World Ocean Research Articles

Coastal foredune enlargement – a sign of sea-level change? An example from the Kavatsite beach-dune system

Sea level rise is one of the effects of climate change and the Black Sea is affected, regardless its isolated position from the World Ocean. As a consequent, in various locations worldwide is reported shifting of foredune ridges towards inland and overlapping of newly formed ridges over older secondary features, as parabolic dunes, dune fields, etc. During the field study in 2023, in the Kavatsite foredune ridge was observed such migration of newly formed accumulations on older grey dunes. Comparative analysis of UAV-based photogrammetry and generated orthophoto mosaic overlaid to archive aerial images from the early 20th century showed over 20 m migration of the primary dune ridge inland and also increased beach erosion. Regarding the accelerating sea rise tendency, special attention should be taken to the anthropogenic activities in the coastal zone, including the beach-dune systems – the first natural barrier to the wave action on coasts.

A first account of pteropod taxa from off Saurashtra, western offshore of India: Implications for palaeohydrological studies

Pteropod aragonitic shells contribute to 12% of biogenic inorganic carbon flux to the world ocean but are also prone to dissolution. Though their state of preservation and generic ratios, namely Creseis/Limacina have been used as a proxy for palaeoclimatic reconstruction, their taxonomic attributes have remained unexplored. The present study reports 20 pteropod species from a single location in the northeastern Arabian Sea offshore of Saurashtra, all of which show the same degree of preservation throughout the core. The occurrence of mesopelagic fauna in the study area located on the shelf region however points to palaeoenvironmental changes and underscores the importance of employing pteropod assemblages for palaeoclimatic reconstructions in the study area.

Analysis of microplastics in ships ballast water and its ecological risk assessment studies from the Persian Gulf

Transport of ballast water is considered a significant vector for dispersion of different pollutants, including microplastics (MPs), throughout the world's oceans. However, there is limited information on MPs in ballast water. Size distribution, polymer type, and ecological risks of MPs in ballast water were investigated for the first time in this study. The mean levels of MPs in ballast water and seawater samples were 12.53 and 11.80 items/L, respectively. MPs with a size category of 50–300 μm was the most abundant. Fiber, black, and polycarbonate (PC) were the predominant shape, color, and polymer type of identified MPs in ballast water and seawater, respectively. The pollution load index (PLI), hazard index (HI), and risk quotient (RQ) indicated high levels of MP pollution, potentially indicating an ecological risk. These findings increase our understanding of the major sources (such as ballast water), transportation routes, and related ecological risks of MPs to marine ecosystems.

Sea level anomalies affect the ocean circulation at abyssal depths

Abyssal channels are the key points controlling bottom circulation of the World Ocean. They provide meridional transport of the coldest Antarctic Bottom Water between deep-water basins influencing the meridional overturning circulation and the climate on a global scale. Here we show that the synoptic variability of deep-water flows including blocking abyssal currents between deep ocean basins is related to sea level anomalies observed over the channels. Our results demonstrate that processes at the ocean surface have a more significant connection with the bottom circulation than it was considered earlier. This study opens a discussion of the importance of mesoscale eddies and air-sea interactions on water exchange between abyssal basins, meridional heat transport in the ocean, and possible responses of the ocean to the observed sea level rise in a changing climate.

HYDROGRAPHIE ACOUSTIC SYSTEMS - MEASUREMENT PRINCIPLES

Hydrography is an applied science that deals with the study of the bottom and shores of the world ocean (all oceans and seas), lakes, rivers and dams, i.e. all natural and artificial water bodies. Hydrographic research is the study of individual areas of the hydrosphere, including the design, implementation of hydrographic works, processing and analysis of the collected data.

Viral Diversity in Benthic Abyssal Ecosystems: Ecological and Methodological Considerations.

