Geographical and seasonal variations in biomass and estimated production rates of net zooplankton in Yatsushiro Bay, Japan   总被引：1，自引：1，他引：0  

Miwa Hayashi  Shin-ichi Uye 《Journal of Oceanography》2008,64(6):877-889

The biomass and production rate of net zooplankton were studied at eight stations in Yatsushiro Bay, Japan, monthly from May 2002 to April 2003. Based on environmental conditions, the bay was divided into three regions, viz. northern (average depth, salinity and chlorophyll a concentration: 11 m, 31.8 and 6.5 μg l⁻¹, respectively), central (30 m, 32.8 and 3.2 μg l⁻¹, respectively) and southern (43 m, 33.4 and 1.9 μg l⁻¹, respectively). Net zooplankton biomass was high in warm months and low in cold ones, with annual averages of 20.2, 38.8 and 16.4 mg C m⁻³ in the northern, central and southern regions, respectively. Copepods were the most important constituent (>ca. 70% of net zooplankton biomass) in all regions. The northern region was characterized by the dominance of Oithona spp. in summer and Acartia spp. in winter-spring. In the central region, Microsetella norvegica was most pronounced in summer-fall. In both central and southern regions, Calanus sinicus and Eucalanus spp. dominated in winter-spring and fall, respectively. The annual average net zooplankton secondary production rate was 4.4, 7.5 and 3.9 mg C m⁻³d⁻¹ in the northern, central and southern region, respectively. Combining the results from the present study with those from other collaborative works on microzooplankton allowed us to determine the trophic interactions in Yatsushiro Bay. If the secondary producers depend entirely on phytoplankton for food, their daily carbon requirement is equivalent to 12.5, 21.6 and 19.1% of the phytoplankton biomass in the respective regions.  相似文献   

The Trophic Contributions of Rotifers in Tidal Freshwater and Estuarine Habitats     

G. S. Park  H. G. Marshall 《Estuarine, Coastal and Shelf Science》2000,51(6):729

Distribution patterns and trophic contributions of rotifers from freshwater through polyhaline estuarine waters were examined in the southern Chesapeake Bay and its major tributaries for a two-year period. Trichocerca marina and Synchaeta spp. were the major taxa in abundance, followed by Polyarthra vulgaris, Keratella cochlearis and Brachionus spp. There was a significant negative correlation between salinity and rotifer density, biomass, and number of species. Rotifers were a component of the microzooplankton biomass during specific periods and at particular sites, dominating summer assemblages in tidal freshwater and river–estuary transition sites, plus the winter communities in estuarine waters. This observation indicates that rotifers may play an important trophic role by seasonally replacing metazoan nauplii as a biomass source in both tidal freshwater and estuarine ecosystems. The annual contribution of rotifers to the total microzooplankton biomass exclusive of heterotrophic dinoflagellates was brief but intensive, achieving over 50% of annual biomass during a 2–3 month period. Despite the small annual mean contribution of rotifers to the total microzooplankton biomass, rotifers may have a limited, but significant impact on the trophic dynamics of the zooplankton community in Chesapeake Bay and its major tidal tributaries.  相似文献   

The role of inflow magnitude and frequency on plankton communities from the Guadalupe Estuary,Texas, USA: Findings from microcosm experiments     

Carrie J. Miller  Daniel L. Roelke  Stephen E. Davis  Hsiu-Ping Li  George Gable 《Estuarine, Coastal and Shelf Science》2008

Changes in magnitude and frequency of inflow results in subsequent alterations in the delivery of nutrients essential for phytoplankton growth and competition producing variations in community composition and nutritional value of phytoplankton. Zooplankton demographics are likely directly influenced by pulsed inflows due to flushing losses, whereas they are also indirectly affected by changes in prey quality. In this study, we report the potential effect of pulsed inflows on the plankton community of the Guadalupe Estuary. Microcosms were used that allowed control of light intensity and photoperiod, turbulence, temperature, nutrient loading, and flushing magnitude and periodicity. Our microcosm experiments were novel as they utilized natural plankton communities, thereby allowing the simultaneous interaction between hydrology, resource availability and grazing. Results show differences in microcosms according to magnitude and frequency of flushing. For example, copepod population density was greatest at the annual mean inflow magnitude. At half the annual mean inflow a decline in prey quality likely resulted in poorer grazer performance, and at double the annual mean inflow magnitude increased flushing losses prevented the incidence of higher copepod densities. Similarly, pulsed inflows resulted in greater copepod population densities, higher overall phytoplankton biomass, and dominance of centric diatoms (known to be faster growing and more edible). While reduced freshwater inflow associated with increasing anthropogenic demands often strains the needs of estuarine systems, the effects of reduced river input may be alleviated with several management options including manipulation of the timing, frequency, and magnitude of freshwater inflows. Before implications for management can be discerned from these findings, however, larger scale experiments are needed focus on the roles of inflow magnitude and frequency.  相似文献   

Oxygen Dynamics in a Highly Trophic Aquatic Environment. The Case of Orbetello Coastal Lagoon     

