湘江干流浮游生物群落结构及水质状况分析

为了解湘江干流水质与生物群落现状, 2010-2011年对湘江的水质和浮游生物的分布进行了采样分析, 利用香农-威纳多样性指数分析湘江干流浮游生物群落特征, 并结合水质理化指标评价其水体营养状态。结果表明, 共检出浮游植物8门99属164种, 丰度变化在(1.83-51.1)104cells/L, 生物量变化在0.03-0.60 mg/L; 浮游动物80种, 密度变化在2.16-76.34个/L, 生物量变化在0.01-1.95 mg/L。各采样点的浮游植物多样性指数变化在2.47-5.43, 浮游动物多样性指数变化在1.63-3.38, 浮游生物的多样性较好, 显示出湘江干流的浮游生物群落处于较稳定的状态。对湘江m-m指示种种类组成和群落结构分析, 结果显示湘江水体属于中污带水质; 综合营养状态指数(TIL)在38.27-51.97, 均值为43.73, 属于中营养水平; 综合水质生物学和化学评价结果可知湘江干流的水质较差, 但无明显向富营养化转化的趋势。       

Phases in the development of riverine plankton: Examples from the rivers Rhine and Meuse

Observations on phyto and zooplankton in two hydrographically different rivers were compared in order to discriminate phases in plankton development. Along the longitudinal axis of the River Rhine a gradual increase in the development of phytoplankton was observed, which reached its maximumca. 100 km before the river flows into its artificial sedimentation area. The development of rotifer populations was slightly retarded as compared with that of phytoplankton and highest population densities were only reached in the sedimentation area. Crustaceans developed in significant numbers, not until the river water had entered the sedimentation area. Development of zooplankton coincided here with a strong decrease in the density of phytoplankton. A similar trend in plankton development was observed in the River Meuse, although in this river the highest densities of phyto and zooplankton already occurred in its middle reaches. The differences in the timing of plankton growth in the two rivers are probably caused by differences in flow regime between both rivers. The River Rhine, which is fed by rainwater and melting of glaciers in the Alps, has a relatively constant discharge. On the other hand, the low discharge of the rain-fed River Meuse combined with an increased residence time of the water as a consequence of large numbers of weirs, allows a full cycle of plankton development long before its discharge into the sea. This phenomenon was also reflected in the silicate cycle in the Meuse, where the consumption by planktonic diatoms and the regeneration of silicate of deposits seem to be important. In contrast, in the main branches of the River Rhine only the effects of silicate consumption were detectable.     

长江口浮游甲壳动物空间分布特征

2010年研究了长江口南、北支浮游甲壳动物的空间分布特征。共采集到浮游甲壳动物50种,其中桡足类39种,枝角类11种。种类数南支高于北支;平均密度北支高于南支,南、北支分别为1.7 ind./L和61.8 ind./L。基于群落相似性矩阵的CLUSTER聚类和MDS分析显示,在群落相似性为40%时,长江口区域浮游甲壳动物群落可分为北支组、南支组1和南支组2共3组。3组的优势种有差异。浮游甲壳动物的平均密度变化趋势为北支组（61.8±22.11 ind./L）〉南支组1（3.07±2.06 ind./L）〉南支组2（0.72±0.45 ind./L）。盐度、潮汐和径流量是影响长江口南北支浮游甲壳动物种类组成、密度和空间分布差异的重要环境因素。     

