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Last updated: October 11, 2002
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The Florida Keys: What is happening to the reef tract and why?
Part 2: Reef Decline: it is Lots of Things
Overview:
Sea Level Rise: Sea level has risen 8.5 inches in the past 75 years as
recorded at Key West, Florida. As sea level rises nutrients on land are washed
out into the marine environment. In addition, tidal passes are created as sea
level rises creating pathways for sediment-laden and nutrient-rich waters from
the Gulf of Mexico to flow out to the reef tract. It is a known fact that reefs
are fewer and less healthy where these tidal passes occur. Reefs located where
there are few or no passes tend to be healthier and more abundant.
Saharan Dust: A new theory that Eugene Shinn has come up with is the effects of
Saharan dust on coral health. Dust from Africa contains fungal spores
(Aspergillus), nutrients (iron and phosphorus), and possibly other contaminants
such as viruses. This subject is still under investigation.
Atmospheric Carbon Dioxide (CO2): Levels of CO2 have been steadily
increasing since the industrial revolution because of increasing number of CO2-
emitting cars and factories. Increasing CO2 levels in ocean water may create an
imbalance in water chemistry causing algae to thrive and compete with coral
health and growth.
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Sea Level Rise
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Graph of Key West sea level record. (Click
on graph for full-sized version.)
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| As sea level rises, nutrients
from the soil are released into the water. Algae flourish in the prescence
of nutrients.
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Illustration of nutrients entering water.
(Click on graph for full-sized version.)
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Map of area shown below. (Click on image
for full-sized version.)
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This is an illustration
of the area shown in the green box in the South Florida map
(above, right).
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As sea level rises, new
tidal passes are created allowing muddy, nutrient-rich water from the gulf
of mexico to flow into the clear, low nutrient waters of the atlantic ocean.
Coral reefs off the seven mile bridge (marathon area) began dying about
2,000 years ago.
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Sea fan
Fungal infection (Aspergillosis)
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One billion tons of african dust is deposited in the caribbean
and se usa each year. Dust is the source of red soils throughout the bahamas
and it feeds the amazon rain forest.
African dust contains spores
of soil fungus. One such fungus causes a caribbean-wide disease that affects
sea-fans.
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An article entitled "Red Dust Plaguing Coral Reefs"
was featured in the February 14, 1999 issue of south Florida's Sun-Sentinal newspaper.
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Post-1983 spiny black
urchin (Diadema)die-off
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Pre-1983 die-off (notice
there is no algae)
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Nutrients in dust, mainly
phosphate and iron, may cause algae to flourish in areas that are normally
low nutrient environments and therefore compete with corals. |
Graph of atmospheric carbon dioxide concentration vs. CO2 concentrations (ppmv).
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Carbon dioxide in the atmosphere
is rising. Plant life is stimulated by carbon dioxide (CO2). CO2 may
stimulate growth of algae in the water that competes with coral development
and growth.
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Next: Human and Natural Threats on Reef Health
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