Western Coastal Waters Research Articles

Diversity of the dinoflagellate genus <i>Tripos</i> Bory 1823 (Dinophyceae) in the Western coastal waters of Tonkin Gulf, Vietnam

Tripos is a genus of marine dinoflagellates in the family Ceratiaceae, the order Gonyaulacales (Dinophyceae). The genus Tripos has been studied in the western coastal waters of Tonkin Gulf, including 6 coastal sampling stations (Tra Co, Cua Luc, Do Son, Ba Lat, Sam Son, Cua Lo) and 2 offshore stations (Co To, Bach Long Vi) in four surveys conducted in March, June, August and November 2022. A total of 21 species belonging to the genus Tripos were initially identified in the study area. The number of species of this genus is lower in the estuarine area and higher in the offshore. The species occurred at all sampling stations, including Tripos furca, T. fusus, T. muelleri, T. trichoceros and T. breve, in which T. furca and T. fusus were the most common species. Species were common including Tripos candelabrus, T. ehrenbergii, T. gravidus, T. minutus, T. extensus and T. longipes. The species diversity in the dry season (March and November) was higher than in the rainy season (June and August). Cell density of the Tripos species varies spatially and temporally in the study area. The variation in Tripos density was related to the sampling stations, tide, sampling time, and water environment factors such as temperature, salinity, DO and pH.

Grazing impact of the calanoid copepods Acartia spp. on the toxic dinoflagellate Alexandrium pseudogonyaulax in the western coastal waters of Korea.

Marine dinoflagellate species in the genus Alexandrium are well known to produce paralytic shellfish poison as well as common coastal species with cosmopolitan distribution. However, few studies on the feeding of copepods on Alexandrium species have been conducted. The toxic dinoflagellate Alexandrium pseudogonyaulax contains goniodomin A and causes red tides in many countries. To investigate the relationship between the toxic dinoflagellate A. pseudogonyaulax and the calanoid copepods Acartia spp., we quantified the ingestion rates of Acartia spp. feeding on A. pseudogonyaulax as a function of prey concentration. Additionally, we estimated grazing coefficients by integrating data from field observations of Acartia spp. and coexisting A. pseudogonyaulax with laboratory measurements of ingestion rates obtained during this investigation. Furthermore, we compared the ingestion rates of Acartia spp. and other predators feeding on Alexandrium species as previously reported. The ingestion rates of Acartia spp. on A. pseudogonyaulax increased continuously with increasing mean prey concentration. The highest values among the ingestion rate of Acartia spp. feeding on A. pseudogonyaulax was 3,407 cells predator-1 d-1 (4,872 ng C predator-1 d-1) at the given prey concentration. The calculated grazing coefficients for Acartia spp. on A. pseudogonyaulax in Shiwha Bay, Korea, were up to 0.073 d-1. The results of this study suggest that A. pseudogonyaulax may decrease or maintain the population of Acartia spp. in marine food webs.

Spatial distribution models and biodiversity of phytoplankton cysts in the Black Sea

The current study employed diverse statistical and machine learning techniques to investigate the biodiversity and spatial distribution of phytoplankton cysts in the Black Sea. The MaxEnt distribution modeling technique was used to forecast the habitat suitability for the cysts of three potentially toxic microalgal taxa (Lingulodinium polyedra, Polykrikos hartmannii, and Alexandrium spp.). The key variables controlling the habitat suitability of Alexandrium spp. and L. polyedra were nitrates and temperature, while for the P. hartmannii cysts, nitrates and salinity. The region with the highest likelihood of L. polyedra cyst occurrence appears to be in the western coastal and shelf waters, which coincides with the areas where L. polyedra red tides have been documented. The projected habitat suitability of the examined species partially overlapped, perhaps as a result of their cohabitation within the phytoplankton community and shared preferences for specific environmental conditions, demonstrating similar survival strategies. The north-western region of the Black Sea was found to be the most suitable environment for the studied potentially toxic species, presumably posing a greater risk for the onset of blooming events. Two distinct aspects of cysts’ ecology and settlement were observed: the dispersal of cysts concerns their movement within the water column from one place to another prior to settling, while habitat suitability pertains to the particular environment required for their survival, growth, and germination. Therefore, it is crucial to validate the model in order to accurately determine a suitable habitat as well as understand the transportation patterns linked to the particular hydrodynamic properties of the water column and the distinct features of the local environment.

