Shallow-water Stations Research Articles

Estimation of a five-parameter JONSWAP spectra with an improved particle swarm optimization

An improved particle swarm optimization (PSO) algorithm is presented to estimate a five-parameter JONSWAP spectrum for modeling of certain wave states, including normal events and extreme events at deep-water and shallow-water stations, respectively. The choices of spectral parameters (energy scale coefficient α, peak enhancement coefficient γ, and shape parameter σ) through vast amounts of in situ observations and spectral nonlinear factors are of significant importance for safety of marine structures and activities. Several experiments are carried out for five JONSWAP spectral parameters (α, γa, γb, σa, and σb) using relatively unimpaired and long series significant wave height, dominant wave period, average wave period, maximal spectral value, and ratio of dominant period and average period. And the choices of γ from γa and γb, as well as σ from σa and σb depend on the relationships between current frequency and the peak frequency. Two improvements of PSO algorithm are made, one is the fitness function, another is that the population average replacing particle’s individual optimum in the updating step. Well fitted spectra and statistic results show that the improved PSO model is more suitable to be applied to estimate the wave spectrum at a given record time. This heuristic model can be used without restrictions of water depth and sea state with its intuitive background, easy-programming and portable feature.

Seasonal Response of Major Phytoplankton Groups to Environmental Variables along the Campeche Coast, Southern Gulf of Mexico

To describe the seasonal response of the major phytoplankton groups to environmental variables along the Campeche coast, southeastern Gulf of Mexico, seven shallow-water (ca. 1 m) stations were monitored from January 2019 to January 2020. Orthophosphate, ammonium, nitrite, nitrate and silicate were measured. Several tests, including ANOVA, the Kolmogorov–Smirnov test, Tukey TSD, Bartlett’s test and canonical correspondence analysis (CCA), were applied. The physicochemical variables (temperature, salinity and pH) recorded are typical for the central coast of Campeche. Seasonal characteristics are affected by the shallowness of the study area. The variation of inorganic nutrient concentrations is likely to be related to specific polluting activities. While the abundance of phytoplankton presented a minimum value of 4.1 × 104 cells L−1 in March, the maximum value of 8.8 × 106 cells L−1 occurred in May; the general average was 5.3 × 105 cells L−1. Based on CCA, the correlation between major phytoplankton groups and physical–chemical variables was high (r ≈ 0.8), indicating a significant relationship. The CCA graphs separated the samples of diatoms by higher values of pH and silicate and separated the samples of cyanobacteria with high values of temperature (>30 °C) from the samples with dinoflagellates and nanoflagellates. Nanoflagellates were abundant in the samples with high values of ammonium and phosphate.

Современное состояние зоопланктона Малого Моря оз. Байкал (по данным 2022 г.)

Original results of studies of zooplankton in the Maloe More Strait of Lake Baikal in 2022 are presented. Changes in species composition, quantitative indicators of development and the structure of zooplankton in years of different water levels are analyzed. Zooplankton was collected on 5 transects in three depth zones: central about 200 m, coastal – about 10 m, shallow – less than 1 m. At deep-water stations, zooplankton includes 5 species of Rotifera and Cladocera, 2 species of Copepoda and 1 species of Amphipoda. Epischura baikalensis and Cyclops kolensis formed the basis (up to 99% of the total number) of the total population density (up to 2100 ind./m3 ) and biomass (up to 140 mg/m3). Macrohectopus branickii may also constitute a significant portion of the biomass at some stations. Coastal zooplankton is characterized by an increase in taxonomic diversity to 28 species, of which 79% are Rotifera. The population density increases to 115 thousand ind./m3 and biomass to 492 mg/m3, but the structure of zooplankton does not change due to the preservation of the dominant complex of Copepoda. A fundamentally different planktocenosis is formed at shallowwater stations, the taxonomic composition of which includes the same species as in deeper-water zones. However, non-endemic rotifers Synchaeta spp., Keratella cochlearis tecta, Polyarthra dolichoptera and others, which together make up more than 96% of the total number, become systemforming species. Of the endemic species, only the meiobenthic phytophilic crustaceans Chydorus baicalensis and Alona setosocaudata, as well as the rotifers Euchlanis ligulata, Dicranophorus sp., play some role. Zooplankton in the shallow water zone is characterized by a high abundance of up to 425 thousand ind./m3, however, taking into account the dominance of small-sized rotifers, a relatively low biomass – up to a maximum of 154.9 mg/m3. The structure and density of the population of plankton in the deep-water and coastal zones of the transects shows similarity with the zooplankton of the average water level in 2012. The taxonomic composition and quantitative characteristics of the shallow zone correspond to the zooplankton of the most warmed bays of the Maloe More Strait.

