首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
依据2010年4月、7月和11月对浙江中部近海上升流海域进行的海洋调查资料,运用定量、定性方法,探讨了上升流对该海域浮游动物生态类群分布的影响.结果表明:3个季节共鉴定浮游动物64种,桡足类占主要优势,包括5个生态类群,分别是暖温带近海种、暖温带外海种、亚热带近海种、亚热带外海种和热带大洋种.在种类数组成上,春季以暖温带近海种为主,夏季则是亚热带近海种和亚热带外海种居多,秋季也是亚热带种居多,其中夏季暖温带种种类数要高于春季和秋季,这一现象与同时期东黄海沿海有所不同,主要是由于上升流将一些在海洋底部度夏的暖温种带至海洋表面造成的.此外,3个季节生态类群都是以近海种为主,表明沿岸流是影响这一海域的最主要的水团.在丰度组成上,4月暖温带近海种占总丰度的98.79%,7月暖温带近海种也是组成丰度的重要部分,10月则是亚热带近海种丰度最高.丰度组成所反映的规律与种类数组成规律一致.上升流的存在导致夏季近海暖温带种大量出现,是影响这一海域浮游动物生态类群组成的重要因素;受长江径流和椒江径流的影响,近海种成为主要生态类群,是这一海域浮游动物的一个重要的生态特征.  相似文献   

2.
The relative importance of small forms of copepods has been historically underestimated by the traditional use of 200?C300-??m mesh nets. This work quantified the distribution and abundance of copepods, considering two size fractions (<300???m and >300???m), in superficial waters (9?m deep) of the Drake Passage and contributed to the knowledge of their interannual fluctuations among three summers. Four types of nauplii and eleven species of copepods at copepodite and adult stages were identified, with abundance values of up to 13 ind L?1 and 28,300???g C m?3. The <300-??m fraction, composed of Oithona similis, small cyclopoids and nauplii, dominated the copepod communities in the 3?years; it accounted for more than 77% of the total number and for between 40 and 63% of the total biomass. Changes in density and biomass values among the three cruises differed according to copepod size fraction and water mass; the >300-??m fraction showed no changes among the 3?years, both in Antarctic (density and biomass) and in Subantarctic waters (density), whereas the <300-??m fraction showed higher (density and biomass) values in 2001 both in Subantarctic and in Antarctic waters. Sea surface temperature and its anomaly accounted for the largest proportion of variability in copepod density and biomass, particularly for the <300-??m fraction.  相似文献   

3.
The aim of this study was to examine the community structure and vertical micro‐distribution of testate amoebae and ciliates in a raised bog in eastern Poland, as well as to assess the influence of potential food resources (Chl‐a, bacteria, heterotrophic flagellates) and predators (rotifers and copepods) on protozoa communities. Samples were taken from surface, bottom and interstitial waters. At each type of micro‐habitat and each sampling date water was sampled using a plexiglass corer or mini‐piezometers. Additionally, in order to evaluate grazing pressure, field enclosures were used in which metazoan abundance and composition was manipulated by size‐fractionation. Over experiments, metazoan populations shifted from dominance of rotifers to copepods. In the first experiment, with rotifers dominating, metazoa had only a modest predatory impact on the protozoa. In contrast, the second experiment, with copepods prevailing, demonstrated a clear top‐down control of the protozoa communities by metazoan. The density and biomass of protozoa significantly differed between the studied stations, with the lowest numbers in the interstitial water and the highest in the surface water. Surface sampling were dominated by mixotrophic taxa, whereas the deepest sampling level was characterized by increase in the proportion of bacterivore species. These differences between micro‐habitats may be due to differences in environmental conditions (food resources and grazing pressure). Ordination analysis revealed that bacteria can strongly regulate the abundance and taxonomic composition of protozoa in the bottom and interstitial waters. Metazoan predators could be the main regulators of protozoa communities in surface water. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

