海洋桡足类摄食生态及其对浮游植物的摄食压力

该文利用肠道色素法,对中国近海(渤海、黄海、东海、莱州湾、潍河口)和南大洋(普里兹湾及邻近海域)浮游桡足类在自然海区的摄食状况及其对浮游植物及初级生产力的摄食压力进行了研究.主要内容包括:近海:桡足类肠道色素含量随个体的增大而增加,但是肠道排空率与个体大小没有相关性.桡足类通常存在着一定的昼夜摄食节律,摄食高峰出现在夜间,另外河口海区桡足类的摄食节律与潮汐有关.南大洋:南极夏季边缘浮冰区微型浮游动物是浮游植物的主要摄食者,纽鳃樽在形成一定的种群密度时也对浮游植物起到重要的控制作用,而桡足类对浮游植物生物量的变化影响相对较小.

黄海浮游动物功能群的研究

浮游动物在海洋生态系统物质循环和能量流动中起着至关重要的作用。浮游动物物种组成、生物量和次级生产力的变化会改变生态系统的结构和功能。在黄海生态系统中如何描述这个过程，并使它易于模拟是本论文的研究目的。生物量和生产力是海洋生态系统食物网的基础。谁是浮游动物生物量和次级生产力的基础？哪些种类在生态系统中起关键作用？这些问题在黄海这样的温带陆架边缘海区很难回答，原因是物种组成、生物量和生产力的季节变化显著。因此，在对黄海食物产出的关键过程进行模拟时，需要应用既准确又简便的方法来对浮游动物群落的生态过程进行模拟。在对黄海浮游动物群落结构和物理海洋学特征进行充分的分析之后，浮游动物功能群的方法被确定用来进行黄海生态系统结构和功能的模拟。 根据浮游动物的粒径、摄食习性和营养功能，黄海浮游动物被分为6个功能群：大型浮游甲壳动物功能群（Giant crustacean，GC）、大型桡足类功能群（Large copepods, LC）、小型桡足类功能群（Small copepods，SC）、毛颚类功能群（Chaetognaths）、水母类功能群（Medusae）和海樽类功能群（Salps）。GC、LC和SC是按照粒径大小而划分的功能群，他们是高营养层次的主要食物资源。毛颚类和水母类是两类胶质性的肉食性浮游动物功能群，他们与高营养层次竞争摄食饵料浮游动物；海樽类与其他浮游动物种类竞争摄食浮游植物，而本身的物质和能量却不能有效的传递到高营养层次。本文研究报道了浮游动物各功能群的时空分布、基于浮游动物动能群的黄海生态区划分、饵料浮游动物功能群的生产力、毛颚类对浮游动物的摄食压力以及中华哲水蚤（Calanus sinicus）的摄食生态学。 春季，浮游动物生物量为2.1 g m–2，GC、LC和SC对生物量的贡献率分别为19, 44 和 26%。高生物量的LC和SC功能群主要分布于山东半岛南岸的近岸海域，而GC主要分布在远岸站位。夏季，浮游动物的生物量为3.1 g m–2，GC贡献了73%。GC、LC和SC主要分布在黄海的中部海域。秋季，浮游动物生物量为1.8 g m–2，GC、LC和SC的贡献率相似，分别为36, 33和23%，高生物量的GC和LC分布在黄海中部，而SC主要分布在远岸站位。GC和LC是冬季浮游动物生物量（2.9 g m–2）的优势功能群，分别贡献率了57%和27%，高生物量的GC、LC和SC都分布在黄海的中部海域。与GC、LC和SC相比，毛颚类生物量较低，主要分布于黄海的中北部海域。水母类（本文中指小型水母类）和海樽类斑块分布明显，主要分布于黄海沿岸和北部海域。属于不同功能群的约10个种类为浮游动物的优势种，控制着浮游动物群落的动态。 春季，黄海可以被分成4个浮游动物生态区，浮游动物生物量的分布中心位于山东半岛南岸近岸海域，与第一个生态区相对应，LC和SC在分布中心起主要的控制作用；夏、秋和冬季，黄海分别被分成3、4和3个生态区，浮游动物生物量的分布中心均位于黄海的中部海域，均与各季节的第一个生态区相对应，GC和LC是分布中心生态区的优势功能群，对分布中心起主要的控制作用。黄海冷水团（YSCBW）在GC、LC和SC的空间分布模式中起着重要的作用。