Coastal Water Areas Research Articles

Distribution and Genesis of Aliphatic Hydrocarbons in Bottom Sediments of Coastal Water Areas of the Crimea (the Black and Azov Seas)

The aim of the article is to assess the level of aliphatic hydrocarbon (AHC) contamination in bottom sediments of the Azov–Black Sea coast of the Crimea, as well as to identify potential sources of its formation. Bottom sediment samples obtained from 19 stations during the research cruise of the R/V “Professor Vodyanitsky” (June 2020) were used as the material for this investigation. Sampling stations were located along the coast of the Crimean Peninsula and the Caucasus coastlines (the Black and Azov Seas). N-hexane extracts of sediments were studied by gas chromatography to determine the AHC amount and composition. It was established that AHC concentrations in the study area varied from 1.30 to 127.8 mg/100 g. Generally, bottom sediments of the Black and Azov Seas were characterized by low AHC contents, while increased AHC contents were found in the outer harbor of Sevastopol and Yalta regions. To identify potential hydrocarbon sources, various hydrocarbon markers were used. In most of the study areas, n-alkane composition was determined by similar sources of inputs and organic compound transformation. At the same time, oil pollution linked with use of fuel was recorded almost everywhere.

An unusual winter bloom of dinoflagellates with notable damage to kelp cultivation around Shandong peninsula, China

In the coastal waters around Shandong peninsula, an unprecedented winter bloom of dinoflagellates Gonyaulax polygramma and Akashiwo sanguinea occurred in 2021 from late November to early December. The bloom affected a wide area of coastal waters extending from west to east along the northern Shandong peninsula and had a devastating blow to the kelp cultivation industry. Based on the remote-sensing data, the initiation of the bloom was traced back to the region adjacent to the mouth of the Yellow River in Laizhou Bay, where enhanced freshwater discharge from the Yellow River was recorded from September to November. It's proposed that the increased precipitation in the Yellow River basin associated with northward extension of the precipitation band in China could be an important reason for this winter bloom. This unusual winter bloom around Shandong peninsula highlights the potential risks of harmful algal blooms and their impacts on coastal ecosystems under the background of climate change.

Bycatch and discard rates assessment of the gillnet fishery in the southern Brazil

The fisheries discard patterns are an important element to be considered in stock assessment, fisheries management, and conservation measures. Using data collected by scientific observers on board, we analysed the bycatch and discard rates of the pelagic and bottom gillnet fishing in southern Brazil. Bottom gillnet was responsible for discarding from 77 taxa; 35 % of the discarded biomass was composed of teleost fishes, 33 % of elasmobranchs, and 22 % of other taxa. Pelagic gillnet, targeting the Pomatomus saltatrix, resulted in the discard of 13 species and taxa not identified at the species level, such as Cnidaria and Malacostraca. The most discarded fish species was Brevoortia pectinata, constituting 94.8 % of the total discarded biomass. The discard rate of bottom gillnets targeting Micropogonias furnieri was higher (20 %) than that of those targeting the demersal species (6 %), such as Cynoscion guatucupa (formely Cynoscion striatus) and Umbrina canosai. The high biomass proportion and numerous discarded species emphasize the need for effective management through temporal and spatial fishing restrictions. Our findings suggest potential measures, including the closure of fishing areas in coastal waters.

Grain-size distribution characteristics of sediments in coastal shallow waters from Van Don to Tien Yen - Ha Coi, Northwest Gulf of Tonkin, Vietnam, according to End-member modelling analysis

The study involved the collection of eighteen surface sediment samples from the coastal shallow water area from Van Don to Tien Yen - Ha Coi in the Northwestern section of the Gulf of Tonkin to analyze their particle size composition. Utilizing the EMMAgeo end-member analysis model, four characteristic particle sizes (4EM) of 0.34, 7.7, 130, and 230 µm, corresponding to clay, fine silt, and fine sand of varying sizes were identified. In conjunction with the sedimentary environment, the spatial distribution analysis of these end members allowed a detailed determination of the formation conditions and distribution of the sediment components. Clay deposits (EM1) are primarily intercalated between the islands. At the same time, fine silt (EM2) is concentrated in the northern part of the study area, transported by flows, and deposited in a low-energy environment. Fine sand sediments (EM3 and EM4) are distributed along the coast of the Van Don peninsula in the Southern part of the study area and likely formed in association with tidal-wave processes under higher energy conditions compared to the North.

