Isotopic Perspectives on the Foundation of

1

• 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 Floridas tidal rivers

2
Fishing in Southwest Florida A Billion Dollar
Industry
New Orleans
Gulf of Mexico
Tidal Rivers

• Estuarine-Dependent Life
• Adults 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

Migration
Coast
Tampa Bay
Juveniles
Larvae
Adults
Why do fish occupy tidal rivers?
3
Tidal Rivers Vegetated Nursery Habitats

• Abundant vascular plants occupy these habitats
• Do these provide the basis of food-webs?

• Juvenile Fish utilize vegetated tidal rivers as
  nurseries
• Juvenile Fish eat benthic invertebrates (Gut
  Study)

• What 1o producers support these ecosystems?

Benthic Inverts.
Juvenile
Benthic invert. feeder
4
Tidal Rivers Vegetated Nursery Habitats

• Abundant vascular plants occupy these habitats
• Do these provide the basis of food-webs?

• Juvenile Fish utilize vegetated tidal rivers as
  nurseries
• Juvenile Fish eat benthic invertebrates (Gut
  Study)

• What 1o producers support these ecosystems?

Benthic Inverts.
Juvenile
Benthic invert. feeder
5
Tidal Rivers Nutrient Flow

• 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)

Nutrient Delivery
Juvenile
Inverts.
6
Tidal Rivers Nutrient Flow

• 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)

Nutrient Delivery
Juvenile
Inverts.
7
Tidal Rivers Nutrient Flow

• 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)

Nutrient Delivery
Juvenile
Inverts.
8
Floridas Tidal Rivers 2 Potential Nutritional
Influences
9
Floridas Tidal Rivers 2 Potential Nutritional
Influences
10
Floridas Tidal Rivers 2 Potential Nutritional
Influences
Hydrology Nutrient Driven

• Microphytes
• Microalgae
• Benthic Microalgae
• Phytoplankton (POM)

Microphytic food web
11
Floridas Tidal Rivers 2 Potential Nutritional
Influences
Hydrology Nutrient Driven

• Microphytes
• Microalgae
• Benthic Microalgae
• Phytoplankton (POM)

Microphytic food web
Which 1o producers support fish biomass in tidal
rivers? Microphytes vs. Macrophytes?
12
Research Strategy

• Field Studies
• Ecosystem wide sampling during wet dry season
• Vascular Plants, Microalgae, Fish

13
Research Strategy

• Field Studies
• Ecosystem wide sampling during wet dry season
• Vascular Plants, Microalgae, Fish
• 3 Rivers with variable nutrient states

14
Research Strategy

• Field Studies
• Ecosystem wide sampling during wet dry season
• Vascular Plants, Microalgae, Fish
• 3 Rivers with variable nutrient states

• Analytical Approach
• Stable isotopes of organic C, N, S
• Reflects trophic relationships nutrient sources

15
Research Strategy

• Field Studies
• Ecosystem wide sampling during wet dry season
• Vascular Plants, Microalgae, Fish
• 3 Rivers with variable nutrient states

• Analytical Approach
• Stable isotopes of organic C, N, S
• Reflects trophic relationships nutrient sources

Which 1o producers support fish biomass in tidal
rivers? Microphytes vs. Macrophytes?
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Mesotrophic Myakka Wet Season
17
Mesotrophic Myakka Wet Season
15
13
11
9
d15N, AIR
7
5
3
1
-1
-3
6N2C
d13C, PDB
-5
-35
-30
-25
-20
-15
18
Mesotrophic Myakka Wet Season
15
13
11
9
d15N, AIR
7
5
3
1
-1
-3
6N2C
d13C, PDB
-5
-35
-30
-25
-20
-15

• Macrophyte d13C range constrained vs. Fish

19
Mesotrophic Myakka Wet Season
15
13
11
9
d15N, AIR
7
5
3
1
-1
-3
6N2C
d13C, PDB
-5
-35
-30
-25
-20
-15

• POM covers d13C range of Fish
• POM supports Fish in the Wet Season

20
Mesotrophic Myakka Dry Season
21
Mesotrophic Myakka Dry Season
Fish
15
Red Drum Mojarra Silverside Sand Seatrout Spotted
Strout Mullet Spot
13
11
9
d15N, AIR
7
5
3
1
-1
-3
6N2C
d13C, PDB
-5
-35
-30
-25
-20
-15
22
Mesotrophic Myakka Dry Season
Macro
15
Mangroves Marshgrass Upland Trees
13
11
9
d15N, AIR
7
5
3
1
-1
-3
6N2C
d13C, PDB
-5
-35
-30
-25
-20
-15