黄海不同季节浮游动物生态区的空间分布模式及生态区中起控制作用的优势功能群类别有着重要的生态学意义。 我们将饵料浮游动物功能群细化为0.16–0.25 mm、0.25–0.5 mm、0.5–1 mm、1–2 mm和 >2 mm5个粒径组。应用生物能量学的方法研究了不同粒径浮游动物的生产力。结果表明：浮游动物次级生产力5月份最高，为91.9 mg C m–2 d–1，其次是6月和9月，分别为75.6 mg C m–2 d–1和65.5 mg C m–2 d–1，8月、3月和12月较低，仅为42.3 mg C m–2 d–1、35.9 mg C m–2 d–1和27.9 mg C m–2 d–1。根据这些结果，黄海浮游动物年次级生产力为18.9 g C m–2 year–1。0.16–0.25 mm和 0.25–0.5 mm 两个粒径组对浮游动物次级生产力的贡献率为58–79%，即相对应的SC功能群的周转率（P/B, 0.091–0.193 d–1）要高于GC和LC。 黄海毛颚类功能群的优势种类为强壮箭虫（Sagitta crassa）、纳嘎箭虫（S. nagae）、肥胖箭虫（S. enflata）和百陶箭虫（S. bedoti）。我们对这四种箭虫的生产力和对浮游动物生物量和生产力的摄食压力进行了研究。结果表明：黄海毛颚类总的生物量为98–217 mg m–2，总的生产力为1.22–2.36 mg C m–2 d–1。黄海毛颚类的生物量占浮游动物总生物量的6.35–14.47%，而生产力仅占浮游动物总生产力的2.54–6.04%。强壮箭虫和纳嘎箭虫是黄海毛颚类功能群的绝对优势种，控制着黄海毛颚类群落的动态。黄海毛颚类总的摄食率为4.24–8.18 mg C m–2d–1，对浮游动物现存量和生产力总的摄食压力分别为为0.94%和12.56%。黄海冬季，浮游动物的现存量和生产力为0.4 g C m–2和0.026 g C m–2d–1，而毛颚类的摄食压力却达到了全年的最大值，为1.4%和20.94%。因此，毛颚类的摄食可能对冬季浮游动物群落结构造成重要的影响。通过不同体长组箭虫的摄食率可以推断，黄海毛颚类全年主要摄食小型桡足类，对SC功能群的摄食压力最大。但是在夏季黄海冷水团形成的月份，毛颚类对前体长为2 mm的LC功能群中的种类摄食压力也较大，但此时，由于优势种中华哲水蚤进入滞育阶段，因此毛颚类的摄食会对其种群数量造成严重的影响。 中华哲水蚤在春、秋季的摄食率分别为2.08–11.46和0.26–3.70 µg C female–1 day–1，与微型浮游生物的现存量呈显著的正相关。春季，在黄海的北部，中华哲水蚤通过摄食微型浮游生物吸收的碳量能够满足其代谢和繁殖需求，而在黄海的南部和秋季黄海冷水团锋区附近，中华哲水蚤必须通过摄食其他类型的食物资源来维持其代谢和生殖需求。较低的摄食率、无产卵以及种群中CV期桡足幼体占优势表明，秋季中华哲水蚤在黄海冷水团区域内处于滞育状态。中华哲水蚤优先摄食微型原生动物，并且春季中华哲水蚤总的生长效率（GGE, 3–39%）与食物中微型原生动物的比例呈显著的正相关，表明微型原生动物具有较高的营养价值。但是，因较低的产卵率（0.16–12.6 eggs female–1 day–1）而导致的中华哲水蚤较低的总生长效率（13.4%），可能就是由于其食物中的必需营养成分含量不足（或缺乏）造成的。 本文从生物量的角度，对黄海浮游动物各功能群的时空分布、生态区划分进行了研究报道，对GC、LC和SC功能群的生产力、毛颚类对浮游动物的摄食压力和中华哲水蚤的摄食生态学进行了较为深入的研究，这些结果为黄海食物产出的关键过程的模拟提供了基础资料。今后的研究重点应搞清楚黄海水母类对浮游动物次级生产力的摄食压力和海樽类在食物产出模型中产生的负效应的程度，浮游动物各功能群的组成、季节变化和空间分布模式的长期变化，尤其是在气候变化和人类活动的影响下，将是今后研究的重点。