Determination of occurrence of atmospheric blockings over the Caspian Sea region in winters of 1959–2022, and influence of them on the ice regime of the Northern Caspian Sea

The ice regime of the Caspian Sea has pronounced influence on the heat and moisture exchange of the reservoir with the atmosphere, the state of the ecosystem, as well as human marine activities, including shipping, fishing, construction of hydraulic structures, etc. Consequently, the development of existing ideas about the causes of changes in the characteristics of the ice regime of such water bodies is actual and socially significant problem of limnology, hydrometeorology, ecology, and navigation. This study was aimed at determination the frequency of occurrence of atmospheric blockings over the Caspian region with standings longer 5 days in winter period of 1959–2022, and investigation of influence of them on the ice regime in the Northern area of the Sea. The following information and data were used: changes in hourly mean values of atmospheric pressure at the sea level, geopotential of isobaric surfaces 850, 500 and 300 hPa, presented in the ERA5 reanalysis; and observational data on air temperature and ice cover from hydrometeorological stations located in the Caspian region of Kazakhstan and Russia. It has been established that in the winter during a long standing of atmospheric blockings the mean daily air temperatures noticeably drop. The values of all the studied characteristics of every atmospheric blocking which occurred in 1959–2022 were estimated as well the influence of them on the ice regime in the North of the Caspian Sea was analyzed. The relationship between a decrease in the frequency of atmospheric blockings (AB), sums of negative air temperatures on its coasts, and the ice cover thickness in the corresponding areas of coastal waters has been revealed in the region. The longer the total AB duration, the lower is the air temperature, and the ice thickness in February is larger.

Tsunami Waves off the Southeastern Coast of Sakhalin Island Caused by the Eruption of the Hunga–Tonga–Hunga–Ha’apai Volcano on 15 January 2022 According to Observations by Bottom Devices of Waves

The observation of waves (sea level oscillations) in the coastal water area of the southeastern coast of Sakhalin Island was carried out from November 2021 to May 2022 using bottom-mounted high-precision ARW 14 K devices with one second discreteness. The analysis of the obtained time series revealed the presence of anomalous waves in the range of tsunami waves in January 2022. It is shown that the waves detected on 15 January 2022 with periods of 15 minutes–4 hours, significantly standing out above the background, are associated with volcanic tsunami waves. Spectral analysis of the time series showed that the maximum in the spectra of sea level oscillations found after the volcanic eruption is close to the period of the first mode of the shelf seiche. This indicates that incoming tsunami waves excite shelf seiches in the coastal zone and contribute to the generation of longshore and transverse seiches into Mordvinov Bay. Time series analysis made it possible to establish that the spectral density of sea level oscillations for the time interval of the beginning of the eruption of the Hunga–Tonga–Hunga–Ha’apai volcano from 21 December 2021 to 11 January 2022 significantly differs from the spectral density for the time of the Plinian volcanic eruption. An analysis of the statistical characteristics of sea level oscillations performed on two–day series in the range of periods 1 min–4 h for background waves and tsunamis showed an increase in the rms by 3.5 times for a time series containing tsunami waves. It has been established that for background time series containing tsunami waves, the coefficients of asymmetry and kurtosis differ little from“Gaussia” values. This indicates that the arrival of tsunami waves from distant sources does not significantly disrupt the stationarity of the wave field in the observation area.

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.

Choosing the profile of an inclined – directional well in the Caspian Sea area of Turkmenistan

This paper aims to design a profile for a directional and production-appraisal well, specifically Well No. 707 in the West Cheleken field, situated in the Caspian Sea coastal water area. In the context of rapid changes in the energy sector, this study holds significance, offering economic benefits and contributing significantly to the energy security of the region and the global energy market. The main objective of this study is to optimise directional drilling for exploration wells in the Caspian Sea area of Turkmenistan, specifically focusing on improving efficiency and reducing environmental impact. To achieve this research objective, the author proposes designing a profile for a directional and production-appraisal well, utilising materials from geophysical surveys of previously drilled wells. This approach aims to avoid accidents and complications during the drilling process. Both the Close Approach software and safety regulations in the oil and gas production industry are employed to prevent collisions of wellbores. In conclusion, this research contributes innovative solutions to optimise directional drilling processes for exploration wells. It addresses potential complications in open wells and, importantly, mitigates the risk of wellbore collisions. Keywords: wellbore collision; complication; stabilization; accident; Apsheron; Akchagil; curvature; displacement.

