1

Executive Summary

TreatmentTreatmentTreatmentTreatmentTreatmentWetlandWetlandWetlandWetlandWetlandHabitat andHabitat andHabitat andHabitat andHabitat andWildlife UseWildlife UseWildlife UseWildlife UseWildlife UseAssessmentAssessmentAssessmentAssessmentAssessment

BackgroundNatural and constructed wetlands are beingused throughout North America and theworld to improve the quality of a broadvariety of wastewater types. Incidental tothis water quality function, most of thesewetlands have been observed to attractsignificant wildlife populations. In somecases these treatment wetlands are also opento the public for nature study and otherforms of recreation.

Little effort has been made to collect ororganize published and unpublished infor-mation concerning the habitat functions oftreatment wetlands. As a result many treat-ment wetland systems have been designedin a manner giving little attention to achiev-ing plant diversity and attracting wildlife.Little in the way of guidance has beenissued on whether such habitat creation iseven compatible with the goal of protectingwetland biota. While it is generally con-ceded that treatment wetlands providehabitat for wildlife, the amount and qualityof that habitat has not been widely recorded.Moreover, the potential for this habitat tothreaten the health of wildlife attracted to

The Tres Rios Hayfield Siteconstructed wetland demon-strates the creation of wildlifehabitat using highly treatedmunicipal effluent along the SaltRiver west of Phoenix, Arizona

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treatment wetlands has been raised, butdocumentation of the occurrence of undesir-able side effects has been very limited.There are few definitive studies of habitatvalues or of ecological impacts in treatmentwetlands�and when they do exist, they arenot generally available.

This Executive Summary report is oneoutput from a Environmental ProtectionAgency Environmental Technology Initia-tive (ETI) Program funded project under-taken in cooperation with the City of Phoe-nix and the U.S. Bureau of Reclamation.This project is concerned with developinginformation and guidance to facilitatetreatment wetland projects that providemultiple environmental benefits. Thepotential benefits of treatment wetlandsinclude improved water quality, creation ofwildlife habitat, and enhancement of thepublic�s understanding and appreciation ofconstructed wetlands. Other efforts underthe ETI project deal with the ability oftreatment wetlands to improve water qualityand with policy and permitting consider-ations facing the technology. This ExecutiveSummary and the companion report: Treat-ment Wetland Habitat and Wildlife UseAssessment, summarize what is knownabout these systems in terms of their eco-

logical structure and function and how theyare used by the public. This portion of theeffort is termed the ETI Treatment WetlandHabitat Project.

Scope of ThisAssessmentNatural and constructed wetlands havereceived and treated a variety of wastewatersources for over 25 years. Hundreds oftreatment wetlands exist in the UnitedStates (Bastian and Hammer, 1993; USEPA, 1993; Kadlec and Knight, 1996) andin Europe and Canada (Pries, 1994). Newsystems are being designed and imple-mented at an ever-increasing rate. Thisinnovative technology for managing waterquality has become attractive to public andprivate facilities, in many cases because itprovides a cost-effective method for im-proving water quality while providingvaluable wetland habitat.

Concurrent with the development andmaturation of treatment wetland technology,researchers have observed that numeroussecondary or ancillary benefits have resultedfrom some of these projects (Sather, 1989;Knight, 1992; Knight, 1997). Publishedobservations of high usage by waterfowland other wetland-dependent wildlife insurface flow treatment wetlands (Wilhelm etal., 1989) indicated that these secondarybenefits are highly significant in somecases. Also, researchers have pointed outpotential problems that might result fromthe use of wetlands for receiving wastewa-ters (Guntenspergen and Stearns, 1985;Bastian et al., 1989; Knight, 1992; Godfreyet al., 1985; Wren et al., 1997).Bioaccumulation of heavy metals or organ-ics that are present in some wastewaters, aswell as transmission of disease, might createhazards that outweigh the potential benefitsof these projects.

Habitat diversity can be incorporated in constructed wetlands byplanting a variety of aquatic plant species such as these water lilies.

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The U.S. EPA conducted a pilot study ofwildlife usage and habitat functions ofconstructed treatment wetlands during thesummer of 1992. This study utilized aconsistent rapid-assessment protocol at sixconstructed surface flow treatment wetlandsto evaluate their habitat structure andfunction and the possibility of environmen-tal hazards (McAllister 1992, 1993a,1993b). That study represents the onlyknown attempt to critically compare habitatand wildlife usage between treatmentwetland sites with nearby �control� naturalwetlands.

A recent report prepared by the CanadianWildlife Service (Wren et al., 1997) summa-rizes information on wildlife usage ofstormwater treatment wetlands. It identifiesareas of potential concern related to accu-mulation of hazardous pollutants andconcludes that insufficient data are availableto document detrimental effects. The reportrecommends the need to require detailedmonitoring of potential wildlife hazards instormwater treatment wetlands in Canada.

This ETI project effort represents the firstcomprehensive effort to assemble the wide-ranging information concerning the habitatand wildlife use data from surface flowtreatment wetlands. These data are as-sembled in an electronic data base formatthat allows researchers to take a critical lookat the actual benefits and hazards that havebeen documented in treatment wetlands.This project involved a focused search ofproject reports and researcher files forqualitative and quantitative informationconcerning surface flow treatment wetlandplant communities, animal populations,concentrations of trace metals and organics,biomonitoring results, and human use.These data have been gathered into anelectronic format built upon the previousexisting North American Treatment WetlandDatabase Version 1.0 (NADB v. 1.0) fundedby the U.S. EPA (Knight et al., 1993). This

Executive Summary briefly describes theformat and contents of the updated database(NADB v. 2.0) and synthesizes this existinginformation into a summary of currentknowledge and remaining questions relatedto habitat and wildlife use of treatmentwetlands.

Habitat quality, wildlife population, andhuman usage data have been previouslycollected by a number of treatment wetlandprojects. When available, these data aretypically in raw form, unpublished reports,or rarely in refereed publications. In manycases these data have not been available toother researchers to evaluate. No previousattempt has been made to assemble thesetypes of data into a consistent format or tosummarize information to compare resultsamong treatment wetland sites.

The primary purpose of this effort was toassemble existing wildlife and habitat usedata from diverse sources into a consistentformat and to make these data available to

Gated pipes onraised boardwalksallow access to over600 acres oftreatment area inthe Vereen NaturalTreatment Wetlandin South Carolina.

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regulators, designers, owners, and research-ers. This Executive Summary and thecompanion report provide a preliminarysummary of these data to begin identifyingany apparent benefits or hazards. It isanticipated that others will conduct moredetailed analyses of these data.

A second purpose of this effort is to estab-lish an inventory of the types of data that areof interest when assessing the environmen-tal and societal attributes of treatmentwetlands, and to create a database format toguide the design of new studies as addi-tional data are collected by wetland re-searchers. A third purpose of the effort is toprovide information concerning habitat,wildlife, and human use in treatment wet-lands to be used for future designs of thesesystems to optimize specific goals forhabitat creation. The fourth purpose of thisproject is to identify areas of insufficientknowledge and to recommend actions thatcan be taken to fill those information gaps.

North AmericanTreatment WetlandDatabase Version 2.0(NADB v. 2.0)Data CollectionThe original NADB v. 1.0 identified 179sites where treatment wetlands were beingused in North America (Knight et al., 1993).In the course of that effort, habitat andwildlife usage data sets were obtained fromsome of these sites. Ongoing treatmentwetland monitoring projects continue todevelop habitat-related data, and those datawere requested by telephone and or inwriting from current project owners andresearchers. Data were received in variousformats, including electronic spreadsheets,consultant and owner reports, daily monitor-ing reports, and raw data. Data were col-lected using a variety of methods with no

differing levels of quality control/qualityassurance between projects. Although thiseffort to obtain existing treatment wetlandhabitat data was extensive, it is consideredlikely that some relevant data sets are notincluded in this survey.

There was no attempt to verify or judge thequality of data collected for this database.Any use of these data to develop summaryconclusions concerning the populations offlora and fauna in treatment wetlandsshould be considered preliminary untilspecific data sets are identified and theirquality verified through peer-reviewedreports. The data gathered for the compan-ion report range in quality from detailedbiological and water quality research effortsto cursory qualitative estimates. For mostpurposes, the data summarized in theNADB v. 2.0 can be assumed to be reason-able estimates or approximations of thebiological and chemical conditions in thesetreatment wetlands.

Database StructureFive new database files with data pertinentto habitat quality and wildlife use of treat-ment wetlands were added to the existing 7files in NADB v. 1.0 to create the ETITreatment Wetland Habitat Project NADBv. 2.0. The structure of the five new data-base files follows the format of NADB v.1.0 in their hierarchical structure. TheNADB v. 2.0 also has been updated byadding treatment wetland site, design, andoperational performance data from confinedanimal feeding operations (CAFOs) summa-rized by a separate project completed for theGulf of Mexico Program with U.S. EPAfunding (CH2M HILL and Payne Engineer-ing, 1997).

Each record identifies the treatment wetlandsite, system, and cell, which allows links tobe made between the 12 individual databasefiles in NADB v. 2.0.

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The Vegetation database file containsqualitative and quantitative plant commu-nity data for treatment wetland sites. Itprovides vegetation data of cells withineach system for a specified period. Dataentered here include species lists, percentcover, biomass, density, basal area, andimportance values.

The Wildlife database file contains qualita-tive and quantitative population data forbenthic macroinvertebrates (benthos), fish,amphibians, reptiles, avifauna (birds), andmammals. Data entered here include specieslists, species density, species diversity, andreproductive success for a given period.

The Metals/Organics database file containsdata on water, sediment, plant, and wildlifetissue concentrations for trace metals andorganics. Data entered into this file areidentified by the sample matrix type (water,sediment, or tissue) and the sample param-eter. Water sampling data are recorded asinfluent and effluent concentrations for eachsystem at a given site. Sediment data areidentified by the station location. Plant andwildlife tissue data are identified by speciesand the type of tissue.

The Biomonitoring database file includesinformation on acute and chronic toxicitytests, reproduction, and mortality tests onvarious test organisms. Each record identifiesthe sampling location (influent or effluent),dilution for each test, and the organism used.

