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...

Tidal Turbine Benchmarking Exercise: Environmental Characterisation and Geometry Specification

Uncertainty in tidal turbine loading contributes significantly to conservatism in turbine design. This uncertainty originates not only from a lack of knowledge of the flow field at a particular site, but also from lack of understanding of the fundamental physics which govern the loading and performance of tidal turbines in unsteady and turbulent flow regimes. In order to reduce this conservatism and the costs associated, the mathematical and engineering models used in turbine design must be improved. To facilitate the development of these models requires scale experimental data for validation. However, few well-documented experimental data sets are available for tidal turbines, especially at scales large enough to achieve Reynolds number independence and comparability to full scale devices.This paper reports on the initial phases of a tidal turbine benchmarking project that will conduct a large laboratory scale experimental campaign on a highly instrumented 1.6m diameter tidal rotor. The turbine will be tested in well defined flow conditions, including unsteadiness created by free surface waves, as well as freestream turbulence, with instrumentation to determine edgewise and flapwise loading distributions along the blades as they rotate through the unsteady flows. As towing tanks by their nature have low levels of freestream turbulence, a carriage-mounted turbulence grid will be utilised to generate sufficient freestream turbulence in a well-defined manner.In this paper the turbine geometry and test conditions are specified, as well as providing details of the rotor’s hydrodynamic design process. Additionally, the results of a flow characterisation of the carriage-mounted turbulence grid via Acoustic Doppler Velocimetry are presented. The turbulence grid produced a mean turbulence intensity of 3:5% across the region in which the turbine will be tested, and a very uniform flow profile of 0:913 times the upstream velocity

Once and Future Gulf of Mexico Ecosystem: Restoration Recommendations of an Expert Working Group

The Deepwater Horizon (DWH) well blowout released more petroleum hydrocarbons into the marine environment than any previous U.S. oil spill (4.9 million barrels), fouling marine life, damaging deep sea and shoreline habitats and causing closures of economically valuable fisheries in the Gulf of Mexico. A suite of pollutants—liquid and gaseous petroleum compounds plus chemical dispersants—poured into ecosystems that had already been stressed by overfishing, development and global climate change. Beyond the direct effects that were captured in dramatic photographs of oiled birds in the media, it is likely that there are subtle, delayed, indirect and potentially synergistic impacts of these widely dispersed, highly bioavailable and toxic hydrocarbons and chemical dispersants on marine life from pelicans to salt marsh grasses and to deep-sea animals. As tragic as the DWH blowout was, it has stimulated public interest in protecting this economically, socially and environmentally critical region. The 2010 Mabus Report, commissioned by President Barack Obama and written by the secretary of the Navy, provides a blueprint for restoring the Gulf that is bold, visionary and strategic. It is clear that we need not only to repair the damage left behind by the oil but also to go well beyond that to restore the anthropogenically stressed and declining Gulf ecosystems to prosperity-sustaining levels of historic productivity. For this report, we assembled a team of leading scientists with expertise in coastal and marine ecosystems and with experience in their restoration to identify strategies and specific actions that will revitalize and sustain the Gulf coastal economy. Because the DWH spill intervened in ecosystems that are intimately interconnected and already under stress, and will remain stressed from global climate change, we argue that restoration of the Gulf must go beyond the traditional "in-place, in-kind" restoration approach that targets specific damaged habitats or species. A sustainable restoration of the Gulf of Mexico after DWH must: 1. Recognize that ecosystem resilience has been compromised by multiple human interventions predating the DWH spill; 2. Acknowledge that significant future environmental change is inevitable and must be factored into restoration plans and actions for them to be durable; 3. Treat the Gulf as a complex and interconnected network of ecosystems from shoreline to deep sea; and 4. Recognize that human and ecosystem productivity in the Gulf are interdependent, and that human needs from and effects on the Gulf must be integral to restoration planning. With these principles in mind, the authors provide the scientific basis for a sustainable restoration program along three themes: 1. Assess and repair damage from DWH and other stresses on the Gulf; 2. Protect existing habitats and populations; and 3. Integrate sustainable human use with ecological processes in the Gulf of Mexico. Under these themes, 15 historically informed, adaptive, ecosystem-based restoration actions are presented to recover Gulf resources and rebuild the resilience of its ecosystem. The vision that guides our recommendations fundamentally imbeds the restoration actions within the context of the changing environment so as to achieve resilience of resources, human communities and the economy into the indefinite future