Ecosystem responses to recent oceanographic variability in high-latitude Northern Hemisphere ecosystems

As part of the international MENU collaboration, we compared and contrasted ecosystem responses to climate-forced oceanographic variability across several high latitude regions of the North Pacific (Eastern Bering Sea (EBS) and Gulf of Alaska (GOA)) and North Atlantic Oceans (Gulf of Maine/Georges Bank (GOM/GB) and the Norwegian/Barents Seas (NOR/BAR)). Differences in the nitrate content of deep source waters and incoming solar radiation largely explain differences in average primary productivity among these ecosystems. We compared trends in productivity and abundance at various trophic levels and their relationships with sea-surface temperature. Annual net primary production generally increases with annual mean sea-surface temperature between systems and within the EBS, BAR, and GOM/GB. Zooplankton biomass appears to be controlled by both top-down (predation by fish) and bottom-up forcing (advection, SST) in the BAR and NOR regions. In contrast, zooplankton in the GOM/GB region showed no evidence of top-down forcing but appeared to control production of major fish populations through bottom-up processes that are independent of temperature variability. Recruitment of several fish stocks is significantly and positively correlated with temperature in the EBS and BAR, but cod and pollock recruitment in the EBS has been negatively correlated with temperature since the 1977 shift to generally warmer conditions. In each of the ecosystems, fish species showed a general poleward movement in response to warming. In addition, the distribution of groundfish in the EBS has shown a more complex, non-linear response to warming resulting from internal community dynamics. Responses to recent warming differ across systems and appear to be more direct and more pronounced in the higher latitude systems where food webs and trophic interactions are simpler and where both zooplankton and fish species are often limited by cold temperatures.     

PCB resistance within phytoplankton populations in polluted and unpolluted marine environments

A comparison between clones of two species of diatoms, Asterionella japonica and Ditylum brightwellii, isolated from Sandy Hook, New Jersey (polluted site) and Montauk, New York (unpolluted site) indicated that some of the clones from Sandy Hook were more resistant to polychlorinated biphenyls (PCB). A japonica was less sensitive to PCB than D. brightwellii since seven clones of A. japonica from both sites were tolerant of 25 μg litre^?1 PCB whereas no clones from either site of D. brightwellii showed such resistance. Growth under high light intensity increased the sensitivity to PCB in all clones except one super-resistant clone from Sandy Hook which was not affected even by additions of 50 μg litre^?1 to the growth medium. This interactive effect of light on PCB sensitivity may relate to the photo-adaptive characteristics of each clone.     

Selected chemical contaminants in surface sediments of Commencement Bay and the Tacoma Waterways, Washington, USA

Eight metals, 21 organic priority pollutants, and 11 other contaminants and contaminant-related sediment characteristics were measured in surface sediments (upper 2 cm) at 21 locations in Commencement Bay and the Tacoma Waterways, Washington. Summary statistics were calculated and statistical approaches (analysis of variance, multiple comparisons tests, cluster analysis and principal component analysis) were applied to subsets of the data to classify sediment contamination. Overall sediment contamination was highest in the Sitcum, City and Hylebos Waterways, intermediate in Commencement Bay, at the entrances to the Tacoma Waterways and in the outer reaches of the Blair and Hylebos Waterways, and lowest at the Blair Waterway turning basin, the mouth of the Puyallup River and at a reference site near Browns Point. High concentrations of some contaminants appeared to be related to proximity to sources of contaminants. Depositional vectors, and chemical adsorption processes may also influence the spatial distribution of sediment contamination in the study area.Results of simple and partial correlation analyses indicate that arsenic, iron and manganese may be more closely associated with the clay fraction, while cadmium, copper and polynuclear aromatic hydrocarbons may be more closely associated with the total organic carbon content of sediments. We were unable to discriminate statistically between the affinity of chromium, lead, zinc and phthalates with the % clay or the total organic carbon content of sediments.     

Dispersion of bauxitic red mud in the Gulf of Corinth, Greece

Bauxitic red-mud slurry, discharged by an aluminium processing factory on the shelf of the Gulf of Corinth, Greece, is used as a tracer to examine sediment transport and dispersion processes in a tectonically active deep basin.

The Gulf of Corinth is a silled elongate basin with a maximum depth of 860 m; it is characterised by high seismicity. The red mud is discharged through a pipeline at a depth of 100 m, where it forms an extensive deposit.

Grab sampling has shown that the red mud extends over the slope and the abyssal plain up to a distance of 17 km from the mouth of the pipeline. It forms small scattered sheet-like deposits of up to 3 cm in thickness. The structures observed in the scattered patches of the red mud, which in some places are overlain by a thin veneer of grey/olive green (natural) sediments, suggest that the red mud is transported from the shelf to the abyssal plain by gravitative sediment flows. The flows are triggered by earthquakes.

