Coastal Waters In Summer Research Articles

The external/internal sources and sinks of greenhouse gases (CO2, CH4, N2O) in the Pearl River Estuary and adjacent coastal waters in summer

Estuary acts as a hotspot of greenhouse gases (GHGs, including CO2, CH4 and N2O) to the atmosphere. However, the GHGs budgets, including input/output fluxes through interfaces and biogeochemical source/sink processes in water columns, of the estuarine systems are still not well constrained due to the lacking of comprehensive observational data. Here, we presented the spatial distributions of GHGs of surface/bottom water and sediment porewater along the Pearl River Estuary (PRE) and adjacent region during summertime. The incorporation of the monitoring for the sediment-water interface (SWI) with these of the water-air interface (WAI) allows us to close the budget revealing additional information of internal consumption/production processes of the three GHGs. The oversaturated CO2 (481–7573 μatm), CH4 (289–16,990 %) and N2O (108–649 %) in surface water suggested PRE is a significant GHGs source to the atmosphere, in which CO2 is the major contributor accounting for 90 % of total global warming potential (GWP), leaving 2.8 % from CH4, and 7.2 % from N2O. Addition to the river input, the SWI releases GHGs to the overlying water with fluxes of 3.5 × 107, 10.8 × 104 and 0.7 × 104 mol d−1 for CO2, CH4 and N2O, respectively. Although all three GHGs exhibited emission to the atmosphere, our mass balance calculation showed that 16.9× 107 mol d−1 of CO2 and 1.0 × 104 mol d−1 of N2O were consumed, respectively, inside the estuary water body, while extra-production (13.8 × 104 mol d−1) of CH4 was demanded in the water body to support its output flux. This is the first experiment quantitatively assessing the importance of internal carbon and nitrogen biogeochemical processes in the PRE. Our finding is of guiding significance to constrain the GHGs budget and draw up realistic pathways for modeling works of GHGs prediction.

Fishery Resource Evaluation with Hydroacoustic and Remote Sensing in Yangjiang Coastal Waters in Summer

Yangjiang coastal waters provide vital spawning grounds, feeding grounds, and nursery areas for many commercial fish species. It is important to understand the spatial distribution of fish for the management, development, and protection of fishery resources. In this study, an acoustic survey was conducted from 29 July to 5 June 2021. Meanwhile, remote sensing data were collected, including sea surface temperature (SST), chlorophyll concentration (Chla), sea surface salinity (SSS), and sea surface temperature anomaly (SSTA). The spatial distribution of density and biomass of fish was analyzed based on acoustic survey data using the geostatistical method. Combining with remote sensing data, we explored the relation between fish density and the environment based on the GAMs model. The results showed that fish are mainly small individuals. The horizontal distri-bution of fish density had a characteristic of high nearshore and low offshore. In the vertical direc-tion, fish are mainly distributed in surface-middle layers in shallow waters (<10 m) and in middle-bottom layers in deeper waters (>10 m), respectively. The deviance explained in the optimal GAM model was 59.2%. SST, Chla, SSS, and longitude were significant factors influencing fish density distribu-tion with a contribution of 35.3%, 11.8%, 6.5%, and 5.6%, respectively. This study can pro-vide a scientific foundation and data support for rational developing and protecting fishery re-sources in Yangjiang coastal waters.

Barrier Effect of the Pearl River Estuarine Plume on Wind‐Induced Coastal Upwelling of Nutrients