COASTAL TERRITORY AND COASTAL ZONE: DEFINITION, CHARACTERISTICS, URBAN DEVELOPMENT

The purpose of this publication is to define the terms «coastal territory» and «coastal zone» from the point of view of their urban planning use, because the current legislative documents, normative sources, scientific articles, which raise the problems of development and preservation of coastal territories, do not give their clear interpretation. As a natural phenomenon, the river and its coastal territory are an interdependent river ecosystem, which is a complex dynamic complex with paradynamic connections, where the exchange of substances, energy, and information takes place. The general boundary and configuration of the coastal territory is determined according to the maximum value of the influence of the river, taking into account its engineering and geological, microclimatic and spatial planning criteria. From the point of view of urban planning, the coastal area is a natural reserve of the urban fabric, which has a favorable potential for the formation of coastal zones in order to create a comfortable and safe urban environment. The coastal zone is a part of the coastal territory and water area with regulated and unregulated economic activity, the functional purpose of which is the organization of a favorable environment for the life of the population in the zone of influence of the reservoir. Almost all coastal areas are favorable for urban development - the difference exists in the degree of complexity and cost of urban development of coastal areas, their transformation into coastal zones. The urban planning assessment of the coastal zone for the organization of a favorable and comfortable environment for people's stay here is a complex of engineering-geological, architectural-compositional, sanitary-ecological and economic assessments. The choice of techniques for the development of the coastal zone should be based on the principles of the formation of an expressive architectural and planning development, improvement of the urban microclimate, the formation of convenient public space and landscaped and recreational areas. It is unacceptable to build up the coastal zone with capital structures of the industrial area, with the exception of water management facilities, and the laying of transit main streets here. The functional purpose of coastal zones may change over time. An assessment of the natural factors of coastal areas in relation to the degree of favorability of urban development of coastal areas and an assessment of coastal landscapes in relation to their functional purpose is given. It is noted that the main defining features of the coastal area, among many factors, are the geomorphological structure and microclimate. The transformation of Kyiv's Dnieper embankment has been traced: starting from the 5th century, after passing through 4 main periods of formation due to the arrangement and beautification of the coastal zone, the Podil embankment today has lost its function as a public space. The transformation of the coastal zone of Kyiv into a center of limited elite housing and a transport corridor is an impoverishment of the life of the city, the loss of an important urban area. The development of coastal areas, as a natural potential in cities, should be carried out within the limits of current legislation and taking into account environmental norms to create a favorable urban environment.

A RELATIONSHIP BETWEEN CHLOROPHYLL AND DISSOLVED SUBSTANCES IN COASTAL WATERS OF SOUTH BALTIC SEA – ANTHROPOGENIC AND NATURAL INFLUENCES

The objectives of this study were to indicate the relationship between chlorophyll levels, dissolved metal group minerals and phosphates in the studied area of the Central Polish Coastal Waters and to relate these data to the influence of the terrestrial environment. In 2020, in the Central Polish Coastal Waters (PLB990002), which is a special area for the protection of birds, tests were carried out on the concentrations of chlorophyll, phosphates, dissolved microelements: zinc, cobalt, nickel and iron, and electrolytic conductivity. For the analysis of dissolved microelements, a graphite cuvette version of atomic absorption spectrophotometer (AAS-GF) was used. Chlorophyll and phosphates were studied using UV-VIS spectrophotometer. The concentrations obtained in coastal sea water in the spring after the wintering of waterfowl and in the autumn were compared. Microelement and phosphate concentrations were higher in spring than in autumn. The relationship between the level of chlorophyll and phosphates and the tested microelements in coastal waters was demonstrated, and the results were linked to the possible sources of these chemical substances, such as wintering of birds, tourism, municipal and port management. It was also observed that the upwelling effects occurred in the study area, which significantly influenced changes in the chemical composition of sea water.

Hazard Zoning of Harmful Algal Bloom Disasters in Zhejiang Coastal Waters Using GIS: 1933-2021