Temporal variations of phytoplankton community and their correlation with environmental factors in the coastal waters of the Çanakkale Strait in 2018

In order to investigate temporal variations in phytoplankton connected with hydrography, high-resolution (twice a week) samplings were carried out between January and December 2018 at a single, shallow water station in the Dardanelles. Diatoms dominated in early and mid-winter, late spring and early summer, and between August and October. Whereas dinoflagellates dominated in the period from mid-February to the end of the third week of May, mid-summer, and late autumn. Other groups were generally more abundant in the early summer and mid-autumn than any other period. Late spring and early summer, mid-autumn and middle winter were the important bloom periods. The average contribution of diatom abundance (5.00 × 105±7.80 × 105 cells L−1) to average total phytoplankton abundance (9.63 × 105±7.88 × 105 cells L−1) was above 50% (average: 51.88%) during the year except spring (34.32%). However, the average contribution of dinoflagellates (43.32±20.69%) and others (4.81±6.99%) to the total phytoplankton abundance were lower than the abundance of the diatoms (51.88±21.61%). The study revealed a decrease both in the total number of algal blooms which also included HABs and their densities in the region compared to the previous findings. These observations seem to evidence environmental status improvement of the investigated area, manifested in an average chlorophyll a concentration (0.71±0.52 µg L−1) and quantitative phytoplankton structure (103 to 105 cells L−1).

Vertical Distribution of Phosphates in the Black Sea Based on the Expeditionary Data, 2016–2019

Purpose. The purpose of the study is to analyze the features of vertical distribution of phosphates and dissolved organic phosphorus (Porg) in the Black Sea at the present period. Methods and Results. The data obtained by the scientists of Marine Hydrophysical Institute in the Black Sea within the economic zone of Russia in 2016–2019 were used. At more than 200 deep-sea stations, a cassette of 12 bathometers (the Seabird-Electronics STD-instrument) was applied for taking hydrochemical samples at certain isopycnic surfaces, usually at σt = 16.30; 16.25; 16.20; 16.20; 16.15; 16.10; 16.05; 16.00; 15.95; 15.90; 15.80; 15.50, 14.0 kg/m3. At the coastal shallow-water stations, samples were taken at the 10 m intervals. Such a scheme permitted to carry out vertical sampling in the upper mixed layer and in the suboxic zone (including its upper boundary) with possible minimum of phosphates, to determine the depth of hydrogen sulfide formation and the location of the phosphates concentration maximum in the upper part of the anaerobic zone. Conclusions. From the surface to isopycn σt = 14.4 kg/m3, the content of phosphates and Porg does not exceed 0.1 µM; below this isopycnic surface, the phosphates concentration begins to increase, whereas of Porg remains at the same level. At all the profiles of the phosphates vertical distribution, the phosphates concentration minimum was recorded near the isopycnic surface σt = 15.8 kg/m3, and its maximum – near the isopycnic surface σt = 16.2 kg/m3. The minimum content of phosphates varied within 0–1.5 µM; in 2016–2017 the phosphates concentration maximum did not exceed 8 µM; in 2018, in many cases, it was higher than 12 µM, and once, near the Kerch Strait, it exceeded 17 µM. Increase in the magnitude of the maximum phosphates concentration (in the previous studies in 1988–2013, it did not exceed 8 µM) is assumed to be related to installation of the supports for constructing the Kerch Bridge.