鄱阳湖国家级自然保护区浮游生物群落结构及空间分布

为评价春季大旱后鄱阳湖国家级自然保护区浮游生物现状,对保护区所辖 8 个子湖及赣江和修河部分河段的浮游生物进行调查和分析。调查共发现浮游植物 53 属 97 种、浮游动物 23 属 42 种（包括原生动物 13 种、轮虫 23 种、枝角类 3 种和桡足类 3 种）,其中大湖池和朱市湖是浮游生物种类数最多的 2 个子湖。各子湖及赣江和修河间浮游生物现存量差异较大,其变化范围分别为260（8.18106）cells/L（浮游植物）、363073173 ind./L（浮游动物）,赣江以西区域的子湖和修河的浮游生物现存量显著高于赣江及其以东区域的子湖。调查水域优势度值（Y）大于 0.02 的浮游生物包括蓝藻 1 种、绿藻 2 种、硅藻 5 种、原生动物 4 种及轮虫 5 种。浮游生物 Shannon-Wiener 多样性指数（H'）和均匀度指数（J）的最大值均分别为 2.41 和 0.96,而其丰富度指数（Dm）值均小于 3。3 种多样性指数综合评价表明,保护区各子湖与修河和赣江水体受污染程度较轻,除蚌湖和梅西湖外,均处于中污状态。       

鄱阳湖不同水文期浮游生物群落结构特征和影响因素及水质评价

为阐明鄱阳湖不同水文期浮游生物群落结构特征及其影响因素,研究于2017年8月(丰水期)和12月(枯水期)在鄱阳湖湖区典型水域设置5个采样点进行浮游生物采样调查。研究期间共鉴定浮游植物8门75属186种,丰水期与枯水期均以硅藻门和绿藻门为主。共鉴定浮游动物4类76种,丰水期与枯水期均以原生动物和轮虫为主。方差分析显示:浮游植物密度与生物量在不同水文期之间的差异均为极显著(P<0.01),浮游动物丰水期密度高于枯水期,但无显著差异(P>0.05),浮游动物生物量(P<0.05)在不同水文期差异显著。冗余分析(RDA)显示:丰水期透明度和浮游生物呈显著负相关关系,电导率和浮游生物呈显著正相关。透明度、电导率与营养盐是影响丰水期浮游生物群落结构的主要环境因素,枯水期水温和溶解氧是驱动鄱阳湖浮游生物群落生态分布的主要环境因素。基于Shannon-Wiener(H′)、Margalef(d)和Pielou(J)等生物多样性指数的水质评价结果表明:鄱阳湖研究区域水质状态处于寡污-中污之间。研究揭示了2个水文期对通江湖泊浮游生物的影响:季节变化不改变湖泊浮游生物的物种组成及优势种,但...     

Biodiversity of testate amoebae (Arcellinida and Euglyphida) in different habitats of a lake in the Upper Paraná River floodplain

This study aimed to investigate the testate amoebae (Arcellinida and Eugliphida) species diversity in plankton, macrophytes and aquatic sediment samples from a shallow lake of the Upper Paraná River floodplain. Samples were carried out from April 2007 to March 2008. We recorded 89 taxa, belonging to 10 families. Eighty-two taxa were found in the aquatic sediment, 71 in the macrophytes and 53 in the plankton. Highest values of alpha diversity were observed in the aquatic sediment. Although the plankton had the highest number of accidental species, accessory and constant species were also observed in this habitat. Most of the species classified as constant for the plankton belonged to the genus Arcella. Most of the constant species in the macrophytes and aquatic sediment belonged to the genus Difflugia. This study supports the idea that the presence of these protists in the plankton should not be attributed only to stochastic processes because (i) the species diversity recorded in this habitat was remarkably high in relation to the total biodiversity of the lake, and (ii) we also recorded frequent and constant species in the plankton.     

Responses of billabong rotifer communities to inundation

Daily plankton collections were taken from a billabong of the River Murray for two weeks prior to inundation in March 1990, and continued for ten days after flooding. Quantitative responses of the plankton community and the component species were analysed against measured environmental variables and between species. Rotifers and copepod nauplii were the predominant net plankton (> 53 µm). Significant negative or positive responses to inundation were detected for most common taxa of 63 rotifer species recorded. A four-fold dilution from intrusion of river water masked rapid population increases. Opportunistic responses to inundation appear to be a survival strategy in the highly unpredictable billabong environment.     

Halicyclops korodiensis Onabamiro (Crustacea,Copepoda) in the estuary of the Warri River,Nigeria, West Africa

Halicyclops korodiensis Onabamiro was recorded in plankton samples of the brackish waters of the Warri River, Nigeria, West Africa. It is redescribed and figured.     