The Human Use database file containsinformation on how the public uses wetlandtreatment sites for recreation, research,hunting, and other activities. Data enteredinclude use density, number of use days, andharvest totals per site.

Summary of NADB v. 2.0ContentsSites and Systems

NADB v. 2.0 has information for a total of257 sites, 367 systems, and 831 cells fromtreatment wetlands in North America. Thesenumbers reflect the fact that some sites havemultiple systems and some individual sys-tems have multiple cells. Of these 257 sites,160 of them treat municipal wastewater, 12receive industrial effluents, 68 receivelivestock wastewaters, and 17 receive otherwastewater types including stormwaters. Ofthe systems described in NADB v. 2.0, 305

File structure of the North American Treatment Wetland System Database (NADB) Version 2.0.

Site

CellPermits

SystemPeople Literature

OperationalData

Vegetation Wildlife Metals/Organics Biomonitoring Human

Use

Legend

Site

System

Cell

NADB Version 1.0

ETI Habitat Database

ETI U.S. EPAEnvironmentalTechnologyInitative

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are surface flow, 54 are subsurface flow, and8 are hybrids of these two designs.

The five new files in NADB v. 2.0 containhabitat and related data for 109 sites,168 separate systems, and 386 individualcells from 31 states or provinces. Eighty-five percent of the sites within the five newdatabase files are constructed treatmentwetlands; the rest are natural treatmentwetlands. Of the 29,960 new records inthese five database files, 65 percent comefrom constructed treatment wetland sites.

Treatment Wetlandsas HabitatThe word habitat refers to a place or envi-ronment that provides support for the needsof a plant or animal. Many plant species aretypically found in wetland environments,including vascular plants, algae, mosses,ferns, and other non-vascular plant species.Wetlands also provide some or all of thehabitat requirements for thousands ofanimal species. Some animals may live outtheir lives within the border of a particularwetland while other species are adapted tocome and go across wetland boundaries.Wetlands provide significant habitat re-quirements for many of the bird species thatare commonly found in North America.

For an environment to be classified ashabitat for a particular organism, it must beable to provide the necessary conditionsrequired to complete the normal life cycle ofthat organism and to propagate the speciesinto the indefinite future. There must be theopportunity for reproduction, growth,adaptation, maturation, and ultimatelyreproduction again.

Since the habitat requirements of nearlyevery organism are different in some way,there is no single measure of the adequacyof habitat that can be applied broadly across

many species. However, there is a relativelysimple test to determine if a given area isproviding suitable habitat for a species ofinterest. The presence of the species over aperiod of time that includes multiple gen-erations indicates that the area is suitablehabitat. For plant populations, this testrequires that successful reproduction mustoccur within the plant�s normal life span.This might be only once in 100 years forlong-lived tree species, or it may be yearlyfor annual species.

This habitat test applies to organisms thatbreed within the habitat as well as those thatmay migrate through and breed elsewhere.If these migratory animals or their progenydo not return to the area then it is not pro-viding suitable habitat. To be beneficial,habitat must provide one or more lifehistory requirements that contribute to aspecies� sustainable population size. If theamount or quality of available habitat islimiting a given species� overall populationsize, then the addition of more habitat or theenhancement of existing habitat will lead toa higher sustainable population of thatorganism. While science may never haveenough information to define a species�overall population size and the variablenature of that population from year to year,enough data exist for some key species thatoccur in treatment wetlands to make pre-liminary assessments of the habitat value ofthese engineered ecosystems. Existingknowledge can be organized by taxonomicgroup (vegetation and animals) and byspecific attention to potential hazards tobiota and humans.

Vegetation in TreatmentWetlandsIntroduction

The wetland environment is generallycharacterized by a high diversity and abun-dance of plants (Mitsch and Gosselink,

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Source of Source of

Site No. Site Name Origin Area (ha) Waste Water Site No. Site Name Origin Area (ha) Waste Water

1 Lakeland, FL CON 498.00 MUN 511 Wayne White Farm, NS CON 0.43 AGR

5 Orange County, FL CON 89.00 MUN 512 David Thompson Farm, NS CON 0.10 AGR

7 Cypress Domes, FL NAT 1.56 MUN 513 Ken Hunter Farm, NS CON 0.07 AGR

9 Reedy Creek, FL NAT 82.20 MUN 514 Oregon State University, OR CON 0.53 AGR

11 Silver Springs Shores, FL CON 21.00 MUN 515 Hickok Veal, PA CON 0.14 AGR

12 Central, SC NAT 31.60 MUN 516 Cobb Farm, PA CON 0.01 AGR

13 Ironbridge, FL NAT 494.00 MUN 517 Moyer Farm, PA CON 0.01 AGR

18 West Jackson County, MS CON 22.70 MUN 518 Crum Farm, MD CON 0.11 AGR

20 Poinciana, FL NAT 46.60 MUN 519 3M Farm, MD CON 0.12 AGR

22 Vereen, SC NAT 229.00 MUN 520 Delmarva Farms , MD CON 0.73 AGR

25 Arcata, CA CON 15.18 MUN 521 U of Connecticut, CT CON 0.04 AGR

26 Hillsboro, OR CON 35.70 IND 522 Guy Thompson Farm, PEI CON 0.15 AGR

29 Santa Rosa, CA CON 4.05 MUN 523 David Gerrits Farm, WI CON 0.03 AGR

31 Waldo, FL NAT 2.60 MUN 524 Norwood Farms, IN CON 0.11 AGR

33 Deer Park, FL NAT 50.60 MUN 526 Nowicki Farm, ALB CON 0.05 AGR

39 Brookhaven, NY CON 0.49 MUN 527 Mercer Co., KY CON 0.14 AGR

51 Hayward, CA CON 58.68 MUN 528 Piscataquis River, ME CON 0.04 AGR

62 Minot, ND CON 13.58 MUN 529 Tom Brothers Farm, IN CON 0.19 AGR

68 Halsey (Pope & Talbot), OR CON 2.02 IND 530 Purdue University, IN CON 0.03 AGR

76 Show Low, AZ CON 54.20 MUN 531 Adair Co.#1, KY CON 0.03 AGR

91 Hillsboro, ND CON 33.00 IND 532 Adair Co.#2, KY CON 0.04 AGR

92 Everglades Nutr. Removal, FL CON 1406.00 OTH 533 Casey Co.#1, KY CON 0.06 AGR

96 Columbia, MO CON 37.00 MUN 536 Crittenden Co., KY CON 0.07 AGR

98 Hemet/San Jacinto, CA CON 14.16 MUN 537 Wayne Co.#1, KY CON 0.03 AGR

99 Sacramento Dem. Wetland, CA CON 8.90 MUN 538 Wayne Co.#2, KY CON 0.02 AGR

102 Champion Pilot, FL CON 1.42 IND 539 Spencer Co., KY CON 0.04 AGR

108 Las Gallinas San. Dist., CA CON � MUN 542 Allen Co., KY CON 3.70 AGR

109 Collins, MS CON 4.47 MUN 543 Butler Co.#1, KY CON 4.90 AGR

110 Tompkins County Landfill, NY CON 0.04 IND 544 Hopkins Co., KY CON 0.93 AGR

111 TVA Mussel Shoals, AL CON 0.19 IND 545 McLean Co.#1, KY CON 0.65 AGR

112 Tres Rios, AZ CON 4.18 MUN 546 McLean Co.#2, KY CON 0.28 AGR

114 Tarrant Co, TX CON � OTH 547 McLean Co.#3, KY CON 0.12 AGR

202 Biwabik, MN NAT 40.50 MUN 548 Union Co., KY CON 0.12 AGR

204 Cannon Beach, OR NAT 7.00 MUN 549 Butler Co.#2, KY CON 4.80 AGR

206 Des Plaines, IL CON 10.13 OTH 550 Dogwood Ridge, KY CON 3.80 AGR

209 Houghton Lake, MI NAT 79.00 MUN 600 Hernando, MS CON 0.08 AGR

210 Kinross (Kincheloe), MI NAT 110.00 MUN 601 Pontotoc, MS CON 0.32 AGR

217 Vermontville, MI CON 4.60 MUN 602 Newton, MS CON 0.12 AGR

302 Benton, KY CON 3.00 MUN 603 Hattiesburg, MS CON 1.24 AGR

303 Brillion, WI NAT 156.00 MUN 605 Auburn Poultry, AL CON 0.12 AGR

304 Drummond, WI NAT 6.00 MUN 606 Auburn Swine, AL CON 0.00 AGR

310 Incline Village, NV CON 173.28 MUN 607 McMichael Dairy, GA CON 0.29 AGR

311 Listowel Artificial Marsh, ONT CON 0.87 MUN 608 Tifton, GA CON 0.22 AGR

312 Mt.View Sanitary District, CA CON 37.00 MUN 610 Louis. St. Univ., LA CON 0.81 AGR

314 Seneca Army Depot, NY NAT 2.50 MUN 611 New Mexico State, NM CON 0.00 AGR

412 Benton, KY CON 1.46 MUN 612 Duplin, NC CON 0.07 AGR

500 Saint-Felicien, QUE CON 0.72 MUN 613 Key Dairy, GA CON 0.35 AGR

501 Essex County, ONT CON 0.06 AGR 615 Crittenden Co., KY CON 0.34 AGR

502 Perth County, ONT CON 0.09 AGR 616 Union Co., KY CON 0.10 AGR

503 Simco County #1, ONT CON � AGR 617 La Franchi, CA CON 0.10 AGR

504 Region of Niagara, ONT CON 0.02 AGR

505 Hamilton-Wentworth, ONT CON � AGR

506 Region of Ottawa-Carlton, ONT CON 0.02 AGR

507 Russel County, ONT CON 0.08 AGR

508 Region of Peel, ONT CON � AGR

509 Simco County #2, ONT CON 0.03 AGR

510 Lucky Rose Farm, IN CON 0.98 AGR

Origin:

CON Constructed

NAT Natural

HYB Hybrid

1 hectare (ha) = 2.47 acres

Source of Waste Water:

AGR Agricultural

IND Industrial

MUN Municipal

OTH Other

Treatment Wetland Sites in the NADB Version 2.0 with Habitat Data.

