ibclogo XVI International Botanical Congess


Abstract Number: 4730
Session = 19.10.7


BOTTOM-UP CONTROL OF MACROALGAL BLOOMS IN SOUTH FLORIDA AND JAMAICA.


B. E. Lapointe (Marine Nutrient Dynamics Program, Marine Science, Harbor Branch Oceanographic Institution, Inc., 5600 US1 North, Ft. Pierce, FL 34946, USA)


During the past two decades coral reefs in many parts of the world, especially the greater Caribbean area, have been altered by phase shifts away from hermatypic (reed-forming) corals and towards fleshy macroalgae or algal turfs. Because the phase shift on reefs in south Florida and Jamaica specifically involved frondose maroalgae rather than algal turfs, I hypothesized that bottom-up control via nutrient enrichment must be a causal factor. My studies were multifaceted and included measurement of dissolved inorganic nutrient concentrations, salinity, benthic biotic cover, alkaline phosphatase activity, limiting nutrient bioassays, tissue C:N:P contents and stable nitrogen isotope ratios (15N/14N). The results provided multiple lines of evidence that the macroalgal blooms on Floridian and Jamaican reefs have results from low level nutrient enrichment that enhances algal productivity and growth. These findings support the view that the ongoing global fertilization of the oceans from local and regional sources is having an adverse impact on the health and longevity of coral reef ecosystems, which are adapted to low nutrient waters where calcification processes by corals and calcareous algae are favored.


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