A 2 °C difference affecting the spatiotemporal distribution of small demersal fish assemblages in shallow tropical and subtropical waters of Western Taiwan

Two OR3 research vessel cruises were conducted at seven nearshore sites from north to south in the western coastal waters off Taiwan in May (late spring) and November (late autumn) 2019 in order to gain insights into the 2 °C difference in the tropical-subtropical fish fauna. Totally, 37 families, 72 genera, and 99 taxas were recorded for the 1809 fishes. Three fish assemblages, the North, South, and Fall-Zhuoshui River (ZRf) groups, were identified as eurythermal, stenothermal, and croaker communities. Their dominants, in rank order, were Tarphops oligolepis, Liachirus melanospilosa, Ostorhinchus fasciatus, and Trachinocephalus myops for the Northern eurythermal group, Arnoglossus tenuis, Eubleekeria splendens, and Ostorhinchus pleuron for the Southern stenothermal group, and Johnius taiwanensis, Chrysochir aureus, and Pennahia macrocephalus for the croaker-ZRf group. Their distribution was markedly correlated with the bottom water temperature, seafloor grain size, and concentration of suspended solids. The influence of a 2 °C difference on the tropical and subtropical demersal fish could indicate how rising temperatures due to climate change are shaping fish communities. The flatfish, Liachirus melanospilos, was distributed northward by 0.5oN and is suggested to be considered as an ecological indicator of the tropicalization of subtropical marine ecosystems in the future.

A comparative eco toxicological study of heavy metal concentrations in mussels collected in 2004 from the western and eastern coastal waters in the straits of Johore

The concentrations of Cu, Cd, Zn, Pb, Ni and Fe in the different soft tissues of Perna viridis from the west and east coast of The Straits of Johore (SOJ) were determined. Crystalline style (CS) recorded higher accumulation of Cu (west: 58.2 mg/kg dry weight; east: 56.0 mg/kg dry weight), Cd (west: 9.45 mg/kg dry weight; east: 3.93 mg/kg dry weight), Pb (west: 49.5 mg/kg dry weight; east: 7.07 mg/kg dry weight) and Ni (west: 40.0 mg/kg dry weight; east: 20.2 mg/kg dry weight) than those other soft tissues. Byssus meanwhile recorded high levels of Zn (west: 173 mg/kg dry weight; east: 193 mg/kg dry weight) and Fe (west: 3213 mg/kg dry weight; east: 1221 mg/kg dry weight). By comparing the accumulation of heavy metal concentrations in all the eight tissues, CS and byssus recorded the highest accumulation of heavy metals among all tissues, followed by other tissues namely foot, gill, gonad, mantel, muscle and remainder, which recorded relatively low level on heavy metal concentrations. Generally, the soft tissues recorded higher heavy metal concentrations on the east coast than on the west coast of the SOJ. This indicated a high bioavailability and contamination of the potentially toxic heavy metals on the east coast which was due to various human activities.

