Zooplankton densities in a Hydrilla infested lake

The number of individuals and species of zooplankton were sampled concurrently with Hydrilla biomass and water quality for one year in a small, eutrophic central Florida lake. Throughout the study, rotifer species and individuals dominated the zooplankton. The abundance of the zooplankton tended to remain high when Hydrilla biomass was at its seasonal low during late winter and early spring. When hydrilla growth increased in the late spring and summer months causing a decrease in total alkalinity, specific conductivity, water color, turbidity, orthophosphate and chlorophyll a concentrations; the abundance of the zooplankton declined. During this time, there was a shift from limnetic to littoral species, principally rotifers. Hydrilla growth did not affect the mean number of cladoceran or copepod species, but may have led to an increase in rotifer species.     

Seasonal succession of zooplankton in the north basin of Lake Biwa

To examine the seasonal succession of the entire zooplankton community in Lake Biwa, zooplankton biomass (on an areal basis) and its distribution patterns among crustaceans, rotifers and ciliates were studied in the north basin from April 1997 to June 1998. Seasonal changes in phytoplankton and population dynamics of Daphnia galeata were also examined to assess food condition and predation pressure by fish. From March to November, crustaceans dominated zooplankton biomass, but rotifers and ciliates were dominant from December to February. Among crustaceans, Eodiaptomus japonicus was the most abundant species, followed by D. galeata. Zooplankton biomass increased from January to a peak in early April, just before the spring bloom of phytoplankton, then decreased in mid-April when mortality rate of D. galeata increased. From mid-June, zooplankton increased and maintained a high level until the beginning of November. During this period, both birth and mortality rates of D. galeata were relatively high and a number of rotifer and crustacean species were observed. However, their abundances were very limited except for E. japonicus which likely preys on ciliates and rotifers. In Lake Biwa, food sources other than phytoplankton, such as resuspended organic matter from the sediments, seems to play a crucial role in zooplankton succession from winter to early spring, while zooplankton community seems to be regulated mainly by fish predation from summer to fall.     

Dynamics and trophic roles of heterotrophic protists in the plankton of a freshwater tidal estuary

Freshwater tidal estuaries comprise the most upstream reaches of estuaries and are often characterised by the presence of dense bacterial and algal populations which provide a large food source for bacterivorous and algivorous protists. In 1996, the protistan community in the freshwater tidal reaches of the Schelde estuary was monitored to evaluate whether these high food levels are reflected in a similarly high heterotrophic protistan biomass. Protistan distribution patterns were compared to those of metazoan zooplankton to evaluate the possible role of top-down regulation of protists by metazoans. Apart from the algivorous sarcodine Asterocaelum, which reached high densities in summer, heterotrophic protistan biomass was dominated by ciliates and, second in importance, heterotrophic nanoflagellates (HNAN). HNAN abundance was low (annual average 2490 cells ml^–1) and did not display large seasonal variation. It is hypothesised that HNAN were top-down controlled by oligotrich ciliates throughout the year and by rotifers in summer. Ciliate abundance was generally relatively high (annual average 65 cells ml^–1) and peaked in winter (maximum 450 cells ml^–1). The decline of ciliate populations in summer was ascribed to grazing by rotifers, which developed dense populations in that season. In winter, ciliate populations were probably regulated `internally' by carnivorous ciliates (haptorids and Suctoria). Our observations suggest that, in this type of productive ecosystems, the microbial food web is mainly top-down controlled rather than regulated by food availability.     

