Structural dynamics of bacterioplankton assemblages in the Lagoon of Venice

In this study we examined the spatial and temporal dynamics of planktonic bacterial assemblages at four different sites in the Lagoon of Venice. Samples were collected in January, April, July and October 2005 and several parameters (temperature, salinity, dissolved oxygen, chlorophyll a, dissolved macronutrients, dissolved and particulate organic carbon, viral and heterotrophic nanoplanktonic abundances) were determined in order to highlight the most important factors which are implied in shaping such assemblages. Furthermore we tested the relationship between similar assemblages and the patterns of activities (prokaryotic carbon production and several hydrolytic activities) that they perform in order to establish if, in this highly variable environment, similar assemblages behave in analogous ways. Results indicate that seasonality act as the main forcing on the communities. Moreover, we found a mismatch between community structure and patterns of activity possibly as a consequence of the heterogeneity of the lagoon which can affect in turn the assemblages' metabolic requirements (and thus their responses).     

黄海西北近岸沉积物中细菌群落空间分布特征

采用16S rDNA文库和变性梯度凝胶电泳(DGGE)技术,对黄海西北部3个近岸站位沉积物中细菌群落多样性及空间分布特征进行了调查和解析。对表层沉积物16S rDNA序列统计表明,各站位细菌群落多样性很高,γ-和δ-变形菌纲分别占克隆序列总数的20%~32%,是沉积物中的绝对优势类群。DGGE图谱分析表明,同一站位中不同深度的细菌群落结构相似性较高,而不同站位间群落结构相差较远。研究表明在黄海西北近岸沉积物中细菌群落多样性较高,优势类群明显,在较小尺度范围内群落结构的垂直变化不明显。     

Copepod assemblages in a highly complex hydrographic region

Community structure and diversity patterns of planktonic copepods were investigated for the Southwestern Atlantic Ocean between 34 and 41°S. Our objectives were (1) to define copepod assemblages, (2) to accurately identify their association to different water masses/hydrodynamic regimes, (3) to characterize the assemblages in terms of their community structure, and (4) to test if frontal boundaries between water masses separate copepod assemblages. Biogeographic patterns were investigated using multivariate analysis (cluster and ANOSIM analyses). Biodiversity patterns were examined using different univariate indexes (point species richness and taxonomic distinctness). Five regions of similar copepod assemblages were defined for our study area each one corresponding to different environments (freshwater, estuarine, continental shelf, Malvinas and Brazil current assemblages). These assemblages have major community structure differences. In spite of the complex oceanographic scenario of our study area, that can lead us to expect a pattern of copepod communities with diffuse boundaries, we found a strong spatial correspondence between these limits and the presence of permanent frontal structures.     

Limiting similarity, niche filtering and functional diversity in coastal lagoon fish communities

The fundamental idea behind the study of biodiversity patterns is the presumed connection between the shape of species assemblages and the functional ways in which they are organized, this functional organization referring to how species are related to one another, as competitors or members of a web of interactions and to how species are facing similar environmental constraints. Amongst the different facets of biodiversity, functional diversity is certainly a key for ecosystem processes in coastal areas. However, surprisingly, patterns of functional diversity have received little attention until now. After presenting a common framework linking functional diversity patterns to species coexistence theories, the aim of our study was twofold: (1) to seek assembly rules in brackish lagoon fish communities drove by functional traits. To this aim we used null models to examine the influence of two opposing forces acting on community structure: interspecific competition that might prevent the coexistence of the most similar species, and environmental filters that might result in the most similar species to coexist. (2) To seek relationships between fish functional diversity and environmental gradients, if any. Fish sampling was carried out in two coastal lagoons where stations differ considerably in terms of physicochemical parameters. Using morphological functional traits, functional diversity of fish communities was estimated using two recently published indices as well as a new proposed index. Firstly our study was not able to demonstrate a limitation of similarity in coexisting lagoon fishes due to interspecific competition. Conversely our results support the niche filtering hypothesis preventing species too dissimilar from one another to co-occur at the same station. Secondly, salinity was positively related to the functional diversity of fishes in both lagoons suggesting that within species assemblages near the channel species are less redundant than at stations far from the channel where species tend to be functionally similar (benthic and eating zooplankton).     

