浅析淡水浮游动物的种类组成及其生态功能作用

浮游动物是浮游生物中的一大生物类群,终生营浮游性生活.淡水浮游动物主要包括原生动物、轮虫、枝角类和桡足类四大类群.这四类浮游动物在水域生态学研究和经济水产中均占有重要地位.它们通过摄食控制浮游植物的数量,来调节水体生态平衡,因此可以通过浮游动物的群落结构变化进行水质监测;同时它们又是许多经济水产动物的饵料,因而其数量变化可以直接影响鱼类养殖.现在,对于浮游动物的研究已不止限于宏观,随着科研技术的进步、分子技术的发展,其研究方法已经实现了宏观与微观的结合,促进了浮游动物生态学研究的进步.     

海洋细菌生产力调控机制研究进展

综述了海洋细菌生产力的生态学意义,细菌生产力在海洋生态系统能量流动中具有重要作用;介绍了国内外的研究进展,我国细菌生产力的研究主要集中在东海、黄海海域,而面积最大的南海研究尚少。分析了海洋细菌生产力的调控机制,温度、DOM、无机营养盐﹑微型浮游动物摄食等都对其产生影响,海水中的DOM主要由可溶性糖类和可溶性氨基酸组成,不同种类的细菌对DOM的吸收并不一致,海水温度直接影响细菌的新陈代谢能力,对细菌生产力大小产生很大影响,浮游动物的摄食对细菌生物量产生抑制作用,但浮游动物在摄食中通过DOM的释放和对无机盐的再生,在海洋生态系统的物质循环也起到了重要作用,一定程度上提高细菌的生产活性。在不同海域不同的因子起到不同的调控作用。     

重金属对海洋桡足类的影响研究进展

桡足类是海洋浮游动物种群的主要组成部分和重要的初级消费者,重金属污染对其影响可通过食物链传递到其他海洋生物甚至人类。综述了近20 a来重金属对桡足类影响的研究进展,包括重金属对桡足类的毒性和生理效应,重金属在桡足类体内蓄积及桡足类体内重金属的食物链(网)传递。并指出今后的研究重点:桡足类体内致毒重金属的存在形式,重金属食物暴露对桡足类生理生化影响机理,以及重金属对桡足类生活史的影响。     

叉尾斗鱼仔鱼饵料选择与摄食强度

采用实验生态学方法,研究了叉尾斗鱼仔鱼对不同类别饵料的选择及其摄食强度。结果表明,2—3 日龄刚开口摄食的仔鱼对桡足类无节幼体有明显正选择,对轮虫表现为明显的负选择,而对枝角类和桡足类则完全不摄食。4—6 日龄仔鱼主要以桡足类无节幼体为食物,7—11 日龄的仔鱼主要以枝角类为食物,而12—25 日龄仔鱼则主要摄食桡足类。仔鱼口宽或全长与摄食饵料个体大小呈线性或曲线正相关。2 日龄仔鱼开口摄食发生率达47%,而3 日龄以上则保持100%;2 日龄仔鱼平均摄食量仅为0.0017 mg,而25 日龄仔鱼平均摄食量已达0.3795 mg。最高饱食率出现在25 日龄,达到60%,而消化道饱满系数以5日龄最大,达13.13%。但之后消化道饱满系数逐步下降,11—25 日龄仔鱼消化道饱满系数在1.46%—2.79%之间波动。     

长江口和杭州湾凤鲚胃含物与海洋浮游动物的种类组成比较

2009年6月—8月期间在长江口及杭州湾水域收集了1355尾的凤鲚（Coilia mystus）标本,对其胃含物进行分析,期间采用出现频率（F）、个数百分比（N）、重量百分比（W）、相对重要性指标（IRI）、优势度（Y）公式计算,并进行种类的相似性分析,同步采集了取样点附近的浮游动物,比较了凤鲚胃含物食谱与该海域浮游动物种类组成。结果表明：河口性的长额刺糠虾IRI 为703.25,%IRI为62.94%,远远超过其他种类,甚至超过任何一个桡足类优势种,因而是凤鲚食谱中的最重要的种类。凤鲚摄食的其他主要种类包括：火腿许水蚤（Schmackeria poplesia）（IRI = 261.04）,虫肢歪水蚤（Tortanus vermiculus）（IRI = 107.53）、真刺唇角水蚤（Labidocera euchaeta）（IRI = 27.27）。以上四种浮游动物重要性合计%IRI为98.36%。在主要食物种类占绝对优势。因而是凤鲚饵料中最重要的优势种。种类组成相似性分析结果显示：胃含物和海域浮游动物之间的相似度值大致在0.363—0.365之间;而两者桡足类之间的相似值在0.521—0.575之间。推测凤鲚对个体较小的桡足类摄食方法是过滤性摄食,对种类的选择性较低。而对个体较大的糠虾则是有选择性追逐摄食。     