The drift of zooplankton and microzoobenthos in the river Strandaelva,western Norway

The drift of zooplankton (rotifers, cladocerans, cyclopoid copepods) and microscopical zoobenthos (mainly bdelloid rotifers and small chironomid larvae) was investigated by filtering samples of river water. The number of drifting benthic rotifers varied between 1 000 and 6 000 ind. m^–3 in the lake inlet, and between 30 and 500 ind. m^–3 in the lake outlet, without any seasonal trend. The number of drifting insect larvae was approx. equal in the lake inlet and outlet, with a maximum in summer (250–300 ind. m^–3) and minimum in winter (ca. 10 ind. m^–3). Increasing water flow resulted in an increasing number of drifting zoobenthos. Downstream from the lake, the number of drifting benthic rotifers was increasing from approx. 300 ind. m^–3 in the outlet to 6 500 ind. m^–3 3.4 km downstream, while the number of insect larvae was ca. 100 ind. m^–3 in the outlet and leveled off at approx. 300 ind. m^–3 after 200 m. The number of drifting zooplankton in the lake outlet varied between 20 and 2 000 ind. m^–3 for crustaceans, and between 300 and 20 000 ind. m^–3 for rotifers, both with a maximum in late summer/autumn and a minimum in winter. The number of drifting zooplankton decreased by some 45% in the first 200 m from the lake outlet, but some zooplankton was still found in the drift 3.4 km downstream. The largest species was removed first from the drift. The diurnal variation in the number of drifting zooplankton in lake outlets appear to be related to the vertical migration in the lake, i.e. the largest number drifting when most animals are in the upper water layers.Contribution from the Voss Project, University of OsloContribution from the Voss Project, University of Oslo     

武汉东湖夏冬两季浮游动物物种多样性及群落结构研究

2018年7月、8月、12月及2019年1月, 对武汉东湖沿岸带的浮游动物群落分夏冬两季进行了调查研究。共鉴定出浮游动物35属50种, 其中轮虫22属37种、枝角类10属10种、桡足类3属3种。夏季优势物种为跨立小剑水蚤(Microcyclops varicans)、裂足臂尾轮虫(Brachionus diversicornis)和微型裸腹溞(Moina micrura); 冬季优势物种为长肢多肢轮虫(Polyarthra dolichoptera)、疣毛轮虫(Synchaeta spp.)、角突臂尾轮虫(Brachionus angularis)和犀轮虫(Rhinoglena sp.)。将观察到的浮游动物进行了图像信息采集, 并确定了部分物种SSU rRNA序列, 为淡水浮游动物的研究提供了参考资料。参考武汉东湖浮游动物研究的历史文献数据, 东湖数十年来浮游动物物种数逐渐下降, 轮虫优势物种由寡污型转为β-中污型甚至α-中污型。夏冬两季东湖浮游动物群落结构具有明显差异, 夏季轮虫平均密度(56.2 ind./L)和生物量(0.22 mg/L)低于冬季(476.3 ind./L、0.44 mg/L), 而甲壳类密度(137.8 ind./L)和生物量(2.88 mg/L)高于冬季(53.1 ind./L、1.12 mg/L)。夏季浮游动物群落Margalef丰富度指数、Shannon-Wiener多样性指数和Simpson多样性指数均高于冬季, 夏冬两季Pielou均匀度指数差异不大, 水质评价表明东湖夏季(中污染)优于冬季(重污染)。夏冬两季温度、溶解氧、pH、盐度和ORP五种环境因子均存在极显著差异, RDA分析表明, 其中温度对浮游动物群落结构的影响最大。     