Predicted increased distribution of non-native red drum in China’s coastal waters under climate change

Climate change and species invasions are among the most serious threats to global biodiversity, and climate change will further greatly alter the distribution of invasive species. The red drum Sciaenops ocellatus (Linnaeus, 1766) has established non-native populations in many parts of the world, leading to negative effects on local ecosystems. In this study, based on 455 global occurrence records (38 of which were in Chinese waters) and 5 biologically relevant variables (average ocean bottom temperature, ocean bottom average salinity, ocean bottom average flow rate, depth, and distance from shore), a weighted ensemble model was developed to predict the current potential distribution of red drum in Chinese waters and the future distribution under two climate change scenarios (RCP 26 and RCP 85). Based on the True Skill Statistics (TSS) and the Area Under Curve (AUC), the ensemble model showed more accurate predictive performance than any single model. Among the five environmental variables, the average temperature was the most important environmental variable influencing the distribution of red drum. Ensemble model prediction showed that the current suitable habitat of red drum was mainly concentrated on the coast of Chinese mainland, around Hainan Island, and the western coastal waters of Taiwan Province (17~41°N). Projections in the 2050s and 2100s suggested that red drum would expand northwards under both future climate scenarios (RCP 26 and RCP 85), especially in the western part of the Yellow Sea and along the Bohai Sea coast, which should be involved in the management strategies to maintain ecosystem structure and function.

Preliminary study on surface phytoplankton assemblages and physicochemical parameters, off the west and south-west coasts of Sri Lanka

This study evaluates the phytoplankton community structure in relation to physicochemical properties in the western and southwestern coastal waters of Sri Lanka. Phytoplankton and water samples were collected from March to April, 2017 at three transect lines towards offshore in Colombo, Beruwala, and Mirissa, each containing 10 sampling sites. The distance between sampling stations on each transect line was approximately 2 km. Phytoplankton samples were collected towing a net (10 µm mesh) by vertical hauls from known depth (2.5 m) and preserved in Lugol’s solution. The phytoplankton were identified to the lowest possible taxonomic level and counted under the Sedgwick rafter cell using a light microscope. Water samples were collected at 0.5 m depth using the Ruttner Sampler and analysed for chlorophyll-a, nutrients, and total suspended solids (TSS). This study identified 57 phytoplankton species comprised of diatoms (33 species), dinoflagellates (23 species), and cyanobacteria (1 species). In general, phytoplankton abundance and species diversity decreased towards offshore in the three transects. Total phytoplankton and diatom abundances varied significantly among the three transect lines, and significantly higher abundance was reported at Mirissa and Colombo than at Beruwala (One-way ANOVA; p < 0.05). Total phytoplankton abundance significantly correlated with dinoflagellates, toxic species of dinoflagellates, chlorophyll-a, and nitrate-N (p < 0.01). Ten toxic species of dinoflagellates were reported in the study. Diatoms dominated (60%) in the study area, followed by cyanobacteria (31%) and dinoflagellates (9%). Diatoms of Cerataulina sp. (31%) and Navicula sp. (50%) were dominant in Colombo and Mirissa respectively, while cyanobacteria of Trichodesmium sp. (85%) dominated in Beruwala, indicating the possibility of blooms of this species at study sites when environmental conditions are favourable.

An overview of grey mullet (Mugilidae) global occurrence and species-rich ecoregions, with indications of possible past dispersal routes within the family.

This review examines the published literature on the distribution and species richness of the family Mugilidae around six continents as well as their phylogenetic relationships in a time-calibrated tree. Three mugilid species-rich regions were identified globally, namely the Coral Triangle, southern Asia and southern Africa, all of which have between 16 and 18 morphologically recognized species. Two of the species hotspots are tropical, and only southern Africa incorporates temperate waters. The centre of mugilid evolution and then global dispersion appears to be located in the tropical waters of the Indo-Pacific. Speciation within the family was promoted mainly by plate tectonics, eustatic sea-level changes, tropical climate and high habitat diversity within this region. The number of these tropical species that radiated out to the coastal waters of Africa and America was clearly less than the number that remained in the central Indo-Pacific region. Nonetheless, access by tropical mugilid species was greater to Africa than the Americas because of the direct tropical and subtropical coastal connectivity to the former continent. This enabled more tropical mugilids to reach Africa than America, with the latter probably relying on Palaeocene "island hopping" or "rafting" to move eastwards across the Pacific Ocean. In addition, tropical mugilids were able to access warm western and central African coastal waters from the Pacific prior to the closure of the Tethys Sea gap in the eastern Mediterranean and prior to the development of the cool Benguela Current upwelling off the southwest African coast, and from America through at least two transatlantic rafting events.