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1993). In many cases, wetland plant commu-nities include multiple vertical strata rangingfrom groundcover species to shrubs and sub-canopy trees to canopy tree species. Obligatewetland plant species are defined as thosefound exclusively in wetland habitats, whilefacultative species are those that may befound in upland or wetland areas. The U.S.Fish and Wildlife Service (USFWS) haslisted more than 6,700 species of obligateand facultative wetland plant species in theUnited States (Reed, 1988).

Wetland plant diversity is important indetermining wildlife diversity because of thecreation of niches associated with differingvegetative structure, reproduction strategies,flowering and seeding phenologies, grossproductivity, and rates of decomposition.In addition to their diversity of species andgrowth habitats, wetland plants are impor-tant for treatment wetland pollutant removalperformance because the physical and

chemical structure they provide supportsmicrobial populations.

The ecology of wetland plant communitiescan be assessed through the use of qualitativeand quantitative measures. Lists of plantspecies provide an overall qualitative inven-tory of the diversity that is present and theability of a wetland plant community to adaptto fluctuating environmental conditions.Quantitative measures of dominance (massor cover per unit area), density (number ofindividuals per unit area), and frequency(percent occurrence in a number of differentsamples) of plants species are direct indica-tors of ecological structure and can be com-pared between treatment wetlands andcontrol sites to assess differences. Quantita-tive functional measures of wetland plantpopulations include primary productivity(gross and various measures of net produc-tivity), litterfall, and decomposition. Thesemeasures provide a method to compare thefunctions of constructed and natural treat-ment wetlands and to compare treatmentwetlands with control wetlands that are notreceiving treated effluents.

Plant Communities

Constructed treatment wetlands are typicallydominated by emergent marsh, floatingaquatic plant, or submerged aquatic plantcommunities. In some cases these con-structed treatment wetlands are dominated bypopulations of filamentous algae becausemarsh plant species have had difficultybecoming established. Emergent marshspecies are frequently intermingled and co-dominant with populations of small floatingaquatic plants such as duckweed (Lemnaspp.). Many constructed treatment marshes inthe United States are dominated by cattails(Typha spp.) or bulrush (Scirpus spp.);however, some treatment marshes are domi-nated by other plant species or by a complexadmixture of species that includes cattailsand bulrush.

Cattails continue to be the workhorse of manytreatment wetlands.

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Natural wetlands used for water qualitytreatment may be dominated by emergentmarsh plant species, by tree species, or byshrub species. Dominant species in naturalwetlands used for water quality treatmentvary regionally, depending upon the types ofwetlands that are locally available. In thesoutheastern United States, the dominantforested wetland types that have been usedto receive and polish wastewaters includecypress (Taxodium spp.), gum (Nyssa spp.),bay (Gordonia lasianthus, Magnolia virginiana, and/or Persea spp.), red maple(Acer rubrum), titi (Cyrilla racemiflora andCliftonia monophylla), willows (Salix spp.),ash (Fraxinus spp.), and oaks (Quercusspp.). In the northcentral United States,forested wetlands receiving wastewaters aredominated by spruce (Picea  spp.), willow,and birch (Betula spp.). In the northwesternUnited States, natural shrub forested wet-lands that receive treated wastewaters aredominated by alder (Alnus rubra) and sitkaspruce (Picea sitchensis).

In the upper midwest and northeasternUnited States, natural marshes dominatedby cattails, grasses, and sedges have re-ceived a variety of wastewater discharges.

Many constructed and natural treatmentwetlands undergo plant succession duringtheir operational life. Constructed marshes

tend to remain marshes as long as floodingis nearly continuous and water depthsexceed about 5 centimeters (cm). At shal-lower water depths and under conditionsthat allow germination of woody species(such as at Orange County, Florida, Site No.5), plant succession moves from herbaceousmarsh plant species through shrubs andsmall trees, to a forested wetland.Natural treatment systems may undergosuccession also. Observed succession in theimmediate vicinity of the distribution area atthe Bear Bay wetland near Myrtle Beach(Vereen, Site No. 22), South Carolina, andin forested wetlands in north central Michi-gan (Bellaire, Site No. 201 and Kinross,Site No. 210) was from densely forested toopen forest shrub/marsh. The water regimeand nutrient quality conditions at thesewetlands killed sensitive tree species andpromoted growth of herbaceous and woodyground cover and shrubs. Other forestednatural treatment wetlands have beenobserved to continue their normal matura-tion pattern as indicated by incresing treebasal area over time.

Plant Species Diversity

Of the more than 800 species of macro-phytic plants that have been reported innatural and constructed treatment wetlands,693 species are emergent herbaceous mac-rophytes, 36 are floating aquatic species, 12

Increasing dominance by cattails(Typha latifolia) at the Kinross,Michigan, natural wetland. Theoriginal plant dominants were bogbirch (Betula pumila), sedge (Carexflava), and black spruce (Piceamariana). Approximately 1/3 of theentire wetland area (320 ha) wasaltered by this unplanned treatmentproject. Water depth changesresulting from beaver activity wereimplicated in addition to nutrientinputs as an important causativefactor for this shift in plant domi-nance (modified from Kadlec andBevis, 1990).

110

100

90

80

70

60

50

40

30

20

10

01950 1955 1960 1965 1970 1975 1980 1985 1990

Year

Are

a o

f C

atta

il M

on

ocu

ltu

re (

hec

tare

s) Lake/Freeway Barrier Reached

10

Biological criteria in the Vereen Natural Treatment Wetland near Myrtle Beach, SC (Site No. 222) include allowablechanges for canopy density and dominance, subcanopy and shrub percent cover, and total plant species diversity.While decreases have been observed for one of these criteria (subcanopy and shrub percent cover) the other threecriteria have all increased in response to 10 years of treated municipal effluent discharge. Far from becoming amonoculture, the floristic diversity of this wetland has increased by 14 species and overall canopy dominance hasincreased by 250 percent.

120110100

908070605040302010

01986 1988 1990 1992 1994 1996Baseline

Sub

cano

py a

nd S

hrub

(per

cent

cov

er)

110

100

90

80

70

60

50

40

30

20

10

01986 1988 1990 1992 1994 1996Baseline

Tota

l Pla

nt S

peci

es

900

800

700

600

500

400

300

200

100

0 1986 1988 1990 1992 1994 1996Baseline

Can

opy

Den

sity

10

9

8

7

6

5

4

3

2

1

0 1986 1988 1990 1992 1994 1996Baseline

Can

opy

Dom

inan

ce(m

2 /ha

)

30% Decline50% Decline

are submerged aquatics, 57 are shrubs, 55are trees, and 18 are vines. A total of 593macrophytic plant species has been reportedfrom constructed treatment wetlands, and427 species from natural treatment wet-lands. Emergent herbaceous macrophytesaccount for 501 species in constructedtreatment wetlands and 290 species innatural treatment wetlands. A significantvariety of tree and shrub species occur insome constructed wetlands. Tree and shrubspecies are well represented in naturaltreatment wetlands with 88 different speciesrecorded.

Plant Dominance, Density, andFrequency

Emergent herbaceous plant communitiescan be quantitatively sampled by use ofline-intercept transects or quadrats. Theseplant ecology techniques provide measuresof plant cover by species, plant frequency,and in some cases plant density, height, orbiomass. Plant communities in forestedwetlands are often quantified throughmeasurements of dominance, density, andfrequency. These three quantitative mea-sures can be used to calculate importancevalue, a relative measure of the contributionof individual tree species in a forest.

Quantitative data from treatment wetlandsconfirm the common observation that thesesystems are densely vegetated. Plant biom-ass values are at the high end of recordedvalues in non-treatment wetlands. This isthe case in both constructed and naturaltreatment wetlands. Reductions in treedominance have been observed in a numberof natural treatment wetlands while othersshow no detrimental effect. Effects onwetland trees are species-specific. Some

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tree species are adapted to the longhydroperiods and low sediment oxygenlevels typical of treatment wetlands whileother species cannot survive these changes.An understanding of the tolerance limits ofindividual plant species, careful site selec-tion and project design can maintain hightree dominance in natural treatment wet-lands.

Primary Productivity

Biomass estimates in marsh wetlandsprovide an index of net plant productivityon a seasonal basis. The biomass estimatesin the NADB v. 2.0 indicate that treatmentwetland marshes have high net productioncompared with many non-treatmentmarshes.

No direct estimates of net primary produc-tivity were recorded in NADB v. 2.0. How-ever, the database includes litterfall ratesfrom two natural forested wetlands (OrangeCounty, Florida, Site No. 5, and Bear Bay,South Carolina, Site No. 22). Litterfall maybe used as a measure of net primary produc-tion (Mitsch and Gosselink, 1993). Thelitterfall rates summarized from treatmentwetlands are comparable to values fromnatural forested wetlands and adjacentnatural control wetlands.

Plant Decomposition

Litter decomposition rates measure animportant component of carbon and nutrientrecycling in wetlands. The decompositionrates of individual plant species differgreatly because of their variable cell struc-ture and lignin composition. Litter decom-position rates are available in NADB v. 2.0from two treatment wetlands, Bear Bay inSouth Carolina (Site No. 22), and theOrange County Eastern Service Area inFlorida. At both sites the presence of shal-

3500

3000

2500

2000

1500

1000

500

076 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94

Year

Ab

ove

gro

un

d B

iom

ass

(gm

/m2) Discharge Area at Pipeline

Backgradient Control Area

Plant biomass changes in responseto addition of treated municipaleffluent at Houghton LakePeatland. Control area experienceshydrologic changes withoutnutrient increases. Pre-existingpeatland vegetation was largelyreplaced by cattails and duckweeddominants over about one-tenth ofthe 600 ha area (modified fromKadlec, 1993).

Orange Co., FLEastern Service

Area

Lit

terf

all (

Dry

Wei

gh

t, g

/m2 /

yr)

Bear Bay,SC

Average of20 S.E.

DeepwaterSwamps

Average of 5FloodplainForestedWetlands

600

500

400

300

200

100

0

Treatment Wetlands Unaltered Wetlands

Litterfall rates provide an estimate of net primary productivityin wetlands dominated by woody vegetation. Rates in naturaltreatment wetlands are comparable to unaltered naturalwetlands.

12

low flooding caused by the discharge oftreated effluent increased the decompositionrate of leaves.