Vertikal'noye raspredeleniye form fosfora v Chernom more po ekspeditsionnym dannym 2016–2019 godov

Purpose. The purpose of the study is to analyze the features of vertical distribution of phosphates and dissolved organic phosphorus (Porg) in the Black Sea at the present period. Methods and Results. The data obtained by the scientists of Marine Hydrophysical Institute in the Black Sea within the economic zone of Russia in 2016–2019 were used. At more than 200 deep-sea stations, a cassette of 12 bathometers (the Seabird-Electronics STD-instrument) was applied for taking hydrochemical samples at certain isopycnic surfaces, usually at σt = 16.30; 16.25; 16.20; 16.20; 16.15; 16.10; 16.05; 16.00; 15.95; 15.90; 15.80; 15.50, 14.0 kg/m3. At the coastal shallow-water stations, samples were taken at the 10 m intervals. Such a scheme permitted to carry out vertical sampling in the upper mixed layer and in the suboxic zone (including its upper boundary) with possible minimum of phosphates, to determine the depth of hydrogen sulfide formation and the location of the phosphates concentration maximum in the upper part of the anaerobic zone. Conclusions. From the surface to isopycn σt = 14.4 kg/m3, the content of phosphates and Porg does not exceed 0.1 µM; below this isopycnic surface, the phosphates concentration begins to increase, whereas of Porg remains at the same level. At all the profiles of the phosphates vertical distribution, the phosphates concentration minimum was recorded near the isopycnic surface σt = 15.8 kg/m3, and its maximum – near the isopycnic surface σt = 16.2 kg/m3. The minimum content of phosphates varied within 0–1.5 µM; in 2016–2017 the phosphates concentration maximum did not exceed 8 µM; in 2018, in many cases, it was higher than 12 µM, and once, near the Kerch Strait, it exceeded 17 µM. Increase in the magnitude of the maximum phosphates concentration (in the previous studies in 1988– 2013, it did not exceed 8 µM) is assumed to be related to installation of the supports for constructing the Kerch Bridge.

Polychaetes (Annelida: Polychaeta) of the Kara Sea

As a result of processing materials from the expeditions of the Saint-Petersburg State University in 2012–2013 and the Transarctic expedition of 2019, 131 polychaete taxa were recorded, of which 124 were identified to species. On the basis of data from previous and recent collections, the general list of polychaetes in the Kara Sea was updated; it includes 209 species belonging to 98 genera, 37 families, and 15 orders. The following species are reported for the first time from the sea: Abyssoninoe hibernica (McIntosh, 1903), Ampharete falcata Eliason, 1955, Brada rugosa Hansen, 1882, Microclymene acirrata Arwidsson, 1906; Nephtys pente Rainer, 1984; Ophelina abranchiata Stop-Bowitz, 1948, Scolelepis burkovskii Sikorski, 1994, and Travisia forbesii Johnson, 1840. Polychaetes were found at all stations; the number of species per station ranged from 1 to 28. Shannon’s indices (H'SpA and H'spB) showed that at most stations the diversity of species was high and resistance to stress (DE') was quite satisfactory. Only in a few cases some tension existed in the ecological situation, estimated by the index of difference in evenness and this applies, to an overwhelming degree, to the shallow water stations in the area of the outlet from the Ob and Yenisei bays. New data show a more pronounced Arctic character of the Kara Sea fauna in comparison with the polychaete fauna of neighboring seas. The influence of the Pacific and Atlantic oceans both on the polychaete fauna of the Kara Sea and on the polychaete fauna of the neighboring seas is noticeable and natural, which is confirmed by changes in the proportion of species of Pacific and Atlantic origin. The trophic structure of polychaetes is represented by four main groups; the distribution of trophic groups is closely related to environmental conditions.

Winter Zooplankton in a Small Arctic Lake: Abundance and Vertical Distribution

Zooplankton assemblages are of great importance in aquatic food webs because they link lower (microplankton) and higher trophic levels (top predators). Small water bodies in the Arctic regions of Russia are less studied in winter because of severe ice conditions. For this reason, we analyzed the winter zooplankton community in Lake Kulonga (western coast of Kola Bay, Barents Sea). A total of 9 taxa were found in the samples. The total abundance varied from 200 to 1320 ind. m−3, averaging 705 ind. m−3. The total zooplankton biomass was 1.8–72.8 mg of wet mass m−3 with an average of 30 mg m−3. These parameters were lower than in other Russian Arctic and sub-arctic lakes in summer. Old copepodites of Cyclops spp. dominated the zooplankton community at deep-water stations in terms of the total abundance consisting of 24–33%. The copepod Macrocyclops albidus prevailed in terms of the total zooplankton biomass comprising 30–33% at deep-water stations while Cyclops scutifer and copepodites Cyclops spp. had the highest biomass at shallow water stations. Vertical distribution demonstrated different patterns at neighboring stations, probably as a result of differences in the density of fish predators.