AbstractCoastal upwelling caused by winds seasonally occurs in summer in the Northern South China Sea. The alongshore prevailing southwest winds, induced by East Asia Summer Monsoon, exert a uniform Coriolis force to drive the surface water offshore, which in turn pushes the deeper coastal water upward. The common view is that coastal upwelling brings up nutrients from deep water. The presence of a buoyance layer such as the riverine or estuarine plumes damps the Ekman effect and hence upwelling. However, the semi‐quantitative analysis of reduced upwelled nitrate amount due to plume (barrier) effect during this interactive process is rare. To examine the dynamics of water masses and nutrient upward transport process in the coastal waters in summer, vertical profiles of temperature, salinity, and nitrate were taken along the transects from the Pearl River estuary to 150 km offshore in July cruise of 2002 in the northern South China Sea. The results show a three‐layer structure resulting from the three water masses under the impact of a large buoyant plume: high‐nutrient plume water in the surface layer, undetectable‐nutrient offshore surface water in the middle layer, and low‐nutrient deep water in the bottom layer. This structure indicates that this middle layer was the offshore surface water entrained underneath the estuarine plume and hence, weakened the intensity of upwelling. Upwelled nitrate amount is reduced by ∼30%–35% from the deep water to the surface layer due to the middle layer based on our estimate. The finding suggests that the presence of estuarine plumes plays an important role as a barrier to weaken upwelling of deep water and subsequently reduce the upward transport of nutrients by wind‐induced coastal upwelling and therefore, such the barrier effect should be considered in estimating budgets of nutrients and subsequent carbon fixation in coastal waters.

Spatial distribution and inter-annual variability of spawning grounds of Cynoglossus joyneri in the Yellow Sea coastal waters in summer

With survey data from three voyages in the summer of 2014, 2016, and 2017, spatial distribution and inter-annual variability of spawning grounds of Cynoglossus joyneri in the coastal waters of Yellow Sea were examined based on Tweedie-generalized additive model (GAM). The results showed that the spawning grounds of C. joyneri mainly distributed in the Haizhou Bay ranging within 34°00'-35°18' N, 119°30'-121°30' E. The other one in Subei Shoal 32°18'-34°00' N, 120°18'-122°00' E. Fish eggs of C. joyneri were few in the southern waters of Shandong Peninsula 34°42'-36°48' N, 119°30'-122°00' E. The distribution of fish eggs was significantly related to the location (i.e., longitude and latitude), depth, and sea surface temperature, and did not relate to the sea surface salinity and surface chlorophyll a. The optimal range of depth, sea surface temperature, sea surface salinity, and surface chlorophyll a were 15-26 m, 29-32 ℃, 22-25 and 0.10-3 mg·m-3, respectively. There was notable inter-annual variability in the spatial distribution of spawning grounds of C. joyneri and its influencing factors. Overall, the distribution of spawning grounds is relatively stable, but potentially move northward in the year with high sea surface temperature.

Thermal response to the surface heat flux in a macrotidal coastal region (Nuevo Gulf, Argentina)

At mid-latitudes, sea water temperature shows a strong seasonal cycle forced by the incident surface heat flux. As depth decreases, the heat flux incidence is damped by the horizontal flux, which prevents the indefinite growth of the seasonal temperature range. In the present work, cross-shore transport in the west coast of Nuevo Gulf (Argentina) was analyzed. Processes tending to cool the coastal waters in summer and to warm the coastal waters in winter, were identified through temperature measurements, surface heat flux and tidal height. The simplified models proposed here provide a feedback mechanism that links changes in surface heat flux with changes in the horizontal heat flux during both seasons. On shorter time scales, tide produces significant variations in the height of the water column, therefore influencing temperature fluctuations and the direction of the horizontal flow.

New evidence links changing shelf phytoplankton communities to boundary currents in southeast Tasmania

