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1.
浮游纤毛虫是真核微型生物的重要类群,在浮游生态系统中发挥着重要作用。利用传统形态学与高通量测序技术相结合的方法,于2020年9月至2021年8月对莱州湾三山岛近岸浮游纤毛虫进行每月两次的调查。对环境DNA的18S rRNA基因的V4区进行高通量测序,结果显示无壳寡毛类(占纤毛虫序列丰度的40.14%)和砂壳纤毛虫(10.67%)是优势类群,并且具有明显的季节变化。无壳寡毛类在冬季序列相对丰度最高,主要由急游虫属(Strombidium)和急游虫科未定类群(Strombidiidae_X)组成;砂壳类在春夏季序列相对丰度最高,主要由砂壳目未定类群(Tintinnida_XX)和拟铃虫属(Tintinnopsis)组成。浮游纤毛虫群落的β多样性呈现显著的季节变化,而α和β多样性在站点间差异均不显著。与环境因子的RDA分析显示,总有机碳和溶解氧含量是影响纤毛虫群落结构的主要环境驱动因子。形态学方法共检获鉴定17种纤毛虫,分别隶属于7个属,其中砂壳类在多样性和检获频率上均为最优势类群。研究填补了莱州湾三山岛海域浮游纤毛虫的多样性、群落结构和季节动态研究的空白,同时为深入研究温带海湾近岸浮游纤毛虫群落的长期变化规律以及对环境因子的响应机制提供本底资料。  相似文献   

2.
Phytoplankton diversity and community composition were studied along the Schelde river–estuary–coastal zone continuum during the summer of 2003. DCA analysis indicated a gradual compositional turnover of the phytoplankton community within the estuary. GAM modelling of species response curves along the estuarine gradient was used to identify taxa that had their population maximum in the river, the coastal zone or within the estuary. Taxa that had their population maximum within the estuary did not form a homogenous community but comprised species with different salinity optima and rather restricted salinity tolerances. The observed changes in community composition along the estuarine transition zone correspond more closely to an ecocline than to an ecotone model. Despite the fact that few taxa had their population maximum at or near the salinity gradient, alpha diversity did not display a minimum around the salinity gradient. This lack of a diversity minimum within the estuary was ascribed to an important contribution of taxa of riverine or coastal origin to alpha diversity within the estuary contributed. On average 55% of the alpha diversity in the estuarine samples was due to riverine or coastal taxa. Beta diversity displayed a clear maximum around the salinity gradient. For planktonic organisms which are subject to mass effects, beta diversity is probably a better indicator for the impact of the salinity gradient on diversity in estuaries than alpha diversity.  相似文献   

3.
We collected fishes and environmental variables in three zones (upper, middle and lower) of a small open tropical estuary during flood tide. The aim was to test for differences in fish assemblages along a gradient from freshwater to marine waters and to detect any seasonal variation in fishes and environmental variables across these zones. A total of 111 species (18 in the upper, 50 in the middle and 66 in the lower estuary) were recorded, forming three distinct fish assemblages, with the family Eleotridae dominating in the upper, Gerreidae in the middle, and Sciaenidae in the lower estuary. Only two species (Geophagus brasiliensis in the upper and the middle zones, and Eucinostomus argenteus in the middle and the lower zones) composed more than 1% of the total number of individuals in more than a single zone. Short‐term (tidal) changes in salinity in the middle estuary were associated with different assemblages in the three estuarine zones, even in winter, when the differences in salinity are lowest between the middle and the lower zones. Seasonal variation in salinity was irrelevant, except in a protected sidewater lagoon in the middle estuary. Low salinity seasonal change may be related to the lack of seasonal variation in the structure of fish assemblages in all estuarine zones.  相似文献   

