Sea Surface Layer Research Articles

Effect of Certain Abiotic and Biotic Factors on Spawning of the European Sprat Sprattus sprattus (Linnaeus, 1758) in the Black Sea in November 2016–2017

The study examines changes in the abundance (density) and distribution of European Sprattus sprattus (Linnaeus, 1758) eggs and larvae, as well as the phenology of its spawning depending on hydrologic factors and abundance of gelatinous macroplankton in the Black Sea in November 2016–2017. An increase in temperature of the sea surface layer observed since the beginning of the century and the enhanced heat content of the cold intermediate layer contributed to the preservation of warm-water mesozooplankton at the end of the fall hydrologic season, which provided favorable trophic conditions for all planktophages. The biomass of scyphomedusa Aurelia aurita was the third largest in the gelatinous macroplankton in 2016 and the largest in 2017 for the long-term annual research in fall months. Gelatinous macroplankton, however, did not have a significant impact on the survival of sprat in the early stages of its development. The average number of sprat eggs and larvae in November 2016 (184 and 11 ind/m2, respectively) and November 2017 (268 and 21 ind/m2, respectively) exceeded their maximum values recorded in the 1950s. The larvae did not differ in length composition in the beginning of the spawning season in 2016 and 2017.

Rezhim biogennykh elementov Chernogo morya

Purpose. One of the key characteristics of water quality and marine ecosystems’ sustainability is nutrients supply, which are the main factors of phytoplankton bloom. Since the mid 20th century, in the northwestern Black Sea and on its western shelf, significant changes in nutrients concentrations took place, which were manifested in increase of the inorganic nitrogen and phosphorus concentrations, and decrease of the dissolved silicon content, that in its turn, led to a strong anthropogenic eutrophication of the above-mentioned regions. The aim of the work is to assess the current state of the Black Sea based on the data on the nutrients distribution and dynamics in the surface water layer. Methods and Results. The data obtained in the cruises of R/V “Professor Vodyanitsky” in 2016–2019 were analyzed. The main regions under study included the deep part of the Black Sea, as well as the Crimean and Caucasian sectors of the economic zone of Russia. The data obtained showed significant variability in the nutrients concentration both in the coastal and open areas. Conclusions. A decrease of nutrients concentration in 2016–2019 as compared to that in 2009–2014 was noted, that can indicate a decrease in the eutrophication degree and an improvement of the Black Sea waters quality. Intra-annual variability of the nutrients concentration in the sea surface layer is observed. No pronounced features in spatial variability of the nutrients concentration in this layer were revealed. It is assumed that in the central deep part of the sea, their concentrations are conditioned mainly by the physical processes of water transfer. In addition to physical transport, the increased nutrients concentrations in the coastal areas are, probably, also related to influence of the anthropogenic factor, namely inflow of nutrients from the coastal sources or their formation resulting from the biogeochemical processes which include organic matter.

Genetic structure and life history are key factors in species distribution models of spiny lobsters.

AimWe incorporated genetic structure and life history phase in species distribution models (SDMs) constructed for a widespread spiny lobster, to reveal local adaptations specific to individual subspecies and predict future range shifts under the RCP 8.5 climate change scenario.LocationIndo‐West Pacific.MethodsMaxEnt was used to construct present‐day SDMs for the spiny lobster Panulirus homarus and individually for the three genetically distinct subspecies of which it comprises. SDMs incorporated both sea surface and benthic (seafloor) climate layers to recreate discrete influences of these habitats during the drifting larval and benthic juvenile and adult life history phases. Principle component analysis (PCA) was used to infer environmental variables to which individual subspecies were adapted. SDM projections of present‐day habitat suitability were compared with predictions for the year 2,100, under the RCP 8.5 climate change scenario.ResultsIn the PCA, salinity best explained P. h. megasculptus habitat suitability, compared with current velocity in P. h. rubellus and sea surface temperature in P. h. homarus. Drifting and benthic life history phases were adapted to different combinations of sea surface and benthic environmental variables considered. Highly suitable habitats for benthic phases were spatially enveloped within more extensive sea surface habitats suitable for drifting larvae. SDMs predicted that present‐day highly suitable habitats for P. homarus will decrease by the year 2,100.Main conclusionsIncorporating genetic structure in SDMs showed that individual spiny lobster subspecies had unique adaptations, which could not be resolved in species‐level models. The use of sea surface and benthic climate layers revealed the relative importance of environmental variables during drifting and benthic life history phases. SDMs that included genetic structure and life history were more informative in predictive models of climate change effects.