Southern Tasmanian shelf waters are host to the seasonal interplay of Australia’s two poleward boundary currents; the East Australian Current (EAC) and the Leeuwin Current (LC). While the behaviour and properties of the LC remain underexplored, strong research focus has allowed insight into how an intensifying EAC has created greater subtropical influence, leading to changes in the physical and biological oceanography of the region. In this cool temperate setting seven species of dinoflagellates, all in the genus Ceratium, which are more typically associated with warm waters of eastern Australia, were observed. This coincided with the seasonal increase in the EAC’s southward penetration beginning in October. Despite the seasonal peak in EAC activity, temperature-salinity plots, nutrient, chlorophyll a and phytoplankton concentrations all indicate the presence of subantarctic waters on the shelf and in coastal waters in summer. Our results are consistent with the description of the EAC as an erratic, eddy-driven current; this itself allowing the periodic influx of subantarctic waters across the shelf. In winter, temperature-salinity plots and nutrient concentrations indicate that the LC was present in southern shelf waters. In addition to its high nitrate signature, the LC displayed low silicate properties in southern Tasmania. Chlorophyll a concentrations revealed a distinct spring bloom event and an extended, productive summer, typical of temperate and subantarctic systems, respectively. This suggests the region is a transitional state between classic seasonal primary production cycles for temperate and subantarctic waters. This paper links changes in southern Tasmanian microphytoplankton communities to shelf ventilation by the EAC, the LC and subantarctic waters, and provides new insight into the oceanography of the region. Consequently, this study provides an awareness of potential phytoplankton perturbations that may be applied to other coastal cool temperate marine environments.

Distribution of Roseobacter RCA and SAR11 lineages and distinct bacterial communities from the subtropics to the Southern Ocean

We assessed the composition of the bacterioplankton in the Atlantic sector of the Southern Ocean in austral fall and winter and in New Zealand coastal waters in summer. The various water masses between the subtropics/Agulhas-Benguela boundary region and the Antarctic coastal current exhibited distinct bacterioplankton communities with the highest richness in the polar frontal region, as shown by denaturing gradient gel electrophoresis of 16S rRNA gene fragments. The SAR11 clade and the Roseobacter clade-affiliated (RCA) cluster were quantified by real-time quantitative PCR. SAR11 was detected in all samples analysed from subtropical waters to the coastal current and to depths of > 1000 m. In fall and winter, this clade constituted < 3% to 48% and 4-28% of total bacterial 16S rRNA genes respectively, with highest fractions in subtropical to polar frontal regions. The RCA cluster was only present in New Zealand coastal surface waters not exceeding 17 degrees C, in the Agulhas-Benguela boundary region (visited only during the winter cruise), in subantarctic waters and in the Southern Ocean. In fall, this cluster constituted up to 36% of total bacterial 16S rRNA genes with highest fractions in the Antarctic coastal current and outnumbered the SAR11 clade at most stations in the polar frontal region and further south. In winter, the RCA cluster constituted lower proportions than the SAR11 clade and did not exceed 8% of total bacterial 16S rRNA genes. In fall, the RCA cluster exhibited significant positive correlations with latitude and ammonium concentrations and negative correlations with concentrations of nitrate, phosphate, and for near-surface samples also with chlorophyll a, biomass production of heterotrophic prokaryotes and glucose turnover rates. The findings show that the various water masses between the subtropics and the Antarctic coastal current harbour distinct bacterioplankton communities. They further indicate that the RCA cluster, despite the narrow sequence similarity of > 98% of its 16S rRNA gene, is an abundant component of the heterotrophic bacterioplankton in the Southern Ocean, in particular in its coldest regions.

Distribution of sunken macroalgae against the background of tidal circulation in the coastal waters of Qingdao, China, in summer 2008

A high‐resolution, three‐dimensional, POM‐based numerical model is developed to study the distributional responses of sunken algae (SA) in a massive macroalgal bloom, which occurred in Qingdao coastal waters in summer 2008, to the barotropic tidal currents which dominate the dynamic circulation system. Validated by in situ observation of both sea level and buoy‐measured current data, the model shows satisfactory performance in reproducing the tidal system. An indicator BotDIV, the integral of velocity divergence of bottom flow over hours preceding the trawling of SA, is diagnosed on the basis of tidal modeling. It is found that the distribution of SA, captured by 16 tows of bottom trawling, is dependent on the BotDIV field. Basically, large (small) quantity of algae are caught at the sites where bottom currents converge (diverge). The influences of advective or diffusive process on the distribution of such heavy seaweeds settling on the seabed are probably limited.