Differences in spatial and seasonal patterns of macrophyte assemblages between a coastal lagoon and the open sea

Although benthic macrophytes must be considered in monitoring programs to establish the ecological status of transitional and coastal waters in the European Union, the patterns of variability in species composition of macrophyte assemblages in Mediterranean coastal lagoons has scarcely been studied. In this work the spatial (both vertical and horizontal) and seasonal dynamics of macrophyte assemblages in a coastal lagoon (Mar Menor) are compared with those of open coastal assemblages in the SW Mediterranean to analyze any biological variability in lagoon assemblages and the factors that determine such variability. Different assemblages, characterized by well defined groups of species, can be described according to their isolation from the open sea and the type of substratum; at the same time, a vertical zonation pattern, similar to that found in all marine communities but more compressed, exists. This implies that when applying the EU Water Framework Directive or assessing environmental impact, a lagoon should not be considered spatially uniform and unique unit but as a mosaic of assemblages.     

海州湾赤潮高发区浮游细菌与赤潮及环境因子的关系

海州湾是南黄海赤潮高发区之一。为研究浮游细菌与赤潮及环境因子的关系,于2020年11月在海州湾赤潮期间进行了现场调查,采集了8个站位的浮游细菌、浮游植物样品,获取了温度、盐度、叶绿素a以及氮、磷、硅营养盐浓度等环境因子信息,分析了赤潮原因种及浮游细菌群落结构情况。结果显示,此次赤潮原因种为三叶原甲藻(Prorocentrum triestinum)、赤潮异弯藻(Heterosigma akashiwo)及塔胞藻(Pyramimonas sp.),发生赤潮时水温、盐度较低,盐度与赤潮异弯藻的分布有一定的联系。使用16SrRNA高通量测序方法分析调查海域的浮游细菌情况,结果显示赤潮发生站位的浮游细菌多样性略低于其他非赤潮发生站位,优势细菌与其他站位有明显不同,以假单胞菌目(Pseudomonadales)、红杆菌目(Rhodobacterales)和黄杆菌目(Flavobacteriales)为主。赤潮发生站位的浮游细菌群落结构也存在一定的差异,不同站位可能处于不同的赤潮阶段,对浮游细菌群落具有不同的影响。相关性分析显示,黄杆菌目与叶绿素a显著正相关,表明黄杆菌目与赤潮发生有一定的关系。     

Zonation and spatial distribution of littoral fish communities from the southwestern Finnish coast (Archipelago and Bothnian Sea,Northern Baltic Sea)

The aim of our study was to test whether the distribution of littoral fish assemblages would reflect both their immediate environment with reference to local underwater vegetation, including larger scale geographic archipelagial zonation. A total of 62 locations were sampled using beach seine and underwater video along the southwestern Finnish coastline in summer 2001. At all locations, water temperature, water transparency and benthic vegetation patterns (depth ranges of plant species or taxa) were recorded. Using correspondence analysis, our results showed a clear division of the Archipelago Sea into three separate zones based on littoral fish species assemblages. Overall, fish assemblages formed three distinct site groups, being dominated by pike and cyprinids, by percids and gobies, or by gasterosteids, and showed clear inner, middle and outer archipelago zones respectively, within the study area. Our results suggest that while vegetation in the study sites was diverse, it failed to express the zonation reflected by the littoral fish assemblages, which showed a definite zonation pattern which broadly reflected previous reports using both physical and biological parameters. We interpret our results to show that littoral vegetation is better in expressing small-scale differences between study sites, while littoral fish communities are more robust in detecting changes over a larger geographical scale.     

