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1.
为了解西沙群岛珊瑚礁海域浮游动物的群落特征, 于2015年5月末至7月初在西沙群岛8个岛礁(七连屿、永兴岛和东岛3个岛屿以及浪花礁、盘石屿、玉琢礁、华光礁和北礁5个环礁)进行了浮游动物采样, 分析了浮游动物的多样性、丰度和群落结构特征, 并比较了5个环礁潟湖内和向海礁坡区浮游动物群落组成的差异。调查海域共鉴定浮游动物180种(包括浮游幼虫13个类群), 其中桡足类最多, 达83种, 其次是水母类(38种)、浮游软体类(14种)、毛颚类(11种)和浮游被囊类(7种); 浮游动物平均丰度为256.4±117.8个·m-3, 桡足类占总丰度的51.08%, 其次是浮游幼虫(16.30%)、浮游被囊类(13.22%)和毛颚类(7.70%)。浮游动物种数、多样性和均匀度指数、丰度在岛屿和环礁之间以及环礁的潟湖区和向海礁坡区均存在差异; 浮游动物多样性和丰度在东岛、玉琢礁和华光礁较高, 而在七连屿和北礁较低; 5个环礁向海礁坡区的浮游动物多样性和丰度皆高于潟湖区的。多元统计分析结果表明调查岛礁的浮游动物可划分两个聚群(相似水平85%); 岛屿近岸及环礁的潟湖群落(Ⅰ)和岛屿远岸及环礁的向海礁坡群落(Ⅱ); 两个聚群浮游动物组成差异较显著(r=0.832, p<0.001); 前者的种数、多样性指数、总丰度和主要浮游动物类群如桡足类、毛颚类和浮游幼虫的丰度显著低于后者。环礁潟湖区和向海礁坡区的空间异质性和生态环境差异可能是导致浮游动物群落结构呈现不同特征的主要因素。  相似文献   

2.
Seasonal and interannual change in mesozooplankton community structure in the offshore Tsushima Current area of the Japan/East Sea was studied in relation to climatic events and temporal variability of the upper water column environment from 1991 to 1999. We observed a clear seasonal succession in zooplankton community structure from a cold-water copepod-dominated community in winter and spring to a gelatinous, carnivorous and warm-water copepod-dominated community in summer and autumn. The mean abundance (inds. m−3) of the spring community was 3–4-fold higher than that of the other season. The spring community structure varied considerably between years: the community characterized by the summer–autumn type zooplankton assemblage appeared in 1991–1993 and 1998, while the community characterized by high abundance of cold-water copepods appeared in the mid 1990s. Time series profiles of water density and nutrients showed the thickness of the surface warm Tsushima Current and the cold subsurface water increased and decreased, respectively, limiting nutrient supply to the surface water in 1992 and 1998. These results suggest that a thick, warm surface layer might reduce the reproductive success and survival ratio of the cold-water copepods both directly and indirectly, by hindering their upward migration to the surface where food is available, and by limiting phytoplankton growth due to nutrient depletion, respectively. A Monsoon Index (MOI) showed weaker winter wind stress in 1992 and 1998, which might have attenuated formation of the cold subsurface layer in the northern Japan/East Sea and been responsible for surface warming of the study area. Since 1992 and 1998 were El Niño years, this study revealed that ENSO related climatic variability on an interannual time scale considerably influenced the lower trophic level ecosystem in the Japan/East Sea.  相似文献   

3.
广东省南澳海域是粤东重要的海产养殖基地, 分析该海域浮游动物群落结构特征对评估其生态环境质量具有重要意义。文章根据2014年9月(秋季)、12月(冬季)、2015年4月(春季)和2016年7月(夏季)在南澳岛东部海域的浮游动物调查, 分析该海域浮游动物的群落结构特征, 探讨环境因素对其时空分布的影响。共鉴定浮游动物206种(包括浮游幼虫), 桡足类种数最多, 达94种; 远岸海域浮游动物的种数高于近岸海域。浮游动物丰度和生物量的季节变化明显, 夏、秋季高于冬、春季; 浮游动物丰度和生物量的分布趋势较一致, 夏季高值区主要出现在近岸, 秋季由近岸向远岸海域递增。浮游动物不同类群和优势种的丰度也存在季节变化, 桡足类是调查期间丰度较高的类群, 秋季水母类和海樽类丰度明显增加; 优势种后圆真浮萤(Euconchoecia maimai)和针刺真浮萤(Euconchoecia aculeata)在夏季丰度高, 小齿海樽(Doliolum denticulatum)在秋季占绝对优势。温度、盐度和浮游植物生物量是影响南澳岛东部海域浮游动物时空变化的主要环境因子, 说明该海域浮游动物群落特征受海流、水团和养殖活动的综合影响。  相似文献   

