Isotopic Perspectives on the Foundation of Estuarine Dependent Fish Biomass: Macrophytes Versus...
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Transcript of Isotopic Perspectives on the Foundation of Estuarine Dependent Fish Biomass: Macrophytes Versus...
Isotopic Perspectives on the Foundation of Estuarine Dependent Fish Biomass:
Macrophytes Versus Microphytes
David Hollander, Elon Malkin, Susan Murasko, Ernst Peebles
College of Marine Science
University of South Florida
St. Petersburg, FL 33701
Project Objective: Determine the key primary producer(s) that
support economically-important juvenile fish in SW Florida’s tidal rivers
Fishing in Southwest Florida: A Billion Dollar Industry
•Estuarine-Dependent Life–Adult’s spawn at coast–Larvae migrate to rivers–Juveniles occupy rivers
•Climatic & Human Impacts–SW Florida Hydrology •Wet vs. Dry Seasons
–Anthropogenic nutrient inputs •Oligotrophic vs. Eutrophic
Why do fish occupy tidal rivers?
Migration
Migration
Adults
Tidal RiversTidal Rivers
JuvenilesJuveniles
New Orleans
Coast
TampaBay
Gulf of Mexico
Larvae
•Abundant vascular plants occupy these habitats– Do these provide the basis of food-webs?
Tidal Rivers: Vegetated Nursery Habitats
•Juvenile Fish utilize vegetated tidal rivers as nurseries•Juvenile Fish eat benthic invertebrates (Gut Study)
Benthic Inverts.
Benthic invert. feeder
Juvenile
–What 1o producers support these ecosystems?
•Abundant vascular plants occupy these habitats– Do these provide the basis of food-webs?
Tidal Rivers: Vegetated Nursery Habitats
•Juvenile Fish utilize vegetated tidal rivers as nurseries•Juvenile Fish eat benthic invertebrates (Gut Study)
Benthic Inverts.
Benthic invert. feeder
Juvenile
–What 1o producers support these ecosystems?
Macrophytic food web?
?Vascular PlantsMacrophytes?
Abundant Vascular Plants (Macrophytes) may support food web
•Freshwater delivers nutrients to these habitats– Potential Changes to Nutrient Flows:
– Natural hydrology (Wet season Hi vs. Dry season Lo)– Anthropogenic nutrient loading (Oligotrophic vs. Eutro)
Tidal Rivers: Nutrient Flow
Nutrient Delivery
JuvenileInverts.
•Freshwater delivers nutrients to these habitats– Potential Changes to Nutrient Flows:
– Natural hydrology (Wet season Hi vs. Dry season Lo)– Anthropogenic nutrient loading (Oligotrophic vs. Eutro)
Tidal Rivers: Nutrient Flow
Nutrient Delivery
JuvenileInverts.
•Nutrient delivery supports microalgal blooms
MicroalgaeMicrophytes
•Freshwater delivers nutrients to these habitats– Potential Changes to Nutrient Flows:
– Natural hydrology (Wet season Hi vs. Dry season Lo)– Anthropogenic nutrient loading (Oligotrophic vs. Eutro)
Tidal Rivers: Nutrient Flow
Nutrient Delivery
JuvenileInverts.
•Nutrient delivery supports microalgal blooms
?MicroalgaeMicrophytes? Microphytic food web?
Microalgae (Microphytes) may support food web
Florida’s Tidal Rivers: 2 Potential Nutritional Influences
Watershed Plants
Macrophytes•Marshgrass•Mangroves•Upland tree detritus
Macrophyticfood web
Juvenile Fish Nursery
Florida’s Tidal Rivers: 2 Potential Nutritional Influences
Hydrology & Nutrient Driven
MicrophytesMicroalgae•Benthic Microalgae •Phytoplankton (POM)
Microphyticfood web
Watershed Plants
Macrophytes•Marshgrass•Mangroves•Upland tree detritus
Macrophyticfood web
Juvenile Fish Nursery
Florida’s Tidal Rivers: 2 Potential Nutritional Influences
MicrophytesMicroalgae•Benthic Microalgae •Phytoplankton (POM)
Microphyticfood web
Watershed Plants
Macrophytes•Marshgrass•Mangroves•Upland tree detritus
Macrophyticfood web
Which 1o producers support fish biomass in tidal rivers? Microphytes vs. Macrophytes?
