Plankton abundance in relation to physicochemical factors in the Bui reservoir of Ghana's Black Volta River

The relationship between physicochemical factors and plankton abundance in the newly created Bui reservoir was studied during 2011 and 2012. The objective was to assess the influence of physicochemical factors on plankton abundance and provide data for monitoring the hydrobiology of the newly created Bui reservoir. Two sampling stations were selected on the Black Volta upstream (Bui) and downstream (Bamboi) of the dam, with samples taken pre‐ and postimpoundment during the study period. Canonical Correspondence Analysis (CCA) was used to trace temporal plankton community changes and to examine the relationships between species composition and physicochemical variables. The relative abundance of some phytoplankton species such as Anabaena sp., Planktothrix sp. and Scenedesmus sp. was directly correlated to nitrates. CCA indicated that physicochemical variables explained 41–64% of zooplankton and 8–12% of phytoplankton variation. Hence, there were correlations between environmental variables and the structure of plankton assemblages. This feature should therefore be used for bio‐monitoring of environmental variables of the river by the Bui Power Authority to ensure protection of the aquatic biota downstream of the Bui dam.     

东湖浮游生物群落DNA指纹结构及其与环境理化因子的关系

对武汉东湖5个不同湖区的浮游生物群落DNA进行了RAPD指纹分析,并探讨了DNA指纹结构与环境理化因子的关系．结果表明：所筛选的9条随机引物共扩增210条大小为150～2000bp的谱带,多态率为93．3％．各站点平均有42条谱带,其中Ⅳ站最多（53条）,Ⅴ站最少（35条）．Ⅰ站的PO4^3--P、TP含量最高,Ⅴ站的NH4^＋-N、TN、NO2^--N含量最高,Ⅳ站各理化因子含量均低于其他站点,站点间COD、碱度、硬度、钙含量差异不大．相似性聚类分析表明,基于RAPD标记的浮游生物群落指纹将5个站点划分为两类：Ⅰ、Ⅱ、Ⅲ站聚为一枝,Ⅳ、Ⅴ站聚为另一枝．这与湖区主要理化因子的聚类结果一致．说明东湖不同湖区浮游生物群落DNA指纹与其环境理化因子密切相关．     

Spatiotemporal heterogeneity of plankton communities in Lake Donghu, China, as revealed by PCR-denaturing gradient gel electrophoresis and its relation to biotic and abiotic factors.

The 16S and 18S rRNA genes of planktonic organisms derived from five stations with nutrient gradients in Lake Donghu, China, were studied by PCR-denaturing gradient gel electrophoresis (DGGE) fingerprinting, and the relationships between the genetic diversity of the plankton community and biotic/abiotic factors are discussed. The concentrations of total nitrogen (TN), total phosphorus (TP), NH(4)-N and As were found to be significantly related (P<0.05) to morphological composition of the plankton community. Both chemical and morphological analyses suggested that temporal heterogeneity was comparatively higher than spatial heterogeneity in Lake Donghu. Although the morphological composition was not identical to the DGGE fingerprints in characterizing habitat similarity, the two strongest eutrophic stations (I and II) were always initially grouped into one cluster. Canonical correspondence analysis suggested that the factors strongly correlated with the first two ordination axes were seasonally different. The concentrations of TN and TP and the densities of rotifers and crustaceans were generally the main factors related to the DGGE patterns of the plankton communities. The study suggested that genetic diversity as depicted by metagenomic techniques (such as PCR-DGGE fingerprinting) is a promising tool for ecological study of plankton communities and that such techniques are likely to play an increasingly important role in assessing the environmental conditions of aquatic habitats.     