4.
The structure of the benthic macrofaunal assemblages of the estuarine portion of Paraguaçu River, NE, Brazil, and its relationship with surface sediment characteristics (trace metals, PAHs, nutrients and grain size) and physical variables were investigated at ten stations on two contrasting occasions, summer (dry season) and winter (rainy season). A total of 1258 individuals (632 in winter and 626 in summer) and 62 taxa representing polychaetes, crustaceans, bivalves, echinoderms, bryozoans, sponges, cnidarians and cephalochordates were collected. Benthic assemblages in the upper estuary were unlike those in the lower estuary and a clear substitution of benthic taxa along the estuary was observed. Macrofaunal invertebrates in the low salinity region, composed of coarse sediments, were dominated by tellinids, venerids (bivalves), cirolanids (isopods), cyclopoids (copepods), and nereidids (polychaetes). While the high salinity region, composed of fine sediments, were dominated by nuculids (bivalves), cirratulids (polychaetes), and by amphiurids (ophiuroids). The Paraguaçu estuarine system is not severely affected by anthropogenic activities. In the great majority of the study sites, concentrations of trace metals and PAHs in the sediments were near background values. Nutrients values were also low. We formulated new models of taxon distribution and suggested detailed studies on the effects of salinity variation and studies using functional approaches to better understand the processes causing the spatial patterns in tropical estuarine benthic assemblages.  相似文献   

5.
The seasonal dynamics of chlorophyll a and the main accessory pigments accompanied by microscopic observations on live and fixed material were investigated in the Urdaibai estuary, Spain. Fucoxanthin was the dominant pigment during the peak in chlorophyll a, with which it was strongly correlated. Concentrations of fucoxanthin (81·30 μg l−1) in the upper estuary were amongst the highest found in the literature, and were mainly associated with diatoms and symbiotic dinoflagellates. In the lower estuary, fucoxanthin showed values typical of coastal waters (<5 μg l−1) and was mainly due to diatoms and prymnesiophytes. Chlorophyllb concentration was high along the estuary, followed the same seasonal pattern as chlorophyll a, and was associated with the presence of euglenophytes, chlorophytes and prasinophytes. High values of 19′-butanoyloxyfucoxanthin were often measured, but no organisms containing this pigment were observed in live or fixed samples. Alloxanthin and peridinin were found in low concentrations which was in agreement with cell counts of cryptophytes and peridinin-containing dinoflagellates. Two main patterns of phytoplankton assemblages were observed along the estuary. In the upper segments, during the chlorophylla maximum fucoxanthin containing algae masked the other algal groups, which were relatively more abundant during or after enhanced river flows. In the lower estuary, although dominated by fucoxanthin-containing algae, the other algal groups were important all year around. In this study, the use of diagnostic pigments has provided considerable insight into the temporal and spatial dynamics of phytoplankton assemblages by detecting phytoplankton taxa generally underestimated or overlooked by microscopy.  相似文献   

6.
Nutrient surveys of the Gulf of Alaska, from 1997 through 1999, show that coastal waters of British Columbia and southern Alaska experienced nitrate depletion each spring and summer. Through the 1997–1998 El Niño, waters with less than 1 μM NO3 covered 250,000 km2 area greater than 1999. Silicate levels as low as 0.2 μM were observed in coastal waters, suggesting that diatom growth may have been nutrient limited both in 1998 and 1999. Detailed sampling off the southern coast of British Columbia revealed that 1998 nitrate levels were only half the average of that during the 1970s winter, were depleted 1 month earlier in spring and remained low throughout the summer. Satellite images show that, compared to 1997 and 1999, chlorophyll levels were much lower in the spring of 1998 throughout the coastal waters of the Gulf of Alaska. Conditions changed dramatically during the 1999 La Niña, with ocean-mixed layer depths increasing by 20 m in winter and 40 m in spring when compared to that during 1997–1998 El Niño. Winter nutrient levels increased and summer upwelling returned. Over the past several decades, a trend towards greater stratification of coastal waters appears to be affecting the supply of nutrients to the mixed layer. The effects of stratification were especially obvious during the 1998 El Niño.  相似文献   