Summary and Data Requirements

Treatment wetlands are typically dominatedby dense growths of wetland-dependentplant species. These plant communities aresimilar in ecological structure and functionto natural wetland plant communities.

A variety of plant communities occur intreatment wetlands including marshes,shrub swamps, and forested swamps. Whilemost constructed treatment wetlands aremarshes, a few constructed treatmentsystems are developing shrub and swampcharacteristics over time, either intention-ally or through volunteer plant colonizationand succession.

On the other hand, natural forested wetlandsreceiving secondary treated municipalwastewaters have been partially convertedto marshes in several areas of the UnitedStates. Other forested wetlands receivinghigher quality municipal wastewaters(advanced secondary with nitrification ortertiary with phosphorus removal) havemaintained their canopy dominance oversignificant periods of time.

More long-term, ecosystem-level studies areneeded for both constructed and naturaltreatment wetlands under a variety ofgeographical and pollutant loading condi-tions to fully describe the parameters mostpredictive of plant community developmentin treatment wetlands. Also, more studies ofthe basic quantitative ecology of naturalwetlands would be helpful for comparisonto treatment wetland structure and function.

Wetland plant diversity is a poorly under-stood subject, both in unaffected naturalwetlands and in treatment wetlands. Non-treatment natural wetlands are frequentlydominated by only a few plant species (forexample, cypress swamps, cattail, sedge, orsawgrass marshes, etc.) that are best adaptedto stressful environmental conditions suchas low nutrient levels, low soil oxygenlevels, or fluctuating water levels. Otherunaffected natural wetlands have higherplant diversity and greater evenness be-tween multiple dominant plant species.

Both constructed and natural treatmentwetlands cover the same range of plantdominance and diversity of unaffectednatural wetlands. Information collected forNADB v. 2.0 indicates that hundreds ofplant species occur in a variety of treatmentwetlands. Even when treatment wetlandsare dominated by cattails or bulrush, dozensof other herbaceous and woody plant spe-cies are typically present.

Volunteer plants such as these mud-plantain fre-quently invade constructed treatment wetlands,adding habitat diversity for wildlife and greaterresistance against insect infestations in cattail-dominated marshes.

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Data from natural treatment wetlandsindicate variable responses to treated efflu-ent discharges: existing diversity may bereduced by the presence of a wastewaterdischarge (e.g., Houghton Lake, Site No.209, and Kinross, Site No. 210, Michigan),or diversity may be maintained or increasedfollowing the initiation of a discharge toother wetlands (Orange County and ReedyCreek, Florida and Bear Bay, South Caro-lina).

The effect of treated wastewater dischargeson plant diversity in natural wetlandsdepends on the amount of pre-treatment andthe scale of the project. Municipal effluentstreated to advanced standards generallyhave only a water regime effect while thosetreated to secondary standards may alsohave a water quality effect. Water qualityeffects on plant diversity are greatest nearthe point of inflow, while water regimeeffects may occur over the entire area of anatural treatment wetland. Over the scale ofthe entire wetland, plant diversity may beincreased by the addition of new plantspecies associated with the discharge.

Total plant cover and dominance data do notindicate any observable difference betweentreatment and non-treatment wetlands forthese indices. However, biomass dataindicate that discharge of secondary munici-pal wastewater to natural, low-nutrientwetlands will greatly increase plant biom-ass. This enrichment effect is typical ofwetlands receiving treated municipal dis-charges and is most observable in theimmediate area of the discharge.

Very few data have been collected thatmeasure the ecological function of treat-ment wetland plant communities. Highplant growth rates are apparent based onstanding crop; however, clip plots, gasmetabolism studies, litterfall studies, orother methods for estimating net primaryproduction have been conducted at only a

few locations. Litterfall rates in at least twonatural forested treatment wetlands arecomparable to unaffected natural forestedwetlands.

Other ecological functions related to thecarbon cycle through wetland plants havebeen largely ignored in treatment wetlandstudies. Decomposition rates in treatmentwetlands compared with natural wetlandsappear to be higher because of greaterorganic carbon inputs and the continuouspresence of water. The proportion of thisorganic carbon cycling through the wetlandplants may be very different between treat-ment and non-treatment wetlands, and thequantities and forms of carbon being ex-ported across the system�s boundaries arelikely to be different. More comprehensivestudies of the total carbon cycle in treatmentwetlands would help quantify the relativeimportance of these similarities and differ-ences.

Wildlife in TreatmentWetlandsIntroduction

Numerous wildlife species of all taxonomicorders depend on wetlands as habitat. Plantproductivity and imports of organic carbonfrom surrounding ecosystems provide theenergy basis that supports these wildlifepopulations. Many wetlands have both

Dragonflies are a common predator found at both con-structed and natural treatment wetlands.

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aquatic and terrestrial food chains. Planttissues that fall into the aquatic portion ofthe wetland are typically degraded by acomplex assemblage of microscopic andsmall aquatic organisms that includesinvertebrate animal groups (protozoans,worms, molluscs, arthropods, and others).These organisms, in turn, serve as the basisof the food chain for other invertebrates,and for diverse vertebrate groups such asfish, amphibians, reptiles, birds, and mam-mals. In addition to their direct support ofwildlife food chains, wetlands providediverse structure for other wildlife habitatneeds.

Over 1,400 species of wildlife have beenreported for constructed and natural treat-ment wetlands in the NADB v. 2.0. Theseinclude more than 700 species of inverte-brates, 78 species of fish, 21 species ofamphibians, 31 species of reptiles, 412 spe-cies of birds, and 40 species of mammals.Over 800 animal species have been reportedin constructed treatment wetlands alone.

Because species lists have been determinedfor only a small fraction of the treatmentwetland sites listed in NADB v. 2.0, andbecause of the widely disparate methods andseasons of measurement, these species totalsunderestimate the diversity that exists intreatment wetlands in North America. Thesections that follow describe findings foreach wildlife group individually.

Invertebrates

A total of 709 species of aquatic inverte-brates have been recorded from treatmentwetlands in NADB v. 2.0. These include15 species of aschelminthes, 81 species ofcrustaceans, 12 species of arachnids, 29 spe-cies of molluscs, and 589 species of insects.Twenty-three treatment wetland systemslisted in NADB v. 2.0 have invertebrate data.In most cases, only species lists are avail-able. A few systems reported quantitativedata, although sampling techniques varied.Although a total of 342 species of benthicmacroinvertebrates have been reported forconstructed treatment wetland sites, theaverage diversity (H�) is low at 1.36 units.The average benthic macroinvertebratediversity for natural treatment wetlands is2.29 units with a total of 349 species re-ported for all sites. These low diversities aretypical of unaltered wetland environmentsdue to low ambient dissolved oxygen levelsand fluctuating water availability.

Average benthic populations summarized inthe NADB v. 2.0 are 6,083 individuals persquare meter for constructed treatmentwetlands and 2,102 per square meter fornatural treatment wetlands. Total populationsof mosquito larvae and pupae in treatmentwetlands are reported from a few projects.Average densities are 1,144 individuals percubic meter for constructed treatment wet-lands (pilot wetlands in Hemet, Site No. 98,and Sacramento, Site No. 99, California) and952 per cubic meter in natural treatmentwetlands. The range of values around these

Wetland monitor-ing efforts havecharterized all

biotic communitiesin constructed

treatment wetlands,including

macroinvertebrates.

15

averages is great and may reflect differencesin sampling techniques as much as differ-ences between actual wetland mosquitopopulations.

No functional measures for invertebratepopulations were discovered from treatmentwetland studies. Secondary production ofinvertebrates can be evaluated by usingrepeated population estimates through time.General anecdotal observations from newlyconstructed treatment wetlands indicate thatinvertebrate populations develop quicklywhen treated wastewaters are added and thatthese population trends are highly variablewhen vegetative cover changes during thefirst few seasons of wetland maturation.Long-term populations of invertebratesappear to be more stable and more charac-teristic of natural wetland environments.

Fish

Seventy-eight fish species are reported from13 treatment wetland sites in NADB v. 2.0(64 species from constructed treatmentwetlands and 24 species from naturaltreatment wetlands). Mosquitofish (Gambu-sia affinis) were reported from 5 constructedand 4 natural treatment wetlands. Thisspecies, found in 69 percent of the treatmentwetlands where fish were sampled, is oftenintentionally introduced into these treatmentwetlands; other species are apparentlypresent as a result of volunteer colonization.

Amphibians

Twenty-one amphibian species are reportedfrom 6 constructed and 3 natural treatmentwetlands in the NADB v. 2.0. Ten speciesare reported from constructed treatmentwetlands and 14 species from naturaltreatment wetlands. Amphibian speciesoccurrence was recorded at two naturaltreatment wetland sites in South Carolina,but populations were not quantitativelysampled. From 4 to 8 amphibian specieswere observed each year during 7 years of

Snakes such as thiswater moccasin are animportant link in thefood webs of treatmentwetlands.

operation of the Vereen natural treatmentwetland (Site No. 22). From 4 to 7 amphibianspecies were observed over 3 years at CentralSlough (Site No. 12). The likely amphibiandiversity at these two locations is greater thanthese numbers indicate since sampling wasqualitative and conducted over a limitedperiod during the spring of each year. Noquantitative data on amphibian populationsare included in the database.

Reptiles

Thirty-one reptile species are reported from 5constructed and 4 natural treatment wetlandsin NADB v. 2.0. These species includesnakes, alligators, lizards, and turtles. Sevenspecies are reported from constructed treat-ment wetlands and 28 species from naturalsites. The Vereen site in South Carolina (SiteNo. 22) had between 6 and 9 reptile specieswhile Central Slough (Site No. 12) hadbetween 1 and 6 species. As with the amphib-ian data above, reptile diversity at these sitesis likely greater than what is reflected bythese numbers. No quantitative data on reptilepopulations are included in the database.

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Birds

Bird data are reported for 21 constructedtreatment wetland sites and 7 natural treat-ment wetland sites in the NADB v. 2.0. Themajority of these data are species lists andpopulation densities. Very few data onbreeding success, nesting, brood production,and mortality rates were found for thisreview.

