Density, species diversity, species richness, and evenness of bivalve mollusks were measured in the deep (0.2km to 3.7km) northern Gulf of Mexico to describe the community structure of benthic bivalve mollusks. Density decreased gradually from shallow continental slope depths, with remarkably high values in the Mississippi canyon, to the deepest sites. Diversity of bivalve mollusks increased from shallow continental slope depths, with low values in the Mississippi canyon, to a maximum at intermediate depths (1-2km), followed by a decrease down to the deepest locations (3.7km). Nine distinct groups were formed on the basis of the similarity in species composition. The pattern varied more abruptly on the slope compared to the deeper depths, possibly due to steeper gradients in physical variables. ANOVA indicated that the density of bivalve mollusks was not significantly different at different depths, was not significantly different on different transects, was not significantly different between basin and non-basin, but was significantly different in canyon and non-canyon locations. Similar distinctions were observed in diversity, except that basins were lower than non-basins. The patterns observed reflect the intense elevated input of terrigenous sediments accompanied by high surface-water plankton production from the Mississippi River to the north central gulf.

Abstract In 1972, Taiwan¡¦s first squid jigging vessel ¡§YUNG CHUNG¡¨ succeeded in developing fishing ground at Sea of Japan. Since that time, Taiwanese squid jigging vessels keep succeeding in developing new Squid fishing grounds in New Zealand, North Pacific Ocean, and Southwest of the Atlantic Ocean. Because the squid catch continued to grow, Taiwan began to export squid products to China, Japan, South Korea, North America, and Europe. In volumes, the top three countries of catching squids are Taiwan, China and South Korea vessels at present. However, in reality, even the freezing ability and catching quality of Taiwanese jigging vessels are much better than the other two countries, the export price for Taiwanese catch are the lowest. The major factor is because the packaging weight has not been standardized. It reduces the purchase willingness and the selling price in the overseas markets for Taiwanese catches. Currently, Taiwan now has 105 squid jigging vessels, but each vessel process the catch in their own way. Therefore, it makes the crew difficult to follow the work procedures which influence the efficiency, and result in inconsistent of the packaging weight. This research we use ¡§Analytical Hierarchy Process¡¨. Through consulting with the experts and studying based from the historical documents, we try to establish the key factors on the construction and design of our questionnaire. We then collect the answers from the fishery companies in Taiwan and sea food processing factories in China, and then we confirm the results trough the statistical analysis. We hope through a dependable data and solid research, we can provide concrete recommendations to squid fishery companies, processing factories, and Fisheries Agency of the Government on benefits of packaging weight standardization. We then hope that the ultimate goal is to help raise the Taiwanese squid price in overseas markets.

A deep-sea time-lapse camera and several temperature probes were deployed on the Gulf of Mexico continental shelf at a biological community associated with a gas hydrate outcropping to study topographic and hydrologic changes over time. The deployment site, Bush Hill (GC 185), is located at 27°47.5' N and 91°15.0' W at depths of ~540m. The digital camera recorded one still image every six hours for three months in 2001, every two hours for the month of June 2002 and every six hours for the month of July 2002. Temperature probes were in place at the site for the entire experimental period. The data recovered provide a record of processes that occur at gas hydrate mounds. Biological activity was documented by identifying the fauna observed in the time-lapse record and recording the number of individuals and species in each image. 1,381 individual organisms representing 16 species were observed. Sediment resuspension and redistribution were regular occurrences during the deployment periods. By digitally analyzing the luminosity of the water column above the mound and plotting the results over time, the turbidity at the site was quantified. A significant diurnal pattern can be seen in both luminosity and temperature records, indicating a possible tidal or inertial component to deep-sea currents in this area. Contrary to expectations, there was no major change in shape or size of the gas hydrate outcrop at this site on the time frame of this study. This indicates that this particular mound was more stable than suggested by laboratory studies and prior in situ observations. The stable topography of the gas hydrate mound combined with high bacterial activity and sediment turnover appears to focus benthic predatory activity in the mound area. The frequency and recurrence of sediment resuspension indicates that short-term change in the depth and distribution of surface sediments is a feature of the benthos at the site. Because the sediment interface is a critical environment for hydrocarbon oxidation and chemosynthesis, short-term variability and heterogeneity may be important characteristics of these settings.

Macrobenthos of the deep, northern Gulf of Mexico have been sampled with large box cores along multiple cross-depth transects extending from depths of 200 m out to 3700 m. Four major depth zones have been identified based on the faunal similarities (beta diversity) between geographic sites, with the two intermediate-depth zones being divided horizontally down the middle of the basin. The input of food resources appears to control the observed patterns. Each zone and sub-zone can be described by a characteristic animal density, biomass and biodiversity (alpha diversity). Highest densities and biomass occurred in two large submarine canyons, the Mississippi and De Soto Canyon, but the two habitats are markedly different. The alpha diversity displays an intermediate depth maximum. Species richness (gamma diversity) is highest on east mid-slope, due, we suggest, to habitat complexity, but alpha diversity is lowest at the canyon head due to extreme dominance by amphipods. Small mean individual size and low densities encountered are a reflection of the meager surface water primary production, albeit with exceptional isolated habitats in which detrital material is concentrated, such as canyons on the upper continental slope.

Density, species diversity, species richness, and evenness of bivalve mollusks were measured in the deep (0.2km to 3.7km) northern Gulf of Mexico to describe the community structure of benthic bivalve mollusks. Density decreased gradually from shallow continental slope depths, with remarkably high values in the Mississippi canyon, to the deepest sites. Diversity of bivalve mollusks increased from shallow continental slope depths, with low values in the Mississippi canyon, to a maximum at intermediate depths (1-2km), followed by a decrease down to the deepest locations (3.7km). Nine distinct groups were formed on the basis of the similarity in species composition. The pattern varied more abruptly on the slope compared to the deeper depths, possibly due to steeper gradients in physical variables. ANOVA indicated that the density of bivalve mollusks was not significantly different at different depths, was not significantly different on different transects, was not significantly different between basin and non-basin, but was significantly different in canyon and non-canyon locations. Similar distinctions were observed in diversity, except that basins were lower than non-basins. The patterns observed reflect the intense elevated input of terrigenous sediments accompanied by high surface-water plankton production from the Mississippi River to the north central gulf.

No description available.

Graduation date: 1997

Univ., Diss.--Bremen, 2006.

Thesis (Ph. D.)--University of Washington, 1996. / Vita. Includes bibliographical references (leaves [87]-101).

Thesis (Ph. D.)--Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1989. / Includes bibliographical references.