SEARCH · Search USGS

Results for “Deep-Sea Research Part II: Topical Studies in Oceanography”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources

USGS1994

210Pb balance and implications for particle transport on the continental shelf, U.S. Middle Atlantic Bight

Supply of 210 Pb to the continental shelf off the northeastern United States is dominated by the deposition from the atmosphere, the rate of which is reliably known from previously published work. Excess 210 Pb inventories in the shelf sediments show accumulations that are nearly in balance with the supply, even in areas of relict sands where it is believed that no net accumulation of sediment presently occurs. The 210 Pb distributions in shelf and slope water indicate that the two-way fluid exchange at the shelf-slope front and the net transport in the alongshore flow make comparatively small contributions to the shelf 210 Pb budget. The near balance between supply and decay of 210 Pb on the shelf implies a limit to the particle export flux. It is concluded that the export of particulate organic carbon does not exceed 60 g m −2 y −1 (&sim;25% of primary production) and is probably lower. The hypothesis is advanced that fine particulate matter introduced to the continental shelf is detained in its transit of the shelf because of bioturbational trapping in the sediment due to benthic animals. Distributions of 210 Pb in suspended particulate matter and in the fine fraction of shelf sediments suggest that the average fine particle must undergo several cycles of deposition-bioturbation-resuspension-redeposition and requires a number of decades for its transit and ultimate export from the shelf. Thus, only the most refractory organic matter is likely to be exported.

Middle Atlantic Bight↗

USGS2023

Habitat utilization, demography, and behavioral observations of the squat lobster, Eumunida picta (Crustacea: Anomura: Eumunididae), on western North Atlantic deep-water coral habitats

Deep-sea coral habitats, comprising mostly Lophelia pertusa (Linnaeus 1758), are well developed on the upper and middle continental slope off the southeastern United States (SEUS). These habitats support a diverse and abundant invertebrate fauna, yet ecology and biology of most of these species are poorly known. Ten cruises conducted off the SEUS (Summer–Fall; Cape Lookout, NC–Cape Canaveral, FL) from 2000 to 2005, and in 2009 provided an opportunity to investigate abundance and distribution of Eumunida picta Smith1883, a large-sized species of squat lobster commonly associated with these deep-water coral habitats. Video analysis from 70 manned-submersible dives documented occurrence, density, location on the coral colony, and behavioral observations for 5774 individuals of E . picta . Individuals collected (n = 178) from coral and adjacent habitats (e.g., rubble, soft sediments) were measured and their sex determined. Males and females were comparable in size (to 53.5 mm carapace length) and exhibited a sex ratio of approximately 1:1. Eumunida picta were most frequently observed as solitary individuals on high-profile coral matrix and were noted only infrequently on coral rubble, or rarely on soft substratum. Presence of coral habitat (i.e., live/dead L. pertusa ), geographic region within the sampling area, and depth significantly influenced abundances of E. picta . Additionally, coral habitat (dead versus live coral), vertical position on the coral (upper, middle, or lower zone), as well as horizontal position in relation to the coral matrix (outer surface versus embedded in coral matrix) were significant factors influencing E. picta distributions within the coral habitat. More individuals were found on dead versus live coral, and most frequently occurred on the outer surfaces of coral branches located on the upper portion or near the tops of coral colonies. Eumunida picta were most often observed with claws extended into the water column. This unique hunting stance provides this squat lobster the opportunity to capture prey from the water column. An active predator, this species utilizes both pelagic (i.e., fishes, pyrosomes) and benthic (e.g., scavenging and grazing) food resources, and may function as an important trophic link between the water column and the benthos. Although considered a facultative reef associate in the strictest sense of the term, E. picta has a complex and intimate relationship with L. pertusa . Based on observations from dive videos, E. picta is a dominant and ecologically important member of the invertebrate assemblage associated with deep-sea coral habitats off the SEUS. As such, this species figures prominently in the structure and function of this ecosystem.

western North Atlantic↗

USGS2004

The distribution of seabirds and pinnipeds in Marguerite Bay and their relationship to physical features during austral winter 2001