Feeding and respiration rates of a planktonic copepod (Calanus sinicus) oversummering in Yellow Sea Cold Bottom Waters

The distribution, feeding and oxygen consumption of Calanus sinicus were studied in August 2001 on a transect across Yellow Sea Cold Bottom Waters (YSCBW) and two additional transects nearby. The distribution of C. sinicus adults and copepodites stage CV appeared to be well correlated with water temperature. They tended to concentrate in the YSCBW (>10,000 ind. m(-2)) to avoid high surface temperature. Gut pigment contents varied from 0.44 to 2.53 ng chlorophyll a equivalents (chl a equiv.) ind.(-1) for adults, and from 0.24 to 2.24 ng chl a equiv. ind.(-1) for CV copepodites. We found no relationship between gut pigment contents and the ambient chl a concentrations. Although the gut evacuation rate constants are consistent with those measured for other copepods, their low gut pigment contents meant an estimated daily herbivorous ingestion of <3% of body carbon in the YSCBW and <10% outside the YSCBW. However, based on estimates of clearance rates, C. sinicus feeds actively whether in the YSCBW or not, so the low ingestion rates probably reflect shortage of food. Oxygen consumption rates of C. sinicus ranged from 0.21 to 0.84 mul O-2 ind.(-1) h(-1), with high rates often associated with high temperature. From the oxygen consumption rates, daily loss of body carbon was estimated to be 4.0-13.7%, which exceeds our estimates of their carbon ingestion rates. C. sinicus was probably not in diapause, either within or outside the YSCBW, but this cold-water layer provides C. sinicus with a refuge to live through the hot, low-food summer.

Summer feeding activities of zooplankton in Prydz Bay, Antarctica

Grazing of dominant zooplankton copepods (Calanoides acutus. and Metridia gerlachei), salps (Salpa thompsoni) and microzooplankton was determined during the austral summer of 1998/1999 at the seasonal ice zone of the Prydz Bay region. The objective was to measure the ingestion rates of zooplankton at the seasonal ice zone, so as to evaluate the importance of different groups of zooplankton in their grazing impact on phytoplankton standing stock and primary production. Grazing by copepods was low, and accounted for less than or equal to 1% of phytoplankton standing stocks and 3.8-12.5% of primary production for both species during this study, even the ingestion rates of individuals were at a high level compared with previous reports. S. thompsoni exhibited a relatively high grazing impact on primary production (72%) in the north of our investigation area. The highest grazing impact on phytoplankton was exerted by microzooplankton during this investigation, and accounted for 10-65% of the standing stock of phytoplankton and 34-100% of potential daily primary production. We concluded that microzooplankton was the dominant phytoplankton consumer in this study area. Salps also played an important role in control of phytoplankton where swarming occurred. The grazing of copepods had a relatively small effect on phytoplankton biomass development.

