Reference : Biol. Bull., 157 : 234—248. (October, 1979) DIETARY FATTY ACID AND TEMPERATURE EFFECTS ON THE PRODUCTIVITY OF THE CLADOCERAN, MOINA MACROCOPA LOUIS R. 1 Departnzent of Biology, Yale University, New Haven, Connecticut 06520 Analyses of the relationships between pimysical parameters and the quantity and quality of food in relation to zooplankton physiological processes such as ingestion, assimilation (growth) and reproduction Imave been scarce. These studies are dif ficult since experimental techniques have lacked means to keep biotic factors con stant while modifying a physical factor, or vice versa. As a result, the nutritional quality of a particular food under certain physical conditions has not been evaluated. The study of interactions between the quantity and quality of food available for a zooplankter and existing physical paranmeters is very important. The struc ture of zooplankton communities may be partially determined by time relative abilities of fauna to efficiently utilize and process the available food and thereby satisfy their individual nutritional requirements. Investigators who have classified the nutritional suitability of a particular food for a predator have observed effects on ingestion, assimilation and reproduction. No study has adequately controlled experimental conditions so that the inter relationships among a physical factor, the chemical composition of diet, and the populationdynamicsofa zooplanktonspeciescouldbe identified. Stuart,McPherson,and Cooper (1931) studiedtherelative valueof a variety of bacterial species as food for time aseptic cladoceran, Moina macrocopa. They found differences in growth, fertility, aimd fecutmdity. Lefevre (1942) demonstrated thatthenormalgrowthand reproduction ofvariousciadoceran speciesweredepend ent upon the suitability (physical or physiological) of species of fresh water algae. Monoxenic culture of two species of Crustacea, Arternia sauna, and Tigrio pus japonicus,anharpacticoid copepod,by Provasoli,Shiraishiand Lance (1959) demonstrated that many unialgal diets either failed to permit growth to adulthood or allowedonly a fewconsecutivegenerations.Interestingly, a phytoplankton species that was nutritionally good for one species was not always good for time other species. The apparent nutritional deficiencies of some of the unialgal diets could often be rectified by the addition of specific vitamins or other organic com pounds (Shiraishi and Provasoli, 1959). Lee, Tietjen, and Garrison (1976) observed a seasonal â€oe¿switching― of nutritional requirements for Nit ocra typica, an harpacticoid copepodfrom saltmarsh aufwuchsconmmunities.In thesestudies timecomparativenutritional valueofunialgaldietsofvariousspeciesandstrains was determined by growth rate and fecundity measurements. In some cases the nutritional adequacy of a particular algal diet was temperature dependent. Guerin and Gaudy (1977) and Gaudy and Guerin (1977) grew the harpacticoid copepod, Tisbe holothuriae, on a variety of artificial chemically undefined particulate diets. The dry weight, elementary chemical composition, fecundity, sex ratio, and result 1 Present address: J3odega Marine Laboratory, Box 247, Bodega Bay, CA 94923. 234