Phytoplankton Seasonal Dynamics under Conditions of Climate Change and Anthropogenic Pollution in the Western Coastal Waters of the Black Sea (Sevastopol Region)

The studies of seasonal phytoplankton dynamics, its growth rate, and microzooplankton grazing were conducted on two stations in the western Black Sea coastal waters near Sevastopol from January 2021 to December 2022. The phytoplankton species composition has remained relatively the same during recent years compared to the end of the last century and the beginning of the 2000s. However, significant changes have occurred in the ratio between different species of diatoms, and the proportion of dinoflagellates was increased, especially in the autumn. Large diatoms and dinoflagellates play a crucial role in forming the phytoplankton biomass seasonal peaks. The first central maximum was observed in July, and the second smaller one was in September–November. Whereas two decades ago, the small diatoms generated three peaks annually: in February, May, and September–October. The maximum values of the phytoplankton growth rate and the rate of its consumption by microzooplankton decreased 2–3 times compared to the beginning of the 2000s. The relative share of primary production consumed by microzooplankton annually averages 35%, two times lower than before.

Social-ecological connectivity and management factors of puerulus (Panulirus spp.) fisheries in the Western Coastal Waters of Lampung Province

Access limitation to capture lobster puerulus needs to be done to sustain the utilization of the resources, increase fishermen’s income and preserve the abundance of puerulus in the Western Coastal Waters of Lampung Province. The management of puerulus resources in these waters does not seem to have been well integrated within the framework of the social-ecological system (SES) of fishery resources. This study aims to analyze SES components and connectivity of lobster puerulus and identify strategic factors to be used in the context of fisheries management of lobster (Panulirus spp.). The research was conducted between October until November 2021 in West Coast Regency, Lampung Province, using SES approach. From the results, we have been revealed that there is a strong interaction and influence between the resources actor component (RA) and the resources unit (RU) in the context of the dynamics of the resources system (RS), but tends to be weak in the framework of the governance of the resource (RG). The management strategy is carried out through good collaboration between the government and resources actor to maintain puerulus abundance.

Extension of the Striped Eel Catfish Plotosus lineatus (Thunberg, 1787) from the eastern Mediterranean Coast to the Mersin Bay on the western Mediterranean Coast of Turkey

A group of schools of striped eel catfish Plotosus lineatus (Thunberg, 1787) was photographed during scuba diving at depths of 10 m and 17 m on 11 July 2022 and on 24 September 2022 from Kızkalesi and Boğsak regions in the Mersin Bay of the Mediterranean coast of Turkey. With the present study, P. lineatus is extending its distribution to the western Mediterranean coastal waters after its first occurrence in 2016 in the İskenderun Bay of Turkish Marine waters.

Catches Analysis of Scottish Seine Net Modification of Cod-end in Majene Waters, Makassar Strait

Research on Scottish Seine Net Modification of cod-end was conducted to analyze the catch. This research was carried out in the western coastal waters of Majene Regency, West Sulawesi, following the fishing operation of one unit of Scottish Seine Net, which had modified its fishing gear. The study results found ten species of fish caught with a total catch of 115.4 kg. The four most caught species were Indian scad 46.5 kg, mackerel tuna 21.5 kg, skipjack tuna 19.2 kg, rainbow runner 17.8 kg, and six other species 10.4 kg. The total catch was 115.4 kg consisting of 1753 individuals, with the composition of the species of catch consisting of Indian scad (Decapterus russelli) 56.7%, Bigeye scad (Selar crumenophthalmus) 22.6%, skipjack tuna (Katsuwonus pelamis) 9.9%, Mackerel tuna (Euthynnus affinis) 3.1% and the other six species 7.7%. The four most common catch species are the Indian scad, 7.3-25.8 cm. Bigeye scad, 6.5-20.5 cm. Skipjack tuna, 10.8-25.5 cm. And Mackerel tuna, 14.5-45.1 cm. Indian scad as the catch with the highest composition caught 62.7% were suitable for catching.