福建北部近海浮游动物数量分布与水团季节变化的关系

根据2015—2016年在福建北部近海水域(120.10°E—120.65°E, 26.35°N—27.07°N)夏、秋、冬、春4个季节的海洋生态调查资料, 探讨了该水域浮游动物的数量分布、季节变化及其与水团变化的关系。结果表明, 调查水域浮游动物的平均生物量依次是: 夏季(479.51 mg/m3)>秋季(257.37 mg/m3)>春季(241.86 mg/m3)>冬季(84.05 mg/m3), 平均丰度依次是: 夏季(156.36 ind./m3)>春季(91.57 ind./m3)>秋季(40.34 ind./m3)>冬季(21.82 ind./m3), 生物量和丰度均值都呈现出夏季、秋季到冬季依次减少, 春季增多的趋势, 不同的是秋季生物量均值高于春季, 而丰度均值低于春季。在夏、冬和春三季, 浮游动物的总生物量和总丰度的分布总体较为一致; 而在秋季, 浮游动物的总生物量和总丰度的分布几乎相反。百陶箭虫(Sagitta bedoti)和微剌哲水蚤(Canthocalanus pauper)是影响夏季总丰度分布最主要的种类; 链钟水母(Desmophyes annectens)是影响秋季总丰度分布最主要的种类; 驼背隆哲水蚤(Acrocalanus gibber)、亚强真哲水蚤(Eucalanus subcrassus)和百陶箭虫对冬季总丰度的分布起到了重要影响; 五角水母(Muggiaea atlantica)和微剌哲水蚤是春季占总丰度比例较高的种类。浮游动物数量各季不同分布模式的根本原因是台湾暖流和浙闽沿岸流水团的季节性变化所致。研究结果不仅对了解与评价区域海洋生态系统动态和生物多样性变化具有重要的理论意义, 而且还可以丰富我国近海水域浮游动物的生态特征与水团变化之间的关系。     

Seasonal distribution,composition and abundance of the planktonic Ciliata and Testacea of Cayuga Lake

The planktonic protozoans (Ciliata and Testacea) of Cayuga Lake were studied from September 1974 through July 1975. Monthly collections were taken at four depths (surface, 15,31 and 92 m) at each of seven stations along the 125 m depth contour. All samples were collected with a 6-liter Van Dorn bottle sampler. Densities and biomass were determined for total protozoans and total zooplankton at each depth on each sampling date. Temperature profiles at one-meter intervals were also determined on or within a few days of the zooplankton sampling.The vertical distribution of the total protozoans was directly related to temperature; maximum densities corresponded to high summer surface temperatures. Dominant protozoan taxa included Didinium nasutum, Stokesia vernalis, Codonella cratera, Strobilidium gyrans, Strobilidium sp., Strombidium viride, Paradileptus canellai, Difflugia limnetica, and unidentified ciliates belonging to the families Halteriidae, Holophryidae, Epistylidae, and Vorticellidae. Protozoans composed 69% or more of the total zooplankton density on nine of eleven dates. Protozoan dominance was most evident during winter and spring, corresponding to the near absence of rotifers and microcrustaceans. Protozoans accounted for 30% or more of the zooplankton biomass from April through June, reaching 47% in May.     

浙江水源地河流浮游动物多样性与环境因子的通径分析

为探明水源地河流浮游动物多样性及与水环境因子的关系, 利用浮游动物多样性参数监测水质, 2010-2014年间, 我们于每年的冬季(1月)、春季(4月)、夏季(7月)和秋季(10月), 对浙江2个水源地河流采样站(H1站和H2站)展开浮游动物种类组成、丰度和多样性指数的季节性调查, 同时测定水环境因子。结果表明, H1站和H2站浮游动物平均丰度分别为1,387.4 ind./L和873.0 ind./L, 小型浮游动物(轮虫 + 桡足类无节幼体)丰度分别占92.8% (H1站)和91.5% (H2站)。两采样站轮虫、枝角类和桡足类的优势种均为针簇多肢轮虫(Polyarthra trigla)、短尾秀体溞(Diaphanosoma brachyurum)和温剑水蚤(Thermocyclops sp.)。多元逐步回归与通径分析结果表明: 冬季氮磷比是轮虫类Shannon-Wiener多样性指数(H′)波动的限制因子, 主要通过总磷含量对轮虫类H′指数产生较大的间接正向作用; 春季氮磷比是轮虫类H′指数发展的决策因子; 秋季氮磷比可通过总氮含量对轮虫类H′指数产生较大的间接正向作用。冬季氨氮、总氮含量分别是甲壳动物体积多样性指数(Hs)的决策因子和限制因子。夏季溶解氧含量是总浮游动物物种丰富度(d)波动的限制因子, 主要通过pH值对d指数产生较大的间接正向作用, 作用机制表现为轮虫类H′指数随着夏季溶解氧含量的升高呈极显著上升(P < 0.01), 而甲壳动物Hs指数则显著下降(P < 0.05)。水源地河流环境因子与浮游动物多样性之间的相互关系为浙江水源地生态学监测提供了可能性。     