Feeding activities of zooplankton in the Bohai Sea

The Bohai Sea was the site of the Chinese national GLOBEC programme. During the June 1997 cruises of R/V Science No.1, observations and experiments on zooplankton feeding were conducted. At five 48 h time-series stations the following observations and measurements on zooplankton were carried out: (1) diurnal vertical migration, by collecting samples at different layers every 3 h with a closing net; (2) diurnal feeding rhythms, by gut pigment analysis; and (3) ingestion rate, by both gut pigment analysis and the dilution method. A classification by body size was used to deal with the diversity of species and developmental stages of zooplankton assemblages. Samples were separated into three size groups: small (200-500 mu m), medium (500-1000 mu m) and large (> 1000 mu m). The results showed that the copepods (Calanus sinicus, Paracalanus parvus, Acartia bifilosa and Centropages mcmurrichi) performed clear diurnal vertical migrations. However, their behaviour was different at different stations. The variation in gut pigment content over the 24 h cycle showed strong diurnal feeding rhythms, particularly for the large size group. Gut pigment contents reached their daily maximum during the time from dusk to midnight (18:00-24:00). The peak value was about 10 times the minimum observed in the daytime. The in situ daily grazing rate, based on gut pigment contents and evacuation experiments, was 4.00-12.65 ng chla ind(-1) day(-1) for the small size group, 5.99-66.58 ng chla ind(-1) day(-1) for the medium size group and 31.31-237.13 ng chla ind(-1) day(-1) for the large size group. The copepods consumed only a small part (2.90-13.52%) of the phytoplankton biomass hut about 77% of the daily production. The grazing mortality rate of phytoplankton by microzooplankton (<200 mu m) measured by the dilution method ranged from 0.43 to 0.69 day(-1) The calculated daily consumption of phytoplankton biomass was 35-50%, and 85-319% of the potential production.

Effects of different diets on the reproduction and naupliar development of the copepod Acartia bifilosa

The influence of diatoms on the reproduction and naupliar development of Acartia bifilosa was investigated under laboratory conditions, comparing initial in situ values and laboratory-food treatments. Egg production by A. bifilosa was significantly reduced by one diatom diet (Phaeodactylum tricornutum: Pt) and by two non-diatom diets (Platymonas subordiformis: Ps and Nannochloropsis oculata: No). It was less affected by the other diatom diet (Skeletonema costatum: Sc) or by two mixed-food treatments (D-mix and DG-mix), composed of two diatoms (Pt, Sc) and four species (Pt, Sc, Ps and No), respectively. The negative effect of Pt was eliminated when adult copepods were offered mixed-food diets. There were no significant differences between the hatching success values observed in filtered seawater and in algal exudates, indicating that diatoms did not produce active dissolved toxic substances under the different food concentrations tested. The mortality rate of nauplii was higher with Pt than the other diets, suggesting that this diatom species had a negative effect on egg production, hatching success and naupliar survival simultaneously. Compared to other diets, No and Pt were not beneficial food sources for reproduction and for female and larval survival. (c) 2007 Elsevier B.V. All rights reserved.