The ecological vulnerability of Semarang’s coastal waters, a brief review

As the capital city of the Central Java Province, Semarang has a very unique regional profile. Economic activity in Semarang has accelerated rapidly and many industrial estates have been established, but the latent problem of inundation and subsidence has been a threat in the northern region of the city for almost a century. Under these conditions, the burden of pollution as a by-product of various activities in the coastal and upland areas becomes a threat magnification for ecological sustainability of coastal waters and surrounding areas. This review will reveal the ecological vulnerability of coastal waters based on biogeochemical aspects. The major references for the review were several research papers dan repots based on the research activities of The Research Centre for Oceanography, Indonesian Science Institute (LIPI) in Semarang coastal water on the last decade. Geological studies, heavy metal contamination and retrospection study using benthic foraminifera as proxies based on two core samples are the major aspects on the review. The results show that the eastern coastal of Semarang was more susceptible to ecological disasters such as accretion, pollution of several metals and total suspended solids compared to the western coastal waters. Retrospective study based on core sample showed that Pb and Zn contaminations were occurred higher at the East Flood Canal estuary since 1910, so was the imprint of hypoxia was found since 1939.

Initial recovery of demersal fish communities in coastal waters of Hong Kong, South China, following a trawl ban

Fisheries resources in Hong Kong have been overexploited since the 1970s due to intensive bottom trawling and other fishing activities that have depleted stocks and destroyed marine habitat. To rehabilitate depleted fisheries resources, a permanent ban on trawling in Hong Kong territorial waters came into force on December 31, 2012. In order to determine whether the trawl facilitated recovery of fish communities, trawl surveys were conducted at two sites in each of the eastern, southern and western (estuarine) coastal waters of Hong Kong before and three years after the trawl ban. A total of 315 species and 86 families of fishes in nine feeding groups were encountered during the surveys. Mean trophic level of the fish community, abundance and biomass of total fishes and of predatory fishes increased in eastern and western waters after the ban, but no changes or declines in these metrics were observed in southern waters. Although initial recovery in fish community were observed in eastern and western waters, anthropogenic disturbances might hinder the recovery process, including a large-scale reclamation for construction of coastal infrastructures in the west, illegal trawling, and expansion of non-trawling fishing efforts in the southern and eastern waters. Longer term monitoring is needed to evaluate the effects of the trawl ban, and determine whether recovery in the southern waters will continue to be constrained by the anthropogenic disturbances.Graphic abstract

Remote sensing estimation of the concentration and sources of coloured dissolved organic matter based on MODIS: A case study of Erhai lake

The use of satellite remote sensing to estimate coloured dissolved organic matter (CDOM) and identify its potential sources is important for monitoring lake water quality and implementing management strategies. In this study, taking Erhai Lake as an example and based on MODIS/Aqua satellite images and in-situ measured data, we used empirical and semi-empirical methods to develop algorithms for CDOM and the fluorescence index (FI370) from remote sensing reflectance (Rrs(λ)). The temporal and spatial distributions of the CDOM concentration and FI370 in Erhai Lake during 2013–2019 were retrieved. The results show the following. (1) The band ratio (Rrs(469)+Rrs(645))/Rrs(555) model could estimate the CDOM absorption coefficient at 412 nm (aCDOM(412)) (R2=0.507), and it was relatively stable. Using the band ratio Rrs(645)/Rrs(469) combined with the chlorophyll-a (Chl-a) APProach by ELimination (APPEL) model, a semi-empirical inversion model of FI370 performed with satisfactory accuracy (R2=0.550) and was more accurate than the empirical algorithm (R2=0.505). (2) During the period of 2013–2019, the CDOM concentration in Erhai Lake generally decreased from the northern to the central to the southern parts of the lake, and the CDOM concentration was higher in summer and autumn than in spring and winter. FI370 was higher in the northern and western coastal waters and lower in the central, southern and eastern parts of the lake. FI370 in autumn and winter was higher than that in spring and summer. CDOM was affected by both terrestrial and internal sources, and their relative contributions were not the same in different seasons. (3) For different Chl-a concentrations, different CDOM concentration models had better retrieval effects, i.e., Rrs(645))/Rrs(555) and (Rrs(469)+Rrs(645))/Rrs(555) had the best performance when Chl-a<10 μg/L and Chl-a>10 μg/L, respectively. The inversion models established in this study offer improved quantifications of the CDOM concentration and the FI370 in Erhai Lake, providing important support for monitoring water quality and implementing efficient management strategies.

