Shelf Depths Research Articles

Theoretical framework for the response of barotropic shelf current to along-shelf bathymetric perturbations

Abstract The mechanism underlying the response of barotropic shelf current to along-shelf bathymetric perturbations is rationalized by a one-dimensional vorticity equation. Fourier analysis of the equation in the wavenumber domain suggests that bathymetric features with relatively short length scales in the alongshore direction drive steady cross-shelf velocity undulations when the shelf circulation is against the direction of Kelvin wave propagation (upwelling regime). In contrast, much weaker and non-oscillatory cross-shelf velocity is expected when the shelf circulation is in alignment with propagating Kelvin waves (downwelling regime). The velocity undulations in the upwelling regime result from a positive feedback mechanism associated with potential vorticity (PV) advection; however, the presence of bottom friction restricts such undulations within a few wavelengths. The characteristic wavelength of undulations is determined by when the normalized drag coefficient , where u is the along-shelf mean flow speed, Hs is shelf depth, αs is the bottom slope, f is the Coriolis parameter, and r is the linear drag coefficient. Using this formula, a scale of the cross-shelf displacement distance Yt is proposed, aligning with one-layer barotropic simulations over a large parameter space. The study provides a framework for investigating barotropic cross-shelf exchange caused by shelf circulation over irregular bottom bathymetries.

ON THE POSSIBLE FORMATION MECHANISM OF THE OPEN FRACTURING IN SEDIMENTARY BASINS

The paper shows that the formation of orthogonal systems of open macrofractures (cleavages) of sedimentary basins can occur at the stage of diagenesis during the first hundreds of years for a small range of shelf depths (up to 100 m) during sedimentation. During this period, sediments are compacted and the excess water is slowly squeezed out, which determines the decrease in the Poisson’s ratio from values close to 0.5 to values 0.3–0.2. Because of this, in sediments, the stress state of which is almost completely determined only by the gravity of the overlying rocks, is reduced by 50 % or more of the horizontal compression stress level from the initial lithostatic pressure level. On the other hand, if the limit of pseudoplastic flow is reached in the rock, vertical compaction occurs, accompanied by an increase in horizontal compression. These two competing processes together with the factor of fluid pressure in fractures and pores determine the possibility of brittle fracture formation. It is shown that for rocks with a low level of yield strength (clay), compaction leads to an increase in the level of horizontal compression stresses, which makes brittle fracture in such rocks at the stage of diagenesis impossible. In rocks with a high level of strength (sandstone, limestone), brittle fracture due to excess water pressure in the sub­vertical microcracks starts earlier than the shear yield limit is reached.

Effect of wind–wave conditions on the distribution of the phytoplankton community in the coastal area of the southern Crimea in spring (Black Sea)

Based on the measurement data obtained during the 121th cruise of the RV Professor Vodyanitsky, regularities were established between spatial distribution of quantitative characteristics and phytoplankton species composition, chlorophyll a concentration, and hydrometeorological parameters of the environment on the southern Crimean coast in the spring 2022. Chlorophyll a concentration was compared with satellite observation data of high spatial resolution. In selected areas with different shelf depths, the features of the distribution of phytoplankton indicators under conditions of changing hydrometeorological parameters were studied. The mechanisms of vertical water exchange were described. In coastal waters of the Crimea (Foros–Novy Svet), with intense western wind contributing to Ekman upwelling and low water temperature is a consequence of the upwelling, rather high values of phytoplankton biomass and abundance and chlorophyll a concentration were recorded, which were accompanied by the highest values of oxygen content. In the area of Sudak–Feodosiya, with intense northeastern wind and waves and with quite high water temperature, low dissolved oxygen, low values of phytoplankton biomass and abundance and chlorophyll a concentration were registered. Apparently, in Sevastopol area, Ekman upwelling arises under the effect of northern and northwestern winds. In three regions, dinoflagellate microalgae prevailed in spring 2022 in phytoplankton biomass. Those accounted for 52, 66, 81 % of the total number of species identified in the regions: Foros–Novy Svet, Sudak–Feodosiya, near Sevastopol, respectively. Thus, the main mechanisms were analyzed, which drive spatial distribution of quantitative characteristics and species composition of the phytoplankton community in the Crimean coastal water area with different shelf depths in spring.