The predator-prey relationship of perch,Perca fluviatilis,larvae and zooplankton in two Scottish lochs

Synopsis Food consumption of perch larvae and the impact of this on zooplankton were examined in two adjacent shallow Scottish lochs. Maximum annual abundance of zooplankton occurred in mid-May at L. Kinord with minimum values in mid-June. Copepods were prominent in spring but were followed by a multi-species community of cladocerans and rotifers in summer. At L. Davan zooplankton biomass remained high through summer with cladocerans dominating andDaphnia longispina the most frequent species. Availability of food items was a principal factor governing feeding behaviour of larvae. Copepodite stages were initially the most common item in the diet in L. Kinord in 1976 and 1977 and rotifers the principal food in June 1977, reflecting the dominance of these items in the zooplankton. Cladocerans were dominant in the plankton community in L. Davan and constituted the greater part of food intake. Overlying this general pattern there was an increase in the size of food items taken by larvae with time and also a definite pattern of food selection for copepods, with initially selection for smaller copepodite stages and later for larger stages and adults. On most occasions larvae selected forCyclops strenuus abyssorum andPolphemus pediculus and selected againstDaphnia longispina. The reduction in the total zooplankton biomass attributed to perch larvae was minimal, with the exception of mid-June at L. Kinord in 1976. However, predation on particular species and copepodite stages was occasionally intense and may have impacted the zooplankton populations.     

Community characteristics and of zooplankton in Qinzhou Bay

Qinzhou Bay, the biggest bay in Guangxi Province, is very species-rich and is developing a robust marine economy. In recent years, as human impact has increased, problems associated with the environment have become more complicated. Measuring zooplankton diversity and abundance is a way to monitor environmental conditions. According to the data from four ecological surveys of the zooplankton in Qinzhou Bay during 2008 and 2009, a total of 134 species of zooplankton were identified, including 52 Copepoda species, 27 Medusa species, 14 Planktonic larvae, 9 Chaetognatha species, 8 Pteropoda species, 5 Amphipoda species, 4 Cladocera species, 4 Ostracoda species, 3 Thaliacea species, 2 Appendiculata species, 2 Sergestdae species, 2 Protlsta species, 1 Rotiera species and 1 Cumacea species. The fauna was clearly characterized as tropical population. The total species number was highest in autumn, followed by spring, winter and summer. Zooplankton species diversity in Qinzhou Bay has increased compared with the results obtained in 1983–1985 (83 species). However, compared with other bays, the number of zooplankton species in Qinzhou Bay is close to Daya Bay (128), higher than in Zhilin Bay (60), Jiaozhou Bay (81) and Luoyuan Bay (70), and far lower than in the north South Sea (709). We adopted the dominant index Y > 0.02 as the distinguishing standard of dominant species. The number of dominant species in spring, summer, autumn and winter were six, nine, eight and five. There was only one common dominant species (Penilia avirostris) appeared in different seasons, For summer and autumn, the shared dominant species numbered about four. Between other seasons, the shared dominant species varied between two and three. The number of uniquely dominant species was four in summer, three in autumn and one in both spring and winter. The dominant species in different seasons have some overlaps and some differences. The average biomass of zooplankton was 378 mg/m³ at all times of year. The average biomass was largest in autumn, followed by winter, and was the least in spring and summer. The average density of zooplankton for the entire year was 805.11 ind/m³. The average density was largest in summer, followed by winter, and was least in autumn and spring. Copepoda and Planktonic larvae were the major components of zooplankton in spring and summer at Qinzhou Bay, with the other species’ densities under 10%. In autumn, Copepoda, Planktonic larvae and Chaetognatha were the major components of the biomass, and in winter, the major species were Copepoda and Cladocera, with the others species’ density under 10%. The average value of the Shannon–Wiener diversity index (H′) was 3.84 and the evenness index (J′) was 0.77. The zooplankton diversity index and community evenness overall were good and the community organization had a complete and stable state, but the status of the community was relatively weak. The relationship between biomass/density of zooplankton and environmental factors is remarkable. Biomass and density are positively correlated with temperature and nutrient concentration, and are negatively correlated with salinity.     