4.
于2018年8月对海南东、南海域展开断面调查研究,共获取了18个浮游动物样品,分析了浮游动物的种群分布和群落结构变化,旨在了解不同区域珊瑚礁生态系统的结构与功能。结果表明:海南东、南沿岸共鉴定浮游动物43属62种,浮游幼体23类,分为河口类群、暖水沿岸类群和暖水广布类群共三个生态类群,浮游动物种群组成以桡足类占优势,优势种以亚强次真哲水蚤(Subeucalanus subcrassus)、肥胖箭虫(Sagittaenflata)、异体住囊虫(Oikopleuradioica)、长尾类幼体(Macruralarva)、鱼卵(Fisheggs)、双生水母(Diphyeschamissonis)等种类组成。浮游动物个体丰度、物种丰富度和多样性指数等参数均存在区域性差异,整体呈现为三亚琼海文昌,湿重生物量则为琼海三亚文昌。总体而言,三亚珊瑚礁生态系统的健康状况整体优于文昌和琼海地区,浮游动物种类丰富度与多样性整体呈较高水平。  相似文献   

5.
文章根据2016年5月（春季）和8月（夏季）温州沿岸海域浮游动物和环境因子的调查资料,对浮游动物的种类组成、生态类群、优势种、丰度和生物量进行研究,并通过典范对应分析探索环境因子对浮游动物群落特征的影响。研究结果表明:春、夏季共鉴定到浮游动物117种和浮游幼虫20类,大多数种类属于暖水性近海类群;春季的优势种包括中华哲水蚤、大西洋五角水母和百陶箭虫,夏季的优势种包括拟细浅室水母、齿形海萤、肥胖箭虫和精致真刺水蚤等;浮游动物的丰度和生物量春季高于夏季,水平分布大致为近岸低、远岸高;浮游动物样品的季节性差异与表层水温和盐度有较大关系,而影响浮游动物群落结构空间差异的环境因子春季为盐度、活性磷酸盐、硝酸盐和氨氮,夏季为盐度、总氮、总磷和叶绿素a。  相似文献   

6.
Zooplankton surveys were carried out on November 2-3 and December 8-10, 2001 at 12 stations in the Nan Wan Bay of Taiwan, China. Altogether 92 quantitative zooplankton samples were collected from subsurface water and bottom water layers with two conical plankton nets （180 cm in length, 45 cm in opening diameter, 333μm and 200 larn in mesh size）. A total of 31 species of Siphonophores were identified, among them 7 species are new records in the waters around Taiwan Island, of which Rocacea cymbiformis is a new record in China. Dominated by Chelophyes appendiculata, Bassia bassensis, Diphyes bojani, Diphyes dispar, Abylopsis eschscholtzi and Chelophyes contorta, these species accounted for over 76 % and 63 % of the total abundance in November and December. The species number and Siphonophores abundance in December （25 species, 1.99 inds/m3） were more than those in November （19 species, 0.438 inds/m3）, and they were more in the surface water layer than in the bottom layer at most sampling stations. In early winter, the offshore high salinity water mass was a main factor influencing the distribution. The sampling efficiency for two plankton nets is discussed and the seasonal variation of species number and abundance in the Nan Wan Bay is compared with that in the neighboring waters.  相似文献   

