763 resultados para Marine Corps Air Ground Combat Center (U.S.)


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At head of cover title: Generalized computer program.

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U.S. Marines advancing under combat conditions. Caption; "Making slow progress over volcanic sands off SE Beaches at Iwo. Mt. Suribachi looms through dust and smoke in the background."

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U.S. Marines advancing on beach under combat conditions. Caption; "It was rugged going during the early phases of the operation."

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U.S. Marines advancing on beach under combat conditions. Caption; "Fire and movement over volcanic dunes off southeastern beaches."

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At head of cover title: Generalized computer program.

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Item 383-B.

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At head of cover title: Generalized computer program.

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Cover title

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Cover title.

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This study documents marine ecological conditions at Rincon Island, located approximately 0.8 kilometer offshore between Ventura and Santa Barbara, California, in a depth of 14 meters. The island, which was constructed between 1957 and 1958 to serve as a permanent platform for oil and gas production, is particularly suitable for ecological study. Habitat features associated with the armor rock and concrete tetrapods surrounding the island support a 'microecosystem' which differs in biotic composition from surrounding natural bottom areas. A major part of the study was devoted to analysis of seasonal dynamics in biotic composition. Permanent transects extending from the high intertidal to natural bottom were established normal to each of the four cardinal sides of the island. All macrobiota were censused in duplicate 1-square meter quadrats along each transect during each of the four seasons. Data analysis indicated that many species exhibit significant variability in abundance from one season to the next. In general, the findings indicate a rich and varied fauna and flora associated with the high-relief solid substrate of Rincon Island which differs substantially from the more depauperate natural bottom habitats in the area.

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Contract no.: DACW72-76-C-0007.

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Benthic fauna from two stations within a 5-year-old borrow area and two control stations off Hillsboro Beach (Broward County), Florida, were sampled quarterly from June 1977 to March 1978 to evaluate the long-term impact of offshore dredging. Generally enhanced productivities occurred within the borrow area, although there was much seasonal variation among stations. Species diversities were usually higher at the borrow stations than at the control stations. The single exception was due to a high concentration of the bivalve E. nitens at one of the control stations in June. Although faunal similarity analysis revealed a qualitative change in the fauna of the borrow area, this change is not considered detrimental. Conspicuous patterns of heterogeneous faunal distributions were evident in this study, particularly for the bivalve E. nitens. No lasting detrimental effects, in terms of numbers of species, faunal densities, or species diversity, resulted from the dredging operation. (Author).

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The long-term effects of beach nourishment on the benthic infauna and surface sediments of Panama City beaches were investigated. Forty-seven stations located on nine transects between West Pass and Philips Inlet, and two nourishment borrow sites were sampled in November-December 1979 and May 1980. The data collected were compared to prenourishment base-line information collected by Saloman (1976). Abiotic parameters, water temperature, dissolved oxygen and salinity were measured. Sediments were analyzed for particle-size distribution, percent organic carbon and percent carbonate. Benthic macroinvertebrates were represented by 162 taxa of 14 major animal phyla. Species composition and faunal densities varied seasonally. Polychaetes and amphipods were the most abundant animal groups; a small number of species were dominant at nearly all stations. Species diversity was lowest in the swash zone and sandbar stations and highest offshore. Sediment composition was similar to that of Saloman's (1976) study within limits of sampling and processing errors. Faunal composition was found to be different from 1976 but was attributed to normal seasonal and spatial variations. Based on benthic community analyses and sediment parameters, no significant differences were found between nourishment borrow sites and surrounding areas and in the nearshore areas where beach nourishment was conducted. No long-term adverse effects of beach nourishment were detected. (Author).