4.
Western boundary currents (WBCs) redistribute heat and oligotrophic seawater from the tropics to temperate latitudes, with several displaying substantial climate change‐driven intensification over the last century. Strengthening WBCs have been implicated in the poleward range expansion of marine macroflora and fauna, however, the impacts on the structure and function of temperate microbial communities are largely unknown. Here we show that the major subtropical WBC of the South Pacific Ocean, the East Australian Current (EAC), transports microbial assemblages that maintain tropical and oligotrophic (k‐strategist) signatures, to seasonally displace more copiotrophic (r‐strategist) temperate microbial populations within temperate latitudes of the Tasman Sea. We identified specific characteristics of EAC microbial assemblages compared with non‐EAC assemblages, including strain transitions within the SAR11 clade, enrichment of Prochlorococcus, predicted smaller genome sizes and shifts in the importance of several functional genes, including those associated with cyanobacterial photosynthesis, secondary metabolism and fatty acid and lipid transport. At a temperate time‐series site in the Tasman Sea, we observed significant reductions in standing stocks of total carbon and chlorophyll a, and a shift towards smaller phytoplankton and carnivorous copepods, associated with the seasonal impact of the EAC microbial assemblage. In light of the substantial shifts in microbial assemblage structure and function associated with the EAC, we conclude that climate‐driven expansions of WBCs will expand the range of tropical oligotrophic microbes, and potentially profoundly impact the trophic status of temperate waters.  相似文献   

5.
Williams  R.  Conway  D. V. P.  Hunt  H. G. 《Hydrobiologia》1994,292(1):521-530
The European shelf seas can be divided into regions which have tidally mixed waters and thermally stratified waters. The tidally mixed near shore environments support zooplankton communities dominated by smaller copepods and having large meroplankton contributions. These small copepods (Centropages spp., Temora spp., Acartia spp., Paral Pseudo/Microcalanus spp.) together with the microzooplankton component form a different and more complex food web than the larger copepod/diatom link associated with thermally stratified waters. The copepods Calanus finmarchicus and C. helgolandicus account for over 90% of the copepod dry weight biomass in stratified waters. Although occurring in lower numbers in mixed waters they can still make significant contributions to the biomass. A 31 year time series from the European shelf shows the inter- and intea-annual variability of these species. The basic biology and food web that these two systems support, and the transfer of energy, can result in marked differences in quantity and quality of particulates available as food for fish larvae. Calanus dominated systems allow the primary production to be directed straight through the trophic food chain (diatoms/Calanus/fish larvae) while the near shore communities of smaller copepods limit the amount of energy being transferred to the higher trophic levels. Eighty-two Longhurst Hardy Plankton Recorder hauls were used as the data base for this study. In all cases the zooplankton was dominated by copepods both in numbers and biomass accounting for > 80% of total zooplankton dry weight in the Irish Sea, Celtic Sea, shelf edge of the Celtic Sea and the northern and southern North Sea in Spring.  相似文献   

6.
Climate warming has been linked with changes in the spatiotemporal distribution of species and the body size structure of ecological communities. Body size is a master trait underlying a host of physiological, ecological and evolutionary processes. However, the relative importance of environmental drivers and life history strategies on community body size structure across large spatial and temporal scales is poorly understood. We used detailed data of 83 copepod species, monitored over a 57-year period across the North Atlantic, to test how sea surface temperature, thermal and day length seasonality relate to observed latitudinal-size clines of the zooplankton community. The genus Calanus includes dominant taxa in the North Atlantic that overwinter at ocean depth. Thus we compared the copepod community size structure with and without Calanus species, to partition the influence of this life history strategy. The mean community body size of copepods was positively associated with latitude and negatively associated with temperature, suggesting that these communities follow Bergmann's rule. Including Calanus species strengthens these relationships due to their larger than average body sizes and high seasonal abundances, indicating that the latitudinal-size cline may be adaptive. We suggest that seasonal food availability prevents high abundance of smaller-sized copepods at higher latitudes, and that active vertical migration of dominant pelagic species can increase their survival rate over the resource-poor seasons. These findings improve our understanding of the impacts that climate warming has on ecological communities, with potential consequences for trophic interactions and biogeochemical processes that are well known to be size dependent.  相似文献   