7.
余少梅  陈伟 《台湾海峡》2012,31(2):160-165
利用2006～2007年春、夏、冬季3个航次的CTD资料分析闽江冲淡水扩展范围季节变化特征.通过分析闽江口及邻近海域温度、盐度的平面、垂直分布特征,结果表明:闽江冲淡水的扩展范围具有明显的季节变化.春季由于闽江口附近受到闽浙沿岸流的影响,冲淡水的扩展范围难以确定,但从盐度分布情况不难看到闽江口表层被盐度低于25的具有明显冲淡水特征的水体覆盖.夏季闽江口被温度高于27℃、盐度低于25的冲淡水覆盖,冲淡水前沿向东北扩展至罗源湾、三沙湾.冬季闽江径流减弱,闽江口主要受到闽浙沿岸水的影响,基本看不到闽江冲淡水的痕迹.春季、夏季闽江冲淡水明显的影响闽江口时,闽江口附近海域被25盐度等值线包围,25盐度等值线可作为闽江口明显受冲淡水影响的指征.  相似文献   

8.
基于主成分分析法的闽江口及其近岸水域水质评价   总被引：1，自引：0，他引：1  
选取2016年4月、7月和10月闽江口及其近岸水域7个调查点位的盐度、悬浮物、pH、溶解氧、化学需氧量、氮营养盐和重金属等15项监测指标数据，采取主成分分析法分析了该水域的水质，明确影响该水域水质的主要污染因子。结果表明：15项监测指标转换提取为4个主成分，解释82.153%的方差。从时间分布来看，闽江口及其近岸水域在4月份水质较差、10月份次之、7月份较好。从空间分布来看，近河口水质较差而远离河口水质较好。影响该水域污染水质的主要驱动因子是pH、COD、氮营养盐和Cd。研究结果对于进一步了解闽江口及其近岸水域水质情况具有重要意义，同时也为福建省海洋管理的科学决策提供支持。  相似文献   

9.
The abundance and variability of planktonic ciliates in the open subarctic Pacific were determined during four month-long cruises in 1987 and 1988. The ciliate community, numerically dominated by relatively small aloricate choreotrichs, was comparable in abundance to communities in a range of oceanic and neritic environments, including waters with much higher average chlorophyll concentrations. Integrated (0–80m) ciliate biomass was typically 100–200mgC m−2, although 3- to 4-fold higher levels were observed on two occasions in spring. Ciliate community biomass, in general, was dominated by large (>20μm width) individuals, although in August 1988 the biomass of smaller cells was as great or greater. The estimated grazing impact of the ciliate community averaged 20% of the primary production. On one instance in May 1988, however, a large biomass of ciliates led to an estimated grazing impact equivalent to 55% of phytoplankton production. While ciliates may be major phytoplankton grazers during sporadic ciliate “blooms”, dino- and other heterotrophic flagellates, which make up the bulk of microheterotroph biomass, must normally be of equal or greater importance as herbivores in this ocean region.  相似文献   

