Why is periphyton so abundant in the Everglades?

Why is periphyton so abundant inthe Everglades?Evelyn Gaiser&The Periphyton GroupDepartment of Biology,FIU

Periphyton in the Everglades• Ubiquitous in natural areas• Grows on all benthic substrates• High productivity in low nutrient,high stress environmentTypesCompositionProductivity

Types of Periphyton CommunitiesMetaphytonEpiphytonEpilithon• Benthic periphyton communities are diverse– >80% of freshwater algae and cyanobacteria live attached tosubstrates• Species diversity linked to habitat heterogeneity• Benthic biomass exceeds planktonic biomass in wetlands– Nutrients are more available from substrates than in water– Large surface area for colonization– Nearby neighbors increase efficiency of nutrient recycling

Composition of Periphyton Communities• Filamentouscyanobacteriadominatebiovolume• Scytonemahofmanii andSchizothrixcalcicola dominatebut 27 otherfilamentous cyanoshave been foundPhotos by M. Gantar• Eubacteria arealso abundant

Composition of Periphyton Communities• Filamentous cyanos precipitateCaCO 3 in this hardwaterenvironment• Calcite comprises 20-90% ofperiphyton biomass, dependingon hydrology10080% CalcitePhotos by M. Gantar60402000 4 8 12 16 24 48Hydroperiod (months)Davis, Gaiser et al. In Press

Composition of Periphyton Communities• Coccoid cyanobacteria are alsoabundant (124 taxa catelogued)• These produce polysaccharideglue that holds the mat togetherDonar, Gantar & Gaiser 2004

Composition of Periphyton Communities• Over 340freshwater and720 marinediatom taxacateloguedfrom S. Fla.periphyton*• Diatoms alsoproducecopious EPSPhotos by M. Gantar, A. Wachnicka*Images are posted athttp://serc.fiu.edu/periphyton

Productivity of Periphyton CommunitiesANPP by Site (g C m -2 yr -1 )SRSTransect6TS/PhTransect543211 101123 456 8796004002000100003000200010000SRS transect1 2 3 4 5 6TS transect1 2 3 4 5 6 7 8PeriphytonSawgrassMangrovesSeagrass9 10 11Periphyton dominates primary production in 8 of 17 sites in the FCE

Productivity of Periphyton CommunitiesGPP g C m -2 d -1Everglades (WCA2A)L. Okeechobee6.628.25McCormick et al. 1998Havens et al. 1999Everglades examplesEverglades (WCA 2A)Everglades (ENP)6.980.99McCormick et al. 2001Browder et al. 1984Mean = 5 g C m -2 d -1Everglades (ENP)0.98Swift 1989Everglades (ENP, TS)3.81Gaiser et al. 2005FW Wetland, Belize7.27Rejmankova & Komarkova 2000L. Schultz Creek, ALLake Borax, CALawrence Lake, MILake Michigan, MI0.230.272.000.09Stock & Ward 1989Wetzel 1966Rich & Wetzel 1978Barko et al. 1977Other periphyton examplesMean = 0.5 g C m -2 d -1Lake Marion, ON0.11Gruendling 1971Red Cedar River, MI0.28King and Ball 1966Hart's Run, KY0.26Kevern et al. 1966Salt marsh, TX0.19Hall et al., 1985Duplin R. Marsh, GA0.41Pomeroy et al. 1981Lousiana Marsh, LA1.10Moncreiff 1983

Productivity of Periphyton CommunitiesBiomass of plants and periphyton in wet prairie sitesMacrophytes59 +/- 34 g DM m -2Periphyton228 +/-96 g AFDM m -2· Surveysites ofRoss &Gaiser

Why is periphyton so abundant???

Factors Influencing Periphyton AttributesWater Chemistry•Salinity•Nutrients•pH, CaCO 3Temperature•Range•SeasonalityHydrology•Water depth•DurationPeriphyton•Structure•Composition•AbundanceLight•Intensity•Quality•PhotoperiodConsumer interactionsFirePlant interactions

Factors Influencing Periphyton AttributesWater Chemistry•Salinity•Nutrients•pH, CaCO 3Temperature•Range•SeasonalityHydrology•Water depth•DurationPeriphyton•Structure•Composition•AbundanceLight•Intensity•Quality•PhotoperiodConsumer interactionsFirePlant interactions

Periphyton mats tolerate a broad salinity rangefrom marshes to mangroves to seagrass beds

