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1.
To detect eddies, intensive surveys of the northeast South China Sea (SCS) (114°30′–121°30′ E, 17°–22°N) were conducted in July 1998 during the international SCS Monsoon Experiment (SCSMEX), the U.S. Navy using Airborne Expendable Bathythermograph and Conductivity-Temperature-Depth sensors (AXBT/AXCTD), and the Chinese Academy of Sciences using Acoustic Doppler Current Profilers (ADCP). The hydrographic survey included 307 AXBT and 9 AXCTD stations, distributed uniformly throughout the survey area. The ADCP survey had two sections. The velocity field inverted from the AXBT/AXCTD data and analyzed from the ADCP data confirm the existence of a low salinity, cool-core cyclonic eddy located northwest of Luzon Island (i.e., the Northwest Luzon Eddy). The radius of this eddy is approximately 150 km. The horizontal temperature gradient of the eddy increases with depth from the surface to 100 m and then decreases with depth below 100 m. The cool core was evident from the surface to 300 m depth, being 1°–2°C cooler inside the eddy than outside. The tangential velocity of the eddy is around 30–40 cm/s above 50 m and decreases with depth. At 300 m depth, it becomes less than 5 cm/s. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

2.
Intermediate Waters in the East/Japan Sea   总被引：4，自引：0，他引：4  
Properties of the intermediate layer in the East/Japan Sea are examined by using CREAMS data taken mainly in summer of 1995. Vertical profiles of potential temperature, salinity and dissolved oxygen and relationships between these physical and chemical properties show that the dissolved oxygen concentration of 250 μmol/l, roughly corresponding to 0.6°C at the depth of about 400 db, makes a boundary between intermediate and deep waters. Water colder than 0.6°C has a very stable relationship between potential temperature and salinity while salinity of the water warmer than 0.6°C is lower in the western Japan Basin than that in the eastern Japan Basin. The low salinity water with high oxygen corresponds to the East Sea Intermediate Water (ESIW; <34.06 psu, >250 μmol/l and >1.0°C) which was previously identified by Kim and Chung (1984) and the high salinity water with high oxygen found in eastern Japan Basin is named as the High Salinity Intermediate Water (HSIW; >34.07 psu, >250 μmol/l and >0.6°C). Spatial distribution of salinity and acceleration potential on the surface of σϑ = 27.2 kg/m3 shows that the ESIW prevailing in the western Japan Basin is transported eastward by a zonal flow along the polar front near 40°N and a cyclonic gyre in the eastern Japan Basin is closely related to the HSIW. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

3.
We measured potential temperature, salinity, and dissolved oxygen profiles from the surface to the bottom at two locations in the north Ross Sea (65.2°S, 174.2°E and 67.2°S, 172.7°W) in December 2004. Comparison of our data with previous results from the same region reveals an increase in potential temperature and decreases in salinity and dissolved oxygen concentration in the bottom layer (deeper than 3000 m) over the past four decades. The changes were significantly different from the analytical precisions. Detailed investigation of the temperature, salinity, dissolved oxygen and σ 3 value distributions and the bottom water flow in the north Ross Sea suggests a long-term change in water mass mixing balance. That is to say, it is speculated that the influence of cool, saline, high-oxygen bottom water (high-salinity Ross Sea Bottom Water) formed in the southwestern Ross Sea has possibly been decreased, while the influences of relatively warmer and fresher bottom water (low-salinity Ross Sea Bottom Water) and the Adélie Land Bottom Water coming from the Australia-Antarctic Basin have increased. The possible impact of global warming on ocean circulation needs much more investigation.  相似文献   

4.
The distributions of CFC (chlorofluorocarbon) in the water column was determined twice in 2000 and 2001 in the northwestern Japan Sea. In 2000 the CFC-11 concentration decreased almost exponentially with depth from 6 pmol/kg at a few hundred m deep to 0.3 pmol/kg or less at the bottom of about 3400 m depth at three stations (40–41°N, 132–133°E) about 300 km off Vladivostok. In 2001 the CFC-11 concentration increased sharply up to 2 pmol/kg in the bottom water, while it did not increase at a station (42.0°N, 136.5°E) about 450 km away to the northeast. This is due to the renewal of the bottom water which is replaced by the surface water flowing down along the continental slope, as suggested by Tsunogai et al. (1999), who proposed the continental shelf pump. Furthermore, an increase in the CFC-11 concentration was observed throughout the entire water column above 3000 m depth, although the proportion of the increase was about 20%, which was one order of magnitude smaller than that in the bottom water. The increase in inventory is almost four times larger than that in the bottom water below 3000 m depth which is equivalent to about 1/6 of the total inventory found in 2000. The increase also means that 3% of the deep water was replaced by the recent surface water, or, if the turnover occurs every year, that the turnover time of the deep water to be about 30 years. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