A total of 412 bird species are reported fromthese treatment wetlands. Constructedtreatment wetlands are represented by361 bird species and natural treatmentwetlands by 170 bird species. Of the birdspecies listed, 51 are waterfowl, 23 arewading birds, 24 are terns or gulls, 45 areshorebirds, 29 are raptors or scavengers, 7are fowl-like, and 235 are passerine or non-passerine land birds. Approximately 45 per-cent of the total of 412 species reportedfrom treatment wetlands are commonlyconsidered to be wetland-dependent forsome portion of their life history. Thisfinding indicates that a majority of the birdspecies recorded at these treatment wetlandsites are facultative wetland inhabitants.

Bird species counts and population densitiesvary between sites, and even at a singletreatment wetland site on a seasonal basis.

For example, the Hayward marsh (Site No.51)in California recorded population densi-ties ranging from 34 to 280 birds per hectareduring monthly counts. Two demonstration-scale constructed wetlands are being studiedat the Tres Rios, Arizona (Site No. 112),constructed treatment wetland. Bird speciesnumbers by month for the Hayfield andCobble sites reflect this variability, and totalspecies counts for a year are much higherthan for any individual month (61 species atthe Cobble site and 66 species at theHayfield site). These two sites are less than0.5 mile apart and have very similar surfaceareas and plant communities, but are adjacentto different natural riparian systems. Totalbird densities averaged 295 birds per hectareat both sites. These high densities are domi-nated by yellow-headed blackbirds(Xanthocephalus xanthocephalus), withabout 1503 birds per hectare. Bird populationdensities in natural riparian hibitats in thesame area are much lower than the averagebird densities measured at the Tres RiosWetlands.

Bird populations were studied at the DesPlaines, Illinois (Site No. 206), constructedtreatment wetlands before and after projectstartup. A total of 22 species were observedduring the breeding season in 1985 beforeconstruction began, and from 30 to 37 spe-cies were observed during breeding seasoncounts in 1990 and 1991. Spring migrationwaterfowl and wading bird counts were alsomade at this wetland. Number of waterfowlspecies observed during the first 7 weeks ofmigration rose from 3 to 14 (1990) prior toproject start-up and 15 (1991) species withthe project. Total waterfowl and wading birddensities at this site were between 691 and929 birds during the spring migration countsand between 363 and 478 birds during thefall migration counts.

Detailed bird population data were collectedfrom natural treatment wetlands at HoughtonLake, Michigan (Site No. 709), and Vereen,

Number AverageObserved Density

Site Name Species (#/ha)Constructed Wetlands Lakeland, FL 190 6 West Jackson County, MS 61 10 Arcata, CA 159 61 Hayward, CA 134 114 Show Low, AZ 155 14 Collins, MS 35 7 Tres Rios, AZ 78 2958 Incline Village, NV 53 19Natural Wetlands Gainesville, FL 20 23 Vereen, SC 103 19 Biwabik, MN 46 13

Bird diversity and density in treatment wetlands is typicallyhigh.

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South Carolina (Site No. 22). Total numberof bird species recorded at the HoughtonLake site (based on three transects com-bined) were between 34 and 45 from 1978through 1989 and have declined somewhatmore recently. Total number of bird speciesat Vereen varied from 35 to 45 during thefirst 5 years of operation, compared with41 species during the baseline study.

Avian botulism is a paralytic disease of birdscaused by ingesting a toxin produced byClostridium botulinum. Insufficient evidenceis currently available to identify the specificcauses of outbreaks of avian botulism. Avianbotulism is a problem in many wildliferefuges and is known to occur in westernwetlands that receive agricultural returnflows and drain waters. Botulism has alsobeen observed to occur in deep water wet-lands and rivers with high oxygen. Althoughwastewater discharges and treatment wet-lands have been implicated with the propa-gation of this disease (Friend, 1985), specificdocumented case histories are rare.

Avian cholera is a highly infectious diseasecaused by the bacterium Pasteurellamultocida (Friend, 1987). Death can occur inas little as 6 to 12 hours following exposure.Migratory waterfowl concentrated in wet-lands are particularly susceptible to thisinfection, and many other wetland-depen-dent bird species can also be infected withthe disease. Avian cholera has been reportedat one treatment wetland, the HaywardMarsh (Site No. 51) on the east shore of SanFrancisco Bay, south of Oakland, California.Annual episodes of avian cholera have beennoted at this site for the past 6 years. In-fected birds are collected, counted, anddisposed of to reduce spread of the disease.The average number of infected waterfowlcollected during a 6 year period was 127 peryear (15 to 340 birds per year). This wetlandsupports very high waterfowl populationsduring the fall months, with peak numbers

above 30,000 birds per day. Also, aviancholera is encountered in nearly all wetlandsin and around San Francisco Bay. For thesereasons, there appears to be no relationshipbetween the avian cholera observed at thislocation and the source or quality of thewater treated at this system.

A parasite that is known to infect wadingbirds feeding on small fish in Floridawetlands is Eustrongyloides ignotus(Spalding, 1990). Only a few studies of theoccurrence of eustrongylidosis in wetlandwading birds at treatment wetlands havebeen conducted (Frederick and McGehee,1994). The most comprehensive study todate was at the Everglades Nutrient Re-moval project (Site No. 92) in south Florida.Of 12,000 individual fish and 19 speciessampled and analyzed during this study,none were infected with the nematoderesponsible for eustrongylidosis (SFWMD,1997).

Mammals

Forty mammal species are recorded inNADB v. 2.0. A total of 22 species arereported from 6 constructed treatmentwetland sites and 27 species from 4 naturaltreatment wetland sites. Quantitative dataon mammal populations are limited in the

The bird watching blind at the Pintail Marsh in Show Low,Arizona, provides educational opportunities for school children.

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database to small mammal surveys at theconstructed treatment wetland in IronBridge (Site No. 92), Florida (from thedownstream Seminole Ranch wetlands thatreceive the discharge from Iron Bridge) andat the natural treatment marsh in HoughtonLake, Michigan (Site No. 209).

Small mammal densities at Iron Bridgeranged from 2.0 to 37 individuals perhectare with from 1 to 3 species collectedon each sample date. Small mammaldensities at Houghton Lake ranged from140 to 213 individuals per hectare with 2 to7 species per transect in 1979, and 7 to213 individuals per hectare with 1 to 3 spe-cies per transect in 1989. Small mammalmonitoring was conducted on threetransects at Houghton Lake from 1979 until1989. These transects were located at 15 m,250 m, and 500 m downstream of thetreated effluent distribution line. Highersmall mammal densities and diversitieshave generally been obtained closer to thedistribution pipe in an area of leatherleafand bog birch mixed with cattails.

Summary and Data Requirements

Qualitative and quantitative studies ofanimals inhabiting constructed and naturaltreatment wetlands have revealed that theseecosystems provide attractive and produc-tive habitats. All trophic levels are repre-sented, from microscopic invertebrates tomacroinvertebrates, fish, herptiles, birds,and mammals. Numbers of species appearto be generally similar between constructedand natural wetland sites. However, insuffi-cient quantitative faunal data currently existto correlate population diversity or densitywith treatment wetland design criteria suchas pretreatment water quality, mass loadingfor key pollutants and nutrients, waterdepth, vegetation types, etc. Essentially allconclusions concerning relationships be-tween wildlife populations and wetlanddesign must be based on other studies or are

currently anecdotal. This lack of informationemphasizes the need for well-designed,quantitative studies of wildlife populationsconducted in the context of controlledtreatment wetland research projects.

Toxic Metals and TraceOrganics in TreatmentWetlandsIntroduction

A variety of data for metals and trace organiccompounds have been collected from 26wetland treatment wetland sites. Data en-tered into the NADB v. 2.0 were grouped bythe sample matrix: surface water, sediment,or tissue. Tissue samples were further di-vided into vegetation and wildlife groups.Many data records for metal and traceorganic compound concentrations are belowdetection limits (BDL) in the raw data in theNADB v. 2.0.

Metals

Available data for 25 metals and relatedelements measured in surface waters, sedi-ments, and biological tissues from treatmentwetlands are summarized in the NADB v.2.0. These data confirm numerous publishedreports that treatment wetlands reducesurface water concentrations of metals. Theyalso provide a basis for comparing treatmentwetland sediment and tissue metals data topublished criteria that are considered to beprotective of environmental health. Mostcriteria are based on laboratory tests onhighly sensitive species. Comparisons oftreatment wetland trace metal concentrationsto published criteria should be cautious dueto the general lack of research that demon-strates that criteria levels actually createeffects in wetland environments.

Trace Organics

Data for more than 120 trace organic com-pounds are reported for treatment wetland

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surface water, sediments, and tissues. Detect-able levels for some of these trace organicswere found in treatment wetland surfacewaters, sediments, and biological tissues. Atotal of 29 trace organic compounds weredetected (out of 121 analyzed for) in con-structed treatment wetland sediments.

Summary

Wetlands and other aquatic ecosystems canreduce concentrations of metals and traceorganics through their complex array ofphysical, chemical, and biological processes.The efficiency of these pollutant removalprocesses is of interest as treatment wetlandsare being designed for a greater variety ofwastewaters with a wide range of concentra-tions of these trace elements and compounds.On the other hand, sequestration of tracemetals and organics in treatment wetlandscreates a potential for detrimental biologicaleffects due to the chemically stable forms ofthese compounds and their biological toxic-ity. While some trace organics are lost fromthe wetland environment through biologicaldegradation or atmospheric volatilization,other organics and most metals tend toaccumulate in sediments and in biologicaltissues.

An important issue needing to be scruti-nized is the extent to which these potentiallytoxic chemicals bioaccumulate and whetherthey are present in amounts that are toxic tothe biota that normally inhabit these wetlandenvironments. The data summarized in theNADB v. 2.0 provide a basis from which tobegin finding answers to these questions.However, additional data from controlled,realistic-scale treatment wetland researchwill need to be collected and analyzed tofully evaluate treatment performance andthe potential for detrimental effects fromeach metal or organic compound of interest.