极端水文干旱下鄱阳湖浮游动物群落结构特征及其影响因素

2022年鄱阳湖流域发生了特大干旱事件,对鄱阳湖生态环境产生了严重影响。为揭示极端水文干旱年的鄱阳湖浮游动物群落结构特征及其主要影响因素,于2022年1月(冬季)、4月(春季)、7月(夏季)和10月(秋季)对鄱阳湖浮游动物进行了综合调查。本次调查共鉴定出浮游动物70种(轮虫40种、桡足类17种和枝角类13种),丰度和生物量范围分别为0—152.67个/L和0—1.52 mg/L。浮游动物群落结构具有较大的时空差异：在季节上,物种数夏季最多,丰度和生物量呈现夏季最高、秋季最低的特征,干旱季节的Shannon-Wiener多样性指数和优势种组成明显不同于非干旱季节;在空间上,南部湖区的物种数、丰度、生物量高于北部湖区,多样性指数在中部湖区最高、北部湖区最低。极端水文干旱年的物种数、丰度和生物量均明显低于往年同期,但空间上的差异较小。相关性分析和冗余分析结果表明,浮游动物群落结构在干旱季节和非干旱季节的主要影响因素存在明显差异,其中干旱季节浮游动物群落结构主要受水温、水位、硝态氮、氨氮等的共同影响,非干旱季节受化学需氧量和水位的影响较大。总体上,极端水文干旱使得鄱阳湖浮游动物群落结构稳定性较...     

舟山海域大中型浮游动物群落时空变化及受控要素

为更好地保护舟山海域的渔业资源和生态环境,了解舟山海域浮游动物组成的时空变化,于2014年到2017年对舟山海域33个站位开展4个季节的生态综合调查,结果表明:4个航次共鉴定出浮游动物成体88种和浮游幼体19类,优势种共12种,浮游动物的优势种更替和群落特征季节变化明显,春夏、夏秋、秋冬、冬春相邻季节优势种更替率分别为75%、80%、100%和60%;平均生物量为夏季(176.34 mg/m³)>春季(120.20 mg/m³)和秋季(86.28 mg/m³)>冬季(7.21 mg/m³);平均丰度为夏季(143.97个/m³)>春季(86.30个/m³)>秋季(21.38个/m³)和冬季(26.86个/m³);平均多样性指数:夏季(3.03)>秋季(2.82)>春季(2.05)>冬季(1.71)。舟山海域浮游动物群落具有明显的季节和区域差异,温度、盐度、Chl a和营养盐是影响舟山浮游动物群落时空变化的主要环境因素,其中春季浮游动物群落空间分布主要受盐度的影响,夏季主要受温度、盐度和Chl a的影响,秋季主要受Chl a的影响,冬季主要受悬浮物和溶解氧的影响,而营养盐对每个季节的浮游动物群落分布都有一定的影响。     