Features of Seismological Observations in the Arctic Seas

This paper is devoted to the features of seismological observations in the Arctic seas, which are complicated by harsh climatic conditions, the presence of ice cover, stamukhi and icebergs, and limited navigation. Despite the high risk of losing expensive equipment, the deployment of local networks of bottom seismographs or stations installed on ice is still necessary for studying the seismotectonic characteristics and geodynamic processes of the region under consideration, the deep structure of the crust and upper mantle, seismic hazards, and other marine geohazards. Various types of seismic stations used for long-term and short-term deployments in the Russian sector of the Arctic Ocean, as well as various schemes and workflows for their deployment/recovery, are described. The characteristics of seafloor seismic noise and their features are also considered. The results of deployments demonstrate that the characteristics of the stations make it possible to reliably record earthquake signals and seismic noise. Based on the experience gained, it was concluded that the preferred schemes for deploying ocean-bottom seismographs are those in which their subsequent recovery does not depend on their power resources. Usually, such schemes allow for the possibility of dismantling stations via trawling and are suitable for the shelf depths of the sea. The advantages of such schemes include the possibility of installing additional hydrophysical and hydrobiological equipment. When using pop-up ocean-bottom seismographs, special attention should be paid to the careful planning of the recovery because its success depends on the possibility of a passage to the deployment site, which is not always possible due to changing meteorological and ice conditions. Seismic records obtained on the seafloor are characterized by a high noise level, especially during periods of time when there is no ice cover. Therefore, it is recommended to install bottom stations for periods of time when ice cover is present. The frequency range of the prevailing noise significantly overlaps with the frequency range of earthquake signals that must be taken into account when processing bottom seismic records.

Broadband Acoustic Field in a Shallow-Water Waveguide with an Inhomogeneous Bottom

A broadband (35–1000 Hz) sound field formed by a point source in a shelf zone with inhomogeneous bottom sediment structure is studied using numerical modeling. The shelf depth is about 30 m and the maximum distance is 10 km. The transitional zone from the bottom with a sound speed of 1400 m/s to the bottom with a speed of 1600 m/s is chosen as the model inhomogeneity. The normal mode theory and wide-angle parabolic equations are used for sound field calculations. Numerical experiments show that the manifestation of horizontal refraction is noticeable at low frequencies (below 100 Hz). It leads to an increase in the amplitude of the low-frequency sound pulse propagating along the transitional zone by more than 10 dB in comparison with a similar waveguide with a homogeneous bottom. At frequencies above 100 Hz, the dominant effect is the mode coupling, causing the appearance of quasi-periodic oscillations of modal amplitude in the frequency domain. The conclusions from the simplified model are confirmed by calculations for the real structure of bottom sediments in the Kara Sea.

Unusual Enhancement of the Optical Depth on the Continental Shelf Depth Latitudinal Variation in the Stratospheric Polar Vortex

The Antarctic ozone hole has attracted attention concerning global climate change. Breakthroughs regarding ozone observation methods and the formation principles of ozone holes have occurred. This study compared the slant column ozone obtained from SCanning Imaging Absorption SpectroMeter for Atmospheric CHartographY (SCIAMACHY) Level 1 optical spectroscopy data processed by QDOAS software with that reconstructed from SCIAMACHY Level 2 ozone data using geographic information to obtain the optical depth coefficients. The global distribution of optical depth coefficients reveals latitudinal homogeneity, whereas the distribution of coefficients in the polar regions reveals heterogeneity. This heterogeneity has an annual variation pattern, alternating between strong and weak distributions in the Arctic and Antarctic regions. It is most evident in the Palmer Peninsula of Antarctica, where the optical depth coefficients were significantly higher than those of the surrounding regions at the same latitude. This analysis excluded the atmospheric pressure influence and suggested the influence of the continental shelf depth. The protrusion of the continental shelf depth changes the optical depth coefficients owing to the geographical proximity of the Antarctic Palmer Peninsula to South America, which separates the Atlantic and Pacific Oceans in an east–west direction.