Effects of Treatment Wetlandson Whole-Effluent ToxicityIntroduction

The Clean Water Act requires that dis-charges to waters of the United States be�free of toxic substances in toxic amounts.�While it is widely recognized that lowlevels of potentially toxic substances existin nearly all effluents and in most naturalsurface waters, no significant detrimentaleffects from those substances is expectedunless concentrations exceed critical levels.The definitions of those critical levels are

Comparison of treatment trace metal concentrations to chronic ambient water quality criteria. Mean treatmentwetland concentrations are typically close to or less than water quality criteria; however some means and mostmaximum reported values are above chronic criteria.

Chronic Ambient Wetland Effluent Outflow Water Concentration (ug/L)Water Quality Constructed Treatment Natural Treatment Wetlands

Metal Criteria (ug/L)a Mean Max % BDL Mean Max % BDLArsenic 190 5.1 25 14 N.D. N.D. N.D.Cadmium 1.0 h 0.5 5.0 69 1.2 5.0 80Chromium (III) 180 h 4.0 30 41 17 69 50Copper 11h 7.4 90 32 3.0 15 31Lead 2.5 h 5.4 40 51 3.2 15 52Mercury 1.3 0.53 4.9 62 0.24 1.0 86Nickel 160 h 14.1 210 31 9.3 25 72Selenium 5.0 1.4 12 69 N.D. N.D. N.D.Silver 0.56 5.0 75 3.9 15 70Zinc 100h 22 320 35 10 39 42

a U.S. EPA 1986a, 1986b, 1987h = hardness-dependent, assumes 100 mg/l as CaCO3N.D. = not determined

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based on a variety of methods that seek toquantify effects to sensitive groups ofaquatic organisms. When practical, specificwater quality criteria are established by theU.S. EPA to define acceptable maximumlevels for specific toxic chemicals, espe-cially heavy metals and trace organics (U.S.EPA, 1986). Permit criteria reflect thesecritical levels when it is possible to identifyspecific chemicals in an effluent that mayoccur in toxic amounts.

The concept of �whole-effluent� toxicitystandards has been developed to regulatereleases of complex effluents that maycontain from several to dozens of poten-tially toxic chemicals. Standardized toxicitytests have been developed by U.S. EPA todefine the concept of whole-effluent toxicitytesting (U.S. EPA, 1989). The freshwatertest organisms most frequently used are thefathead minnow (Pimephales promelas) andwater flea (Ceriodaphnia dubia). Thesetests look for �acute� or �chronic� toxicity.Acute toxicity is defined as conditions thatlead to the relatively rapid death of the testorganism. Chronic toxicity is a measure ofsublethal effects that ultimately result in adecrease of the organism�s population sizethrough impaired behavior or reproduction.

End points typically vary from 24 to 96hours for acute tests and are typically 7 daysfor chronic tests. Both acute and chronicwhole-effluent toxicity test data are in-cluded in the NADB v. 2.0.

Two primary issues are related to whole-effluent toxicity tests and treatment wet-lands. The first issue is determining howeffective wetlands are as a water qualitytreatment system in reducing concentrationsor bioavailability of toxins and therebyreducing whole-effluent toxicity of a waste-water effluent before it is discharged to areceiving water environment. This issue canbe characterized as the effect of the wetlandon the toxin(s). To examine this first issue,whole-effluent toxicity input/output datacollected from wetlands treating wastewa-ters are summarized in the NADB v. 2.0.

The second issue deals with the potentialeffects of effluent toxicity to organismswithin the treatment wetland. This issue canbe characterized as the effect of the toxin(s)on the wetland. The relevancy of acute andchronic whole-effluent toxicity tests towetland environments has not been exam-ined. These tests are simplistic in that theyfocus all attention on only one or twoanimal species that may or may not havesensitivity to toxins similar to the fauna thatnormally occur in wetlands. Wetland envi-ronments are typically dominated by plantand animal species that are hardier and lesssensitive to pollutants than more sensitivespecies that may occur in other surfacewaters. Quantitative data of direct or indi-rect toxic effects to wildlife in treatmentwetlands are generally lacking.

Acute Toxicity

Acute toxicity test results were availablefrom four treatment wetlands. No signifi-cant mortality was observed at three ofthese sites receiving municipal effluents.One site receiving an industrial effluent did

The Hayfield Site demonstration Wetland at Tres Rios west of Phoenix,Arizona, includes two cells with variable numbers of deep water zones totest their effect on hydraulic efficiency and wildlife habitat.

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record acute toxicity to minnows andwaterfleas (15 to 16 percent mortality in100 percent effluent) in treatment wetlandeffluent samples.

Chronic Toxicity

Chronic toxicity results were available from10 treatment wetland systems. Nine of thesesystems are constructed and one is a naturaltreatment wetland. Some chronic toxicitywas identified at several sites, but chronictoxicity effects are consistently reduced bypassage through treatment wetlands withsurface discharges.

Summary

Acute and chronic whole-effluent toxicitytest results are available at a limited numberof treatment wetland sites in North America.With a few exceptions, any acute or chronictoxicity that may be present in wetlandinfluent is reduced or completely eliminatedafter the wastewater passes through thewetland. One example exists in an evapora-tive treatment wetland where toxicity tofreshwater test organisms increases withdistance from the point of wastewater inputdue to increasing total dissolved solids.

Whole-effluent toxicity tests do not distin-guish the source of toxicity; therefore,mechanisms for toxicity reduction in wet-lands are likely to vary greatly and todepend on the form of the toxicant. Avariety of metals and trace organics maycause acute or chronic toxicity in wastewa-ter effluents. Additional study with treat-ment wetlands is necessary to understandthe effects of toxicants on the wetland biotaas well as the effects of the wetland on thetoxicant.

Human Use of TreatmentWetlandsThe primary goal of most treatment wet-lands is water quality improvement. Increas-

ingly, however, treatment wetlands havemultiple purposes, and it cannot always beassumed that their water treatment goal ismore important than their other roles, suchas creating wildlife habitat or human recre-ation areas. The majority of this ExecutiveSummary focuses on the habitat functionsof treatment wetlands. This project alsosummarized what is known about theirhuman uses other than water quality im-provement.

Recognized human uses of treatment wet-lands in addition to water purification canbe lumped into five general categories:

u Nature studyu Exercise activitiesu Recreational harvestu Educationu Commercial harvest

Activities in Treatment Wetlands

Summaries of human use data exist for onlya few treatment wetland systems. The

A wooden towerprovides a pan-oramic view of theBoggy Gut Wetlandon Hilton HeadIsland, SouthCarolina.

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Arcata, California (Site No. 25), constructedwetland is used by an estimated 100,000visitors per year (Benjamin, 1993). Thislevel of activity is sustained because thesystem is located in a progressive, coastalCalifornia community near a trail systemand park-like setting. Data from Arcatasummarized in the NADB v. 2.0 indicatethat from 27,000 to 64,000 human use-daysper year (HUD/y) are devoted to generalpicnicing and relaxing. These data may alsobe expressed on a unit area basis as a totalof about 1,600 HUD per hectare per year(HUD/ha/y) for the entire Arcata Marsh andWildlife Sanctuary. At the Show Low,Arizona (Site No. 76), constructed treatmentwetland, human use data are lumped for allcategories and averaged about 370 HUD/yror about 7 HUD/ha/yr. The Iron Bridge,Florida (Site No. 13), constructed wetlandhas an overall estimated human use of about4,800 HUD/y or about 10 HUD/ha/y.

Nature Study

Nature study includes a variety of activitiesthat may be associated with treatmentwetland projects:

u Bird studyu Plant observation and identificationu Observation and identification of other

wildlife groupsu Plant and wildlife photographyu Plant and wildlife art

Few data are available that specificallydescribe any of these activities. Arcata,California, has reported data indicatingabout 10,000 HUD/yr or 165 HUD/ha/yr forbird watching. Photography and art accountfor about 360 to 900 HUD/yr at Arcata.Anecdotal information is available thatindicates that bird-watching groups regu-larly use treatment wetlands at West Jack-son County, Mississippi (Site No. 18);Hillsboro, Oregon; Show Low, Arizona(Site No. 76); Pinetop-Lakeside, Arizona;

Lakeland, Florida (Site No. 1); and IronBridge, Florida (Site No. 13). Some of thesesites are visited by organized groups on aregular basis (once a week or month), whileothers are visited by individuals or groups ona less regular schedule.

Exercise Activities

When treatment wetlands are open to thepublic, they are frequently used for activitiesthat provide exercise. Forms of exerciseknown to occur in treatment wetlands includehiking, jogging, and off-road bicycling.

Treatment wetland sites that are open to thegeneral public for these activities includeShow Low, Arizona; Pinetop-Lakeside,Arizona; Tres Rios, Arizona; Arcata, Califor-nia; Sea Pines, South Carolina; Iron Bridge,Florida; Cannon Beach, Oregon (Site No.204); Hillsboro, Oregon; and Mountain View,California (Site No. 312).

Bird counts have shown that constructed treatmentwetlands have bird diversity and population numbersas high or higher than many natural wetlands.

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Hiking and jogging at the Arcata, Califor-nia, constructed wetland is estimated asabout 18,000 HUD/yr. One specific compo-nent of this use that was identified includesabout 900 HUD/yr just for walks led by theRedwood Region Audubon Society.

No other quantitative data specificallyrecording exercise activities in treatmentwetlands were available for this review.

Recreational Harvest

A small number of treatment wetlands areopen to the public or to private individualsfor hunting and/or fishing.

A borrow pit at the Arcata Marsh andWildlife Sanctuary in California is open forfishing, but use is reported to be light andseasonal.

At Incline Village, Nevada (Site No. 310),duck blinds are available on a lottery basis.Typical hunter use days are about 877 HUD/yr or 5.6 HUD/ha/yr. About 817 ducks and60 geese are harvested per year at thisconstructed wetland.

The Iron Bridge, Florida (Site No. 13),constructed wetland is closed to the publicfrom September through March of each yearand is available to former land owners forwaterfowl hunting and fishing during thisperiod. The Houghton Lake, Michigannatural treatment wetland (Site No. 209);the Show Low, Arizona (Site No. 76),constructed wetland; and the area down-stream of the Columbia, Missouri, con-structed wetland are open to hunters asstate-controlled wildlife management areas.About 836 HUD/yr or 1.6 HUD/ha/yr areavailable for duck hunting at the Columbia,Missouri, site.