• Macrophytes may contribute to some Fish

23
Mesotrophic Myakka Dry Season
Micro
15
POM BMA
13
11
9
d15N, AIR
7
5
3
s
1
-1
-3
6N2C
d13C, PDB
-5
-35
-30
-25
-20
-15

• BMA may contribute to some Fish

24
Mesotrophic Myakka Dry Season
Fish
15
Micro
13
POM BMA
11
9
d15N, AIR
Macro
7
Mangroves Marshgrass
5
3
s
1
-1
-3
6N2C
d13C, PDB
-5
-35
-30
-25
-20
-15

• BMA Macrophytes both seem to contribute to fish
• Third tracer needed

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Mesotrophic Myakka Dry Season Sulfur
Fish
15
Mojarra Silverside Spotted Strout
13
11
Micro
9
d15N, AIR
BMA
7
Macro
5
Mangroves Marshgrass
3
s
1
-1
-3
6N0S
d34S, CDT
-5
3
8
13
18

• Sulfur data distinguishes between BMA
  Macrophytes
• BMA supports Fish in the Dry season

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Conclusion
Microalgae Support Juvenile Fish
Biomass

• Fish and Inverts do not change feeding behavior

Benthic Deposit Feeders
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Conclusion
Microalgae Support Juvenile Fish
Biomass

• Fish and Inverts do not change feeding behavior

Benthic Deposit Feeders
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Conclusion
Microalgae Support Juvenile Fish
Biomass

• Fish and Inverts do not change feeding behavior

POM BLOOM
Benthic Nutrients
BMA Dominated Sediments
Benthic Deposit Feeders
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Conclusion
Microalgae Support Juvenile Fish
Biomass

• Fish and Inverts do not change feeding behavior

POM BLOOM
POM BLOOM
Depositional System
Benthic Nutrients
POM Dominated Sediments
BMA Dominated Sediments
Benthic Deposit Feeders
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Mesotrophic vs. Oligotrophic Rivers
Mesotrophic Myakka

• Moderate nutrient delivery during wet season
• POM supports Fish

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Mesotrophic vs. Oligotrophic Rivers
Mesotrophic Myakka
Oligotrophic Weeki wachee

• Moderate nutrient delivery during wet season
• POM supports Fish

• Low nutrient delivery during wet season
• What supports Fish?

• What 1o producers support Fish in oligotrophic
  systems?

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Oligotrophic Rivers POM Deposition OFF
Myakka Wet Season
Wwachee Wet Season
15
15
13
13
11
11
9
d15N, AIR
9
7
7
5
5
3
3
1
1
-1
-1
Mesotrophic
Oligotrophic
-3
-3
d13C, PDB
-5
-35
-30
-25
-20
Oligotrophic Weeki wachee
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Oligotrophic Rivers POM Deposition OFF
Myakka Wet Season
Wwachee Wet Season
15
15
13
13
11
11
9
d15N, AIR
9
7
7
5
5
Fish
3
3
1
1
-1
-1
Mesotrophic
Oligotrophic
-3
-3
d13C, PDB
-5
-35
-30
-25
-20
Oligotrophic Weeki wachee

• Less Fish catches during sampling (Myakka 3X)

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Oligotrophic Rivers POM Deposition OFF
Myakka Wet Season
Wwachee Wet Season
15
15
13
13
11
11
9
d15N, AIR
9
7
7
5
5
Fish
3
3
Micro
1
1
-1
-1
POM BMA
Mesotrophic
Oligotrophic
-3
-3
d13C, PDB
-5
-35
-30
-25
-20
Oligotrophic Weeki wachee

• Less Fish catches during sampling (Myakka 3X)

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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
  NOAAs future goals
• Links Ecology to biogeochemistry of ecosystems