Zooplankton functional groups on the continental shelf of the yellow sea

Zooplankton plays a vital role in marine ecosystems. Variations in the zooplankton species composition, biomass, and secondary production will change the structure and function of the ecosystem. How to describe this process and make it easier to be modeled in the Yellow Sea ecosystem is the main purpose of this paper. The zooplankton functional groups approach, which is considered a good method of linking the structure of food webs and the energy flow in the ecosystems, is used to describe the main contributors of secondary produciton of the Yellow Sea ecosystem. The zooplankton can be classified into six functional groups: giant crustaceans, large copepods, small copepods, chaetognaths, medusae, and salps. The giant crustaceans, large copepods, and small copepods groups, which are the main food resources for fish, are defined depending on the size spectrum. Medusae and chaetognaths are the two gelatinous carnivorous groups, which compete with fish for food. The salps group, acting as passive filter-feeders, competes with other species feeding on phytoplankton, but their energy could not be efficiently transferred to higher trophic levels. From the viewpoint of biomass, which is the basis of the food web, and feeding activities, the contributions of each functional group to the ecosystem were evaluated; the seasonal variations, geographical distribution patterns, and species composition of each functional group were analyzed. The average zooplankton biomass was 2.1 g dry wt m(-2) in spring, to which the giant crustaceans, large copepods, and small copepods contributed 19, 44, and 26%, respectively. High biomasses of the large copepods and small copepods were distributed at the coastal waters, while the giant crustaceans were mainly located at offshore area. In summer, the mean biomass was 3.1 g dry wt m(-2), which was mostly contributed by the giant crustaceans (73%), and high biomasses of the giant crustaceans, large copepods, and small copepods were all distributed in the central part of the Yellow Sea. During autumn, the mean biomass was 1.8 g dry wt m(-2), which was similarly constituted by the giant crustaceans, large copepods, and small copepods (36, 33, and 23%, respectively), and high biomasses of the giant crustaceans and large copepods occurred in the central part of the Yellow Sea, while the small copepods were mainly located at offshore stations. The giant crustaceans and large copepods dominated the zooplankton biomass (2.9 g dry wt m(-2)) in winter, contributing respectively 57 and 27%, and they, as well as the small copepods, were all mainly located in the central part of the Yellow Sea. The chaetognaths group was mainly located in the northern part of the Yellow Sea during all seasons, but contributed less to the biomass compared with the other groups. The medusae and salps groups were distributed unevenly, with sporadic dynamics, mainly along the coastline and at the northern part of the Yellow Sea. No more than 10 species belonging to the respective functional groups dominated the zooplankton biomass and controlled the dynamics of the zooplankton community. The clear picture of the seasonal and spatial variations of each zooplankton functional group makes the complicated Yellow Sea ecosystem easier to be understood and modeled. (C) 2010 Elsevier Ltd. All rights reserved.

Simultaneous enumeration of diatom, protozoa and meiobenthos from marine sediments using Ludox-QPS method

The Ludox-QPS method is a newly developed technique, which combines the Ludox HS 40 density centrifugation and quantitative protargol stain, to enumerate marine ciliates with good taxonomic resolution. We tested the method for simultaneous enumeration of diatoms, protozoa and meiobenthos and compared its extraction efficiency for meiobenthos with that of the routine Ludox-TM centrifugation and a modified protocol using Ludox HS 40. We conducted the evaluation with a sample size of 8.3 ml each from sandy, muddy-sand and muddy sediments collected from the intertidal area of the Yellow Sea in summer 2006 and spring 2007. The Ludox-QPS method not only produced high extraction efficiencies of 97 +/- 1.3% for diatoms and 97.6 +/- 0.8% for ciliates, indicating a reliable enumeration for eukaryotic microbenthos, but also produced excellent extraction efficiencies of on average 97.3% for total meiobenthos, 97.9% for nematodes and 97.8% for copepods from sands, muddy sands and mud. By contrast, the routine Ludox-TM centrifugation obtained only about 74% of total meiobenthos abundance with one extraction cycle, and the modified Ludox HS 40 centrifugation yielded on average 93% of total meiobenthos: 89.4 +/- 2.0% from sands, 93 +/- 4.1% from muddy sands and 97.1 +/- 3.0% from mud. Apart from the sediment type, sample volume was another important factor affecting the extraction efficiency for meiobenthos. The extraction rate was increased to about 96.4% when using the same modified Ludox centrifugation for a 4 ml sediment sample. Besides the excellent extraction efficiency, the Ludox-QPS method obtained higher abundances of meiobenthos, in particular nematodes, than the routine Ludox centrifugation, which frequently resulted in an uncertain loss of small meiobenthos during the sieving process. Statistical analyses demonstrated that there were no significant differences between the meiobenthos communities revealed by the Ludox-QPS method and the modified Ludox HS 40 centrifugation, showing the high efficiency of the Ludox-QPS method for simultaneous enumeration of diatom, protozoa and meiobenthos. Moreover, the comparatively high taxonomic resolution of the method, especially for diatoms and ciliates, makes it feasible to investigate microbial ecology at community level.