Mats have similar appearance but differentcommunity composition

Strong salinity relationships allow reliablepredictionsModel: Biscayne Bay WetlandsModel: Florida BayDiatom-Predicted Salinity (ppt)302520151050R 2 = 0.91RMSE = 0.140 5 10 15 20 25 30Observed Salinity (ppt)Diatom-Predicted Salinity (ppt)4032241680R²=0.96RMSE = 2 ppt0 8 16 24 32 40Observed Salinity (ppt)

Why is periphyton so abundant in theEverglades?• Salinity – similar periphyton mats exist across broad salinityrange with species swapping functional roles across spectrum

Factors Influencing Periphyton AttributesWater Chemistry•Salinity•Nutrients•pH, CaCO 3Temperature•Range•SeasonalityHydrology•Water depth•DurationPeriphyton•Structure•Composition•AbundanceLight•Intensity•Quality•PhotoperiodConsumer interactionsFirePlant interactions

Seasonality is consistent across sites0.140.12Periphyton Production (mean g C m -2 d -1 )FCE LTER SRS 1-3, TS 4-6, 9-112000-2004T = 17-32 ºC0.10.080.060.04Dry season0.020J F M A M J J A S O N DMonth• Periphyton production is less seasonally variable in subtropics than temperatewetlands• Peak biomass is in late fall and early spring linked to hydrology, photoperiod andnutrient influx

Why is periphyton so abundant in theEverglades?• Salinity – similar periphyton mats exist across broad salinityrange with species swapping functional roles across spectrum• Temperature – high temperatures with relatively lowfluctuations allow sustained production throughout the year

Factors Influencing Periphyton AttributesWater Chemistry•Salinity•Nutrients•pH, CaCO 3Temperature•Range•SeasonalityHydrology•Water depth•DurationPeriphyton•Structure•Composition•AbundanceLight•Intensity•Quality•PhotoperiodConsumer interactionsFirePlant interactions

Periphyton production is high although waternutrients are lowIn the natural Everglades, water column phosphorusconcentration ranges from about 3-10 ppb (µg L -1 )Water Total PhosphorusTP µg.L -120181614121086420PeriphytonNo Periphyton0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22Days after re-floodingPeriphyton releasessequestered P to the watercolumn upon re-floodingPeriphyton re-sequesters lostP maintaining water P atambient levelsThomas, Gaiser et al., In Press

Difference from control at 5 m (µg g -1 )2520151050-5-10100050020010030 ppb15 ppb5 ppbWater TPPeriphyton TPPeriphyton regulates water Pconcentration untilcommunities are P saturated30150 5098 99 00 01 0203YearGaiser et al. 2004

Periphyton biomass declines with added PMat Ash-Free Dry Mass (g m -2 )250200150100500R 2 = 0.13P < 0.000110 100 1000 10000Periphyton Mat TP (µg g -1 )Prior toPaddition180 dafter 30ppbadditionGaiser et al. 2004

Inverse trend occurs throughout theEverglades100R 2 (all sites) = 0.491010 100 1000 10000Periphyton biomass (dry g m -2 )1000Periphyton TP (µg g -1 )Ambient EnrichedWCA-1WCA-2AWCA-3ASRSTSExperimentGaiser et al. L & O

Compositional responses to P concentrationRelative Abundance5432106040200605040Brachysira neoexilis v. 02Encyonema evergladianumFragilaria synegrotesca1008060402008060402002015Mastogloia smithiiNitzschia amphibiaGomphonema parvulumAll transectandexperimentaldatacombined302010105010 100 1000 10000010 100 1000 10000Periphyton TP Content Gaiser et al. 2005

Strong phosphorus relationships allow reliablepredictionsSpecies-Predicted Periphyton TP (µg g -1 )10000100010010Model: Flume ExperimentR 2 = 0.70RMSE boot = 1801:110 100 1000 10000Species--Predicted Periphyton TP (µg g -1 )1000010001001010Model: All Everglades TransectsR 2 = 0.56RMSE boot = 2801:1100 1000 10000Measured Periphyton TP (µg g -1 )Measured Periphyton TP (µg g -1 )Gaiser et al. 2005

Phosphorus increases green algal productionmg O 2 .g DW -1GPP8765432100 200 400 600 800 1000 1200Site ASite BSite CThis is anunstable statemg O 2 .g DW -1Respiration0-0.2-0.4-0.6-0.8-1-1.2-1.40 200 400 600 800 1000 1200Periphyton TP (µg g -1 )

