[Temporal and spatial variations and driving factors of phytoplankton in Yongjiang River estuary]. / ç”¬æ±Ÿå£æµ®æ¸¸æ¤ç‰©æ—¶ç©ºåˆ†å¸ƒç‰¹å¾åŠé©±åŠ¨å› å­.

To explore the temporal and spatial variations in phytoplankton community in small estuaries, we collected surface water samples from Yongjiang River estuary during wet, normal, and dry seasons and determined the main driving factors of phytoplankton community. A total of 358 species belonging to nine phyla and 123 genera were identified in all seasons. During wet, normal, and dry seasons, species number was 276, 154 and 151, and the abundance was (170.45±225.43)×103, (51.92±30.28)×103 and (31.65±12.79)×103 cells·L-1, respectively. Diatoms dominated the phytoplankton community, and the main dominant species were Cyclotella meneghiniana, Skeletonema costatum, and Paralia sulcata. Shannon diversity and Pielou evenness indices decreased from inside mouth to outside mouth in wet season, but there was no obvious spatial difference in normal season or dry season. Results of non-metric multidimensional scaling analysis and analysis of similarities showed that phytoplankton community composition differed significantly among different regions (inside, at and outside mouth) and different seasons. In wet season, phytoplankton abundance was significantly positively correlated with temperature, dissolved inorganic nitrogen, and dissolved reactive phosphorus, but significantly negatively correlated with salinity. In normal season, phytoplankton abundance was significantly negatively correlated with temperature. In dry season, it was not significantly correlated with environmental factors. Results of redundancy analysis showed that temperature, salinity, ammonium and dissolved reactive phosphorus explained the variations in phytoplankton community by 19.5%, 11.9%, 9.4% and 8.2%, respectively. These results revealed high dominance of diatoms and the main driving factors (temperature, salinity and nutrients) of phytoplankton community in Yongjiang River estuary.

[Spatial niches of dominant zooplankton species in Sanmen Bay, Zhejiang Province of East China].

Ecological niche has close relations with inter-species competition and resources utilization, and thus, can be used as an indicator to symbolize the resources utilization capability of certain groups of related species. In this paper, the niche breadth and overlap of the dominant zooplankton species in the Sanmen Bay of Zhejiang were determined by Shannon's formula and Petraitis index, respectively, and the differentiation of the niche was studied by canonical correspondence analysis (CCA), aiming to approach the distribution features of coastal zooplankton and related affecting factors in the Bay. In the study area, some coastal species such as Zonosagitta bedoti, Centropages dorsispinatus, and brachyuran larvae had wider niche breadth than the pelagic species such as Flaccisagitta enflata and Pseudeuphausia sinica, and the species of different groups with prey-predator relation had a greater niche overlap than those of the same groups without this relation. The CCA analysis showed that the spatial distribution of the zooplankton was more affected by water temperature, salinity, and chlorophyll a content rather than nutrients. The spatial niche of the zooplankton species was correlated with their living habit, inter-species competition, and prey- predator relationship.

[Microcosm experiments on the influence of different N/P ratios on phytoplankton community growth in the East China Sea].

In the present study, a microcosm experiment was conducted in situ for 30 days, in order to investigate the effects of different N/P ratios (1N: 1P, 4N: 1P, 8N: 1P, 16N: 1P, 32N: 1P, 64N: 1P, 128N: 1P, and 256N: 1P) on phytoplankton community growth in the East China Sea. The results indicated that the species number, cell abundance, Chl-a content, specific growth rate as well as species composition of the phytoplankton community significantly varied with the N/P ratios. After 6 days of culture, the species number, cell abundance, Chl-a content and specific growth rate in the high N/P ratio groups were significantly higher than those in the low N/P ratio groups. After 30 days of culture, the cell abundance in the groups close to the Redfield ratio (8N: 1P, 16N: 1P, and 32N: 1P) was significantly higher than those in the other treatments. On the other hand, the phytoplankton community in all the treatments was observed a definite succession from diatoms to dinoflagellates during the present study. Nonetheless, the N/P ratios strongly affected the duration of dinoflagellate bloom as well as the dominated species: at the beginning of culture (0th day-12th day), the diatoms dominated the phytoplankton community; then the relative contribution of dinoflagellates to the total cell abundance exceeded diatoms in the 4N: 1P, 16N: 1P, and 32N: 1P groups on the 18th day. After that, the relative contribution of dinoflagellates exceeded diatoms ordinally in the other groups from the 24th day to 30th day. At the end of culture, the phytoplankton community was dominated by the dinoflagellates in all the groups except for the 8N: 1P, 16N: 1P, and 32N: 1P treatments.

[Spatiotemporal distribution of macrobenthic communities and its relationships with environmental factors in Sanmen Bay].