Tidally induced upwelling off Yangtze River estuary and in Zhejiang coastal waters in summer

MASNUM wave-tide-circulation coupled numerical model (MASNUM coupled model, hereinafter) is developed based on the Princeton Ocean Model (POM). Both POM and MASNUM coupled model are applied in the numerical simulation of the upwelling off Yangtze River estuary and in Zhejiang coastal waters in summer. The upwelling mechanisms are analyzed from the viewpoint of tide, and a new mechanism is proposed. The study suggests that the tidally inducing mechanism of the upwelling includes two dynamic aspects: the barotropic and the baroclinic process. On the one hand, the residual currents induced by barotropic tides converge near the seabed, and upwelling is generated to maintain mass conservation. The climbing of the residual currents along the sea bottom slope also contributes to the upwelling. On the other hand, tidal mixing plays a very important role in inducing the upwelling in the baroclinic sea circumstances. Strong tidal mixing leads to conspicuous front in the coastal waters. The considerable horizontal density gradient across the front elicits a secondary circulation clinging to the tidal front, and the upwelling branch appears near the frontal zone. Numerical experiments are designed to determine the importance of tide in inducing the upwelling. The results indicate that tide is a key and dominant inducement of the upwelling. Experiments also show that coupling calculation of the four main tidal constituents (M2, S2, K1, and O1), rather than dealing with the single M2 constituent, improves the modeling precision of the barotropic tide-induced upwelling.

Variability of stable isotope signatures ( δ13C and δ15N) in two spider crab populations ( Maja brachydactyla) in Western Europe

The ontogenic variations of nitrogen and carbon stable isotopic signatures ( δ 15N and δ 13C) were investigated in two spider crab ( Maja brachydactyla) populations inhabiting in different biotopes of Western Europe. The Iroise Sea population is localized in Western Brittany and characterized by a seasonal migration occurring on a large bathymetric and habitat gradient while the Seine Bay population, in the Eastern English Channel, remains in a more homogeneous environment during its migration. In the Iroise Sea population, δ 13C values increased significantly both with body size and age, revealing a shift towards “benthic-component” prey with spider crab growth. On the contrary, neither body size nor ageing gave rise to a significant trophic level change (derived from the δ 15N). In this M. brachydactyla population, the seasonal migrations from coastal waters in summer to offshore habitats in winter involved significant but slight differences in both δ 13C and δ 15N. In the Seine Bay population, low variations for both carbon and nitrogen were recorded related to either sex or size or seasonal migration. Thus, the δ 13C and δ 15N variability in the spider crab depends on the availability and diversity of prey in its different living habitats, as well as on the morphological aptitudes of individuals to feed on prey (individual's size).

Belugas (&lt;i&gt;Delphinapterus leucas&lt;/i&gt;) of the Barents, Kara and Laptev seas

This paper reviews published information on the white whale or beluga (Delphinapterus leucas) inhabiting the Barents, Kara and Laptev seas. Some data obtained during multi-year aerial reconnaissance of sea ice in the Russian Arctic are also included. Ice conditions, considered one of the major factors affecting distribution of belugas, are described. The number of belugas inhabiting the Russian Arctic is unknown. Based on analysis of published and unpublished information we believe that the primary summer habitats of belugas in the Western Russian Arctic lie in the area of Frants-Josef Land, in the Kara Sea and in the western Laptev Sea. Apparently most belugas winter in the Barents Sea. Although it has been suggested that a considerable number of animals winter in the Kara Sea, there is no direct evidence for this. Apparent migrations of animals are regularly observed at several sites: the straits of the Novaya Zemlya Archipelago, the waters north of the archipelago, and Vilkitskiy Strait between the Kara and Laptev seas. Calving and mating take place in summer, and the beluga mother feeds a calf for at least a year. Females mature earlier than males, and about 30% of mature females in a population are barren. Sex ratio is apparently close to 1:1. The diet of the beluga in the region includes fish and crustaceans and shows considerable spatial and temporal variations. However, polar cod (Boreogadus saida) is the main prey most of the year, and whitefish (Coregonidae) contribute in coastal waters in summer. Usually belugas form groups of up to 10 related individuals of different ages, while large aggregations are common during seasonal migrations or in areas with abundant and easily available food. Beluga whaling in Russia has a history of several centuries. The highest catches were taken in the 1950s and 1960s, when about 1,500 animals were caught annually in the Western Russian Arctic. In the 1990s, few belugas were harvested in the Russian Arctic. In 1999 commercial whaling of belugas in Russia was banned. Belugas can be caught only for research, cultural and educational purposes and for the subsistence needs of local people. With the absence of significant whaling, anthropogenic pollution seems to be the major threat for the species.

