Dissolved organic matter in the water column may influence co...( PORT ARANSAS TexasBacterial communit...)

PORT ARANSAS, TexasBacterial communities endemic to healthy corals could change depending on the amount and type of natural and man-made dissolved organic matter in seawater, report researchers from The University of Texas at Austin Marine Science Institute and Mote Marine Laboratory in Sarasota, Florida.

Healthy corals naturally exude a surrounding mucous layer in which a complex population of bacteria exists. Recent studies have indicated that some coral diseases may be linked to community shifts in this bacterial population.

In experiments with a common reef building coral in the Florida Keys, Chris Shank of the University of Texas Marine Science Institute and Kim Ritchie of Mote Marine Laboratory found an obvious shift in the composition of the coral bacterial community resulting from changes in the pool of surrounding dissolved organic matter.

Dissolved organic matter in the water column near Florida Keys coral reefs comes from a variety of natural sources, including coastal mangroves, seagrasses, and plankton, as well as man-made sources, including sewage effluent. The composition of dissolved organic matter surrounding Florida Keys coral reefs has likely changed in recent decades due to growing coastal populations.

When coastal ecosystems are physically altered, the natural flow of dissolved organic material to nearby coral ecosystems is disrupted with potentially harmful consequences for the corals, said Shank, assistant professor of marine science.

Shank and Ritchie, manager of the Marine Microbiology Program at Mote, placed Montastraea faveolata coral fragments in aquaria filled with water collected from either Florida Bay or from an offshore bluewater site.

Dissolved organic matter concentrations are much greater in Florida Bay than in offshore waters and typically have different chemical characteristics. Water collected from these distinct locations used for the coral incubation experiments rep
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