Mesopelagic fishes are important prey for a diversity of predators

Through daily vertical movements, mesopelagic fishes contribute to global carbon export and, when eaten, link primary consumers to higher trophic level predators. Although the importance of mesopelagic fishes as prey to individual predator species has been explored, a comprehensive assessment of mesopelagic fishes as prey at the scale of a large marine ecosystem would advance our observing, modeling, and predicting of biodiversity and ecosystem function. We use diet samples from over 105,000 individual predators from 143 taxa in the California Current Ecosystem (CCE) to quantify and evaluate the role of mesopelagic fishes as prey. For 11 predator taxa, including protected mammal species, pelagic squids, a shelf-edge-associated rockfish and highly migratory species, mesopelagic fishes occurred in greater than 25% of all diet samples, likely comprising an important source of prey. Of the 143 taxa represented, individuals from 36 taxa, or 25% percent of all predator taxa in the database, consumed at least one mesopelagic fish species, including economically important fishery species such as Bluefin tuna (16% of all non-empty diet samples), Albacore (19%), Swordfish (50%), Humboldt squid (52%), and Pacific hake (4%). Compared with coastal pelagic fish species (essential prey in the CCE), mesopelagic fish were more frequently encountered in the diets of 21 predator taxa. Lanternfish (family Myctophidae) were the most common prey and consumed by the greatest diversity of predators (32 taxa), but an additional 16 families of mesopelagic fishes were also consumed by predators, highlighting the diversity of organisms inhabiting mesopelagic depths. Mesopelagic fishes were found in the diets of predators collected from shelf depths to well offshore, accentuating the role of mesopelagic fishes as prey across habitats, especially for predators foraging over the slope and further offshore. Our work illuminates the importance of mesopelagic fishes as prey to a diversity of economically valuable and protected species, underscoring the need to incorporate mesopelagic fishes more comprehensively into food web models, global carbon budgets and ultimately our understanding of ecosystem function.

Experimental demonstration of spatial division multiplexing multiple-input/multiple-output underwater acoustic communication using a time-reversal method at the depth of the continental shelf: a consideration of optimization of signal length and number of transmission channels

In this paper, the performance of the adaptive passive time-reversal method is investigated for an at-sea experiment of multiple-input/multiple-output underwater acoustic communication over a range of 13.5 km. The experiment was conducted at a depth of 200 m utilizing up to five transmitters with 4–8.5 kHz signal bandwidth for spatial division multiplexing. It was confirmed that the performance depends on the delay time from the timing of the channel response estimation to the communication signal reception, and the optimal signal length and the number of transmission channels can be determined according to the required bit error rate (BER) for the system. As a result, using the optimal signal length and a number of transmission channels, effective data rates of 30.21 and 37.53 kbps are achieved with BER ranges of less than 0.1% and 1%, respectively, with more than 90% of received communication signal packets.

New species and records of Heterospio (Annelida, Longosomatidae) from continental shelf, slope and abyssal depths of the Atlantic Ocean, Pacific Ocean, Indian Ocean and adjacent seas.

Nineteen species of the rare polychaete genus Heterospio are reported, 15 of which are new to science. The status of H. longissima Ehlers, 1874, the type-species, is reviewed. The specimens examined are from several locations in the North Atlantic Ocean, Gulf of Mexico, Caribbean Sea, off Br azil, the Indian Ocean, the Pacific Ocean off California, New Zealand, Australia, and the South China Sea. Deep-water samples from the western North Atlantic Ocean collected by the late Drs. H.L. Sanders and R.R. Hessler that were reported by Hartman as H. longissima were re-examined and referred to two new species, H. hartmanae n. sp. (abyssal depths, New England to Bermuda transect) and H. guiana n. sp. (bathyal depths off Suriname). Other materials from the Sanders/Hessler North Atlantic collections were also examined and referred to two additional species, H. canariensis n. sp. (deep water off Canary Islands) and H. southwardorum n. sp. (Bay of Biscay) as well as H. cf. reducta from off SW Ireland in bathyal depths. New collections from the North Atlantic region include additional materials of H. hartmanae n. sp. (deep water off the Mid-Atlantic and SE USA), H. aruba n. sp. (Caribbean Sea), H. bathyala n. sp. (deep water off SE USA), and H. dibranchiata n. sp. (deep water, Gulf of Mexico). Heterospio paulolanai n. sp. is from shelf depths off southeastern Brazil. Heterospio knoxi n. sp. is from the North Island of New Zealand, H. ehlersi n. sp. is from the Gulf of Thailand, in the South China Sea, H. bidentata n. sp. is described from deep water in the Coral Sea off eastern Australia, and H. alata n. sp. and H. brunei n. sp. are described from deep water off the Island of Borneo in the South China Sea. Heterospio africana n. sp. and H. antonbruunae n. sp. are described from off east Africa in the Mozambique Channel. New records and descriptions of H. catalinensis, H. indica, and H. peruana are presented. The 15 new species reported here nearly triple the number of previously known species of Heterospio, with 23 species now recognized. All known species are tabulated and compared.