Vertical Distribution of Bio-Optical Properties of the Azov – Black Sea Basin Waters in April – May, 2019

Purpose. The work is aimed at investigating spatial distribution of the chlorophyll a concentration and the spectral light absorption coefficients by all optically active components in the Azov and Black seas in spring, when the seawater hydrophysical structure changes. Methods and Results. The data collected in the 106th scientific cruise of R/V Professor Vodyanitsky in April 19 – May 10, 2019 were used. The chlorophyll a concentration was measured by the spectrophotometric method. The spectral light absorption coefficients were determined in accordance with the NASA protocol 2018. The optical measurements were performed using the dual-beam spectrophotometer Lambda 35 (PerkinElmer). It was shown that in the surface layer of the Black Sea, the chlorophyll a concentration varied from 0.21 to 1.2 mg/m3. At some stations in the deep-water region, the increased values of this parameter were observed in the lower part of the euphotic zone that was associated with the beginning of seasonal water stratification due to the surface water heating. At these stations, the phytoplankton absorption spectra were more smoothed in the lower part of the euphotic zone than those in the upper layer. In the deep-water region, the non-algal particles contribution to the total particulate light absorption at wavelength 438 nm changed with depth from 40 ± 15 % at the surface to 29 ± 12 % near the bottom of the euphotic zone; whereas in the coastal waters this parameter was almost unchangeable within the water column (54 ± 11 %). No significant change of the colored dissolved organic matter contribution to the total light absorption with depth was revealed (69% on average). In the Sea of Azov, vertical distribution both of the chlorophyll a concentration (6.2 mg/m3 on average) and the spectral light absorption coefficients by all the optically active components was uniform. The non-algal particles contribution to the particulate light absorption was 40 ± 14 %, and the colored dissolved organic matter contribution to the total light absorption constituted 52 ± 6 %. Conclusions. New data on spatial distribution of the chlorophyll a concentration and the spectral light absorption coefficients by the optically active components in the Black and Azov seas were obtained for the spring period when the seawater hydrophysical characteristics changed.

Assessment of Applicability of Satellite-Derived Ocean Color Data for Studying Variability of Total Suspended Matter in the Surface Layer of the Deep Part of the Black Sea

Purpose. Studies of spatial-temporal variability of total suspended matter are necessary for understanding the biochemical processes which form and support stable functioning of a marine ecosystem. The aim of the work is to assess applicability of satellite data for studying total suspended matter variability in the surface layer of the deep part of the Black Sea. Methods and Results. Application of the regression analysis yielded the linear regression equations that unite the in situ measurements of the total suspended matter concentrations in the surface layer in the northeastern (June, 2005–2015) and western (November, 2016, 2017 and December, 2017) deep sea areas, and the regional satellite products (the particulate backscattering coefficient, the absorption coefficient of colored detrital matter and the chlorophyll a concentration). Based on the measured and calculated data arrays, the maps of the total suspended matter concentrations in the surface layer of the northeastern Black Sea were constructed. The interannual changes in the in situ measured concentrations of the total suspended and lithogenic matters, as well as in the quasi-synchronous satellite regional products (the light absorption coefficient of colored detrital matter at 490 nm and the particulate backscattering coefficient at 555 nm) in June, 2005–2015 were considered. High total suspended matter concentrations were noted in 2012, just when extreme growth of the coccolithophorid population was observed in the Black Sea. The correlation coefficients were used to evaluate whether the relation between the total suspended matter concentration and the individual analyzed parameters was fast. Conclusions. Spatial distributions of the measured and calculated total suspended matter contents showed satisfactory agreement. In course of the whole observation period, difference between the values of the measured and calculated total suspended matter concentrations was on average 6–23 %. Possibility of application of the satellite-derived ocean color data for studying spatial-temporal variability of the total suspended matter content is shown.