Viruses are the most abundant 'biological entities' in the world's oceans. However, technical and methodological constraints limit our understanding of their diversity, particularly in benthic abyssal ecosystems (>4000 m depth). To verify advantages and limitations of analyzing virome DNA subjected either to random amplification or unamplified, we applied shotgun sequencing-by-synthesis to two sample pairs obtained from benthic abyssal sites located in the North-eastern Atlantic Ocean at ca. 4700 m depth. One amplified DNA sample was also subjected to single-molecule long-read sequencing for comparative purposes. Overall, we identified 24,828 viral Operational Taxonomic Units (vOTUs), belonging to 22 viral families. Viral reads were more abundant in the amplified DNA samples (38.5-49.9%) compared to the unamplified ones (4.4-5.8%), with the latter showing a greater viral diversity and 11-16% of dsDNA viruses almost undetectable in the amplified samples. From a procedural point of view, the viromes obtained by direct sequencing (without amplification step) provided a broader overview of both ss and dsDNA viral diversity. Nevertheless, our results suggest that the contextual use of random amplification of the same sample and long-read technology can improve the assessment of viral assemblages by reducing off-target reads.

Physiological effects of polycyclic aromatic hydrocarbons (PAH) in fish organism

The pollution of world ocean is a serious threat to the biodiversity of flora and fauna. One of the most important sources of pollution are oil and oil products – every year more than 1 million tons of oil is spilled into the sea as a result of accidents during oil production or transportation. The teratogenic and carcinogenic effects of such oil components as benzopyrene is well known since the middle of the last century. However, after a large oil spill from “Exxon Valdez” tanker in 1989 it became clear that oil and its components have strong toxic effects in fish organism – and to a large extent these effects are caused by di- and tricyclic aromatic hydrocarbons, in particular phenanthrene. Field research have demonstrated that fish embryo and larvae are the most prone to the effects of oil – and the largest oil spills endanger the populations of important commercial fish species that spawn in this area. This review considers the influence of polycyclic aromatic hydrocarbons (PAH) on the physiology of various organ systems in fish. Particular attention is paid to the cardiotoxic effects of PAH which were recently discovered and which are potentially not only the main cause of animals’ death upon the spill of PAH into water, but also underlie the malformation of other organs.

ON THE LOGICAL FOUNDATIONS OF DIFFERENT INTERPRETATIONS OF THE “HYDROSPHERE” CONCEPT

The logical foundations of different interpretations of the fundamental “hydrosphere” concept, widely used in the Earth sciences, are discussed. Five principal interpretations of the hydrosphere notion were identified: the World Ocean; the World Ocean and all surface land waters; all surface and ground waters on the Earth; all surface and ground waters, as well as waters of the atmosphere, including atmospheric moisture; all forms of water present on the planet. Based on the concept of the phase-shell structure of the Earth, it is logically most reasonable to define the hydrosphere as a shell of the Earth, which embraces all water bodies located between the atmosphere and the lithosphere (the World Ocean, lakes, rivers, swamps, temporary and permanent snow and ice cover). The hydrosphere does not include water vapor in the atmosphere and groundwater, which are components of other geospheres, i.e. the atmosphere and the lithosphere, respectively.

STUDYING OF THE SATELLITE BASED MODELS FOR LOCAL SPATIO-TEMPORAL MONITORING OF OCEAN ACIDIFICATION IN COSTAL SEA WATER IN BLACK SEA

Due to climate changes, a number of changes are observed in the world's oceans, such as a change in the amount of thermal energy and water temperature, a change in sea and ocean currents, as well as an increase in acidification. These changes lead to a change in sea water as a habitat for marine ecosystems. Since the beginning of the new millennium, many scientific researches have been focused on monitoring and studying ocean acidification as an important indicator of climate change. The use of satellite remote sensing data to study ocean acidification is gaining wide application and is emerging as a major research method in the near future. It enables continuous near-real-time monitoring, both globally and regionally. The aim of the present study is to investigate and evaluate the possibilities of applying the models for the study of marine acidification using satellite data for a limited coastal area in the Black Sea region. A review of the publications in various scientific databases related to the major projects of international and governmental organizations such as UNESCO, IALA, EC, NOAA, etc. was made. The study takes into account the gaps in the information on the acidification of the Bulgarian coastal waters by exploring the possibilities for satellite remote monitoring, which would allow the creation of spatio-temporal and prognostic models. The global and regional coastal studies of seawater acidification with satellite data, as well as the satellite studies of the Black Sea carried out so far, give us hope that in the near future we will be able to successfully apply satellite remote sensing methods in regions such as the Bulgarian coast. However, there are currently no data on quantitative analyzes based on satellite data for the Black Sea, such as the calculations of the parameters of the carbon cycle in sea water. This leads to the impossibility of conducting satellite monitoring of acidification in our region at the present time.

