Strait Region Research Articles

Voyaging towards the future: the brig Rurik in the North Pacific and the emerging science of the sea.

This article explores the networking activities of Count Nikolai Rumiantsev and Adam von Krusenstern, his close collaborator. The visionary Russian statesman and the celebrated navigator were deeply involved in northern exploration. They funded and organized a circumnavigating voyage by the brig Rurik in 1815-18, with the explicit goals of searching for a northern passage between Eurasia and North America and conducting a series of scientific investigations in the Bering Strait region. This private exploratory enterprise profoundly influenced the exchange of information and reconfigured both local and global networks of knowledge. Based on an analysis of private correspondence, printed accounts and journal articles related to the Rurik's expedition, this study sheds light on how this transnational network of actors emerged and functioned, and how it promoted a lively circulation of information about exploration in the Bering Strait region in the 1810s-1820s. I argue that a complex interplay of geopolitical and intellectual competition, with exchanges, collaborations and coordination among various actors (e.g. patrons, navigators, scholars, entrepreneurs and publishers), stimulated further research on the global ocean's northern spaces and laid the foundations of marine science.

SUCCESS STORY TO ERADICATE THE MARINE POLLUTION IN INTERNATIONAL STRAIT OR STRAIT FOR INTERNATIONAL TRADE

Marine pollution has a significant impact on the waters of the coastal states, especially in the strait routes used for international trade. The traffic density of large ships which is not proportional to the wide geographical conditions, makes the Strait of Malacca a potential area that is prone to high marine pollution. This article aims to examine the use of the Marine Electronic Highway in the Malacca Strait and the success story which is applied to the territorial waters of other countries that have the same conditions. The results of the study show that in the Dover strait region, the French and British Governments are collaborating by investing in infrastructure to regulate the navigation of these areas. Meanwhile, at The Torres Straits, the Australian Government implemented a Pilotage policy by requiring ships passing through to pay a maintenance fee of 3% for the conservation of the waterways and security zones. However, the Indonesian and Malaysian governments had to negotiate beforehand to determine the delimitation of their respective maritime boundaries in Malacca Straits.

Prediction of Northern Hemisphere Regional Sea Ice Extent and Snow Depth Using Stratospheric Ozone Information

AbstractThe forecast potential of springtime ozone on April surface temperatures at particular locations in the Northern Hemisphere has been previously reported. Evidence suggests that early springtime Arctic stratospheric ozone acts as a proxy for extreme events in the winter polar vortex. Here, using a state‐of‐the‐art chemistry‐climate model, reanalysis and observations, we extend the forecast potential of ozone on surface temperatures to aspects of the Northern Hemisphere cryosphere. Sea ice fraction and sea ice extent differences between years of March high and low Arctic stratospheric ozone extremes show excellent agreement between an ensemble of chemistry‐climate model simulations and observations, with differences occurring not just in April but extending through to the following winter season in some locations. Large snow depth differences are also obtained in regional locations in Russia and along the southeast coast of Alaska. These differences remain elevated until early summer, when snow cover diminishes. Using a conditional empirical model in a leave‐three‐out cross validation method, March total column ozone is able to accurately predict the sign of the observed sea ice extent and snow depth anomalies over 70% of the time during an ozone extreme year, especially in the region of the Bering strait and the Greenland Sea, which could be useful for shipping routes and for testing climate models.

Die–offs, reproductive failure, and changing at–sea abundance of murres in the Bering and Chukchi Seas in 2018