浮游动物摄食在赤潮生消过程中的作用

浮游动物摄食在赤潮生消过程中起相当重要的作用。由于摄食过程的复杂性和生物物种与个体行为存在的多样性 ,使得赤潮过程中浮游动物的摄食研究具有相当难度。从浮游动物的摄食类型和习性、浮游动物摄食率测定、浮游动物选择性摄食对赤潮群落演替发展方向、浮游动物摄食在有毒微藻赤潮中的作用、浮游动物摄食在中国赤潮研究中的关键科学问题等几个方面探讨了浮游动物摄食对赤潮生物种群动力学的影响 ,为理解和治理赤潮提供科学依据     

厦门港表层水体磷周转的生物学过程Ⅱ：桡足类对浮游植物的摄食压力

为了解桡足类在磷的生物地球化学循环中的作用,于2005年5、8、11月和2006年3月分别在厦门时间序列站（XMTS）采用肠道色素法,研究了桡足类对浮游植物的现场摄食率,同步分析了桡足类的种类组成和数量变化,进而得到桡足类群体对浮游植物的摄食率.结果表明：厦门港桡足类对浮游植物的年平均摄食率为55.53 μg·m^-3·d^-1;其中秋季最高,为108.98 μg·m^-3·d^-1,夏季最低,为7.18 μg·m^-3·d^-1.根据试验数据估算,厦门港桡足类对浮游植物现存量的摄食压力四季平均为1.81%,春、夏、秋、冬分别为3.22%、0.06%、3.52%和0.46%.     

三峡水库坝前段蓄水前后桡足类种类组成的变化

三峡水库蓄水后库区水环境发生了巨大变化,坝前茅坪至归州的西陵峡段由激流型河流生态系统演变为相对静水的水库型生态系统。桡足类是河流、湖泊、水库中重要的浮游动物类群,在水生态系统中占有重要地位,在浮游动物的研究中备受重视[1—7]。20世纪50年代三峡水库论证时也曾对其淹没区小水体的桡足类进行过调查,并对建库后的桡足类的种类组成进行了预测,但当时在未成库区干流中没有采集到桡足类[8]。作者对三峡水库蓄水前后坝前段(茅坪至归州)的桡足类进行研究,以期为三峡水库水生态系统中桡足类的演替、水环境管理、第二和第三阶段蓄水后桡…     

食蚊鱼摄食特性及其与浮游动物和环境因子的关系

2008年11月—2009年4月,利用分时段采样法对广州暨南大学明湖内食蚊鱼在秋季(11月)、冬季(12—2月)、春季(3—4月)3个季节的摄食特性进行了研究,探讨其与湖内浮游动物群体数量动态、光照和水温的关系。结果表明:食蚊鱼主要以浮游动物为食,对枝角类和桡足类有较强的选择性;明湖日平均水温与浮游动物日平均丰度在3个季节间有显著差异,而食蚊鱼消化道饱满指数的差异不显著;食蚊鱼消化道饱满指数在这3个季节的变化与浮游动物丰度、水温、光照在这3个季节的变化无明显的相关;无论哪个季节,食蚊鱼在白天时段(10:00—18:00)的消化道饱满指数均高于夜间(22:00—6:00),表现出白天高峰型的摄食节律;光照是影响食蚊鱼昼夜摄食节律的主要因素,而水温、浮游动物丰度的昼夜变化与食蚊鱼的昼夜摄食节律没有显著相关。     

河口浮游动物生态学研究进展

综述了国内外有关河口浮游动物种类组成、时空分布、生物量及其环境影响因素等方面的若干研究进展。河口地区潮流、径流共存,是陆海相互作用的集中地带,环境因子复杂多变,生态环境敏感脆弱。因此,研究河口浮游动物群落结构的时空变化有助于更好地揭示近海生态系统的特征。河口水域重要的浮游动物有原生动物、轮虫、桡足类、糠虾、水母等。环境因素和人类的活动对浮游动物种类组成和时空分布具有重要影响,河口浮游动物群落结构变化主要受到食物、温度、盐度、动物摄食以及径流等因素的影响,盐度是决定浮游动物分布的关键性非生物因子。近年来的研究表明,微型浮游动物（原生动物,轮虫和无节幼体）在河口生态系统中占有重要地位,是微食物网和传统食物网连接的关键环节。浮游生物网是采集浮游动物样品的主要工具,对研究结果有重要影响,我国许多学者使用浅水Ⅰ型或Ⅱ型浮游生物网（网孔为507μm和169μm）采集样品,导致小型和微型浮游动物（如无节幼体）逃逸,研究结果被严重低估,而这些小型和微型浮游动物是幼鱼的重要开口饵料,因此合适的浮游生物网对于研究浮游动物极其重要。并对今后我国河口浮游动物生态学研究中值得关注的科学问题进行了探讨。     

Metabarcoding and metabolome analyses of copepod grazing reveal feeding preference and linkage to metabolite classes in dynamic microbial plankton communities

