A comparative study of the effects of sedimentation on symbiotic and asymbiotic colonies of the coral Astrangia danae Milne Edwards and Haime 1849

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The effect of heavy sedimentation on corals was examined in the laboratory using both symbiotic and asymbiotic colonies of Astrangia danae Milne Edwards and Haime. Colonies receiving applications of clean fine sand at a rate of 200mg·cm-2 once per day for 4 wk were not different from controls with respect to symbiotic index, colony weights, growth rates, or net oxygen exchange rates. Slight adverse effects relative to controls were noted after increasing the sand applications to three times per day, which became more evident during a 2-wk period of starvation combined with the sand applications. Starved symbiotic colonies were more susceptible than starved asymbiotic colonies to the sediment loading. After the starvation period, sediment-exposed colonies processed for histopathological examination revealed loss of mucous secretory cells in the epidermis, compared to starved controls, along with an increase in mucoid material accumulations in the gastrodermis and calicoblastic epithelium. These results are consistent with previous field observations that sediment loading is harmful to stony corals. However, damage may be minimal as long as adequate nutrients, from either internal (zooxanthellae) or external (Zooplankton, particulates) sources, are available to the coral animal to meet the additional energy expenditures required to rid themselves of sediment. © 1985.

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Journal of Experimental Marine Biology and Ecology