Common and thick–billed murres are among the most numerous and widespread seabirds in the northern hemisphere though they appear to be especially susceptible to mass die–off events. During the spring and summer of 2018, the Bering Sea experienced warmer than average sea temperatures following a winter of unprecedented, near complete lack of sea ice. To determine if breeding murres were negatively affected by these warm sea temperatures, surveys at most of the major murre breeding colonies in the eastern Bering and eastern Chukchi seas were conducted during the 2018 breeding season. Nearly all colonies surveyed experienced near-complete reproductive failure. Concurrently, above average levels of murre mortality were observed, primarily at St. Lawrence Island and in the Bering Strait region. The timing of this mortality is somewhat unusual and concerning as it occurred during the breeding season. Based on surveys at sea, overall murre abundance offshore was generally lower in 2018 compared to recent years (2012–2017), particularly in the northern Bering Sea, yet mean density for thick–billed murres increased in the Chukchi Sea. Reproductive failure is rare at monitored murre colonies within the study area and the widespread reproductive failures observed in 2018 were unprecedented over four decades of monitoring, but consistent with the reproductive failure of murres documented in the Gulf of Alaska and southeastern Bering Sea following a large murre die–off in 2015–2016. The combination of large–scale reproductive failure, evidence of elevated levels of mortality, and low abundance of birds offshore suggest that murres experienced severe distress in the Bering and Chukchi sea region during the summer of 2018.

The influence of Arctic Fe and Atlantic fixed N on summertime primary production in Fram Strait, North Greenland Sea

Climate change has led to a ~ 40% reduction in summer Arctic sea-ice cover extent since the 1970s. Resultant increases in light availability may enhance phytoplankton production. Direct evidence for factors currently constraining summertime phytoplankton growth in the Arctic region is however lacking. GEOTRACES cruise GN05 conducted a Fram Strait transect from Svalbard to the NE Greenland Shelf in summer 2016, sampling for bioessential trace metals (Fe, Co, Zn, Mn) and macronutrients (N, Si, P) at ~ 79°N. Five bioassay experiments were conducted to establish phytoplankton responses to additions of Fe, N, Fe + N and volcanic dust. Ambient nutrient concentrations suggested N and Fe were deficient in surface seawater relative to typical phytoplankton requirements. A west-to-east trend in the relative deficiency of N and Fe was apparent, with N becoming more deficient towards Greenland and Fe more deficient towards Svalbard. This aligned with phytoplankton responses in bioassay experiments, which showed greatest chlorophyll-a increases in + N treatment near Greenland and + N + Fe near Svalbard. Collectively these results suggest primary N limitation of phytoplankton growth throughout the study region, with conditions potentially approaching secondary Fe limitation in the eastern Fram Strait. We suggest that the supply of Atlantic-derived N and Arctic-derived Fe exerts a strong control on summertime nutrient stoichiometry and resultant limitation patterns across the Fram Strait region.

Satellite-based assessment of the long-term efficacy of PM2.5 pollution control policies across the Taiwan Strait

Evaluating the efficacy of air pollution control policies is an essential part of the decision-making process to develop new policies and improve existing measures. Since 2005, Fujian Province of Mainland China and Taiwan across the Taiwan Strait have both implemented aggressive air pollution control policies designed based on different principles, but a comprehensive evaluation of these control policies on PM2.5pollution levels is still lacking. In the current study, we assessed the effects of these policies in the Taiwan Strait Region from 2005 to 2018 using full-coverage, high-resolution PM2.5generated by a satellite-driven machine learning model. A ten-fold cross-validation for our prediction model showed an R2value of 0.89, demonstrating that these predictions can be used for policy evaluation. During the 14-year period, PM2.5levels in all areas of Fujian and Taiwan underwent a significant decrease. Separate regression models for policy evaluation in Taiwan and Fujian showed that all considered policies have mitigated PM2.5pollution to various degrees. The Clean Air Action Plans (CAAP) is the most effective control policy in Taiwan, while the Action Plan of Air Pollution Prevention and Control (APPC-AP) and Three-year Action Plan for Blue Skies (3YAP-BS) as well as their provincial implementation plans are the most successful in Fujian. The effectiveness of control policies, however, varies by land-use types especially for Taiwan.

