1. Ecological Effects of Potential Minimum Flows and Levels for Florida Bay David Rudnick 1, Melody Hunt 1, Christopher Madden 1, Robin Bennett 1, Amanda McDonald 1, and Joel VanArman 2 1 Coastal Ecosystems Division and 2 Planning and Resource Evaluation Division South Florida Water Management District

3. Fresh water flow: Limited management control (Tamiami Trail, L31, C111) FL Bay inflow diffuse (mostly via creeks into northeast bay)

4. MFL Analysis Approach Resource - based using SAV in Transition Zone ponds. Identify salinity threshold for significant harm to SAV indicator species Determine concurrent salinity impacts along gradient from Transition Zone into NE Florida Bay

5. Evaluation Components  Hydrologic Analyses: Relationships among levels, flows, and salinity  Literature Review: Salinity effects on SAV species, major fish and invertebrate species  SAV Analyses: Statistical analysis of transition zone and FL Bay SAV and salinity Experiments on major SAV species (salinity tolerance and physiological response) Dynamic modeling of SAV (Halodule and Thalassia)  Fish and Invertebrate Analyses: Statistical modeling of higher trophic level species and forage fish assemblage

6. Hydrologic Models: Regression models Mass balance models Products: Water Budgets Sensitivity to managed flow Analysis of alternatives Hydrologic Analyses

7. Correlation of Annual Maximum Salinity with Annual Rainfall and Flow

8. Fresh Water Flow (1970 - 2000) Fresh water flow to NE Florida Bay Flow (thousands acre-feet)

9. Estimated salinity in Upper Taylor River Pond Jan Dec 2002 1970 > 50 ppt 40 – 50 ppt 30 – 40 ppt 20 – 30 ppt 10 – 20 ppt 0 – 10 ppt Black boxes: at least two consecutive years > 30 ppt

10. Estimated salinity in Little Madeira Bay > 50 ppt 40 – 50 ppt 30 – 40 ppt 20 – 30 ppt 10 – 20 ppt 0 – 10 ppt 2002 1970 Jan Dec Black boxes: when Transition Zone with at least two consecutive years > 30 ppt

11. Ecological Analyses Transition zone SAV: salinity response Florida Bay SAV: salinity response Florida Bay higher trophic level: salinity and habitat response

12. SAV as an Ecological Indicator Ecological Value –Habitat –Sediment Stability –Water Quality Benefits –Food Source Fresh water and brackish species sensitive to flow History of use and acceptance Ruppia maritima (widgeon grass)

13. When salinity > 30 ppt, SAV habitat almost absent from National Audubon Soc (Frezza and Lorenz) Transition Zone SAV Cover and Salinity

14. Salinity effects on Ruppia reproductive success Literature indicates failure at > 30 ppt (Kantrud 1991) Koch & Dawes experiment: no seed germination at 30 ppt, slow at 15 ppt Durako & Koch experiment on FL Bay seeds (below): no germination > 30 ppt from Durako and Koch 2005 Salinity (ppt)

15. Everglades-Florida Bay Gradient: Modeled SAV Response Little Madeira BayEagle Key Basin Dual species model results indicate decreasing Halodule at > 30 ppt

16. Higher Trophic Level Evaluation Statistical model developed from comprehensive Florida Bay database (20 species, 25 years) Results show high salinity (>40 ppt) results in decreased fish and invertebrates because of salinity stress and Halodule loss.

17. Conclusions:  Ruppia proposed as an indicator When salinity > 30 ppt, Ruppia typically absent and reproductive failure likely When Ruppia absent, SAV habitat lost  When salinity 30 ppt in transition zone, salinity is near 40 ppt in northeastern FL Bay  SAV model results indicate Halodule loss in northeast Bay near 40 ppt  Higher trophic level statistical models indicate hypersalinity and habitat quality effects  Protection of Ruppia also protects transition zone and northeastern Florida Bay resources (SAV habitat and fauna)

18. Photo by Pam Winegar