The distribution of seabirds and pinnipeds and their relationship to physical oceanographic variables were investigated as part of the US Southern Ocean Global Ocean Ecosystem Dynamics field program along a study grid centered around Marguerite Bay on the west Antarctic Peninsula during late fall (April-May) and winter (July-August), 2001. Sea-ice conditions during the cruises provided an opportunity to compare the relationship among physical oceanographic variables and species distributions before and after the development of pack ice. During the fall cruise before pack ice development, both sea-ice-affiliated species and open-water-affiliated were observed in the area. The most common ice-affiliated species observed at this time were snow petrel (Pagodroma nivea, 0.7 individuals km-2) and Antarctic petrel (Thalassoica antarctica, 0.2 individuals km-2) and the most common open-water-affiliated species were blue petrel (Halobaena caerulea, 0.4 individuals km-2), cape petrel (Daption capense, 0.2 individuals km-2), and southern fulmar (Fulmarus glacialoides, 0.1 individuals km-2). In addition, Antarctic fur seals (Arctocephalus gazella, 0.1 individuals km-2) and crabeater seals (Lobodon carcinophagus, 0.4 individuals km-2) were observed in low numbers. Akaike's information criterion was used to assess competing models that predicted predator distributions based on physical oceanographic variables proposed to structure predator distribution in previous research. These analyses indicated that predator distributions were primarily associated with water-mass structure and variability in bottom depth during the fall cruise. Crabeater seal, snow petrel, Antarctic petrel, and southern fulmar had higher densities in Inner Shelf Water, particularly near Alexander Island where a coastal current was present. Blue petrel, kelp gull (Larus dominicanus), and southern giant petrel (Macronectes giganteus) were positively associated with variability in bottom depth in April-May, suggesting that hydrographic processes influenced by bathymetry may have been important in structuring bird distributions. After the development of pack ice, during July and August, only sea-ice-affiliated species, including snow petrel (1.0 individuals km-2), Antarctic petrel (0.1 individuals km-2), Ade??lie penguin (Pygoscelis adeliae, 0.4 individuals km-2), and crabeater seal (0.3 individuals km-2), were observed. Seabirds were primarily associated with sea-ice characteristics (e.g. sea-ice concentration, sea-ice type) rather than the water-column environment later in the winter. Results from this study suggest that the timing and extent of sea-ice development in the fall may influence over-winter predation by seabirds and pinnipeds on zooplankton and fish on the western Antarctic Peninsula. Delays in sea-ice development may allow seabirds and pinnipeds access to biologically important areas such as the Inner Shelf Water for a longer period of time thereby increasing predation on zooplankton and fish. ?? 2004 Elsevier Ltd. All rights reserved.

Deep-Sea Research Part II: Topical Studies in Ocea↗

USGS2005

The kinematic and hydrographic structure of the Gulf of Maine Coastal Current

The Gulf of Maine Coastal Current (GMCC), which extends from southern Nova Scotia to Cape Cod Massachusetts, was investigated from 1998 to 2001 by means of extensive hydrographic surveys, current meter moorings, tracked drifters, and satellite-derived thermal imagery. The study focused on two principal branches of the GMCC, the Eastern Maine Coastal Current (EMCC) that extends along the eastern coast of Maine to Penobscot Bay, and the Western Maine Coastal Current (WMCC) that extends westward from Penobscot Bay to Massachusetts Bay. Results confirm that GMCC is primarily a pressure gradient-driven system with both principal branches increasing their transport in the spring and summer due to fresh-water inflows, and flowing southwestward against the mean wind forcing during this period. In the spring and summer the subtidal surface currents in the EMCC range from 0.15 to 0.30 ms −1 while subtidal WMCC currents range from 0.05 to 0.15 ms −1 . The reduction of southwestward transport near Penobscot Bay is accomplished via an offshore veering of a variable portion of the EMCC, some of which recirculates cyclonically within the eastern Gulf of Maine. The degree of summer offshore veering, versus leakage into the WMCC, varied strongly over the three study years, from nearly complete disruption in 1998 to nearly continuous through-flow in 2000. Observations show strong seasonal and interannual variability in both the strength of the GMCC and the degree of connectivity of its principal branches.

Gulf of Maine, Jordan Basin↗

USGS2006

Predictable hotspots and foraging habitat of the endangered short-tailed albatross (Phoebastria albatrus) in the North Pacific: Implications for conservation

The short-tailed albatross ( Phoebastria albatrus ) is a rare and endangered seabird that ranges widely over the northern North Pacific. Populations are slowly recovering but birds face several threats at sea, in particular the incidental capture of birds in long-line fisheries. Conservation efforts are hampered by a lack of information about the at-sea distribution of this species, especially knowledge of where it may predictably co-occur with long-line fishing effort. During 18 years of transiting the Aleutian Islands Unit of the Alaska Maritime National Wildlife Refuge on a research vessel, we observed short-tailed albatross on 65 occasions. They were consistently observed near Ingenstrem Rocks (Buldir Pass) in the western Aleutians and near Seguam Pass in the central Aleutians. Based on the oceanographic characteristics of the locations where we saw most of the birds, we hypothesized that short-tailed albatross “hotspots” were located where tidal currents and steep bottom topography generate strong vertical mixing along the Aleutian Archipelago. As a test of this hypothesis, we analyzed a database containing 1432 opportunistic observations of 2463 short-tailed albatross at sea in the North Pacific. These data showed that short-tailed albatross were closely associated with shelf-edge habitats throughout the northern Gulf of Alaska and Bering Sea. In addition to Ingenstrem Rocks and Seguam Pass, important hotspots for short-tailed albatross in the Aleutians included Near Strait, Samalga Pass, and the shelf-edge south of Umnak/Unalaska islands. In the Bering Sea, hotspots were located along margins of Zhemchug, St. Matthews and Pervenets canyons. Because these short-tailed albatross hotspots are predictable, they are also protectable by regulation of threatening activities at local spatial scales.

