Dissolved organic matter in the water column may influence coral health

March 4, 2008

Bacterial 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 represented the variable nature of dissolved organic matter experienced by corals in the middle and lower Florida Keys.

They found that the microbial community of healthy corals shifts measurably when exposed to water from Florida Bay, suggesting the microbes that normally play a role in coral immunity may be out-competed by potentially problematic bacteria. In combination with increased water temperatures, this is an example of the type of compounded stressors known to cause health problems in corals, or “reef deterioration.”

The scientists reported their results today at the Ocean Sciences Meeting in Orlando, Florida.

The scientists’ research is part of their larger effort to investigate the link between alterations to the south Florida ecosystem and Florida Keys coral ecosystems. Coral reefs there, as with coral reefs around the world, are increasingly threatened by rising water temperatures, advancing ocean acidification and rapidly rising coastal populations.

Corals are especially susceptible to coastal alterations because they commonly exist in shallow waters at the interface of land and sea.

Shank and Ritchie are planning a series of experiments to more closely evaluate the chemical nature of the water column dissolved organic matter surrounding the corals in the Florida Keys and identify shifts in potentially harmful bacterial populations.

Source: University of Texas at Austin

Explore further: Volunteers help track endangered, enigmatic bonneted bat

Related Stories

Scientists develop new methods to track ocean biodiversity

May 12, 2015

How can you track changes in complex marine ecosystems over time? MBARI scientists are part of a team trying to do just this with a five-year, $7 million grant through the National Ocean Partnership Program. The proposed ...

Recommended for you

Researchers design first artificial ribosome

July 29, 2015

Researchers at the University of Illinois at Chicago and Northwestern University have engineered a tethered ribosome that works nearly as well as the authentic cellular component, or organelle, that produces all the proteins ...

Meet the high-performance single-molecule diode

July 29, 2015

A team of researchers from Berkeley Lab and Columbia University has passed a major milestone in molecular electronics with the creation of the world's highest-performance single-molecule diode. Working at Berkeley Lab's Molecular ...

Researchers build bacteria's photosynthetic engine

July 29, 2015

Nearly all life on Earth depends on photosynthesis, the conversion of light energy into chemical energy. Oxygen-producing plants and cyanobacteria perfected this process 2.7 billion years ago. But the first photosynthetic ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.