Experimental Warming Effects on Prokaryotic Growth and Viral Production in Coastal Waters of the Northwest Pacific during the Cold Season

Climate warming can directly affect biological processes in marine environments. Here, we investigated if warming (+2 °C) can change dynamics in viral and prokaryotic populations in the cold seasons in natural seawaters. We monitored the changes in viral production and prokaryotic growth rate. The prokaryotic average gross growth rates were 0.08 and 0.34 h−1 in November and 0.06 and 0.41 h−1 in December in the in situ and warming experiments, respectively. We found that warming water temperature resulted in a significant increase in prokaryotic growth rates. In warming experiments, the overall viral production rate was about 0.77–14.4 × 105 viruses mL−1 h−1, and a rough estimate of prokaryotic mortality was about 5.6–6.8 × 104 cells mL−1 h−1. Based on our estimation, burst sizes of about 21 and 14 viruses prokaryotes−1 were measured under the experimental warming period. Moreover, the results found that an increased water temperature in the subtropical western Pacific coastal waters increases prokaryotic growth rates, enhances viral production, and changes the carbon fluxes in the trophic interactions of microbes.

Spatiotemporal distribution of shrimp assemblages in the western coastal waters off Taiwan at the Tropic of Cancer, Western Pacific Ocean

Two Ocean Researcher No.3 research vessel cruises were conducted at seven sites set along the western coastal waters off Taiwan in May (late spring) and November (late autumn) 2019, to elucidate the spatiotemporal variation of the benthic shrimp assemblages. Among the 27 recorded shrimp species, the species number was higher in late autumn (20 species) due to the appearance of several oligothermal shrimps, than in late spring (15 species) with only polythermal tropical shrimps. Two shrimp assemblages, the North group and South group, were identified in the nearshore coastal waters off western Taiwan with distinct dominant shrimp species. Their spatiotemporal distribution reflects the large-scale seasonal water temperature variation driven by the cold China Coastal Current (CCC), and the warm Kuroshio Branch Current (KBC) and South China Sea Surface Current (SCSSC), as well as the shrimp preference for sediment grain size. The North group is situated north of Chiku (Qigu) (23°09′N), which is the cold CCC southbound limit in winter, and is composed mainly of subtropical shrimps, dominated by Parapenaeopsis hardwickii and P. sinica. The South group is located south of Jiading (Qieding) (22°52′N), which is annually affected by the warm KBC and SCSSC, heating the water temperature to >25 °C, even in winter, except for January. The South group is composed of mainly tropical shrimps dominated by Metapenaeopsis. palmensis, which cannot live in water temperatures <25 °C. This is the first report of tropical-subtropical shrimp assemblages formed in conjunction with the large-scale variation of the water mass and current-driven sediment grain size on a seasonal and geographical location basis. It is also shown that P. hardwickii made a northward retreat of ca. 0.5oN in the past two decades, and the baseline has been set to study the north-range shift of the tropical shrimps in the future in this location.