10.
Nutrient and chlorophyll concentrations were measured in January 1997, 1998 and 1999 in the Gulf of the Farallones, CA at locations stretching north/south from Point Reyes to Half Moon Bay, and seaward from the Golden Gate to the Farallon Islands. The cruises were all carried out during periods of high river flow, but under different climatological conditions with 1997 conditions described as relatively typical or ‘neutral/normal’, compared to the El Niño warmer water temperatures in 1998, and the cooler La Niña conditions in 1999. Near-shore sea-surface temperatures ranged from cold (9.5–10.5°C) during La Niña 1999, to average (11–13°C) during 1997 to warm (13.5–15°C) during El Niño 1998. Nutrients are supplied to the Gulf of the Farallones both from San Francisco Bay (SFB) and from oceanic sources, e.g. coastal upwelling near Point Reyes. Nutrient supplies are strongly influenced by the seasonal cycle of fall calms, with storms (commencing in January), and the spring transition to high pressure and northerly upwelling favorable winds. The major effect of El Niño and La Niña climatic conditions was to modulate the relative contribution of SFB to nutrient concentrations in the coastal waters of the Gulf of the Farallones; this was intensified during the El Niño winter and reduced during La Niña. During January 1998 (El Niño) the oceanic water was warm and had low or undetectable nitrate, that did not reach the coast. Instead, SFB dominated the supply of nutrients to the coastal waters. Additionally, these data indicate that silicate may be a good tracker of SFB water. In January, delta outflow into SFB produces low salinity, high silicate, high nitrate water that exits the bay at the Golden Gate and is advected northward along the coast. This occurred in both 1997 and 1998. However during January 1999, a La Niña, this SFB feature was reduced and the near-shore water was more characteristic of high salinity oceanic water penetrated all the way to the coast and was cold (10°C) and nutrient rich (16 μM NO3, 30 μM Si(OH)4). January chlorophyll concentrations ranged from 1–1.5 μg l−1 in all years with the highest values measured in 1999 (2.5–3 μg l−1) as a result of elevated nutrients in the area. The impact of climatic conditions on chlorophyll concentrations was not as pronounced as might be expected from the high temperatures and low nutrient concentrations measured offshore during El Niño due to the sustained supply of nutrients from the Bay supporting continued primary production.  相似文献   

11.
We describe the spatial and temporal dynamics of macrozooplankton on the southern North West Shelf (NWS) of Australia over two consecutive summers (1997/1998 and 1998/1999). Sampling was conducted using submersible light traps, deployed at the surface and at depth, along one cross-shelf transect in 1997/1998, and along two cross-shelf transects and one long-shore transect in 1998/1999. Our results revealed large inter-annual changes in macrozooplankton assemblages during the two summers. An upwelling regime associated with El Niño conditions prevailed during the first summer, resulting in high chlorophyll concentrations and an abundance of both meso- and macrozooplankton. During this time, there were distinct inshore and offshore macrozooplankton assemblages that reflected an abrupt transition from upwelling-enriched shelf waters to oligotrophic oceanic waters. In contrast, the second summer was characterised by a downwelling regime associated with La Niña conditions that resulted in low chlorophyll concentrations and decreased abundances of meso- and macrozooplankton. The lack of upwelling activity weakened horizontal gradients in macrozooplankton assemblages so that differences between surface and deep assemblages were more pronounced. Catches in light traps were dominated by hyperiid amphipods during the first summer and by the neritic euphausiid Pseudeuphausia latifrons during the second. There was little within-season change in macrozooplankton assemblages during both summers, and only weak relationships were found between the environmental parameters and the distribution of individual macrozooplankton taxa.  相似文献   

12.
The horizontal distributions of reactive silicate and zinc in the Otago Harbour, New Zealand, a shallow, vertically well-mixed estuary, have been compared. Within the harbour silicate displayed a linear salinity profile on two sampling occasions in October and early November. Consideration of the silicate budget suggested some removal of freshwater silicate in the headwaters of the estuary. Zinc concentrations, measured using state-of-the-art clean laboratory techniques were orders of magnitude lower than previously published data for coastal waters. Typical values of 5–20 ng l−1 Zn were recorded in the seaward endmember. Zinc-salinity profiles were approximately linear. Relationships between zinc and silicate concentrations for the estuarine and freshwater samples suggest a coupling between the rates of supply of these elements to the ocean and their utilisation by plankton.  相似文献   