The coastal waters of Zhejiang Province in China experience a high incidence of harmful algal blooms (HABs). It is therefore important to carry out hazard zoning to prevent and mitigate these HAB disasters. According to the historical record data of HAB disasters from 1933 to 2021, the frequency, duration, area and algal toxicity of HAB occurrences can be used as evaluation indicators. A method for hazard zoning of HAB disasters and a method for verifying the rationality of the zoning results are proposed. The hazard zoning results of HAB disasters in the coastal waters of Zhejiang from 1933 to 2021 (H1933-2021) show that very-high hazard degree areas of coastal waters of Zhejiang Province were found in Shengshan waters, the eastern waters of Zhujiajian and Nanji Islands' waters. Due to the influence of marine environmental factors, the spatial distribution of hazard degree of HAB disasters is dynamic, so it is recommended that the hazard zoning of HAB disasters be carried out once every five years. The rationality of the zoning results from 2017 to 2021 is verified, showing that the hazard zoning method of HAB disasters proposed in this study has a good rationality and credibility. This study utilized a qualitative approach to visually identify the spatial distribution of hazard degree zoning of HAB disasters in the Zhejiang Province coastal waters over the last 88 years. This has provided useful information to help prevent and mitigate HAB disasters and guide mariculture and coastal tourism planning.

Distribusi Spasial Lamun di Perairan Sekotong Barat-TWP Gita Nada Lombok Barat Menggunakan Citra Landsat 8 OLI

West Sekotong Village is one of the coastal water areas included in the Gita Nada Aquatic Tourism Park (TWP) area which has a seagrass habitat. Seagrass beds in West Sekotong are threatened due to increased tourism and community activities. This research aims to determine the distribution and extent of seagrass beds on the coast of West Sekotong-TWP Gita Nada. This research uses a remote sensing approach through interpretation of Landsat 8 OLI imagery. This research consists of 2 steps, namely image data processing and supporting data. Image data processing includes several stages, namely image data collection, geometric correction, radiometric correction, image cutting, image composite, image data sharpening, image data interpretation, accuracy testing, area measurement, and final layout. Supporting data was obtained by searching related literature, interviews and surveys of activities that have the potential to have an impact on seagrass ecosystems. The research results show that the distribution of seagrass in West Sekotong-TWP Gita Nada covers the coast of the large island (mainland) and the coast of small islands. The distribution of seagrass on the mainland is found on the coasts of Medang, Tanjung Kelor, Batu Kijuk, Tawun, Labu, Kelapa, Pandanan, Gili Genting, Labuan Petung, Temeran, and Gawah Pudak. In the coastal areas of small islands, seagrass is found on Gili Sudak, Gili Tangkong, Gili Nanggu, Gili Poh, and Gili Lontar. The total area of seagrass beds in West Sekotong is around 144.68 ha. On the mainland coast the area is 118.96 ha (82.2%) and on small islands the area is around 25.72 ha (17.8%). The distribution of seagrass in West Sekotong is influenced by many factors, among which those observed in this research are the type of substrate, the presence of river estuaries, and the use of land and coastal waters.

Ethological and Acoustic Studies of Bottlenose Dolphins (Tursiops truncatus ponticus Barabash, 1940) in the Coastal Water Area of the Karadagh Reserve, South-Eastern Crimea

The work is devoted to the study of the bottlenose dolphin community in the coastal waters of the Karadag Reserve (southeastern Crimea). Observations and acoustic recordings were carried out in 2015–2017 and in 2020–2022 As the main method for identifying bottlenose dolphins, we used the method developed by us for acoustic recording of bottlenose dolphins by individual sound signals “signature whistles”. This method of identification makes it possible to fairly accurately count the population, observe the movements of bottlenose dolphins, and also reveal the association of individuals with each other.

Deep Electrical Conductivity Anomalies in the Chaun Bay Region Based on Magnetic Variation Sounding Data

Abstract—This paper discusses the results of magnetic variation soundings at two sites in the eastern Arctic, in the Chaun Bay region, at the Pevek and Valkarkai weather stations, by using the ModEM program to perform a three–dimensional (3D) inversion of tippers. The inversion has produced a geoelectric model of the region in a subsurface area of 300 × 300 × 200 km. The moduli of tippers at both sites have values between 0.2 and 0.85, reaching the maximum ones in a period of 1000 s. At the Pevek weather station, the real induction arrow in the Parkinson convention is oriented to the west throughout the range of periods. At the second site, its azimuth changes from 30° to the NE to –30° to the NW as the period of variations increases. Throughout the range of depths, conductive inhomogeneities are located to the west and north of the Chaun folded zone. They extend as a narrow strip under the western and northern coastal parts of the zone at depths of 8–12 km. As the depth increases, they are split into blocks, which reach their maximum size in the horizontal plane at depths ranging between 20 and 30 km. The most prominent among them is the conductive block beneath the southern part of the Chaun Bay. The roots of these blocks are distinguishable at depths of up to 100 km. The Chaun folded zone is represented by a high–resistance block down to a depth of 150 km with an electrical resistivity of more than 1000 Ω⋅m. Comparison of the obtained geoelectric model with the geophysical studies previously conducted here reveals a correlation between the location of conductive formations and the location of weakly positive anomalies in the gravity field in the Bouguer and isostatic reductions in the coastal water area.