The biogeography of marine plankton traits

Changes in marine plankton communities driven by environmental variability impact the marine food web and global biogeochemical cycles of carbon and other elements. To predict and assess these community shifts and their consequences, ecologists are increasingly investigating how the functional traits of plankton determine their relative fitness along environmental and biological gradients. Laboratory, field and modelling studies are adopting this trait‐based approach to map the biogeography of plankton traits that underlies variations in plankton communities. Here, we review progress towards understanding the regulatory roles of several key plankton functional traits, including cell size, N₂‐fixation and mixotrophy among phytoplankton, and body size, ontogeny and feeding behaviour for zooplankton. The trait biogeographical approach sheds light on what structures plankton communities in the current ocean, as well as under climate change scenarios, and also allows for finer resolution of community function because community trait composition determines the rates of significant processes, including carbon export. Although understanding of trait biogeography is growing, uncertainties remain that stem, in part, from the paucity of observations describing plankton functional traits. Thus, in addition to recommending widespread adoption of the trait‐based approach, we advocate for enhanced collection, standardisation and dissemination of plankton functional trait data.     

Spatiotemporal heterogeneity of plankton communities in Lake Donghu, China, as revealed by PCR–denaturing gradient gel electrophoresis and its relation to biotic and abiotic factors

The 16S and 18S rRNA genes of planktonic organisms derived from five stations with nutrient gradients in Lake Donghu, China, were studied by PCR–denaturing gradient gel electrophoresis (DGGE) fingerprinting, and the relationships between the genetic diversity of the plankton community and biotic/abiotic factors are discussed. The concentrations of total nitrogen (TN), total phosphorus (TP), NH₄-N and As were found to be significantly related ( P <0.05) to morphological composition of the plankton community. Both chemical and morphological analyses suggested that temporal heterogeneity was comparatively higher than spatial heterogeneity in Lake Donghu. Although the morphological composition was not identical to the DGGE fingerprints in characterizing habitat similarity, the two strongest eutrophic stations (I and II) were always initially grouped into one cluster. Canonical correspondence analysis suggested that the factors strongly correlated with the first two ordination axes were seasonally different. The concentrations of TN and TP and the densities of rotifers and crustaceans were generally the main factors related to the DGGE patterns of the plankton communities. The study suggested that genetic diversity as depicted by metagenomic techniques (such as PCR-DGGE fingerprinting) is a promising tool for ecological study of plankton communities and that such techniques are likely to play an increasingly important role in assessing the environmental conditions of aquatic habitats.     

Longitudinal differentiation among pelagic populations in a planktic foraminifer

Evolutionary processes in marine plankton have been assumed to be dependent on the oceanic circulation system, which transports plankton between populations in marine surface waters. Gene flow facilitated by oceanic currents along longitudinal gradients may efficiently impede genetic differentiation of pelagic populations in the absence of confounding marine environmental effects. However, how responsible oceanic currents are for the geographic distribution and dispersal of plankton is poorly understood. We examined the phylogeography of the planktic foraminifer Pulleniatina obliquiloculata in the Indo-Pacific Warm Pool (IPWP) by using partial small subunit ribosomal DNA (SSU rDNA) sequences. We found longitudinal clines in the frequencies of three distinct genetic types in the IPWP area. These frequencies were correlated with environmental factors that are characteristic of three water masses in the IPWP. Noteworthy, populations inhabiting longitudinally distant water masses at the Pacific and Indian sides of the IPWP were genetically different, despite transportation of individuals via oceanic currents. These results demonstrate that populations of pelagic plankton have diverged genetically among different water masses within a single climate zone. Changes of the oceanic circulation system could have impacted the geographic patterns of dispersal and divergence of pelagic plankton.     

Comparative plankton investigations in a brackish lake (L. Veere) and a brackish tidal estuary (Westerschelde) in the SW Netherlands

Summary As the data, presented in this lecture, have been published elsewhere (see references), only a summary is given here.A comparison was made between the plankton assemblages of the mesoand polyhaline ranges of Lake Veere and the Westerschelde estuary. Species composition, densities and seasonal distributions of the predominant planktonic organisms of the investigated brackish water ecosystems were quite different, depending on several other environmental factors than salinity.     

