Caulerpa brachypus

     At a recent ISWG meeting, Dr. Brian LaPointe (Harbor Branch Oceanographic Institution) presented his latest findings on the invasive marine algae Caulerpa brachypus found just off the southeastern coast of Florida.  He noted the fundamental driving force in marine coastal ecosystems is the accumulation of nitrogen and phosphorus in freshwaters that reach the seas.  These excess nutrients cause harmful algae blooms that can significantly impact coastal ecosystems in terms of producing lower dissolved oxygen levels and lower biodiversity. 

Human sources of excess nutrients in the Southeast Florida coastal area are sewage ocean outfalls (about 400 million gallons a day), surface water inlet discharge, and submarine groundwater discharges.  Dr. LaPointe noted that Caulerpa brachypus, a native of the Pacific, was first detected in Florida in 2001 and its presence due to an aquarium release.  The species quickly spread.

A network of sampling sites was established for this non-native species in 2003 and it appears that high nitrogen concentrations from sewage and groundwater discharge played a significant factor for producing Caulerpa brachypus's high biomass that degraded this region’s coral reefs.  Caulerpa brachypus grows best at low light levels but may thrive under higher light levels if sufficient nutrients are available.  In more turbid waters, this invasive alga may grow in shallow depths as oppose to its optimum depth of 90 feet. 

In 2004, a series of hurricanes (severe wave actions) removed most of this alga from the sampling locations.  In 2005, small populations reemerged at the sampling sites but may be having difficulty in building up its biomass because of a highly disturbed bottom substrate (too much sand).  Dr. LaPointe believes that this invasive non-native alga could expand its range again in Florida, especially in other nutrient laden waters, threatening Florida's more southern coral reef areas in the future.  

   
A Caulerpa brachypus population in 2004 along the Southeastern coast of Florida.

Links

DEP Southeast District

Harbor Branch Oceanographic Institution