Biotic response of plankton communities to Middle to Late Miocene monsoon wind and nutrient flux changes in the Oman margin upwelling zone

Abstract. Understanding past dynamics of upwelling cells is an important aspect of assessing potential upwelling changes in future climate change scenarios. Our present understanding of nutrient fluxes throughout the world's oceans emphasizes the importance of intermediate waters transporting nutrients from the Antarctic divergence into the middle and lower latitudes. These nutrient-rich waters fuel productivity within wind-driven upwelling cells in all major oceans. One such upwelling system is located along the Oman margin in the western Arabian Sea (WAS). Driven by cross-hemispheric winds, the WAS upwelling zone's intense productivity led to the formation of one of the most extensive oxygen minimum zones known today. In this study covering the Middle to Late Miocene at Ocean Drilling Program (ODP) Site 722, we investigate the inception of upwelling-derived primary productivity. This study presents new plankton assemblage data in the context of existing model- and data-based evidence constraining the tectonic and atmospheric boundary conditions for upwelling in the WAS. With this research, we build upon the original planktonic foraminifer-based research by Dick Kroon in 1991 as part of his research based on the ODP LEG 117. We show that monsoonal winds likely sustained upwelling since the emergence of the Arabian Peninsula after the Miocene Climatic Optimum (MCO) ∼ 14.7 Ma, with fully monsoonal conditions occurring since the end of the Middle Miocene Climatic Transition (MMCT) at ∼ 13 Ma. However, changing nutrient fluxes through Antarctic Intermediate and sub-Antarctic Mode Waters (AAIW/SAMW) were only established after ∼ 12 Ma. Rare occurrences of diatom frustules correspond to the maximum abundances of Reticulofenestra haqii and Reticulofenestra antarctica, indicating higher upwelling-derived nutrient levels. By 11 Ma, diatom abundance increases significantly, leading to alternating diatom blooms and high-nutrient-adapted nannoplankton taxa. These changes in primary producers are also well reflected in geochemical proxies with increasing δ15Norg. values (> 6 ‰) and high organic carbon accumulation. These proxies provide further independent evidence for high productivity and the onset of denitrification simultaneously. Our multi-proxy-based evaluation of Site 722 primary producers provides evidence for a stepwise evolution of Middle to Late Miocene productivity in the western Arabian Sea for the first time. The absence of a clear correlation with existing deep marine climate records suggests that both local wind patterns and intermediate water nutrient changes likely modulated productivity in the western Arabian Sea during the Middle to Late Miocene. Finally, we show that using a multi-proxy record provides novel insights into how plankton responded to changing nutrient conditions through time in a monsoon-wind-driven upwelling zone.

Simulations of ocean deoxygenation in the historical era: insights from forced and coupled models

