NOAA Coral Reef Watch Elevated nutrients The Reefs are Changing.

NOAA Coral Reef Watch

NOAA Coral Reef Watch Elevated nutrients

The Reefs are Changing

1959

1988

1998

Photos by Gene Shinn (USGS)

What does it look like?

Balance in the Reef

Corals StructureAlgae fix inorganic material (C; N)Fish keep algae in check

A “Healthy” Reef

St. John USVI - Dennis Hubbard

ZooxanthellaeMaricopa Community College

Zooxanthellae•live in coral tissue•photosynthesize•need light•provide “food” for corals

Background: see http://serc.carleton.edu/eslabs/corals/index.html

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

Classifying Impacts

• Top Down• Bottom Up

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

Classifying Impacts

• Top Down• Bottom Up

This

leads to

This

In the Caribbean……

The “Healthy” Reef

From this……

to this!!

• too few fish• too many nutrients• both

ConceptualModel

MathematicalModel

CoralReefs in Netlogo

• Mathematical Simulation• Free• Runs on both Mac and PC

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 locationDouble-click model file to start (see Handout 2)