Mapping Past Distributions of Marine Mollusks Using Shell Death Assemblages

Marine species assessments rely heavily on baseline surveys conducted after the 1960s, long after many anthropogenic pressures began, which could lead to misinformed management decisions and poor conservation outcomes. In this study, we collaborated with Florida Fish and Wildlife to conduct stock assessments for mollusks of the west Florida shelf that incorporate shell death assemblages. One of our first assessments was of the Florida Fighting Conch, Strombus alatus, an abundant gastropod that is also under consideration as a replacement fishery for the threatened Queen Conch. Live and dead shells were collected from >300 dredge tows between 2008-2018 covering the entire west Florida shelf. Shells were age-partitioned by 14C- and AAR-calibrated taphonomic criteria. Counts were converted to densities per m2. Inverse distance weighting interpolation of S. alatus death assemblages reveals multiple population centers along the coast and a rapid decrease in density with depth from 25-120 m. In contrast, live conchs were absent in our dredge samples from shelf depths deeper than 40 m. These differences are confirmed by single-visit occupancy methods that account for variation in detectability across the samples. Live-dead differences in spatial distribution are probably influenced by time averaging in death assemblages, which increases detectability of conchs in deeper habitats, where they may be too rare to be sampled alive. However, extirpation of offshore populations was also indicated by independent natural history collection occurrence records, which show numerous live-collected conchs from 1940-1980 but none afterwards, despite an increase in sampling effort. These results suggest that live-dead comparisons can reveal biodiversity loss at the scale of large marine ecosystems.

Study on Characteristics and Optimal Layout of Components in Shallow Water Mooring System of Floating Wind Turbine

Offshore wind energy resources far exceed those on land. However, the increase in water depth of the continental shelf in China’s sea area slows down as the distance from the shore increases. In view of the characteristics of China’s sea, how to optimize the design of mooring systems to adapt to the water depth conditions in China’s waters and to resist the harsh sea conditions is one of the major problems encountered in the development of floating wind turbines. In this paper, the 5MW-OC4 semi-submersible floating wind turbine is taken as the research object, and the frequency domain and time domain calculation of the floating wind turbine are carried out by using SESAM software under the water depth of 40 m in the Bohai Sea. By comparing the motion response and tension of catenary and tension mooring floating wind turbine. The mooring system is optimized by combining the buoy and clump weight. The results show that the catenary mooring mode is more suitable for the floating wind turbine under shallow water conditions. Mooring accessories used in combination have the same effect on the overall response of the floating wind turbine as changing the same mooring parameters when used alone, but the effect of changing the mooring parameters on the performance optimization of the mooring system is more obvious when used in combination, and a reasonable combination of accessories can significantly change the overall characteristics of the floating system and affect the safety and cost of the system.