Benthic infaunal communities around two artificial reefs in Mamala Bay, Oahu, Hawaii

Non-fishery use of artificial reefs has been given attention in recent years. The primary concern associated with non-fishery artificial reefs is their effects to the surrounding ecosystems. This study examined the infaunal communities around two non-fishery artificial reefs (the sunken vessels YO257 and Sea Tiger) in Mamala Bay, Hawaii. Infaunal community structures at these artificial reefs were relatively similar to one at a nearly natural patch reef. A large amount of basalt gravel around YO257 associated with its deployment operation possibly had an effect on the surrounding community by increasing pore space. Polychaete assemblages were compared with existing data throughout the bay, and this revealed that the variation in sediment grain sizes and depths seemed to play some role in structuring the polychaete communities. Nevertheless, the infaunal communities around the artificial reefs were typical and within the range of natural variation in Mamala Bay, supporting their beneficial uses in ecotourism.     

Spatial and Temporal Patterns in Structure of Macrobenthic Assemblages. A Three-Year Study in the Northern Adriatic Sea in Front of the Po River Delta

Abstract. Coastal benthic communities in soft-bottom deposits of a restricted area were studied by seasonal sampling at nine stations. Faunal assemblages at three different depths were consistently different and exhibited a seasonal pattern of abundance and diversity. Multivariate statistical analyses suggest that each community structure is very similar during the three summer samplings; in autumn and winter many causes of disturbance can disrupt this structure, which is reconstituted the following summer. The stability of benthic communities in this physically variable environment is discussed and a "cyclic" adjustment mechanism of stability is proposed to explain the dynamics of the benthos in this area.     

乳山湾外海溶氧低值区细菌多样性初步研究

采用化学裂解法从乳山湾外海溶氧低值区不同溶解氧质量浓度(3.7～7.0mg.L-1)的6个站位海水样品中提取了环境DNA样品。以试剂盒纯化后的DNA样品为模板扩增其16SrRNA基因V3区,通过变性梯度凝胶电泳、分子文库构建及DNA测序对溶氧低值区海水中的细菌群落结构进行研究。结果表明,乳山湾外海溶氧低值区不同溶解氧质量浓度的6个站位底层海水样品中的细菌群落结构是相似的,它们均由隶属于Alteromonas(交替单胞菌属)、Salegentibacter(需盐杆菌属)等10个属的18种细菌组成。系统发育分析发现这些细菌分别属于α变形菌纲(2种)、γ变形菌纲(12种)和黄杆菌纲(3种)三个大类。在乳山湾外海溶氧低值区的海水样品中细菌多样性最高的类群是γ变形菌纲。     

16S rDNA克隆文库解析刺参(Apostichopus japonicas)苗种培育池中生物絮团的细菌群落结构*

提要 通过采集东营和蓬莱地区采用生物絮团技术的刺参(Apostichopus japonicas)苗种培育池(DYt和PLt)及其对照池(DYc和PLc)海水样品,构建细菌16S rDNA 克隆文库,对其中细菌群落的多样性和群落组成结构进行了分析。结果表明,四个文库Coverage值在34.7%～54.8%之间,文库丰富度指数(Chao)66.2～314.1,shannon多样性指数从3.01～4.07变动,Pielou均匀度指数0.68～0.85,样品的细菌群落均具有很高的多样性,蓬莱刺参苗种培育池细菌多样性均高于东营;生物絮团文库中细菌包括拟杆菌门(Bacteroidetes)、变形细菌门(Proteobacteria)、厚壁菌门(Firmicutes)等八个菌门和未知类群,黄杆菌群(Flavobacteria)、α-变形菌群(Alphaproteobacteria)芽孢杆菌纲(Bacilli)为主要优势菌群;DYt和PLt处理组文库细菌多样性减少并出现特征菌群,生物絮团调控技术改变了刺参苗种培育环境的微生物群落结构。生物絮团的细菌群落结构研究,为揭示生物絮团的作用机制并进一步有效利用提供研究基础和依据。     

