1. NOAA Coral Reef Watch Elevated nutrients The Reefs are Changing

3. 1959 1988 1998 Photos by Gene Shinn (USGS) What does it look like?

4. Balance in the Reef Corals  Structure Algae  fix inorganic material (C; N) Fish keep algae in check

5. A “Healthy” Reef St. John USVI - Dennis Hubbard Zooxanthellae Maricopa Community College Zooxanthellae live in coral tissue photosynthesize need light provide “food” for corals Background: see http://serc.carleton.edu/eslabs/corals/index.html

6. A “Unhealthy” Reef Grand Bahama Island Dennis Hubbard St. Thomas USVI – Dennis Hubbard To many algae: elevated nutrients too few fish shade out corals block larval settlement

7. Classifying Impacts Top Down Bottom Up

8. Fish & Urchins graze on algae Keep reef surface “clean” algae shade corals (light) algae take up space (recruitment) Problems: Overfishing Diseases (urchins) St. John USVI – Dennis Hubbard

10. Classifying Impacts Top Down Bottom Up

11. This leads to This

12. In the Caribbean……

13. The “Healthy” Reef

14. From this……

15. to this!! too few fish too many nutrients both

16. Conceptual Model Mathematical Model

17. CoralReefs in Netlogo Mathematical Simulation Free Runs on both Mac and PC

18. CoralReefs in Netlogo Download & Install Program: http://ccl.northwestern.edu/netlogo/download.shtml Download Model: CoralReefs-V5.1.nlogo Your instructor will give you a location Double-click model file to start (see Handout 2)