Coral Communities on Drilling Platforms
For hundreds of thousands or millions of years, the Gulf of Mexico has had precious little hard bottom associated in its shallow sunlit waters. There is some hard bottom, however most of it is in depths too great to receive much light. Algae, corals, and other organisms requiring light cannot live there. But there is an exception to this: The Flower Garden Banks in the northwestern Gulf, at the edge of the continental shelf (110 miles SW of Galveston, TX).
These banks were created and brought into shallow water by the emergence of two salt domes in the ocean floor. The banks were raised into shallow water where light is sufficient to support organisms requiring such. Over millions of years, thriving coral reefs have developed on these banks in these clear, warm, offshore sub-tropical waters. Their significance has been recognized by the US government, and they have been declared the NOAA Flower Garden Banks National Marine Sanctuary. These reefs are isolated by hundreds to thousands of miles from other reefs in the Gulf.
Up until the 1940s, there was no other shallow hard-bottom in offshore waters of the Gulf. But then we began deploying oil and gas drilling platforms there. In all, ~6,000 major platforms have been installed. ~4,000 remain at this time (2002).
We have recently found that these platforms have acted as new settling substrate for corals. In fact, in a study of ~10-15 platforms within a 50-mile radius of the Flower Garden Banks, we have found that some of the platforms have substantial coral populations on them of both reef-building (hermatypic) and non-reef-building (ahermatypic) types. The corals seem to be most abundant on the older platforms (> 12 yrs). These are all common Caribbean corals.
The platforms are also covered with other plants and animals associated with Caribbean coral reefs - algae, sponges, tunicates, crabs, sea fans, etc. They are also home to abundant populations of reef-associated fish. These include demersal reef fish, such as damselfish, parrotfish, and surgeonfish; semi-demersal fish, such as chromids; and pelagic fish, such as sharks, cobia, amber jack, etc. These artificial structures, over time, have become true living, breathing coral reefs.
Photos by Josh Collins and Toby Armstrong
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