7.
A continuous survey examined short-term variations in the zooplankton community and physical ocean environment from the northeastern Izu Islands to Boso Peninsula in Japan. High copepod abundance and small upwellings in the surface layer and salinity minimum layer in the subsurface were observed on the north side of coastal fronts in the westernmost transect, moving southward as the Kuroshio Current left the Boso Peninsula. Thus, the salinity minimum layer might be a key factor forming upwelling and the fronts, leading to large abundance of coastal copepods off the northeastern Izu Islands. A community structure analysis of calanoid copepods revealed an intermediate belt assemblage between coastal and offshore (Kuroshio) assemblages. Copepod abundance was remarkably low and Ctenocalanus vanus dominated (nearly 37%) in the intermediate belt zone, indicating that C. vanus has a relatively high tolerance to adverse environments for calanoid copepods. As the Kuroshio Current left the Boso Peninsula, the coastal assemblage expanded in the same direction, and the intermediate belt assemblage off the northeastern Izu Islands disappeared. The largest population of Calanus sinicus was found along the two western transects off the northeastern Izu Islands (>1000 m depth), which was assumed to be transported from Sagami Bay and advanced southwestward while growing from copepodite stages CIII to CV. Larvae of C. sinicus would be an important food for fish larvae in addition to Paracalanus parvus s.l., the numerically dominant species in the coastal assemblage, and C. vanus under the adverse conditions for coastal copepods.  相似文献   

8.
Cape hake in Namibian waters are demersal and mesopelagic spawners, spawning peaking offshore between 100 and 400 m deep, depending on local environmental conditions. The cross-shelf circulation, low-oxygen layers and mesoscale gyres are three important environmental factors influencing hake spawning behaviour and subsequent transport of the spawning products. Normally, hake spawn offshore near the bottom at depths of 150–400 m. However, during one cruise, spawning was concentrated below several subsurface mesoscale gyres, resulting in reduced dispersion of the eggs and larvae. When the low-oxygen layer above the bottom is pronounced, hake spawning has been observed close to the top of the layer at oxygen concentrations as low as 0.2–0.3 m? ??1. The relatively small size of the eggs and their high specific gravity make them ascend quite slowly from the spawning depths, 10–40 m per day. Consequently, hake eggs spawned deeper than 200 m hatch before they reach the upper mixed layer. The newly hatched larvae are relatively undeveloped, without functional eyes or mouth, and display little swimming activity during their first hours, but laboratory observations have revealed subsequent periods of downward swimming activity. Based on current field observations, on buoyancy measurements of eggs and larvae and on observed larval behaviour, it is concluded that hake eggs and larvae are transported onshore by features of the upwelling subsurface circulation that compensate for offshore movement of surface water. This may be the basic mechanism concentrating early juvenile hake nearshore. Spawning activity near the low-oxygen layer might be a behavioural adaptation to minimize egg predation, because few other species are expected to survive such low concentrations of oxygen.  相似文献   

9.
《Oceanologica Acta》1998,21(1):95-104
A hydrographic and zooplankton survey (neuston and water column) was performed over the Blanes submarine canyon (western Mediterranean) in June 1993. Abundance of fish and crab larvae was very low when compared with previous studies conducted in the same area. The horizontal distribution of fish and crab larvae whose adults inhabit the continental shelf was restricted to the coast. The offshore occurrence of low-salinity waters of continental origin, together with the absence of a component perpendicular to the coast in the system of currents observed throughout the study area, support the observed pattern of distribution. The occurrence of mesopelagic fish larvae and of the oceanic neustonic isopod Idotea metallica in some coastal stations may be associated with episodic inshore-offshore exchanges of water masses identified by drifting buoy trajectories.  相似文献   