Juvenile Fish Nursery
Hydrology & Nutrient Driven
Weeki wachee
Alafia
Myakka
CharlotteHarbor
Tampa Bay
Gulf OfMexico
Research Strategy
Field Studies•Ecosystem wide sampling during wet & dry season
–Vascular Plants, Microalgae, Fish
Weeki wachee
Alafia
Myakka
CharlotteHarbor
Tampa Bay
Gulf OfMexico
Research Strategy
Field Studies•Ecosystem wide sampling during wet & dry season
–Vascular Plants, Microalgae, Fish
•3 Rivers with variable nutrient states
EutrophicOligotrophic
AlafiaMyakkaWwachee
Weeki wachee
Alafia
Myakka
CharlotteHarbor
Tampa Bay
Gulf OfMexico
Research Strategy
Field Studies•Ecosystem wide sampling during wet & dry season
–Vascular Plants, Microalgae, Fish
•3 Rivers with variable nutrient states
EutrophicOligotrophic
AlafiaMyakkaWwachee
Analytical Approach•Stable isotopes of organic C, N, S
–Reflects trophic relationships & nutrient sources
Weeki wachee
Alafia
Myakka
CharlotteHarbor
Tampa Bay
Gulf OfMexico
Research Strategy
Field Studies•Ecosystem wide sampling during wet & dry season
–Vascular Plants, Microalgae, Fish
•3 Rivers with variable nutrient states
EutrophicOligotrophic
AlafiaMyakkaWwachee
Which 1o producers support fish biomass in tidal rivers? Microphytes vs. Macrophytes?
Analytical Approach•Stable isotopes of organic C, N, S
–Reflects trophic relationships & nutrient sources
Mesotrophic Myakka: Wet Season
-5-3-113579111315
δ15N
,
‰ A
IR
6N:2C
FishRed Drum
Mojarra
Silverside
Sand Seatrout
-35 -30 -25 -20 -15δ13 C, ‰ PDB
-5-3-113579111315
•Macrophyte δ13C range constrained vs. Fish
6N:2C
δ15N
,
‰ A
IRMacroMangroves
Marshgrass
Upland Trees
-35 -30 -25 -20 -15δ13 C, ‰ PDB
Mesotrophic Myakka: Wet Season
-5-3-113579111315
-35 -30 -25 -20 -15
•POM covers δ13C range of Fish•POM supports Fish in the Wet Season
δ15N
,
‰ A
IR
δ13 C, ‰ PDB
6N:2C
MicroPOM
BMA
Mesotrophic Myakka: Wet Season
-5-3-113579111315
δ15N
,
‰ A
IR
6N:2C
FishRed DrumMojarraSilversideSand SeatroutSpotted StroutMulletSpot
-35 -30 -25 -20 -15δ13 C, ‰ PDB
Mesotrophic Myakka: Dry Season
-5-3-113579111315
•Macrophytes may contribute to some Fish
δ15N
,
‰ A
IR
6N:2C
MacroMangroves
Marshgrass
Upland Trees
-35 -30 -25 -20 -15δ13 C, ‰ PDB
Mesotrophic Myakka: Dry Season
-5-3-113579111315
s
•BMA may contribute to some Fish
δ15N
,
‰ A
IR
6N:2C
MicroPOM
BMA
-35 -30 -25 -20 -15δ13 C, ‰ PDB
Mesotrophic Myakka: Dry Season
•BMA & Macrophytes both seem to contribute to fish•Third tracer needed
6N:2C
s
Micro
MacroMangroves
Marshgrass
Fish
-35 -30 -25 -20 -15δ13 C, ‰ PDB
-5-3-113579111315
δ15N
,
‰ A
IR Mesotrophic Myakka: Dry Season
POM
BMA
Mesotrophic Myakka: Dry Season Sulfur
-5-3-113579111315
3 8 13 18
s
•Sulfur data distinguishes between BMA & Macrophytes•BMA supports Fish in the Dry season
δ15N
,
‰ A
IR
6N:0S
MojarraSilversideSpotted Strout