13.
The hydrological and hydrochemical parameters of the Tumen River estuary were collected at 13 stations in May and October 2015. Vertical temperature, conductivity, dissolved oxygen, chlorophyll fluorescence, and turbidity profiles were obtained. Water was sampled from the surface and bottom layer. The water samples were analyzed for major ions, pH, salinity, concentrations of dissolved oxygen, major nutrients, dissolved organic carbon, humic matter, and δ18О and δD isotopes. This estuary is attributed to microtidal type with a flushing time of about 10 h. A phytoplakton bloom occurred in the top layer of the estuary. For surface horizons, the hydrochemical parameters show a linear correlation with salinity. In the bottom horizons, all these parameters, except for major ions and δ18О and δD isotopes, reveal substantial nonconservative behavior. The nonconservative behavior of the hydrochemical parameters in the bottom waters was mainly caused by degradation of the phytoplankton biomass at the water/sediment interface. Hypoxic conditions were established in the bottom waters of the estuary in May.  相似文献   

14.
于2009年3月对鸭绿江河口进行了10个站的浮游植物生态调查,分析了该海域浮游植物的种类组成、优势种类、群落结构以及水平分布等特征参数.本次调查共鉴定浮游植物48种,其中硅藻种类最多,达41种,甲藻其次,为6种,金藻1种.浮游植物可划分为广温类群、暖水类群和暖温类群3个生态类群,以广温类群为主.浮游植物细胞数量平均4.67×108个/m3,细胞数量自河口向外海逐渐降低.其中,中肋骨条藻(Skeletonema costatum)占据绝对优势.浮游植物群落优势种单一且优势度较大,群落结构相对简单.相关性分析表明温度和盐度是浮游植物细胞数量的主要限制性因子.浮游植物数量受鸭绿江径流的影响较大.  相似文献   

15.
New Eulerian-Lagrangian Method for Salinity Calculation   总被引：4，自引：0，他引：4  
A difference scheme in curvilinear coordinates is put forward for calculation of salinity in estuaries and coastal waters, which is based on Eulerian-Lagrangian method. It combines first-order and second-order Lagrangian interpolation to reduce numerical dispersion and oscillation. And the length of the curvilinear grid is also considered in the interpolation. Then the scheme is used in estuary, coast and ocean model, and several numerical experiments for the Yangtze Estuary and the Hangzhou Bay are conducted to test it. These experiments show that it is suitable for simulations of salinity in estuaries and coastal waters with the models using curvilinear coordinates.  相似文献   

16.
Ciliates play a curial role in energy transfer from pico-and nano-phytoplankton to mesozooplankton in marine ecosystems. In order to visualize their geographical distributions from the Java Sea to the South China Sea (6°S to 20°N), the authors investigated the ciliate abundance and species composition in surface waters during May 18 to 27 of 2010. The ciliate abundance decreased latitudinally from 3 080 ind./L (～6°S) to 40 ind./L (～3°N), and then increased to 1 180 ind./L (～16°N) at the end of the survey. A total of 22 ciliates belonging to 15 genera were identified with the tintinnids accounted for 50% (11 species); and the species number showed a same spatial change as the ciliate abundance. Moreover, the Strombidium occupied over 50% of total ciliate abundance in most stations and Mesodinium and Tintinnopsis contributed to about 18.7% and 11.4%, respectively. In particular, our results indicate that the geographical changes in ciliate abundance were positively regulated by larger nano-and micro-phytoplankton biomass, rather than smaller pico-phytoplankton in the investigated waters.  相似文献   