Biological Features of Atlantic Cod <i>Gadus Morhua</i> L., 1758 (Gadiformes: Gadidae) of the Murmansk Coast: Race Composition and Fishing

The biological features of Atlantic cod in the coastal zones of the Murman for 1999–2006 were studied. The age composition, growth rate and maturation, feeding habits and structure of otoliths were analyzed. Histological and genetic studies were carried out. It was shown that young cod mainly lives and spawns in Western Murman bays. Older cod leaves the bays due to insufficient food supply. The growth rate of young coastal cod is comparable to that of cod in the open part of the Barents Sea. With age, the cod of open sea areas noticeably overtakes the cod that lives in the coastal zone in growth. It was noted that cod spawns in the bays with both coastal and Atlantic types of otoliths. Studies of genetic polymorphism indicate a high degree of genetic si-milarity between cod groups in the Norwegian and Barents Seas, which is evidenced under the influence of currents (branches of the Norwegian Atlantic Current, the Murmansk Coastal Current) and against the background of migrations at different stages of ontogeny of cod individuals from coastal and open water areas.

A model of a shear landslide wedge with subsequent hydraulic rupture as an explanation for the formation of an anomalous section of the Bazhenov formation in the north of Western Siberia. Part 2. Description of the mesostructural complexes in the core and the model of the anomalous section formation

A new anomalous section of the Bazhenov formation was described on the territory of the Urengoydeposit in the northern part of Western Siberia. This article presents descriptions of mesostructural complexes in the core, on the basis of which a new model for the formation of the anomalous section of the Bazhenov formation was proposed. It was found that the formation of the mesostructural complexes occurred at different stages of the landslide and when its body moved along the uneven surface of the detachment. In the formation of large injection “sand veins” in the studied section, the main role was probably played by the landslide-induced grain flow from the coastal shallow water area. The penetration of its sandy material into the rocks of the Bazhenov formation and, to a lesser extent, the Achimov formation occurred due to the energy of hydraulic shock and hydraulic fracturing along layer-by-layer and secant fractures.

Effect of cage culture on sedimentary heavy metal and water nutrient pollution: Case study in Sansha Bay, China

The aquaculture area in China's coastal waters has increased rapidly from 6000 km2 in 1990 to 22,000 km2 in 2020. Despite extensive research regarding the effect of coastal aquaculture on water and sediment pollution, evaluating the quantitative relationship between aquaculture and pollutants remains challenging. Sansha Bay, the world's largest cage aquaculture base for Pseudosciaena crocea, is a typical enclosed bay used for investigating aquaculture pollution. A cage culture database is established from 2000 to 2020 in Sansha Bay. Meanwhile, 236 sediment samples from 3 sediment cores and 67 water samples from 4 transects are obtained from the bay for experiments. The main indicators are five nutrients (NO3−, SiO32−, PO43−, NH4+, and NO2−) in the water samples, the grain size, the heavy metal (Zn, Cu, Pb, Cr, Cd, and As) content, and the 210Pb radioactivity in sediment samples. Based on data obtained and a new calculation method, the annual increment in Zn, Cu, As, Cd, Pb, and Cr contents in the cultured zone is shown to increase by 2137 %, 1881 %, 506 %, 300 %, 202 %, and 118 % in 2000–2018, respectively, as compared with the levels in a noncultured zone. The activities of the cage culture increased NO3− by 9 %, PO43− by 30 %, NH4+ by 115 %, and NO2− by 232 %, compared with natural conservative mixing processes, such as the mixing of SiO32−, in 2020. A novel quantitative approach with broad applicability is proposed to evaluate the magnitude of anthropogenically induced environmental contamination. The effectiveness of the proposed technique is demonstrated through a case study conducted in Sansha Bay, China.