COASTAL OCEAN ACIDIFICATION IN BRAZIL: A BRIEF OVERVIEW AND PERSPECTIVES

This perspective paper aims at presenting the current knowledge on the processes of ocean acidification (OA) and coastal acidification (CA) in the Brazilian coastal ocean. We define and differentiate the processes of OA and CA: the first driven by the actual global increase of atmospheric carbon dioxide (CO2); the second driven by a combination of ocean uptake of atmospheric CO2 and other local/regional chemical additions or subtractions in aquatic ecosystems at the land-ocean interface. Regarding OA, we have centered our analysis on the data available for the main water masses along the Brazilian coast: South Atlantic Central Water (SACW), Tropical Water (TW), and Coastal Water (CW). The few data available for the shallow coastal waters (< 200 m depth) of the continental shelf reveal an increase in the anthropogenic component of the total dissolved inorganic carbon (DIC) pool in the SACW, with a decline in the ocean pH (over two decades; 1993-2013), and in the saturation state of calcium carbonate (CaCO3) minerals. We could not find OA trends for TW and CW because no data was available. Overall, the colder water masses (SACW, Plata Plume) have lower buffering capacity and simulations show that will potentially experience earlier negative OA impacts than the warmer waters masses (TW, Amazon Plume). Regarding CA, we have identified some local/regional studies investigating the carbonate chemistry in nearshore/estuarine ecosystems, particularly on the quantification of sources and sinks of CO2 , and determining short-term variabilities. Apparently, spreading coastal eutrophication in Brazil can enhances or reduces the process of OA, depending on the net ecosystem metabolism in combination with other chemical alterations. However, we could not find medium-long term acidification trends due to the limited data. There is a limited capacity to produce long time-series of carbonate chemistry parameters in key ecosystems and regions along the Brazilian coast. This lack of past information hinders and impairs the scientific community for identifying potential patterns of acidification along the Brazilian coast. We call for an urgent action in Brazil, with emphasis on the establishment of moored buoys/stations and/or scientific programs in the long term with continuous, real-time measurements of the main carbonate chemistry parameters.
 Keywords: ocean acidification, coastal acidification, coastal eutrophication, continental shelf, Southwestern Atlantic Ocean

Calcareous Nannofossil Biostratigraphy and Ostracoda Paleoecology of Hartha Formation from Balad (1) well, Central Iraq

Seventeen samples of Hartha Formation in Balad (1) well, central Iraq, are studied on the basis of stratigraphic ranges of the recorded calcareous nannofossils for twenty species belonging to twelve genera. The studied section reveals three biozones arranged from oldest to youngest as follows; (1) Calculites ovalis Interval Biozone (CC19), (2) Ceratolithoides aculeus Interval Biozone (CC20), (3) Quadrum sissinghii Interval Biozone (CC21). These Biozones are correlated with other calcareous nannofossils biozones from both local and regional sections, leading to conclude the age of the Middle Campanian.
 Rerecorded eighteen ostracode species that belong to eleven genera are identified, all of which were previously recorded from Iraq and adjacent regions. The occurrence of these species leads to conclude a continental shelf environment, while they are typical of inner shelf-outer shelf depth.

Coastal trapped waves propagation along the Southwestern Atlantic Continental Shelf

This study investigates the propagation of coastal trapped waves (CTWs) along the Brazilian continental shelf between 34°S and 11°S using in situ data combined with the outputs from a high-resolution ocean simulation with HYCOM. The CTWs generation area covers a wide region ranging from the Patagonian shelf to the southern Brazilian shelf. The spectral analysis of coastal sea level series between 54°S and 10.5°S shows three bands of high energy associated with periods from 5 to 12 days, 15–22 days, and 25–40 days. The energy of the CTWs decreases along their propagation for all frequency bands, showing a drastic reduction north of 22°S, due to abrupt variations in the width and depth of the continental shelf between Tubarão Bight and Abrolhos Bank. Their phase speed propagation varies along the coast, being faster (>25 m/s) in the southernmost region (between 42°S and 41°S), reaching ~11 m/s north of 41°S, and reducing to ~3 m/s further north (equatorward of 24°S). The free Continental Shelf Wave theory supports the notion that the intense deceleration north of 24°S can be explained by the narrowing of the continental shelf. The stratification parameter indicates that the Brazilian continental shelf has a barotropic response to wind-generated disturbances.

Coupling framework (1.0) for the PISM (1.1.4) ice sheet model and the MOM5 (5.1.0) ocean model via the PICO ice shelf cavity model in an Antarctic domain

Abstract. The past and future evolution of the Antarctic Ice Sheet is largely controlled by interactions between the ocean and floating ice shelves. To investigate these interactions, coupled ocean and ice sheet model configurations are required. Previous modelling studies have mostly relied on high-resolution configurations, limiting these studies to individual glaciers or regions over short timescales of decades to a few centuries. We present a framework to couple the dynamic ice sheet model PISM (Parallel Ice Sheet Model) with the global ocean general circulation model MOM5 (Modular Ocean Model) via the ice shelf cavity model PICO (Potsdam Ice-shelf Cavity mOdel). As ice shelf cavities are not resolved by MOM5 but are parameterized with the PICO box model, the framework allows the ice sheet and ocean components to be run at resolutions of 16 km and 3∘ respectively. This approach makes the coupled configuration a useful tool for the analysis of interactions between the Antarctic Ice Sheet and the global ocean over time spans of the order of centuries to millennia. In this study, we describe the technical implementation of this coupling framework: sub-shelf melting in the ice sheet component is calculated by PICO from modelled ocean temperatures and salinities at the depth of the continental shelf, and, vice versa, the resulting mass and energy fluxes from melting at the ice–ocean interface are transferred to the ocean component. Mass and energy fluxes are shown to be conserved to machine precision across the considered component domains. The implementation is computationally efficient as it introduces only minimal overhead. Furthermore, the coupled model is evaluated in a 4000 year simulation under constant present-day climate forcing and is found to be stable with respect to the ocean and ice sheet spin-up states. The framework deals with heterogeneous spatial grid geometries, varying grid resolutions, and timescales between the ice and ocean component in a generic way; thus, it can be adopted to a wide range of model set-ups.