Micro
MacroBMA
MangrovesMarshgrass
δ34 S, ‰ CDT
Fish
Conclusion: Microalgae Support Juvenile Fish Biomass
Benthic Deposit Feeders
Invert Feeders
Juvenile Fish
•Fish and Inverts do not change feeding behavior
Conclusion: Microalgae Support Juvenile Fish Biomass
•Fish and Inverts do not change feeding behavior
Benthic Deposit Feeders
Invert Feeders
Juvenile Fish
Wet Season Nutrient Delivery ON
POM BLOOM
POM DominatedSediments
DepositionalSystem
Conclusion: Microalgae Support Juvenile Fish Biomass
Benthic Deposit Feeders
Invert Feeders
Juvenile Fish
Dry Season Nutrient Delivery OFF
BMA DominatedSediments
POM BLOOM
Benthic Nutrients
•Fish and Inverts do not change feeding behavior
Conclusion: Microalgae Support Juvenile Fish Biomass
Benthic Deposit Feeders
Invert Feeders
Juvenile Fish
Wet Season Nutrient Delivery ON
POM BLOOM
POM DominatedSediments
DepositionalSystem
Dry Season Nutrient Delivery OFF
BMA DominatedSediments
POM BLOOM
Benthic Nutrients
•Fish and Inverts do not change feeding behavior
Mesotrophic vs. Oligotrophic Rivers
Mesotrophic Myakka
•Moderate nutrient delivery during wet season
–POM supports Fish
Mesotrophic vs. Oligotrophic Rivers
•Moderate nutrient delivery during wet season
–POM supports Fish
Mesotrophic Myakka Oligotrophic Weeki wachee
•Low nutrient delivery during wet season
–What supports Fish?
•What 1o producers support Fish in oligotrophic systems?
Oligotrophic Weeki wachee:
δ13 C, ‰ PDB
Mesotrophic Oligotrophic-3-113579111315
-5-35 -30 -25 -20
-3-113579111315
-5-35 -30 -25 -20
δ15N
,
‰ A
IROligotrophic Rivers: POM Deposition OFF
Myakka Wet Season Wwachee Wet Season
Oligotrophic Weeki wachee:
δ13 C, ‰ PDB
Mesotrophic Oligotrophic-3-113579111315
-5-35 -30 -25 -20
-3-113579111315
-5-35 -30 -25 -20
δ15N
,
‰ A
IR
•Less Fish catches during sampling (Myakka 3X)
Fish
Oligotrophic Rivers: POM Deposition OFF
Myakka Wet Season Wwachee Wet Season
Oligotrophic Rivers: POM Deposition OFF
Oligotrophic Weeki wachee:
Myakka Wet Season Wwachee Wet Season
δ13 C, ‰ PDB
Mesotrophic Oligotrophic-3-113579111315
-5-35 -30 -25 -20
-3-113579111315
-5-35 -30 -25 -20
δ15N
,
‰ A
IR
•Less Fish catches during sampling (Myakka 3X)•Not enough nutrients for sig. wet season phytoplanktic algal blooms•Only partial POM contribution; BMA supports fish in wet season
Micro Fish
POM
BMA
Conclusions & Implications•Microalgae support juvenile fish in tidal rivers
–POM supports Fish during wet season (freshwater nutrient flow)
–BMA supports Fish during dry season (access to benthic nutrients)
•Ecosystem-wide stable isotopes & Management
–Quantifies ecology; supports mathmatical models
–Stronger than species-specific studies; supports NOAA’s future goals
–Links Ecology to biogeochemistry of ecosystems