1. Seagrasses 2 Light, Eutrophication & Foodwebs = Why seagrasses are used to indicate coastal/estuarine system stability.

2. Light Limitation is the Principal Determinant of SAV Distribution

3. Light Environment Water causes light attenuation Due to: suspended particles (turbidity) and color (CDOM). Turbidity a fnt of phytoplankton and other “particles” (TSS) K = attenuation coefficient Beer-Lambert Law: I z = I o e -zK Msr with secchi disk or PAR sensors PAR vs PUR Z I

4. Light Limitation is the Principal Determinant of SAV Distribution Apparent Optical Properties vs Inherent OP’s AOP = Secchi depth (m) or attenuation coefficient (K d ) in 1/m K d (AOP) depends on inherent optical properties (IOP’s) IOP’s depend on water quality IOP’s are a based on absorption (a) and scattering (b) of water+TSS+color+chl a Radiative transfer modeling provides the link between AOP and IOP’s of the 3 components of attenuation (TSS + color + chl a) From this relationship a direct link between water quality and light available to SAV can be made. TSS AOPIOP

6. Eutrophication reduces light (phytoplankton and epiphytes), and increases sulfide-toxicity Eutrophication

7. WHY SEAGRASS ONLY FOUND IN SHALLOW WATER? 15-25% of Surface Light (Io)

9. Seagrass loss causes sediments to be resuspended. Sediment resuspension causes water quality to decline -> less light Less light means seagrasses are further prone to sulfide toxicity Results in ongoing losses of remaining seagrasses

10. Importance of WQ to SAV Conceptual Model (Virnstein et al. 2000) (TMDL) $$$

11. Food Webs

12. Fewer Critters if no GrassShrimp feed in Grassbeds

14. Reef Halos

15. Parrotfish and Surgeons

16. FLORIDA BAY 1997

17. Green-winged teal American wigeon Redheads Migrating waterfowl Important food source e.g. 5000 seeds in 1 duck Anatini (dabbling ducks) Aythyini (diving ducks) Cygnini (swans) CONSUMERS OF SAV

18. Eutrophication? + Nutrients BOTTOM-UP + algae/p’plankton - seagrass - light TOP-DOWN - mesograzers + small fish - pred fish Trophiccascade TROPHIC CASCADES: Jackson et al, Nature 2001 Heck and Valentine, JEMBE 2006

20. Top-down and bottom-up control

21. Why we are concerned

24. 3 papers to read William C. Dennison; Robert J. Orth; et al. 1993. Assessing Water Quality with Submersed Aquatic Vegetation BioScience, Vol. 43, pp. 86-94. Kenneth L. Heck Jr, John F. Valentine. 2006. Plant– herbivore interactions in seagrass meadows. Journal of Experimental Marine Biology and Ecology 330: 420– 436 Michelle Waycott, Carlos M. Duarte, et al. 2009. Accelerating loss of seagrasses across the globe threatens coastal ecosystems. Proceedings of the Natural Academy of Sciences (PNAS) vol. 106 pp. 12377–12381