Plankton dynamics in a dead arm of the River Waal: a comparison with the main channel

It has been postulated that areas of reduced flow along rivers,either within the river channel or in the form of backwaters,exert a considerable influence on plankton dynamics in rivers.To test this hypothesis, a survey of plankton distribution ina dead arm along the River Waal, a branch of the River Rhine,was made. The euphotic fraction of the water column varied alongthe transect. Phytoplankton species composition changed fromdiatom-dominated populations in the river to dominance of greenalgae near the rear end of the dead arm. Green algae were dominatedby Pandorina morum. The diatoms were dominated by typicallyriverine species, like Cyclotella menegh-iniana, Skeletonemapotamos and Skeletonema subsalsum. The total zooplankton biovolumeat the rear end was >100 times higher than in the river.In the river, rotifers and crustaceans co-dominated, whereasto the rear end the crustaceans became dominant. Diaphanosomabrachyurum was the most abundant zooplankter. The dynamic behaviourof both phytoplankton and zooplankton suggests the presenceof an intense grazing network in the dead arm. There were alsosome indications of a rapid transfer of biomass to higher consumerlevels, such as fish. The large difference in species compositionbetween the dead arm and the river itself does not suggest amajor influence by backwaters along the River Rhine. This maybe due to its channelized nature. The situation can be differentin rivers with a more natural morphology.     

Nectonema zealandica n. sp. (Nematomorpha: Nectonematoidea) parasitising the purple rock crab Hemigrapsus edwardsi (Brachyura: Decapoda) in New Zealand,with notes on the prevalence of infection and host defence reactions

A new species of Acusicola is described based on adults of both sexes taken from plankton samples collected in the upper reaches of the Piauí River estuary, in the northeast of Brazil. Ovigerous females were present in the plankton. The new species, Acusicola minuta n. sp., can be distinguished from its congeners by its small body size, female antennal morphology and leg setation. The male described here as A. minuta n. sp. is the first known male attributed to the genus.     

Nitrogen fixation and denitrification in plankton and periphyton of the Kama River Basin watercourses

The results of studies on molecular nitrogen fixation and denitrification by plankton, epiphytone, and epilithone in a number of natural and anthropogenic waterways of the Kama River Basin are presented for summer and autumn periods of 2005. The nitrogen fixation and denitrification was quantified by acetylene gas chromatography. The phototrophic anoxybiotic purple non-sulfurous bacteria, in particular, of Rhodopseudomonas, Rhodobacter and Rhodocyclus genera, play a significant role in active denitrification in the presence of sulfide-free flow water in the Kama River and its inflows in epilithone, algal-bacterial mats, and biological sewage disposal plants in Perm. On the other hand, the heterocyst cyanobacteria of Anabaena and Aphanizomenon genera had a leading position in active N₂ fixation in the plankton and periphyton of the lower river streams.     

嘉陵江浮游生物群落结构研究

为揭示嘉陵江梯级水库浮游生物群落结构特征,按枯水期和丰水期对嘉陵江12个梯级水库24个样点进行浮游生物的野外采集,分析其群落结构的物种组成,并采用Shannon-wiener指数、Margalef指数和Pielou均匀度指数进行分析.结果表明:嘉陵江四川段浮游植物共8门42科95属171种,浮游动物的组成共有4纲9目21科30属62种;浮游动物优势种类有21种.浮游生物评价结果表明梯级库区水质处于中度污染状态.     