10.
Vypeen, an island of Cochin estuarine system, acts as the spawning site of several marine and estuarine fishes. We assumed that, physical process(upwelling) make changes in hydrography and the production of chlorophyll a in coastal waters off Vypeen. These alterations can influence the zooplankton abundance and copepod community structure in that area. For justifying this hypothesis, samples were collected from Vypeen at 10 m and 30 m locations during January(pre-southwest monsoon), August(late-southwest monsoon) and November(postsouthwest monsoon) 2014. During August, subsurface water column was cool, nutrient rich and less oxygenated(signatures of upwelling) than in November and January. Maximum concentrations of nitrate and chlorophyll a were recorded during August. In the present study, 15 zooplankton groups were recorded; of which copepods were the most predominant group(73%–90%). Copepod density in the present study ranged between 527.2 ind./m~3 and 5 139.2 ind./m~3. Totally, 37 copepods species were reported in present study and copepod species richness was higher during January. The abundance of zooplankton and copepods was high in August during late-southwest monsoon. These variations were closely associated with the coastal upwelling in August and weakening of moderate upwelling in November. In SIMPER analysis, it was found that the copepods species distribution was similar within season and dissimilar between the three seasons. Moreover, the higher abundance of upwelling indicator species Temora turbinata was recorded in August, which confirms the signs of seasonal upwelling in Vypeen. The present study emphasized on the influence of hydrographical parameters associated with physical process, in governing the copepod community organization of the Vypeen Island.  相似文献   

11.
Mesozooplankton biomass, species composition, abundance, and vertical distribution were determined along a transect from the continental slope off the west coast of Canada to Ocean Station Papa (OSP) in the open-ocean waters of the NE subarctic Pacific as part of the Canadian Joint Global Ocean Flux Study of this area. All of these measurements had distinct seasonal patterns. At OSP biomass peaked in spring, coincident with the annual biomass maximum of large copepods of the genus Neocalanus. Early copepodites of these copepods were present in surface waters at all stations along the transect in winter, but N. plumchrus and N. flemingeri copepodites were only at the offshore stations in spring. This indicated that these large copepods had completed the growth phase of their life cycle slower in the open ocean than closer to shore where they had already descended to deep water by May or June. Summer biomass was low compared to the spring peak. The summer mesozooplankton abundance was similar to the springtime abundance, but the composition had changed from large-bodied copepods in the spring to small copepods and fewer non-copepod taxa in the summer, which accounts for the reduction in total biomass. Winter biomass was the lowest of the year. Winter species composition was similar to summer except for the appearance of juvenile stages of the genera Neocalanus and Calanus. Diel changes in biomass in the upper 150 m were found in summer but not in winter or spring. Vertical distributions of copepods were often distinct, with closely related species occupying different depth strata. Measurements of wet weight at OSP were higher than the long-term mean wet weight during winter and spring, and lower during summer.  相似文献   

12.
A time series of zooplankton sampling carried out at Station 18 off Concepción (36°S, 73°W) from August 2002 to December 2003 allowed the study of annual life cycles of the copepods Calanus chilensis and Centropages brachiatus in association with environmental variability in the coastal upwelling zone. Changes in the abundance of eggs, nauplii, and copepodids were assessed from samples taken at a mean time interval of ca. 20 days. Upwelling variability in near-surface waters was reflected in seasonal changes in salinity, water column stratification, and oxycline depth, as well as a weak seasonal signal in sea surface temperature (1-2 °C). Both copepods exhibited similar life cycles, characterized by continuous reproduction throughout the year. Estimates of generation times, as a function of temperature, were 25-30 days for C. chilensis and 27-35 days for C. brachiatus, predicting about 12 and 10 generations a year, respectively. These estimates were consistent with reproduction pulses observed in the field. It was thus suggested that copepods may grow under non-limiting food conditions in this upwelling area. However, despite continuous reproduction, there were abrupt changes in population sizes along with the disappearance of early naupliar and copepodid stages taking place even during the upwelling season (spring/summer). These changes were attributed to sudden increases in mortality taking place in spring or early summer, after which the populations remained at low levels through the fall and winter. It is thus suggested that, in addition to variability in the physical environment, biological interactions modulating changes in copepod mortality should be considered for understanding copepod life cycles in highly productive upwelling systems.  相似文献   