5.
In 1995 and 2000, the radiocarbon ratio (Δ14C) of total dissolved inorganic carbon was measured in the Japan Sea where deep and bottom waters are formed within the sea itself. We found that (1) since 1979, the Δ14C in bottom water below about 2000-m depth in the western Japan Basin (WJB) had increased by about 30‰ by 1995, and (2) the bottom Δ14C in the WJB did not change between 1995 and 2000. The former finding was due to penetration of surface bomb-produced radiocarbon into the bottom water owing to bottom ventilation, whereas the latter was caused by stagnation of the bottom ventilation there. In the eastern Japan Basin (EJB), the bottom Δ14C also increased by about 30‰ between 1979 and 2002. Recent stagnation of the bottom ventilation in the EJB is also suggested from analyses of constant bomb-produced tritium between 1984 and 1999. The temporal variations of Δ14C, tritium, and dissolved oxygen in the bottom waters indicate that: (1) new bottom water is formed south of Vladivostok in the WJB only in severe winters; and (2) the new bottom water then follows the path of a cyclonic abyssal circulation of the Japan Sea, which results in the increases in dissolved oxygen and the transient tracers in the bottom waters in the EJB and Yamato Basin with an approximate 3-to 6-year time lag. This process is consistent with the spatial variations of Δ14C, bomb-produced 137Cs, and chlorofluorocarbon-11 in the bottom waters of the Japan Sea.  相似文献   

6.
Water masses in the subsurface and the intermediate layer are actively formed due to strong winter convection in the Japan Sea. It is probable that some fraction of pollution is carried into the layer below the sea surface together with these water masses, so it is important to estimate the formation rate and turnover time of water masses to study the fate of pollutants. The present study estimates the annual formation rate and the turnover time of water masses using a three-dimensional ocean circulation model and a particle chasing method. The total annual formation rate of water masses below the sea surface amounted to about 3.53 ± 0.55 Sv in the Japan Sea. Regarding representative intermediate water masses, the annual formation rate of the Upper portion of the Japan Sea Proper Water (UJSPW) and the Japan Sea Intermediate Water (JSIW) were estimated to be about 0.38 ± 0.11 and 1.43 ± 0.16 Sv, respectively, although there was little evidence of the formation of deeper water masses below a depth of about 1500 m in a numerical experiment. An estimate of turnover time shows that the UJSPW and the JSIW circulate in the intermediate layer of the Japan Sea with timescales of about 22.1 and 2.2 years, respectively.  相似文献   

7.
A record of radionuclide fluxes at a deep marginal sea of the Northwest Pacific Ocean (39°40′N 132°24′ E, Japan Basin, East Sea/Sea of Japan) was obtained from analysis of a 1-year continuous collection of sediment-trap samples. The trap was placed at a depth of 2800 m, 500 m above the sea floor, and the samples were recovered at the end of one year. Concentrations of 238U, 234U, 232Th, 230Th and 228Th were measured in the trapped material. All of the radionuclide fluxes showed seasonal variations that were in phase with the variations in total particle flux, which were shown in earlier work to be closely tied to the primary production in the surface water. The formation of authigenic 238U appears to be less than in other open ocean regimes. The residence time of particulate thorium isotopes were of the order of a year, resulting in an average settling rate of a meter per day. Comparison of the measured 230Thex flux with that of the theoretical production in the overlying water column yielded about 40% surplus of 230Th, indicating that lateral advection contributes 230Th to this sampling site.  相似文献   

8.
One year records of four current meters moored at two sites off Sanriku (39°26′ N, 142°45′ E and 143°E) have been analyzed. Mean currents flowed southward to southwestward with velocity 2.5–7.8 cm s−1. The geostrophic velocity appeared to be surface-intensified, and the flows at 500 m depth have a relationship with the 100 m depth temperature distribution, suggesting the influence of the upper layer flows. At a depth of 1500 m and 2500 m, southward to southwestward flows are thought to be a part of the current flowing southward on the western flank of the Japan Trench. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