Using genomic tools to inform management of the Atlantic northern fulmar

Highly migratory species pose unique conservation and management challenges, especially when significant mortality occurs away from breeding concentrations. Population genetics and genomics may help with the appropriate management of these species by (1) determining the population genetic structure of a species across its range, and (2) allowing the assignment of individuals to their breeding source. The northern fulmar (Fulmarus glacialis; Procellariiformes: Procellariidae) is a seabird species that breeds in colonies throughout the North Atlantic and Pacific oceans. This species ranges widely across ocean basins during the non-breeding season and is exposed to a variety of threats throughout the annual cycle. The impact of mortality during the nonbreeding season on individual breeding colonies is unknown but has important ramifications for conservation and management. In this study we used restriction site-associated DNA sequencing (RADseq) to provide 6614 genome-wide single nucleotide polymorphisms (SNPs) to investigate population genetic structure of northern fulmars using 127 individuals from six breeding colonies spanning the Atlantic. Additionally, birds of unknown breeding origin were sampled from two locations: (1) offshore in the Labrador Sea, and (2) the Baffin Bay-Davis Strait region (NAFO subarea 0), as bycatch in gillnets set for Greenland halibut (Reinhardtius hippoglossoides). We found weak genetic differentiation among breeding colonies, which we suggest reflects historical associations as well as contemporary gene flow among populations. Most bycatch birds were likely from nearby breeding colonies in the eastern Canadian Arctic, but the exact breeding origins were difficult to determine due to the lack of differentiation between colonies.

Empirical Relationships between Remote-Sensing Reflectance and Selected Inherent Optical Properties in Nordic Sea Surface Waters for the MODIS and OLCI Ocean Colour Sensors

The Nordic Seas and the Fram Strait regions are a melting pot of a number of water masses characterized by distinct optical water properties. The warm Atlantic Waters transported from the south and the Arctic Waters from the north, combined with the melt waters contributing to the Polar Waters, mediate the dynamic changes of the year-to-year large-scale circulation patterns in the area, which often form complex frontal zones. In the last decade, moreover, a significant shift in phytoplankton phenology in the area has been observed, with a certain northward expansion of temperate phytoplankton communities into the Arctic Ocean which could lead to a deterioration in the performance of remote sensing algorithms. In this research, we exploited the capability of the satellite sensors to monitor those inter-annual changes at basin scales. We propose locally adjusted algorithms for retrieving chlorophyll a concentrations Chla, absorption by particles ap at 443 and 670 nm, and total absorption atot at 443 and 670 nm developed on the basis of intensive field work conducted in 2013–2015. Measured in situ hyper spectral remote sensing reflectance has been used to reconstruct the MODIS and OLCI spectral channels for which the proposed algorithms have been adapted. We obtained MNB ≤ 0.5% for ap(670) and ≤3% for atot(670) and Chla. RMS was ≤30% for most of the retrieved optical water properties except ap(443) and Chla. The mean monthly mosaics of ap(443) computed on the basis of the proposed algorithm were used for reconstructing the spatial and temporal changes of the phytoplankton biomass in 2013–2015. The results corresponded very well with in situ measurements.

Seasonal gene expression profiling of Antarctic krill in three different latitudinal regions.

The Antarctic krill, Euphausia superba, has evolved seasonal rhythms of physiology and behaviour to survive under the extreme photoperiodic conditions in the Southern Ocean. However, the molecular mechanisms generating these rhythms remain far from understood. The aim of this study was to investigate seasonal differences in gene expression in three different latitudinal regions (South Georgia, South Orkneys/Bransfield Strait, Lazarev Sea) and to identify genes with potential regulatory roles in the seasonal life cycle of Antarctic krill. The RNA-seq data were analysed (a) for seasonal differences between summer and winter krill sampled from each region, and (b) for regional differences within each season. A large majority of genes showed an up-regulation in summer krill in all regions with respect to winter krill. However, seasonal differences in gene expression were less pronounced in Antarctic krill from South Georgia, most likely due to the milder seasonal conditions of the lower latitudes of this region, with a less extreme light regime and food availability between summer and winter. Our results suggest that in the South Orkneys/Bransfield Strait and Lazarev Sea region, Antarctic krill entered a state of metabolic depression and regressed development (winter quiescence) in winter. Moreover, seasonal gene expression signatures seem to be driven by a photoperiodic timing system that may adapt the flexible behaviour and physiology of Antarctic krill to the highly seasonal environment according to the latitudinal region. However, at the lower latitude South Georgia region, food availability might represent the main environmental cue influencing seasonal physiology.

Analyzing Collision, Grounding, and Sinking Accidents Occurring in the Black Sea Utilizing HFACS and Bayesian Networks.