13.
The surface and sub-surface biological oceanography of tuna fishing grounds within the East Australian Current (EAC) was compared in 2004 with two other fishing areas further offshore. Our aim was to determine whether the biological oceanography of the region could explain the distribution and intensity of pelagic fishery catches inside and outside the EAC at that time. The EAC fishing area was noticeably warmer, less saline and lower in nutrients than waters in the other fishing areas. The EAC waters were dominated by large diatoms, the biomass of which was significantly higher than in the seamount and offshore areas, apparently the result of a cold core eddy beneath the EAC surface filament. Over the seamount and offshore more typical Tasman Sea waters prevailed, although the presence of a relatively deeper oxygen minimum layer over the seamount suggested topographically induced mixing in the area. Notably, sub-surface zooplankton and micronekton biomass was significantly higher around the seamount than in the two other areas. The offshore region was characterised by frontal activity associated with the Tasman front. Micronekton net biomass was generally highest in surface waters in this region. Examination of tuna catch records at that time showed yellowfin tuna (Thunnus albacares) dominated the catches of the EAC, whereas swordfish (Xiphias gladius) and bigeye tuna (Thunnus obesus) were the main species caught offshore. We suggest the yellowfin tuna concentrate in waters that are not only warmer but where prey species are concentrated near the surface. Offshore, deeper living species such as swordfish and bigeye tuna (T. obesus) can take advantage of prey species that are distributed deeper in the water column and along the flanks of the many seamounts in the region, or that are concentrated at fronts associated with the Tasman Front. Although only a snapshot of the region, relatively consistent catch data over time suggests the underlying biological oceanography may persist over longer time periods, particularly during the Austral spring.  相似文献   

14.
Zooplankton are important grazers of primary production within intertidal marshes and are the optimal prey of higher trophic consumers; however, the patterns of their spatial distribution in marsh creeks are rarely reported. The zooplankton in the intertidal creeks with different salinities at Dongtan marshes of the Yangtze River Estuary was surveyed. The mean zooplankton densities in the intertidal creeks were 53,638 ind. m−3 in April and 132,916 ind. m−3 in July, respectively, which were as high as in the near-shore subtidal waters of the Yangtze River Estuary. This high abundance implied the important roles of zooplankton in the matter flux between marshes and near-shore waters through complex intertidal creek systems. Zooplankton total densities changed significantly from northern to southern creeks. ANOSIM and CCA analyses revealed that the zooplankton community structure were significantly different among the northern, eastern and southern creeks, and between two sampling seasons. Salinity accounted for most of the spatial variation of zooplankton community, whereas water temperature, chlorophyll a concentration, and pH were the main reasons of the temporal variation observed. Copepods were the most abundant zooplankton group. A total of 24 copepod species, belonging to 15 families and 20 genera, were recorded. Planktonic copepods preferred the northern and eastern creeks, with higher densities in July than in April, while benthic copepods predominated only in the northern creeks in April. Since the role of benthic and planktonic copepods may differ in transporting nutrients in the intertidal creeks, it is suggested that the variations in their distribution may influence the ecological functions of zooplankton in the estuarine matter fluxes both spatially and temporally.  相似文献   

15.
在2011年丰水期(7月)和2012年枯水期(3月),分别对钦州湾的内湾和外湾开展了浮游动物调查,研究了枯水期和丰水期钦州湾浮游动物的种类组成、数量分布和季节变化特征。丰水期和枯水期浮游动物种类数量分别为27种和44种,以优势度指数Y0.02确定的优势种丰水期和枯水期分别为3种和4种。丰水期浮游动物丰度为4.0~133.6ind/m3,平均丰度为50.9ind/m3;枯水期浮游动物丰度为1.2~1 725.0ind/m3,平均丰度为272.2ind/m3。丰水期浮游动物(包含鱼卵仔鱼)生物量为1.7~179.2mg/m3,平均生物量为44.0mg/m3;枯水期浮游动物(包含鱼卵仔鱼)生物量为3.1~3 530.0mg/m3,平均生物量为474.9mg/m3。无论是浮游动物的种类数量、丰度和生物量,均显示出内湾低于外湾的空间分布特征,以及枯水期高于丰水期的变化特征。钦州湾浮游动物的这种季节变化和空间分布特征主要是与浮游植物生物量、贝类养殖、环境的稳定度以及人为干扰等有着密切的关系。  相似文献   

