Reef and Fishery Assessment of Navassa Island National Wildlife Refuge

On April 23, 2009 scientists from the NOAA's Southeast Fisheries Science Center in Miami Florida (SEFSC) departed from San Juan, Puerto Rico aboard the NOAA Ship Nancy Foster. Their destination: the Navassa National Wildlife Refuge. Along with the NOAA scientists are researchers from the University of Miami's Rosenstiel School of Marine and Atmospheric Science (UM/RSMAS), the US Fish and Wildlife Service (FWS), and the Director of the Fondation pour la Protection de la Biodiversité Marine (FoProBiM), an NGO based in Haiti.
This work is funded by the NOAA Coral Reef Conservation Program.

Thursday, April 30, 2009

Submerged walls

The topography of Navassa Island is unique. It was once believed to be a small uplifted atoll with a volcanic core and surrounded by a fringing reef. However, the island is only a small portion of the Navassa Ridge above sea level. Located on the Gonave tectonic microplate, and caught in the great strike-slip faults between the Caribbean and North American plates the region is still seismically active today. Due to uplifting and folding processes during the Miocene, Navassa is characterized by sharp cliffs creating submerged walls. The submerged wall, heavily eroded at the surface by the wave action, runs vertically down to 50 or 80 feet deep. This particularity creates a habitat similar to those found in the platform drop off of some islands in the Caribbean. Covered majorly by sponges, seafans, tunicates, calcareous algae and scleractinian corals, the wall offers one of the best diving sites around the island. There are few species of sponges and gorgonians solely found in this kind of environment such as the Devil’s Sea Whip (Ellisella barbadensis) characterized for a single long axis full of polyps. The wall ends in the second or third underwater terrace around the island. But about terraces will be the next blog.
Photo by Abel Valdivia
Abel Valdivia

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