Scaling patterns of plankton diversity: a study of ciliates in a tropical coastal lagoon

Although spatial and temporal variation in plankton diversity is regularly investigated in surveys, experiments, and models, there is a lack of methods for predicting spatial patchiness of plankton diversity. We develop and apply a suite of geostatistical and multiple-regression analysis tools to assess ciliate diversity in a tropical coastal lagoon; these methods can predict spatial and temporal patterns of diversity, provide error estimates associated with these predictions, and assess which environmental factors may drive diversity patchiness. Geostatistical analysis was applied to H′ (Shannon diversity index) from 25 to 35 data collected from a sampling grid (40 × 40 m), and 10 dispersed lagoonal sites, in the dry and rainy seasons, on numerous occasions. Conditional simulation and kriging were used to predict diversity at the lagoonal and small scales, respectively. The relationship between diversity (H′) and the environment was examined by multiple-regression analysis. Thirty-six ciliate morphospecies occurred; H′ ranged from 0 to 1.9 and was patchy. Multiple regression indicated ciliate diversity changed seasonally, increasing when the sand bar was open and the lagoon was connected with the sea. Geostatistical analysis extended the recognition that seasonal changes alter diversity: when the rainy season produced a variable environment, relatively small scale patches and diversity gradients occurred; in the dry season, when the lagoon was physically uniform, larger and fewer diversity patches occurred; at the sublagoonal scale, diversity patches were similarly structured in the two seasons. Results indicate environmental variability and immigration can be the main drivers behind ciliate diversity in the lagoon. We recommend the patterns these data reveal and methods we employ be considered when further studies are continued to examine diversity on local and larger scales. Handling editor: S. Declerck     

Eukaryotic plankton communities across reef environments in Bocas del Toro Archipelago,Panamá

Variation in light and temperature can influence the genetic diversity and structure of marine plankton communities. While open-ocean plankton communities receive much scientific attention, little is known about how environmental variation affects plankton communities on tropical coral reefs. Here, we characterize eukaryotic plankton communities on coral reefs across the Bocas del Toro Archipelago, Panamá. Temperature loggers were deployed, and midday light levels were measured to quantify environmental differences across reefs at four inshore and four offshore sites (Inshore = Punta Donato, Smithsonian Tropical Research Institute (STRI) Point, Cristobal, Punta Laurel and Offshore = Drago Mar, Bastimentos North, Bastimentos South, and Cayo de Agua). Triplicate vertical plankton tows were collected midday, and high-throughput 18S ribosomal DNA metabarcoding was leveraged to investigate the relationship between eukaryotic plankton community structure and inshore/offshore reef environments. Plankton communities from STRI Point were additionally characterized in the morning (~ 08:00), midday (~ 12:00), and late-day (~ 16:00) to quantify temporal variation within a single site. We found that inshore reefs experienced higher average seawater temperatures, while offshore sites offered higher light levels, presumably associated with reduced water turbidity on reefs further from shore. These significant environmental differences between inshore and offshore reefs corresponded with overall plankton community differences. We also found that temporal variation played a structuring role within these plankton communities, and conclude that time of community sampling is an important consideration for future studies. Follow-up studies focusing on more intensive sampling efforts across space and time, coupled with techniques that can detect more subtle genetic differences between and within communities will more fully capture plankton dynamics in this region and beyond.

     

Effect of temporal and geographical factors on fatty acid composition of M. galloprovincialis from the Adriatic sea

Soft body tissue and gill and mantle microsomal membranes of Mytilus galloprovincialis, were analyzed to assess geographical and temporal effects on fatty acid distribution with special focus on n-3 polyunsaturated fatty acid (PUFA) content. Mussels and plankton samples were collected in April and in October from three locations of the North Adriatic Sea. Plankton fatty acid composition apparently depended both on the sampling site and time and differences referable to temporal features prevailed on the geographical ones. Accordingly, also mussel fatty acid composition appeared to be more effectively modulated by sampling time rather than by sampling location. Membrane fatty acids showed high homeostatic capabilities to reduce effects of exogenous input on cellular organization. Selective capabilities apparently enable mussels to modulate their fatty acid composition combining plankton input, environmental effects on lipid metabolism and physiological requirements. The constantly higher n-3/n-6 ratio in April than in October, shared by fatty acids of plankton, soft tissues and microsomal membranes, confirms the influence of temporal factors in fatty acid modulation. On these bases, late spring is suggested to be the more suitable period for collecting mussels destined for healthy diet of humans or other animals.     

