Diel Fluctuations of a Shallow Water Fish Community in the Inner Oslofjord, Norway

Abstract. A shallow water fish community in the inner Oslofjord, Norway, was sampled with a beach seine at 4h intervals over two 36 h periods (25-26th May and 28-29th September, 1982). Night length varied from 1 h in May to 11 h in September. Differences in the community composition were observed between May and September. The diversity of the fish community changed between the two months although the interpretation of the change was dependent on the method used to analyse the community. The three dominant species ( Gasterosteus aculeatus, Sprattus sprattus , and Ammodytes tobianus ) showed diel variations in catch rate which were out of phase with each other. The percentage overlap in abundance of the dominant species was low. The summation of the individual periodicities resulted in aperiodicity at the community level. There were fluctuations, over a diel cycle, in all the community parameters (number of individuals, number of species, species diversity [H'J, species richness [D] and evenness [J']) which affect measures of resource partitioning in fish communities and which should therefore be considered in ecological studies. Diel fluctuations in abundance of some individual shallow water species varied between seasons causing problems in population estimates.     

Seasonal and annual change in community structure of meso-sized copepods in Tokyo Bay, Japan

Seasonal change in the meso-sized copepod community structure in the central part of Tokyo Bay was investigated from January 2006 to December 2008. Three seasonal community groups were detected, and seasonal shifts of these communities are explained by life history characteristics of indicator species and seasonal changes in the hydrographical environment. In the winter-spring community, Acartia omorii and Centropages abdominalis dominate because of high growth rates at low temperature. A shift to the early summer community is caused by a diapause of Ce. abdominalis as resting eggs and an increase in the growth and egg-production rate of Pseudodiaptomus marinus at high temperature. A shift to the summer-fall community is caused by a diapause of A. omorii at hypoxic and high temperature conditions and an increase of Temora turbinata, Paracalanus parvus and other oceanic species by an enhancement of the estuary circulation. Then, the community returns to a winter-spring one by the recovery of A. omorii and Ce. abdominalis with low temperatures and oxygenation of bottom water and by the disappearance of oceanic warm-water species at low temperature. Seasonal community shifts occurred almost regularly, but the shift from a winter-spring community to an early summer one occurred 1 month early in 2007 when the water temperature was warmer than in other years.     

海州湾秋季鱼类β多样性组分分析及其与环境因子的关系

由于过度捕捞等人类活动的胁迫,近年来海州湾渔业资源严重衰退.为了解海州湾鱼类β多样性的变化特征及其影响因素,本研究根据2013?2017年秋季在海州湾及其邻近海域进行的渔业资源底拖网调查数据,采用S?renson相异性指数等方法计算了调查站位间以及海州湾海域整体的鱼类β多样性,并将β多样性分解为周转和嵌套两个组分,分析...     

Soft‐bottom macrobenthic communities of Manukau Harbour,New Zealand

A survey of the macrobenthos at 42 stations in the channels and subtidal sandflats in Manukau Harbour, Auckland, revealed four biotic associations; although referred to as communities, they are not equivalent to Peterson‐type communities since they are not particularly discrete and there is some overlap in species composition. The similarity in species between stations was measured by percentage similarity coefficients using Jaccard's coefficient for presence‐absence data and Czekanowski's coefficient for log‐transformed quantitative data. Stations were grouped in dendrograms by group‐average sorting which allowed re‐arrangement of the similarity matrices into trellis diagrams.

Dominant species in each of the four groups of stations were ranked by calculating a ‘community score’ for each, based on its abundance, fidelity, and bioindex value within the group. Each of the four groups was found to support a unique group of species and these are considered as representing four communities. Two indicator species in each community were identified from the highest community scores: Group 1, the Microcosmus/Nolomithrax community — associated with a coarse sediment of dead bivalve shells and small rocks in shallow water. It has high species diversity indices; Group 2, the Halicarcinus/Bugula community— associated with a relatively coarse sediment of dead shells, grit, and little sand in deep water in the main channels; Group 3, the Amalda/Myadora community—associated with fine sand with mud or shell grit in shallow parts of the channels; and Group 4, the Fellaster/Pagurus community — associated with ironsand in shallow water in the outer harbour. It has low species diversity indices.     