Deep-Sea Research Part II: Topical Studies in Ocea↗

USGS2006

Foraging destinations and marine habitat use of short-tailed albatrosses: A multi-scale approach using first-passage time analysis

We used satellite telemetry, remotely sensed data (bathymetry, chlorophyll a (chl a), sea-surface temperature (SST), wind speed) and first-passage time (FPT) analysis to determine the distribution, movement patterns, and habitat associations of short-tailed albatrosses (Phoebastria albatrus) during the non-breeding season, 2002 and 2003. Satellite transmitters were deployed on birds immediately prior to their departure from a breeding colony at Torishima, Japan (n = 11), or at-sea in the Aleutian Islands (n = 3). Tracking durations ranged from 51 to 138 days for a total of 6709 locations after filtering (131 - 808 per bird). FPT (time required to transit a circle of given radius) revealed the location and spatial scale of area-restricted search (ARS) patterns along flight paths. On average, ARS occurred within 70 km radii. Consequently, the fit of the habitat use models increased at spatial scales beyond a 40 km FPT radius (R2 = 0.31) and stabilized for scales of 70 km and larger (R2=0.40- 0.51). At all scales, wind speed, depth or depth gradient, and chl a or chl a gradient had a significant effect on FPT (i.e., residence time). FPT increased within regions of higher gradients of depth and chl a. In contrast, FPT decreased within regions of greater depth and wind speed, with a significant interaction of wind speed and depth at some scales. Sea-surface temperature or its interactions were only significant at large spatial scales (???160 km FPT radius). Albatrosses engaged in ARS activities primarily over the shelf break and slope, including Kuroshio and Oyashio regions off the western subarctic gyre. Occasionally, birds transited the northern boundary of the Kuroshio Extension while in-route to the Aleutian Islands and Bering Sea, but overall spent little time in the western gyre. In the Aleutian Islands, ARS occurred within straits, particularly along the central and western part of the archipelago. In the Bering Sea, ARS occurred along the northern continental shelf break, the Kamchatka Current region, and east of the Commander Islands. Non-breeding short-tailed albatross concentrate foraging in oceanic areas characterized by gradients in topography and water column productivity. This study provides an understanding of the foraging ecology for a highly migratory, imperiled seabird, and confirms the importance of shelf break and slope regions as hot spots for a variety of top marine predators in the North Pacific.

Deep-Sea Research Part II: Topical Studies in Ocea↗

USGS2007

Individual dietary specialization and dive behaviour in the California sea otter: Using archival time-depth data to detect alternative foraging strategies

The existence of individual prey specializations has been reported for an ever-growing number of taxa, and has important ramifications for our understanding of predator-prey dynamics. We use the California sea otter population as a case study to validate the use of archival time-depth data to detect and measure differences in foraging behaviour and diet. We collected observational foraging data from radio-tagged sea otters that had been equipped with Mk9 time depth recorders (TDRs, Wildlife Computers, Redmond, WA). After recapturing the study animals and retrieving the TDRs it was possible to compare the two data types, by matching individual dives from the TDR record with observational data and thus examining behavioural correlates of capture success and prey species. Individuals varied with respect to prey selection, aggregating into one of three distinct dietary specializations. A number of TDR-derived parameters, particularly dive depth and post-dive surface interval, differed predictably between specialist types. A combination of six dive parameters was particularly useful for discriminating between specialist types, and when incorporated into a multivariate cluster analysis, these six parameters resulted in classification of 13 adult female sea otters into three clusters that corresponded almost perfectly to the diet-based classification (1 out of 13 animals was misclassified). Thus based solely on quantifiable traits of time-depth data that have been collected over an appropriate period (in this case 1 year per animal), it was possible to assign female sea otters to diet type with >90% accuracy. TDR data can thus be used as a tool to measure the degree of individual specialization in sea otter populations, a conclusion that will likely apply to other diving marine vertebrates as well. Our ultimate goals must be both to understand the causes of individual specialization, and to incorporate such variation into models of population- and community-level food web dynamics. ?? 2007 Elsevier Ltd. All rights reserved.