海水循环水系统中环境因子对大西洋鲑体内土腥味物质含量的影响

为获知不同时期封闭式海水循环水养殖系统中水质因子、浮游植物和细菌群落结构对大西洋鲑(Salmo salar)体内土腥味物质含量变化的影响,于2018—2019年4次采集封闭式海水循环水养殖系统的水样和大西洋鲑。测定水体的氨氮、亚硝氮、硝氮、活性磷酸盐等指标,分析水体浮游植物群落结构并通过16S高通量测序测定水体中细菌群落结构,通过微波蒸馏-固相微萃取-气相色谱-质谱联用(MD-SPME-GC-MS)方法,分析大西洋鲑背肌中土臭素(Geosmin,GSM)和二甲基异冰片(2-methylisoborneol,MIB)的含量。研究发现:测定水质指标中温度、溶解氧、盐度、pH、氨氮、亚硝氮、硝氮、活性磷酸盐、总氮、总磷、总悬浮物和溶解性总有机碳在不同时期差异显著。共鉴定出浮游植物7门、13目、26属,蓝藻门(Cyanophyta)、硅藻门(Bacillariophyta)和绿藻门(Chlorophyta)为优势门;不同时期细菌群落中的优势菌门均为变形菌门(Proteobacteria)和拟杆菌门(Bacteroidetes),但细菌群落结构存在差异,这主要是由水质差异引起的。在不同时期,鱼体MIB含量均高于GSM含量,MIB为鱼体中主要的土腥味物质,在7和10月MIB含量较高。鱼体土腥味物质含量受浮游植物和细菌群落影响,而水质因子可能通过影响浮游植物和细菌群落的结构,来影响养殖鱼体内土腥味物质的含量。     

Benthic macrofauna and productivity regimes in the Barents Sea — Ecological implications in a changing Arctic

Benthic faunal assemblages were analysed from 47 stations in the central and southern parts of the Barents Sea, together with sedimentary and water column parameters, daily ice records and modelled integrated primary productivity. Sampling spanned areas influenced by Atlantic Water (AW) to those lying under Arctic Water (ArW), and included stations with mixed water masses. Ice cover suppressed water column productivity in the northern areas. Three main faunal groups were identified, based on similarity of numerical faunal composition. The northern and southern faunal groups were separated by the northernmost penetration of AW in the bottom water and the third group, the Hopen group, was influenced by modified bank water. Faunal abundances were significantly higher within the southern faunal group relative to the northern group, but the numbers of taxa present were similar. The particularly rich fauna of the Hopen group reflected sediment heterogeneity and tight pelagic–benthic coupling. These results suggest that a retreat and thinning of the ice cover in the Barents Sea likely will result in the northern parts of the Barents Sea becoming more Atlantic in character, with a higher productivity at the sea floor.     

Tidal exposure or microhabitats: what determines sandy‐beach nematode zonation? a case study of a macrotidal ridge‐and‐runnel sandy beach in Belgium

Lately, across‐shore zonation has been found to be more important in structuring the nematode community of a tropical macrotidal sandy beach than microhabitat heterogeneity. To evaluate whether this zonation pattern applies to a temperate beach, a macrotidal ridge‐and‐runnels sandy beach in the North Sea was studied. We investigated whether a similar zonation occurs in sandbar and runnel microhabitats, and whether the runnels harbour a different community from the subtidal. Our results indicate that nematode communities from runnel and sandbar habitats are significantly different. In addition, horizontal zonation patterns for nematode communities differ between both habitats. Nematode assemblages from sandbars are divided to lower, middle and upper beach while upper and middle runnels cluster together. The subtidal and upper runnels showed dissimilar nematode assemblages, although runnels showed the same dominant species (Daptonema normandicum), which increases its abundance towards the upper runnels. This study illustrates the importance of microhabitat heterogeneity, which resulted in different zonation patterns across the sandy beach examined. The divergent zonation between sandbars and runnels in the macrotidal temperate sandy beach, compared with the pattern observed for a subtropical sandy beach with similar morphodynamics, indicates that generalizations about nematode distribution patterns should be made with caution.     

