Physiology and Ecology of Macroalgal Blooms on Coral Reefs off Southeast FloridaEPA Grant Number: R830414
Title: Physiology and Ecology of Macroalgal Blooms on Coral Reefs off Southeast Florida
Investigators: Lapointe, Brian E. , Yentsch, Charles S.
Current Investigators: Lapointe, Brian E. , Barile, Peter J. , Yentsch, Charles S.
Institution: Harbor Branch Oceanographic Institution, Inc. , Plankton Research and Instruments
EPA Project Officer: Hiscock, Michael
Project Period: October 14, 2002 through October 13, 2004 (Extended to October 13, 2005)
Project Amount: $279,098
RFA: Ecology and Oceanography of Harmful Algal Blooms (2002) RFA Text | Recipients Lists
Research Category: Water Quality , Ecosystems , Water , Aquatic Ecosystems
Over the past several decades, macroalgal blooms have degraded the biodiversity and growth of coral reef ecosystems experiencing anthropogenic nutrient enrichment. This problem has reached a critical stage in southeast Florida where blooms of Codium isthmocladumin the early 1990's were followed by a succession of Caulerpaspp. between 1998 and 2001 on fringing reefs in 20 to 50 m depths. Preliminary evidence supports the hypothesis that the decade-long succession of macroalgal blooms is linked to increasing land-based discharges of ammonium derived from sewage via groundwaters and ocean outfalls. To date, little is known of the seasonal patterns in growth and photosynthesis of Caulerpaspp., the relative importance of upwelled nitrate versus ammonium as a nitrogen source, or the potential for herbivores to control these blooms. This project will provide a two-year study of the physiology and ecology of Codium and Caulerpaspp. with the objectives of measuring seasonal patterns in benthic cover, photosynthesis, dark respiration, optical properties, tissue C:N:P ratios and d 15N values, uptake of NH4+ and NO3- under different combinations of irradiance and temperature, and the potential for herbivores to control the blooms.
To achieve these objectives, we propose to: 1) use underwater digital video to quantify seasonal growth patterns (as % cover of reef surface) of the target species on two fringing reefs, 2) measure seasonal changes in tissue C:N:P and d 15N of the target species, 3) measure seasonal changes in spectral absorption, reflectance, dark respiration, and photosynthesis of the target species with and without ammonium enrichment, 4) use controlled, laboratory experiments to determine the effects and interactions of temperature and irradiance on uptake of NNH4+ and NO3- by the target species, and 5) conduct controlled grazing experiments in both the lab and field to quantify the potential for generalist and specialist herbivores to control standing crops as a function of the C:N ratio.
Achieving these objectives will advance our understanding of how physical, chemical, and biological factors interact to initiate, sustain, and terminate macroalgal blooms on coral reefs in southeast Florida. This research will be useful to the scientific community and resource managers not only in south Florida but worldwide by demonstrating the physiological and ecological bases for the formation and termination of harmful macroalgal blooms on coral reefs.