7.
Range shifts of tropical marine species to temperate latitudes are predicted to increase as a consequence of climate change. To date, the research focus on climate‐mediated range shifts has been predominately dealt with the physiological capacity of tropical species to cope with the thermal challenges imposed by temperate latitudes. Behavioural traits of individuals in the novel temperate environment have not previously been investigated, however, they are also likely to play a key role in determining the establishment success of individual species at the range‐expansion forefront. The aim of this study was to investigate the effect of shoaling strategy on the performance of juvenile tropical reef fishes that recruit annually to temperate waters off the south east coast of Australia. Specifically, we compared body‐size distributions and the seasonal decline in abundance through time of juvenile tropical fishes that shoaled with native temperate species (‘mixed’ shoals) to those that shoaled only with conspecifics (as would be the case in their tropical range). We found that shoaling with temperate native species benefitted juvenile tropical reef fishes, with individuals in ‘mixed’ shoals attaining larger body‐sizes over the season than those in ‘tropical‐only’ shoals. This benefit in terms of population body‐size distributions was accompanied by greater social cohesion of ‘mixed’ shoals across the season. Our results highlight the impact that sociality and behavioural plasticity are likely to play in determining the impact on native fish communities of climate‐induced range expansion of coral reef fishes.  相似文献   

8.
In contrast to cold and eurythermal waters, benthic communities of warm brooks in temperate regions have been inadequately studied. In order to investigate the effects of water thermal regime on the benthic communities of warm waters and their relationships with those of cold and eurythermic ones, the macrozoobenthos was studied at eight sites in the Toplica River, and at four sites in its tributary, the Termalni brook. Investigations were carried out seasonally from April 2000 to January 2001. Warm waters of the Termalni brook were characterized by specific macrozoobenthos assemblages that exhibited significant differences to the populations of eurythermal and cold waters of the Toplica River. The dominant taxa in the macrozoobenthos community of warm waters were mainly Gastropoda species. Moreover, benthic communities of warm waters were characterized by lower diversity and greater biomass in comparison with those of cold and eurythermal waters. The gradient of average annual temperatures represented the main ecological factor influencing changes of diversity and biomass along the course of the investigated Termalni brook. Inflow of warm waters at site T6 lead to a decrease in macrozoobenthos abundance and changes in qualitative and quantitative composition of the benthocoenosis of a highland stream, but did not significantly alter diversity.  相似文献   

9.
MK Ekvall  LA Hansson 《PloS one》2012,7(9):e44614
In recent decades temperature elevation has been the focus of many studies on climate change, including effects on planktonic communities, but few studies have examined the effects of increased water color ("brownification"). Since these changes are likely to occur simultaneously, it is important to investigate their potential interactive effects. Accordingly, we performed a mesocosm experiment where we combined a 3°C increase in temperature with a doubling in water color to study how these factors affect zooplankton. In particular, we looked at recruitment of cladocerans and copepods from the sediment in spring, as well as their establishment in the water column. Our results show that an elevated temperature will have considerable effects on recruitment as well as on pelagic abundances of both cladocerans and copepods, whereas increases in water color will have less effects on the recruitment and pelagic establishment. But more importantly, the proportion of cladocerans in the water column, relative to copepods, increased at higher temperature, suggesting that cladocerans benefit more from elevated temperatures than copepods do. Overall, these results likely stem from the combined effect of changes in recruitment and differences in life history between copepods and cladocerans. Taking a wider outlook, this suggests that future climate warming will change the dominance pattern of zooplankton communities in spring, and, in accordance with the experimental data, we here show that cladocerans are more abundant than copepods in natural lake ecosystems during warmer rather than cooler years.  相似文献   

10.
Mesozooplankton abundance, body area spectrum, biomass, gut fluorescence and electron transfer system (ETS) activity were studied in the Antarctic Peninsula during the post-bloom scenario in these waters. Values of abundance and biomass were rather low and decreased sharply from the slope waters to the coastal area. In contrast, specific gut fluorescence and ETS activity were high in the coastal area and decreased through the shelf-break. Large copepods were very scarce, similarly to the post-bloom conditions in phytoplankton where large cells are not abundant and small cells such as flagellates dominate the water column. The vertical distribution showed two well defined layers by day, one at the surface which corresponded to krill organisms and a second at depth (>300 m) formed mainly by the large copepod Metridia gerlachei. During the short night, this layer ascended at the time that krill at the surface migrated to deeper waters as observed from acoustics and net sampling. This observation and the absence of large copepods over the shelf suggest that krill consumption on large phytoplankton cells during the bloom is followed by an increase in predation upon mesozooplankton. It also suggests that krill decrease the abundance and biomass of mesozooplankton over the shelf and continues their predation upon mesopelagic copepods during the post-bloom in Antarctic waters. This behaviour could explain the long ago described impoverishment in mesozooplankton south of the Antarctic Circumpolar Current.  相似文献   

