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 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 Adults Tidal Rivers Juveniles New Orleans Coast Tampa Bay 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 1 o 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 1 o producers support these ecosystems? Macrophytic food web? ?Vascular Plants Macrophytes? 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 Microalgae Microphytes

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 ?Microalgae Microphytes? Microphytic food web? Microalgae (Microphytes) may support food web

Florida’s Tidal Rivers: 2 Potential Nutritional Influences Juvenile Fish Nursery

Florida’s Tidal Rivers: 2 Potential Nutritional Influences Watershed Plants Macrophytes Marshgrass Mangroves Upland tree detritus Macrophytic food web Juvenile Fish Nursery

Florida’s Tidal Rivers: 2 Potential Nutritional Influences Hydrology & Nutrient Driven Microphytes Microalgae Benthic Microalgae Phytoplankton (POM) Microphytic food web Watershed Plants Macrophytes Marshgrass Mangroves Upland tree detritus Macrophytic food web Juvenile Fish Nursery

Florida’s Tidal Rivers: 2 Potential Nutritional Influences Microphytes Microalgae Benthic Microalgae Phytoplankton (POM) Microphytic food web Watershed Plants Macrophytes Marshgrass Mangroves Upland tree detritus Macrophytic food web Which 1 o producers support fish biomass in tidal rivers? Microphytes vs. Macrophytes? Juvenile Fish Nursery Hydrology & Nutrient Driven

Weeki wachee Alafia Myakka Charlotte Harbor Tampa Bay Gulf Of Mexico Research Strategy Field Studies Ecosystem wide sampling during wet & dry season –Vascular Plants, Microalgae, Fish

Weeki wachee Alafia Myakka Charlotte Harbor Tampa Bay Gulf Of Mexico 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 Charlotte Harbor Tampa Bay Gulf Of Mexico 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 Charlotte Harbor Tampa Bay Gulf Of Mexico Research Strategy Field Studies Ecosystem wide sampling during wet & dry season –Vascular Plants, Microalgae, Fish 3 Rivers with variable nutrient states EutrophicOligotrophic AlafiaMyakkaWwachee Which 1 o 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

δ 15 N, ‰ AIR 6N:2C Fish Red Drum Mojarra Silverside Sand Seatrout δ 13 C, ‰ PDB

Macrophyte δ 13 C range constrained vs. Fish 6N:2C δ 15 N, ‰ AIR Macro Mangroves Marshgrass Upland Trees δ 13 C, ‰ PDB Mesotrophic Myakka: Wet Season

POM covers δ 13 C range of Fish POM supports Fish in the Wet Season δ 15 N, ‰ AIR δ 13 C, ‰ PDB 6N:2C Micro POM BMA Mesotrophic Myakka: Wet Season

Mesotrophic Myakka: Dry Season

δ 15 N, ‰ AIR 6N:2C Fish Red Drum Mojarra Silverside Sand Seatrout Spotted Strout Mullet Spot δ 13 C, ‰ PDB Mesotrophic Myakka: Dry Season

Macrophytes may contribute to some Fish δ 15 N, ‰ AIR 6N:2C Macro Mangroves Marshgrass Upland Trees δ 13 C, ‰ PDB Mesotrophic Myakka: Dry Season

s BMA may contribute to some Fish δ 15 N, ‰ AIR 6N:2C Micro POM BMA δ 13 C, ‰ PDB Mesotrophic Myakka: Dry Season

BMA & Macrophytes both seem to contribute to fish Third tracer needed 6N:2C s Micro Macro Mangroves Marshgrass Fish δ 13 C, ‰ PDB δ 15 N, ‰ AIR Mesotrophic Myakka: Dry Season POM BMA

Mesotrophic Myakka: Dry Season Sulfur s Sulfur data distinguishes between BMA & Macrophytes BMA supports Fish in the Dry season δ 15 N, ‰ AIR 6N:0S Mojarra Silverside Spotted Strout Micro Macro BMA Mangroves Marshgrass δ 34 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 Dominated Sediments Depositional System

Conclusion: Microalgae Support Juvenile Fish Biomass Benthic Deposit Feeders Invert Feeders Juvenile Fish Dry Season Nutrient Delivery OFF BMA Dominated Sediments 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 Dominated Sediments Depositional System Dry Season Nutrient Delivery OFF BMA Dominated Sediments 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 1 o producers support Fish in oligotrophic systems?

Oligotrophic Weeki wachee: δ 13 C, ‰ PDB MesotrophicOligotrophic δ 15 N, ‰ AIR Oligotrophic Rivers: POM Deposition OFF Myakka Wet Season Wwachee Wet Season

Oligotrophic Weeki wachee: δ 13 C, ‰ PDB MesotrophicOligotrophic δ 15 N, ‰ AIR 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 δ 13 C, ‰ PDB MesotrophicOligotrophic δ 15 N, ‰ AIR 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