In November 2006 and in January, April, and August 2007, an investigation on the macrobenthic communities was conducted at 18 stations in Sanmen Bay to study the relationships between the macrobenthic communities and environmental factors. A total of 124 taxa were collected, including 44 species of Polychaeta, 34 species of Crustacea, 22 species of Mollusca, 11 species of Echinodermata, and 13 species of others. The species of Polychaeta and Mollusca accounted for 62.9% of the total, which constituted the main population of the communities. Aglaophamus dibranchis, Capitella capitata, and Sternaspis scutata were the dominant species in spring, Sternaspis scutata, Aglaophamus dibranchis, and Spionidae spp. were the dominant species in summer, S. scutata, C. capitata, A. dibranchis and Virgularia gustaviana were the dominant species in autumn, and A. dibranchis, S. scutata, C. capitata, and Spionidae spp. were the dominant species in winter. There was a significant difference in the average biomass and average density of the macrobenthic communities between different seasons. The annual average biomass was 17.36 g x m(-2) and the annual average density was 72 ind x m(-1). The diversity indices of the macrobenthic communities also differed significantly between different seasons. The seasonal average Shannon diversity index was from 1.53 to 1.89, seasonal average Margalef species richness index was from 2. 25 to 2. 96, and seasonal average Pielou evenness index was from 0.83 to 0.94. Canonical correspondence analysis showed that the sea water temperature, salinity, and dissolved inorganic nitrogen, and the organic matter, total nitrogen, and total phosphorus in surface sediment were the main environmental factors affecting the macrobenthic communities. Environmental variables could better explain the changes of main macrobenthic species.

[Spatial distribution patterns of heterotrophic, nitrogen, and phosphate bacteria in hypoxic zone of Yangtze River Estuary].

In August 15-28, 2009, a preliminary study was conducted on the spatial distribution characteristics of heterotrophic bacteria (HB), inorganic phosphate bacteria (IPB), organic phosphate bacteria (OPB), denitrifying bacteria (DB), and ammonifying bacteria (AB) in the hypoxic zone of Yangtze River Estuary. In the water surface, water bottom, and sediment surface of the zone, the average quantity of AB was the largest, being 307.52 x 10(4) cells x L(-1), 184.50 x 10(4) cells x L(-1), 199.97 x 10(2) cells x g(-1), followed by that of HB (87.35 x 10(4) cfu x L(-1), 86.85 x 10(4) cfu x L(-1), and 19.56 x 10(2) cfu x g(-1)), and of OPB (19.26 x 10(4) cfu x L(-1), 18.82 x 10(4) cfu x L(-1), and 19.56 x10(2) cfu x g(-1), respectively). IPB was only observed within the Yangtze Estuary, south passage of the Estuary, and Zhoushan inshore, and its average quantity in the water surface, water bottom, and sediment surface was 18.50 x 10(4) cfu x L(-1), 31.00 x 10(4) cfu x L(-1), and 7.17 x 10(2) cfu x g(-1) respectively. DB had a wide distribution, but its average quantity was low, being 3.94 x 10(4) cells x L(-1), 23.08 x 10(4) cells x L(-1), and 6.22 x 10(2) cells x g(-1) in the water surface, water bottom, and sediment surface, respectively. Salinity, NO3(-)-N, PO4(3-)-P, SiO3(2)-Si, and pH were the main factors affecting the distribution of HB, IPB, OPB, and DB in water body and sediment surface. The HB, IPB, and OPB in water bottom and sediment surface had significant positive correlation with water temperature; the HB and OPB in water bottom and the IPB in sediment surface were significantly positively correlated with dissolved oxygen (DO); while the AB in sediment surface was significantly negatively correlated with DO. Cluster analysis showed that hypoxia affected the bacterial community structure in sediment surface.

[Abundance distribution of virioplankton in Yangtze River estuary and its adjacent East China Sea in summer and winter].

An investigation was made on the abundance distribution and its variation of virioplankton in the Yangtze River estuary and its adjacent East China Sea in summer 2006 and winter 2007. The virus direct count (VDC) was quantified by fluorescent microscopy. In summer 2006, the VDC was from 2.22 x 10(6) to 9.97 x 10(7) ind x m(-1), being higher in the surface sea water of B area (122.5 degrees-123.5 degrees E); in winter 2007, the VDC was from 1.99 x 10(6) to 2.66 x 10(7) ind x mh(-1), being higher in coastal A area (120.5 degrees-122.5 degrees E) and decreased from nearshore waters to offshore waters. In summer, the VDC had close relationships with bacteriaplankton biomass and chlorophylla concentration but less relationship with nutrients concentration (P > 0.05); in winter, the VDC was closely related to bacteriaplankton biomass and nutrients concentration but less related to chlorophyll-a concentration (P > 0.05). The abundance distribution pattern of virioplankton showed significant seasonal variability, with the VDC significantly larger in summer than in winter (P < 0.01), which was mainly decided by the distribution of the viral host, and partly by the nutrients concentration in wintertime.

The chronic effects of oil pollution on marine phytoplankton in a subtropical bay, China.