Влияние повышения температуры поверхностного слоя моря на потенциальную пополняемость популяции мидии у берегов юго-западного Крыма

The article discusses the possibility of a connection between an increase in the temperature of the surface layer of water and a decrease in the potential replenishment of the Black Sea population of the mussel Mytilus galloprovincialis recruitment off the southwestern coast of Crimea in recent decades. The considered biological parameter is characterized by the number of mussel post-larvae, formed planktonic larvae that settled on the experimental substrate per unit of time (usually a month). The study of water temperature variability in the region showed that from the 80s of the last century to the present, there has been an increase in the average annual temperature of the surface water layer by about 2 ° C. The maximum increase in water temperature was noted during the warm period of the year, especially in June, July and September – during these months it was about 5°C. This ecological change took place against the background and, very likely, due to the previously noted processes of global warming, freshening of the surface layer of the Black Sea, a decrease in its vertical mixing, a decrease in the frequency and duration of coastal upwellings, and an increase in the eastern component in the surface wind speed in the region, contributing to the intensification of surge phenomena off the coast of Crimea. All these processes can lead to a decrease in the productivity of the surface layer of the sea, and, consequently, in the reproductive potential of the mussel population, as well as to a decrease in the probability of its larvae appearing in mass number at the stage of settling in the coastal zone during upwellings. In addition, a significant increase in the temperature of surface water in the Black Sea in the warm season can contribute to the food and reproductive activity of the predatory Rapana, feeding mainly on mussels, as well as to the survival of its juveniles. Thus, an increase in the temperature of the surface layer of the sea and the processes leading to this increase can directly or indirectly contribute to a decrease in the potential recruitment replenishment of the mussel and a decrease in reproduction of its population in the Black Sea.

A model for the estimation of the mixing zone behind large sea vessels.

One of the important tasks associated with reducing the concentration of contaminants in the sea surface layer is the determination of their mixing volume, as of the most active systems for mixing the sea surface layer are sea vessels. The wake of a ship is a highly mixed medium. The study of the wake development over time is important when evaluating the mixing of various pollutants in the wake with neutralizing chemicals. As shown in some previous works, in the wake of a vessel that crosses a contaminated surface, the concentration of harmful impurities decreases to background values; however, the problem of determining the volumetric characteristics of this wake remains. In our work, we propose a relatively simple model for assessing the characteristics of a turbulent wake in the near zone behind a vessel. Based on the actual parameters of the vessels, the parameter F= (penetration depth) / (draft) was calculated, which characterizes the potential mixing effects caused by turbulence in the wake. The proposed simple model can be used, for example, to assess the mixing of oil when it is being bottled, with chemicals, to assess possible scenarios of increasing its dilution.

Distribution of 137Cs in the Surface Layer of the Black Sea in Summer, 2017

Distribution of 137Cs in the Surface Layer of the Black Sea in Summer, 2017

Raspredelenie 137Cs v poverhnostnom sloe Chernogo morya letom 2017 goda

Raspredelenie 137Cs v poverhnostnom sloe Chernogo morya letom 2017 goda

Plastic of the Solid Domestic Waste on the Coastal Zone of the Northwestern Part of the Black Sea as a Component of Marine Littre

Purpose. The goal of the study is estimation the scale of the plastic waste’s area in the coastal zone of the Northwestern part of the Black Sea and their role of the of polution formation. Methods. The base of methods is system analyses. Results. The annual volume of solid waste in the North-Western Black Sea region can reach 2.5 million tons per year, and the volume of plastic littre - up to 323 thousand tons per year. In spite of of plastic littre as the resource, at present there is no definite system for handling them, and under these conditions they are disposed of at numerous dumps (including unauthorized ones) of solid household waste. A significant part of plastic (up to 80%) from unorganized landfills and from the other coastal pollution sources is carried out by air and water flows in the water area of the Northwestern part of the Black Sea. Approximatly 83% of marine littre in the Black Sea is plastic. In turn, the presence of marine littre links with the imperfection of the solid waste management system. The dominant way of manage is remains their removal and disposal in landfills. As of 2019, in the Odessa region there were 528 landfills, in the Nikolaev region - 267, in the Kherson region - 54. Almost 17% of landfills in the Odessa region and 26% in the Nikolaev region do not comply according to environmental hazard standards. Significant part of the plastic littre, first of all from unauthorized of the solid waste dumps, is carried by air flows into the river network, and if they are close to the beach area, directly into the Black Sea. Plastic littre is carried out from the catchment areas of the large rivers (Danube, Dniester, Southern Bug and Dnieper), as well as water intakes of numerous medium and small rivers. Almost the whole beach area of the Northwestern part of the Black Sea is actively used for recreational purposes and, therefore, is a source of beach waste. In addition, the coastal sources of garbage can be settlements, marine complexes and agricultural lands located along the coastal line. An insignificant share of plastic littre is generated within the sea area (from shipping, fishing, etc.). Conclusions. The main component of marine littre is plastic, as it accounts for 83% of marine littre founded in the Black Sea. Macroplastics can be subject to long-term movement by the sea currents, winds, waves and poses a direct threat to the marine ecosystem. Directions of movement of marine littre depends on the processes of general circulation in the surface layer (0-500 m) of the Black Sea. The processes of biodegradation of macroplastic are hindered in the marine environment, and therefore its transformation is limited by the processes of destruction and dispersion in micro- and nanoparticles. Taking into consideration the environmental hazard of microplastics, it is advisable to create a system for monitoring in the marine environment. To improve the environmental situation in the coastal zone of the Northwestern part of the Black Sea, it is necessary to significantly increase the volume of recycled plastic littre, as well as to eliminate numerous landfills for solid household waste that do not accord to environmental safety requirements.