16.
The number and lipolytic activity of neustonic and planktonic bacteria inhabiting estuarine Lake Gardno were determined. Lipolytic bacteria were very numerous in investigated layers of water, accounting for 10–88% of the total number of culturable heterotrophic bacteria. Significant differences were found in the decomposition of individual lipid substrates by bacteria. The highest percentage of neustonic and planktonic strains were able to hydrolyse tributyrin and Tween 85. The least numerous bacteria group was microflora hydrolysing Tween 20 and Tween 40. The activity of lipases synthesized by bacteria from the subsurface layer was higher than that of lipases produced by bacteria isolated from the surface layers. A significant effect of salinity on the activity of lipases has been shown.  相似文献   

17.
In the present study we examine factors that affect the downward flux of biogenic carbon in the NE subarctic Pacific, one of the important high-nutrient-low-chlorophyll (HNLC) regions in the open ocean. We focus on the role of mesozooplankton, since their seasonal peaks in biomass and growth are in phase with the seasonal variations in the downward POC fluxes, whereas phytoplankton biomass is more-or-less uniform year-round. The relative importance of mesozooplankton and algal sinking was examined using the pigment composition of material accumulated in short-term free-drifting sediment traps positioned just below the upper stratified surface layer (ca. 100–200 m). This was compared with the phytoplankton composition in the surface waters, and with the grazing activity (gut pigments and fecal pellet production rates) of the most abundant large copepods. We also examined whether the relationships between the downward flux of carbon and pelagic processes were similar in the coastal, continental margin and offshore HNLC regions of the NE subarctic Pacific, the latter represented by Ocean Station Papa (OSP).Our results show that grazing had a variable impact on the downward flux of biogenic carbon. Carbon-transformed pheopigments (particularly pyropheophorbide a, frequently associated with copepod grazing) represented up to 13% of the total downward POC flux inshore (in May 1996) and 8–9% at OSP in May and February 1996, respectively. This flux of pheopigments was accompanied by a large potential input of fecal pellets from large copepods (as estimated from defecation rates of freshly collected animals) only in May 1996 at OSP, suggesting that pheopigments came from other sources (other herbivores, senescing algae) in February. The larger flux of pheopigments in May was probably related to the abundance of mesozooplankton at that time of the year. During summer (August 1996), both the flux of pheopigments and the potential input of fecal pellets from large copepods were negligible at OSP, consistent with more intense pelagic recycling reported in other studies. Inshore, the flux of carbon-transformed pheopigments was slightly higher than at OSP, and its contribution to the downward POC flux in May 1996 was twice that in August 1996. In contrast, the potential input of feces carbon was higher in August than in May 1996, again suggesting other sources for pheopigments found in the traps. The contribution of sinking phytoplankton to the downward biogenic flux was negligible in summer, when prymnesiophytes (indicated by the presence of 19′-hexanoyloxyfucoxanthin) and pelagophytes (19′-butanoyloxyfucoxanthin-containing) dominated in surface offshore waters. The contribution of sinking algae was maximal (9%) in winter (February 1996) at OSP, when fucoxanthin (mainly a diatom marker) dominated the carotenoid composition in the traps and when the abundance of diatoms in surface waters showed its seasonal maximum for this station. Inshore, the low contribution of diatoms (fucoxanthin) to the sinking fluxes may have resulted from inadequate sampling (i.e. the spring bloom may have been missed).Overall, we conclude that: (a) large copepods significantly influenced the downward POC flux only during spring at OSP; (b) unidentified herbivores (e.g. salps, pteropods) producing pigmented, fast-sinking fecal material likely had an important impact during winter; (c) algal sinking made a small contribution to the downward POC flux (maximum in winter); and (d) neither algal sinking nor mesozooplankton grazing had a significant influence on the downward flux of biogenic material in summer at OSP.  相似文献   

