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1.
河北沿岸微微型浮游植物的分布特征   总被引：1，自引：0，他引：1  
于2006年7月～ 2007年10月间,分4个季度调查了河北省沿岸微微型浮游植物的丰度和生物量及对浮游植物总生物量的贡献.结果显示:河北近岸海域聚球藻蓝细菌丰度为4.46×103个/mL(0.79×103～ 16.19×103个/mL),生物量(以碳计,下同)为1.31 mg/m3 (0.84～17.47 mg/m3),季节分布特征为秋季＞冬季＞夏季＞春季.微微型光合真核生物丰度为4.43×102个/mL (0.84×102～ 17.47×102个/mL),生物量为1.11mg /m3 (0.21～ 4.37 mg/m3),季节变化变现为秋季＞冬季＞春季＞夏季.微微型浮游植物对浮游植物总生物量的贡献年平均为5.32％(1.84％～ 8.91％),春季最高,秋季最低.温度在较冷季节(冬春季)里是影响聚球藻蓝细菌生长和分布的控制因素.总之,在近岸环境里,微微型浮游植物并不占优势.  相似文献   

2.
Temporal and spatial variations in Synechococcus abundance were investigated over an annual cycle (February'10–January'11) along a salinity gradient (0–35) in the tropical Zuari estuary, influenced by south-west monsoons. Synechococcus exhibited salinity preferences with phycoerythrin-rich cells at salinities >2 (Synechococcus-PEI), >20 (Synechococcus-PEII) and <1 (Synechococcus-PEIII) whereas phycocyanin-rich (Synechococcus-PC) dominant at lower salinities. Downstream stratification during monsoon caused Synechococcus group segregation in the surface and near-bottom waters. During monsoon-break and non-monsoon period stabilized waters, increased salinity, temperature, solar radiation and low rainfall favored high Synechococcus abundance whereas unstable waters, increased turbidity and low solar radiation during active monsoon lowered abundance. SYN-PC positively co-related with nitrate and phosphate and SYN-PEI with phosphate. Synechococcus contribution to phytoplankton carbon biomass ranged from 9 to 29%. In monsoonal estuaries, rainfall intensity regulates freshwater runoff which modulates the estuarine environment, creating temporal–spatial niche segregation of Synechococcus groups thereby serving as indicator organisms of the estuarine hydrodynamics.  相似文献   

3.
Seasonal variations in the picoplankton community were investigated from June 2002 to March 2004 within the photic zone of Sagami Bay, Japan. The study area was mostly dominated by coastal waters during the warm period (mixed layer water temperature ≥ 18°C). During the cold period (mixed layer water temperature ≤ 18°C), the water mass was characterized by low temperature and high saline waters indicative of the North Pacific Subtropical Mode Water (NPSTMW). Occasionally, a third type of water mass characterized by high temperature and low saline properties was observed, which could be evidence of the intrusion of warm Kuroshio waters. Synechococcus was the dominant picophytoplankton (5−28 × 1011 cells m−2) followed by Prochlorococcus (1−5 × 1011 cells m−2) and picoeukaryotes during the warm period. Heterotrophic bacteria dominated the picoplankton community throughout the year, especially in the warm period. During the Kuroshio Current advection, cyanobacterial abundance was high whereas that of picoeukaryotes and heterotrophic bacteria was low. During the cold period, homogeneously distributed, lower picophytoplankton cell densities were observed. The dominance of Synechococcus in the warm period reflects the importance of high temperature, low salinity and high Photosynthetically Active Radiation (PAR) on its distribution. Cyanobacterial and heterotrophic bacterial abundance showed a positive correlation with temperature. Prochlorococcus and picoeukaryotes showed a positive correlation with nutrients. Picoeukaryotes were the major contributors to the picophytoplankton carbon biomass. The annual picophytoplankton contribution to the photosynthetic biomass was 32 ± 4%. These observations suggest that the environmental conditions, combined with the seasonal variability in the source of the water mass, determines the community structure of picoplankton, which contributes substantially to the phytoplankton biomass and can play a very important role in the food web dynamics of Sagami Bay.  相似文献   

