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Michael Chislock, Kristin Adamson, Jim Stoeckel, and Alan Wilson Department of Fisheries and Allied Aquacultures Auburn

Plankton Community Dynamics near the Saugahatchee Creek Embayment: Variable Effects of Phosphorus Loading and Zooplankton Grazers on Algal Abundance. Michael Chislock, Kristin Adamson, Jim Stoeckel, and Alan Wilson Department of Fisheries and Allied Aquacultures Auburn University.

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Michael Chislock, Kristin Adamson, Jim Stoeckel, and Alan Wilson Department of Fisheries and Allied Aquacultures Auburn

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  1. Plankton Community Dynamics near the Saugahatchee Creek Embayment: Variable Effects of Phosphorus Loading and Zooplankton Grazers on Algal Abundance Michael Chislock, Kristin Adamson, Jim Stoeckel, and Alan Wilson Department of Fisheries and Allied Aquacultures Auburn University

  2. Acknowledgments AL Power – for allowing us to access their house during experiment set-ups. Kiunte Dowdell, Reni Kaul, Erin Cash, and Sean Maher assisted with field work in all weather conditions. This project was funded by an Auburn University Water Center grant and a Sigma Xi Grant-in-Aid of Research. Jacaris (for assisting last summer, drinking/eating Daphnia when I told him to, and losing my Rat-l-traps in the stumps) Reni – for getting in the boat … with Al driving Key – for helping out in the hot weather (and for taking a dive in the pond during “the mudfight”) Wilson Lab at Auburn University (www.wilsonlab.com)

  3. Background Threats to Reservoir Systems Nutrient enrichment Invasive/non-native species

  4. Background Sedimentation & Nutrient Loading Threats to Reservoir Systems Sediment and phosphorus pulses from Saugahatchee Creek  algal blooms? Mudline/Sediment plume

  5. Project Overview Central Aims - To understand how pulses of nutrients, sediments, and grazers influence plankton communities in reservoirs - How does upstream nutrient loading in Saugahatchee Creek impact plankton abundance in Yates Lake (and do these effects vary seasonally)? Outline Site Info and Background Experimental Design Development Seasonal Experiments

  6. Sampling Sites Tallapoosa Upst Saugahatchee AL Power Boat Dock

  7. Sampling Sites Experimental Sites Saugahatchee Creek Tallapoosa Upst

  8. Sampling Sites Experimental Sites Tallapoosa Upst Saugahatchee

  9. General experimental design Goals: (1) To determine effects of nutrient pulses and grazers on phytoplankton (2) To test whether these effects vary across sites and seasonally Methodology 2 nutrient treatments (ambient; 2X seasonal maximum phosphorus) × 2 grazer treatments (grazer; no grazer) × 2 sites (Saug embayment; Yates Lake – embayment above Saug input) -3 replicates/treatment combination at each site -200 μg L-1 = target total phosphorus -2X ambient zooplankton density for grazer treatment (80 µm mesh) Mesocosms attached to PVC frames – 44 gallon Rubbermaid Brute trash can enclosures or 6.5 gallon buckets Short-term experiments

  10. Hypothesis – Completely Conceived Results Importance of bottom-up vs top-down effects

  11. Effects of Enclosure Size Packing Up Buckets vs Cans

  12. Pilot Experiment – Effects of Scale (Buckets vs Cans) Key Results – 44 gallon trash cans • Significant effect of fertilization and grazer treatments in cans • Treatment effects much stronger after 2 weeks • Rank order of treatments as predicted • Key Results – 6.5 gallon buckets • Significant effect of grazer treatments only after 2 weeks • Data much less ‘clean’ than cans • Fertilized/grazer mean substantially lower than ambient/grazer -lots of settled algae in shallow buckets

  13. Demonic intrusion (Hurlbert, S.H., 1984. Pseudoreplication and the design of ecological field experiments. Ecological Monographs 54:187-211)

  14. Demonic intrusion (Hurlbert, S.H., 1984. Pseudoreplication and the design of ecological field experiments. Ecological Monographs 54:187-211) Elevated N

  15. Seasonal experiments design Goals: (1) To determine effects of nutrient pulses and grazers on phytoplankton (2) To test whether these effects vary across sites and seasonally Methodology 2 nutrient treatments (ambient; 2X seasonal maximum phosphorus) × 2 grazer treatments (grazer; no grazer) × 2 sites (Saug embayment; Yates Lake – embayment above Saug input) -3 replicates/treatment combination at each site -200 μg L-1 = target total phosphorus -2X ambient zooplankton density for grazer treatment (80 µm mesh) 44 gallon trash can enclosures 1 week = duration of experiment

  16. Winter Experiment (December)Total phosphorus Experimental Sites Initial Nutrient Levels Initial Nutrient Levels

  17. Winter Experiment (December)Chlorophyll -Significant phosphorus effect on Tallapoosa -No grazer effect at either site -Lack of a phosphorus effect on Saug likely a result of limited light availability and cold water temp -Initial grazer density = 2X ambient  cool temperatures and short duration of experiment

  18. Spring Experiment (March) -Only significant treatment effect = grazer effect on Saug -Turbid conditions at both sites

  19. Conclusions -Tremendous amount of variation in effects across space and time -Sediment loading is an important water quality issue near the Saug embayment, with clear effects on algal productivity -c.f., Coosa River System (cyanobacterial blooms, very high productivity) -Future plans for this project – submit results to peer-reviewed publication this spring

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