Invertebrates assemblage captured by a pink shrimp's fishery on Amazon continental shelf

Shrimp trawl fisheries constitute a major threat to continental shelves' biodiversity, given their profound impact on benthic communities. We investigated the composition of an invertebrate assemblage impacted by this type of fishery and possible correlations of the abundance and richness with specific environmental parameters. The activities of the industrial shrimp fleet on the north coast of Brazil were monitored over two years. We analyzed 20,303 specimens belonging to seven phyla (Porifera, Cnidaria, Mollusca, Sipuncula, Annelida, Arthropoda, Echinodermata) and 154 species. There was a predominance of generalist and rare species, given that most species (86) were sporadic. Taxonomic composition patterns were complex, dynamic, and were correlated mainly with the temperature and depth of the Amazon continental shelf, the largest in extension and low depth of the South Atlantic. The crustaceans were dominant in both abundance and taxonomic richness. The influence of environmental factors on the abundance of the main species is discussed. The invertebrates are a neglected component in studies of fisheries impact and important components of the ecological structure of the Amazon coast. They are an essential group for developing a holistic fisheries management approach, which will support the sustainability of the region's fisheries and preserve local aquatic communities.

Drivers for spatial modelling of a critically endangered seabird on a dynamic ocean area: Balearic shearwaters are non‐vegetarian

AbstractSpatial modelling is an important research tool to improve our knowledge about the distribution of wildlife in the ocean. Using different modelling techniques (MaxEnt and a generalized linear mixed model), a predictive habitat suitability model was developed for one of the most threatened seabirds in the world: the Balearic shearwater,Puffinus mauretanicus.Models were developed using a 10‐year dataset from the Gulf of Cádiz (on the south‐western Iberian Peninsula), a key foraging area for Balearic shearwaters during migration and the non‐breeding season.Predictive habitat maps strongly matched the observed distribution patterns, pointing to bathymetric features as the main modelling drivers. The species was concentrated on shallow areas (up to approximately 100 m in depth) of the continental shelf, very close to the mouth of the Guadalquivir River. In contrast with previous studies, Balearic shearwater distribution in the highly dynamic Gulf of Cádiz was not correlated with areas of high chlorophyllaconcentration.This lack of spatial correlation probably arises from the delay between the phytoplankton bloom and the response of the zooplankton and small fish that are preyed upon by Balearic shearwaters, which may result in important displacements of this trophic chain across the Gulf of Cádiz.The analysis presented contributes to a better understanding of the spatial distribution and ecology of the critically endangered top predator in the Gulf of Cádiz and offers important information to improve management plans.

A Win-Win for Deep-Sea Corals and Fishing: Increasing Seafloor Protections While Restoring Fishing Opportunities Off the United States West Coast