Effect of phytoplankton adaptation on the distribution of its biomass and chlorophyll a concentration in the surface layer of the Black Sea

Abstract Using the field data collected in the Black Sea in September 2005–May 2013, the authors studied the spatial variability of the ratio of organic carbon to chlorophyll a (C:Chl a) in the sea surface layer (0–1 m). The C:Chl a ratio is an important parameter that reflects the phytoplankton adaptation to abiotic factors. Its maximum variations occurred in September–October 2005 and October 2010 when the highest spatial variability of average light intensity and nitrogen concentration was observed in the upper mixed layer. As a result, the maps of phytoplankton biomass differed from chlorophyll maps. In August 2011, no effect of light or nitrogen on the spatial variability of the C:Chl a ratio was found. Changes in the contribution of dinoflagellates to the total phytoplankton biomass affected the C:Chl a ratio variability, which was two times lower compared to September–October 2005 and October 2010. Also, the spatial distribution of phytoplankton biomass differed from the distribution of chlorophyll a concentration only in some areas of the sea. In May 2013, environmental factors slightly varied across the study area and the spatial variability of the C:Chl a ratio was insignificant. Therefore, the map of phytoplankton biomass indicated similarities with the chlorophyll map.

Osnovnye zakonomernosti dolgovremennoy evolyutsii khalinnoy stratifikatsii Chernogo morya

Purpose. At present the process of formation of haline stratification in the Black Sea is poorly studied. The current state of the basin is considered to be close to equilibrium. However, having been analyzed, the long-term observations testify to a tendency towards desalination of the sea surface layer and salination of the deep waters. The goal of the study is to obtain a complete pattern of the haline stratification formation in the basin and the characteristic time scales of its long-term climatic evolution. Methods and Results. Numerical calculations of the Black Sea circulation which is formed being influenced by water exchange through the Bosporus, river runoff, precipitation and evaporation, are compared with the laboratory simulation results obtained previously using the NEMO model. It is shown that the time period of formation of the upper and lower Bosporus currents is of a characteristic time scale 20 years. Relatively short period of adaptation of the Bosporus water exchange to the external conditions testifies that on the climatic scale, the strait should be in a quasi-equilibrium state. The results of the numerical experiments also show that, against the background of the initially preset constant salinity of the Black Sea, the vertical haline stratification is formed rather rapidly due to the fact that the upper forty-meter layer is desalinated by the river runoffs. This leads to formation of a halocline in the 10–40 m layer. In the deeper layers, salinity increases slowly owing to the Marmora Sea water inflow. Each of the calculations shows that intense desalination of the surface layer lasts 70–80 years, whereupon its salinity grows slowly. Conclusions. As a result, the characteristic adaptation period of the basin stratification to the changes in the external factors constitutes 70–100 years. After the equilibrium regime is settled, slow quasi-stationary evolution of the basin fields takes place. Analysis of the obtained results enabled us to deduce the equations for describing slow evolution of the haline stratification.