Education

Treatment wetlands have been used for avariety of educational opportunities. Some

The City of Tucson, Arizona, has made its Sweetwater Wetlands acommunity affair.

sites are open for controlled access of gradeschool and high school students and forvarious college classes and individualundergraduate and graduate research. Theonly two sites that were quantified areArcata, California, with an estimated 1,500HUD/yr and Vereen, South Carolina withan estimated 234 educational and researchHUD/yr.

Commercial Harvest

The potential to use treatment wetlands forcommercial production of food and fiberhas been discussed (Wengrzynek andTerrell, 1990; Knight, 1992; Kadlec andKnight, 1996). Types of potential commer-cial uses include:

u Plant harvesting for food (such as waterchestnuts) or fiber (such as commonreed, pulp wood, saw timber)

u Trapping of mammals for furs (nutria,muskrat, beaver)

u Aquaculture (baitfish, food fish, crayfish,frog legs, etc.)

No data concerning any of these uses wereobtained for this project.

Miscellaneous Activities

Treatment wetlands may provide human-use benefits other than those described

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above. It is not possible at this time toanticipate all of the possible uses that willbe derived from these green machines.Types of miscellaneous activities that havebeen observed include:

u School projects to name constructedwetlands

u Community service outings to help plantnew constructed wetlands, clear trash,and install bird and bat houses

u Boy Scout projects to build public usefacilities

u Citizen groups and government officialsmeeting to review wastewater manage-ment options

These activities are known to exist but havebeen difficult to quantify.

Summary

Treatment wetlands often provide humanuse benefits in addition to their primary rolefor water quality treatment. These uses varygreatly and have been quantified in only afew cases. Additional data on human use intreatment wetlands are needed to determinethe significance of these activities and to

provide information to designers on how toprovide the best opportunities forcost-effective use.

Treatment WetlandDesign for WildlifeHabitat and Human UseIntroductionThe need for information related to thepotential effects of treatment wetlands onnatural biota and humans has been recog-nized for years (Godfrey et al., 1985 andFeierabend, 1989). The ETI TreatmentWetland Habitat Project is the first attemptto provide a comprehensive summary of thestate of our knowledge concerning therelationship between treatment wetlandsand their interaction with wildlife andhuman use. While this summary indicatessignificant areas of incomplete understand-ing, it also provides a clearer view of thoseareas where conclusions are warranted.

The information summarized in this Execu-tive Summary and the companion reportindicates that treatment wetlands typicallyhave the following properties:

u Their biological structure is substantialand is dominated by relatively diverseassemblages of wetland plant species,typically including a few dominants andmany less common species that havespecific adaptations to grow in saturatedsoils

u All major animal groups and trophiclevels that occur in natural wetlands arerepresented in treatment wetlands;population size and diversity in treatmentwetlands are generally as high or higheras in other wetlands; no documentedoccurrences of detrimental effects towildlife caused by the pollutant-cleansingfunction of treatment wetlands werenoted

Permitting-related work at the Pintail Marsh in Show Low, Arizona(Site No. 76), included an assessment of the net ecological benefits ofthese effluent-dependent waters.

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u Contaminant data from treatment wet-lands for heavy metals and trace organicsare available for sediments and biologicaltissues; treatment wetlands are effectiveat reducing concentrations of thesepollutants; these data do not generallyindicate a threat to flora and fauna basedon the existing range of contaminantloadings

u Treatment wetlands are generally effec-tive at reducing levels of whole-effluenttoxicity

u Humans are using treatment wetlands fora variety of purposes in addition to waterquality enhancement

As data concerning each of these itemscontinue to become more available, the nextstep is to apply this information to thedesign and operation of new and existingtreatment wetlands. Brief discussions ofimportant areas for additional research andhow resulting knowledge might be appliedin the future are provided below. Newprojects that have benefited from thisexpanding information base have beendesigned and implemented during thelifetime of the ETI Treatment WetlandProject. Examples of these new systemsinclude municipal effluent treatment wet-land projects at Beaufort, South Carolina(Great Swamp Natural Effluent Manage-ment System), Tucson, Arizona (SweetwaterWetlands), and Palm Beach County, Florida(Wakodahatchee Wetlands).

Water Quality ConsiderationsThe effects of wetlands on water qualityhave been described in detail elsewhere(e.g., Kadlec and Knight, 1996; U.S. EPA,1999). The ETI Treatment Wetland HabitatProject is intended to provide information toresearchers who may wish to examine theflip-side of this question�namely, theeffect of the water quality on the wetlandenvironment.

Contaminants in wastewaters are known toaffect the wetland environment. Theseeffects are highly variable depending on thespecific constituents and the biologicalcomponents of the wetland in question.Research efforts should be designed tocorrelate these water quality conditions withtreatment wetland environmental condi-tions. The most basic comparisons have notbeen made between treatment wetlands withvarying dissolved oxygen and nutrientconditions and their ability to supportdiverse plant and animal populations.Although pH requirements for some indi-vidual plant and animal species are known,there are no studies of the effect of varyingpH in treatment wetlands. Although thetoxicity of many trace metals and organicsare known in laboratory studies with one ora few plant or animal species, there is verylittle information on the ecosystem-leveleffects of these substances in treatmentwetlands. The information collected for thisETI Habitat Project only provides a startingpoint for the studies needed to developempirically based treatment/habitat wetlanddesign criteria.

Biological ConsiderationsDuring the review of new and existingdischarge permits to treatment wetlands,environmental agency staff are frequentlyfaced with the difficulty of assessing thepotential for harmful environmental effects.The potential receptors of most interest aretypically the vertebrate inhabitants of thewetlands including fish, amphibians, rep-tiles, birds, and to a lesser extent, mammals.These organisms tend to be more highlyvisible to people than the invertebrates, andconcern for their fate is highest in thepublic�s priorities. While it is recognizedthat the invertebrates are also of importance,their protection is generally justified basedon their place in the food chain supportingthe vertebrate forms.

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While the use of wetlands to improve thequality of wastewaters is considered animportant goal, it is also important tobalance the benefits of meeting that goalwith the avoidance of harm to those organ-isms that will ultimately reside in the livingtreatment system.

Summary of design considerations for treatment wetland habitat and public use benefits.

It is important to protect those wildlife species thatrange outside the boundaries of the treatment wetlandHigh sediment loads can suffocate wetland emergentplant rootsHigh loadings of oxygen-demanding substances willcause nuisance conditions in treatment wetlands,including poor plant growth

Water level control is the principal tool available tocontrol plant growth and water quality improvementDeep water zones serve multiple purposes, includingimproved hydraulic mixing and residence time, a sumpfor solids storage, and perrenial habitat for fish andwaterfowlPolyculture will provide greater habitat diversity andgreater resistence to pests and operational upsetsEach plant species provides differing benefits todifferent wildlife species/groupsStructural diversity equates to habitat variety forfeeding, roosting, and nesting wildlife

Plant diversity is promoted by varying water depths,islands provide a refuge for birds and other wildlife, andirregular shorelines provide visual cover and greaterecotone length

Humans will be attracted if they have access and feelsafeBoardwalks allow the public to get a �feel� for being inthe wetland environmentThe public is eager to learn more about the structureand function of wetlandsThe public will provide useful suggestions for improve-mentThe public can be an ally during permitting and fundingfor treatment wetlandsProviding the public with a sense of ownership will helpenlist supportTreatment wetlands provide excellent classrooms forenvironmental studyObserving wildlife without disturbing it will optimize bothhabitat and public usesThe public has a right to know about any hazards orbenefits being created by a treatment wetland

Pre-treat toxic trace metals and organics

Pre-treat excessive loads of mineral and organicsedimentsPre-treat excessive organic and ammonia nitrogenconcentrations

Design flexibility to control water levels

Incorporate deep-water zones without creatinghydraulic short circuits

Utilize a diversity of plant species

Utilize plant species with known benefits to wildlifespeciesIncorporate vertical structure by planting aquatic,emergent, shrub, and canopy strata, and byinstalling snags and nesting platformsIncorporate horizontal structure by providing littoralshelves, islands, and the use of irregular shorelines

Provide parking and safe access to wetlands

Provide boardwalks and observation points

Incorporate interpretive displays

Collect public comment and incorporate in design/operation modificationsPublicize the wetlands

Inlist volunteer participation

Establish accessible monitoring points

Provide blinds for wildlife study

Maintain adequate monitoring records

Design Criteria ExplanationWater Quality Considerations

Wildlife Habitat Considerations

Public Use Considerations

The information gathered for this reportindicates that biological changes can occurin response to discharges of treated efflu-ents. These changes cover the spectrumfrom obvious to subtle. Many of thechanges that have been noted favor onegroup of species over another. The most

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normal wastewaters from the same generalsource. This greater level of caution duringproject design and review is most relevantto those wastewaters, leachates, andstormwaters that have received minimumlevels of pretreatment.

Human UseVery little information is available abouthow to best integrate human use withtreatment wetlands. Benjamin (1993)presents a highly useful summary of theissues related to public perception and useof the most-visited treatment wetland in theUnited States, the Arcata Marsh and Wild-life Sanctuary in California. That studyconcluded that the Arcata Marsh is a greatsuccess in its role as a community openspace and as a recreational, ecological, andeducational resource. Interviews identifiedbirds and wildlife viewing as the mostpopular public uses of the marsh. Thesecond most common response to questionsabout the benefits of the marsh focused onits aesthetic qualities, including scenery,beauty, and open space. The most commonresponse to the survey question concerningwhat the public disliked about the ArcataMarsh was �nothing.� These obviousbenefits are being accomplished even as theArcata Marsh meets its primary goal ofwater quality protection.

Anecdotal information indicates that similarresponses might be obtained at several othertreatment wetland sites open to the public.Studies similar to the one conducted byBenjamin (1993) should be conducted at anumber of treatment wetlands that are opento the public to develop wider guidance forhow humans interact with wetlands.

SummaryThe ETI Treatment Wetland Habitat Projectdemonstrates that both natural and con-structed treatment wetlands have substantial

common changes result in an increase ofwetland structure and function at an ecosys-tem level. Assigning value judgments tothese types of changes becomes a matter ofperspective.