Growth and longevity in surfclams east of Nantucket: Range expansion in response to the post-2000 warming of the North Atlantic

The Atlantic surfclam, Spisula solidissima, is distinguished by a well-documented shift in range that accelerated in the 2000s as the northwest Atlantic warmed. Here the extension of the Atlantic surfclam into heretofore Acadian Province waters off the island of Nantucket is documented and compared to the distribution of surfclam shell as an indicator of recent colonization, to the timing of range expansion, and to the physiological implications of a range extension into deeper water. The primary demographic difference observed is the dichotomous distribution of sizes. Smaller surfclams averaged higher in abundance at the deeper offshore sites, whereat the number of large animals was distinctly fewer; thus, the size-frequency distributions at deeper sites were shifted towards the smaller sizes, a finding consistent with the expectation of recruitment into deeper water during a period of range expansion. In confirmation, deeper-water stations where surfclams were aged yielded surfclams no older than 13 yr, whereas shallow-water stations had a mature age frequency with some surfclams exceeding 20 yr. Further support for the more recent occupation of deeper-water sites comes from the distribution of surfclam shell, that was found in limited quantities at stations where recent colonization is inferred and in greater quantities in shallower water where longer-term occupation is surmised. For the shallower-water sites with a mature demographic, growth rates were comparable or higher than observed elsewhere in the stock and surfclam maximum sizes were larger than elsewhere in the geographic range. In contrast, surfclams colonizing deeper water post-2000 grew at a slower rate likely due to a lower average temperature near the deep-water range boundary. The penalty for colonization pushing the range boundary into deeper, cooler water lasted no more than 4–5 years, however, after which growth rates increased to rates typical of surfclams in shallower water. Thus, surfclams responded quickly to a period of rapid climate change in contrast to expectation from their known longevity.

Benthic Harpacticoida of the Cara sea: species composition and bathymetric distribution

Data on benthic harpacticoid copepods from the Voronin Trench (central part of the Kara Sea) are reported for the first time. Harpacticoids accounted for 1–25% of total meiofauna, their abundance varied from 6 to 102 ind/10 cm2 and decreased with depth. Totally, 42 nominal species have been found, 15 species are new for the Kara Sea, and at least eight species are new for science. Several species are first records for the Arctic waters (Cylindronannopus bispinosus, Haloschizopera clotensis, H. bathyalis, Metauntemannia pseudomagniceps, Mesocletdemus duosetosus, M. parabodini, Proameira echinipes, Cletodes tuberculatus). Ameiridae, Argestidae, Pseudotachidiidae, Miraciidae and Ectinosomatidae are the most species-rich families. Joint analysis with data on shallow-water stations (Yenisei Gulf, southern Kara Sea) revealed three assemblages occupying different habitats. The assemblage inhabiting shallow silts (20–62 m in depth) was the poorest one, the shallow sands were more species-rich, while the deepest stations (92–698 m) was the richest one. The latter assemblage had the composition of families typical for the deep-sea areas. The known fauna of the Kara Sea includes 82 harpacticoid species, most of which have been also reported from north Atlantic and/or western Arctic waters.

Benthic Harpacticoida of the Kara Sea: Species Composition and Bathymetrically Related Distribution

