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Abstract: Anthropogenic marine debris is an increasing concern because of its potential negative impacts on marine ecosystems. This is a global problem that will have lasting effects for many reasons, including: (1) the input of debris into marine environments is likely to continue (commensurate with population increase and globalization), (2) accumulation, and possibly retention, of debris will occur in specific areas due to hydrography and geomorphology, and (3) the most common types of debris observed to date will likely persist for centuries. Due to the technical challenges and prohibitive costs of conducting research in the deep sea, little is known about the abundance, types, sources, and impacts of human refuse on this vast habitat, and the extreme depths to which this debris is penetrating has only recently been exposed. We reviewed 1149 video records of marine debris from 22 years of remotely operated vehicle deployments in Monterey Bay, covering depths from 25m to 3971m. We characterize debris by type, examine patterns of distribution, and discuss potential sources and dispersal mechanisms. Debris was most abundant within Monterey Canyon where aggregation and downslope transport of debris from the continental shelf are enhanced by natural canyon dynamics. The majority of debris was plastic (33%) and metal (23%). The highest relative frequencies of plastic and metal observations occurred below 2000m, indicating that previous studies may greatly underestimate the extent of anthropogenic marine debris on the seafloor due to limitations in observing deeper regions. Our findings provide evidence that submarine canyons function to collect debris and act as conduits for debris transport from coastal to deep-sea habitats. [Copyright &y& Elsevier]

Abstract: On the basis of mass balance calculations performed for nitrogen (N) uptake experiments in the Southern California Bight (SCB), it has been suggested that a significant portion of dissolved inorganic N (DIN) uptake results in the production of dissolved organic N (DON). To investigate this process, the fate of ammonium (NH4 +) and nitrate (NO3 −) uptake was quantified within the euphotic zone at three coastal stations in the SCB using 15N tracer techniques. Several trends in the fate of DIN and the production of DON were observed. First, production of particulate N (PN), from both NH4 + and NO3 −, was quantitatively more important in near surface waters, while DON release dominated within the nitracline. Second, the percentage of gross N uptake released as DON was generally higher when NO3 −, rather than NH4 +, was the substrate. Third, the percentage of N released as DON was higher at night, relative to the day. Fourth, rates of DON release were significantly correlated to NH4 + regeneration, suggesting that similar mechanisms are responsible for both processes—presumably grazing. The results of this study indicate that the DON pool is a sink for DIN uptake on the time scale of hours. One implication of this finding is that new production estimates based on 15NO3 − uptake rates will likely underestimate particle flux out of the surface layer because the rate of NO3 − uptake is underestimated due to loss of DO15N during the incubation. On time scales of months to years, however, the N that is taken up as NO3 − and released as DON will likely contribute to export flux via incorporation of the dissolved phase during seasonal mixing into sinking particles or transport. The export of DON on these time scales argues for the use of gross uptake rates to calculate f-ratios. [Copyright &y& Elsevier]

Presents a study that examined the depth distribution and temperature dependence of sulfate reduction by thermophilic bacteria in hydrothermal surface sediments of the southern trough of the Guaymas Basin in California. Description of the hydrothermal sediments; Profiles of temperature and sulfate; Examination of the reduction of sulfate in sediment cores; Influence of temperature on sediment sulfate reduction.

Investigates the individual, population, and community responses to mesoscale variability of the euphausiid Nematoscelis difficilis and the zooplankton assemblage of the California Current. Variations in the DNA sequences of the genes encoding phosphoglucose isomerase and lactate dehydrogenase; Differences between pooled nearshore and offshore samples; Impact of the mesoscale features and circulation patterns of the California Current on biological processes.

Presents a study which examined sediments collected from seeps in California for the presence of benthic foraminifera. Methods Results; Discussion.

Presents a study which found that the fractionation of a photosynthetic carbon is affected by variations in diffusive transport of carbon dioxide into phytoplankton cells in Monterey Bay, California. Implications of variation in C fractionation in plankton; Methods and results; Discussion.

Presents information on a study which analyzed the spatial distribution of planktonic particles in an eddy-jet system and their relation to a hydrodynamic structure in California. Description on the variability of particle abundance in the region; Methodology of the study; Results and discussion; Conclusions.

Presents data on the size-specific particulate organic carbon (POC), particulate organic nitrogen (POC), dry mass and Chl, a content of four major types of marine snow aggregates, from the surface waters off coastal California. Laboratory analysis for chemical content and size; Determination of the relationship between aggregate size and chemical content; Importance of aggregates to a variety of marine processes.

Studies the characteristics of the ocean bottom in Monterey Bay, California. Domination of chemoautotrophic bacteria and vesicomyid clams; Observation of benthic fauna in seeps; Ratios of stable carbon isotopes in clam tissues.