STAGES OF BARRIERS FORMATION IN THE ENTRANCE GATES OF THE VOLGOGRAD RESERVOIR BAYS

The secondary processes of alongshore transport and accumulation of sediments are the consequences of reshaping the shores of the Volgograd Reservoir. Alongshore sediment transfer promoted the segregation of bays from the main water area of the Volgograd Reservoir with abrasion-accumulative barriers. Classification of the bays according to the degree of evolution of abrasion-accumulative barriers in their entrance gates is the initial stage of complex research which is necessary to reveal the main patterns of the separation process. Application of the Earth remote sensing data and geoinformation technologies is the most effective to study the process in addition to field methods. The study is based on the satellite imagery of Google Earth program and data of field research of the bays in 2008, 2010-2016 and 2019-2020. Both analytical (cartographic, graphical, mathematical methods and methods of working with satellite images) and field (geometric leveling of abrasion-accumulative barriers and spits, and bathymetric survey of bays) research methods were applied. Morphometric parameters of the entrance gates to the bays of right and left coast of the Volgograd Reservoir were measured using the satellite images of Google Earth. Expedition materials and data received from satellite images were then compared. The difference in absolute values does not exceed double standard error. This indicates the reliability of applied research method. We calculated two coefficients for classification of bays. These coefficients considered width of the bay at the entrance gate, width of the coastal shallow water area at the entrance gate and length of above-water part of a sand bar or spit. Six classes of bays were identified according to the degree of evolution of abrasion-accumulative barriers at the entrance gates: opened bays (class 1), bays at the initial stage of segregation (2), bays at the active stage of segregation (3), bays at the final stage of segregation (4), closed bays, (5) and a specific class - bays with the entrance gates subjected to anthropogenic impact (6). The bay segregation becomes more active with the expansion of the coastal shallow water area at its entrance gate. Quick overgrowth by higher aquatic, herbaceous and tree-shrub vegetation takes place under the active formation of abrasion-accumulative barriers.

Erratum: Eyestalk Ablation to Increase Ovarian Maturation in Mud Crabs.

Erratum: Eyestalk Ablation to Increase Ovarian Maturation in Mud Crabs.

Measurement report: Summertime fluorescence characteristics of atmospheric water-soluble organic carbon in the marine boundary layer of the western Arctic Ocean

Abstract. Accelerated warming and a decline in sea ice coverage in the summertime Arctic Ocean can significantly affect the emissions of marine organic aerosols and biogenic volatile organic compounds. However, how these changes affect the characteristics of atmospheric water-soluble organic carbon (WSOC), which plays an important role in the climate system, remains unclear. Thus, to improve our understanding of WSOC characteristics in the rapidly changing Arctic Ocean, including its summertime fluorescence characteristics, we simultaneously measured atmospheric concentrations of ionic species and WSOC, a fluorescence excitation–emission matrix coupled with parallel factor (EEM-PARAFAC) analysis of WSOC, and marine biological parameters in surface seawaters of the western Arctic Ocean during the summer of 2016. WSOC was predominantly present as fine-mode aerosols (diameter <2.5 µm, median =92 %), with the mean concentration being higher in the coastal water areas (462±130 ngC m−3) than in the sea-ice-covered areas (242±88.4 ngC m−3). Moreover, the WSOC in the fine-mode aerosols was positively correlated with the methanesulfonic acid in the fine-mode aerosol samples collected over the sea-ice-covered areas (r=0.88, p<0.01, n=10), suggesting high rates of sea–air gas exchange and emissions of aerosol precursor gases due to sea ice retreat and increasingly available solar radiation during the Arctic summer. Two fluorescent components, humic-like C1 and protein-like C2, were identified by the PARAFAC modeling of fine-mode atmospheric WSOC. The two components varied regionally between coastal and sea-ice-covered areas, with low and high fluorescence intensities observed over the coastal areas and the sea-ice-covered areas, respectively. Further, the humification index of WSOC was correlated with the fluorescence intensity ratio of the humic-like C1 / protein-like C2 (r=0.89, p<0.01) and the WSOC concentration in the fine-mode aerosols (r=0.66, p<0.05), with the highest values observed in the coastal areas. Additionally, the WSOC concentration in the fine-mode aerosols was positively correlated with the fluorescence intensity ratio of the humic-like C1 / protein-like C2 (r = 0.77, p<0.01) but was negatively correlated with the biological index (r=-0.69, p<0.01). Overall, these results suggested that the WSOC in the fine-mode aerosols in the coastal areas showed a higher degree of polycondensation and higher aromaticity compared to that in the sea-ice-covered areas, where WSOC in the fine-mode aerosols was associated with relatively new, less oxygenated, and biologically derived secondary organic components. These findings can improve our understanding of the chemical and biological linkages of WSOC at the ocean–sea-ice–atmosphere interface.