Data on benthic harpacticoid copepods from the Voronin Trench (central part of the Kara Sea) are reported for the first time. Harpacticoids accounted for 1–25% of total meiofauna, their abundance varied from 6 to 102 ind./10 cm2 and decreased with depth. I total, 42 nominal species have been found, 15 species are new for the Kara Sea, and at least 8 species are new for science. Several species have been recorded for Arctic waters for the first time: Cylindronannopus bispinosus, Haloschizopera clotensis, H. bathyalis, Metauntemannia pseudomagniceps, Mesocletdemus duosetosus, M. parabodini, Proameira echinipes, and Cletodes tuberculatus. The most species-rich families are Ameiridae, Argestidae, Pseudotachidiidae, Miraciidae, and Ectinosomatidae. Comparative analysis including the data obtained at shallow-water stations from the Yenisei Gulf (southern Kara Sea) revealed three assemblages occupying different habitats. The assemblage inhabiting shallow-water silts (20–62-m depth) was the poorest in regard to species diversity; shallow-water sands were richer in species number, while the deepest stations (92–698 m) were the richest. The latter assemblage had the composition of families typical for the deep-sea areas. The fauna of the Kara Sea includes by now 82 harpacticoid species, most of which have been also reported from North Atlantic and/or western Arctic waters.

Vertical Structure of the Water Column at the Virgin Islands Shelf Break and Trough

The steep US Virgin Islands Shelf Break (VISB) and the Virgin Islands Trough (VIT) at the Northeastern Caribbean Sea comprise a dynamic region of the Atlantic Ocean. In situ oceanographic data collected in the region during April 2017 were used to examine the spatial variability in temperature, density, salinity, and relative Chlorophyll-a. Analysis of data from the upper 300 m of the water column, that include deep and shallow water stations in the shelf break region, shows strong stratification of the water column. Stations shallower than 800 m along the shelf break are more variable in temperature, density, and salinity than those that are deeper than 800 m along the trough. For shallow stations, the mixed layer depth deepens along-shelf from West to East while at the deep stations the opposite occurs. Salinity maxima exhibit more variability in depth and range of values in the shallow stations compared to deep stations. Six different types of water masses that contribute to the strong stratification in the region were identified in our study: Caribbean Surface Water, Subtropical Underwater, Sargasso Sea Water, Tropical Atlantic Central Water, Antarctic Intermediate Water, and North Atlantic Deep Water. The upper level Caribbean Surface Water, Subtropical Underwater, and Sargasso Sea Water are present in shallow stations, indicating potential meridional intrusions from the VIT to the VISB which may not be resolved by current ocean circulation models and are not captured in satellite data. The analysis presented here indicates that competing physical processes may be controlling the vertical structure of the water column in the region and merit further examination.

Spectral Wave Modeling in Very Shallow Water at Southern Coast of Caspian Sea

This study evaluates the capability of the Simulating WAves Nearshore (SWAN) wave model (version 41.01) in predicting significant wave height and spectral peak energy content for swell waves in very shallow water of surf zone during depth-induced wave breaking and dissipation. The model results were compared with field measurements at five nearshore stations. The results demonstrated that some breaker index formulations were successful for significant wave height prediction in surf zones. However, an incorrect shape of the energy spectrum and overestimated near spectral peak energy content at shallow water stations were obtained using all of the embedded depth-induced wave breaking formulations in SWAN. The dependent breaker index on relative depth (Kpd) formulation, which was successful in predicting near spectral peak energy content, resulted in an average error of 30%. Finally, this formulation was modified to enhance the model performance in reproducing the spectral peak energy content.

Polychaetes from the northern part of the Sea of Marmara with the description of a new species of Polydora (Annelida: Polychaeta: Spionidae)

Soft-bottom material collected from the northern part of the Sea of Marmara (off Küçükçekmece) included a total of 67 species belonging to 24 polychaete families. Three species (Brania pusilla, Lysidice cf. margaritacea and Sabellaria spinulosa) are new records for the Sea of Marmara. Three alien species (Polydora cornuta, Prionospio pulchra and Pseudopolydora paucibranchiata) were found at the shallow-water stations. Different polychaete assemblages occurred in the area and the mud percentage of sediment and salinity were the main factors related to their distribution. A new Polydora species, which is mainly characterized in having brownish pigmentation solely on the antero-dorsal sides of the body, and falcate major spines with only a bulge (anterior ones) or with a bulge and a small tooth, is described.