11.
The feeding ecology of the larvae of silver hake Merluccius bilinearis was examined during two time periods (October 1998 and December 1992) on the Western Bank, Scotian Shelf, north‐west Atlantic, and compared with the feeding ecology of Atlantic cod Gadus morhua larvae collected in the same samples in December 1992. During both time periods silver hake exhibited strong selection for late stage copepodids and adult copepods at a small size (>3·5 mm total length, L T). The niche width measured as the diet breadth index ( I DB) of silver hake declined rapidly as they increased in size and remained relatively constant from 3 to 11 mm L T, during each time period. Atlantic cod larvae exhibited a broader niche width that was curvilinear over the same L T. Atlantic cod were also less selective than silver hake, incorporating both naupliar and early stage copepodids in their diets throughout the length classes examined. Simple isometric relationships did not explain the differences in diet, as Atlantic cod larvae continued to feed on early stages of copepods at large size, while silver hake larvae quickly switched to large prey items. The strong selection and narrow I DB observed for silver hake probably reflects adaptation to spawning during the periods between major secondary production peaks in temperate waters.  相似文献   

12.
Zooplankton that are vulnerable to predation by planktivorousfish typically remain in deeper, darker water during the day.Vertical position may be affected by profiles of temperatureand oxygen concentration, but light levels are thought to becritically important. Water transparency in temperate lakesis strongly dependent on the concentration of dissolved organiccarbon (DOC). Therefore, different patterns of zooplankton verticalposition might be expected in lakes that vary in their levelof DOC. The importance of three factors (light, temperatureand oxygen) that might affect vertical position of major zooplanktongroups was evaluated in 10 small lakes located in central Ontario.The lakes, encompassing a wide range of water colour, were sampledin May, June and August of 2000. Small cladocerans were foundto be always higher in the water column than large cladocerans,while copepods were deeper. Small cladocerans had a weak responseto the predictive factors, but copepods and large cladoceranswere strongly affected. The vertical position of copepods wasconsistently dependent solely on Secchi depth. Surprisingly,for large cladocerans, temperature gradient was decisive inMay and June, and only in August was water transparency themost important variable. Overall, water transparency, as determinedby level of water colour, was the most important variable but,depending on taxonomic group and time of year, temperature andoxygen were also major determinants of vertical position.  相似文献   

13.
To assess potential differences in predation impact on zooplankton communities by small (larva) and large 0+ juvenile fish, 18 studies were reviewed from fresh water and the brackish Baltic Sea of the northern hemisphere temperate region. These case studies were performed either in the field or in mesocosm experiments. Larva stocks were found to exert only minor impact on small zooplankton species such as rotifers, copepodids and small cladocerans. In contrast, stocks of 0+ juveniles were found to have the potential to depress populations of large cladocerans and copepods, especially during late summer and autumn. However, studies where both 0+ juvenile fish consumption and zooplankton dynamics and production were exactly quantified are still very rare, and therefore final evaluation of this interaction cannot be made. In addition, papers were summarized that describe differences in morphological and physiological performance between larva and 0+ juvenile fish. The greater impact of 0+ juvenile fish on large zooplankton may be explained by their larger mouth gape and by their better developed abilities to detect and consume their prey items. However, this partly is lessened by the lower energy requirements of juvenile fish compared with identical biomasses of fish larvae, although larva bioenergetics remains only fragmentarily understood. Consequently, selective predation by fish larvae on particular small zooplankton prey may be more important than has been detected so far.  相似文献   