Spring Distribution of Ciliate Plankton in the Southeastern Yellow Sea in 2019

As planktonic ciliates have been recognized as important players in marine microbial food webs, relevant studies have been conducted in the western coastal waters of the Yellow Sea. However, little is known about ciliate distributions from the eastern coast of the Yellow Sea near the Korean Peninsula. A spring cruise in April 2019 was carried out to investigate vertical and horizontal distributions of ciliate plankton at 18 stations that form three zonal sections in the eastern area. Biological (picoplankton, nanophytoplankton, and mesozooplankton) and hydrological (water temperature and salinity) environments were also analyzed to understand relationships between the ciliate distributions and the environments. High abundance (ca. 2400 cells L−1) of a large ciliate species, Laboea strobila, was observed at the surface water of Stn. 37–5. Abundance peak of large (> 50 μm) ciliates coincided with the peak of mesozooplankton abundance. Spatial distribution of the large ciliates was associated with nanophytoplankton distribution while a smaller (20–50 μm) ciliate group was associated with picoplankton distribution. Therefore, the spring distribution of ciliate plankton in the southeastern coast of the Yellow Sea indicates that food size for the ciliates is one of the important factors controlling ciliate compositions as well as their abundances. Further investigations need to be carried out to understand seasonal differences of ciliate distributions in the eastern Yellow Sea.

The Movement Track of the Ocean Current in Jiaozhou Bay

According to the data on the investigation of Jiaozhou Bay in May, August and October, 1992, the Pb content and the horizontal distribution in the surface of Jiaozhou Bay were studied. The results show that in May, the open ocean current with a high content of Pb entered Jiaozhou Bay surrounding the nearshore waters of the bay. In August, in the waters of Jiaozhou Bay, there was only one high Pb content source - open ocean current transportation. The open ocean current entered Jiaozhou Bay with a high content of Pb. The ocean current passed from the outside of the bay to the inside through the bay mouth with 37.53 μg/L Pb content. Then the ocean current made a circle around the inshore waters of Jiaozhou Bay, bringing a high Pb content zone of 11.30 - 27.44 μg/L. At this point, a low Pb content area of 5.53 μg/L appeared in the central waters of Jiaozhou Bay. So, in August, the open ocean current with a high content of Pb moved into Jiaozhou Bay. Then it surrounded the nearshore waters of the bay. By the authors’ Dongfang Yang’s migration law of material content, it is obtained that the open ocean current with high Pb content moves into Jiaozhou Bay. And with the continuous decrease of Pb content, the flow path of the open ocean current in the bay, illustrated by a model block diagram, is left. Furthermore, the migration law reveals that the unit water body with the ocean current returns to the inlet water in a counterclockwise direction along the inshore water in the bay. Thus, under the combined action of ocean current and tide, this unit of water body shows zigzag movement from east to north and to west along the eastern, northern and western coastal waters of Jiaozhou Bay, leaving the center of the bay barely affected by the unit water. The unit body of water has a circular center in the center of the bay and a zigzag motion along the edges. Moreover, the topography and geomorphology of the bottom of Jiaozhou Bay also confirm the movement track of the ocean current in the waters of Jiaozhou Bay proposed by the authors.

FEATURES OF FORMATION OF THE WINTER PLANKTON COMMUNITIES IN THE NEFTEGAVAN (“OIL HARBOUR”) - MAKHACHKALA AREA OF THE MIDDLE COASTAL CASPIAN

Made has been the analysis of the pelagic ecosystems state in the Western coastal waters of the Middle Caspian in winter period of 2020 in the Neftegavan area, Seaport of Makhachkala. The taxonomic composition of phytoplankton and zooplankton communities, and the density of hydrobionts inhabiting them have been determined. It is noted that in phytocenoses during mass blossom of Rhizosolenia calcar avis (Schultze,1843) the diatom water plants (Bacillariophyta) dominated, and in zooplankton communities the paddle-footed crustaceans, mainly acarcidis ( Acartai tonsa Dana,1843) dominated on abundance. All sampling stations were characterized by a high degree of similarity of phyto-zooplankton in taxonomic composition but they differed significantly in number and biomass.