Deep-Sea Research Part II: Topical Studies in Ocea↗

USGS2007

Authigenic carbonate formation at hydrocarbon seeps in continental margin sediments: A comparative study

Authigenic carbonates from five continental margin locations, the Eel River Basin, Monterey Bay, Santa Barbara Basin, the Sea of Okhotsk, and the North Sea, exhibit a wide range of mineralogical and stable isotopic compositions. These precipitates include aragonite, low- and high-Mg calcite, and dolomite. The carbon isotopic composition of carbonates varies widely, ranging from −60‰ to +26‰, indicating complex carbon sources that include 13 C-depleted microbial and thermogenic methane and residual, 13 C-enriched, bicarbonate. A similarly large variability of δ 18 O values (−5.5‰ to +8.9‰) demonstrates the geochemical complexity of these sites, with some samples pointing toward an 18 O-enriched oxygen source possibly related to advection of 18 O-enriched formation water or to the decomposition of gas hydrate. Samples depleted in 18 O are consistent with formation deeper in the sediment or mixing of pore fluids with meteoric water during carbonate precipitation. A wide range of isotopic and mineralogical variation in authigenic carbonate composition within individual study areas but common trends across multiple geographic areas suggest that these parameters alone are not indicative for certain tectonic or geochemical settings. Rather, the observed variations probably reflect local controls on the flux of carbon and other reduced ions, such as faults, fluid conduits, the presence or absence of gas hydrate in the sediment, and the temporal evolution of the local carbon reservoir. Areas with seafloor carbonates that indicate formation at greater depth below the sediment–water interface must have undergone uplift and erosion in the past or are still being uplifted. Consequently, the occurrence of carbonate slabs on the seafloor in areas of active hydrocarbon seepage is commonly an indicator of exhumation following carbonate precipitation in the shallow subsurface. Therefore, careful petrographic and geochemical analyses are critical components necessary for the correct interpretation of processes related to hydrocarbon seepage in continental margin environments and elsewhere.

Deep-Sea Research Part II: Topical Studies in Ocea↗

USGS2007

Barite-forming environments along a rifted continental margin, Southern California Borderland

The Southern California Continental Borderland (SCCB) is part of the broad San Andreas transform-fault plate boundary that consists of a series of fault-bounded, petroleum-generating basins. The SCCB has high heat flow and geothermal gradients produced by thinned continental crust and Neogene volcanism. Barite deposits in the SCCB occur along faults. Barite samples from two sea-cliff sites and four offshore sites in the SCCB were analyzed for mineralogy, chemical (54 elements) and isotopic (S, Sr) compositions, and petrography. Barite from Palos Verdes (PV) Peninsula sea-cliff outcrops is hosted by the Miocene Monterey Formation and underlying basalt; carbonate rocks from those outcrops were analyzed for C, O, and Sr isotopes and the basalt for S isotopes. Cold-seep barite from Monterey Bay, California was analyzed for comparison. SCCB offshore samples occur at water depths from about 500 to 1800 m. Those barites vary significantly in texture and occurrence, from friable, highly porous actively growing seafloor mounds to dense, brecciated, vein barite. This latter type of barite contrasts with cold-seep barite in being much more coarse grained, forms thick veins in places, and completely replaced rock clasts in breccia. The barite samples range from 94 to 99 wt% BaSO4, with low trace-element contents, except for high Sr, Zr, Br, U, and Hg concentrations compared to their crustal abundances. δ34S for SCCB offshore barites range from 21.6‰ to 67.4‰, and for PV barite from 62‰ to 70‰. Pyrite from PV sea-cliff basalt and sedimentary rocks that host the barites averages 7.8‰ and 2.2‰, respectively. Two offshore barite samples have δ34S values (21.6‰, 22.1‰) close to that of modern seawater sulfate, whereas all other samples are enriched to strongly enriched in 34S. 87Sr/86Sr ratios for the barites vary over a narrow range of 0.70830–0.70856 and are much lower than that of modern seawater and also lower than the middle Miocene seawater ratio, the time of deposition of the host rocks for the PV samples. This indicates that the mineralizing fluids were not unaltered seawater. We develop a model in which the barites precipitated both below the sediment–water interface and at the seafloor from low-temperature fluids that circulated along faults. The isotopic, chemical, and textural data indicate that the barites formed by several processes. Mesozoic and Cenozoic basement rocks (crystalline and overlying sedimentary rocks), Quaternary basin fill, turbidite fans, and seawater provided various elements for the barites in different environments. The fluids had a deep-seated source and were hydrothermal in the deeper parts of the system for all the barite types, including the seafloor cold-seep deposit, based on Sr isotopes and regional geothermal gradients. These deep-seated fluids mixed with other fluids as they ascended, including seawater at and near the seafloor. The high δ34S values may have resulted from extreme Rayleigh fractionation during bacterially mediated (semi)closed-system sulfate reduction, probably driven by the flux of methane- and hydrocarbon-bearing fluids through basement rocks and basin sediments. Early diagenetic dolomite and pyrite in the host Monterey Formation in the PV Headland also formed in a zone of sulfate reduction, but within sediment buried only centimeters to a few meters and with a predominantly seawater source for the sulfur. Dolomite occurring with vein barite in the PV Headland formed at temperatures in the range of 40–90 °C. The cold-seep barites have δ34S values near that of modern seawater, although still somewhat fractionated. The barites that precipitated below the sediment–water interface have higher δ34S values, suggesting that the fluids were relatively reduced with molar dissolved barium in excess of dissolved sulfate. Those samples were exposed at the seafloor by uplift along faults and are composed predominantly of massive, brecciated, and vein barite.