Macrofauna along the Sudanese Red Sea coast: potential effect of mangrove clearance on community and trophic structure

Mangroves along the Sudanese Red Sea coast are under constant anthropogenic pressure. To better understand the influence of mangrove clearance on the intertidal benthic community, we investigated the composition, biodiversity and standing stock of the macrofauna communities at high‐, mid‐ and low‐water levels in three contrasting habitats: a bare sand flat, a cleared mangrove and an intact mangrove. In addition, a community‐wide metric approach based on taxon‐specific carbon and nitrogen isotope values was used to compare the trophic structure between the three habitats. The habitats differed significantly in terms of macrofaunal standing stock, community composition and trophic structure. The high‐ and mid‐water levels of the intact mangroves showed a distinct macrofaunal community characterized by elevated densities and biomass, largely governed by higher decapod and gastropod abundances. Diversity was similar for cleared and intact mangroves, but much lower for the bare sand flat. Community‐wide metrics indicated highest trophic diversity and community niche breadth in the intact mangroves. Differences between the cleared and intact mangroves can be partly attributed to differences in sediment characteristics resulting from mangrove clearance. These results suggest a significant impact of mangrove clearance on the macrofaunal community and trophic structure. This study calls for further investigations and management actions to protect and restore these habitats, and ensure the survival of this ecologically valuable coastal ecosystem.     

Short-term bacterial reactivity of nitrogen-enriched seawater of a eutrophic lagoon

We carried out, in September, a 24 h experiment to determine the potential reactivity of bacterial communities found in the sea water in Arcachon Basin (France). To create eutrophic systems, batches of seawater were enriched with 30 mgl^?1 of either ammonium chloride or amino acids. Samples were taken every 3 h. Quantitative measurements were made of direct counts (AODC), biomass and ATP content. The heterotrophic bacterial communities were defined in terms of their catabolic potentialities and ‘specific’ diversity. Bacterial heterotrophic activity was established by measuring heterotrophic uptake and the mineralization percentage of labelled glucose or amino acids. From these data, ratios of AMP/ATP and P/B were calculated where P is the uptake of labelled substrate and B is the biomass.After the nitrogen enrichment an increase of the respiration was seen at first. After 6 h, a biomass peak appeared associated with a continuous increase in the number of cells. Bacterial growth was concurrent with a qualitative modification of the community: UAI increased, and diversity dropped. A less diversified community resulted suggesting an immature ecological state (zymogenous bacterial). Low values of respiration percentage (20%) characterized high growth yields.     

Macrobenthic community structure of soft-bottom sediments at the Belgian Continental Shelf

Within the frame of different research projects, a large number of sites at the Belgian Continental Shelf (BCS) have been sampled for the macrobenthos between 1994 and 2000. These samples cover a diverse range of habitats: from the sandy beaches to the open sea, from the gullies between the sandbanks to the tops of the sandbanks, and from clay to coarse sandy sediments. To investigate the large-scale spatial distribution of the macrobenthos of the Belgian Continental Shelf, the data of all these research projects—728 samples—were combined and analysed. By means of several multivariate techniques, 10 sample groups with similar macrobenthic assemblage structure were distinguished. Each sample group is found in a particular physico-chemical environment and has a specific species composition. Four sample groups differ drastically, both in habitat and species composition, and are considered to represent four macrobenthic communities: (1) the muddy fine sand Abra alba–Mysella bidentata community is characterized by high densities and diversity; (2) the Nephtys cirrosa community occurs in well-sorted sandy sediments and is characterized by low densities and diversity; (3) very low densities and diversity typify the Ophelia limacina–Glycera lapidum community, which is found in coarse sandy sediments and (4) the Eurydice pulchra–Scolelepis squamata community is typical for the upper intertidal zone of sandy beaches. These macrobenthic communities are not isolated from each other, but are linked through six transitional species assemblages. The transition between the A. alba–M. bidentata community and the N. cirrosa community is characterized by a reduction in the mud content and is dominated by Magelona johnstoni. The transition between the N. cirrosa and the O. limacina–G. lapidum community is distinctive by decreasing densities and coincides with a gradual transition between medium and coarse sandy sediments. From the N. cirrosa to the E. pulchra–S. squamata community, transitional species assemblages related to the transition from the subtidal to the intertidal environment were found. Each community or transitional species assemblages was found over a specific range along the onshore–offshore gradient, four types can be discerned: (1) almost restricted to the near-shore area, but possible wider distribution; (2) distributed over the full onshore–offshore gradient; (3) restricted to the near-shore area and (4) restricted to the sandy beach environment. The diversity pattern on the BCS follows this division, with species rich and poor assemblages in the near-shore area to only species poor assemblages more offshore. The distribution and diversity patterns are linked to the habitat type, distinguished by median grain size and mud content.     

