Herbivory by crabs and the control of algal epibionts on Caribbean host corals |
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Authors: | L D Coen |
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Institution: | (1) Department of Zoology, University of Maryland, 20742 College Park, MD, USA;(2) Present address: Dauphin Island Sea Lab, Marine Environmental Sciences Consortium, P.O. Box 369-370, 36528 Dauphin Island, AL, USA |
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Abstract: | Summary A short-term experiment was conducted to examine the relationships among the branching coral Porites porites, algal epibionts, and a facultative crab associate Mithrax sculptus in Belize, Central America. Initial field observations suggested that coral colonies supporting resident crabs generally had lower algal cover than colonies without crabs. The hypothesis was tested that Mithrax significantly depresses host coral algal cover and thereby indirectly affects host survivorship and growth. Crab accessibility to an array of coral colonies, similarly covered with algal epibionts, was manipulated in three treatments. Results strongly support the hypothesis, with significant differences in algal cover (primarily Dictyota spp.) noted among treatments after only one month. Caged heads with crabs included and uncaged natural controls allowing crabs free access averaged less than 10% cover, whereas mean algal cover exceeded 75% where crabs were excluded. The uncaged treatment, in which crabs were allowed free access to Porites heads was not significantly different from the crab inclusion treatment. Collectively, these results demonstrate that under natural conditions, crabs can have pronounced effects on host corals by reducing fouling algal epibionts. Furthermore, these facultative coral associates may have more important, albeit localized effects on Caribbean corals than has been suggested previously. |
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Keywords: | Algae Caribbean Coral reeb Herbivory crabs |
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