Adult and juvenile (age-1) walleye pollock (Gadus chalcogrammus) were sampled by the US NOAA Alaska Fisheries Science Center summer bottom trawl survey in 2010, 2017, 2018, and 2019 in the northeastern and southeastern Bering Sea, with profiles of temperature collected concurrently. Similarly, the Russian Research Institute of Fisheries and Oceanography, Pacific branch, collected adult and juvenile

Die-offs of seabirds in Alaska have occurred with increased frequency since 2015. In 2018, on St. Lawrence Island, seabirds were reported washing up dead on beaches starting in late May, peaking in June, and continuing until early August. The cause of death was documented to be starvation, leading to the conclusion that a severe food shortage was to blame. We use physiology and colony-based observations

In May-June 2013, the RV G.O. Sars surveyed the Norwegian, Iceland, Irminger, and Labrador seas in the North Atlantic to explore distributions of plankton and pelagic/mesopelagic fish as part of the Euro-BASIN (Basin-scale Analysis, Synthesis, and INtegration) Project. From temperature and salinity measurements collected along the ship’s track, we present and compare the hydrography of the different

Indian Scientific Expeditions to the Southern Ocean (ISESO) have been implemented since 2004 to explore the unknown areas of the Indian Sector of the SO (ISSO) with the National Centre for Polar and Ocean Research (NCPOR) as the nodal centre for the Ministry of Earth Sciences, Government of India. The studies conducted in these expeditions have prime importance to understand the role of the SO on regional

Winter Water (WW) is a feature in the upper layers of the Southern Ocean during austral summer. The interaction of this cold water with surface and deeper subsurface layers can alter the heat budget as well as the carbon cycle. However, the structure and characteristics of the WW in the Southern Ocean is poorly understood due to the lack of in-situ data. In this study, hydrographic data collected from

During austral summer 2012, seawater samples were collected from the upper 120 m of the water column, across the frontal zones in the Indian Ocean sector of the Southern Ocean. Suspended particulate organic matter from seawater was characterised, from its organic carbon and nitrogen content, and δ13C(POM). There was a marked difference in δ13C(POM) across the three frontal zones. It was depleted from

The variations in nutrient utilization in the euphotic layer was studied using geochemical tracers N* (NO3- −16PO43−) and Si* (Si(OH)4 – NO3-) along two transect 57°30′E (T1) and 47°E (T2) during austral summer 2011 in the Indian Ocean sector of the Southern Ocean. Seawater samples collected from 8 depths within the euphotic zone (upper 200 m) along two meridional transects were analysed for nitrate

Sea-ice extent is very sensitive to climate change and its minor variations can significantly affect the regional biota of the Southern Ocean (SO). Chlorophyll-a concentration (Chl-a) is a primary proxy for the understanding of phytoplankton distribution and primary productivity in the oceans. Therefore, analysing the relation between Chl-a and sea-ice extent could be significant in understanding the

Phytoplankton, the primary producers in all aquatic systems, plays an important role in key biogeochemical processes that are linked to higher trophic levels and climate variability. The present study deals with the phytoplankton community structure in the Indian Ocean, particularly in the higher latitudes with respect to environmental variables to understand the region specific dominant community

The Southern Ocean is a very dynamic ecosystem comprising many fronts and interfrontal areas. Among the fronts, the Subtropical Front (STF) is a region of eddy activity exhibiting high spatial-temporal variability. The variability of food web structure in such a dynamic system and their influence on the plankton community structure is of great interest. The present study attempts to explain the variability

Recent historic lows in sea ice and cold pool extent in the Bering Sea have been linked to large-scale biogeographic shifts in many demersal taxa. Snow crab (Chionoecetes opilio) are associated with the cold pool and thus may be especially prone to northward range contraction with continued warming. Data from the 1988–2019 National Marine Fisheries Service eastern Bering Sea (EBS) bottom trawl surveys

Globally, the Indian Ocean appears to have the greatest blue whale (Balaenoptera musculus ssp) acoustic diversity, with at least four acoustic populations from three defined sub-species. To understand how these different populations use this region as habitat, we first need to characterize their spatial and seasonal distributions. Here, we build on previous passive acoustic monitoring studies and analyze