California↗

USGS2008

Contrasting population trends of piscivorous seabirds in the Pribilof Islands: A 30-year perspective

The Pribilof Islands provide nesting habitat for one of the largest concentrations of piscivorous seabirds in the North Pacific region. Pribilof breeding populations of black-legged and red-legged kittiwakes (Rissa tridactyla and Rissa brevirostris), and common and thick-billed murres (Uria aalge and Uria lomvia) are supported by a highly productive marine food web. Productivity and temperature in this area are influenced by winter sea ice that frequently reaches its maximum extent near the Pribilofs. Although St. George and St. Paul islands, the two largest of the Pribilof group, are situated only 60 km apart, St. George is within 25 km of the shelf break, but St. Paul is approximately 90 km away. In contrast, the local contribution of sea ice-edge productivity in the spring is frequently closer to St. Paul than to St. George. Central place foraging piscivorous seabirds nesting at St. Paul and St. George are likely differentially affected by the relative contributions of the shelf break and ice-edge environments based on juxtaposition. Within the past decade or so, sea ice in the Bering Sea has failed to reach the vicinity of the Pribilofs in some years, and predictions of warming in the future suggest the possibility that direct effects of the ice on the immediate Pribilof environment will be reduced. To evaluate the response of kittiwakes and murres on the two islands to conditions in their foraging environments, we examined population trends over the past 30 years based on data from the seabird monitoring program conducted by the Alaska Maritime National Wildlife Refuge and others. Spatial differences in trends have been more consistent than differences among species, with populations at St. Paul having more enduring declines than those at St. George. At St. George, black-legged kittiwakes and common murres have remained stable. Red-legged kittiwakes and thick-billed murres both declined, but began to rebound in the late 1980s, such that in 2005 population numbers for all four species at St. George were approximately equivalent to those observed in 1976. In contrast, at St. Paul Island, all four species have declined for most of this 30-year time series, with only black-legged kittiwakes showing increases in the past decade but still remaining far below 1976 numbers. Interestingly, rates of productivity for kittiwakes and for murres were similar between the two islands, suggesting similar responses to summer conditions and implicating differential mortality of post-fledging juveniles or adults from the two islands (i.e., if summer food stress was insufficient to cause differences in productivity, but sufficient to cause physiological consequences that reduced survival. Another possibility is immigration from St. Paul to St. George, probably by juveniles. ?? 2008 Elsevier Ltd.

Deep-Sea Research Part II: Topical Studies in Ocea↗

USGS2009

Bioenergetic model estimates of interannual and spatial patterns in consumption demand and growth potential of juvenile pink salmon (Oncorhynchus gorbuscha) in the Gulf of Alaska

A bioenergetic model of juvenile pink salmon (Oncorhynchus gorbuscha) was used to estimate daily prey consumption and growth potential of four ocean habitats in the Gulf of Alaska during 2001 and 2002. Growth potential was not significantly higher in 2002 than in 2001 at an alpha level of 0.05 (P=0.073). Average differences in growth potential across habitats were minimal (slope habitat=0.844 g d -1 , shelf habitat=0.806 g d -1 , offshore habitat=0.820 g d -1 , and nearshore habitat=0.703 g d -1 ) and not significantly different (P=0.630). Consumption demand differed significantly between hatchery and wild stocks (P=0.035) when examined within year due to the interaction between hatchery verses wild origin and year. However, the overall effect of origin across years was not significant (P=0.705) due to similar total amounts of prey consumed by all juvenile pink salmon in both study years. We anticipated that years in which ocean survival was high would have had high growth potential, but this relationship did not prove to be true. Therefore, modeled growth potential may not be useful as a tool for forecasting survival of Prince William Sound hatchery pink salmon stocks. Significant differences in consumption demand and a two-fold difference in nearshore abundance during 2001 of hatchery and wild pink salmon confirmed the existence of strong and variable interannual competition and the importance of the nearshore region as being a potential competitive bottleneck.