4.
胶州湾微微型浮游植物丰度及其与环境因子的相关性分析   总被引：1，自引：0，他引：1  
利用流式细胞仪对胶州湾微微型浮游植物4个季节的丰度分布进行了研究,并分析了微微型浮游植物与环境因子的相关性。结果表明,聚球藻的丰度在2.17×102—2.329×104个/ml之间,高值区主要分布在湾内西部和湾口海域;仅夏季、冬季丰度之间有显著性差异;夏季在垂直分布上差异显著,在B3、C4、D5连续站昼夜变化趋势基本一致,分别在13:00和3:00出现峰值。微微型真核浮游植物的丰度分布在1.028×103—8.651×104个/ml之间,主要活跃于湾内西部海域;四季丰度在垂直分布上差异不显著;春、夏季丰度明显高于秋、冬季;夏季连续站昼夜变化趋势与聚球藻基本一致。通过主成分分析表明,聚球藻和微微型真核浮游植物丰度在不同季节受不同环境因子的影响,在冬季与温度有关,温度升高,二者的丰度增高。在其它季节,二者丰度主要受营养盐等环境因子的影响。  相似文献   

5.
春季黄海浮游植物生态分区:物种组成   总被引：3，自引：1，他引：2  
Phytoplanktonic ecological provinces of the Yellow Sea(31.20°–39.23°N, 121.00°–125.16°E) is derived in terms of species composition and hydrological factors(temperature and salinity). 173 samples were collected from 40 stations from April 28 to May 18, 2014, and a total of 185 phytoplanktonic algal species belonging to 81 genera of 7phyla were identified by Uterm?hl method. Phytoplankton abundance in surface waters is concentrated in the west coast of Korean Peninsula and Korea Bay, and communities in those areas are mainly composed of diatoms and cyanobacteria with dominant species of Cylindrotheca closterium, Synechocystis pevalekii, Chroomonas acuta,Paralia sulcata, Thalassiosira pacifica and Karenia mikimotoi, etc. The first ten dominant species of the investigation area are analyzed by multidimensional scaling(MDS) and cluster analysis, then the Yellow Sea is divided into five provinces from Province I(P-I) to Province V(P-V). P-I includes the coastal areas near southern Liaodong Peninsula, with phytoplankton abundance of 35 420×10~3–36 163×10~3 cells/L and an average of 35 791×10~3 cells/L, and 99.84% of biomass is contributed by cyanobacteria. P-II is from Shandong Peninsula to Subei coastal area. Phytoplankton abundance is in a range of 2×10~3–48×10~3 cells/L with an average of 24×10~3cells/L, and 63.69% of biomass is contributed by diatoms. P-III represents the Changjiang(Yangtze River) Diluted Water. Phytoplankton abundance is 10×10~3–37×10~3 cells/L with an average of 24×10~3 cells/L, and 73.14% of biomass is contributed by diatoms. P-IV represents the area affected by the Yellow Sea Warm Current.Phytoplankton abundance ranges from 6×10~3 to 82×10~3 cells/L with an average of 28×10~3 cells/L, and 64.17% of biomass is contributed by diatoms. P-V represents the cold water mass of northern Yellow Sea. Phytoplankton abundance is in a range of 41×10~3–8 912×10~3 cells/L with an average of 1 763×10~3 cells/L, and 89.96% of biomass is contributed by diatoms. Overall, structures of phytoplankton community in spring are quite heterogeneous in different provinces. Canonical correspondence analysis(CCA) result illustrates the relationship between dominant species and environmental factors, and demonstrates that the main environmental factors that affect phytoplankton distribution are nitrate, temperature and salinity.  相似文献   

