Coral Reef Assessment: An Index Utilizing Sediment Constituents

Resource managers need inexpensive bioindicators to evaluate the health of coral reef ecosystems and to inform decisions on when and where to utilize more expensive assessment techniques. Following USEPA Guidelines for Evaluating Ecological Indicators, I developed the SEDCON Index (SI), a rapid-assessment protocol which utilizes reef sediment composition to assess the integrity of coral-reef communities. Key advantages of this index are that it entails non-destructive sampling and is applicable to reefs worldwide. The underlying assumption of the index is that community structure is reflected by proportions of recognizable remnants of calcareous shells and skeletal remains of mixotrophic (zooxanthellate corals and larger foraminifers), autotrophic (calcareous and coralline algae), and heterotrophic (e.g., bryozoans, molluscs, smaller foraminifera) benthic organisms, as well as unrecognizable debris as a proxy for bioerosion. Implementation and assessment of this diagnostic tool is presented for the Florida Middle Grounds (FMG) and the Coral Reef Evaluation and Monitoring Project (CREMP) sites in the Florida Keys National Marine Sanctuary (FKNMS). I calibrated SI data with benthic community data from CREMP. Data from samples collected in FKNMS between 2001 and 2004 indicate dominance of the sediments by bioerosional debris, whereas data from samples collected in the early 1980s from the Florida Keys and from Navassa in 2004 indicate lower proportions of unidentifiable components. Application of the SI provides an assessment of ecosystem condition on scales of years to decades