This study examines and analyzes marine accidents that have occurred over the past 20 years in the Black Sea. Geographic information system, human factor analysis and classification system (HFACS), and Bayesian network models are used to analyze the marine accidents. The most important feature distinguishing this study from other studies is that this is the first study to analyze accidents that have occurred across the whole Black Sea. Another important feature is the application of a new HFACS structure to reveal accident formation patterns. The results of this study indicate that accidents occurred in high concentrations in coastal regions of the Black Sea, especially in the Kerch Strait, Novorossiysk, Kilyos, Constanta, Riva, and Batumi regions. The formation of grounding and sinking accidents has been found to be similar in nature; the use of inland and old vessels has been highlighted as important factors in sinking and grounding incidents. However, the sequence of events leading to collision-contact accidents differs from the sequence of events resulting in grounding and sinking accidents. This study aims to provide information to the maritime industry regarding the occurrence of maritime incidents in the Black Sea, in order to assist with reduction and prevention of the marine accidents.

Tectonostratigraphy and evolution of the West Greenland continental margin

Large structural highs and sedimentary basins are identified from mapping of the West Greenland continental margin from the Labrador Sea to the Baffin Bay. We present a new tectonic elements map and a map of thickness from the seabed to the basement of the entire West Greenland margin. In addition, a new stratigraphic scheme of the main lithologies and tectonostratigraphy based on ties to all offshore exploration wells is presented together with seven interpreted seismic sections. The work is based on interpretation of more than 135 000 km of 2D seismic reflection data supported by other geophysical data, including gravity- and magnetic data and selected 3D seismic data, and is constrained by correlation to wells and seabed samples. Eight seismic mega-units (A–H) from the seabed to the basement, related to distinct tectonostratigraphic phases, were mapped. The oldest units include pre-rift basins that contain Proterozoic and Palaeozoic successions. Cretaceous syn-rift phases are characterised by development of large extensional fault blocks and basins with wedge-shaped units. The basin strata include Cretaceous and Palaeogene claystones, sandstones and conglomerates. During the latest Cretaceous, Paleocene and Eocene, crustal extension followed by oceanic crust formation took place, causing separation of the continental margins of Greenland and Canada with north-east to northward movement of Greenland. From Paleocene to Eocene, volcanic rocks dominated the central West Greenland continental margin and covered the Cretaceous basins. Development of the oceanic crust is associated with compressional tectonics and the development of strike-slip and thrust faults, pull-apart basins and inversion structures, most pronounced in the Davis Strait and Baffin Bay regions. During the late Cenozoic, tectonism diminished, though some intra-plate vertical adjustments occurred. The latest basin development was characterised by formation of thick Neogene to Quaternary marine successions including contourite drifts and glacial related shelf progradation towards the west and south-west.

Efficacy of marine cyanobacterium Oxynema thaianum ALU PBC5 against multi drug resistant Gram negative pathogens.

Emergence of extended antibiotic resistance among several human bacterial pathogens often leads to the failure of existing antibiotics to treat bacterial infections worldwide. Hence, the present study is aimed to explore antibacterial activity of marine cyanobacterium against MDR pathogens. The cyanobacterial samples were collected and isolated from Thondi Palk Strait region. The isolate was subjected to polarity based solvent extraction and checked for their antibacterial activity against test bacterial pathogens. The active principles from chloroform extract of Oxynema thaianum (CEOT) were partially purified through thin layer chromatography (TLC). The active principle with highest activity was further characterized by FTIR, high performance liquid chromatography (HPLC) and gas chromatography mass spectrometry (GC-MS) analysis. Among the eight extracts tested, CEOT showed effective zone of clearance against ESBL producing Escherichia coli and Klebsiella pneumoniae in disc diffusion method. In TLC, all the purified five fractions were eluted and tested for their antibacterial activity against test pathogens. The third fraction showing maximum activity was subjected to HPLC analysis for checking its purity. In GC-MS analysis, 9-octadecenoic acid, methyl ester and hexadecanoic acid were identified as the major chemical compounds. Hence, the present study was concluded that O. thaianum ALU PBC5 is a promising agent to treat ESBL producing MDR bacterial pathogens. This is the pioneer study on screening and isolation of bioactive compounds from the marine cyanobacteria against MDR pathogens such as E. coli and K. pneumoniae. Here, 9-octadecenoic acid, methyl ester and hexadecanoic acid were identified as the major chemical compounds through TLC, FTIR, HPLC and GC-MS. From this screen, we identified the bioactive compounds against ESBL producing multidrug resistant pathogens such as E. coli and K. pneumoniae.