On January 1, 2020, the United States (U.S.) government implemented new regulations increasing total closed areas to bottom trawl fishing by 363,513 km2, including a net increase of 44,498 km2 in essential fish habitat conservation areas at fishable depths (<1,280 m) along the West Coast continental shelf and upper slope. At the same time, the government reopened certain bottom trawl fishing grounds originally established to rebuild overfished groundfish. In combination with previously existing conservation areas, the result of these regulations is that bottom trawl fishing is now prohibited in 90% (739,491 km2) of ocean waters in the United States West Coast Exclusive Economic Zone, including 32.6% of shelf (<200 m) depth zones and 56.0% of upper slope depth zones (200-1,280 m), with a disproportionate focus on priority habitat features that are proxies for fish habitat, sensitivity to bottom trawling, and biodiversity. The final spatial management measures include 53 new or modified habitat conservation areas closed to bottom trawling in fishable depths (<1,280 m) and a precautionary prohibition on all bottom contact fishing gears at depths greater than 3,500 m. Together the final set of habitat conservation area closures and openings result in an overall increase in coastwide protections for hard, mixed, and soft substrates; seamounts; submarine canyons; and known and predicted coral, sponge, and pennatulid locations. Finer scale analyses indicate net increases or no change in coral and sponge observations inside protected areas across all regions and depth zones, despite some reductions in total area and hard substrate protected in certain regions. Based on historic bottom trawl effort data, we estimate that the opening of previously closed areas restores 24.6% of fishing effort that was displaced by bottom trawl closures implemented prior to 2020. Here we describe the involvement and approach of the conservation organization, Oceana, to protect seafloor habitats off the United States West Coast, which included a coastwide proposal to modify conservation areas, geospatial analyses, grassroots organizing, media stories, and scientific expeditions using remotely operated vehicles. Our comparison of the new versus previous assemblage of habitat conservation areas demonstrates increased overall habitat protection and fishing opportunities throughout depths and bioregions off the United States West Coast.

Upper Bathyal Pacific Ocean biogeographic provinces from octocoral distributions

Biogeographical classification schemes such as the Marine Ecoregions of the World (MEOW) have been developed for continental shelf depths. The lack of faunal data in the deep sea has led to the development of biogeographical units based on oceanographic characteristics. The aim of this study was to propose biogeographical schemes for the Upper Bathyal (200–1000 m) across the Pacific Ocean using octocoral distributions. We retrieved over 200 000 octocoral data records from the Deep Sea Coral Data Portal (DSCDP), Ocean Biogeographic Information System (OBIS), Tropical Deep-Sea Benthos program (French National Museum of Natural History), Queensland Museum from the CIDARIS expeditions, and records retrieved from the Siboga expedition reports. We used cluster analysis to examine octocoral distributions against four different biogeographical classification schemes. The classification schemes produced mostly concordant patterns with three major faunal distribution barriers: the North Pacific Current isolates the subarctic units by creating a steep temperature gradient; the Subantarctic Front separates the Subantarctic from the rest of the Pacific; and the East Pacific Barrier separates the East Pacific from the Central and West Pacific. Two other smaller but distinct provinces are the Indo-Pacific where Lower Bathyal genera are found in the Upper Bathyal, and Torres Strait/Coral Sea characterised by mesophotic genera. We propose 12 biogeographic provinces across the Pacific Ocean Upper Bathyal region from 200 to 1000 m depth based on octocoral distributions. The main driver for these units seems to be temperature, a defining feature of water masses. These units could potentially be subdivided into smaller regions based on habitat. Additionally, the clustering of Ecological Marine Units (EMUs) provides evidence that the Upper Bathyal should in certain regions be divided vertically into two depth zones based on water masses.

Перенос свободного метана струйными газовыделениями из анаэробных в аэробные воды Чёрного моря

«Дыхание недр» в форме метановых струйных газовыделений из морского дна (метановые сипы, или пузырьковые эманации) — явление планетарного масштаба, на которое обратили внимание лишь в конце XX столетия. Изучение этого явления как важного звена процессов взаимодействия литосферы, гидросферы, атмосферы и биосферы не потеряло своей актуальности до настоящего времени. В данной работе определены потоки метана в известном районе интенсивных метанопроявлений биогенной природы, географически привязанных к палеоруслу р. Днепр в северо-западной части Чёрного моря. Впервые оценено, что поток струйного (свободного) метана из анаэробных в аэробные воды на участке активных метановых газовыделений в районе палеорусла р. Днепр в диапазоне глубин 140–725 м составляет (в среднем по участку) 1,2·10³ м³·км−2·год−1 (STP), или 2,8 % от выделившегося из дна струйного метана. Величина исследованного потока — 4,2 % от удельного потока струйного метана в водный столб на шельфовом участке (глуби́ны менее 140 м) в этом же районе. Полученная в работе оценка потока метана — значимый экологический фактор в условиях стратификации вод Чёрного моря, где перенос метана струйными газовыделениями является основным механизмом внесения глубоководного метана в биогеохимические циклы и процессы трансформации углерода аэробной зоны Чёрного моря.