Optimal Assimilation of Daytime SST Retrievals from SEVIRI in a Regional Ocean Prediction System

Exploiting the potential of space-borne oceanic measurements to characterize the sub-surface structure of the ocean becomes critical in areas where deployment of in situ sensors might be difficult or expensive. Sea Surface Temperature (SST) observations potentially provide enormous amounts of information about the upper ocean variability. However, the assimilation of daytime SST retrievals, e.g., from infrared sensors into ocean prediction systems, requires a specific treatment of the diurnal cycle of skin SST, which is generally under-estimated in current ocean models due to poor vertical resolution at the air–sea interface and lack of proper parameterizations. To this end, a simple off-line bias correction scheme is proposed, where the bias predictors include, among others, the warm layer and cool skin warming/cooling deduced from a prognostic model. Furthermore, a localization procedure that limits the vertical penetration of the SST information in a hybrid variational-ensemble data assimilation system is formulated. These two novelties are implemented and assessed within a regional ocean prediction system in the Ligurian Sea for the assimilation of daytime SST data retrieved with hourly frequency from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) onboard the geostationary satellite Meteosat-10. Experiments are validated against independent measurements collected by gliders, moorings, and drifters during the Long-term Glider Missions for Environmental Characterization (LOGCMEC17) sea trial. Results suggest that the simple bias correction scheme is effective in improving both the sea surface and mixed layer accuracy, correctly thinning the mixed layer compared to the control experiment, outperforming experiments with night-only data assimilation, and improving the forecast skill scores. Localization further improves the prediction of the mixed layer depth. It is therefore recommended that sophisticated bias correction and localization procedures are adopted for fruitfully assimilating daytime SST data in operational oceanographic analysis systems.

СТРУКТУРА ВЫНОСА Р. ШАХЕ В ЧЕРНОМ МОРЕ ПО ДАННЫМ ДИСТАНЦИОННЫХ, ПИРОМЕТРИЧЕСКИХ И КОНТАКТНЫХ ИЗМЕРЕНИЙ

The results of studies of hydrophysical and bio-optical structure of the outflow of the Shakhe River, conducted during the IO RAS expedition “Black Sea-2018” at the marine site near Golovinka on the RV “Ashamba” on 1–2 June 2018, are presented. Information synchronously obtained, both with the help of remote sensing satellites (radar and optical sensors), infrared portable pyrometer, and onboard the RV (CTD probe as part of a shipboard flow system), was used. At the same time, seawater samples were taken from the sea surface layer, followed by laboratory analysis of their bio-optic and geochemical characteristics. Hydrophysical characteristics and submesoscale structure of the Shakhe River outflow at the test site studied both remotely and contactly, gave identical results. This makes it possible to further efficiently use these instruments on board of RVs to study the river outflows in the Black Sea. At the same time, portable infrared pyrometers make it possible to obtain significantly better spatial resolution in terms of temperature compared with satellite instruments, while satellite images can detect river outflows in the sea, their boundaries and structure.

Remote Tracking to Monitor Ship Tracks at or near the Water Surface

The tracking of hydrodynamic disturbances within the sea surface and near-surface layer and surface layer aerosol is performed using three different installations, a laser locator, photometer of sea brightness, and elastic aerosol lidar. The experiments are carried out under the natural conditions of the Black Sea polygon. A surface vessel was a source of hydrodynamic perturbations in the form of a lagging track. The results reveal the efficiency of the methods used to record ship tracks in three media.

The role of river runoff in the Kara Sea surface layer acidification and carbonate system changes

This study aims to perform the results of the investigation of the Kara Sea carbonate system (CS) changes and the factors that determine it. The important feature of the Kara Sea water structure is strong stratification caused mainly by the Ob’ and Yenisey rivers discharge which is estimated as 81% of the total continental runoff to sea. Occurring climate changes, as an increase in the total volume of the Arctic Ocean water (due to melting of glaciers, sea ice decline and river runoff increase), air temperature and CO2 concentration growth should affect greatly the Kara Sea CS. However, riverine water influence seems to be the main driver of future acidification of the Kara Sea water due to permafrost thawing as it stores a great amount of buried carbon. An increase of carbon (mainly inorganic) flow to the sea will lead to carbonate equilibrium shift, oxidation of organic matter and release of CO2 that ultimately leads to a decrease in pH and therefore acidification. The area of the riverine plume depends on the amount of freshwater flowing into the sea and the conditions of the wind forcing. According to the data from Shirshov Institute cruises within the plume area aragonite saturation is below 1 that shows its state as acidified. Prevalence of pCO2 values in the freshened surface layer over the atmospheric shows that atmospheric carbon dioxide, apparently, cannot serve as the main driver for the acidification of the surface waters of the Kara Sea. At the shallow shelf to the north of the Ob′ Inlet mouth we observe acidification of the whole water column from surface to the bottom layer due to elevated riverine discharge and increase of flowing terrestrial carbon.

