EarthLabs > Corals > Lab 6: Using Data to Identify Hot Spots and Predict Bleaching Events > 6D: Sombrero Reef

Using Data to Identify Hot Spots and Predict Bleaching Events

Part D: Sombrero Reef

Satellite image showing the location of Sombrero Reef (red star) in the Florida Keys. Click image for a larger view. Image source: Google Maps.

The barrier reef in the Florida Keys is the third largest living coral reef system in the world behind the Great Barrier Reef in Australia and the Belizian barrier reef. It is also the only extensive reef system in the continental United States. Sombrero Reef is located off the coast of Marathon, which is the midpoint of the Florida Keys island chain. This beautiful section of reef supports both tourism and commercial fishing, which are major contributors to the economy of the Florida Keys. Since 1990, Sombrero Reef has been under strict regulations as a Sanctuary Preservation Area in the Florida Keys National Marine Sanctuary. In this part of the lab, you will examine data from Sombrero Reef to determine if and how bleaching has affected this reef.

  1. Go to NOAA's Coral Reef Watch home page. Scroll about halfway down to find Time Series at 24 Sites in the left-hand navigation bar. Click on the Current icon to open a page that lists 24 "Virtual Station" sites around the world.
    Locations of the 24 NOAA virtual stations. Image source: NOAA.

    Along with the worldwide data, NOAA also focuses in on several representative coral reef locations around the world. Even though the temperature measurements at these locations are based on satellite measurements, honing in on a specific region is like having a temperature sensor in the water next to a reef, hence the term "Virtual Stations". Data from these stations are updated twice a week.

  2. Find the cell in the table that says Sombrero Reef, FL. Click on the location name to see a map of this location. Then, use your browser's back button to return to the table, and click on the Graphs link for Sombrero Reef.

    This page shows time series graphs for the SST at the Sombrero Reef virtual station, from December 2000 through the most current measurement.

    These graphs show the time series data at a particular station. This particular example shows data from the U.S. Virgin Islands station. The left axis of each graph shows temperature in °C. SST is plotted with a dark blue solid line. The mean SST for each month is plotted as a light-blue cross, and the maximum monthly mean (MMM) is indicated by a light-blue dashed line. There is a bleaching hot spot any time the SST goes above the MMM (dashed light-blue line). The bleaching threshold temperature, equal to 1 °C higher than the MMM, is a solid light-blue line. Whenever the temperature goes above the bleaching threshold, corals experience thermal stress.

    Sample Time Series Graph: U.S. Virgin Islands Temperature

    DHWs are shown at the bottom of each graph as a separate trace. , and the right axis shows the DHW scale.

    Sample Bleaching Time Series Map

    Bleaching Status Table
    Images courtesy of NOAA.

  3. Scroll down to the 2006/2007 graph, and compare the summer seasons.

    Checking In

    Use the Sombrero Reef graphs to answer the following questions.

    • Which month is the warmest on average?
    • What is the maximum monthly mean?
    • What is the bleaching threshold temperature?
    • What was the highest alert level for the Virtual Station at Sombrero Reef in 2006 and 2007?

    Stop and Think

    1: Over what time period, if any, do you think significant bleaching occurred? Explain.