循环水养殖黑鲷(Acanthopagrus schlegelii)水体中循环率对水质因子和细菌群落多样性的影响

为探讨循环水养殖系统中循环率对水质因子和细菌群落多样性的影响,以黑鲷(Acanthopagrus schlegelii)为研究对象,研究了4次/天(低循环率)、8次/天(中循环率)、12次/天(高循环率)三个流量下,养殖桶和生物过滤桶两部分细菌群落结构、多样性以及细菌群落与环境因子的相关性。高通量测序结果表明:黑鲷循环水养殖中优势细菌类群为变形菌门(Proteobacteria)、拟杆菌门(Bacteroidetes)、放线菌门(Actinobacteria)、疣微菌门(Verrucomicrobia)和厚壁菌门(Firmicutes)。流量的升高可增加系统的细菌多样性,且高循环率过滤桶中具有净化水质降低营养盐功能的有益菌属更为多样化及丰度更高,同时,其系统去氨氮和总氮效果更好,去除率分别是49.5%和22.3%,氨氮去除率是低循环率组的2.9倍和中循环率的3.6倍,总氮去除率是低循环率组的8.2倍和中循环率组的20.5倍。PCoA分析和聚类分析结果表明,各实验组养殖桶与生物过滤桶中细菌群落组成有着明显的差异,中、高循环率组过滤桶菌落结构与低循环率的有明显的差异。环境因子与细菌群落结构相关性分析结果表明,总磷、活性磷酸盐、亚硝酸盐和总氮等指标对细菌群落结构影响相对较大,但未发现两者间有很显著的相关性。     

Sediment-related distribution patterns of nematodes and macrofauna: two sides of the benthic coin?

We investigated the sediment-related distribution of both nematodes and macrofauna on the Belgian part of the North Sea (Southern Bight of the North Sea) in order to evaluate whether both faunal groups reflect similar patterns in community composition and diversity. Fine-grained sediments (median grain size <200μm) were inhabited by nematode communities characterised by a low diversity and dominated by non-selective deposit-feeding nematodes. Nematode communities from coarser sediments were significantly different in terms of community composition and diversity. Moreover, all nematode feeding types were present in coarser sediments. These differences were explained by the contrasting biogeochemical processes prevailing in both sediment types, rather than granulometry and food availability per se. Macrofaunal distribution patterns were different from those of the nematode communities and seem to be related to water column processes (SPM loading, food availability, hydrodynamic stress) that promote the establishment of diverse communities in the coarser sediments but not in the finest sediments. This suggests that data on nematodes and macrofauna reveal different, complementary aspects of the factors structuring the benthic ecosystem that can be of importance in assessing the ecological status of the seafloor.     

Three main stressors acting on the Ria Formosa lagoonal system (Southern Portugal): Physical stress, organic matter pollution and the land–ocean gradient

During the last 15 years of the 20th century, several researchers carried out extensive sampling of benthic macrofauna communities in the Ria Formosa lagoon. The main objective of this paper is to discern the main communities of benthic fauna of the Ria Formosa and the leading stressors that limit them based on this large data set.The high species richness and high diversity values observed at most of the stations or groups of stations indicate a good ecological status, with the exception of the sewage-impacted areas and the physically stressed areas. It was possible to define three main stressors acting on the Ria Formosa. The most important is the physical stress imposed by the limited water renewal in some areas of the Ria Formosa. The second is the nutrient and organic matter pollution that is limited to the vicinity of the sewage outfall stations and to some locations of the Ria Formosa. This is due to the dual effects of the low residence time of water, but also due to a degradation of water quality in places of relatively restricted water circulation but with high primary production, symptoms of eutrophication. The third stressor is the natural land–ocean gradient, denoting the influence of seawater exchanges and emersion time, attenuated by the high water exchange rates of Ria Formosa.It was possible to differentiate the anthropogenic stress from the natural physical stress through the application of multivariate analysis. However, both structural (species richness and diversity indices) and functional indicators (trophic composition) indicate the same trend – low species richness, low diversity indices, and a community dominated by detritivores species at the locations characterized by high anthropogenic impact or by physical stress. The physically stressed areas were dominated by chironomid larvae and hydrobiid gastropods and the most polluted areas were dominated by oligochaetes, mainly tubificids.     