6.
为全面了解黄海典型海区微微型浮游植物的季节变化特征,于2009年7月至2010年6月在北黄海獐子岛海域和2010年1~12月在南黄海胶州湾进行逐月调查采样,利用流式细胞仪检测了表层海水中微微型浮游植物(picophytoplankton)的丰度,包括聚球藻(Synechococcus,SYN)和微微型真核浮游植物(picoeukaryotes,PEUK),并分析了其与环境因子的关系。獐子岛海域和胶州湾SYN和PEUK全年广泛分布,獐子岛海域SYN丰度范围在0.05×103~120.00×103cells/mL之间,丰度在秋季最高;胶州湾SYN丰度范围在0.02×103~61.80×103cells/mL之间,丰度在夏季最高。獐子岛海域PEUK丰度范围在0.01×103~18.76×103cells/mL之间,丰度在秋季最高;胶州湾PEUK丰度范围在0.25×103~95.57×103 cells/mL之间,丰度在春季最高。獐子岛海域微微型浮游植物丰度组成以SYN为主;而胶州湾以PEUK为主。PEUK是两海区微微型浮游植物生物量的主要贡献者。相关性分析结果表明,温度是影响两海区SYN丰度季节变化的最主要因素;影响PEUK季节分布的因素不完全一致,獐子岛海域PEUK丰度主要受温度调控;胶州湾PEUK丰度主要受温度和营养盐浓度影响。与已有研究比较,这两个海区的微微型浮游植物生物量对浮游植物生物量的贡献明显高于其他温带沿岸海域,预示微微型浮游植物在獐子岛海域和胶州湾生态系统中的重要作用,值得进一步深入研究。  相似文献   

7.
李照  宋书群  李才文  俞志明 《海洋学报》2017,39(10):124-144
通过2013年3月和8月在长江口及其邻近海域进行的多学科综合调查,研究了枯水期和丰水期浮游植物的群落结构和空间分布特征,并探讨了影响其分布的环境因子效应。枯水期共发现浮游植物3门41属80种（不包括变种和变型）,以硅藻为主,主要优势种为具槽帕拉藻（Paralia sulcata）;浮游植物细胞丰度介于0.15×103~16.35×103 cells/L,平均值为（3.24±3.14）×103 cells/L;浮游植物细胞丰度在长江口外东北部海域形成高值,垂直变化较小,硅藻刻画了浮游植物的空间分布。丰水期共发现浮游植物4门67属135种（不包括变种和变型）,甲藻物种数量和细胞丰度均升高,主要优势种为东海原甲藻（Prorocentrum donghaiense）和骨条藻（Skeletonema sp.）;浮游植物细胞丰度介于0.2×103~1 925.45×103 cells/L,平均值为（41.67±186.00）×103 cells/L;浮游植物细胞丰度在长江口外形成南北两个高值区,随水深增加,细胞丰度逐渐降低。浮游植物的空间分布受长江口冲淡水影响,与盐度和浊度有显著的相关性;N/P比影响浮游植物群落结构,随着N/P比升高,甲藻的相对丰度升高,硅藻的相对丰度逐渐降低。浮游植物在层化水体的上层大量繁殖是底层低氧形成的必要条件,硅藻具有较高的沉降速率,因而以硅藻为主的群落更利于低氧的形成。  相似文献   

8.
南黄海夏季微微型浮游植物丰度的分布   总被引：1，自引：1，他引：0  
2008年8月中韩合作对南黄海生态系统进行了整体调查,调查站位共计37个。利用流式细胞仪测定了南黄海微微型浮游植物丰度,结合理化环境因子,分析了它们在夏季南黄海的分布特征。所测微微型真核浮游植物丰度平均值为1.9×103个/mL,最大值为2.4×104个/mL;聚球藻丰度平均值为5.3×104个/mL,最大值为5.1×105个/mL;从河口近岸到南黄海中部的宽阔海域,随着环境因子的变化,微微型浮游植物在各海区的分布明显不同,表现为河口近岸区域丰度大,离岸丰度小的特点;各站位丰度垂直分布主要趋势是上大下小,在跃层突出。根据分布趋势,聚球藻可分为两种垂直分布类型,微微型真核浮游植物分为三种。这些分布差异源于长江冲淡水和黄海冷水团的影响。  相似文献   