Deep-Sea Research Part II: Topical Studies in Ocea↗

USGS2009

A mosaic of diverse ideas: The ecological legacy of J. Frederick Grassle

During the 40 years (and counting) of his scientific career, J. Frederick Grassle has made fundamental contributions to our understanding of marine ecosystems from coral reefs to deep-sea sediments. His advocacy and passion for marine biodiversity in the form of myriad groundbreaking studies and influential reviews, his generosity of ideas and capacity to catalyze and inspire those working with him as well as the science community in general, his breakthroughs in improved ocean observation, his marine science infrastructure initiatives, together with his tireless persistence, have helped lead to major shifts in approaches to marine science and the shape of modern ocean studies to one that favours multidisciplinary research, teamwork, continuous, long-term observation, in situ experimentation, recognition of the importance of marine biodiversity, and global cooperation on research and data sharing. In shallow-water ecology, he co-discovered sibling species of Capitella spp., important not only because it is a key pollution indicator but also because the work helped to pave the way for the discovery of numerous sibling species in other taxa with major ramifications for ecological understanding. He was also a key player in the West Falmouth oil spill study which, along with complementary mesocosm experiments, remains one of the most important and detailed studies of its kind. He was also a lead player in the first biological expedition to hydrothermal vents and wrote the seminal articles that helped to inspire the flurry of vent research that followed. He is perhaps best known for his deep-sea work, where he brought submersibles to the forefront as a sampling tool, brought experimental manipulative studies to the primarily descriptive discipline of deep-sea benthic ecology, and generated tremendous excitement, debate, and rekindled interest in marine biodiversity with the first quantitative estimate of global deep-sea diversity. His efforts to document marine biodiversity resulted in the international Census of Marine Life, and his emphasis on the need for continuous, long-term ocean observation has led to breakthroughs in international cooperation in cabled observatories such as LEO-15. These efforts have also enhanced efforts to integrate ocean data on a global scale in platforms such as the Ocean Biogeographic Information System (OBIS). The diversity of his contributions to marine science mirror the immense marine diversity he has recognized, documented, and championed so effectively over the last four decades.

Deep-Sea Research Part II: Topical Studies in Ocea↗

USGS2009

Recolonization of gravel habitats on Georges Bank (northwest Atlantic)

Gravel habitats on continental shelves around the world support productive fisheries but are also vulnerable to disturbance from bottom fishing. We conducted a 2-year in situ experiment to measure the rate of colonization of a gravel habitat on northern Georges Bank in an area closed to fishing (Closed Area II) since December 1994. Three large (0.25 m 2 ) sediment trays containing defaunated pebble gravel were deployed at a study site (47 m water depth) in July 1997 and recovered in June 1999. The undersides of the tray lids positioned 56 cm above the trays served as settlement panels over the same time period. We observed rapid colonization of the gravel substrate (56 species) and the settlement panels (35 species), indicating that colonization of gravel in this region is not limited by the supply of colonists. The species composition of the taxa found in the trays was broadly similar to that we collected over a 10-year period (1994-2004) in dredge samples from gravel sediments at the same site. The increase in abundance of animals in the gravel colonization trays was rapid and reached a level in 2 years that took 4.5 years to achieve in the surrounding gravel sediments once fishing had stopped, based on data from dredge sampling at this site. The increase in biomass of animals found in the sediment trays paralleled the trend of biomass increase observed in dredge samples over the same period (1997-1999) but was lower in value. These data suggest that after rapid initial increase in abundance of organisms, succession proceeded by increasing individual body size. A comparison of settlement panel and tray faunas revealed that the mean biomass of structure-forming epifauna (sponges, bryozoans, anemones, hydroids, colonial tube worms) on the panels was 8 times that found on the trays. Structure-forming taxa constituted 29% of the mean biomass of the panel fauna but only 5.5% of the tray fauna. By contrast, the mean biomass of scavengers (crabs, echinoderms, nudibranchs, gastropods) in the trays was 32 times that on the panels. Colonization of the tray gravel was more rapid for free-living species (many of which are prey for fish) than for structure-forming epifauna, though colonists of the latter species were present. The reduced success of structure-forming species in colonizing the tray gravel possibly is related to factors such as intermittent burial of the gravel by migrating sand and low survival of new recruits due to the presence of high numbers of scavengers on the gravel. These two factors might explain, to varying degree, the slow recolonization of gravel habitats by structure-forming species in Closed Area II of the northern part of Georges Bank. ?? 2009 Elsevier Ltd.