9.
Wind data from NCEP and hydrographic data obtained from August 28 to September 10, 1994 have been used to compute circulation in the northern South China Sea and near Luzon Strait using three-dimensional diagnostic models with a modified inverse method. The numerical results are as follows: the main Kuroshio is located above 400 m levels near Taiwan’s eastern coast and above 800 m levels away from it. Near Luzon Strait above 400 m levels a branch of the Kuroshio joins with a part of the northward current, which comes from an area west of Luzon’s western coast and intrudes northwestward, then it branchs into western and eastern parts near 20°30′ N. The eastern part flows northward into an area east of Taiwan, while its western part continues to intrude northwestward, flowing through an area southwest of Taiwan. Net westward intruded volume transport through longitude Section AB at 121°00′ E from 19°00′ N to 21° 43′ N is about 3.5 × 106 m3s−1 in a layer above 400 m levels. The anticyclonic eddies W1 and W3 exist above 700 m levels east of Dongsha Islands and below 200 m levels in the eastern part of the region, respectively. The circulation in the middle region is dominated mainly by a basin-scale cyclonic gyre, and consists of three cyclonic eddies. Strong upwelling occurs in the middle region. The joint effect of baroclinity and relief and interaction between wind stress and relief both are important for real forcing of flow across contours of fH −1 in effecting the circulation pattern.  相似文献   

10.
Most marginal seas in the North Pacific are fed by nutrients supported mainly by upwelling and many are undersaturated with respect to atmospheric CO2 in the surface water mainly as a result of the biological pump and winter cooling. These seas absorb CO2 at an average rate of 1.1 ± 0.3 mol C m−2yr−1 but release N2/N2O at an average rate of 0.07 ± 0.03 mol N m−2yr−1. Most of primary production, however, is regenerated on the shelves, and only less than 15% is transported to the open oceans as dissolved and particulate organic carbon (POC) with a small amount of POC deposited in the sediments. It is estimated that seawater in the marginal seas in the North Pacific alone may have taken up 1.6 ± 0.3 Gt (1015 g) of excess carbon, including 0.21 ± 0.05 Gt for the Bering Sea, 0.18 ± 0.08 Gt for the Okhotsk Sea; 0.31 ± 0.05 Gt for the Japan/East Sea; 0.07 ± 0.02 Gt for the East China and Yellow Seas; 0.80 ± 0.15 Gt for the South China Sea; and 0.015 ± 0.005 Gt for the Gulf of California. More importantly, high latitude marginal seas such as the Bering and Okhotsk Seas may act as conveyer belts in exporting 0.1 ± 0.08 Gt C anthropogenic, excess CO2 into the North Pacific Intermediate Water per year. The upward migration of calcite and aragonite saturation horizons due to the penetration of excess CO2 may also make the shelf deposits on the Bering and Okhotsk Seas more susceptible to dissolution, which would then neutralize excess CO2 in the near future. Further, because most nutrients come from upwelling, increased water consumption on land and damming of major rivers may reduce freshwater output and the buoyancy effect on the shelves. As a result, upwelling, nutrient input and biological productivity may all be reduced in the future. As a final note, the Japan/East Sea has started to show responses to global warming. Warmer surface layer has reduced upwelling of nutrient-rich subsurface water, resulting in a decline of spring phytoplankton biomass. Less bottom water formation because of less winter cooling may lead to the disappearance of the bottom water as early as 2040. Or else, an anoxic condition may form as early as 2200 AD. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