G. Buffoni  A. Cappelletti 《Estuarine, Coastal and Shelf Science》1999,49(6):763

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应用稳定碳氮同位素分析法研究广东流沙湾海域白腹小沙丁鱼的营养级     

杨国欢  侯秀琼  孙省利  陈春亮 《台湾海峡》2011,30(4):467-472

对2008年5—11月采集的广东流沙湾海域白腹小沙丁鱼（Sardinellaclupeoides）进行稳定碳、氮同位素比值的测定,分析比较了5个不同体长组的差异,并以此为基础推算其营养级．结果表明,流沙湾白腹小沙丁鱼的δ^13C值变化范围为一17．61％。一15．99％。,平均值为一16．59‰,与浮游动物的δ^13C均值（一17．27％0）较为相近．其6”N值变化范围为12．73％。～15．26％0,平均值为14．03％0,比浮游动物的6”N均值（10．56％0）高出3．47％0．5个体长组的8¨c、8”N平均值没有随着体长的增大而增大．由δ15N值推算出广东流沙湾海域白腹小沙丁鱼的营养级范围为2．24～3．25,平均值为2．76,符合其主要摄食浮游动物的食性．  相似文献   

An analysis of the trophic network of a macrotidal estuary: the Seine Estuary (Eastern Channel, Normandy, France)     

Herv Rybarczyk  Bernard Elkaïm 《Estuarine, Coastal and Shelf Science》2003,58(4):775

A steady state, mass balance, trophic network has been constructed to illustrate the flow of energy in the Seine Estuary by using Network Analysis and Ecopath methods. This ecosystem shows 15 compartments from primary producers to the top consumers (fish and birds). This study has been compared with other ecosystems of comparable nature located in North America (Narragansett, Chesapeake, Delaware Bays), Europe (Ems Estuary, Dublin Bay and Bay of Somme), and South Africa (Swartkops Estuary) in which analysis of trophic network has been applied with similar methods.The Seine Estuary shows values of some global parameters and indices either close to large North American bays and a South African estuary characterised by the complexity of their trophic network, or values near European bays and estuaries, or else remain typical of the Seine estuary. All of this reflects specific functioning of the Seine Estuary which can be explained by the analysis of the dominant food web. In the upstream sector an important pelagic food web was found correlated with highest primary production, especially planktonic, which is rapidly consumed by an abundant zooplankton and suprabenthos (Mysidacae and Decapoda Crustacea). This reveals the dominant consumer role of this sector. The external fluvial inputs (277.80 gC m⁻² y⁻¹) are transferred to the downstream sector which produces the major export (548.43 gC m⁻² y⁻¹), in parallel with the low consumption and efficiency of dominant benthos component from its bentho-pelagic food web. This reflects the dominant exporter role of this sector.In the Seine Estuary low values of detritivory index D/H (2.52), recycling index FCI (16.1%) and connectance (0.24) were found associated with high values of P/B ratio (38.2%), sum of exports (548.43 gC m⁻² y⁻¹) and the great difference between ratio of ascendency to capacity development A/C and internal ratio A_i/C_i. This shows the lack of a dominant resource as in Delaware Bay, that the state of development is different from a mature ecosystem, and the dependance on external connections similar to the Bay of Somme, another ecosystem of Eastern Channel, France.  相似文献   

Biomass and estimated production rates of metazoan zooplankton community in a tropical coral reef of Malaysia     

Ryota Nakajima  Teruaki Yoshida  Bin Haji Ross Othman  Tatsuki Toda 《Marine Ecology》2014,35(1):112-131

Quantitative research on composition, biomass and production rates of zooplankton community is crucial to understand the trophic structure in coral reef pelagic ecosystems. In the present study, micro‐ (35–100 μm) and net‐ (>100 μm) metazooplankton were investigated in a fringing coral reef at Tioman Island of Malaysia. Sampling was done during the day and night in August and October 2004, and February and June 2005. The mean biomass of total metazooplankton (i.e. micro + net) was 3.42 ± 0.64 mg C·m^?3, ranging from 2.32 ± 0.75 mg C·m^?3 in October to 3.26 ± 1.77 mg C·m^?3 in August. The net‐zooplankton biomass exhibited a nocturnal increase from daytime at 131–264% due to the addition of both pelagic and reef‐associated zooplankton into the water column. The estimated daily production rates of the total metazooplankton community were on average 1.80 ± 0.57 mg C·m^?3·day^?1, but this increased to 2.51 ± 1.06 mg C·m^?3·day^?1 if house production of larvaceans was taken into account. Of the total production rate, the secondary and tertiary production rates were 2.20 ± 1.03 and 0.30 ± 0.06 mg C·m^?3·day^?1, respectively. We estimated the food requirements of zooplankton in order to examine the trophic structure of the pelagic ecosystem. The secondary production may not be satisfied by phytoplankton alone in the study area and the shortfall may be supplied by other organic sources such as detritus.  相似文献   

Seasonal and ontogenetic changes in the diet of blenny Hypleurochilus fissicornis: An estuarine mariculture as a model of the reef environment   总被引：1，自引：0，他引：1  

