FORAMINIFERS AS INDICATORS OF PHOTO-OXIDATIVE STRESS: COMPARING BLEACHING PREVALENCE IN FORAMINIFERS WITH RATES OF DECLINE IN CORAL COVER IN THE FLORIDA KEYS, USA

Reef-building coral populations and communities are in decline worldwide, with serious implications for carbonate sedimentation and coastal erosion. Larger foraminifers, which host algal endosymbionts in physiological relationships analogous to those in zooxanthellate corals, have been proposed as bioindicators for assessment and monitoring of modern reefs. The Coral Reef Evaluation and Monitoring Project (CREMP) was established in 1996 by the Florida Fish and Wildlife Research Institute to record the status and trends of stony corals in the Florida Keys and to aid in the management of this declining resource. A major observation from this ongoing monitoring program is that offshore reefs are declining more rapidly than inshore patch reefs. We hypothesize that differences in photo-oxidative stress between inshore and offshore reefs can at least partly explain differences in rates of decline in coral cover. Previous research has demonstrated that amphisteginid foraminifers, which are abundant on reefs worldwide, bleach in response to photo-oxidative stress. Therefore, we sampled both benthic foraminiferal populations and concentrations of photo-protective colored dissolved organic matter (CDOM) in reef waters at 32 CREMP patch-reef, shallow offshore-reef, and deep offshore-reefs sites at peak seasonal solar radiation (May-June) in 2006 and 2007. Comparison of foraminiferal data from 2006 with the CREMP data for total coral cover and for decline in coral cover since 1996 revealed significant correlations between foraminiferal bleaching and coral cover on patch reefs and between foraminiferal bleaching and percent coral decline on patch reefs. Moreover, concentrations of CDOM were observed to significantly decline between inshore and offshore sites. Data collected in June 2007 are being compared to the CREMP data sets and to the 2006 foraminiferal data set to determine if observed trends are robust. This research is part of an effort to develop protocols for bioindicators that can be applied to the South Florida reef tract and to reefs worldwide. Additionally, results may strengthen rationale for protecting mangrove coastlines, as mangroves not only protect shorelines, but are major producers of CDOM.