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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 3207

James B. Lackey and Kenneth A. Clendenning; Ecology of the Microbiota of San Diego Bay, California. Transactions of the San Diego Society of Natural History 14(2):9-40, 1965

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During July and August, 1959, the plankton in 69 samples and the benthos in 36 samples from eight stations in and near San Diego Bay were listed qualitatively and quantitatively. The samples were taken at about weekly intervals. The examinations revealed a high plankton production in San Diego Bay for the period of observation. Over 340 species or genera of algae, protozoa and sulfur bacteria were represented in the samples. The more frequent and denser blooms observed in San Diego harbor indicated considerable fertilization from the surrounding urban population. Inhibiting as well as stimulating influences of organic wastes were apparent in the plankton and benthic microbiota. Coastal dinoflagellates were almost absent from the fertilized sections of San Diego harbor which bore large populations of photosynthetic microflagellates and other small algae. Fertilizing materials were evidently transformed and greatly diluted within the bay, since at the outermost stations there was a large diminution of the plankton and changes in its species composition. No particular indicator organisms were found. The species found in San Diego harbor were practically all present at the coastal control station, which showed the greatest array of species. Sulfur-depositing bacteria, when abundant, indicated deposits of organic matter and partial to complete anaerobism in the mud. Chlorococcales were assumed to indicate soluble organic substances in the parts of the bay where they were most abundant. On the basis of planktonic Volvocales, Station II opposite National City was the only sampling point in San Diego Bay that showed evidence of recent organic enrichment. The large numbers of colorless euglenids in the mud-water interface indicates an important role for them in the mineralization of organic matter. They were probably second in importance to the bacteria in this function. Since most of the solid materials eventually reach the bottom, their role in the transformation of organic sediment needs critical evaluation. Ciliates are probably the third most important group at the sediment-water interface. Dino-flagellates occurred infrequently in the sediment-water interface, but their effects include some reaeration due to photosynthesis and they were not aggregated except in a thin film at the interface. They were mainly planktonic, and the fertilized harbor water apparently decreased the number of dinoflagellate species and the frequency of their occurrence. Several phytoplankton categories (e.g. Cryptomonadaceae, Chlorococcals, Volvocales) which attained outstanding numbers in fertilized sections of San Diego harbor seemed to be retained there as a characteristic resident population. A related distribution was observed for the red ciliate Mesodinium rubrum (Cyclotrichium meuneri), which attained bloom proportions in South San Diego Bay with a progressive diminution in numbers toward the harbor entrance.