NREM 665NREM 665Salt MarshesSalt Marshes

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I. Tidal Salt Marshes (TSMs)

A. Def: halophytic grassland & dwarf brushwood on alluvial sediments bordering saline H2O bodies whose H2O level fluctuates tidally (Beeftink1977)

B. Found along coasts in mid & high latitudes

1 C h1. Common where:

a. accumulation of sediment ≥ land subsidence

b. there is adequate protection from waves; (M&G 2000)

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Global salt marsh & mangrove distribution4

C. TSMs often appear to be veg. monocultures of Spartina alterniflora

1. Veg. varies across salinity, flooding gradients, provides habitat for various of spp. adapted to deal w/ stresses of this env.

2. Diff. plant assocs. dominate coastlines in diff. countries but ecol. structure/function similar

D. TSMs mainly intertidal, located on narrow fringe (m) of steep shoreline OR large expanse (km) in coastal plains

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Estuarine Salinity Gradient

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ConnecticutConnecticut River estuary

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Altamaha River estuary, GA

http://coastgis.marsci.uga.edu/summit/images/altsalinity.jpg 8

Tidal salt marsh (Spartina alterniflora) in coastal NC 9

Tijuana estuary, CA

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San San QuintinQuintin Marsh, MexicoMarsh, Mexico

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Hawai‘i salt marsh: Honu‘apo

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Honu‘apo

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Honu‘apo

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Transition from Salt to Fresh Marsh

Plant Species Diversity

Salt: 17 sppSalt: 17 spp.

Brackish: 40 sppBrackish: 40 spp.

Intermediate: 54 spp.

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Tidal Freshwater Marshes

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E. TSMs boundaries set by:

1 U li it f fl di f t tid (B fti k 1977) & l t1. Upper: limit of flooding of extreme tides (Beeftick 1977) & plant competition (Bertness et al. 2002)

2 Lower: physical stresses: depth & duration of flooding2. Lower: physical stresses: depth & duration of flooding, mechanical effects of waves, sediment availability & erosion (Chapman 1960; Bertness et al. 2002)

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F. TSMs divided into 2 zones: low & high marsh (M&G 2000)

1 LM fl d d il hi h d1. LM: floods daily, higher prod.

2 HM: floods irregularly lower prod2. HM: floods irregularly, lower prod.

3 Stress-tolerant plants dominate LM while competitively-superior3. Stress tolerant plants dominate LM while competitively superior plants dominate HM (Bertness et al. 2002)

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(Mitsch & Gosselink 2000)(Mitsch & Gosselink 2000)

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Distinct zonation patterns in SE & gulf coast TSMsg

23(Mitsch & Gosselink 2000)

Zonation in a southern New England salt marsh

24(Bertness et al. 2002)

4. LM has tidal creeks

a bidirectional flow stable channelsa. bidirectional flow, stable channels

b. productivity creek banks > interior marsh due to better p yflushing of salts, toxins (M&G 2000)

5. Pannes

a. bare, exposed, or H2O filled depressions where evap conc. salts

b. Only a few, if any, spp. can tolerate these conditions: BG algae or other halophytes Ruppia (wigeon grass), Battis(pickelweed)(pickelweed)

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Tidal creek network behind a barrier island in coastal NC

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Tidal salt marsh creek in coastal NC

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Salt marsh Salt marsh pannepanne

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G. Ecosystem structure

1. Primary producers: vegetation & algae

a. Herbaceous veg: S. alterniflora, S. patens, Juncusg pgeradi/romerianus (needlerush)

b. Salt tolerant spp: Salicornia (glasswort), Battis maritima(pickelweed), Distichlis spicata (salt grass)

c. Benthic algae, diatoms:

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2. Consumers: insects (grasshoppers, weevils), crustaceans (crabs), birds, mammals

a. Birds:

i wading & song birds (permanent): marsh wren Capei. wading & song birds (permanent): marsh wren, Cape Sable seaside sparrow, clapper rail

ii. waterfowl (migratory): mallards, widgeons, teals, ate o ( g ato y) a a ds, dgeo s, tea s,geese

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b. Mammals: muskrat (native) & nutria (invasive) to NA

i. nutria consume leaves, shoots in GS, belowground tubors in winter

Note: Exclosure plot 100 ft x 100 ft

http://www pwrc usgs gov/factshts/nutria pdf

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http://www.pwrc.usgs.gov/factshts/nutria.pdf

Characteristic salt marsh species

(Boaden & Seed

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& Seed 1985)

Salt marshmarsh

food webs

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H. Odum’s Big 2: Outwelling & Subsidy

1. Outwelling (Teal 1962, Odum 1971): “Coastal wetlands & estuaries tend to produce an annual excess of organic matter some ofan annual excess of organic matter, some of which is exported seaward where it represents a major energetic pathway & supports coastal fisheries”fisheries

a. applicable for exchange bet. marsh & estuary and estuary & ocean y y

b. modified by geomorphology of estuary & position of marsh in estuary

Eugene P. Odum1913-2002

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Outwelling Hypothesis

Organic matter from salt marshg(Teal 1962, Odum 1971)

Coastal Ocean

(MacKenzie 2008)

(Teal 1962) 36

2. Critiques of Outwelling Hypothesis

a. Haines (1977)

i. found little evidence for direct OM export from marsh studied

ii. suggested that dominant mode of C export is via DOC supporting plantktonic food chain

b. Taylor & Allanson (1995)

i foundi. found

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3. Revised Outwelling Hypothesis (Odum 2000)

a. Outwelling higher in marshes w/ high tide range or that are

t thopen to the sea

b. Exchanges of C & nutrients bet marsh & estuary arebet. marsh & estuary are aperiodic w/ storms or w/ spring tides

c. Transient fish & inverts. serve as

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4. Tidal Subsidy Concept (Odum 1980)

a. “…tides, by flushing salts & other toxins out of the marsh & by bringing in nutrientsof the marsh & by bringing in nutrients, stimulate marsh growth.”

LocationNPP

(g dw m-2 yr-1) ReferenceMassachusetts (tall) 1 320 Valiela et al 1976Massachusetts (tall) 1,320 Valiela et. al. 1976

Massachusetts (short) 420 Valiela et. al. 1976

G i 3 700 St d 1976Georgia 3,700 Stroud 1976

Mississippi 1,964 de la Cruz 1974

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Louisiana 1,473-2,895 White et. al. 1978

5. Current thoughts on TSM productivity

a. Factors influencing primary production:

i Withi Siti. Within Site:ii. Across Sites:iii. Within & Across:

MGFMGFsTSMs

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I. TSM/MG ecosystem services valued @ $9,990 ha-1 yr-1 (Costanza et al 1997)al. 1997)

1. primary productivity

2. export C → basis of estuarine food web

3. interface bet terrestrial & marine ecosystems y

4. protect against storm surge & tsunamis

J. Due to ↑ construction of dams/reservoirs, sediment delivery to estuaries & TSMs ↓ considerably

1 i l f TSM ’t k / i i1. in some cases large areas of TSM can’t keep pace w/ rising sea levels & are experiencing subsidence (Agardy & Alder 2005)

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K. Trophic Cascades in TSMs

Potential of significant gherbivory by marsh periwinkle

(Silliman et al. 2005)

• Drought conditions weaken vegetation (Spartina alterniflora)

• Overharvesting of blue crabs →↑ periwinkle populations →↑ periwinkle populations →↑mechanical damage & disease

• ↓ productivity of Spartina →bare patches & die-back

42http://newell.myweb.uga.edu/periwink.htm

(Silliman & Bertness 2002)

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