长江口3个不同生态系的浮游植物群落

初步研究表明 ,长江口及邻近海域存在 3个不同的生态系 ,与以盐度划分的水团 (长江河口水、长江冲淡水、外海水 )基本一致 ,每个生态系包含 1个浮游植物群落。 1997～ 2 0 0 0年的 7个航次调查中共鉴定出浮游植物 393种 ,其中大部分为硅藻。长江口的浮游植物基本可归为 5个类群 :淡水类群、河口半咸水类群、近岸低盐性类群、外海高盐类群、海洋广布性类群。它们自西向东在 3个生态系中有明显的分布格局 ,并且随着长江径流量的变化而摆动和变化。根据栖息水域的盐度浮游植物可分为 3个群落 :河口群落、冲淡水低盐群落、外海高盐群落。     

Diversity patterns of free‐living marine nematodes in the southwest continental shelf off Bay of Bengal and their link to abiotic variables

Marine sediments in continental shelf ecosystems harbor a rich biodiversity of benthic communities. In this study, the spatial and temporal diversity and community assemblages of free‐living marine nematodes were studied by sampling at six depths and over 3 years from the southwest continental shelf off Bay of Bengal, one of the least explored tropical shelf ecosystems. The dominant marine nematode species were related with abiotic variables as part of this study. The effects of sediment granulometry generally decreased with increasing depth and the highest nematode density and species diversity were recorded on coarse sand (shallower depths). Multivariate analysis of the nematode community data showed that community structure differed significantly among depths as well as among years. Statistical analyses showed significant correlations between the nematode community and abiotic variables. Sediment texture, organic matter, water pressure and depth profile were crucial factors for determining diversity, vertical profile and feeding types of the nematode community. Other environmental factors, including anthropogenic pressure, did not have an effect on nematode diversity except for the presence of some tolerant species (Metachromadora spp., Sabatieria spp. and Siplophorella sp.). This study represents a baseline of knowledge of free‐living marine nematode communities that can be used in the future to compare nematode assemblages from temperate shelf ecosystems.     

Relationships between molecular bacterial diversity and chemistry of groundwater in the Wairarapa Valley,New Zealand

Groundwater plays an important role in New Zealand water supplies and hence monitoring activities are conducted regularly. Most monitoring programmes aim to evaluate groundwater chemistry and almost completely overlook the microbial component in this ecosystem. In our present study, the bacterial community structure of groundwater in the Wairarapa Valley was examined using the terminal restriction fragment length polymorphism (T-RFLP), and relationships between bacterial community structure and groundwater chemistry, aquifer confinement and groundwater usage were explored. In addition, the results from this study were compared with a previous T-RFLP survey of the same area in an attempt to detect changes in bacterial community structure over time. The data obtained suggested that bacterial community structure was related to groundwater chemistry, especially to redox conditions. Species composition showed minimal variation over time if groundwater chemistry remained unchanged. These findings reflect the potential of using bacterial communities as biological indicators to evaluate the health of groundwater ecosystems. We suggest that it is important to include this type of broad bacterial diversity assessment criteria into regular groundwater monitoring activities.     

