Mucous sheet production by poritid corals

Date of Award




Degree Name

Doctor of Philosophy (Ph.D.)


Marine Biology and Fisheries

First Committee Member

Alina Szmant - Committee Chair


Mucous sheets, produced by poritid corals, provided a test system to determine the contribution of mucus production to reef trophodynamics. This dissertation examined mucous sheet formation by two common Caribbean poritids, Porites astreoides and Porites furcata.Mucous sheet formation by both P. furcata and P. astreoides had a lunar periodicity with the timing of mucous sheet formation distinct for each species. The cyclical formation of mucous sheets was correlated with polyp contraction behavior and may be a consequence of this lunar periodicity of polyp activity. Mucous sheet formation was not correlated with any of the environmental parameters measured. Mucous sheet formation was induced experimentally by exposing corals to reduced salinities or increased sedimentation. The observations that polyps contract prior to mucous sheet formation, both during the lunar cycle of mucous sheet formation and when a coral is stressed, lead to the hypothesis that the coral may control mucous sheet formation by regulating fluid mucus secretions and ciliary currents through polyp behavior. This suggests that cyclical mucous sheet formation in Porites may not have a specific function, although mucous sheets may protect the colony from fouling during stressful environmental conditions.Knowledge of the predictable cycle enabled estimates of the rate of mucous sheet production. Biochemical analyses indicated that the mucus was primarily a carbohydrate-protein compound. Mucous sheets had a mean caloric content of 3.5 cal/mg ash-free dry weight and were 68% ash. Both the high ash content and low organic content suggest that mucous sheets have a low nutritional value. C:N ratios for mucous sheets ranged from 4.8 to 5.9. In terms of both carbon and caloric content, mucous sheet production accounted for less than 2% of published values of coral gross photosynthesis. In the San Blas Islands, Panama, Porites astreoides produced mucous sheets at a rate of 1.5 gC/m$\sp2$/y and 0.3 gN/m$\sp2$/y. Each month, when the mucous sheet is present, mucous sheets may represent pulses of carbon and nitrogen to the reef food web. However, the low annual production rates suggest that mucous sheets make only a small contribution to the overall energy flow of coral reefs.


Biology, Ecology; Biology, Oceanography

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