Ecological Studies of Symbiosis in Convoluta roscoffensis

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Abstract
The size of the C. roscoffensis population on a beach in Herm, Channel Islands [UK] is subject to wide seasonal variation, being very low in early summer and high in autumn and winter. Of the ecological factors measured, only light (expressed as photosynthetically active radiation) showed a correlation with population size. Low worm numbers, and also low numbers of algae and chlorophyll a content per worm, were associated with high light intensities and vice versa. Worm spacing within colonies, however, remained relatively constant, with a mean value of 9 .times. 105 worms m-2. Estimates of photosynthetic cover (chlorophyll biomass) of 320 mg chlorophyll a m-2, and annual primary productivity for 1977, of 872.9 g C fixed m-2 of colony, approach estimates for coral reefs; they were remarkably high for the potentially disturbed environment of the intertidal sandy beach.