Polycyclic aromatic compounds (PACs) and trace elements in four marine bird species from northern Canada in a region of natural marine oil and gas seeps

There is a growing understanding of how oil pollution can affect aquatic ecosystems, including physical and chemical effects. One of the biggest challenges with detecting the effects of oil-related contaminants on biota from resource development is understanding the background levels and potential effects of the exposure of biota to contaminants from various natural and anthropogenic sources prior to large scale oil and gas operations. Seabirds are effective indicators of pollution, and can be useful for tracking oil-related contaminants in the marine environment. We sampled four seabird species (black guillemot, Cepphus grylle; thick-billed murre, Uria lomvia; black-legged kittiwake, Rissa tridactyla; and northern fulmar, Fulmarus glacialis) in the Baffin Bay-Davis Strait region of the Northwest Atlantic and Arctic oceans, an area where natural oil and gas seeps are present but lacking any large-scale oil and gas projects. We found detectable levels of PACs and several trace elements in all species examined. Alkylated PAC levels were higher than parent compounds in all four seabird species examined, with fulmars and murres having the highest levels detected; mean hepatic concentrations of ∑16PAC were 99.05, 46.42, 12.78 and 9.57 ng/g lw, respectively, for guillemots, murres, fulmars and kittiwakes. Overall, PAC concentrations in the seabird species examined were similar to PAC concentrations measured in other bird species in regions with more industrialization. These findings provide data which can be used to assess the current oil-related contaminant exposure of biota in the region. As well, they provide background levels for the region at a time when shipping activity is relatively low, which can used for future comparisons following expected increases in shipping and oil and gas activities in the region.

Acceptability and Usability of Computerized Cognitive Assessment Among Australian Indigenous Residents of the Torres Strait Islands.

This cross-sectional study aimed to investigate the acceptability and usability of the Cogstate Brief Battery (CBB) in a community-based sample of Australian Indigenous people from the Torres Strait region, based on a user experience framework of human-computer interaction. Two-hundred community participants completed the four subtests of the CBB on an iPad platform, during a free adult health check on two islands in the region, between October and December 2016. Acceptability was defined as completing the learning trial of a task and usability as continuing a task through to completion, determined by examiner acumen and internal Cogstate completion and integrity criteria. These were combined into a single dichotomous completion measure for logistic regression analyses. Performance-measured as reaction times and accuracy of responses-was analyzed using linear regression analyses. CBB completion ranged from 82.0% to 91.5% across the four tasks and the odds of completing decreased with age. After adjusting for age, iPad/tablet familiarity increased the odds of completion for all tasks while level of education and employment increased the odds for some tasks only. These variables accounted for 18.0%-23.8% of the variance in reaction times on speeded tasks. Age and education had the most effect, although semipartial correlations were modest. When administered in a health-screening context, the acceptability and usability of the CBB were greatest in young- to middle-aged participants with some education and iPad/tablet experience. Older and more vulnerable participants may have benefited from additional time and practice on the CBB prior to administration.

Summertime Chlorophyll a and Particulate Organic Carbon Standing Stocks in Surface Waters of the Fram Strait and the Arctic Ocean (1991–2015)