There is currently no evidence that treatedwastewater effluents cause increased risksfor vertebrates in treatment wetlands. Thislack of evidence does not prove that thereare no effects, but it indicates that mosttreatment wetland projects can be permittedwithout special requirements other thanreasonable caution. Greater caution shouldbe exercised when project wastewaters areknown or suspected to contain unusuallyelevated concentrations of heavy metals,trace organics, un-ionized ammonia, orother chemicals that are likely to be acutelyor chronically toxic to aquatic and wetlandbiota. These potentially toxic chemicals areonly of special interest when they are atconcentrations above the range typical of

Alligators are a common predator in constructedtreatment wetlands throughout the southeasternUnited States.

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plant communities and wildlife populations.The concern that treatment wetlands arebotanical monocultures is not supported bythe data. Diverse and abundant populationsof wildlife use the variety of niches pro-vided by the complex plant communitiesthat develop in many treatment wetlands.

This project has documented the presenceof potentially harmful substances in thewater, sediments, and biological tissues oftreatment wetlands. While it is highly likelythat some or all of these substances at highconcentrations could create harmful condi-tions for the biota attracted to treatmentwetlands, contaminant concentrations aregenerally below published action levels andthere is apparently no documentation thatharm has occurred in any wetland intention-ally designed for water quality improve-ment. While this lack of evidence does notprove that harm does not occur somewherein a treatment wetland, current evidenceindicates that treatment wetlands supportcomplex ecosystems that are as productive

as, or more productive than, unalterednatural wetlands.

This project represents a first step at collect-ing and summarizing the information onhabitat and wildlife use of treatment wet-lands. The number of new treatment wet-land projects gathering and reporting thesetypes of data is increasing yearly. Whilesubstantial data about the diversity of plantsand animals inhabiting treatment wetlandsare available, it is hoped that these new andongoing studies will shed greater light onthe ecological functions of these systemsand their full potential for environmentalbenefit or harm.

ReferencesBastian, R.K. and D.A. Hammer. 1993. TheUse of Constructed Wetlands for Wastewa-ter Treatment and Recycling. Chapter 5, pp.59-68 in G.A. Moshiri (ed.), ConstructedWetlands for Water Quality Improvement.Lewis Publishers, Boca Raton, Florida.

Bastian, R.K., P.E. Shanaghan, and B.P.Thompson. 1989. Use of Wetlands forMunicipal Wastewater Treatment andDisposal-Regulatory Issues and EPA Poli-cies. Chapter 22, pp. 265-278. In D.A.Hammer (ed.), Constructed Wetlands forWastewater Treatment: Municipal, Indus-trial, and Agricultural. Lewis Publishers,Chelsea, Michigan.

Benjamin, T.S. 1993. Alternative Wastewa-ter Treatment Methods as CommunityResources: The Arcata Marsh and Beyond.Master of Landscape Architecture Thesis,University of California at Berkeley.

CH2M HILL, 1997. Treatment WetlandHabitat and Wildlife Use AssessmentProject. Prepared for the U.S. Environmen-tal Protection Agency, U.S. Bureau ofReclamation, and the City of Phoenix withfunding from the Environmental Technol-ogy Initiative Program.

CH2M HILL and Payne Engineering. 1997.Constructed Wetlands for Livestock Waste-water Management. Literature Review,Database, and Research Synthesis. ReportPrepared for the Gulf of Mexico Program,

The Cobble SiteDemonstration

Treatment Wetlandfor the City of

Phoenix tests thefeasibility of

recreating habitatin the dry channel

of the Salt River.

29

Nutrient Enrichment Committee, StennisSpace Center, MS.

Frederick, P.C. and S.M. McGehee. 1994.�Wading Bird Use of Wastewater TreatmentWetlands in Central Florida, USA. � Colo-nial Waterbirds 17(1):50-59.

Freierabend, J.S. 1989. Wetlands: TheLifeblood of Wildlife Chapter 7, pp. 107-118. In D.A. Hammer (ed.), ConstructedWetlands for Wastewater Treatment: Mu-nicipal, Industrial, and Agricultural.Chelsea, Michigan: Lewis Publishers. 1989.

Friend, M. 1987. (ed.) Field Guide toWildlife Diseases. Volume 1. General FieldProcedures and Diseases of Migratorybirds. U.S. Department of the Interior, Fishand Wildlife Service. National WildlifeHealth Center, Madison, Wisconsin.

Friend, M. 1985. Wildlife Health Implica-tions of Sewage Disposal in Wetlands.Chapter 17, pp. 262-269 in: P.J. Godfrey,E.R. Kaynor, S. Pelczanski, and J.Benforado (eds.). Ecological Consider-ations in Wetlands Treatment of MunicipalWastewaters. Van Nostrand Reinhold, NewYork.

Godfrey, P.J., E.R. Kaynor, S. Pelczarski,and J. Benforado. 1985. (eds.) EcologicalConsiderations in Wetlands Treatment ofMunicipal Wastewaters. Van NostrandReinhold, New York, 473 pp.

Guntenspergen, G.R. and F. Stearns. 1985.Ecological Perspectives on Wetland Sys-tems. Chapter 5, pp. 69-97 in: P.J. Godfrey,E.R. Kaynor, S. Pelczanski, and J.Benforado (eds.). Ecological Consider-ations in Wetlands Treatment of MunicipalWastewaters. Van Nostrand Reinhold, NewYork.

Kadlec, R.H. and R.L. Knight. 1996. Treat-ment Wetlands. Lewis Publishers, BocaRaton, FL, 893 pp.

Knight, R.L. 1992. Ancillary Benefits andPotential Problems With the Use of Wet-lands for Nonpoint Source Pollution Con-trol. Ecological Engineering 1:97-113.

Knight, R.L., R.W. Ruble, R.H. Kadlec, andS. Reed. 1993. Wetlands for WastewaterTreatment: Performance Database. Chap-ter 4, pp. 35-58 in: G.A. Moshiri (ed.).

Constructed Wetlands for Water QualityImprovement. Lewis Publishers, BocaRaton, FL.

Knight, R.L. 1997. Wildlife Habitat andPublic Use Benefits of Treatment Wetlands.Water Science & Technology 35(5): 35-43.

McAllister, L.S. 1992. Habitat QualityAssessment of Two Wetland TreatmentSystems in Mississippi: A Pilot Study. U.S.Environmental Protection Agency. Environ-mental Research Laboratory, Corvallis,Oregon. November 1992. EPA/600/R-92/229.

McAllister,L.S. 1993a. Habitat QualityAssessment of Two Wetland TreatmentSystems in the Arid West: A Pilot Study. U.S.Environmental Protection Agency. Environ-mental Research Laboratory, Corvallis,Oregon. July 1993. EPA/600/R-93/117.

McAllister,L.S. 1993b. Habitat QualityAssessment of Two Wetland TreatmentSystems in Florida: A Pilot Study. U.S.Environmental Protection Agency. Environ-mental Research Laboratory, Corvallis,Oregon. November 1993. EPA/600/R-93/222.

Mitsch, W.J. and J.G. Gosselink. 1993.Wetlands. Second Edition. Van NostrandReinhold, New York. 722 pp.

Many constructed treatment wetland designs includediverse plantings of native wetland species to providewildlife habitat as well as project aesthetics.

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Pries, J.H. 1994. Wastewater andStormwater Applications of Wetlands inCanada. North American Wetlands Conser-vation Council (Canada). Issues Paper,No. 1994-1, Ottawa, Canada.

Reed, Jr., P.B. 1988. National List of PlantSpecies that Occur in Wetlands: NationalSummary. U.S. Fish and Wildlife Service.Biol. Rep. 88(24) 244 pp.

Sather, J.H. 1989. Ancillary Benefits ofWetlands Constructed Primarily for Waste-water Treatment. Chapter 28a, pp. 353-358in: D.A. Hammer (ed.) Constructed Wet-lands for Wastewater Treatment, Municipal,Industrial, and Agricultural. Lewis Publish-ers, Chelsea, MI.

South Florida Water Management District(SFWMD). 1997. Everglades NutrientRemoval Project. Year 2 Synopsis. WestPalm Beach, Florida.

Spalding, M.G. 1990. Antemortem Diagno-sis of Eustrongylidosis in Wading Birds(Ciconiiformes). Colonial Waterbirds 13(1):75-77.

U.S. Environmental Protection Agency(U.S. EPA) 1993. Constructed Wetlands forWastewater Treatment and Wildlife Habitat� 17 Case Studies. EPA832-R-93-005, 174pp.

U.S. EPA. 1999. Free Water Source Con-structed Wetlands: Technology Assessment.EPA 823- -99- . __ pp.

U.S. EPA. 1986. Quality Criteria for Water.EPA-44015-86-001.

U.S. EPA. 1989. Short-Term Methods forEstimating the Chronic Toxicity of Effluentsand Receiving Waters to Freshwater Organ-isms. EPA/600/4-89/001.

Wengrzynek, R.J. and C.R. Terrell. 1990.Using Constructed Wetlands to ControlAgricultural Nonpoint Source Pollution.In: P.F. Cooper and B.C. Findlater (eds.).Proceedings of the International Conferenceon Use of Constructed Wetlands in WaterPollution Control. Cambridge, UnitedKingdom. Pergamon Press, Oxford, UK.

Wilhelm, M., S.R. Lawry, and D.D. Hardy.1989. Creation and Management of Wet-lands Using Municipal Wastewater in

Northern Arizona: A Status Report. Chapter13a, pp. 179-185 in D.A. Hammer (ed.),Constructed Wetlands for WastewaterTreatment: Municipal, Industrial, andAgricultural. Lewis Publishers, Chelsea,MI.

Wren, C.D., C.A. Bishop, D.L. Stewart, andG.C. Barrett. 1997. Wildlife and Contami-nants in Constructed Wetlands andStormwater Ponds: Current State of Knowl-edge and Protocols for Monitoring Con-taminant Levels and Effects in Wildlife.Canadian Wildlife Service Ontario Region,Technical Report Series Number 269.

Prepared by CH2M HILL with funding fromthe Environmental Technology InitiativeProgram

Project Sponsors were: U.S. Bureau of Reclamation U.S. Environmental Protection Agency City of Phoenix

Additional Copies of this Executive Sum-mary and the NADB v.2.0 can be obtainedfrom NTIS.