R.R. Bidigare | USGS Science

USGS1988

Biological measurements and related chemical features in Soviet and United States regions of the Bering Sea

The U.S. results of a joint U.S.-U.S.S.R. expedition to the Bering Sea in 1984 investigated the chemical and biological interactions in the south, east, north and west regions. The nutrients, phytoplankton biomass and primary productivity were enhanced near the ends of a north-south transect of stations. The southern end of the transect had characteristics of the North Pacific Ocean with high nutrient and low phytoplankton concentrations and an elevated concentration of peridinin indicative of dinoflagellates. The middle station of the transect, near the shelf break, had low nutrients and phytoplankton in the upper euphotic zone, but a submerged chlorophyll b maximum indicated green algae was located on the upper boundary of high ammonium concentration and pycnocline. The north end of the transect over the shelf at mid-depth on the boundary of high nitrate and ammonium concentrations produced the highest primary production. Pigment analysis (chlorophyll a , diadinoxanthin and fucoxanthin) indicated the dominance of diatoms and was coincidental to oxygen saturation values as large as 150%. The highest phaeophorbide a concentrations were also observed in this area, suggesting relatively high grazing stress. Measurements of low molecular weight hydrocarbons also suggest high microbiological degradation rates of organic matter in the sediments in the north region. Overall, this research strongly relates nutrient, oxygen and pigment concentrations to the production, decomposition and recycling processes in the open ocean and shelf areas of the Bering Sea.

Bering Sea↗

USGS1987

The importance of methane and thiosulfate in the metabolism of the bacterial symbionts of two deep-sea mussels

Undescribed hydrocarbon-seep mussels were collected from the Louisiana Slope, Gulf of Mexico, during March 1986, and the ultrastructure of their gills was examined and compared to Bathymodiolus thermophilus, a mussel collected from the deep-sea hydrothermal vents on the Gala??pagos Rift in March 1985. These closely related mytilids both contain abundant symbiotic bacteria in their gills. However, the bacteria from the two species are distinctly different in both morphology and biochemistry, and are housed differently within the gills of the two mussels. The symbionts from the seep mussel are larger than the symbionts from B. thermophilus and, unlike the latter, contain stacked intracytoplasmic membranes. In the seep mussel three or fewer symbionts appear to be contained in each host-cell vacuole, while in B. thermophilus there are often more than twenty bacteria visible in a single section through a vacuole. The methanotrophic nature of the seep-mussel symbionts was confirmed in 14C-methane uptake experiments by the appearance of label in both CO2 and acid-stable, non-volatile, organic compounds after a 3 h incubation of isolated gill tissue. Furthermore, methane consumption was correlated with methanol dehydrogenase activity in isolated gill tissue. Activity of ribulose-1,5-biphosphate (RuBP) carboxylase and 14CO2 assimilation studies indicate the presence of either a second type of symbiont or contaminating bacteria on the gills of freshly captured seep mussels. A reevaluation of the nutrition of the symbionts in B. thermophilus indicates that while the major symbiont is not a methanotroph, its status as a sulfur-oxidizing chemoautotroph, as has been suggested previously, is far from proven. ?? 1987 Springer-Verlag.

Marine Biology↗