Bianca Possamai  Luis Fernando Fvaro 《Marine Ecology》2019,40(2)

The Blenniidae family is characterised by small cryptic fish. Due to the small size of these specimens, the sampling is very difficult and information about the ecological role of these fishes is vague. However, mariculture adds reef encrusting organisms that attract blennies, which makes sampling easier. Furthermore, recognising species feeding is critical to understand biological communities. In this study, we evaluated the diet of blenny Hypleurochilus fissicornis in a mariculture, to clarify its influence on the benthic fauna and its interactions with the reef environment. We evaluated the seasonal variation (four seasons chosen by the abiotic variables) and the ontogenic changes (three classes defined by L₅₀ of the species: juvenile, transition and adult) in the diet. Hydrozoans were the main prey, but H. fissicornis fed on a variety of other benthic organisms, exhibiting opportunistic habits. The diet of H. fissicornis was complemented by Amphipods in autumn, Ostracods in winter, and bivalves in summer. Juveniles fed more on Ostracods than the other classes, while the transition class fed mainly on Hydrozoans and a variety of rare items, and adults consumed almost exclusively Hydrozoans and some Cirripedia. Therefore, we conclude that H. fissicornis is an opportunistic feeder and may influence benthic organisms. The establishment of fouling organisms on the mariculture structures allows the use of this area by the blenny, since they promote its feeding base.  相似文献   

基于角质颚碳氮稳定同位素探索茎柔鱼地理种群连通性及其洄游     

刘必林  陈新军  钱卫国  金岳  李建华 《海洋学报(英文版)》2019,38(10):53-59

本文分析了2009、2010和2013年期间采集于哥斯达黎加、厄瓜多尔、秘鲁和智利外海的茎柔鱼的角质颚下颚的δ¹³C和δ¹⁵N含量。各海区的稳定同位素含量反应了不同海区背景值的不同，海区间稳定同位素含量差异显著，其中厄瓜多尔外海最低，智利外海最高。δ¹³C和δ¹⁵N散点图显示，尽管秘鲁海区的同位素值与哥斯达黎加和智利的存在一定的重叠，但是δ13C和δ15N值可明显将各海区的样本明显分开。哥斯达黎加、厄瓜多尔和智利外海样本的δ¹³C和δ¹⁵N值分布相对集中以及三海区之间的δ¹³C和δ¹⁵N值差异显著说明，采自哥斯达黎加、厄瓜多尔和智利外海的茎柔鱼样本属于不同地理群体，它们的产卵起源不同，各自在相对狭小的地理区域内移动，相互之间没有种群交流。与之相比，δ¹³C和δ¹⁵N值变化范围广说明，秘鲁外海茎柔鱼样本的幼体是来自不同海区，经理不同的移动路线和索饵场。秘鲁和智利外海茎柔鱼样本的同位素值存在一定的重叠可能是由于两者之间存在一定的种群交流所致。总体来说，通过分析茎柔鱼角质颚稳定同位素的空间差异有助于我们了解其不同地理种群的迁徙策略以及相互之间的连通性。  相似文献   

非洲沿海国家海洋渔业资源开发利用现状   总被引：1，自引：0，他引：1  

房俊晗  任航  罗莹  张振克 《热带地理》2019,39(2):288-297

根据联合国粮农组织提供的1950-2015年非洲渔获生产统计数据，结合Fishbase提供的相关鱼种营养级（Trophic level, TL）以及Sea Around Us Project Database提供的海洋无脊椎动物营养级，探讨了1950-2015年北非、东非、南非、中非和西非的沿海国家渔获物平均营养级（Mean trophic level, MTL）的变化情况，以此来判定非洲沿海国海洋渔业资源的开发利用现状。结果表明：非洲沿海国家的海洋渔业资源开采大致经历开发不足、快速开发、过度开发阶段，1984-1991年，北非地区的海洋渔业资源遭到一定程度的破坏，高营养级渔业资源渔获量减少了33.5%，MTL由3.44降低到3.25；东非地区渔获量较其他4个区域低，目前，大部分鱼类资源处于充分捕捞利用状态；南非地区在21世纪初发生“捕捞降低海洋食物网”现象，2004-2015年，MTL恢复小幅上升趋势，渔业均衡指数（Fishing-in-balance index, FIB）趋于平稳；2013-2015年，中非地区的MTL与FIB均呈下降趋势，说明产量的增加速度不足以弥补营养级的降低，生态系统结构功能开始遭到破坏；1950-2015年，西非地区的渔获量不断增加，从上世纪60年代开始，过度捕捞现象愈加严重，低营养级鱼类数量占比呈先减少后增加趋势，2001-2012年，MTL波动下降，FIB平稳变化，说明MTL的下降由产量的增加而抵消。21世纪以来，部分北非、南非与西非沿海国家加强了资源管理，渔业资源状况有所好转。研究认为：渔获物平均营养级的下降主要由过度捕捞引起，非洲国家的管理不力加重了过度捕捞现象，建议非洲各国尽快建立起基于渔获物统计的海洋渔业资源实时监测系统，以便掌握捕捞活动下的鱼类群落结构的变动情况。  相似文献