Determining Microeukaryotic Plankton Community around Xiamen Island,Southeast China,Using Illumina MiSeq and PCR-DGGE Techniques

Microeukaryotic plankton are important components of aquatic environments and play key roles in marine microbial food webs; however, little is known about their genetic diversity in subtropical offshore areas. Here we examined the community composition and genetic diversity of the microeukaryotic plankton in Xiamen offshore water by PCR-DGGE (polymerase chain reaction-denaturing gradient gel electrophoresis), clone-based sequencing and Illumina based sequencing. The Illumina MiSeq sequencing revealed a much (approximately two orders of magnitude) higher species richness of the microeukaryotic community than DGGE, but there were no significant difference in species richness and diversity among the northern, eastern, southern or western stations based on both methods. In this study, Copepoda, Ciliophora, Chlorophyta, Dinophyceae, Cryptophyta and Bacillariophyta (diatoms) were the dominant groups even though diatoms were not detected by DGGE. Our Illumina based results indicated that two northern communities (sites N2 and N3) were significantly different from others in having more protozoa and fewer diatoms. Redundancy analysis (RDA) showed that both temperature and salinity were the significant environmental factors influencing dominant species communities, whereas the full microeukaryotic community appeared to be affected by a complex of environmental factors. Our results suggested that extensive sampling combined with more deep sequencing are needed to obtain the complete diversity of the microeukaryotic community, and different diversity patterns for both abundant and rare taxa may be important in evaluating the marine ecosystem health.     

Composition and indication of plankton fatty acids under the influence of environmental factors in the Hongfeng Reservoir,Southwest China

Aquatic Ecology - To clarify the indication of plankton fatty acids (FAs) under the influence of the natural environmental factors that affect FA composition and transmission, the Hongfeng...     

Contribution of Crenarchaeota and Euryarchaeota to the prokaryotic plankton in the coastal northwestern Black Sea

The NW Black Sea is an area with peculiar hydrological, hydrochemicaland biological features (river plume dynamics, coastal upwelling,intense eutrophication, blooms algae). We determined the abundanceand distribution of the two major groups of Archaea (Crenarchaeotaand Euryarchaeota) in three contrasting sites of the NW BlackSea from May to August 2004 to estimate the contribution ofnon-extremophilic Archaea to the coastal prokaryotic plankton.Using catalyzed reporter deposition-fluorescence in situ hybridization,Euryarchaeota were found to be particularly prominent (11–22%of total prokaryotic plankton) in the low-salinity waters duringlate-spring and summer, whereas Crenarchaeota contributed only5% to the prokaryotic community in these waters. The abundanceof Crenarchaeota was highest in nutrient- and particle-richwaters and lowest in offshore Black Sea surface waters. Theseresults confirm recent studies on the distribution of planktonicArchaea with Euryarchaeota dominating the archaeal communityin surface waters. Statistical analyses indicated significantcorrelations between crenarchaeotal abundance, ammonia and nitrateconcentrations at each sites. Our data show that the archaealplankton constitute an important and dynamic component of theprokaryotic plankton in the coastal oxygenated waters of theNW Black Sea and might play a significant role in the nitrogencycle.     