14.
In the Northern California Current (NCC), zooplankton communities show interannual and multiyear shifts in species dominance that are tracked by survival of salmon populations. These zooplankton community changes correlate with the Pacific Decadal Oscillation (PDO) index: a ‘warm‐water’ copepod species group is more abundant during warm (positive) phases of the PDO and less abundant during cold (negative) phases; the reverse occurs for a ‘cold‐water’ species group. The observed relationship led to the hypothesis that the relative dominance of warm/cold‐water copepods in the NCC is driven by changes in the horizontal advection of surface water over different phases of the PDO. To test this hypothesis, variation in surface water advection to coastal regions of the NCC over the period of 1950–2008 was investigated using a Regional Ocean Modeling System (ROMS) and passive tracer experiments, then was compared with zooplankton collected off Oregon since 1996. Results showed that surface water advection varied with the phase of the PDO; the low‐frequency component of advection anomalies strongly correlated with copepod species composition (R>0.9). During positive phases of the PDO, current anomalies were northward and onshore, resulting in transport of warmer waters and the associated copepods into the region. During negatives phases, increased equatorward current anomalies led to a copepod community that was dominated by cold‐water taxa. Our results support the hypothesis that climate‐driven changes in basin‐scale circulation controls copepod community composition in the NCC, and demonstrate that large‐scale climate forcings downscale to influence local and regional ecosystem structure.  相似文献   

15.
Copepod-bacteria interactions include permanent and transient epi- and endobiotic associations that may play roles in copepod health, transfer of elements in the food web, and biogeochemical cycling. Microbiomes of three temperate copepod species (Acartia longiremis, Centropages hamatus, and Calanus finmarchicus) from the Gulf of Maine were investigated during the early summer season using high throughput amplicon sequencing. The most prominent stable component of the microbiome included several taxa within Gammaproteobacteria, with Pseudoalteromonas spp. especially abundant across copepod species. These Gammaproteobacteria appear to be promoted by the copepod association, likely benefitting from nutrient enriched microenvironments on copepods, and forming a more important part of the copepod-associated community than Vibrio spp. during the cold-water season in this temperate system. Taxon-specific associations included an elevated relative abundance of Piscirickettsiaceae and Colwelliaceae on Calanus, and Marinomonas sp. in Centropages. The communities in full and voided gut copepods had distinct characteristics, thus the presence of a food-associated microbiome was evident, including higher abundance of Rhodobacteraceae and chloroplast sequences in the transient communities. The observed variability was partially explained by collection date that may be linked to factors such as variable time since molting, gender differences, and changes in food availability and type over the study period. While some taxon-specific and stable associations were identified, temporal changes in environmental conditions, including food type, appear to be key in controlling the composition of bacterial communities associated with copepods in this temperate coastal system during the early summer.  相似文献   

16.
Here, we evaluate the so‐called Thorson's rule, which posits that direct‐development and larger eggs are favored toward the poles in marine organisms and whose validity been the subject of considerable debate in the literature, combining an expanded phenotypic dataset encompassing 60 species of benthic octopuses with a new molecular phylogeny. Phylogenetic reconstruction shows two clades: clade 1 including species of the families Eledonidae, Megaleledonidae, Bathypolypodidae, and Enteroctopodidae, and clade 2 including species of Octopodidae. Egg size, development mode, and all environmental variables exhibited phylogenetic signal, partly due to differences between the two clades: whereas most species in clade 1 inhabit cold and deep waters, exhibit large eggs and hatchling with holobenthic development, species from clade 2 inhabit tropical‐temperate and shallow waters, evolved small eggs, and generally exhibit merobenthic development. Phylogenetic regressions show that egg size exhibits a conspicuous latitudinal cline, and that both egg size and development mode vary with water temperature. Additionally, analyses suggest that egg size is constrained by body size in lineages with holobenthic development. Taken together, results suggest that the variation in egg size and development mode across benthic octopuses is adaptive and associated with water temperature, supporting Thorson's rule in these organisms.  相似文献   