人为干扰对岩礁潮间带无脊椎动物群落结构的影响

对烟台海域 6个岩礁潮间带生态学统的无脊椎动物群落的研究发现 ,东方小藤壶( Chthamallus challengeri )为第一优势种。其主要优势种——密鳞牡蛎 ( Ostrea denselamellosa )、短滨螺 ( Littorina brevicula)、紫贻贝 ( Mytilus edulis)和常见种——笠贝 ( Patelloida spp.)、红条毛腹石鳖( Acanthochiton rubrolineatus)、沙参 ( Nereisspp.)、海葵 ( Anthopleura midori )在群落中的优势地位和功能有明显的区别 ,尽管 6个岩礁潮间带群落的区系成分相近。对基于 RIV、RB和 RD的优势度曲线研究发现 ,基于 RIV和 RB的优势度曲线更适合于表示和描述受人为干扰和污染的潮间带无脊椎动物群落的结构和多样性变化。研究发现 ,6个潮间带的无脊椎动物群落皆受到不同程度的干扰 ,而养马岛和芝罘岛所受的干扰最轻。 6个岩礁潮间带的群落多样性序列依次为 :芝罘岛、养马岛、石沟屯、烟台山、玉岱山、月老湾。不同岩礁潮间带群落的种类组成和结构差异主要由来自采集和旅游者的干扰 ,养殖和生活污水造成的海水富营养化所致     

Archaeal community structure in sediments from a seamount in the Mariana Volcanic Arc

Seamounts are subsurface mountains in the ocean. Examination of the abundance and distribution of Archaea in seamount ecosystems may provide a better understanding of their ecological functions. Most studies of marine archaeal assemblages in seamount area have focused on hydrothermal vents or ferromanganese crusts. We investigated the archaeal communities from a seamount of the Mariana Volcanic Arc, in the tropical western Pacific Ocean by using high-throughput sequencing. Thaumarchaeota was dominant in the sediments of all sample stations. Community diversity and species richness were greatest at stations near the top of the seamount, and lowest at the deepest station. One sample station on the steep southeast slope that faced the Yap-Mariana trench had a unique composition of Archaea. In summary, depth has an important influence on archaeal community structure, and the geographic properties and sediment characteristics may explain the unique distribution patterns of Archaea in this seamount. This study provides a foundation for future research on Archaea in seamounts.     

Phylogenetic analysis of bacterial community in deep-sea sediment from the western Pacific “warm pool”

A depth profile of bacterial community structure in one deep-sea sediment core of the western Pacific ＂warm pool＂ （WP） was investigated and compared with that in a sediment sample from the eastern Pacific （EP） by phylogenetic analysis of 16S rDNA fragments. Five bacterial 16S rDNA clone libraries were constructed, and 133 clones with different restriction fragment length polymorphism （RFLP） patterns were sequenced. A phylogenetic analysis of these sequences revealed that the bacterial diversity in a sample from the WP was more abundant than that in the EP sample. The bacterial population in the sediment core of WP was composed of eight major lineages of the domain bacteria. Among them the γ-Proteobacteria was the predominant and most diverse group in each section of WP sediment core, followed by the α-Proteobacteria. The genus Colwellia belonging to γ-Proteobacteria was predominant in this sample. The shift of bacterial communities among different sections of the WP sediment core was δ-, ε-Proteobacteria, and Cytopahga-Flexibacteria-Bacteroides （CFB） group. The ratios between them in the bacterial communities all showed inversely proportional to the depth of sediment. The sequences related to sulphate reducing bacteria （SRB） were detected in every section. The bacterial community structure in this sediment core might be related to the environmental characteristics of the surface seawater of the western Pacific WP.     

