Biological Observations

A qualitative biological survey was conducted in Little Cayman, Cayman Islands adjacent to the NOAA/ICON pylon and on Snapshot Reef on 22 and 23 July 2009, respectively. Only a few coral colonies exhibited paling or mild bleaching. Multiple colonies of Siderastrea siderea were mottled, displaying a blue or purple coloration (i.e., this is how this species looks when it begins to pale). It is likely that this is just a result of the normal seasonal declines in zooxanthellae densities and tissue biomass that occur in summer given that few other species or individuals exhibited noticeable paling.

Some coral colonies exhibited signs of the coral disease "white plague." Fortunately, infected colonies appeared to be few and far between. This image illustrates what appears to be recent mortality due to white plague on a colony of Montastraea annularis (all images taken by and courtesy of Dr. Jen Dupont, NOAA Knauss post-doctoral scholar). Drs. Marilyn Brandt and Carrie Manfrino have obtained a long-term dataset which shows that white plague has been the most significant cause of coral mortality in Little Cayman over the last 5-10 years. In fact, Dr. Marilyn Brandt (personal friend and colleague of mine) did a large portion of her Ph.D. work on Little Cayman, where she built an agent-based, data-driven model on the spread of disease on coral community structure. Researchers in the past have implicated coastal runoff and nutrification as the driver of the increase in coral diseases throughout the Caribbean. Marilyn's findings are extremely important in that she has shown that coral disease can be the main cause of mortality for sites without significant land-based sources of pollution. Way to go Marilyn!

There were a fair amount of clionid sponges overgrowing some dead coral skeletons. The image below illustrates clionid colonization of a Diploria labyrinthiformis skeleton. Some species of Cliona are known to actively overgrowth and kill live coral tissue, but it is not known if what was observed is a result of direct overgrowth or solely clinoid recruitment to the dead coral skeleton following mortality. Clionid sponges are of particular concern because they can be significant bioeroders as they directly dissolve coral skeletons and reef framework.













Seawater temperatures were warm when the station went online (29.9 - 30.0 degrees Celsius), but it is unknown if these are representative of the 'normal' seasonal cycle (climatology) for this site because of the lack of long-term in situ data.

Derek P. Manzello, Ph.D.