Selenium in sediment and food webs of the Tapajós River basin (Brazilian Amazon) and its relation to mercury

BackgroundWe investigated Se levels along the Tapajós River basin - which is an important tributary of the Amazon River - and the possible antagonistic effect of Se in Hg availability. This is the first study to investigate Se transfer from abiotic to biotic compartments and along the food chain in aquatic ecosystems of the Amazon basin.MethodsSe concentrations were measured in superficial sediment (n = 29), plankton (n = 28) and fishes (n = 121) along two stretches of the Tapajós River basin (Tap_up/mi and Tap_low), comprising approximately 500 km with different hydrological characteristics.ResultsSe concentrations in sediment were significantly higher in the Tap_low (345−664 μg kg⁻¹) than in the Tap_up/mi (60−424 μg kg⁻¹). The seasonal flooding of the Amazon River probably helps to carry selenium-rich sediment to the Tapajós mouth (Tap_low stretch). We suggest that Se in sediment could decrease the bioavailability of Hg resulting in lower MeHg concentrations in fish, as observed in the Tap_low (45−934 μg kg⁻¹). Sediment and plankton were positively correlated in relation to their Se concentrations (r = 0.62; p = 0.001) suggesting that sediment can possibly be the main source of Se to plankton. Our data indicate Se uptake by primary consumers, as noted in phytoplankton levels. The decrease of Se concentrations along the food chain was also noteworthy.ConclusionThis work elucidates some aspects of Se biogeochemistry in the Amazon basin and shows its importance regarding Hg cycles in aquatic ecosystems.     

Contribution of biofilm‐dwelling consumers to pelagic–benthic coupling in a large river

1. Over the course of this 17‐month study, we assessed the potential loss of plankton (bacteria, algae, heterotrophic flagellates) to consumers (ciliates and rotifers) within mature biofilms established on natural substrata exposed to the main current of the River Rhine (Germany). Once a month, in flow cells in a bypass system to the River Rhine, we measured the clearance rates of the biofilm‐associated consumers on the different groups within the natural plankton. 2. Ciliates were the most dominant consumers, among which planktivorous groups, particularly peritrichs and (in spring and summer) heterotrichs dominated. Consumer biomass varied with season, with the highest density occurring directly after the appearance of the phytoplankton spring peak. 3. Clearance rates on plankton ranged from 96 to 565 L m^?2 d^?1 for bacteria and 66–749 L m^?2 d^?1 for algae, with a preference for algae in summer and for bacteria in winter. This pattern coincided with seasonal changes in the structures of the grazer communities. The consumers (both ciliates and rotifers with total standing stocks ranging between 19 and 572 mg C m^?2) imported a substantial amount of organic matter (between 15 and 137 mg C m^?2 d^?1) into the biofilm. 4. These results highlight the potential importance of consumers in the biofilm as a trophic link between the plankton and the benthos, a function that has hitherto mostly been attributed to filter‐feeding bivalves. In contrast to bivalves, the biofilm‐dwelling consumers show a more dynamic response towards the plankton density and composition. Such dynamic components need to be considered when estimating total plankton consumption by the benthos.     

Biomass size spectra of net plankton in the adjacent area near the Yangtze River Estuary in spring

Based on data from survey carried out in spring 2005, the biomass size spectra of net plankton were explored in the adjacent sea of Yangtze River Estuary. Results revealed an approximately continuous size distribution of plankton individuals, from phytoplankton (5–250 μm cell^?1 in equivalent sphere diameter (ESD), 15 pg–146 ng C cell^?1) to zooplankton (120 μm–2 cm ESD, 115 ng–7.5 mg C ind^?1). The normalized spectra (carbon scale) were linear with slope ranged from –0.889 to –0.445, and intercept ranged from 12.866 to 16.863 (all stations together, slope = –0.606, intercept = 19.448), indicating strong deviations from the ideal value (slope = –1.22) of a steady pelagic ecosystem. Correlation analysis presented that intercept and regression coefficient of net plankton size spectra had significant relationship with plankton biomass size diversity.     

The structure of the planktic microbial community in the lower reaches of the Ob River near Salekhard

We studied the distribution of the main components of planktic food web: bacteria, heterotrophic flagellates, and ciliates in the lower reaches of the Ob River near the town of Salekhard. In the early summer, the abundance, biomass, and diversity of protozoans were low; the plankton community was dominated by heterotrophic bacteria whose biomass was higher than that of phyto- and zooplankton. Downstream of Salekhard, biomass and abundance of bacterioplankton were increased due to household and industrial wastewater. The data obtained showed the importance of heterotrophic organisms in trophic dynamics and self-purification of the lower reaches of the Ob River.     