PLANKTON OF UST-KURA REGION OF THE CASPIAN SEA

Abstract. Plankton of Ust-Kura region of the Caspian Sea is studied in 2009–2011. Forty-eight species of planktonic ciliates, 17 species of Cladocera, 3 species of rotifers and 2 species of copepods are registered during the studies. Species diver-sity of all groups strongly influences the Kura River defining seawater desalination this site. The vast majority of species of plank-ton community refers to freshwater representatives or eurybiontic species able to exist in a wide range of salinity. Methods. Collected samples for evaluation were examined diatomaceous plankton partially invivo, and then fixed with 4% formalin with addition of dye Benqalrose. Further processing of the samples was carried out under laboratory conditions. Results. During the study 43 species of ciliates, 3 species of rotifers, 17 species of Cladocera and 2 species of cope-pods and their larval stages was noted (Table 1) . As seen from Table 1, the distribution of planktonic ciliates to collection points was fairly even and ranged from a minimum number of species reported by Article 1 (22 species) to a maximum at station 5 (31 species). It should also be noted that the vast majority mentioned in plankton ciliates are typical planktontam is distributed fairly evenly throughout the studied waters. Random plankton species, such as representatives of Condylostoma and Amphisiella were marked in shallow water stations 4 and 5. Apparently their presence in the samples is due to the temporary transfer of ben-thic plankton under the influence of the wave factor. Ключевые слова

Pycnogonida from the Bellingshausen and Amundsen seas: taxonomy and biodiversity

The Bellingshausen and Amundsen Seas are among the least studied Antarctic areas. Pycnogonids constitute a common and conspicuous component of the Antarctic marine fauna. Antarctic pycnogonids have been widely studied and are usually more abundant than elsewhere. Therefore, they represent a key taxon to understand the zoogeographic and bathymetric distributions of the fauna from these two poorly sampled seas. Furthermore, we aim to compare the diversity and composition of the pycnogonids in these areas with those in other Antarctic zones. Three main surveys were carried out in these regions (Bentart 2003 and 2006 and Biopearl II 2008). In total, 879 pycnogonids belonging to 65 species were recorded in 49 stations. Two new species are described: Heteronymphon krappi n.sp. and Nymphon nakamurai n.sp. Ammothea magniceps and A. hesperidensis are recorded for the second time in the Antarctic. The most abundant family is the Nymphonidae (60.5 %), and Nymphon australe is the most abundant species (25.5 %). The biogeographic analysis revealed 39 species in the Bellingshausen Sea (16 new records) and 19 species in the Amundsen Sea (18 new records). The circumpolar pattern is the most common found. The Bellingshausen Sea seems to be a poor area in terms of abundance and species richness compared to the Amundsen Sea and other Antarctic zones. Faunal similarity was clustered into three main groups: the shallow-water stations, the outer continental shelf stations and the slope stations. The abundance of individuals likely responds to the varying amount of organic matter that reaches each bathymetric zone.

Abundance and distribution of meiofauna in the Chukchi Sea

The metazoan meiofauna in the Chukchi Sea were collected from seven shallow water stations (depths ranging 46 to 52 m) and five deep sea stations (depths ranging between 393 and 2 300 m) during the 4th Chinese National Arctic Research Expedition in 2010. The results showed that abundance of meiofauna was higher in shallow water sediments (average of 2 445 ind./(10 cm2)) than in deep sea sediments (407.06 ind./(10 cm2)). A UNIANOVA test for difference between the two different regions was highly significant (F=101.15, p<0.01). Nematodes were numerically dominant, representing (96.6±4.6)% of the total meiofaunal abundance at the shallow water stations and (98.90±1.42)% at deep sea stations. The number of higher taxonomic groups and abundance of meiofauna were higher at Stas CC1, CC4, and R06 near the Bering Strait and the continent, than at the rest of the shallow water and deep sea stations. The primary factors causing the differences were concentrations of nutrients P and Si of bottom seawater (R=0.831, p<0.003), followed by depth (R=−0.655, p<0.05) and sand fractions of sediments (R=0.632, p <0.05). The numbers of meiofauna on the 65 μm and 32 μm sieves were significantly higher than those on the rest of the screens. Differences in numbers of meiofauna retained on screens with different mesh openings were highly significant among all sampling stations (F=31.60, p<0.01). The highest numbers of individuals on screens with 32 μm mesh openings were found at deep sea stations. The number of meiofauna in the top 0–1, 1–2, and 2–4 cm segments constituted 84.4% of the total and was significantly higher than those in the bottom 4–6 and 6–10 cm segments (F=15, p<0.01).