9.
于 2008 年 8 月 10—28 日, 在山东乳山近海赤潮发生海域采用直接采水计数法对浮游植物种类组成进行了 4 次跟踪监测。结果表明, 此次赤潮主要由海洋卡盾藻引起, 面积约 100km2, 平均密度 1.46×106 cells/L, 占浮游植物总数的 91.32%。 从 8 月 19 日开始, 海洋卡盾藻赤潮开始消退, 同时中肋骨条藻和尖刺拟菱形藻密度增高, 到 8 月 28 日本次赤潮完全消失。研究发现, 该海域富营养化、低盐度的理  相似文献   

10.
The spatial distribution of heterotrophic ciliates, environmental factors and potential food items (bacteria, Synechococcus spp. and nanoflagellates) were measured in the East China Sea to examine which variables contributed importantly to the long-term distribution of ciliates between 1998 and 2007. In July 1998 and June 2003, heterotrophic ciliates were found to be abundant (1,000–2,000 × 103 cells m−3) in regions where surface salinity <32 but extremely low (<500 × 103 cells m−3) in shelf waters of surface salinity >32. After August 2003, shortly after the completion of the Three Gorges Dam, we found no significant areal differences in the abundance of heterotrophic ciliates (HC). However, we found a significantly negative correlation between temperature and HC abundance of surface water after the completion of the dam, suggesting that temperature had a greater influence on HC abundance, once the original saline state had changed. For the long-term trends on the vertical distribution of HC, their abundance was significantly higher in the upper 50 m of the water column than at either 75 or 100 m. Abundance of Synechococcus spp. at these levels varied significantly in regions of surface salinity <32, suggesting that ciliates and picophytoplankton contribute greatly to mediating the transfer of organic matter to higher trophic levels in this marine ecosystem.  相似文献   

11.
The KwaZulu-Natal Bight is a shallow indentation of the eastern seaboard of South Africa, characterised by a narrow (45 km wide) extension of the continental shelf, with a shelf break at about 100 m. It has a complex hydrography: the waters of the bight are derived from the fast-flowing, southward-trending Agulhas Current, which is fed mostly by the tropical and subtropical surface waters of the South-West Indian Ocean subgyre, which are generally oligotrophic in nature, notably depleted in reduced nitrogen and phosphate except at river mouths and during periodic upwelling of deeper nutrient-rich water. Despite this, the bight is believed to be relatively productive, and it is suggested that efficient nutrient recycling by prokaryotes may sustain primary productivity efficiently, even in the absence of new nutrient inputs. Here we have measured bacterial numbers, biomass and heterotrophic productivity during summer and winter in conjunction with phytoplankton standing stock and factors that influence it. Bacterial distribution closely matched phytoplankton distribution in surface waters, and was highest close to the coast. Bacterial standing stocks were similar to those of oligotrophic systems elsewhere (0.5–5.0 × 105 cells ml–1; 1 × 10–8 to 1.25 × 10–7 g C ml–1) and increased in association with the development of phytoplankton blooms offshore and with inputs of allochthonous material by rivers at the coast. Heterotrophic productivity in summer was lowest in the far south and north of the bight (0.5 × 10–10 g C ml–1 h–1) but higher close to the shore, over shallow banks, and in association with increased phytoplankton abundance over the midshelf (1.0–3.5 × 10–9 g C ml–1 h–1). There were marked seasonal differences with lower bacterial standing stocks (5 × 104 to 2 × 105 cells ml–1; 4–5 × 10–9 to 1–2 × 10–8 g C ml–1) and very low bacterial productivity (4 × 10–11 to 1 × 10–10 g C ml–1 h–1) in winter, probably resulting from lowered rates of primary productivity and dissolved organic matter release as well as reduced riverine allochthonous inputs during the winter drought.  相似文献   