Ocean deoxygenation due to anthropogenic warming represents a major threat to marine ecosystems and fisheries. Challenges remain in simulating the modern observed changes in the dissolved oxygen (O2). Here, we present an analysis of upper ocean (0-700m) deoxygenation in recent decades from a suite of the Coupled Model Intercomparison Project phase 6 (CMIP6) ocean biogeochemical simulations. The physics and biogeochemical simulations include both ocean-only (the Ocean Model Intercomparison Project Phase 1 and 2, OMIP1 and OMIP2) and coupled Earth system (CMIP6 Historical) configurations. We examine simulated changes in the O2 inventory and ocean heat content (OHC) over the past 5 decades across models. The models simulate spatially divergent evolution of O2 trends over the past 5 decades. The trend (multi-model mean and spread) for upper ocean global O2 inventory for each of the MIP simulations over the past 5 decades is 0.03 ± 0.39×1014 [mol/decade] for OMIP1, −0.37 ± 0.15×1014 [mol/decade] for OMIP2, and −1.06 ± 0.68×1014 [mol/decade] for CMIP6 Historical, respectively. The trend in the upper ocean global O2 inventory for the latest observations based on the World Ocean Database 2018 is −0.98×1014 [mol/decade], in line with the CMIP6 Historical multi-model mean, though this recent observations-based trend estimate is weaker than previously reported trends. A comparison across ocean-only simulations from OMIP1 and OMIP2 suggests that differences in atmospheric forcing such as surface wind explain the simulated divergence across configurations in O2 inventory changes. Additionally, a comparison of coupled model simulations from the CMIP6 Historical configuration indicates that differences in background mean states due to differences in spin-up duration and equilibrium states result in substantial differences in the climate change response of O2. Finally, we discuss gaps and uncertainties in both ocean biogeochemical simulations and observations and explore possible future coordinated ocean biogeochemistry simulations to fill in gaps and unravel the mechanisms controlling the O2 changes.

Studies of microplastic content in water and commercial fish: from scientific research to large-scale monitoring

Purpose. The article presents proposals for the development of studies of microplastic pollution of waters and biological resources in the Russian fishery areas. Materials and methods. The materials of VNIRO on the quantitative assessment of the MPs content in the Arctic Seas in August-October 2019–2022 and modern research on this problem are summarized. MPs samples were collected on the surface of the seas with a Manta-trawl 335 and processed according to a single method. Results. The conducted studies pick up knowledge gaps regarding the real level of marine MPs pollution of the Arctic region.Novelty. No large-scale localization of MPs was detected in the observation areas, the level of plastic pollution on the surface of the Russian Arctic seas was lower compared to other areas of the World Ocean. We point out the relevance of the assumption that a significant part of MPs fragments and fibers are transported by Atlantic and Pacific currents to the Arctic basin. A sample survey of fish in commercial catches for MPs contamination confirmed the presence of its fragments and fibers in the digestive tract of some individuals (pink salmon, greenlings, herring, sea bass) caught in the North Pacific seas in 2019, 2021 and 2022.Practical significance. The global increase in MPs content in the Northern hemisphere seas, exacerbated by climate change, requires a transition from exploratory scientific observations to regular multidisciplinary study of plastic pollution of biotopes of ecosystems of the Arctic, North Pacific and Atlantic seas. The key points and tasks of monitoring microplastic pollution of waters and biological resources in the Russian fishing areas provide for objective and comparable assessments based on the use of unified methods of collection and processing of samples, as well as an ecosystem approach to prevent environmental risks and ensure food safety.

Morphological characteristics, molecular species validation and spatio-temporal distribution of myctophid eggs off the Pacific coast of northeastern Japan

Myctophids in the world's oceans have a huge biomass and act as an important link between secondary producers and upper trophic levels through their extensive diel vertical migrations from the epipelagic to mesopelagic layers. Dominance of myctophid larvae in oceanic ichthyoplankton has been reported from various parts of the major oceans; however, there are few records concerning their eggs. We established species-specific morphological characteristics for identifying myctophid eggs which were then validated by sequence analysis of mitochondrial 12S rRNA and cytochrome b genes using representative subsamples of the morphotypes, and then used the criteria to determine the species composition and spatio-temporal distribution of myctophid eggs. Samples were collected monthly in the epipelagic layer off the Pacific coast of northeastern Japan, resulting in 664 net tows that yielded a total of 10,172 myctophid eggs, defined by a smooth and delicate chorion, segmented yolk, and single oil globule. Subsamples of 160 small, 34 intermediate, and 20 large-sized eggs were sequenced, resulting in their classification as Diaphus theta, Diaphus garmani, and Myctophum asperum, respectively. Mean egg diameter was smallest in D. theta (0.75 mm), intermediate in D. garmani (1.06 mm), and largest in M. asperum (1.31 mm). Eggs of D. theta had a markedly narrower perivitelline space (0.17 mm) than D. garmani and M. asperum (0.49 and 0.71 mm, respectively). Based on morphology, the myctophid eggs were dominated by D. theta (86.0%), followed by D. garmani (12.6%) and M. asperum (1.4%). Abundances of early-stage eggs of D. theta and D. garmani were high during the daytime to dusk but low at night and dawn, indicating that spawning would not be active in the epipelagic layer at night. Spawning can be considered to occur in the mesopelagic layer during the early night, and then the eggs rise to reach the epipelagic layer in the daytime. High abundances of D. theta and D. garmani eggs were observed in the slope region from spring to summer, corresponding with the larval distribution reported for the study area.

