Aquatic Plant Management and Aquatic Plant Management and Ecological Condition of Florida SpringsEcological Condition of Florida Springs

Questions for ConsiderationQuestions for Consideration

Jason M. EvansJason M. EvansSprings Research SymposiumSprings Research Symposium

University of FloridaUniversity of FloridaAugust 21, 2007August 21, 2007

Major Invasive PlantsMajor Invasive Plants

Hydrilla (Hydrilla (Hydrilla verticillataHydrilla verticillata))

Water hyacinth (Water hyacinth (Eichhornia crassipesEichhornia crassipes))

Water lettuce (Water lettuce (Pistia stratiotesPistia stratiotes))

Wakulla HydrillaWakulla Hydrilla

St. Johns HyacinthSt. Johns Hyacinth

www.jou.ufl.edu/pubs/onb/S05/d_green.html

http://aquat1.ifas.ufl.edu/guide/stboatbg.gif

Ichetucknee Water LettuceIchetucknee Water Lettuce

Other Invasive PlantsOther Invasive Plants

Eurasian milfoil (Eurasian milfoil (Myriophyllum spicatumMyriophyllum spicatum))

Indian Hygrophila (Indian Hygrophila (Hygrophila polyspermaHygrophila polysperma))

Brazilian Elodea (Brazilian Elodea (Egeria densaEgeria densa))

Giant Salvinia (Giant Salvinia (Salvinia molestaSalvinia molesta) ?) ?

Control MethodsControl MethodsHerbicidesHerbicides– Fluridone (hydrilla, hygrophila, salvinia)Fluridone (hydrilla, hygrophila, salvinia)

Difficult in flowing waters due to long contact requirementsDifficult in flowing waters due to long contact requirementsFluridone resistant biotypesFluridone resistant biotypesNon-target concernsNon-target concerns

– Endothall (hydrilla, hygrophila)Endothall (hydrilla, hygrophila)Non-target concernsNon-target concerns

– 2-4,D (hyacinth, hygrophila)2-4,D (hyacinth, hygrophila)Non-target concernsNon-target concerns

– Glyphosate (hyacinth)Glyphosate (hyacinth)Non-target concernsNon-target concerns

– Diquat (hydrilla, hyacinth, lettuce, salvinia)Diquat (hydrilla, hyacinth, lettuce, salvinia)Non-target concernsNon-target concerns

– Copper (hydrilla, hyacinth, lettuce, salvinia)Copper (hydrilla, hyacinth, lettuce, salvinia)Sediment accumulationSediment accumulationManatee toxicity concernsManatee toxicity concerns

Other ControlOther ControlPhysicalPhysical– Mechanical harvestMechanical harvest

ExpenseExpenseFragment sprouting, particularly hydrillaFragment sprouting, particularly hydrillaNon-target concernsNon-target concerns

– Manual harvestManual harvestLabor intensiveLabor intensive

BiologicalBiological– Grass carp Grass carp

Can over graze native plantsCan over graze native plants

– Biocontrol insectsBiocontrol insectsResults not immediateResults not immediateOngoing research and lengthy risk assessmentsOngoing research and lengthy risk assessmentsNon-target concernsNon-target concernsPerhaps most sustainable over long-termPerhaps most sustainable over long-term

Question 1Question 1

Does increased nutrient (particularly Does increased nutrient (particularly nitrate) loading into Florida springs also nitrate) loading into Florida springs also increase the spread, growth, and coverage increase the spread, growth, and coverage of major invasive plant species?of major invasive plant species?

Question 2Question 2

Would decreased nutrient loading lessen Would decreased nutrient loading lessen the spread, growth, and coverage of the spread, growth, and coverage of invasive plant species?invasive plant species?

Question 3Question 3

What are the habitat effects of major invasive What are the habitat effects of major invasive plants?plants?– Displacement of native plantsDisplacement of native plants– Hypothesis that apple snail and limpkin decline in Hypothesis that apple snail and limpkin decline in

Wakulla directly related to hydrilla invasionWakulla directly related to hydrilla invasion– Edge of water hyacinths in St. Marks system found to Edge of water hyacinths in St. Marks system found to

harbor high densities and diverse assemblages of harbor high densities and diverse assemblages of invertebrates (apple snail, crayfish, amphipods), fish, invertebrates (apple snail, crayfish, amphipods), fish, and wading birds (Bartodziej and Leslie 1998)and wading birds (Bartodziej and Leslie 1998)

– Water lettuce and hyacinth preferred habitat for Water lettuce and hyacinth preferred habitat for endemic dense hydrobe snail (endemic dense hydrobe snail (Aphaostracon pycnumAphaostracon pycnum)) in Alexander Spring run (Thompson 1968)in Alexander Spring run (Thompson 1968)

Question 4Question 4

What, if any, non-target effects are associated with What, if any, non-target effects are associated with aquatic plant management activities?aquatic plant management activities?– Native plant impactsNative plant impacts– Deposition of organic matter and “pulsed” nutrient releaseDeposition of organic matter and “pulsed” nutrient release– Grazer impacts, both toxicological and habitat disruptionGrazer impacts, both toxicological and habitat disruption

State of Washington (2003) recently found that diquat can be “highly State of Washington (2003) recently found that diquat can be “highly toxic” to apple snails (toxic” to apple snails (Pomacea paludosaPomacea paludosa) and ) and Hyalella azteca Hyalella azteca at at ecologically relevant dosages (.36 and .07 ppm, respectively)ecologically relevant dosages (.36 and .07 ppm, respectively)Concerns about crayfish (Concerns about crayfish (Procambarus peninsulanusProcambarus peninsulanus) die-off ) die-off observed in Wakulla after hydrilla treatment with endothall (Aquathol observed in Wakulla after hydrilla treatment with endothall (Aquathol K)K)

– Algal community compositionAlgal community compositionOpportunistic colonization by algae/cyanobacteria Opportunistic colonization by algae/cyanobacteria Lyngbya wolleiLyngbya wollei resistant/tolerant to common herbicide formulations resistant/tolerant to common herbicide formulations

Proposition 1Proposition 1

History of invasive plant colonization and History of invasive plant colonization and control methods should be directly control methods should be directly considered when evaluating the ecological considered when evaluating the ecological condition of Florida spring systems condition of Florida spring systems

Proposition 2Proposition 2

In springs impacted by overgrowth of In springs impacted by overgrowth of nuisance algae, careful experimentation nuisance algae, careful experimentation with novel aquatic plant management with novel aquatic plant management approaches – including tolerance of higher approaches – including tolerance of higher coverage levels by coverage levels by already establishedalready established invasive plant species – should be invasive plant species – should be explored in conjunction with broader explored in conjunction with broader ecosystem rehabilitation and recovery ecosystem rehabilitation and recovery goals goals