12.
胶州湾浮游病毒的分布研究   总被引：3，自引：1，他引：2  
运用荧光显微镜技术,对2007年6～8月胶州湾14个站点的浮游病毒丰度进行了检测,分析了病毒在不同月份的水平与垂直分布变化,发现胶州湾浮游病毒的丰度在0.48×107～22.78×107个/mL之间,平均值为(5.72±4.72)×107个/mL,7月份病毒丰度明显高于其他两个月(P0.01)。病毒呈现从湾内至湾口至湾外递减的趋势,病毒垂直分布变化不明显。病毒-细菌比率(VBR)范围为3.90～150.72,平均值42.05±28.55,处于较高水平。利用多元相关性分析发现,病毒丰度与异养细菌丰度、聚球藻蓝细菌丰度和叶绿素a含量相关,其相关系数r分别为0.605(P0.01),0.265(P0.01)和0.604(P0.05),确定系数R2分析表明,异养细菌和叶绿素a对浮游病毒丰度的影响基本相当。病毒丰度与温度、盐度无明显相关性。对VBR的分析表明,调查区域藻类病毒占总浮游病毒的比例较高;通过VBR与异养细菌丰度的负相关性分析,认为胶州湾噬菌体的宿主菌种群较单一。  相似文献   

13.
2006年冬季北黄海网采浮游植物群落结构   总被引：6，自引：1，他引：5       下载免费PDF全文
杜秀宁  刘光兴 《海洋学报》2009,31(5):132-147
根据2006年12月30日—至2007年1月17日北黄海的调查资料,对该海域浮游植物的种类组成、优势种、丰度及其分布和多样性等基本状况进行了分析。本次调查共鉴定浮游植物4门68属131种,主要以温带近岸和广布性种为主,其中硅藻有53属113种,占总种数的86.3%,甲藻有11属16种,占总种数的12.2%。浮游植物丰度平均值为88.89×104个/m3,硅藻丰度平均值为86.58×104个/m3,甲藻丰度平均值为2.28×104个/m3,硅藻丰度分布趋势决定了浮游植物丰度的分布趋势。辽宁南岸是浮游植物密集区,山东半岛北岸其次,而北黄海中部是浮游植物的稀疏区。优势种为:短角弯角藻(Eucampia zodiacus)、具槽帕拉藻(Paralia sulcata)、尖刺拟菱形藻(Pseu-do-nitzschia pungens)、密连角毛藻(Chaetoceros densus)、柔弱角毛藻(Chaetoceros debilis)、刚毛根管藻(Rhizosolenia setigera)。浮游植物群落Shannon-Weiner物种多样性指数平均值为1.80,Peilou均匀度指数平均值为0.42。与1959年1月相比,2007年1月北黄海浮游植物丰度由150.00×104个/m3降为88.89×104个/m3,下降了近41%,硅藻丰度由148.00×104个/m3降为86.58×104个/m3,而甲藻丰度由1.25×104个/m3上升为2.28×104个/m3,占浮游植物丰度的比例由0.8%上升为2.5%。主要优势种及优势属也发生了一定程度的变化,但浮游植物群落结构仍以硅藻为主、甲藻其次,浮游植物丰度总的分布格局变化不明显。  相似文献   

14.
根据2018年春、秋两季在石狮东部近岸海域进行调查所获得的数据,研究了该海域浮游植物的群落结构,并对浮游植物群落与环境因子的关系进行了相关性分析。通过春、秋两季的调查,经初步鉴定,共145种浮游植物,隶属于3门51属,种类以硅藻为主,其中硅藻122种,甲藻21种,蓝藻2种。在春季的调查中,优势种有奇异棍形藻(Bacillaria paradoxa)、密连角毛藻(Chaetoceros densus)等7种,秋季的优势种有中肋骨条藻(Skeletonema costatum)、琼氏圆筛藻(Coscinodiscus jonesianus)等5种。浮游植物细胞密度在1.81×10~4～410.65×10~4cells/m~3之间,春季明显高于秋季。春季多样性指数(H')平均值为3.24,秋季为3.31。相关性分析结果表明,影响石狮东部近岸海域浮游植物群落的主要环境因子有水温、盐度、无机氮含量和活性磷酸盐含量。  相似文献   