17.
Zooplankton assemblages were studied from January 2007 to January 2008 along the salinity gradient of the Charente estuary (France). A Lagrangian survey was performed monthly at five sampling stations defined by salinity (freshwater, 0.5, 5, 15 and 25) in order to collect zooplankton and measure the main environmental parameters (concentrations of suspended particulate matter, particulate organic carbon, chlorophyll a and phaeopigments). A combination of multivariate cluster analysis, species indicator index and canonical correspondence analysis was used to relate the spatio-temporal patterns of the zooplankton assemblages with environmental drivers. The estuary was divided into three different zones by means of environmental parameters while four zooplankton assemblages were identified along the salinity gradient. The Charente estuary appeared as one of the most turbid systems in Europe, with suspended particulate matter (SPM) concentration reaching 3.5 g l−1 in the Maximum Turbidity Zone (MTZ). Algal heterotrophy and microphytobenthos resuspension from the wide mudflats could be responsible for the relatively high chlorophyll a concentrations measured within this MTZ. Salinity and SPM affected significantly the spatial distribution of zooplankton species while temperature and river flow seemed to control their temporal variations. From a zooplanktonic viewpoint, the highly turbid Charente estuary seemed to match an “ecotone–ecocline” model: the succession of species assemblages along the salinity gradient matched the concept of ecocline while the MTZ, which is a stressful narrow area, could be considered as an ecotone. Although such ecoclinal characteristics seemed to be a general feature of estuarine biocenoses, the ecotone could be more system-specific and biological compartment-specific.  相似文献   

18.
为研究黄河入海径流变化条件下河口附近海域盐度扩散特征,以更好地保护河口海域生物资源多样性,本文以黄河下游利津水文站的长序列实测径流数据资料为基础,利用近海水动力模型FVCOM,分析径流变化对黄河口海域盐度的影响规律。结果表明：黄河口与莱州湾之间存在顺时针的环流系统,在余流作用以及涨落潮方向的影响下,黄河冲淡水长期向莱州湾扩散;丰水期黄河冲淡水几乎影响了整个莱州湾,27盐度锋可以到达莱州湾中部,27等盐线的表层包络面积为2 665.61 km2,占莱州湾的1/4左右,枯水期低盐度水只有向南扩散的趋势,27以下的低盐度水集中分布在黄河口门附近,27等盐线的表层包络面积只有199.65 km2;5月份,随着入海径流量增加,27等盐线扩散的范围、距离、方向都会发生明显变化。在对近海生物资源有迫切保护需求的情景下,适当减少其他用水户供水量以增加入海生态径流量,可以有效改善黄河口海域附近的盐度情况,为生物资源的生长繁殖创造良好条件。  相似文献   

19.
珠江口及邻近水域鱼类群落结构研究   总被引：17，自引：2，他引：15  
詹海刚 《海洋学报》1998,20(3):91-97
根据1986～1987年珠江口及邻近水域底拖网鱼类采样资料,运用系统聚类与排序等多元分析方法和群落多样性指数,研究该水域鱼类群落结构及其与环境因素的关系,分析结果把该水域鱼类划分为淡水、河口和沿岸3个群落,分别位于莲花山,虎门河道、珠江河口伶仃洋和珠江口浅海水域,各群落结构组成呈沿盐度梯度而成带分布的格局.淡水群落结构简单稳定,沿岸群落结构比较复杂,河口群落受水动力过程和生物活动影响最大,群落结构的季节变化较为显着.  相似文献   

20.
东海沿岸海域表层海水酸化趋势及影响因素研究   总被引：1，自引：0，他引：1  
根据2002—2011年东海沿岸海域(4个区域,16个站位)春、夏、秋三个季节的表层海水pH、温度、盐度和叶绿素a等监测资料,对该海域pH的年际时空变化及其影响因素进行了探讨。结果表明,东海沿岸海域表层海水十年间pH变化趋势存在明显的季节和区域差异,共有10个站点表层海水pH呈下降趋势,主要集中于长江口和杭州湾海域,而三门湾和椒江口海域的酸化则不明显。环境因子相关性分析显示,杭州湾海域夏季表层海水的pH与叶绿素a浓度呈极显著正相关,其它海域两者间未显示出显著的相关性;杭州湾海域的pH与海表温度也存在显著的相关性,但季节不同趋势不同,呈现出春季正相关而夏季负相关的特征;pH与盐度的关系在各海域表现得更加明显,长江口、杭州湾和三门湾三个调查海区海水的pH变化与盐度都存在显著的正相关。总之,在10年的连续监测内东海沿岸海域存在一定程度的酸化趋势,其影响机制还需进一步研究。  相似文献   

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