The epi- and mesopelagic ecosystems of four sub-polar ocean basins, the Labrador, Irminger, Iceland and Norwegian seas, were surveyed during two legs from Bergen, Norway, to Nuuk, Greenland, and back to Bergen. The survey was conducted from 1 May to 14 June, and major results were published in five papers (Drinkwater et al., Naustvoll et al., Strand et al., Melle et al., this issue, and Klevjer et

We describe a method to allow acoustic sampling at depths not reachable by the higher frequencies of ship hull-mounted echosounders and observe the abundance and behaviour of individual organisms in front of trawls. A self-contained scientific echosounder with a 120 kHz transducer was mounted forward-facing on the headline of a macrozooplankton trawl that was obliquely towed from 0 to 1000 m depth

Arctic marine ecosystems are experiencing substantial changes associated with sea ice loss and surface warming. The most obvious and dramatic changes include earlier ice retreat and a longer ice-free season, particularly on Arctic inflow shelves, including the Barents Sea in the Atlantic Arctic and the northern Bering Sea and Chukchi Sea in the Pacific Arctic. The extreme variability observed in recent

The Chukchi Sea consists of a broad, shallow (<45 m) shelf that is seasonally (November–July) covered by sea ice. This study characterizes the seasonal patterns of near-bottom primary production using moored instruments measuring chlorophyll fluorescence, oxygen, nitrate, and photosynthetically active radiation. From 2010 to 2018, moorings were deployed at multiple sites each year. Instruments were

Life-history and life-cycle models of Pink salmon (Oncorhynchus gorbuscha) are developed to provide insight into production dynamics of northern Bering Sea Pink salmon. Arctic ecosystems, including freshwater and marine ecosystems in the northern Bering Sea, are warming at a rapid rate. Due to their short, two-year life cycle, Pink salmon are well known to respond rapidly to ecosystem change and can

It is well known that the Physical properties of the ocean impact marine biological activity. Conversely, ocean biology feedsback to affect physical properties through the influence of phytoplankton on the ocean’s absorption of incoming shortwave radiation. In this study, we explore this feedback in the tropical Indian Ocean (TIO) throughout the seasonal cycle by comparing solutions to a biophysical

We observed herring horizontal and vertical distribution during feeding migration along a 128 km transect across the Arctic front of the Norwegian and Iceland seas, in early June, in relation to its physical, chemical and biological environment, distribution of prey organisms and pelagic and mesopelagic competitors. The Norwegian Spring Spawning herring is one of the largest and economically most important

Compared with other ocean basins, little is known scientifically about the seamounts in the Indian Ocean. Nonetheless, fishers have plundered these fragile ecosystems for decades, and now mining is becoming a reality. We introduce a multidisciplinary project referred to as MADRidge that recently focused on three shallow seamounts in the South West Indian Ocean between 19°S and 34°S. The larger Walters

Spatial anomalies associated with seamounts and islands have been detected in the South West Indian Ocean using a new surface chlorophyll-a based enrichment index (EI). Calculated from daily L3 4-km MODIS chl-a data from 2003 to 2018, the EI was used to quantify recurrent (seasonal) surface enrichment associated with these features. Most notable were the shallow Walters Shoal (18 m) and nearby deeper

This work is part of the MADRidge Project special issue which aims to describe pelagic ecosystems in the vicinity of three prominent shallow seamounts in the South West Indian Ocean: one here named MAD-Ridge (240 m below the surface) plus Walters Shoal (18 m) on the Madagascar Ridge, and La Pérouse (60 m) on the abyssal plain east of Madagascar. The three span latitudes 20°S and 33°S, some 1500 km

Based on satellite and in situ data, the dynamic characteristics and vertical structure of a surface intensified mesoscale eddy dipole recently expelled from the South East Madagascar Current (SEMC) is described for the first time. The dipole was surveyed 250 nautical miles south of Madagascar between 14 and 23 November 2016, during west-east and south-north transects carried out over the northern

The composition and spatial variability of ichthyoplankton assemblages were investigated at three shallow seamounts between latitudes 19°S and 33°S in the South West Indian Ocean (SWIO) – La Pérouse (60 m), an unnamed pinnacle south of Madagascar, referred to hereafter as MAD-Ridge (240 m), and the Walters Shoal seamount (18 m). In all, 299 larvae (23 families, 54 species) were present at La Pérouse

