This formula says that the intensity of light at the surface
of the ocean (I0) will decay at an exponential rate as
depth (d) increases. The constant controlling this decay rate is
the clarity of the water (k). When water is very clear, k
will be small; when water contains silt or plankton, k will be larger
and less light will get through.
The information we have is enough to calculate k
for any of the days where light measurements were taken at the Mobil platform
and at the bottom sensors. When we plot k instead of the light intensities,
it is easier to see the changes in water clarity over time. |
Can you rearrange the light extinction equation to calculate
k ? (Click for answer.) |
The graph at right shows a marked decrease in water clarity
(high k values) during the summer months. Because corals depend on
light, these kinds of measurements are important for monitoring the health
of the reef ecosystem.
 |
Why would water clarity decrease during the summer? What could have happened
in the middle of August to abruptly increase water clarity? (Click
for discussion.) |
|
This graph shows how the water over the East Flower Garden Bank filters
out light at different times of the year. |