Sea ice in the Arctic Ocean has been undergoing dramatic changes during the last two decades. In addition, the water temperature of the inflow of Atlantic water masses at the gateway Fram Strait has recently increased. Long-term data may help to evaluate the impact of these physical changes on the biological processes in surface waters. Over a 25-year period, and mostly in summer, water samples were collected at discrete depths within the uppermost 100 m of the Fram Strait and other regions of the Arctic Ocean (AO) to investigate chlorophyll a (Chl a) and particulate organic carbon (POC) standing stocks. Stations sampled from 1991 to 2015 were located in the Fram Strait, Barents Sea, on the Eurasian shelf, and over the Nansen, Amundsen, and parts of the Amerasian basins. Discrete Chl a and POC measurements obtained during 33 and 24 expeditions, respectively, were integrated over the upper 100 m of the water column to monitor spatial and interannual variations in distribution patterns of standing stocks. In general, the highest Chl a and POC standing stocks were observed in the eastern Fram Strait and in the Barents Sea, while the lowest biomasses were observed in the heavily ice-covered regions of the central AO, mainly in the Amundsen and Amerasian basins. Whereas summertime Chl a stocks sharply decreased northwards from the Fram Strait and Barents Sea towards high latitudes, the decline in POC standing stocks was less pronounced. Over the sampling period, summertime Chl a stocks slightly increased in the eastern Fram Strait but remained more or less constant in the central AO. In contrast to Chl a, standing stocks of POC eventually increased over the last 25 years in the central AO, possibly as an effect of increasing air temperatures, decreasing sea ice extent and thickness, and increasing light availability. Moreover, variations in riverine discharge and in sea ice export within the Transpolar Drift may have contributed to the enhanced POC stock in the central AO surface waters.

Seasonal trends in underwater ambient noise near St. Lawrence Island and the Bering Strait

We measured spatial and temporal patterns of ambient noise in dynamic, relatively pristine Arctic marine habitats and evaluate the contributions of environmental and human noise sources. Long-term acoustic recorders were deployed around St. Lawrence Island and the Bering Strait region within key feeding and migratory corridors for protected species that are inherently important to Native Alaskan cultures. Over 3000 h of data from 14 recorders at nine sites were obtained from October 2014 to June 2017. Spatial and temporal ambient noise patterns were quantified with percentile statistics in 1/3rd-octave bands (0.02–8 kHz). Ice presence strongly influenced ambient noise by influencing the physical environment and presence of marine mammals. High variability in noise was observed within and between sites, largely as a function of ice presence and associated factors. Acute contributions of biological and anthropogenic sources to local ambient noise are compared to monthly averages, demonstrating how they influence Arctic soundscapes.

Variability in fin whale (Balaenoptera physalus) occurrence in the Bering Strait and southern Chukchi Sea in relation to environmental factors

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 in years and at sites where productive water masses were present, indicated by low temperatures and high salinities, and where strong northward water and wind velocities, resulting in increased prey advection, were prevalent. Using acoustic recordings from three moored hydrophones in the Bering Strait region from 2009–2015, we identified fin whale calls during the open-water season (July–November) and investigated potential environmental drivers of interannual variability in fin whale presence. We examined near-surface and near-bottom temperatures (T) and salinities (S), wind and water velocities through the strait, water mass presence as estimated using published T/S boundaries, and satellite-derived sea surface temperatures and sea-ice concentrations. Our results show significant interannual variability in the acoustic presence of fin whales with the greatest detections of calls in years with contrasting environmental conditions (2012 and 2015). Colder temperatures, lower salinities, slower water velocities, and weak southward winds prevailed in 2012 while warmer temperatures, higher salinities, faster water velocities, and moderate southward winds prevailed in 2015. Most detections (96%) were recorded at the mooring site nearest the confluence of the nutrient-rich Anadyr and Bering Shelf water masses, ~35 km north of Bering Strait, indicating that productive water masses may influence the occurrence of fin whales. The disparity in environmental conditions between 2012 and 2015 suggests there may be multiple combinations of environmental factors or other unexamined variables that draw fin whales into the Pacific Arctic.

Tsunamiopasnost' Krymskogo poberezh'ya Chernogo morya i Kerchenskogo proliva pri katastroficheskih tsunamigennyh zemletryaseniyah, blizkih po lokalizatsii k istoricheskomu YAltinskomu zemletryaseniyu 12 sentyabrya 1927 goda