The La Pérouse seamount (60 m depth) has so far been poorly studied despite it being a short distance (160 km) from Réunion Island. As part of the MADRidge project, a multidisciplinary cruise was conducted to evaluate the effect of this shallow seamount on the local hydrology and ecology. Current measurements, temperature and chlorophyll-a profiles, and mesozooplankton and micronekton samples were

An investigation of the vertical and horizontal distributions of micronekton, as influenced by mesoscale eddies, the Madagascar shelf and shallow seamounts, was undertaken using acoustic data collected during two research cruises at an unnamed pinnacle (summit depth ~240 m) thereafter named “MAD-Ridge”, and at La Pérouse seamount (~60 m) in the south-western Indian Ocean. MAD-Ridge is located to the

The stable carbon (δ13C) and nitrogen (δ15N) isotope values of soft tissues of micronekton (crustaceans, squid, mesopelagic fish) and zooplankton were measured from organisms collected on the RV Antea at two seamounts located in the south-western Indian Ocean: La Pérouse (summit depth ~60 m) and “MAD-Ridge” (thus named in this study; summit depth ~240 m). Surface particulate organic matter (POM-Surf)

Mesopelagic fishes of the southeastern Indian Ocean are represented by a high number of lanternfish species (Myctophidae). The horizontal distribution patterns of their larvae have been previously studied; however, research on larval feeding habits is non-existent. The goal of this study was to describe the diet and trophic-based strategies of the most abundant myctophid larvae off Western Australia

A comparative study of the mesozooplankton in four North Atlantic basins is presented. During a trans-Atlantic expedition with R/V G.O. Sars in May and June 2013, the Norwegian Sea, Iceland Sea, Irminger Sea and Labrador Sea was surveyed twice on a round trip from Bergen, Norway to Nuuk, Greenland. Mesozooplankton samples of biomass, species composition and vertical distribution were obtained with

A precautionary approach to protecting biodiversity on mid-ocean ridges, while permitting seabed mining, is to design and implement a network of areas protected from the effects of mining. Such a network should capture representative populations of vent endemic fauna within regions of connectivity and across persistent barriers, but determining where such connectivity and barriers exist is challenging

Oceanic top predators, the marine ecosystems that support them and dependent socio-economic systems have been the subject of studies by researchers under the Climate Impacts on Oceanic Top Predators (CLIOTOP) regional programme since 2005. Research conducted under the programme has focused on how climate change is affecting the pelagic ocean, with a range of impacts detected or predicted for open ocean

The yellowfin tuna (Thunnus albacares; YFT) is a crucial species because it is the second most fished tuna globally. In this study, we analyzed the standardized catch per unit effort (CPUE) to determine the influence of climate indices on YFT distribution and fishing vessel dynamics. The standardized CPUE in the western Pacific Ocean was significantly correlated to the Pacific Decadal Oscillation (PDO)

Black marlin (Istiompax indica) are large, highly mobile, apex pelagic predators of tropical and subtropical oceans with high economic importance in western North Pacific fisheries. To assess the ontogenetic trophic ecology of black marlin in the western North Pacific Ocean, the stable isotopic composition of 177 black marlin muscle samples (87–383 cm, eye-orbit fork length (EFL); 33–447 kg, body weight)

We examined the abundance and horizontal and vertical distributions of epipelagic ctenophores and scyphomedusae in the northern Bering Sea using an underwater video camera during July of 2017 and 2018. The effects of environmental and biological parameters on the distribution of these species were evaluated by generalized additive modelling (GAM). In 2017, the dominant ctenophore, Bolinopsis infundibulum

We investigated spatial and interannual variation in the physical environment in the northern Bering Sea focusing on stratification, which is one factor affecting biological production in Arctic/subarctic regions. In particular, we analyzed in situ data obtained onboard the training ship Oshoro Maru in early summer in 2017 and 2018. We found that stratification in the areas just north of St. Lawrence