Rescue device concept for the ARGO profiling float

Abstract The material presents the development work carried out by the ARGO-Poland scientific consortium related to the design of rescue systems for ARGO profiling floats used for in situ exploration of the world oceans. The article describes the principle of operation of the Argo float and the theoretical basis of the rescue system and six alternative design solutions for such a system.

К СЕМИДЕСЯТИЛЕТИЮ СО ДНЯ РОЖДЕНИЯ Н. А. РИМСКОГО-КОРСАКОВА

August 23, 2023 marked the 70th anniversary of the birth of Nikolai Andreevich RimskyKorsakov. Nikolai Andreevich worked at the Institute of Oceanology for almost half a century and went from an engineer to deputy director for scientific work in the field of Marine Engineering, head of the Bottom Hydrolocation Laboratory, chief researcher, professor, doctor of technical sciences. He is a participant in numerous expeditions to various areas of the World Ocean and inland waters of Russia on ships of various classes and different departmental affiliations. Under his leadership, many different projects, government contracts were completed, numerous technical means were developed and built for the multifaceted study of water areas, the use of which made it possible to obtain a large amount of previously inaccessible data on various underwater objects of natural and artificial origin, including objects posing a radiation threat.

К 75-ЛЕТИЮ СЕРГЕЯ МИХАЙЛОВИЧА ШАПОВАЛОВА

On September 1, 2023, the leading researcher, head of the Scientific Coordination Oceanological Center of the Russian Academy of Sciences Sergey Mikhailovich Shapovalov turns 75 years old. S. M. Shapovalov has been working at the Shirshov Institute of Oceanology of RAS since 1976. For many years he has been engaged in scientific and coordination work, including international organizations. He is the Scientific Secretary of the Scientific Council of the Russian Academy of Sciences on the problems of the World Ocean. From the 1990s until present, S. M. Shapovalov participates in the work of the International Scientific Committee for Oceanographic Research (SCOR). From 2014 to 2018 he was Vice President of the SCOR. S. M. Shapovalov participated in more than 20 long-term scientific marine expeditions.

МОЯ ЖИЗНЬ С ИНСТИТУТОМ

The article is dedicated to the 90th anniversary of Irina Nikolaevna Sukhanova – phytoplanktonologist, biologist, Candidate of Biological Sciences. I. N. Sukhanova, a veteran of Russian oceanology, has worked at the Institute of Oceanology of the Academy of Sciences (IO RAS) since 1958, participated in 18 major marine expeditions of the Institute, dealt with a wide range of problems related to the structure and functioning of phytocenoses in various regions of the World Ocean, as well as the Black, Baltic and Bering Seas. She studied phytoplankton blooms and the life cycles of mass phytoplankton species with the possibility of changing autotrophic and heterotrophic types of nutrition during the development of populations. She is the first phytoplanktonologist to develop and introduce into the practice of marine research a method of soft reverse filtration of samples using nuclear filters. In this article, Irina Nikolaevna recalls her fellow scientists and her teachers, the expeditions in which she had a chance to participate and talks about her work as a phytoplanktonologist.

