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in higher ratios in the low quality food characteristic of eutrophic conditions. These results and data from the literature are used to propose a two-dimensional niche model to demonstrate the interaction between food quality and abundance on the competitive interaction between Calanoid copepods and Daphnia-like cladocerans.

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The secretion of mucus by eight species of scleractinian corals was measured in situ at the Red Sea reef in Eilat, Israel. Selected coral heads were covered with plastic bags and the total organic matter collected after 24 h was determined. The rate of mucus production by massive forms was significantly greater than that by hemispherical or branched species, supporting the suggestion that the massive species use mucus secretion as a mechanism to prevent burial in heavy sedimentation areas on this reef. Overall mucus production results in about 51 mg of particulate organic production m−3 day−1. Laboratory feeding experiments and assimilation measurements with Acartia negligens feeding on radioactive mucus indicate that the zooplankters can assimilate up to 50% of the organic matter of the mucus. Calorific determinations show this material to contain 5.2 ± 0.13 cal mg−1 ash‐free dry weight.

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