11.
Water masses in the East Sea are newly defined based upon vertical structure and analysis of CTD data collected in 1993–1999 during Circulation Research of the East Asian Marginal Seas (CREAMS). A distinct salinity minimum layer was found at 1500 m for the first time in the East Sea, which divides the East Sea Central Water (ESCW) above the minimum layer and the East Sea Deep Water (ESDW) below the minimum layer. ESCW is characterized by a tight temperature–salinity relationship in the temperature range of 0.6–0.12 °C, occupying 400–1500 m. It is also high in dissolved oxygen, which has been increasing since 1969, unlike the decrease in the ESDW and East Sea Bottom Water (ESBW). In the eastern Japan Basin a new water with high salinity in the temperature range of 1–5 °C was found in the upper layer and named the High Salinity Intermediate Water (HSIW). The origin of the East Sea Intermediate Water (ESIW), whose characteristics were found near the Korea Strait in the southwestern part of the East Sea in 1981 [Kim, K., & Chung, J. Y. (1984) On the salinity-minimum and dissolved oxygen-maximum layer in the East Sea (Sea of Japan), In T. Ichiye (Ed.), Ocean Hydrodynamics of the Japan and East China Seas (pp. 55–65). Amsterdam: Elsevier Science Publishers], is traced by its low salinity and high dissolved oxygen in the western Japan Basin. CTD data collected in winters of 1995–1999 confirmed that the HSIW and ESIW are formed locally in the Eastern and Western Japan Basin. CREAMS CTD data reveal that overall structure and characteristics of water masses in the East Sea are as complicated as those of the open oceans, where minute variations of salinity in deep waters are carefully magnified to the limit of CTD resolution. Since the 1960s water mass characteristics in the East Sea have changed, as bottom water formation has stopped or slowed down and production of the ESCW has increased recently.  相似文献   

12.
The Arabian Sea is characterized by a mid‐depth layer of reduced dissolved oxygen (DO) concentration or oxygen minimum zone (OMZ ‐DO concentration <0.5 ml·l?1) at ~150–1000 m depth. This OMZ results from the flux of labile organic matter coupled with limited intermediate depth water ventilation. Generally, benthic animals in the OMZ have morphological and physiological adaptations that maximize oxygen uptake in the limited oxygen availability. Characteristics of OMZ benthos have been described from only a few localities in the Arabian Sea. We measured the bottom water DO and studied the characteristics of infaunal macrobenthos of the Indian western continental shelf by collecting samples at 50, 100 and 200 m in depth from 7° to 22° N. The DO values observed at 200 m (0.0005–0.24 ml·l?1) indicated that this area is lying within an OMZ. Five major taxa, namely Platyhelminthes, Sipunculoidea, Echiuroidea, Echinodermata and Cephalochordata were absent from the samples collected from this OMZ. In general, declines in total macrobenthic density and biomass and polychaete species richness and diversity were observed in this OMZ compared with the shallower depths above it. Community analyses of polychaetes revealed the dominance of species belonging to families Spionidae, Cirratulidae and Paraonidae in this OMZ. Low oxygen condition was more pronounced in the northern continental shelf edge (≤0.03 ml·l?1), where the majority of spionids including Prionospio pinnata and cirratulids were absent; whereas amphipod, isopod and bivalve communities were not impacted.  相似文献   

13.
The habitat quality of Chub mackerel (Scomber japonicus) in the East China Sea has been a subject of concern in the last 10 years due to large fluctuations in annual catches of this stock. For example, the Chinese light-purse seine fishery recorded 84000 tons in 1999 compared to 17000 tons in 2006. The fluctuations have been attributed to variability in habitat quality. The habitat suitability Index (HSI) has been widely used to describe fish habitat quality and in fishing ground forecasting. In this paper we use catch data and satellite derived environmental variables to determine habitat suitability indices for Chub mackerel during July to September in the East China Sea. More than 90% of the total catch was found to come from the areas with sea surface temperature of 28.0°–29.4°C, sea surface salinity of 33.6–34.2 psu, chlorophyll-a concentration of 0.15–0.50 mg/m3 and sea surface height anomaly of −0.1–1.1 m. Of the four conventional models of HSI, the Arithmetic Mean Model (AMM) was found to be most suitable according to Akaike Information Criterion analysis. Based on the estimation of AMM in 2004, the monthly HSIs in the waters of 123°–125°E and 27°30′–28°00′ N were more than 0.6 during July to September, which coincides with the catch distribution in the same time period. This implies that AMM can yield a reliable prediction of the Chub mackerel’s habitat in the East China Sea.  相似文献   

