STUDENT INSTRUCTIONS

To examine Figs. 1A and 1B,

* Turn to your neighbor and take 5 minutes to first describe and then interpret the data. Use the Step One - Step Two approach we have practiced in class. Be prepared to volunteer or be called on during our discussion.

* In Step One you first understand how the figure or table is set up (e.g. what the labels on the axes mean). You also need to have a pretty good idea of the experimental design - the question the scientists were asking and how they went about addressing it. Carefully describe the overall pattern in the data as well. In Step Two you can go on and attempt to interpret the data. For both steps write down any questions you have.

Some information about this study:

The only coral reef community in the continental US is in the waters off the southern tip of Florida. Stretching for more than 200 miles, the Florida Keys and Florida Bay contain a mosaic of seagrass beds and corals with mangrove forests at the coastal edge. During the late 1980's and into the 1990's noticeable changes occurred in the Florida Keys area. In the reef live coal coverage decreased and the corals were plagued with several diseases, some not seen before.

Most researchers have looked to the Florida Bay watershed as the source of these problems. For decades freshwater flow from the Everglades into Florida Bay has been greatly changed; water has been diverted, retained, and polluted with herbicides and other agricultural chemicals. As a result of water diversions and also droughts, salinity in parts of the Bay has been reported to be as high as 70ppt (seawater is about 30 ppt). Another likely reason is increased nutrient inputs (mainly from agriculture, sewage, and septic systems) to the Bay. Nutrients (mainly nitrogen and phosphorus) stimulate the growth of phytoplankton (floating microscopic plants) in the water. The result is very turbid water which shades the corals (they need light to grow). In addition, when the phytoplankton die and sink to the bottom of the bay, waters can become anoxic (no oxygen) because bacteria use up oxygen when they consume all this organic matter.

The EPA conducted this study from 1996-2000 in the Florida Keys National Marine Sanctuary. The data in Figs. 1 A and B are from permanent underwater stations in the Upper, Middle, and Lower Keys in Florida Bay. To get the coral diversity data (Fig. 1A), divers counted numbers of corals in 22 two meter squares at each station. The percent cover data (Fig. 1B) are from 60 frames per station of underwater videos.

Address these questions:

* What is the overall pattern of change in both species diversity and percent cover at the 3 station locations in the Florida Keys? In what ways are these two measures of coral "health" different? Why might the results for these measures be different? Is one measure better than the other?

* Imagine that you are a diver floating over the Upper, Middle, and Lower Key reefs in 1996 and again in 2000. In what ways would the three locations look different in regard to both coral diversity and coverage of hard corals? Be as specific as you can be.