15.
北部湾北部海域水体异养细菌的时空分布特征研究   总被引：2，自引：1，他引：1  
贺成  徐沙  宋书群  李才文 《海洋学报》2019,41(4):94-108
为探讨环境因素对异养细菌丰度的影响，2016年9月至2017年8月通过月度航次调查对北部湾北部海域异养细菌丰度的时空分布特征进行了系统研究。结果表明，调查海区异养细菌丰度介于（2.75~56.86）×105 cell/mL，平均值为（11.01±6.31）×105 cell/mL。各季节细菌丰度从高至低依次为:夏季、春季、冬季、秋季。异养细菌丰度由近岸海域向西南深水区方向逐渐降低，在近岸浅水区垂直分布均匀，在水深大于20 m的海区出现季节性分层现象:表层细菌丰度较高，底层细菌丰度较低。主成分分析显示温度对异养细菌时空分布有重要影响，秋、冬季异养细菌丰度与温度呈显著负相关，在春、夏季呈显著正相关。细菌丰度与盐度呈显著负相关，说明海水盐度变化是细菌时空分布重要影响因素。异养细菌丰度与叶绿素a和溶解氧含量呈显著正相关，表明浮游植物初级生产过程影响了异养细菌的时空分布。在秋、冬和春3季异养细菌丰度与营养盐水平呈显著负相关，二者关系受浮游植物生物量间接影响。异养细菌时空分布差异取决于环境条件的变化，温度、盐度、叶绿素a和溶解氧含量是影响异养细菌丰度分布的主要因素。  相似文献   

16.
2013年春季崂山湾浮游植物群落及其环境控制   总被引：4，自引：0，他引：4  
2013 年春季(3、4、5 月)对崂山湾海域浮游植物群落及其理化环境进行了3 个航次的调查研究。共鉴定浮游植物40 属75 种, 硅藻是调查区主要的浮游植物类群; 浮游植物细胞丰度平均为1.27×106个/m3,3 月份的平均丰度显著高于4、5 月份(P<0.01); 优势种主要为冰河拟星杆藻(Asterionopsis glacialis)、加拉星平藻(Asteroplanus karianus)、密联角毛藻(Chaetoceros densus)和夜光藻(Noctiluca scintillans), 浮游植物群落演替明显, 由3 月份硅藻控制逐步过渡到4、5 月份硅/甲藻共同控制; 相对较低的硝酸盐水平是导致4、5 月份浮游植物丰度显著低于3 月份的主要原因; 物种–环境数据的冗余分析(RDA)结果显示, 温度、硝酸盐含量是控制崂山湾春季浮游植物分布的重要环境因子。  相似文献   

17.
The Subei Shoal is a special coastal area with complex physical oceanographic properties in the Yellow Sea. In the present study, the distribution of phytoplankton and its correlation with environmental factors were studied during spring and summer of 2012 in the Subei Shoal of the Yellow Sea. Phytoplankton species composition and abundance data were accomplished by Uterm?hl method. Diatoms represented the greatest cellular abundance during the study period. In spring, the phytoplankton cell abundance ranged from 1.59×10~3 to 269.78×10~3 cell/L with an average of 41.80×10~3 cell/L, and Skeletonema sp. and Paralia sulcata was the most dominant species. In summer, the average phytoplankton cell abundance was 72.59×10~3 cell/L with the range of 1.78×10~3 to 574.96×10~3 cell/L, and the main dominant species was Pseudo-nitzschia pungens, Skeletonema sp., Dactyliosolen fragilissima and Chaetoceros curvisetus. The results of a redundancy analysis(RDA) showed that turbidity,temperature, salinity, pH, dissolved oxygen(DO), the ratio of dissolved inorganic nitrogen to silicate and SiO_4-Si(DIN/SiO_4-Si) were the most important environmental factors controlling phytoplankton assemblages in spring or summer in the Subei Shoal of the Yellow Sea.  相似文献   

18.
夏季南黄海主要环境因子对微微型浮游生物分布影响   总被引：2，自引：1，他引：1  
利用流式细胞技术, 获取南黄海夏季微微型浮游生物丰度数据, 分析了其组成和分布规律, 并探讨了主要的影响因子。2011年夏季, 聚球藻、微微型真核藻、异养细菌在整个调查海区的平均丰度分别在1×104、1×103、1×106 cells/mL数量级上。在全调查海区, 聚球藻和微微型真核藻受温度和光照的限制明显, 主要集中分布在温跃层及其以上水层;而营养盐的限制较小, 它们的影响只有在沿岸流影响明显的西部海区才能较为明显的体现出来。结果表明在该海域浓度较高的营养盐能够促进微微型浮游生物的生长, 但不是其限制因素;异养细菌受环境因子限制较小, 即使在深海也保持着较高的丰度。  相似文献   

