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Workshop Objectives

Workshop Objectives. A better understanding of the relationships between nutrients and aquatic communities Some context around what makes a “Quality” Florida Lake A summary and interpretation of LakeWatch Data and Soils Data.

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Workshop Objectives

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  1. Workshop Objectives • A better understanding of the relationships between nutrients and aquatic communities • Some context around what makes a “Quality” Florida Lake • A summary and interpretation of LakeWatch Data and Soils Data. • A summary of what and why various alternative management strategies are being implemented in some of the stormwater ponds at Grand Haven and a request for volunteers.

  2. Agenda • Presentation - Aquatic Ecology 101 • Video - What Makes a Quality Lake? • Break • Presentation - Watershed Connections • Data summary – LakeWatch Data • Data Summary - Soils Data • Presentation – Alternative management practices and why they are being evaluated • Monitoring plan

  3. Aquatic Ecology 101 Mark Clark Extension Specialist Wetlands and Water Quality Soil and Water Science Department University of Florida

  4. Outline • Types of aquatic ecosystems • Hydrology of lakes and ponds • Lake zones and processes • Aquatic food web • Lake trophic states • Concept of limiting nutrient

  5. Types of Aquatic Systems Rivers & Streams Lakes & Ponds Wetlands Estuaries Groundwater Marine system

  6. Lakes and Ponds • Critical differences from other freshwater systems • Longer residence time • Typically not shaded with most of the surface area exposed to sunlight • Florida lakes are typically shallow and well mixed • Florida lakes are often highly colored, but can have light reaching much of the bottom Photo by Bill Wade

  7. Watershed / Lake Area Ratio • Watershed area relative to lake area will influence the residence time of water in the lake. • This ratio is also a factor in the nutrient loading to the lake

  8. Lake Habitat Zones

  9. Lake Littoral Zone • Functions • Intercepts Nutrients • Refuge from Predators • Nursery for Fish Oligotrophic Northern Lake Eutrophic Southern Lake

  10. Lake Limnetic/Pelagic Zone • Functions • Plankton • Zooplankton

  11. Lake Limnetic / Pelagic Zone • Submerged Aquatic Vegetation (SAV) • Nutrient uptake • Sediment stabilization • Habitat • Oxygen production

  12. Pond Food Web Algae/Plants Fish Nutrients Grazers Nutrients Algae/Plants Grazers Fish

  13. Fish Algae/Plants Grazers Algae/Plants Grazers Fish Algae/Plants Grazers Fish Algae/Plants Grazers Fish Relationship Between Nutrients and Pond Productivity Nutrients Nutrients Nutrients Algae/Plants Grazers Fish Nutrients Nutrients Habitat/Environmental Impacts

  14. Low nutrients Low primary productivity Low grazers and insects Low fish production Clear water Sandy/low organic matter on bottom

  15. Moderate nutrients Increased primary productivity More grazers and insects More fish production Moderate water clarity More aquatic plants Some organic sediment accumulation TROPHIC STATE

  16. High nutrients High primary productivity Large number of grazers and insects Moderate fish production Low water clarity, or Clear with aquatic plants High organic sediment accumulation TROPHIC STATE

  17. Trophic State Change • Nutrients & Productivity • Sediment & Accumulation • Species Shifts • Species Richness

  18. Source of the problem Manipulating Pond Response to Nutrients X X Nutrients Algae/Plants Grazers Fish Algae/Plants Grazers Fish

  19. Limiting Nutrient Concept …Plants need nutrients to grow • Nitrogen and Phosphorus are the main nutrients • For every unit of N you need so many units of P • If one nutrient is not in sufficient supply it will limit the total production potential. • For algae • N:P > 17 Phosphorus Limited • N:P < 10 Nitrogen Limited • 10 < N:P < 17 Co-Limitation • N:P < 22 will tend to promote Cyanobacteria which are nitrogen fixers

  20. Phosphorus Limitation: Lake 227

  21. Total Phosphorus / Chlorophyll-a Relationship • Phosphorus is typically liming nutrient in freshwater • Nitrogen is typically limiting nutrient in marine system.

  22. Summary • Lakes have longer residence time and more light than other freshwater systems • Littoral Zone, Pelagic Zone, Submerged Aquatic Vegetation • Nutrients regulate algae > grazers > fish • Removing algae doesn’t remove nutrient regulator • Phosphorus is typical nutrient limiting nutrients depending on N:P ratio Stormwater ponds respond just like lakes do to nutrients

  23. Questions?

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