Granulometric and geochemical analyses of the red-mud samples show that the red mud, during its transport from the shelf to the abyssal plain, is subjected to mixing with the surrounding sediments. A different mixing ratio is determined, however, by reference to the various trace metals (Fe, Ni, Co, Pb).     

Biochemical and ultrastructural observations of long-term silver accumulation in the mussel, Mytilus edulis

The cellular distribution and chemical forms of Ag were determined in mussels after accumulation of the metal from sea water. The major accumulations were either in the vacuoles of connective tissue macrophages, where it was associated with S, or in deposits in the fibrillar layer of the basement membranes of the digestive diverticulum and kidney epithelia, where it was bound to the sulphydryl and sulphate groups of glycoproteins and proteoglycans. In acutely exposed animals, about 10 % of the accumulated Ag was found in a (Ag, Cu)-binding protein with characteristics indicating that it may be a metallothionein. There was a concomitant increase in the body Cu levels after Ag exposure and 40 % of this was bound to this low molecular weight metal-binding protein.     

The US freedom of navigation program preserving the law of the sea

The 1982 United Nations Convention on the Law of the Sea prescribed extensive rules of behavior for the international community in the oceanic regime. Some of the most important provisions of the Convention are those regarding the freedom of navigation and overflight in various maritime zones, i.e. territorial seas, international straits, archipelagos, exclusive economic zones and the high seas.While most coastal nations are complying with the navigation and overflight provisos of the Convention, some are not. Where excessive maritime claims exist, the US has evolved an ambitious Freedom of Navigation (FON) Program which challenges these excessive claims. This Program was initiated under the Carter Administration in 1979 and has continued, unabated, ever since.As the international community prepares for the day when the 1982 Convention becomes universally-recognized international law, there are likely to be periodic excessive maritime claims. In cases where the Convention's dispute settlement provisos fail to resolve excessive claims, the community of nations may find it useful to use the US FON Program as an example for the enforcement of maritime rules.     

Current-generated noise recorded on ocean bottom seismometers

High-amplitude, anrrow band noise that correlates with periods of high ocean bottom currents and the tidal cycle is occasionally observed on ocean bottom seismometers (OBS). The geophones on OBSs of different configurations are not equally sensitive to this noise and hydrophones are almost unaffected. With a suitable design, it should be possible to eliminate this noise problem.Hawaii Institute of Geophysics Contribution No. 1173     

A comparative study of the differential blood cell counts of winter flounder (Pseudopleuronectes americanus) collected in New England

Major alterations in the distribution of peripheral blood cells were observed among winter flounder (Pseudopleuronectes americanus) from Martha's Vineyard (MV), East Cape Cod Bay (ECCB), Fox Island (FI) (Narragansett Bay), Central Long Island Sound (CLIS), Gaspee Point (GP) (Narragansett Bay), Black Rock Harbor (BRH) (Bridgeport, CT), New Bedford Harbor (NBH) and Quincy Bay (QB) (Boston Harbor). Collection locations ranged from relatively uncontaminated offshore (MV) and nearshore (ECCB) sites to the more contaminated estuarine (FI, CLIS) and urban embayments (GP, BRH, NBH, QB). Differential diagnosis demonstrated a shift in lymphocyte counts from 28% (MV) to 54% (QB) that increased with the incidence of liver lesions in relation to known and suspected levels of sediment chemical contamination. A significant change in the ratio of circulating immature to mature erythrocytes was observed in flounder collected from Boston Harbor. Immature erythrocytes comprised 18% of the total erythrocyte population of fish from QB in comparison to 6% observed in flounder from ECCB.     

Numerical Simulation of the Gulf Stream and the Deep Circulation

The Gulf Stream system has been numerically simulated with relatively high resolution and realistic forcing. The surface fluxes of the simulation were obtained from archives of calculations from the Eta-29 km model which is an National Center for Environment Prediction (NCEP) operational atmospheric prediction model; synoptic fields are available every 3 hour. A comparison between experiments with and without surface fluxes shows that the effect of the surface wind stress and heat fluxes on the Gulf Stream path and separation is closely related to the intensification of deep circulations in the northern region. Additionally, the separation of the Gulf Stream and the downslope movement of the Deep Western Boundary Current (DWBC) are reproduced in the model results. The model DWBC crosses under the Gulf Stream southeast of Cape Hatteras and then feeds the deep cyclonic recirculation east of the Bahamas. The model successfully reproduces the cross-sectional vertical structures of the Gulf Stream, such as the asymmetry of the velocity profile, and this structure is sustained along the downstream axis. The distribution of Root Mean Square (RMS) elevation anomaly of the model shows that the eddy activity of the Gulf Stream is realistically reproduced by the model physics. The entrainment of the upper layer slope current into the Gulf Stream occurs near cross-over; the converging cross-stream flow is nearly barotropic. This revised version was published online in August 2006 with corrections to the Cover Date.