14.
We have measured helium isotopic ratios of thirty-seven Pacific water samples from various depths collected in adjacent regions of Honshu, Japan. The 3He/4He ratios vary significantly from 0.989 R atm to 1.208 R atm where R atm is the atmospheric ratio of 1.39 × 10−6. The mid-depth (750–1500 m) profile of 3He/4He ratios at ST-1 located Northwestern Pacific Ocean east of Japan (Off Joban; 37°00′ N, 142°40′ E) is significantly different from that at ST-2 of the Northern Philippine Sea south of Japan (Nankai Trough; 33°07′ N, 139°59′ E), suggesting that these waters were separated by a topographic barrier, the Izu-Ogasawara Ridge. Taking 3He/4He data of the Geosecs expeditions in the western North Pacific, an extensive plume of 15% excess 3He relative to the air may be traced at ST-1 over 12,000 kilometers to the northwest of the East Pacific Rise where the mantle helium may originate. The 20% excess found at ST-2 may be attributable to the additional source of the subduction-type mantle helium in the Okinawa Trough. A 15% excess of 3He has also been discovered at a depth of about 1000∼1500 m at ST-3 adjacent to Miyakejima Island (33°57′ N, 139°22′ E) and ST-4 of Sagami Bay (35°00′ N, 139°22′ E). It is confirmed that mid-depth all over the western North Pacific water is affected by the mantle helium with a high 3He/4He ratio. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

15.
The circulation of intermediate and deep waters in the Philippine Sea west of the Izu-Ogasawara-Mariana-Yap Ridge is estimated with use of an inverse model applied to the World Ocean Circulation Experiment (WOCE) Hydrographic Program data set. Above 1500 m depth, the subtropical gyre is dominant, but the circulation is split in small cells below the thermocline, causing multiple zonal inflows of intermediate waters toward the western boundary. The inflows along 20°N and 26°N carry the North Pacific Intermediate Water (NPIW) of 11 × 109 kg s−1 in total, at the density range of 26.5σθ–36.7σ2 (approximately 500–1500 m depths), 8 × 109 kg s−1 of the NPIW circulate within the subtropical gyre, whereas the rest is conveyed to the tropics and the South China Sea. The inflow south of 15°N carries the Tropical Salinity Minimum water of 35 × 109 kg s−1, nearly half of which return to the east through a narrow undercurrent at 15–17°N, and the rest is transported into the lower part of the North Equatorial Countercurrent. Below 1500 m depth, the deep circulation regime is anti-cyclonic. At the density range of 36.7σ2, – 45.845σ4 (approximately 1500–3500 m depths), deep waters of 17 × 109 kg s−1 flow northward, and three quarters of them return to the east at 16–24°N. The remainder flows further north of 24°N, then turns eastward out of the Philippine Sea, together with a small amount of subarctic-origin North Pacific Deep Water (NPDW) which enters the Philippine Sea through the gap between the Izu Ridge and Ogasawara Ridge. The full-depth structure and transportation of the Kuroshio in total and net are also examined. It is suggested that low potential vorticity of the Subtropical Mode Water is useful for distinguishing the net Kuroshio flow from recirculation flows. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

16.
A time-series sediment trap deployment was carried out in the marginal ice zone (MIZ) of the Antarctic Ocean (64°42′ S, 139°58′E; sea depth of 2930 m), during the austral summer. Cylindrical fecal pellets were the predominant sinking particles at 537 m in the middle of January and most of them disappeared below that depth, the loss of which were 25.3 mg C m−2 day−1 in the depth range of 537–796 m. Small-sized sinking particles other than fecal pellets increased in that depth range. Analyses of fecal pellets for remnant DNA corresponding to 16S mitochondrial RNA and 28S ribosomal RNA suggested that the large cylindrical fecal pellets at 537 m were produced by Antarctic krill (Euphausia superba) and copepods. According to the presence of the DNA associated with sinking particles, E. superba fecal pellets rapidly disappeared below 537 m, while copepod fecal pellets still remained in the mesopelagic and bathypelagic layers. Small-sized amorphous sinking particles at 537 m also contained E. superba- and copepod-derived DNA. The abundance of trap-collected copepods (Oithona spp. and Oncaea spp.) which are known to be coprophagous increased at 796 m where many fecal pellets disappeared. We suggest that those rapidly sinking pellets were fragmented by copepods with intensified coprorhexy activity (fragmentation of fecal pellets) in the mesopelagic layers, reducing their sinking rates. These smaller and slower sinking particles can be important food sources for detritivorus or coprophagous animals in mesopelagic and bathypelagic layers in the MIZ. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