Deep-Sea Research Part II: Topical Studies in Ocea↗

USGS2015

Water masses, ocean fronts, and the structure of Antarctic seabird communities: putting the eastern Bellingshausen Sea in perspective

Waters off the western Antarctic Peninsula (i.e., the eastern Bellingshausen Sea) are unusually complex owing to the convergence of several major fronts. Determining the relative influence of fronts on occurrence patterns of top-trophic species in that area, therefore, has been challenging. In one of the few ocean-wide seabird data syntheses, in this case for the Southern Ocean, we analyzed ample, previously collected cruise data, Antarctic-wide, to determine seabird species assemblages and quantitative relationships to fronts as a way to provide context to the long-term Palmer LTER and the winter Southern Ocean GLOBEC studies in the eastern Bellingshausen Sea. Fronts investigated during both winter (April–September) and summer (October–March) were the southern boundary of the Antarctic Circumpolar Current (ACC), which separates the High Antarctic from the Low Antarctic water mass, and within which are embedded the marginal ice zone and Antarctic Shelf Break Front; and the Antarctic Polar Front, which separates the Low Antarctic and the Subantarctic water masses. We used clustering to determine species' groupings with water masses, and generalized additive models to relate species' densities, biomass and diversity to distance to respective fronts. Antarctic-wide, in both periods, highest seabird densities and lowest species diversity were found in the High Antarctic water mass. In the eastern Bellingshausen, seabird density in the High Antarctic water mass was lower (as low as half that of winter) than found in other Antarctic regions. During winter, Antarctic-wide, two significant species groups were evident: one dominated by Adélie penguins ( Pygoscelis adeliae ) (High Antarctic water mass) and the other by petrels and prions (no differentiation among water masses); in eastern Bellingshausen waters during winter, the one significant species group was composed of species from both Antarctic-wide groups. In summer, Antarctic-wide, a High Antarctic group dominated by Adélie penguins, a Low Antarctic group dominated by petrels, and a Subantarctic group dominated by albatross were evident. In eastern Bellingshausen waters during summer, groups were inconsistent. With regard to frontal features, Antarctic-wide in winter, distance to the ice edge was an important explanatory factor for nine of 14 species, distance to the Antarctic Polar Front for six species and distance to the Shelf Break Front for six species; however, these Antarctic-wide models could not successfully predict spatial relationships of winter seabird density (individual species or total) and biomass in the eastern Bellingshausen. Antarctic-wide in summer, distance to land/Antarctic continent was important for 10 of 18 species, not a surprising result for these summer-time Antarctic breeders, as colonies are associated with ice-free areas of coastal land. Distance to the Shelf Break Front was important for 8 and distance to the southern boundary of the ACC was important for 7 species. These summer models were more successful in predicting eastern Bellingshausen species density and species diversity but failed to predict total seabird density or biomass. Antarctic seabirds appear to respond to fronts in a way similar to that observed along the well-studied upwelling front of the California Current. To understand fully the seabird patterns found in this synthesis, multi-disciplinary at-sea investigations, including a quantified prey field, are needed.

Deep-Sea Research Part II: Topical Studies in Ocea↗

USGS2010

Food-web structure of seep sediment macrobenthos from the Gulf of Mexico

The slope environment of the Gulf of Mexico (GOM) supports dense communities of seep megafaunal invertebrates that rely on endosymbiotic bacteria for nutrition. Seep sediments also contain smaller macrofaunal invertebrates whose nutritional pathways are not well understood. Using stable-isotope analysis, we investigate the utilization of chemosynthetically fixed and methane-derived organic matter by macrofauna. Biological sampling was conducted in three lower-slope GOM seep environs: Green Canyon (GC852, 1428 m), Atwater Valley (AT340, 2230 m), and Alaminos Canyon (AC601, 2384 m). Infaunal delta 13 C and delta 15 N exhibited a broad range of values; most infauna appeared to be heterotrophic, although several taxa had very light delta 15 N and delta 13 C values, indicating possible reliance on chemoautotrophic symbioses. The lightest delta 13 C and delta 15 N values were observed in nematodes (delta 13 C=-54.6 + or - 0.1 per mil, delta 15 N=-6.1 + or - 0.2 per mil) and one gastropod (delta 13 C=-54.1 per mil, delta 15 N=-1.1 per mil) from Green Canyon. Mixing-model results indicated that sulfur-oxidizing Beggiatoa may be an important food source for seep infauna; the rate of utilization ranged from 60% to 100% at Green Canyon and Atwater Valley. The overall range in isotope values was similar across the three sites, suggesting that biogeochemical processes may be very similar in these geographically distinct areas.