Purpose. The main purpose of the work is to assess a possible tsunami hazard for the region of location of the Crimean Bridge constructed across the Kerch Strait, since up to present, numerical simulations of the tsunamigenic earthquakes in the Black Sea have never taken the Kerch Strait region (except for the water area at the strait entrance) into consideration as a possible object for a tsunami hazard. Methods and Results. To assess a tsunami hazard for the Kerch Strait and, particularly, for the region of location of the constructed Crimean Bridge, the present paper considers the historical catastrophic tsunamigenic earthquake in the southeastern part of the Crimea Peninsula on September 12, 1927 as well as possible strong earthquakes, the source locations and magnitudes of which can be close to those of the above-mentioned one. The available data on localization and intensity of the earthquake on September 12, 1927 allowed to model the source of such an earthquake. Besides, within the framework of the nonlinear shallow water equations, simulated were the tsunami generation and the tsunami waves’ propagation from the single- and two-block seismic sources in the Black Sea along the Crimea Peninsula, at the Kerch Strait entrance and in its water area. The seismic sources of close localization were similarly simulated for two possible tsunamigenic earthquakes in the southeastern part of the Crimea Peninsula. Conclusions. For all the considered scenarios, generation and propagation of the tsunami waves over the water area regions under study were numerically simulated, the histograms of distribution of the wave run-up maximum heights along the Crimea Peninsula and the Kerch Strait coasts were constructed. It is shown that for all the scenarios, in the region of the Crimean Bridge western pillars the tsunami wave heights do not exceed 0.3–0.5 m, whereas in the region of its eastern pillars, possible wave heights are within the range 0.6–1.95 m. The results represented in the paper are compared with the available data on the wave heights in a number of settlements of the Crimea Peninsula coast and at the Kerch Strait entrance, obtained by the other authors.

Swordfish Xiphias gladius diet in the Florida Straits

Swordfish Xiphias gladius inhabit the Florida Straits year-round and provide a significant role in the food web as top-level predators. However, little is known about the diet composition and thus ecological role of swordfish in Florida. This study investigated swordfish diet by analyzing stomach contents of 131 swordfish in the Florida Straits from April 2007 to December 2008. Identifiable species included 13 teleost species, 3 cephalopod species, and 1 crustacean species. Cephalopods dominated the swordfish diet by weight (72.4%) and number (69.9%), and ranked highest in importance in the diet by the index of relative importance (IRI; 81.5%). Teleosts occurred the most (99.1%) but represented the second highest importance in diet by weight (25.2%), number (26.3%), and IRI (17.6%). Illex sp. was the prey with the greatest dietary importance, followed by unidentifiable ommastrephid squids. Stomach fullness index values ranged from 0 (empty) to 8.98 (mean = 0.37). A positive significant correlation between swordfish length and prey length was found (r2 = 0.104, P = 0.037), and no significant correlations were found between swordfish weight and prey weight (r2 = –0.075, P = 0.065). This is the first study to report a comprehensive diet of swordfish inhabiting waters in the Florida Straits region and suggests swordfish may be opportunistic feeders, altering their diet when abundance or presence of prey changes.

Diversity and biogeography of picoplankton communities from the Straits of Malacca to the South China Sea

Abstract Marine picoplankton, including prokaryotic and eukaryotic picoplankton, drive many biogeochemical processes, such as carbon, nitrogen and sulfur cycles, making them crucial to the marine ecosystem. Despite the fact that picoplankton is prevalent, its diversity and spatial distribution from the Straits of Malacca (SM) to the South China Sea (SCS) remain poorly investigated. This work explores the phylogenetic diversity and community structure of picoplankton in relation to environmental factors from the SM to the SCS. To this end, the Illumina MiSeq sequencing technique was applied to 16S and 18S rRNA genes. The results showed significant differences in the dynamics of picoplankton between the open sea and the strait region. Proteobacteria and Cyanobacteria constituted a larger part of the prokaryotic group. Within Cyanobacteria, the abundance of Prochlorococcus in the open sea was significantly higher than that of Synechococcus, while the opposite trend was observed in the strait. Dinoflagellata, Cnidaria, Retaria, Tunicata, and Arthropoda dominated among the eukaryotic taxa. High-throughput sequencing data indicated that salinity, temperature and NO2-N were the key factors determining the prokaryotic community structure, while temperature and dissolved oxygen determined the eukaryotic community structure in the studied region. The network analysis demonstrated that the cooperation and competition were also important factors affecting the picoplankton community.