17.
The Formation and Circulation of the Intermediate Water in the Japan Sea   总被引：1，自引：0，他引：1  
In order to clarify the formation and circulation of the Japan/East Sea Intermediate Water (JESIW) and the Upper portion of the Japan Sea Proper Water (UJSPW), numerical experiments have been carried out using a 3-D ocean circulation model. The UJSPW is formed in the region southeast off Vladivostok between 41°N and 42°N west of 136°E. Taking the coastal orography near Vladivostok into account, the formation of the UJSPW results from the deep water convection in winter which is generated by the orchestration of fresh water supplied from the Amur River and saline water from the Tsushima Warm Current under very cold conditions. The UJSPW formed is advected by the current at depth near the bottom of the convection and penetrates into the layer below the JESIW. The origin of the JESIW is the low salinity coastal water along the Russian coast originated by the fresh water from the Amur River. The coastal low salinity water is advected by the current system in the northwestern Japan Sea and penetrates into the subsurface below the Tsushima Warm Current region forming a subsurface salinity minimum layer. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

18.
本研究通过分析布放在南海北部的着陆器流速数据,研究一支蓝移的近惯性振荡信号,发现该信号可以传到600m水深以下,持续时间为11月3—16日。该信号的最大的东向流速为0.133m/s,最大南向流为0.124m/s。谱分析发现垂向流速呈现出5个不同的流核,最强流核发生在600—650m位置。近惯性能量下传速度为67±5m/d,从600m下传到1000m的位置能量耗散18%。经验正交函数(empiricalorthogonalfunction,EOF)分解结果显示,这次近惯性振荡信号开始是第一模态占主导,随后变成高阶模态为主导的形式。由于不知道其信号生成的源头,所以无法确定近惯性振荡形成原因,结合前人的研究结果,可以排除台风引起此次近惯性振荡信号的生成。卫星的海表高度异常显示,此时的正涡度有利于此次近惯性振荡发生蓝移特征。  相似文献   

19.
Concentration and stable isotopic compositions (δ 18O) of dissolved O2 were measured in seawater samples collected from the Philippine Sea in June 2006. The in-situ O2 consumption rate and the isotopic fractionation factor (α r ) during dissolved O2 consumption were obtained from field observations by applying a vertical one-dimensional advection diffusion model to the deep water mass of about 1000–4000 m. The average O2 consumption rate and α r were, respectively, 0.11 ± 0.07 μmol kg−1yr−1 and 0.990 ± 0.001. These estimated values agree well with values from earlier estimations of Pacific deep water. The in-situ O2 consumption rates are two or more times higher north of 20°N, although the value of α r was not significantly different between the north and south. Its levels varied rapidly in the water mass of less about 2000 m depth. These results suggest that organic matter from the continent imparts a meaningful contribution to the upper water in the northern part of the area; it might produce the strong O2 minimum that is evident in the water mass from about 1000–2000 m in the northern part of the Philippine Sea.  相似文献   

20.
The material was collected in the Ob River estuary and over the adjacent shallow Kara Sea shelf between 71°14′0 and 75°33′0N at the end of September 2007. Latitudinal zoning in the phytoplankton distribution was demonstrated; this zoning was determined by the changes in the salinity and concentration of nutrients. Characteristic of the phytocenosis in the southern desalinated zone composed of freshwater species of diatom and green algae were the high population density (1.5 × 106 cells/l), biomass (210 μgC/l), chlorophyll concentration (4.5 μg/l), and uniform distribution in the water column. High primary production (∼40 μgC/l/day) was recorded in the upper 1.5-m layer. The estuarine frontal zone located to the north contained a halocline at a depth of 3–5 m. Freshwater species with low population density (2.5 × 105 cells/l), biomass (24 μgC/l), and chlorophyll concentration (1.5 μg/l) dominated above the halocline. Marine diatom algae, dinoflagellates, and autotrophic flagellates formed a considerable part of the phytocenosis below the halocline; the community characteristics were twofold lower as compared with the upper layer. The maximal values of the primary production (∼10 μgC/l per day) were recorded in the upper 1.5-m layer. The phytocenosis in the seaward zone was formed by marine alga species and was considerably poorer as compared with the frontal zone. The assimilation numbers at the end of the vegetation season in the overall studied area were low, amounting to 0.4–1.0 μgC/μgChl/h in the upper layer and 0.03–0.1 μgC/μgChl/h under the pycnocline.  相似文献   

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