Effects of the benthic suspension feeder Dreissena polymorpha on zooplankton in a large river

1. We conducted a series of in situ enclosure experiments to assess the impact of zebra mussels ( Dreissena polymorpha ) on the plankton of the Ohio River. Adult mussels were suspended in pelagic enclosures ('potamocorrals') at three densities (0, 1000, 2500 mussels per corral) and incubated for 6 days with daily plankton and physiochemical sampling.
2. The presence of adult zebra mussels was correlated with a shift in composition of the phytoplankton community and a severe reduction in some rotifers. The effects of zebra mussels on the larger zooplankton were taxon-dependent, but bacterial density showed no trend among treatments.
3. Zebra mussels may have significant negative impacts on zooplankton, which may in turn alter riverine food webs.     

New Data on the Distribution of Kellicottia bostoniensis (Rousselet, 1908) (Rotifera: Monogononta: Brachionidae): Its Presence in Argentina

The discovery of this species in plankton samples taken at five stations in the Iguazú River and Uruguay River (in a reservoir and an affluent) is reported. Data on the morphology and measurements of individuals collected are shown. This species had previously been registered in Brazil, South America, where it has dispersed widely. The Iguazú River, tributary of the Paraná River, and the Uruguay River could constitute an important dispersal path from Brazilian territory to aquatic environments of Del Plata basin which contains 85% of the freshwater of Argentina.     

Persistence and growth of the fecal indicator bacteria enterococci in detritus and natural estuarine plankton communities

Enterococci are used to evaluate recreational-water quality and health risks in marine environments. In addition to their occurrence in feces of warm blooded animals, they are also common epiphytes. We investigated the contribution of plankton- or particle-associated enterococci in estuarine and coastal water. Seven water and size-fractionated plankton samples were collected monthly between April 2008 and January 2009 in the tidal reaches of the Skidaway River (Georgia, USA). Each size fraction, along with filtered (<30 μm) and bulk estuarine water, was processed according to U.S. Environmental Protection Agency method 1600. Presumptive enterococci were selected and species were identified using carbon substrate utilization patterns. The highest average densities occurred within the 30-, 63-, 105-, and 150-μm size fractions, which also represented the majority (>99%) of the particles within the sampled water. Particle-associated enterococci accounted for as little as 1% of enterococci in bulk water in April to as much as 95% in July. Enterococcus faecalis was the most commonly isolated species from both water and plankton and represented 31% (16/51) and 35% (6/17) of the identified Enterococcus species from water and plankton, respectively. Enterococcus casseliflavus represented 29% of the selected isolates from plankton and 16% from water. Both E. faecalis and E. casseliflavus were able to survive and grow in plankton suspensions significantly longer than in artificial seawater. Enterococcus spp. may be highly concentrated in plankton and associated particles, especially during summer and fall months. These findings could have implications for the effectiveness of enterococci as an indicator of coastal water quality, especially in particle-rich environments.     

Influence of Environmental Heterogeneity on the Structure of Testate Amoebae (Protozoa,Rhizopoda) Assemblages in the Plankton of the Upper Paraná River Floodplain,Brazil

In freshwater environments, testate amoebae are usually found associated with macrophytes and sediments and many studies have suggested that their occurrence in plankton samples is accidental. This implies that predictable patterns detected in planktonic assemblages should not be observed in testate amoebae assemblages. This hypothesis was tested in this study. Plankton samples were collected from different environments in the Upper Paraná River floodplain. Results show that patterns in species composition and abundance of testate amoebae are predictable, and that dominant species tend to present characteristic shell morphology in hydrologically different environments. We suggest that testate amoebae must be routinely included in plankton ecology studies, at least in floodplain environments.