Experimental Development and Implementation/Calibration of a Tissue-Based Indicator for Sedimentation Impacts in Caribbean Scleractinian Corals

ISSUE: Excessive sedimentation constitutes one of the most persistent and insidious sources of human-induced stress to corals and coral reefs worldwide, via dredging, drilling, agricultural runoff, and coastal and upstream deforestation. Although tolerance to increased sedimentation varies among coral species, sedimentation stress reduces individual fitness, thus resulting in altered coral reef community structure and function. This project is handled in close cooperation with the Broward County (FL) Environmental Protection Department.

Specimens of Montastraea cavernosa employed in the sediment-stress experimental trials.

PROJECT AND FINDINGS: Coral tissues and cellular elements readily respond to environmental stress. This response generally precedes population-level responses by days, weeks, or even months. Because cellular structure is closely related to function, coral physiological dysfunction, impairment, and/or damage can be effectively diagnosed by careful examination of the tissue component parts. The present pilot study is aimed at developing an experimental ranking scale to assess coral and coral tissue responses to increased sedimentation, with potential application in coral sedimentation stress diagnosis and bioassessment. Tissue condition in laboratory-treated and control specimens of Caribbean Montastraea cavernosa, Solenastrea bournoni, and Siderastrea siderea is carefully examined, ranked, and scored considering the type and severity of the morphological and histopathological changes and lesions present. These data are being compiled into an adaptive, provisional Stress Index for describing and assessing coral health status in the field during dredging activities. This system requires field calibration and validation before its application and implementation

Photomosaic illustrating stress-related changes in gross morphology and histopathological condition in Montastraea cavernosa specimens subjected to increased sedimentation (clock-wise): Colony exhibiting normal appearance in minimally stressed conditions; outer epidermis exhibiting good structural integrity in a mildly stressed specimen; colony exhibiting polyp retraction and advanced swelling; colony with retracted polyps and unusual opening of the oral disc, note advancing lesion; and lower gastrodermis exhibiting increased cell granularity and debris, and swelling of the calicoblastic epidermis, in a markedly stressed specimen.

IMPLICATIONS FOR MANAGEMENT: This pilot study is part of a larger project aimed at using coral gross morphology and histopathology in concert with conventional monitoring tools, such as coral community and fish assemblage surveys, and sediment accumulation and texture analyses, to diagnose and assess sedimentation impacts during dredging activities of the Broward County Beach Restoration Project, Segment III. This multilayered approach combines community- and organism-based biomonitoring attributes, thus providing researchers and managers with a broader set of tools for defining coral and coral reef health status in field conditions. The evaluative findings of this pilot study will provide managers with recommendations for using this tool to devise and evaluate alternative management strategies for reducing/mitigating the effects of future coastal dredging projects. This work embodies the NCRI mission to identify gaps in scientific knowledge and to provide scientific synthesis for use by the research and management community.

PARTNERS:
NCRI via NOAA-CSCOR
Broward County Department of Environmental Protections
Florida Department of Environmental Protection