17.
Bacteria living in the oligotrophic open ocean have various ways to survive under the pressure of nutrient limitation. Copepods, an abundant portion of the mesozooplankton, release nutrients through excretion and sloppy feeding that can support growth of surrounding bacteria. We conducted incubation experiments in the North Atlantic Subtropical Gyre to investigate the response of bacterial communities in the presence of copepods. Bacterial community composition and abundance measurements indicate that copepods have the potential to influence the microbial communities surrounding and associating with them – their ‘zoosphere’, in two ways. First, copepods may attract and support the growth of copiotrophic bacteria including representatives of Vibrionaceae, Oceanospirillales and Rhodobacteraceae in waters surrounding them. Second, copepods appear to grow specific groups of bacteria in or on the copepod body, particularly Flavobacteriaceae and Pseudoalteromonadaceae, effectively ‘farming’ them and subsequently releasing them. These distinct mechanisms provide a new view into how copepods may shape microbial communities in the open ocean. Microbial processes in the copepod zoosphere may influence estimates of oceanic bacterial biomass and in part control bacterial community composition and distribution in seawater.  相似文献   

18.
南汇东滩湿地围垦水域内浮游动物群落结构的变化   总被引:2,自引:0,他引:2  
2010年10月-2011年7月对南汇东滩围垦水域和坝外自然水域的浮游动物进行调查,研究了两水域内浮游动物的种类组成、丰度、生物量、优势种和生物多样性等生态学特征参数的季节变化,并初步探讨了围垦内外水域浮游动物群落的结构差异,及其与盐度、水温和人类活动等环境因子的关系.结果表明:围垦水域和坝外自然水域共检获浮游动物30种,其中围垦水域浮游动物24种,以轮虫的种类数最多;坝外自然水域浮游动物14种,其中桡足类占绝对优势.围垦水域浮游动物的年平均丰度明显高于坝外自然水域,年平均生物量则相反.围垦水域以角突臂尾轮虫、萼花臂尾轮虫和广布中剑水蚤等淡水种为主要优势种,而坝外自然水域则以中华华哲水蚤、火腿许水蚤和虫肢歪水蚤等河口半咸水种为主要优势种,且两水域优势种均存在季节更替.坝外水域浮游动物Shannon多样性指数(H)值和Pielou均匀度指数(J)值均明显高于围垦水域,Margalef丰富度指数(d)值和单纯度指数(C)值低于围垦水域.群落聚类和MDS结果表明,围垦水域浮游动物的群落结构与坝外自然水域存在明显差异.围垦是引起被围水域浮游动物群落结构变化的主要原因,盐度、潮汐动力等是导致动物群落结构改变的主要环境因子.  相似文献   

19.
Patterns of phytoplankton size spectra variation with gradients of environmental stress have been observed in freshwater, transitional waters and marine ecosystems, driving the development of size spectra based assessment tools.In this study, we have tested on transitional and coastal waters a new Index of Size spectra Sensitivity of Phytoplankton (ISS-Phyto), which integrates simple size spectra metrics, size class sensitivity to anthropogenic disturbance, phytoplankton biomass (chlorophyll a) and taxonomic richness thresholds. ISS-Phyto has been tested both among and within ecosystems along pressure gradients based on expert view assessment; the adequacy of symmetric and both left and right asymmetric models of phytoplankton size class sensitivity have been compared.The results showed that ISS-Phyto consistently discriminated between anthropogenic and natural disturbance conditions. Left asymmetric models of size spectra sensitivity, assuming greater disturbance tolerance with respect to eutrophication and organic enrichment of increasingly large size classes, showed the best fit comparing all ecosystems; in three of the four considered ecosystems (Varna, Helsinki, Mompás-Pasaia), they seemed to discriminate best between different levels of disturbance also within ecosystems. Moreover, they demonstrated significant and inverse patterns of variation along the overall pressure gradient as well as along the inorganic phosphorus (DIP), chlorophyll a and trophic index (TRIX) gradients.Therefore, ISS-Phyto, originally developed for transitional waters, seems to be an adequate assessment tool of ecological status also in coastal marine waters; moreover, it seems adequate to describe within ecosystem disturbance gradients. Hence, ISS-Phyto helps to understand the relationships between anthropogenic impact and ecosystem response from the individual point of view, with reference to the simple parameter of body size.  相似文献   

20.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号