Distribution patterns of mesozooplankton biomass in the North Sea

During spring 1986 and winter 1987, zooplankton samples were collected over the entire North Sea by means of a multi-closing net-system. Before taxonomic treatment, wet weight estimates and carbon content conversions were carried out. From this data set, 4 962 522 tons zooplankton biomass (dry weight) were estimated for the whole North Sea during the spring survey. High biomasses (more than 100 mg C/m³) were located in areas between the Orkneys and the Shetlands, off the mouth of the Firth of Forth, the Channel and the river Rhine. Considerable zooplankton biomass was also found parallel to the Danish west coast. Furthermore, a narrow tongue of high biomass (partly greater than 200 mg C/m³) intruded from the north, between 1 °E and 4 °E, into the northern North Sea, turning to the east at 56°N, and continuing into deeper water layers to form a left turning “helix” of high biomass in the central part of the North Sea. During the winter survey the carbon content of the zooplankton stock was a factor 10 lower than in summer. Altogether, 519340 tons of zooplankton biomass (dry weight) were estimated in winter. Centres of relatively high biomass were located off the mouth of the rivers Rhine, Weser and Elbe and off the British east coast moving in a cyclic way across the Dogger Bank into the central North Sea. A further maximum of zooplankton abundance was found in the Skagerrak region. However, an intrusion of zooplankton from the shelf edge into the North Sea was not observed in winter. A qualitative analysis of species composition showed that small copepods dominated the zooplankton in the southern and eastern North Sea. The “eddy” of high biomass in the northern North Sea observed in spring, however, was mostly shaped by the large copepodCalanus finmarchicus (70–90%). The distribution of zooplankton biomass in the North Sea is discussed in relation to the hydrographic conditions and to the biology of the dominant species.     

浙江水源地水库浮游动物丰度和生物量与水质参数的通径分析

为探明浙江水源地水库浮游动物群落特征及与环境因子的关系, 达到用浮游动物群落参数监测水源地水库水质的目的。于2014年1月至2016年10月, 对10个饮用水源地水库(K1—K10)展开了水质参数、浮游动物丰度和生物量的季节调查。采用多元逐步回归与通径分析的方法, 研究了浙江水源地水库环境因子与浮游动物群落之间的相互关系和作用过程。结果表明, 2014—2016年水库浮游动物平均密度97.5 ind./L, 主要由桡足类无节幼体(占36.3%)、轮虫(28.4%)和剑水蚤(20.0%)组成。平均生物量289.3 μg/L, 主要由枝角类(占39.3%)、剑水蚤(29.0%)和哲水蚤(14.5%)组成。Chl. a含量是春、夏季水库浮游动物丰度的决策因子, TP含量是秋、冬季群落丰度波动的限制因子, 春季TN通过N﹕P比率影响群落丰度。DO含量是冬季和夏季水库浮游动物生物量发展的决策因子, 冬季DO通过降低N﹕P比促进群落生物量发展。水库浮游动物现存量受到了TP含量消长、N﹕P比率变化, 以及最终反映的水体Chl.a含量共同影响。     

Larger zooplankton in Danish lakes after cold winters: are winter fish kills of importance?

Winter fish kills can be intense under ice in shallow lakes, and have cascading effects on the food web and ultimately on lake water clarity. In maritime Western Europe, winters are usually mild, but occasional colder periods may also have strong effects on lake fish communities. Global warming may have disproportionate effects by delaying freezing and shortening the period of ice coverage. We studied differences in zooplankton (cladocerans, copepods, and rotifers): phytoplankton biomass, zooplankton community structure, and individual body size among 37 Danish lakes of various depths, chemical characteristics, and trophy, by comparing four winters of different severity (mean winter temperatures ranging from −1.19°C in 1996 to +2.9°C in 1995). We found that crustacean mean body sizes were significantly larger in the summer following a severely cold winter. The zooplankton communities in the summer after a cold winter had a significantly larger proportion of larger-bodied species and taxa. Phytoplankton biomass, expressed as chlorophyll-a (chl-a), was lower and zooplankton herbivory (chl-a:TP index), higher, in the summer after the severely cold winter of 1995/1996. All these effects were stronger in shallow lakes than in deep lakes. Changes in zooplankton during summer 1996, compared with other years, were likely caused by fish kills under ice during the preceding severe winter of 1995–1996. Fish kills due to under ice oxygen depletion would be expected to occur earlier and be more complete in the shorter water columns of shallow lakes. With climate change, severe winters are predicted to become less frequent and the winters to be milder and shorter. In general, this is likely to lead to higher winter survival of fish, lower zooplankton grazing of phytoplankton the following summer and more turbid waters, particularly in shallow eutrophic lakes.     