The endpoint of the eutrophication process isa cattail stand devoid of periphytonFlume C5 PPB ChannelJuly 2005Flume A30 PPB ChannelJuly 2005

Why is periphyton so abundant in theEverglades?• Salinity – similar periphyton mats exist across broad salinityrange with species swapping functional roles across spectrum• Temperature – high temperatures with relatively lowfluctuations allow sustained production throughout the year• Nutrients – periphyton sustains highest production underlowest nutrient concentrations indicating efficient recycling

Factors Influencing Periphyton AttributesWater Chemistry•Salinity•Nutrients•pH, CaCO 3Temperature•Range•SeasonalityHydrology•Water depth•DurationPeriphyton•Structure•Composition•AbundanceLight•Intensity•Quality•PhotoperiodConsumer interactionsFirePlant interactions

Consumer effects – or lack thereof10080604020012108642040Site 6Site 37** ***3020100Control ExclosureControl ExclosureDorn, Trexler & Gaiser, SubmittedPeriphyton matabundance (g ashfree dry mass/m 2 )Mean density ofmat-dwellingprimaryconsumers(no./g dry mass)Mean density ofintermediateconsumers(no./m 2 )

Why is periphyton so abundant in theEverglades?• Salinity – similar periphyton mats exist across broad salinityrange with species swapping functional roles across spectrum• Temperature – high temperatures with relatively lowfluctuations allow sustained production throughout the year• Nutrients – periphyton sustains highest production underlowest nutrient concentrations indicating efficient recycling• Consumer Interactions – periphyton feeds the food web butreduced edibility and high turnover mask consumer effects

Factors Influencing Periphyton AttributesWater Chemistry•Salinity•Nutrients•pH, CaCO 3Temperature•Range•SeasonalityHydrology•Water depth•DurationPeriphyton•Structure•Composition•AbundanceLight•Intensity•Quality•PhotoperiodConsumer interactionsFirePlant interactions

Periphyton is expansive in short-hydroperiodareas of the marl prairie

Most marl prairie sites dry down, leavingperiphyton exposed to desiccation

Hydrology regulates periphyton structureProportion of Max value0.80.60.40.20N = 1200 Sites in Marl PrairieUtricularia Epiphytes MatVegetationSoilpurpureathicknessCoverDepth1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5Hydroperiod Index1 = 100-150 Days2 = 150-200 Days3 = 200-250 Days4 = 250-300 Days5 = 300-350 Days

Periphyton thrives in shallow waterPeriphyton AFD Biomass (g m -2 )400350300250200150N = 437 Sites in Marl Prairie0-5 6-10 11-20 21-30 31-40October Water Depth (cm)Water Depth (cm)6050403020100October 2003October 2004A B C D E FPopulation

Desiccated periphyton recovers quickly uponrehydrationProduction (GPP µg C cm -3 mol photon -1 )3025201510500 1 2 3 4 5 6 7 8 910 11 12 13 14 15 16 17 18 19 20 21Days since re-hydratedThomas, Gaiser et al., In Press

Periphyton composition responds quickly tochanges in hydroperiodNMDS Relative Algal AbundancesShort Hydroperiod SitesLong Hydroperiod SitesS. calcicolaDesiccation -resistantspeciesS. hofmaniiAxis 2DryWetDryWetChroococcidiopsisAxis 1Gottlieb, Richards & Gaiser 2005

Why is periphyton so abundant in theEverglades?• Salinity – similar periphyton mats exist across broad salinityrange with species swapping functional roles across spectrum• Temperature – high temperatures with relatively lowfluctuations allow sustained production throughout the year• Nutrients – periphyton sustains highest production underlowest nutrient concentrations indicating efficient recycling• Consumer Interactions – periphyton feeds the food web butreduced edibility and high turnover mask consumer effects• Hydrology – communities are adapted to particularhydroperiod regimes and recover quickly after desiccating

Factors Influencing Periphyton AttributesWater Chemistry•Salinity•Nutrients•pH, CaCO 3Temperature•Range•SeasonalityHydrology•Water depth•DurationPeriphyton•Structure•Composition•AbundanceLight•Intensity•Quality•PhotoperiodConsumer interactionsFirePlant interactions