태풍 통과에 따른 한국 연근해 수온 변동

While typhoons were passing by the coastal and offshore waters around the Korean peninsula, the variations of the sea surface temperature (SST) were studied. To study on the variation, the data related to the 22 typhoons among 346 typhoons which occurred in the western Pacific during 1990∼1999, daily measured field SSTs at coastal and offshore, and imageries from advanced very high resolution radiometer on NOAA satellite during 1990∼1999 were used. The average variations of the SSTs were -0.9℃ at coastal waters and -2℃ at offshore around the Korean peninsula while the typhoons were passing by. In very near coastal waters from the land, the SST was not changed because the bottom depth of the coastal waters was shallower than the depth of thermalcline, while the typhoon was passing. The temporal and spatial variation of SSTs at coastal waters in summer were depended on the various types of the typhoons＇paths which were passing through the Korean peninsula. When a typhoon passed by the western parts including the Yellow Sea of the Korean peninsula upwelling cold water occurred along the eastern coastal waters of the peninsula. The reason was estimated with the typhoon that was as very strong wind which blew from south toward north direction along the eastern shore of the peninsula, led to the Ekman transport from near the eastern coastal area toward the offshore. While cold water was occurring in the eastern coast, a typhoon passed over the coastal area, the cold water disappeared. The reason was estimated that the cold water was mixed up with the surrounding warm water by the effect of the typhoon. While a cold water was occurring in the eastern coast, a typhoon passed by the offshore of the eastern coast, there were the increasing of the SST as well as the disappearing of the cold water. While a typhoon was passing by the offshore of the eastern coast, the cold water which resulted from the strong tidal current in the western coast of the peninsula was horizontally spread from the onshore to the offshore. We think that the typhoon played the role of the very strong wind which was blowing from north toward south. Therefore, the Ekman transport occurred from the onshore toward the offshore of the western coast in the Korean peninsula.

Effects of Solar Radiation and Upwelling on Daily Primary Production off Oregon

Primary production was measured in units of gC m−2 day−1 (=P) and gC (gChla)−1 day−1 on a per meter squared basis (=PChl) for 4 years in Oregon coastal waters and offshore areas. P, and particularly PChl, were functions of daily photosynthetically usable radiation inshore except in summer, and offshore apparently during all seasons. Values of P and PChl for a given daily input of usable radiation were higher inshore than offshore, probably because of more efficient use of penetrating light by the relatively heavy coastal phytoplankton populations in nutrient-rich water. Evidence is presented that inshore phytoplankton populations in winter are acclimated to low light relative to inshore populations in spring.P and PChl are related to the interaction of daily radiation and degree of upwelling in Oregon coastal waters in summer. P is a function of photic depth offshore and inshore, except in summer. Probably the presence of large quantities of non-photosynthesizing detritus, even in areas of upwelling, destroys the relation in summer. There apparently is no simple relation involving daily production and certain significant environmental factors which will allow prediction of daily production in all regions of the ocean during all seasons.