To better understand the impact of climate change on the Southern Ocean (SO) biogeochemistry, we must know the evolution of the seasonal cycle of biological properties. Here we present the first estimate of the seasonal evolution of chlorophyll-a (Chl-a) along oceanic fronts in the Indian sector of SO using Bio-Argo float observations. The present study is based on data collected using three such floats

Phytoplankton biomass (chlorophyll-a) and community structure in the water column was analyzed across various frontal regions in the Subtropical Front (STF), Sub-Antarctic Front (SAF), Polar Front-1 (PF1) and Polar Front-2 (PF2) in the Indian Ocean sector of the Southern Ocean (SO) during the austral summer (January–February) of 2013 and 2015. The surface chlorophyll-a (Chl-a) was maximum in PF1 (0

Observations from a single mooring site on the northern Chukchi Sea continental slope near the 1000-m isobath are presented. This site was occupied consecutively for three years (spanning September 2014–August 2017). Vertically the flow divides into three depth ranges: the upper ~200 m, ~200–~850 m and near-bottom flow. In the upper ~200 m, the mean flow was northwestward and strongest in the summer

Rapid changes in sea ice and ocean properties are occurring in the Chukchi Sea, and there is considerable uncertainty how these changes might influence nutrient distributions and ultimately primary productivity. Although inorganic nitrogen is a limiting nutrient, there are few reports on seasonal or interannual variability of nitrate, especially those focused on wintertime replenishment of nitrate

Kuwait's marine area, located at the far north-western corner of the Arabian/Persian Gulf, is under significant and diverse anthropogenic effects, which are exacerbated by climatic changes. Microalgal blooms occur in Kuwait's waters year round and are caused by proliferation of microalgae, cyanobacteria, and photosynthetic ciliates. The diverse assemblage of potentially toxic diatoms and dinoflagellates

The Chukchi Sea has recently experienced increased water temperatures, increased advection of water from the Bering Sea, declines in sea-ice concentration, and shorter periods of ice coverage. These physical changes are expected to impact trophic food-webs and ecosystem attributes. In this study, a series of research surveys were conducted in the summers of 2011–2015 to characterize the physical environment

We studied vertical distribution and diel vertical migration (DVM) behaviour of mesopelagic acoustic scattering layers in relation to environmental conditions in the Norwegian Sea, the Iceland Sea, the Irminger Sea, and the Labrador Sea. Distinct mesopelagic scattering layers were found in all basins, but the daytime depth of the layers varied between basins. The results suggested that daytime vertical

The northern Bering Sea and Chukchi Sea represent the gateway from the Pacific to the Arctic. This contiguous marine system encompasses one of the largest continental shelves in the world and serves as the sole point of connection between the North Pacific and Arctic Ocean. This region has unique attributes and complex dynamics, driven by the convergence of distinct water masses, dynamic currents,

A temperature and salinity hydrographic profile climatology is assembled, evaluated for data quality, and analyzed to assess changes of the Bering and Chukchi Sea continental shelves over seasonal to century-long time scales. The climatology informs description of the spatial distribution and temporal evolution of water masses over the two shelves, and quantification of changes in the magnitude and

Aerosol optical depth (AOD), black carbon (BC) mass concentration, aerosol size, along with wind parameters, were derived during Southern Ocean expeditions (SOE) 7 and 8 carried out in austral summer of 2013 and 2015, with an aim to analyse the effect of aerosol on incoming solar radiation. The data were complemented with trace metals from aerosol samples of SOE-6 conducted in 2012. The AOD spectra

The Southern Ocean ecosystem is thought to be experiencing a long-term increase in Salpa thompsoni. Uncertainty surrounds the environmental drivers behind variable S. thompsoni abundances, particularly within the East Antarctic region. In this study, S. thompsoni populations were sampled in the Indian Sector of the Southern Ocean, as part of the January–February 2016 Kerguelen Axis voyage. These recent

The influence of environmental factors on the horizontal community structure of zooplankton over the southern Kerguelen Plateau was investigated during summer in 2016. Zooplankton abundance ranged from 1490 to 363,484 ind. 1000 m-3, with highest numbers observed in the eastern and central areas. Based on cluster analysis the zooplankton were divided into six groups (A−F), and these were only distinguished