Patterns of colonization and succession of benthic assemblages in two artificial substrates

Benthic communities colonizing two different typologies of artificial structures, Tecnoreef® pyramids (PY), and plinth modules (PL), differing for material and shape, were investigated for three years after their deployment on a soft bottom offshore Pedaso (Western Adriatic Sea). The aims were to describe the colonization patterns of benthic assemblages on the two artificial modules, to highlight possible differences between them and to detect the effectiveness of the artificial reef on the ecosystem functioning.The composition of the benthic communities settled on the two types of artificial substrates was different especially just after the reef deployment. Abundance and species richness were higher on PL in the first two years, while an explosion of individuals characterized PY in the third year. This suggested a delay of about one year in the colonization processes on PY likely due to the material and shape. The community settled of the artificial structures was dominated by hard-substrate species which are commonly absent in the natural environment. The occurrence of these organisms enriched the local soft-bottom communities and contributed to habitat diversification. This, together with the importance of these species in the diet of a few reef-dwelling fish, confirms the trophic role and the ecological importance of artificial reefs in areas characterized by soft seabed.     

A multidisciplinary study of the Cape Peloro brackish area (Messina, Italy): characterisation of trophic conditions, microbial abundances and activities

In the framework of the VECTOR DIVCOST Project, a 2-year investigation was started in 2006, with the aim of testing the sensibility of microbial parameters to environmental changes and of assessing whether they can provide information about functional changes in the carbon cycle. The investigation was performed in the surface waters of two small brackish ponds (Ganzirri and Faro), located in the Cape Peloro transitional area (Sicily, Italy). The seasonal changes in both the microbial compartment [bacterioplankton, vibrios, exoenzymatic hydrolysis of proteins and polysaccharides, bacterial secondary production (HBP) and community respiration] and the trophic state of suspended matter [total suspended matter (TSM), particulate organic carbon (POC), particulate organic nitrogen (PON), C/N] were analysed in relation to the hydrological characteristics [temperature, salinity, oxygen, fluorescence, NH₄, NO₂, NO₃, PO₄]. Despite marked differences in the nutritional input and the diversification in both carbon budget and trophic level, the two ponds show similar trends in many of the investigated factors, hardly influenced by seasonal variations. Temporally coupled trends were observed for some parameters (enzyme activities, vibrios abundances, respiratory activity), whereas others (POC, PON, heterotrophic bacterial production, bacterioplankton) showed a seasonal shift between the two lakes. The different behaviour found for the some biotic parameters suggests that their response to environmental conditions may be modulated differently between the two lakes, which, despite their spatial proximity and reciprocal connection, do not always show contemporaneous functional processes.     

Abundance and biomass of nano- and microplankton during the 1995 Northeast Monsoon and Spring Intermonsoon in the Arabian Sea

Phototrophic and heterotrophic nanoplankton (PNAN, HNAN; 2–20 μm protists) and microplankton (PMIC, HMIC; 20–200 μm protists and micrometazoa) are major components of the producer and consumer assemblages in oceanic plankton communities. Abundances and biomasses of these microorganisms were determined from samples collected along two transects during the Northeast Monsoon and Spring Intermonsoon process cruises of the US JGOFS Arabian Sea Program in 1995. Vertical profiles of these assemblages were strongly affected by the presence of a subsurface oxygen minimum layer. Abundances of all four assemblages decreased dramatically below the top of this layer. Depth-integrated (0–160 m) abundances and biomasses of nanoplankton and microplankton were of similar magnitude for most samples. Exceptions to this rule were primarily due to PMIC (mostly diatom) species which dominated phytoplankton assemblages at a few stations during each season. Depth-integrated biomasses for the combined nano- and microplankton averaged over all stations for each cruise were surprisingly similar for the Northeast Monsoon and Spring Intermonsoon seasons in this ecosystem (2.0 and 1.8 g C m⁻² [170 and 150 m moles C m⁻²] for the two seasons, respectively). Nano- and microplankton biomass for these two time periods constituted a signficant portion of the total amount of the particulate organic carbon (POC) in the water column. Summed over all stations, these assemblages constituted approximately 25–35% of the POC in the top 160 m of the northern Arabian Sea.