Seasonal changes in community composition and trophic structure of fish populations of five salt marshes along the Essex coastline, United Kingdom

European intertidal salt marshes are important nursery sites for juvenile fish and crustaceans. Due to the increasing threat of habitat loss, the seasonal changes of salt marsh fish communities need to be understood in order to appreciate the ecological and economic importance of the saltmarsh habitat. This study was the first in Great Britain to investigate the seasonal changes of salt marsh fish communities and the variation in community structure between closely located marsh habitats. Between February 2007 and March 2008, five marshes on three estuaries of the Essex coastline were sampled using flume nets to block off intertidal creeks at high tide. Fourteen fish species were caught. The community overall was dominated by three species that made up 91.6% of the total catch: the common goby Pomatoschistus microps (46.2% of the total catch), juvenile herring Clupea harengus (24.3%), and juvenile and larval sea bass Dicentrarchus labrax (21.2%). Cluster analysis demonstrated clear seasonal patterns, with some community structures unique to specific marshes or estuaries. The marsh fish community shifts from a highly diverse community during spring, to a community dominated by D. labrax and P. microps in autumn, and low diversity during winter months. Gravimetric stomach content analysis of fish community identified three main trophic guilds; macroinvertivores, planktivores and omnivores. The macroinvertivore feeding guild contained D. labrax and P. microps, the two most frequently occurring species. This investigation demonstrates the importance of British salt marshes as nursery habitats for commercial fish species.     

Community Structure of Free-living Marine Nematodes in the Area of Agar-Producing Alga Ahnfeltia To b u c h i e n s i s Field (Starka Strait,Peter the Great Bay,East Sea)

The structure of the nematodes communities has been studied in the sediments on two sites located outside and under the layer ofAhnfeltia tobuchiensis (Kanno and Matsubara 1932; Makijenko 1970). Bottom sediments at the stations were represented by sands with a different degree of silting. Specific structure of nematodes at the stations was significantly different under the similar environmental conditions (water depth, dissolved oxygen saturation, salinity, temperature of the bottom layer and organic carbon content inside of the sediment). Nematodes dominated (75.7 %) in meiobenthos community under the layer of A.tobuchiensis where concentration of silt particles was 12 %. Representatives of the family Comesomatidae were dominant. Low index of species diversity and high Simpson domination index were detected in this community. Under a layer ofA. tobuchiensis with the thickness of 30 cm concentration of the silt particles was 5.39 %; nematodes density was low and made 32.1 % of the general density of meiobenthos. Species of the families Xyalidae and Monoposthiidae were dominant. Outside of A.tobuchiensis, field percentage of silt particles was minimal (3.1 %) and representatives of families Cyatholaimidae and Axonolaimidae dominated. The specific structure of nematodes in this type of the ground is characterized by high index of species diversity and low level of domination.     

南长山岛岩岸潮间带底栖藻类群落结构的季节变化格局

南长山岛岩岸潮间带底栖藻类群落的种类组成存在显著的季节差异,4个季节的群落共有种为8种:孔石莼、海黍子、石花菜、江蓠、叉枝藻、小石花菜、叉枝伊谷草和瘤枝凹顶藻。4个季节群落中生物量的变化为:秋季>夏季>冬季>春季。绿藻和褐藻类群主要为暖温性种类,而红藻类群比较复杂,既有暖温带、温带和亚热带性种类,也有寒温带的冷水性种类。4个季节群落的物种优势度序列存在明显的差异,海黍子在春季、夏季和冬季3个群落为第一优势种,瘤枝凹顶藻在秋季为第一优势种。不同季节群落多样性指数变化如下:物种丰富度指数,春季>秋季>冬季>夏季;物种多样性指数,冬季=秋季>春季>夏季;均匀度指数,冬季=秋季>春季>夏季。群落的多样性由红藻类群控制。     

Plankton community diversity from bacteria to copepods in bloom and non-bloom conditions in the Celtic Sea in spring