18.
根据2016年3月和9月南海东北部陆坡区浮游动物垂直分层采样, 比较浮游动物种类组成、丰度和生物量的垂直分布和季节变化, 探讨影响其差异的原因。文中共鉴定浮游动物225种, 其中3月和9月分别出现150种和169种; 桡足类种数达132种, 其次是毛颚类和管水母类, 各18种; 浮游动物种数在50~100m水层最高, 一般随水深增加而减少。浮游动物丰度和生物量主要集中在0~100m, 二者在100m以深水层随深度增加而降低, 而水柱生物量在100~1000m占总水柱生物量的60%以上。浮游动物优势种季节和垂直变化明显, 3月近海种如普通波水蚤(Undinula vulgaris)和微刺哲水蚤(Canthocalanus pauper)等在100m以上水层丰度较高; 9月外海种如达氏筛哲水蚤(Cosmocalanus darwinii)和黄角光水蚤(Lucicutia flavicornis)等在100m以浅水层相对于3月丰度增加; 隆线似哲水蚤(Calanoides carinatus)在3月丰度和平均体长高于9月, 并且体长较大者主要分布在深层。浮游动物可分0~100m、100~400m和400~1000m三个群落, 因不同水层种类组成和丰度差异引起。浮游动物丰度和生物量的垂直变化与温度、叶绿素a质量浓度等因子呈显著正相关。南海东北部陆坡浮游动物季节和垂直变化受季风、沿岸流和中尺度涡的影响。  相似文献   

19.
We analyzed long-term (56-year) variations in springtime biomass of the zooplankton of the California Current System from two primary regions sampled by CalCOFI: Southern California (SC) and Central California (CC) waters. All organisms were enumerated from the plankton samples and converted to organic carbon biomass using length-carbon relationships, then aggregated into 19 major taxa. Planktonic copepods dominate the carbon biomass in both SC (59%) and CC (46%), followed by euphausiids (18% and 25% of mean biomass in SC and CC, respectively). Pelagic tunicates, especially salps and doliolids, constituted a higher fraction of the biomass in CC (13%) than in SC (5%). There was no long-term trend detectable in total zooplankton carbon biomass, in marked contrast to a decline in zooplankton displacement volume in both regions. The difference between these biomass metrics is accounted for by a long-term decline in pelagic tunicates (particularly salps), which have a relatively high ratio of biovolume:carbon. The decline in pelagic tunicates was accompanied by a long-term increase in water column density stratification. No other taxa showed a decline over the duration of the study, apart from salps and pyrosomes in SC and doliolids in CC. Some zooplankton taxa showed compensatory increases over the same time period (ostracods, large decapods, and calycophoran siphonophores in both SC and CC; appendicularians and polychaetes in SC). Two tests for ecosystem shifts, a sequential algorithm and the cumulative sum of anomalies (CuSum) approach, failed to detect changes in 1976-1977 in total carbon biomass, displacement volume, or most individual major taxa, suggesting that aggregated biomass is an insensitive indicator of climate forcing. In contrast, both techniques revealed a cluster of step-like changes associated with the La Niña of 1999. The major El Niño’s in the past half century have consistently depressed total zooplankton biomass and biomass of many major taxa in both SC and CC, although such effects are transitory. Much, but not all, of the interannual variability in zooplankton is shared between the Southern and Central California sectors of the California Current System.  相似文献   

20.
根据2013年8月(夏季)和2014年5月(春季)在曹妃甸邻近海域的调查资料,研究了浮游动物群落的种类组成、丰度、生物量、优势种和多样性的时空变化特征,分析了其与环境因子的关系,并结合2004年调查资料对比分析了浮游动物丰度和优势种的变化特征及围填海的影响。结果表明,研究海域浮游动物共鉴定得到31种(类),以桡足类和浮游幼体为主,优势种主要包括双刺纺锤水蚤(Acartia bifilosa)、小拟哲水蚤(Paracalanus parvus)、拟长腹剑水蚤(Oithona similis)和桡足类幼体(Copepodid larva)等。春季的浮游动物丰度和生物量均高于夏季,多样性和均匀度指数均低于夏季。浮游动物丰度的空间分布主要受温度、叶绿素a(Chl-a)等环境因子影响,春季基本为近岸高、远岸低的空间分布规律,夏季则相反,基本为近岸低、远岸高的空间分布规律。与2004年相比,本次调查春季和夏季的浮游动物丰度明显下降,可能与浮游植物丰度及DIP浓度降低有关。春季,西侧、东侧海域的浮游动物丰度分别明显降低、升高,与围填海后营养盐重新分布促进了东侧海域浮游植物增殖有关。夏季则主要受河流输入影响,浮游动物丰度的变化不具有空间差异。  相似文献   

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