Fin whales (Balaenoptera physalus) are common summer visitors to the Pacific Arctic, migrating through the Bering Strait and into the southern Chukchi Sea to feed on seasonally-abundant prey. The abundance and distribution of fin whales in the Chukchi Sea varies from year-to-year, possibly reflecting fluctuating environmental conditions. We hypothesized that fin whale calls were most likely to be detected

To better understand habitats of larval Pacific bluefin tuna (PBT; Thunnus orientalis) in the nursery grounds, the vertical distribution of larval PBT was collected using a 1-m2 Tucker trawl and a 3.14-m2 ring net at depths of 0, 10, 20, and 30 m during the spawning seasons of 2016 and 2017. Most of the larvae in the Japan Sea (756 of 938 individuals) were collected from the surface layer using a ring

We investigated the pelagic habitat requirements of Arctic larval fish and the effects of interannual variability of ocean conditions on their distribution. We examined the distribution of larval Arctic cod, Bering flounder, yellowfin sole and capelin in the Chukchi and northern Bering seas during two years with different oceanographic conditions. We found that despite marked changes in water mass

We describe the distribution, abundance and growth of the paralarvae and juveniles of the glass squid Galiteuthis glacialis which were collected from tows conducted at 500 m depth in Prydz Bay, Antarctica by using an Isaacs Kidd Midwater Trawl (IKMT). Paralarvae occurred in an area from 57° S to 65°30ʹ S and 57°–66° E. Early juveniles co-occurred with paralarvae at 57°–65°30′ S and 57°37′ E to 64°56′

Annual phytoplankton blooms on the northern region of the Kerguelen Plateau fuel a productive food web that supports highly valuable commercial fisheries for Patagonian toothfish (Dissostichus eleginoides) and mackerel icefish (Champsocephalus gunnari). The food web on the plateau is understudied in comparison to other regions of the Southern Ocean. Major linkages and energy pathways have not been

The biological carbon pump has been estimated to export ~5–15 Gt C yr−1 into the deep ocean, and forms the principal deep-sea food resource. Irregular, intense pulses of particulate organic carbon (POC) have been found to make up about one-third of the overall POC fluxes at a long-term deep-sea research station influenced by coastal upwelling of the California Current, Station M (34°50′N, 123° W, 4000 m

We evaluate a recent region-specific model of export production (Kelly et al., 2018) and some similar fits to in situ data for the California Current Ecosystem using satellite data. The model is a simple linear function of net primary productivity (NPP): Export = 0.08 × NPP + 72 where EF is export flux in mg C m−2 d−1. We confirm that contrary to several global algorithms export efficiency (e-ratio = export/primary

This study examines the applicability of the two-component mixing model in one dimension (depth) to published depth profiles of DOC concentrations and Δ14C values from hydrographic Station M (34°50′N, 123°00′W). We have rederived the two-component model assuming DOC exhibits stable conservative tracer properties and compared it to a model that includes reactivity and radioactive decay. We used 14C∗

High-temporal-resolution views of particle flux to the abyssal benthic boundary layer are provided for an eight-month period (October 2014–June 2015) at the long-term monitoring site Station M within the California Current ecosystem. Contributions of fecal pellets and aggregates to particulate organic carbon (POC) flux at 3900 m depth were estimated based on optical sediment trap (Sedimentation Event

The sequestration of carbon in the deep ocean relies on the export of sinking particulate organic matter (POM) originating in the surface waters and its attenuation by organisms that reprocess and repackage it. Despite decades of research, predicting the variability of POM to the deep ocean remains difficult as there is still a gap in the knowledge as to which and how organisms control or influence

Deep-sea currents in the Northeast Pacific Ocean are examined using observations at Station M, located on the abyssal plain 220 km offshore of central California. Collected near the seabed at ~4000 m depth from October 2014–October 2018, the current meter observations supplement long-term investigations of deep-sea benthic ecology at this site. To investigate mechanisms for variability at different

Gelatinous zooplankton are prominent fauna in the deep ocean, especially in the water column associated with the sea floor. This interface zone, the benthic boundary layer, is critical to biogeochemical exchanges between pelagic and benthic communities. A conspicuous member of this benthic boundary layer community in the abyssal Northeast Pacific (Sta. M; 4000 m depth) is the hydrozoan medusa, Benthocodon