大陈岛海域浮游动物群落季节变化及其影响因素

为探究大陈岛海域浮游动物群落的季节变化,于2020年9月（夏季）、11月（秋季）和2021年1月（冬季）、4月（春季）分别对大陈岛海域的浮游动物及环境因子进行了4个航次的调查。结果共鉴定浮游动物90种,包括浮游幼体15类,其中夏季种类数最多（68种）,冬季最少（20种）,常见的优势种有：百陶箭虫（Sagitta bedoti）、微刺哲水蚤（Canthocalanus pauper）、中华哲水蚤（Calanus sinicus）等12种（Y>0.02）。浮游动物的年平均丰度和生物量分别为（153.40±214.73）个/m³、（411.93±561.76） mg/m³,二者存在明显的季节变化,平均丰度为春季（380.17±296.14）个/m³>夏季（135.30±112.59）个/m³>秋季（67.88±90.52）个/m³>冬季（25.30±19.11）个/m³;平均生物量为夏季（895.01±802.54） mg/m³>春季（623.39±358.73） mg/m³>秋季（91.08±82.36） mg/m³>冬季（45.96±84.95） mg/m³。多样性指数（H''）和均匀度指数（J''）的年平均值分别为1.71±0.96和0.53±0.20,均表现出夏秋季较高、冬春季较低的特征。聚类分析结果表明调查海域的浮游动物可划分为夏季类群、秋季类群、冬季类群和春季类群4组类群。Pearson相关性分析和冗余分析（RDA）结果表明,海水温度、盐度、叶绿素a浓度是影响大陈岛海域浮游动物群落特征的重要环境因素。此外,夏季大陈岛海域水母类浮游动物暴发的现象值得关注。研究结果将为大陈岛海域的生物多样性保护及渔业资源可持续开发利用提供可参考的数据资料。     

Annual cycle of zooplankton community in the Abra Harbour (Bay of Biscay): abundance, composition and size spectra

The annual cycle of the zooplankton community in a coastal embaymentof the Bay of Biscay was studied from data on zooplankton fractionslarger than 45 and 250 µm Smaller zooplankton and chlorophyllmaxima coincided in summer, while larger zooplankton reachedthe maximum in spring. Copepods dominated in both fractionsmost of the year, being copepod nauplii and postnaupliar stagesof Oithona nana and Paracalanus parvus the main constituentsof the microzooplankton maxima, and older copepodites and adultsof Acartw clausi of the meso-macrozooplankton maxima. Secondarypeaks of abundance due to protozoan blooms of Steno-semellanivalu, in early spring, and Noctiluca santillans, in summer,were also observed in smaller and larger fractions respectively.The collapse of phytoplankton biomass in early autumn was followedby a strong decrease of zooplankton in mid autumn. From thisperiod to winter, chlorophyll and zooplankton abundance showedsmall variations, but noticeable changes in the compositionand size spectra of zooplankton were observed. In winter, valuesof chlorophyll and zooplankton abundance reached minima, A.clausidominated the copepod assemblage and carnivorous zooplankterswere absent or negligible The annual development of the mainpredator populations (Sagitta frideria, Luiopc tetraphylla andanchovies) were found to be synchronized with the variationsin abundance and size spectra of zooplankton in the study area.     

太平湖浮游动物动态演替与环境因子的相关性研究

2012年11月至2014年10月, 对太平湖浮游动物群落进行了为期两年的调查研究。共鉴定出浮游动物45属89种, 其中轮虫 29属69种、枝角类5属7种、桡足类2属4种和原生动物9属9种; 优势种主要来自于轮虫异尾轮虫属(Trichocereca)和龟甲轮虫属(Keratella)。浮游动物的丰度值存在明显的季节变化, 表现为夏季最大, 平均达1326 ind./L, 秋季春季次之, 分别为608和605 ind./L, 冬季最小为216 ind./L; 垂直分布表现为春夏季太平湖表层浮游动物丰度最高, 中间层次之, 底层最小, 秋冬季则表现为中间层最高。浮游动物群落Shannon-Wiener多样性指数和Margalef丰富度指数中间层普遍高于表层和底层, Pielou均匀度指数表现为底层要高于表层和中间层, 季节变化表现为夏秋季显著高于冬春季的现象, 水质评价表明夏秋季水质好于春冬季。聚类和多维尺度分析表明: 太平湖浮游动物可分为夏秋季类群与春冬季类群, 两类群均表现为湖心与上下游区域群落结构差异较大, 其中春冬季类群差异较明显; 相关和逐步回归分析表明: 透明度和水温为太平湖浮游动物群落结构变化的主要环境影响因子; 依据结构方程模型(SEM)和冗余分析(RDA)的结果显示, 在溶解氧和水温较高的水环境中浮游动物丰度值表现为较大, 其中水温对轮虫的影响高于对枝角类和桡足类的影响。     