The plankton community composition comprising heterotrophic bacteria, pro-/eukaryotes, heterotrophic nanoflagellates, microzooplankton and mesozooplankton was assessed during the spring bloom and at non-bloom stations in the English Channel and Celtic Sea between 6 and 12 April 2002. Non-bloom sites were characterised by a dominance of pro-/eukaryotic phytoplankton <20 μm, higher abundance of heterotrophic nanoflagellates, microzooplankton standing stocks ranging between 60 and 380 mg C m⁻², lower mesozooplankton diversity and copepod abundance of between 760 and 2600 ind m⁻³. Within the bloom, the phytoplankton community was typically dominated by larger cells with low abundance of pro-/eukaryotes. Heterotrophic nanoflagellate cell bio-volume decreased leading to a reduction in biomass whereas microzooplankton biomass increased (360–1500 mg C m⁻²) due to an increase in cell bio-volume and copepod abundance ranged between 1400 and 3800 ind m⁻³. Mesozooplankton diversity increased with an increase in productivity. Relationships between the plankton community and environmental data were examined using multivariate statistics and these highlighted significant differences in the abiotic variables, the pro-/eukaryotic phytoplankton communities, heterotrophic nanoflagellate, microzooplankton and total zooplankton communities between the bloom and non-bloom sites. The variables which best described variation in the microzooplankton community were temperature and silicate. The spatial variation in zooplankton diversity was best explained by temperature. This study provides an insight into the changes that occur between trophic levels within the plankton in response to the spring bloom in this area.     

2008年初冷事件对南海北部夏季浮游动物的影响

2008年初,我国南方出现了罕见的低温冰冻极端天气过程。通过对2007年8月和2008年8月南海北部现场调查所获得的数据分析研究了浮游动物种类组成。结果表明,与2007年8月相比2008年8月浮游动物丰度和生物量有很大的下降。聚类分析结果表明浮游动物群落被分为近岸和远海两大类群。浮游动物近岸类群和远岸类群的分界点在不同的时间有所不同,这是由于外海水向近岸的入侵所致。与2007年8月相比,2008年8月浮游动物优势种发生了很大的演替,主要是因为四种浮游动物优势种亚强真哲水蚤、异尾宽水蚤、锥形宽水蚤和小哲水蚤丰度急剧下降所致。相反,水母类和海樽类丰富有很大的升高,其原因可能是2008年春季极端低温导致的鱼类大量死亡所致。与远岸浮游动物群落相比,近岸浮游动物群落变化更剧烈,这说明近岸浮游动物群落结构不稳定。南海北部浮游动物群落结构的变化与2008年初的冷事件有很大关系。     

东、黄海2000年冬季底层鱼类群落结构及其多样性

根据2000年12月～2001年1月东、黄海冬季底层鱼类资源调查资料,分析了该海域的鱼类群落结构。本次调查共捕获鱼类4716.72kg,395796尾,138种。其中,暖水种(WW)居第1位,有81种,占60.00%;暖温种(WT)次之,有53种,占39.26%;冷温种(CT)最少,只有1种,占0.74%。全调查海域的优势种(相对重要性指数QIRI大于500)有5种:带鱼、黄鲫、发光鲷、小黄鱼和鳀;与历史资料相比,优势种个体变小、有被小型鱼类更替的趋势。以质量计算的多样性指数(种类丰富度指数D,Shannon-Wiener多样度指数H′W,种类均匀度指数J′W)呈现由北至南逐渐递增的趋势,而以尾数计算的多样性指数(H′N,J′N)呈现东海北部最高,东海中部次之,黄海南部最低的趋势。生物多样性指数中除种类丰富度指数(D)与水深、海水表温、表层盐度都呈显著性正相关外,而其它生物多样性指数与前述3种环境因子之间的相关性都不显著。单因素方差分析表明,东海北部和中部渔获组成和生物多样性指数都无显著性差别。     

胶州湾浮游植物遗传多样性及其季节变化研究

分别于春、夏、秋三季提取了胶州湾浮游生物总DNA,用PCR方法扩增了浮游植物核酮糖1,5-二磷酸羧化/氧化酶大亚基(rbcL)基因片段,构建了三季节rbcL基因片段质粒文库.随机从各文库中选择约50个克隆,测定了这些克隆的序列.以氨基酸序列相同为标准,共获得59个分类操作单元(OTUs),其中春季特有的21个,夏季特有的13个,秋季特有的23个.有两个OTUs为春、夏季表层海水共有.基于OTU丰度计算的香农氏指数能反映遗传多样性水平.胶州湾春、夏、秋三季的香农氏指数分别为2.69,2.44和2.76,表明秋季胶州湾浮游植物遗传多样性最丰富.春、夏、秋三季浮游植物群落组成差异显著.除夏秋季有两个OTUs相同外,其他OTUs在季节间完全不同.表层海水浮游植物群落结构是动态的,随时间、空间的不同而变化.