Infaunal macrobenthos off Cap Blanc, Spanish Sahara

Cap Blanc, Spanish Sahara is characterized by a nearshore benthic faunal province physically controlled by rates of sedimentation, conservatively estimated at 4 cm/yr, with a gradual transition across the continental shelf to a second province in a zone with high phytoplankton production of 2 gm C m-2 d-1 induced by upwelling at the continental shelf\u27s outer margin...

Nitrification and oxygen consumption in northwest Atlantic deep-sea sediments

The importance of nitrification in the oxygen consumption by deep-sea sediments was investigated by modelling pore water nitrate profiles from 6 northwest Atlantic cores. Total nitrification and denitrification rates were calculated from the thickness of the nitrification layer, the nitrification rate at the sediment surface (N), the coefficient of exponential decrease of the nitrification rate (B), and the first-order rate constant for denitrification. The four unknowns were determined by best fit of the model to the nitrate profiles. The nitrate profile from the furthest offshore station indicated no denitrification, so that only N and B were determined. Nitrification rates ranged from 150 × 10−6 to 3.86 × 10−6 nmole NH4+ cm−2 s− at the 1850 m and the 5105 m stations, respectively. As the oxygen consumption by nitrification could account for 35% of the published total oxygen consumption at these stations, nitrification represented a significant aerobic reaction in these deep-sea sediments. Ammonium sources included an upward ammonium flux from deeper anaerobic strata (6%) and aerobic respiration of organic matter (56%) with the remainder presumably supplied by anaerobic respiration within the oxygenated strata (38%). Nitrogen budgets based on sediment traps indicated that nitrification and burial rates agreed within a factor of 2 of sediment trap organic nitrogen fluxes. Also, 70% of the nitrogen that was nitrified or buried was returned as nitrate to the water column

The role of bacteria in the turnover of organic carbon in deep-sea sediments

The cycling of organic carbon in the deep sea was inferred from measurements of sediment trap and box core samples taken on the Biscay and Demerara abyssal plains of the North Atlantic. Of the input of organic carbon to the bottom, less than 10% was buried, i.e., not consumed biologically. Based on laboratory measurements of bacterial activity in the sediment samples, incubated under in situ temperature and pressure, it was possible to attribute at least 13 to 30% of the total inferred biological consumption of organic carbon to microbial utilization. The complementarity of results from these biochemical and microbiological measurements implies that the decompression of cold abyssal samples during retrieval efforts does not prevent meaningful experiments on the microbial inhabitants, once returned to in situ pressure

Sedimentation rates in the slope water of the northwest Atlantic Ocean measured directly with sediment traps

Four sedi ment trap arrays we re deployed in the Slope Water off the northeast United States for periods of 5.8 to 15.8 days from May to August 1976. Three traps, each a PVC cylinder 25 cm in diameter and 76 cm tall, were attached a t va rious distances above the bottom along bottom-anchored moorings. Closure of the individu al traps and release of each array from its expend able anchor was co ntrolled by a Williams Timed Release or an AMF acoustic release. DSRV ALVIN, making observations of one array, closed those traps and released that array from the bottom...

Benthic fauna of the Gulf of Maine sampled by R/V Gosnold Cruise 179 and DSRV Alvin Dives 329, 330, 331, and 404 : infaunal species list

Bottom samples were collected in the Gulf of Maine during July, 1971 and June, 1972 using DSRV ALVIN and RV GOSNOLD. The techniques and results are embodied in a paper entitled "Quantitative Biological Assessment of the Benthic Fauna in the Deep Basins of the Gulf of Maine" by G. T. Rowe, P. T. Polloni and R. L. Haedrich. Many of the conclusions made in that paper were based on summaries of the abundance of each benthic species of living invertebrate animal in each kind of sample, but those original data would not be accepted by the journal (JOURNAL OF THE FISHERIES RESEARCH BOARD OF CANADA) because the table was too long. The purpose of this technical report is to put those raw data in a form available(on request from the authors)to any interested ecologists.The work was supported by ONR Contract N00014 - 66 - C00284 and NSF Grant GA 31235X

Zonation and faunal composition of epibenthic populations on the continental slope south of New England

The epibenthic macrofauna, including demersal fishes, between 140 and 1900 m on the continental slope south of New England was found to be distributed in three zones: shallow (141-285 m), middle (393-1095 m), and deep (1270-1928 m). Fauna! boundaries were associated with the transition zones from shelf to upper continental slope and from upper to lower continental slope. The small Alvin Canyon was not faunally distinct. Fishes and echinoderms were the most abundant taxa, the former predominant in shallow and middle depths and the latter predominating deeper...

Categorizing zonal productivity on the continental shelf with nutrient-salinity ratios

Highlights Identifying riverine influence on productivity in the northern Gulf of Mexico Use of nutrient/salinity plots to differentiate inputs from two rivers Verifying Rowe-Chapman (2002) hypothesis with in situ data Abstract Coastal ocean productivity is often dependent on riverine sources of nutrients, yet it can be difficult to determine how far the influence of the river extends. The northern Gulf of Mexico (GOM) receives freshwater and nutrients discharged mainly from the Mississippi and Atchafalaya Rivers. We used nutrient/salinity relationships to (i) differentiate the nutrient inputs of the two rivers and (ii) determine the potential extent of the zones where productivity is affected by each. We identified three different zones: one close to the coast having a linear nutrient/salinity relationship where physical forcing (river flow) dominates, one offshore with nutrient (N or Si) concentrations \u3c1 μM, and one between them with variable nutrient concentrations largely controlled by consumption by autotrophs. While in the GOM salinity/nutrient relationships varied systematically with distance from the two rivers in winter, this was not seen in summer. Thus, the methodology is not always applicable directly, because the boundaries of the different regions vary with river flow, overall nutrient flux, and grids of stations at the regional spatial scale (15–20 km in the GOM), rather than single sections are needed to determine boundaries

Implications of different nitrogen input sources for potential production and carbon flux estimates in the coastal Gulf of Mexico (GOM) and Korean Peninsula coastal waters

The coastal Gulf of Mexico (GOM) and coastal sea off the Korean Peninsula (CSK) both suffer from human-induced eutrophication. We used a nitrogen (N) mass balance model in two different regions with different nitrogen input sources to estimate organic carbon fluxes and predict future carbon fluxes under different model scenarios. The coastal GOM receives nitrogen predominantly from the Mississippi and Atchafalaya rivers and atmospheric nitrogen deposition is only a minor component in this region. In the CSK, groundwater and atmospheric nitrogen deposition are more important controlling factors. Our model includes the fluxes of nitrogen to the ocean from the atmosphere, groundwater and rivers, based on observational and literature data, and identifies three zones (brown, green and blue waters) in the coastal GOM and CSK with different productivity and carbon fluxes. Based on our model results, the potential primary production rate in the inner (brown water) zone are over 2 gC m−2 d−1 (GOM) and 1.5 gC m−2 d−1 (CSK). In the middle (green water) zone, potential production is from 0.1 to 2 (GOM) and 0.3 to 1.5 gC m−2 d−1 (CSK). In the offshore (blue water) zone, productivity is less than 0.1 (GOM) and 0.3 (CSK) gC m−2 d−1. Through our model scenario results, overall oxygen demand in the GOM will increase approximately 21 % if we fail to reduce riverine N input, likely increasing considerably the area affected by hypoxia. Comparing the results from the USA with those from the Korean Peninsula shows the importance of considering both riverine and atmospheric inputs of nitrogen. This has direct implications for investigating how changes in energy technologies can lead to changes in the production of various atmospheric contaminants that affect air quality, climate and the health of local populations