A simulation study of the Argo program-enhanced global ionospheric modeling

The ionospheric total electron content (TEC) is a critical parameter for space weather and Global Navigation Satellite System (GNSS) applications. Since 1998, the Ionospheric Working Group of the International GNSS Service (IGS) has been generating global ionospheric maps using data from hundreds of GNSS stations. However, the uneven geographical distribution of these observations has resulted in significant variations in TEC map accuracy, particularly in marine areas where observations are scarce or absent. In this study, we introduce Argo data as additional observations to enhance the accuracy of global ionospheric modeling. Argo data consists of measurements collected by more than 1,000 robotic floats deployed across the world's oceans. By utilizing the NeQuick model and considering the geographic coordinates of both IGS stations and Argo buoys, we simulate the ionospheric Slant Total Electron Content (STEC). This approach allows us to examine the impact of integrating Argo data into global ionospheric modeling and evaluate its effectiveness. The results indicate a significant improvement in the overall accuracy of the model after incorporating Argo data. Furthermore, by increasing the model's degree, a better global fit is achieved. It eliminates noticeable overestimation or underestimation of TEC, especially evident at a degree of 30. As the availability and uniform distribution of observations improve, the model demonstrates higher accuracy and enhanced global performance.

Numerical study of the gas production process from a gas hydrate deposit in the presence of thermal and depression effects

Today the issue of gas production technology from existing gas hydrate deposits discovered on the shelf of the World Ocean and in permafrost areas is still very significant since the methane reserves in the free state are significantly inferior to its reserves in the form of its gas hydrates. One of the tasks for possible gas production from a hydrate-containing porous medium is to study the process of gas hydrate decomposition under thermal and depression effects since they are most commonly used ones. It is necessary to conduct a theoretical study including the development of a mathematical mode and its algorithmization, the creation of a computational program and the conduct of numerical experiments. The paper presents one-dimensional axisymmetric problem of heating and/or pressure reduction at the bottom of a well passing through the entire thickness of a porous formation when its pores are initially filled with methane and its hydrate. The utilized mathematical model includes the continuity equations for methane, its hydrate and water; the equation of the gas phase motion in a porous medium as the Darcy filtration law; the state equation of methane and water, the energy conservation equation considering the Joule–Thomson effects and adiabatic cooling for gas, the latent heat of the “gas hydrate  methane + water” phase transition. A numerical implementation of the proposed mathematical model and a numerical study of the thermal and/or depression impact on the studied hydrate-bearing deposit are carried out. The results of calculations show that the size of a zone containing only the gas hydrate decomposition products (gas and water) slightly increases with a smaller length of a porous layer. They also show that the thermal effect (increasing the temperature at the bottomhole of production well) on the hydrate-saturated reservoir simultaneously with the depression effect is not efficient enough due to the intensive flow of cold gas (with a temperature equal to the initial temperature of the reservoir) from the hydrate-containing deposit to the well.

Reliability assessment of the ocean thermal energy conversion systems through Monte Carlo simulation considering outside temperature variation

AbstractThe ocean thermal energy conversion (OTEC) systems, as renewable energy-based power plants, have the potential to play a significant role in meeting future electricity demands due to the vast expanse of the world's oceans. These systems employ the temperature difference between surface ocean waters and deep ocean waters to drive a thermodynamic cycle and produce electricity. The temperature of deep ocean waters, approximately 1000 m below the surface, is approximately 4 °C, while surface ocean temperatures typically range between 20 and 30 °C. The generated power of OTEC systems is dependent on these temperature differences and may vary with changes in surface ocean temperatures. In this study, the main focus is to find the impact of temperature variation on the failure rates of OTEC system components and the generated power output of these plants. The findings indicate that as the demand for the power system increases, its reliability decreases. In order to improve the reliability of the power system, the integration of a new generation unit, such as the close cycle OTEC power plant under investigation, could be necessary. The findings also indicate the importance of considering temperature variation in the evaluation of the reliability of such types of power plants based on renewable energy.