How do periphyton and vegetation interact?Periphyton removal treatment plotPaired periphyton/plantremoval plots; Site B“...as heavy floating periphyton matsdry they can flatten and kill theaboveground portion of muhly grassand other vulnerable species.”Pimm et al., 2002. “Sparrow in the Grass”

How do periphyton and vegetation interact?ControlPeriphyton RemovalPlant RemovalPlant turnoverand periphytonbiomass accrualmeasured in 48paired plots at 3sites, bimonthlyfor 3 years

Do plants shade-out periphyton?Shade houses reduced lightpenetration by 0, 30, 50, 60, 70,80, 90 and 98%.Periphyton sampled monthlyduring 6 month wet seasonPeriphyton incubated monthlyunder same light intensities todetermine P/I curve

Periphyton sustains maximum growth underbroad range of light intensity76543210Daily GPP (g O 2 .m -2 .d -1 )0 20 40 60 80 100Percent Irradiance TransmissionMonth12345Thomas, Gaiser et al., Submitted

Why is periphyton so abundant in theEverglades?• Salinity – similar periphyton mats exist across broad salinityrange with species swapping functional roles across spectrum• Temperature – high temperatures with relatively lowfluctuations allow sustained production throughout the year• Nutrients – periphyton sustains highest production underlowest nutrient concentrations indicating efficient recycling• Consumer Interactions – periphyton feeds the food web butreduced edibility and high turnover mask consumer effects• Hydrology – communities are adapted to particularhydroperiod regimes and recover quickly after desiccating• Plant Interactions – TBA but conjecture that periphyton mayeffect plants through smothering but also through seed bank• Light – periphyton sustains high productivity even under thelowest light intensties, minimizing shade-effects of plants

Factors Influencing Periphyton AttributesWater Chemistry•Salinity•Nutrients•pH, CaCO 3Temperature•Range•SeasonalityHydrology•Water depth•DurationPeriphyton•Structure•Composition•AbundanceLight•Intensity•Quality•PhotoperiodConsumer interactionsFirePlant interactions

When all else fails, try fire…

Periphyton sampled from adjacentburned/unburned plotsGradient of moisturePeriphytonTop unburnedElevationgradientedge unburnedflooded unboiledAfterfireTop burnededge burnedflooded boiled

Burned periphyton recovers slowlyunburned moundsunburned poolstop of burned moundsedges of burned moundspools in burned areas10mg O 2 /L500 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19DaysThomas et al., in prep

Burned periphyton leaches and then reabsorbsnutrientsµg/L80604020Water Total Phosphorusunburned moundsunburned poolstop of burned moundsedges of burned moundspools in burned areasmg/L08765432100 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19Water Total Nitrogen0 1 2 3 4 5 6 7 8 9 10 11 1213 1415 16 1718 19DaysThomas et al., in prep

Why is periphyton so abundant in theEverglades?• Salinity – similar periphyton mats exist across broad salinityrange with species swapping functional roles across spectrum• Temperature – high temperatures with relatively lowfluctuations allow sustained production throughout the year• Nutrients – periphyton sustains highest production underlowest nutrient concentrations indicating efficient recycling• Consumer Interactions – periphyton feeds the food web butreduced edibility and high turnover mask consumer effects• Hydrology – communities are adapted to particularhydroperiod regimes and recover quickly after desiccating• Plant Interactions – TBA but conjecture that periphyton mayeffect plants through smothering but also through seed bank• Light – periphyton sustains high productivity even under thelowest light intensties, minimizing shade-effects of plants• Fire – burned mats recover slowly, releasing and thenresorbing lost nutrients

Summary• Species inhabiting periphyton mats are adapted to theextreme and variable conditions of the Everglades

Unanswered questionsMany mechanistic experiments still needed to understand:• Why is there an inverse relationship of production and P?• How do bacteria and algae interact to increase nutrientcycling efficiency?• What is the mechanism of desiccation resistance (physicalstructures, species’ phenologies)?• How does variability in light quality and quantity withinmats facilitate production?• What happens with all that detritus?

Unanswered questionsWhere does all this production go?-Maybe the Everglades food webis detrital rather than algal-Maybe it is being respired bybacteria in the flocculent detritusand subsoils-Maybe it is being transporteddownstream as particulate anddissolved organic matter

AcknowledgementsFaculty: Jenny, Mike, Joel,Miro, Dan, Ron, Len…Funding: NSF FCE LTER, South Florida Water Management District,Everglades National Park, Florida DEP, US EPA