Pathways of unauthorized fish introductions and types of management responses

The study of the relationships among environmental factors, primary production, zooplankton community, and feeding behavior of fish species represents a key aspect to obtain a deeper knowledge of biological processes acting at ecosystem level. In this context, oceanographic data and biological samples were collected in two different surveys, carried out during late June 2011 and early July 2015 in the Strait of Sicily (Central Mediterranean Sea). Differences in abundance, biomass, and assemblage structure of zooplankton and anchovy (Engraulis encrasicolus Linnaeus, 1758) population were observed between the two surveys. Still, zooplankton biomass was significantly correlated to longitude, chlorophyll a recorded during the surveys (as a proxy of primary production), and oxygen concentrations. Such differences affected the isotopic composition of anchovy, which showed changes in δ¹⁵N and δ¹³C values between the two surveys. Mixing models identified different contributions of food sources in the two sampling periods, i.e., major consumption on large copepods and euphausiids in 2015 with respect to 2011, which was consistent with a greater availability of these preys in the environment in 2015. The obtained results evidenced that E. encrasicolus may be affected by any environmental change that influences the plankton community, which is the basis of the diet of these fishes. Such findings highlighted the importance to further investigate the trophic relationships among different compartments of the food web, as well as the possible environmental influences, in order to obtain a more complete picture of ecosystem functioning and also in the light of an ecosystem-based approach to fisheries management.     

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...     

Microbial eukaryote plankton communities of high‐mountain lakes from three continents exhibit strong biogeographic patterns

Microbial eukaryotes hold a key role in aquatic ecosystem functioning. Yet, their diversity in freshwater lakes, particularly in high‐mountain lakes, is relatively unknown compared with the marine environment. Low nutrient availability, low water temperature and high ultraviolet radiation make most high‐mountain lakes extremely challenging habitats for life and require specific molecular and physiological adaptations. We therefore expected that these ecosystems support a plankton diversity that differs notably from other freshwater lakes. In addition, we hypothesized that the communities under study exhibit geographic structuring. Our rationale was that geographic dispersal of small‐sized eukaryotes in high‐mountain lakes over continental distances seems difficult. We analysed hypervariable V4 fragments of the SSU rRNA gene to compare the genetic microbial eukaryote diversity in high‐mountain lakes located in the European Alps, the Chilean Altiplano and the Ethiopian Bale Mountains. Microbial eukaryotes were not globally distributed corroborating patterns found for bacteria, multicellular animals and plants. Instead, the plankton community composition emerged as a highly specific fingerprint of a geographic region even on higher taxonomic levels. The intraregional heterogeneity of the investigated lakes was mirrored in shifts in microbial eukaryote community structure, which, however, was much less pronounced compared with interregional beta‐diversity. Statistical analyses revealed that on a regional scale, environmental factors are strong predictors for plankton community structures in high‐mountain lakes. While on long‐distance scales (>10 000 km), isolation by distance is the most plausible scenario, on intermediate scales (up to 6000 km), both contemporary environmental factors and historical contingencies interact to shift plankton community structures.     

海洋浮游生物介导的弧菌传播扩散机制研究进展

弧菌在全球范围内广泛存在,弧菌病的暴发和流行不仅给海水养殖业造成巨大的经济损失,还严重威胁人类健康。一些弧菌可以通过与环境中浮游植物和浮游动物的相互作用提高自身存活率和环境持久性,并进行跨海域传播。本文综述了海洋浮游生物作为部分弧菌物种储库的作用及影响因素,以及气候变化和人类活动等因素驱动下浮游生物间接介导的弧菌传播扩散特性;并重点介绍了弧菌特定的结构、代谢途径和次级代谢产物在其与浮游生物互作过程中发挥的独特作用及其机制;提出今后应从分子层面深入解析浮游生物与弧菌的相互作用机制,从全球尺度阐释浮游生物介导的弧菌跨海域传播机制,建立弧菌疾病传播预测模型和预警系统,为浮游生物介导的弧菌传播扩散风险的防控提供重要信息。     

Plankton dynamics under different climate conditions in tropical freshwater systems (a reply to the comment by Sarmento,Amado & Descy, )

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