To evaluate the effects of crude oil water accommodated fraction (WAF) on marine phytoplankton community, natural phytoplankton collected seasonally from the Yueqing bay were exposed to eight groups of crude oil WAF for 15 days under laboratory conditions. Chlorophyll a and cell density were measured, and species of phytoplankton were identified every 24 h to reflect the change of phytoplankton community. The results showed that (1) High concentrations (≥ 2.28 mg l(-1)) of oil pollution would greatly restrain phytoplankton growth (p<0.001), decrease chlorophyll a content and cell density, whereas low concentrations (≤ 1.21 mg l(-1)) did not restrain its growth but rather promoted the phytoplankton growth. (2) The biodiversity, evenness, and species number of phytoplankton were all significantly influenced by crude oil WAF in all seasons (p<0.001). (3) The dominant species changes were different under different pollutant concentrations in different seasons. Different species had different tolerances to the oil pollution, thus leading to abnormal succession.

[Seasonal distribution of macrozoobenthos and its relations to environmental factors in Oujiang River estuary sea area].

To evaluate the seasonal distribution of macrozoobenthos and its relations to environmental factors in Oujiang River estuary and adjacent waters, two cruise surveys were conducted in May 2006 (spring) and January 2007 (winter). A total of 65 species were collected, among which, polychaeta and mollusk were the dominant groups, Capitella capitata and Nassarius succinctus were the dominant species in spring and winter, respectively. The species number of macrozoobenthos was more in adjacent sea area than in estuary, and more in spring than in winter. The average biomass and density in the two seasons were 19.66 g x m(-2) and 131 ind x m(-2), respectively. There was a significant difference in the macrozoobenthos density between the two seasons, while less difference was observed in the biomass. The Shannon-Weiner index had significant difference between the two seasons, while Pielou eveness index, Margalef abundance index, and Simpsom dominance index had not. Water temperature and phytoplankton were the key factors affecting the macrozoobenthic taxa in spring, and water total organic carbon and dissolve oxygen were the key affecting factors in winter.

[Niche of macrozoobenthos in intertidal zone of Jiaojiang Estuary].

The niche width and niche overlap of macrozoobenthos dominant species in the intertidal zone of Jiaojiang Estuary in October 2007 were analyzed based on niche theory, and the effects of natural factors (salinity, water temperature, sediment temperature, beach width, and sediment grain size) and environmental factors (contents of oils and heavy metals) on the environmental heterogeneity as well as the relationships between selected environmental factors and quantitative distribution of various groups of macrozoobenthos were studied by using canonical correspondence analysis method. The macrozoobenthos dominant species in study area were classified into four groups, i. e., burrowing surface predator, surface grazer, subsurface filter feeder, and subsurface swallow feeder, based on their feeding types. There were great differences in the niche widths among the groups, with the maximum of 0.428 and the minimum of 0.168, which suggested that different groups had different adaptive capacity to the environmental factors. At the level of niche overlap value higher than 0.6, Macrophthalmus japonicas and M. definitus of Group 1, Lunatica gilva, Bullacta exarata, Decorifera insignis, Assiminea brevicula and Cerithidae ornate of Group 2, and Moerella iridescens, Glauconome chinensis and Potamocorbula laevis of Group 3 had a biologically significant niche overlap, indicating their similar behavior in utilizing natural feeding resources.

[Effects of residual heat and chlorine in cooling water from coastal power plant on Calanus sinicus].

According to the practical operation of coastal power plant cooling system, a simulation study was conducted on the effects of residual heat and chlorine in the cooling water on Calanus sinicus. The results showed that the thermal tolerance of C. sinicus to the cooling water was decreased with increasing exposure duration but increased with increasing acclimation temperature. When the acclimation temperature was 16 degrees C-27 degrees C, the lethal temperature of C. sinicus under thermal shock for 15, 30 and 45 min was 29.9 degrees C-31.7 degrees C, 29.4 degrees C-31.0 degrees C and 28.9 degrees C-30.3 degrees C, and that of C. sinicus continually exposed to increasing temperature for 24 and 48 h was 26.9 degrees C-28.5 degrees C and 26.4 degrees C-28.0 degrees C, respectively. When the acclimation temperature increased to a certain degree, the thermal tolerance of C. sinicus maintained at a stable level. The toxicity of residual chlorine on C. sinicus enhanced with increasing acclimation temperature, temperature increment, and exposure duration.

[Thermal tolerance of some marine copepods].

By using experimental ecological methods, the 24 hours semi-lethal temperature (24 h LT50) of typical copepods living in the coastal area of East China Sea was determined to elucidate the effects of thermal discharge from power station on the coastal ecosystem. The results indicated that different copepods at same natural acclimated temperature and specific copepod at different initial acclimated temperature had different thermal tolerance capability. The 24h LT50 of Calanus sinicus and Sinocalanus tenellus at natural acclimated temperature 13.5 degrees C was 26.9 degrees C and 25.4 degrees C, of Acartiella sinensis and Corycaeus affinis at natural acclimated temperature 14.2 degrees C was 26.7 degrees C and 30.5 degrees C, and of Centropages dorsispinatus, Paracalanus crassirostris, Acartia spinicauda and Euterpina acutifrons at natural acclimated temperature 28.0 degrees C was 34.0 degrees C, 34.3 degrees C, 35.7 degrees C and 36.0 degrees C, respectively. The 24h LT50 of S. tenellus at natural acclimated temperature 13.5 degrees C and 23.5 degrees C was 25.4 degrees C and 33.0 degrees C, respectively.