Plankton biomass partitioning in a eutrophic subtropical lake: comparison with results from temperate lake ecosystems

Plankton were sampled for 6 years in a subtropical eutrophiclake in FL, USA, and absolute and relative carbon biomass wasdetermined for bacteria, phytoplankton, heterotrophic and phototrophicnanoflagellates, ciliates, rotifers and crustacean zooplankton.We compared the results with findings from a comprehensive studyof carbon biomass partitioning in eutrophic German lakes withelucidate common patterns and differences. Similarities betweenthe temperate and subtropical systems included: similar seasonaldynamics, with maximal carbon biomass of nanoflagellates andmetazoan zooplankton in spring and phytoplankton in summer toautumn, yearly averaged carbon occurring mainly in the phytoplanktonand phytoplankton accounting for a much greater proportion ofcarbon than bacteria. There also were differences: the Floridalake had lower absolute and relative carbon biomass in crustaceanzooplankton, stronger dominance of protozoa in total grazercarbon biomass, a lower ratio of zooplankton to phytoplanktoncarbon and almost a monoculture of predation-resistant copepods(versus a relatively balanced distribution of carbon among cladocerans,copepods and rotifers in the temperate lakes). The subtropicallake also had 4-fold higher relative biomass of small filamentouscyanobacteria in its phytoplankton, which we attribute to lightlimitation. Although the Florida and German studies did notmeasure biomass of planktivorous fish, the differences observedhere are consistent with a recent hypothesis that fish predationexerts stronger top–down control on the pelagic food webin subtropical lakes than in temperate lakes of similar trophicstatus.     

Effects of ice duration on plankton succession during spring in a shallow polymictic lake

1. Long-term records of air temperature and ice phenology (ice duration), and phyto- and zooplankton time series (1979–1997) were used to study the effects of ice duration on the successional pattern within plankton communities during spring in a shallow polymictic lake. 2. Water temperature in March was significantly lower after cold winters when compared to average or mild winters. Mean water temperature in April was not significantly different after mild, average or cold winters, but showed an overall significant negative correlation with ice duration. 3. Ice duration affected the timing and the magnitude of the peak abundance of diatoms, rotifers and daphnids during spring, but had no direct effects on the timing and maximum of chlorophytes, cryptophytes, cyanobacteria, bosminids and cyclopoid copepods. 4. Plankton groups which appeared first in the seasonal succession (i.e. diatoms, rotifers and daphnids) reached maximum abundance earlier after mild and average winters. The peak abundance of diatoms was negatively correlated with ice duration, whereas that of rotifers and daphnids was independent of the conditions during the preceding winter. 5. Temperature alone was generally a poor predictor of the timing and magnitude of both phyto- and zooplankton maxima. Turbulence may be important in the timing and the magnitude of peaks in diatoms, while total algal biomass was the most important determinant for the timing of the rotifer maximum. The magnitude of the daphnid maxima were significantly influenced by water temperature in March and April, and by rotifer abundance. The magnitude of the bosminid maximum was correlated with food availability and predation, whereas the timing of the maximum was more closely related to water temperature in May. 6. We conclude that, as a result of the low heat storage capacity of shallow lakes, the effects of winter on planktonic communities are short lived, and soon overtaken by the prevailing weather and by biotic interactions.