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Environmental Science Analysis of Coral Reef Satellite Imagery
Coral bleaching is a phenomenon in which the algae living in the coral are expelled and the corals turn white. If the conditions causing it continue, the coral may die. Two conditions that have been linked to coral bleaching are (1) unusually high water temperatures and (2) light surface winds. Your assignment is to use satellite data collected by NOAA to investigate whether these conditions occurred in the Caribbean during early Fall 2005. Data has been provided for four locations:
- Bermuda
- Lee Stocking Island in the Bahamas
- Puerto Rico
- US Virgin Islands
Write your data in the following table.
Bermuda Lee Stocking, Bahamas Puerto Rico US Virgin Islands
- Temp. on 9/2/05 (°C)
- Degrees above average (°C)
- Wind speed (knots)
- Highest 2005 temp. (°C)
5 1st^ bleaching threshold month in 2005
of weeks above bleaching
threshold in 2005
- Month DHW started in 2005
- Maximum DHW from Graphs
- Predicted level of bleaching
- Maximum DHW from Fig. 4
- Predicted ranking from satellite data (4=worst bleaching)
- Actual ranking from field data (4=worst bleaching)
- Write your answer here.
- Write your answer here.
Use the following figures and graphs to complete the data table above.
Go to Figure 1, Sea Surface Temperature. This map shows the temperature of the ocean waters, measured from some of NOAA’s satellites on 9/2/05. The data are broken up into squares that are 50 km on a side.
Match the color inside the square to the color on the scale under the map to determine the sea surface temperature for each location.
Question 1. What was the temperature at each of the four reefs on 9/2/05?
Go to Figure 2, Coral Reef Hot Spot. This map shows how much warmer than average the reefs were on 9/2/05. Pinks and blues mean the reef had close to normal temperatures. Orange and reds mean the reef had higher than normal temperatures. Match the color inside the square to the color on the scale under the map to determine how many degrees above average each reef was.
Question 2. How many degrees above average was each reef on 9/2/05?
Go to Figure 3, Ocean Surface Winds. Again, this is data that NOAA measures from its satellites every day. A white area on this map means “no data,” not “no wind.” If a square over a reef is white, look at the surrounding area to get an idea of what the wind speed was probably like. Grays mean very little wind (0-5 knots), blues mean light winds (5-15 knots), greens mean stronger winds (15-20 knots) and yellow-red-purple colors mean even stronger winds (20+ knots).
Question 3. What was the wind speed in the region for each reef on 9/2/05?
Go to Graphs 1-4. Sea Surface Temperature (SST) Time Series Graphs. These graphs give the yearly temperature pattern for each of the four reef sites, measured by NOAA satellites. Note that both 2004 and 2005 are plotted on the same graph. Refer only to the right hand portion of each graph, which is 2005.
The blue lines on the graph are data related to temperature. Use the scale on the left y-axis, also in blue, to answer questions 4-6. Here is what the blue lines mean. A key is also on the graph:
- Dark blue line: sea surface temperature (SST) – notice how it goes up and down over the months of the year (Jan- Dec) because this is actual data for each day
- Dashed light-blue line: average temp for warmest month of the year – notice that it is straight across because it is an average
- Solid light-blue line: one degree above average, which is the threshold for coral bleaching (anything above this means the corals might die from bleaching) – notice that it is straight across because it is one degree above average all the way across
Refer only to the right hand portion of the graph, which is 2005. Answer these questions.
Question 4. For each reef, what was the highest temperature from Jan-Dec for 2005? Use the solid dark blue line and left y-axis, and record in the data table.
Question 5. Using the left y-axis for temperature and the months on the x-axis, determine in what month the temperature (solid dark blue line) first crossed the bleaching threshold (solid light-blue line), and record in the data table for each reef.
Question 6. For each reef, count the number of weeks the temperature stayed above the threshold by counting how many weeks the dark blue line stayed above the solid light-blue line. Record for each reef in the data table.
The red lines on the graph are data related to Degree Heating Weeks (DHW). This is a measure of how many weeks of heat have accumulated. The more degree heating weeks, the more the coral is threatened with bleaching. Use the scale on the right y-axis, also in red, to answer these questions. Here is what the red lines mean. A key is also on the graph:
- Solid red line (forms a “mountain” on the graph): Degree Heating Weeks (DHW); shows the accumulation of heat stress on the coral
- Sea Surface Temperature, September 2nd,
- Coral Reef Hotspot, September 2nd,
Ocean Surface Winds, September 2
nd
Go on to the next page ….
2005 Maximum Degree Heating Weeks