Deep-Sea Research Part II: Topical Studies in Ocea↗

USGS2011

Characterization of winter foraging locations of Adélie penguins along the Western Antarctic Peninsula, 2001–2002

In accord with the hypotheses driving the Southern Ocean Global Ocean Ecosystems Dynamics (SO GLOBEC) program, we tested the hypothesis that the winter foraging ecology of a major top predator in waters off the Western Antarctic Peninsula (WAP), the Adélie penguin ( Pygoscelis adeliae ), is constrained by oceanographic features related to the physiography of the region. This hypothesis grew from the supposition that breeding colonies in the WAP during summer are located adjacent to areas of complex bathymetry where circulation and upwelling processes appear to ensure predictable food resources. Therefore, we tested the additional hypothesis that these areas continue to contribute to the foraging strategy of this species throughout the non-breeding winter season. We used satellite telemetry data collected as part of the SO GLOBEC program during the austral winters of 2001 and 2002 to characterize individual penguin foraging locations in relation to bathymetry, sea ice variability within the pack ice, and wind velocity and divergence (as a proxy for potential areas with cracks and leads). We also explored differences between males and females in core foraging area overlap. Ocean depth was the most influential variable in the determination of foraging location, with most birds focusing their effort on shallow (<200 m) waters near land and on mixed-layer (200–500 m) waters near the edge of deep troughs. Within-ice variability and wind (as a proxy for potential areas with cracks and leads) were not found to be influential variables, which is likely because of the low resolution satellite imagery and model outputs that were available. Throughout the study period, all individuals maintained a core foraging area separated from other individuals with very little overlap. However, from a year with light sea ice to one with heavy ice cover (2001–2002), we observed an increase in the overlap of individual female foraging areas with those of other birds, likely due to restricted access to the water column, reduced prey abundance, or higher prey concentration. Male birds maintained separate core foraging areas with the same small amount of overlap, showing no difference in overlap between the years. While complex bathymetry was an important physical variable influencing the Adélie penguin's foraging, the analysis of sea ice data of a higher resolution than was available for this study may help elucidate the role of sea ice in affecting Adélie penguin winter foraging behavior within the pack ice.

Deep-Sea Research Part II: Topical Studies in Ocea↗

USGS2013

Cold-seep habitat mapping: high-resolution spatial characterization of the Blake Ridge Diapir seep field

Relationships among seep community biomass, diversity, and physiographic controls such as underlying geology are not well understood. Previous efforts to constrain these relationships at the Blake Ridge Diapir were limited to observations from piloted deep-submergence vehicles. In August 2012, the autonomous underwater vehicle (AUV) Sentry collected geophysical and photographic data over a 0.131 km2 area at the Blake Ridge Diapir seeps. A nested survey approach was used that began with a regional or reconnaissance-style survey using sub-bottom mapping systems to locate and identify seeps and underlying conduits. This survey was followed by AUV-mounted sidescan sonar and multibeam echosounder systems mapping on a mesoscale to characterize the seabed physiography. At the most detailed survey level, digital photographic imaging was used to resolve sub-meter characteristics of the biology. Four pockmarks (25–70 m diameter) were documented, each supporting chemosynthetic communities. Concentric zonation of mussels and clams suggests the influence of chemical gradients on megafaunal distribution. Data collection and analytical techniques used here yield high-resolution habitat maps that can serve as baselines to constrain temporal evolution of seafloor seeps, and to inform ecological niche modeling and resource management.

Deep-Sea Research Part II: Topical Studies in Ocea↗

USGS2013

Linkages between sea-ice coverage, pelagic-benthic coupling, and the distribution of spectacled eiders: observations in March 2008, 2009 and 2010, northern Bering Sea

Icebreaker-based sampling in the northern Bering Sea south of St. Lawrence Island in March of 2008, 2009, and 2010 has provided new data on overall ecosystem function early in the annual productive cycle. While water-column chlorophyll concentrations (<25 mg m −2 integrated over the whole water column) are two orders of magnitude lower than observed during the spring bloom in May, sea-ice algal inventories of chlorophyll are high (up to 1 g m −3 in the bottom 2-cm of sea-ice). Vertical fluxes of chlorophyll as measured in sediment traps were between 0.3 to 3.7 mg m −2 d −1 and were consistent with the recent deposition (days to weeks time scale) of chlorophyll to the surface sediments (0–25 mg m −2 present at 0–1 cm). Sediment oxygen respiration rates were lower than previous measurements that followed the spring bloom, but were highest in areas of known high benthic biomass. Early spring release of sedimentary ammonium occurs, particularly southeast of St. Lawrence Island, leading to bottom-water ammonium concentrations of >5 µM. These data, together with other physical, biological, and nutrient data are presented here in conjunction with observed sea-ice dynamics and the distribution of an apex predator, the Spectacled Eider (Somateria fischeri). Sea-ice dynamics in addition to benthic food availability, as determined by sedimentation processes, play a role in the distribution of spectacled eiders, which cannot always access the greatest biomass of their preferred bivalve prey. Overall, the data and observations indicate that the northern Bering Sea is biologically active in late winter, but with strong atmospheric and hydrographic controls. These controls pre-determine nutrient and chlorophyll distributions, water-column mixing, as well as pelagic-benthic coupling.

Deep-Sea Research Part II: Topical Studies in Ocea↗