19.
Phytoplankton and its relationships with physical and chemical variables were analysed over a 2-year period in Hueihue and Linao Bays (southern Chile). Samples were collected on a monthly basis from May 1991 to May 1993. The growth rate of a single stock of hatchery-produced oysters (Ostrea chilensis) distributed between these two bays was also monitored monthly. The growth rate of oysters maintained at Linao Bay (site associated with a fish farm) was significantly higher, at every depth, compared with the oysters maintained at Hueihue Bay. Temperature and salinity values and their annual fluctuations were similar at both locations, presenting higher variations at the surface (1 m) due to the influence of air temperature and local precipitation than at depth. However, significant differences in phytoplankton abundance and composition were found between the two locations. The phytoplankton community was characterized by high biomass values during spring and summer, the dominance of diatoms and an inverse relationship between temperature and species diversity. However, phytoplankton cell abundance, biovolume and chlorophyll a concentration were significantly higher at Linao at every depth sampled. Cell abundance ranged between 4.49 × 104 and 7.45 × 106 cells · l?1 in Hueihue and between 6.48 × 104 and 8.71 × 106 cells ·1?1 in Linao. The influence of temperature on chlorophyll a concentration was significant except at 8 m at both locations. The instantaneous oyster growth rate was found to be positively correlated with temperature, chlorophyll a concentration and particulate organic matter at both locations. A significant negative relationship between oyster growth and amount of particulate inorganic matter was found; this confirms the important role played by seston composition in oyster growth. The demonstration of variation in oyster growth rate associated with differences in food availability between the two locations provides insight into the ecological role played by fish farms in southern Chile. The results suggest a strong link between food availability and oyster growth.  相似文献   

20.
Primary production, nutrient concentrations, phytoplankton biomass (incl. chlorophyll a) and water transparency (Secchi depth), are important indicators of eutrophication. Earlier basin-wide primary production estimates for the Baltic Sea, a shallow shelf sea, were based mainly on open-sea data, neglecting the fundamentally different conditions in the large river plumes, which might have substantially higher production. Mean values of the period 1993–1997 of nutrient concentrations (phosphate, nitrate, ammonium and silicate), phytoplankton biomass, chlorophyll a (chl a) concentration, turbidity and primary production were calculated in the plumes of the rivers Oder, Vistula and Daugava and Klaipeda Strait as well as the open waters of the Arkona Sea, Bornholm Sea, eastern Gotland Sea and the Gulf of Riga. In the plumes, these values, except for primary production, were significantly higher than in the open waters. N:P ratios in the plumes were >16 (with some exceptions in summer and autumn), indicating potential P-limitation of phytoplankton growth, whereas they were <16 in the open Baltic Proper, indicating potential N-limitation. On the basis of in situ phytoplankton primary production, phytoplankton biomass and nutrient concentrations, the large river plumes and the Gulf of Riga could be characterized as eutrophic and the outer parts of the coastal waters and the open sea as mesotrophic. Using salinity to define the border of the plumes, their mean extension was calculated by means of a circulation model. Taking into account the contribution of coastal waters, the primary production in the Baltic Proper and the Gulf of Riga was 42·6 and 4·3×106 t C yr−1, respectively. Hence, an annual phytoplankton primary production in the whole Baltic Sea was estimated at 62×106 t C yr−1. The separate consideration of the plumes had only a minor effect on the estimation of total primary production in comparison with an estimate based on open sea data only. There is evidence for a doubling of primary production in the last two decades. Moreover, a replacement of diatoms by dinoflagellates during the spring bloom was noticed in the open sea but not in the coastal waters. A scheme for trophic classification of the Baltic Sea, based on phytoplankton primary production and biomass, chl a and nutrient concentrations, is proposed.  相似文献   

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