2. The main characteristics of the habitat

Habitat parameters were investigated in 14–22 June 2011 and in 12–24 July 2012. The comparison of the main hydrochemical parameters in the INPP pre-operational and post-operational periods shows a significant reduction in dissolved oxygen content in the lake profundal zone and in bottom layers at shallow-water stations, which was not observed in the plant pre-operational period. Such low oxygen content has a negative impact on the lake fauna, and the transformation of matter and energy in the lake ecosystem in general. Based on the hydrochemical parameters studied, it can be concluded that the trophic status of the lake has not changed.

夏、冬季南海北部浮游植物群落特征

Two cruises were carried out in the northern South China Sea( 18°—23.5°N、109°—120°E) in summer( 19th July to 16thAugust,2009) and winter( 6thto 30thJanuary,2010). Phytoplankton samples were analyzed and 150 taxa belonging to 72 genera of 4 classes were identified by Utermhl method in summer samples. The cell abundance of phytoplankton ranged 0. 16—6001. 78 × 103cells / L,the average cell abundance was 26. 49 × 103cells / L,in which Bacillariophyta accounted for 25. 81 × 103cells / L. The dominant species in summer were Trichodesmium thiebautii、 Thalassionema nitzschioides、Pseudo-nitzschia delicatissima and Gymnodinium spp. etc. 168 taxa belonging to 58 genera of 4 classes were identified in winter samples,the cell abundance of phytoplankton ranged 0. 08—37. 52 × 103cells / L,the average cell abundance was 2. 69 × 103cells / L,in which Bacillariophyta abundance was 2. 49 × 103cells / L. The dominant species in winter were Thalassionema nitzschioides,Thalassionema frauenfeldii and Chaetoceros messanensis,etc. The average cell abundance of phytoplankton in the 5m layers reduced rapidly from coastal zone to open sea in summer,and ahigh abundance value of phytoplankton occurred in coastal seawaters of east of Guangdong Province and east of Hainan Provence,while a high value of phytoplankton cell abundance occurred in Pearl River Estuary and sea basin in winter. In general,phytoplankton cell abundance was lower at deep-water stations( 200m) than at shallow water stations( 200m) during this two cruises. The average cell abundance of phytoplankton in summer was higher,but species richness was lower than that in winter. The average Shannon-Wiener diversity index of phytoplankton community were 2.12 and 2.36 in this two cruises,average Pielou index were 0.79 and 0.81,respectively. Pearson Correlate Analysis of phytoplankton cell abundance with environmental factors showed that the phytoplankton cell abundance correlated negatively( in 0.01 level) to the salinity in this two cruises and negatively correlated( in 0.01 level) to phosphate concentration in winter.

Spatio-temporal distributions of zoobenthos in Mersin Bay (Levantine Sea, eastern Mediterranean) and the importance of alien species in benthic communities

Spatio-temporal variations of soft-bottom zoobenthic communites in Mersin Bay were examined at seven stations between February and October 2009. A total of 337 species were encountered, of which Polychaeta had the highest number of species (136 species), and Mollusca possessed the highest number of individuals (65% of total specimens) and biomass (59% of total biomass). The highest benthos density (max. 9760 ind. m−2) and biomass (max. 133 g m−2) were found at shallow-water stations, whereas the highest diversity index values were calculated at the deepest station. The molluscs Cerithidium diplax, Corbula gibba and Bittium reticulatum dominated the area. Changes of zoobenthic communities were spatial rather than temporal and were strongly correlated with depth and the sediment structures. A total of 40 alien species were found in the area, of which 15 species were possibly transported to the area by ships and the others were Lessepsian migrants. The most domiant alien species in the area were C. diplax, Finella pupoides, Notomastus mossambicus and Amphiodia obtecta. Alien species formed dense populations at shallow water stations, and accounted for 12% of total number of species and 31% of total number of individuals in the area. The community parameters estimated for alien species significantly differed among stations but not among sampling periods. The main factors negatively affecting the number of alien species and individuals were depth, the clay percentage and total organic carbon concentration in sediment. The number of native species and individuals in the area show moderate positive correlations with those of aliens.