Feature of formation of the Black Sea surface layer temperature during air cold intrusions

Application of the results of the drifter observations performed in the western Black Sea permitted to show that during air cold intrusions (CI) in winter accompanied by the wind (10 m/c and more), the upper mixed layer (UML) was cooled by 0,1-0,2 °C in course of a day. At that the seasonal thermocline (ST) and the cold intermediate water (CIW) sink deeper; after CI is over these layers rise to the depths smaller than their previous ones. It results in decrease of temperature in UML and its increase, as compared to the period preceding CI, in the layer below ST. The process of the sea upper layer mixing is explained by the fact that anti-cyclonic mesoscale vortices are involved in it.

Оценка средней температуры поверхностного слоя Азовского моря на основе данных спутниковой съёмки и наблюдений прибрежных гидрометеостанций

Оценка средней температуры поверхностного слоя Азовского моря на основе данных спутниковой съёмки и наблюдений прибрежных гидрометеостанций

Use of Satellite Data for the Estimation of the Specific Growth Rate of Phytoplankton in the Surface Layer of the Black Sea

A regional model is proposed for the estimation of the specific growth rate of phytoplankton in the sea surface layer using satellite data. The model is based on phytoplankton photosynthesis rate and biomass in organic carbon units. The phytoplankton photosynthesis rate was calculated based on ecological and physiological characteristics that were previously obtained for the Black Sea. The input parameters of the model are the chlorophyll concentration in the surface layer, water temperature, the intensity of the photosynthetic active radiation falling on the sea surface, the depth of the mixed layer, and the diffuse light attenuation coefficient. Seasonal variations in specific growth rate of phytoplankton were estimated for deep-water and near-Danube areas. The maximum values were found in the coastal area in May–June, the minimum values were observed in deep waters before the spring maximum of phytoplankton. The maximum and minimum values differed by a factor 5. The measured and calculated values of phytoplankton specific growth rate at individual stations and in selected extensive areas of the sea were fairly close. The model can be used for rapid estimation of the specific growth rate of phytoplankton in the sea surface layer using satellite data.

Review of Tide and Wind Affect to Currents Pattern in Amurang Bay, North Sulawesi, Indonesia

Winds, tides and river discharges largely drive coastal currents. The strength of tidal currents, river runoff, meteorological conditions, shoreline configuration, water depth and topography are the factors that affect coastal water circulation. Generally currents are the flowing of water mass caused by wind, difference of density or tide moving. The existence of currents direction to nearshore of Amurang Bay was studied with using computer model tools as the hydrodynamic model by determine currents speed and its direction.The study took place in Amurang Bay as the province of North Sulawesi Indonesia with the geography position around 1012’16.16” N-124027’04.33” E to 1015’43.80” N-124032’01.06”E. The bathymetry and tide data used in this research from Indonesian Coastline Environmental map of year 1995 with scale 1:50.000 from BIG (Badan Informasi Geospasial) with a satellite data from Google earth of year 2018 and LANTAMAL Manado, the wind and current data was obtained from BMKG Bitung. Time simulations are taken from 25 November to 23 December 2016 as a wet season and 25 Mei to 23 Juni 2016 as a dry season. As analytical tools, MIKE3 hydrodynamic mode are used. The currents pattern play an important role in sediment transport process, so the study of the currents pattern become to be important as well. The result of this study indicate that in the wet season the combination of tide wind in surface and bottom layer of sea the currents direction close to nearshore dominant to East with current speed average 0.18 m/s, in dry season the combination of tide wind in surface layer of sea the currents direction close to nearshore dominant to South-East with current speed 0.12-0.24 m/s, in bottom layer the currents direction dominant to South-East with current speed average 0.2 m/s. Some of interesting point in research’s area show that current by tide make the current direction seaward and landward, but tide combination wind change the direction of current. It can be said that the tide influenced to current make the currents direction seaward and landward follow the pattern of tide, but combination tide and wind change its direction.