In order to characterize copepod feeding in relation to microbial plankton community dynamics, we combined metabarcoding and metabolome analyses during a 22‐day seawater mesocosm experiment. Nutrient amendment of mesocosms promoted the development of haptophyte (Phaeocystis pouchetii)‐ and diatom (Skeletonema marinoi)‐dominated plankton communities in mesocosms, in which Calanus sp. copepods were incubated for 24 h in flow‐through chambers to allow access to prey particles (<500 μm). Copepods and mesocosm water sampled six times spanning the experiment were analysed using metabarcoding, while intracellular metabolite profiles of mesocosm plankton communities were generated for all experimental days. Taxon‐specific metabarcoding ratios (ratio of consumed prey to available prey in the surrounding seawater) revealed diverse and dynamic copepod feeding selection, with positive selection on large diatoms, heterotrophic nanoflagellates and fungi, while smaller phytoplankton, including P. pouchetii, were passively consumed or even negatively selected according to our indicator. Our analysis of the relationship between Calanus grazing ratios and intracellular metabolite profiles indicates the importance of carbohydrates and lipids in plankton succession and copepod–prey interactions. This molecular characterization of Calanus sp. grazing therefore provides new evidence for selective feeding in mixed plankton assemblages and corroborates previous findings that copepod grazing may be coupled to the developmental and metabolic stage of the entire prey community rather than to individual prey abundances.     

Numerical study of the feeding current around a copepod

Three-dimensional, numerical simulations of the feeding current around a tethered copepod were performed using a finite-volume code. The copepod's body shape was modeled to resemble Euchaeta norvegica, and was represented by a curvilinear body-fitted coordinate system. In the simulations, the appendages that generate the feeding current were replaced by a distribution of forces acting on the water adjacent and ventrally to the body. First, the accuracy of the code was verified by simulating two viscous, zero-Reynolds-number flows for which analytical solutions are available. Then, simulations with realistic body shape and Reynolds numbers were carried out. The main features of the computed feeding current were compared with observations from Yen and Strickler (Invert. Biol., 115, 191-205, 1996), and good agreement was obtained. The entrainment region, as visualized by tracking particles in the feeding current and by plotting the resulting stream-tube, is quite large. The result can be used to quantify how the copepod takes advantage of the feeding current to trap the algal particles in its capture area. The configuration of the feeding current near to the body surface of the copepod is controlled by how the copepod forces the feeding current and by the copepod's morphology. These parameters were varied and their effects studied in a systematic manner. Specifically, by comparing various spatial distributions of the same amount of total force, it was shown that a distributed force dissipates less energy (and increases the entrainment rate) than a concentrated force, it is thus energetically more desirable. Variations of the copepod's body shape and of the distribution of forces showed little effect on the far field of the feeding current, and therefore do not appear to affect the detectability by other mechano-receptional organisms. The length scale of the influence field of the feeding current was shown to be anisotropic in three directions, extending 5-7 mm above or ventrally to the copepod, <1 mm dorsally to the copepod and >1 cm down from the abdomen. The results also suggest that the net reaction force on the copepod from the feeding current is of the same order of magnitude as the excess weight of the copepod, but is not sufficient to balance the excess weight completely.      

Planktonic marine copepods and harmful algae

Marine planktonic copepods are important grazers on harmful algae (HA) species of phytoplankton, and copepods are major entry points for vectorial intoxication of pelagic food webs with HA toxins. Previous reviews (Turner and Tester, 1997, Turner et al., 1998a, Turner, 2006) summarized information on HA interactions with zooplankton grazers, and vectorial intoxication of pelagic food webs, up through approximately 2005. Accordingly, this review will address primarily studies published during the last decade. It will concentrate on generic issues in the developing field of HA:grazer interactions, such as the extent to which HA toxins serve as copepod grazing deterrents, induction of HA grazing deterrents by exposure to copepods, copepod selective feeding to avoid ingesting HA taxa versus non-selective feeding on HA taxa, possible biogeographic aspects of the effects of HA toxins on copepods, impact of copepod grazing on HA bloom development and termination, the role of copepods as entry points for vectorial intoxication of pelagic food webs with HA toxins, and possible reasons and remedies for the highly-variable and conflicting results reported for many studies of copepod grazing on various HA species.     

Chemoreception and the deformationof the active space in freely swimming copepods: a numerical study

A three-dimensional alga-tracking, chemical advection–diffusionmodel was used to calculate the deformation of the active spacesurrounding an alga entrained within the flow field around afreely swimming copepod. From the model, the advance warningtime resulting from the copepod's chemo-reception of the entrainedalga was quantified, and copepod chemoreception capability comparedfor several different swimming behaviors: hovering in the water,swimming slowly (swimming upward, swimming backward and swimmingforward), swimming fast (swimming upward, swimming backwardand swimming forward) and sinking (with the anterior pointingupward or downward). The results show that when it hovers orswims slowly, a copepod can use chemoreception to remotely detectindividual algae entrained by the flow field around itself.In contrast, a fast-swimming copepod is not able to rely onchemoreception to remotely detect individual algae. The possibilityof a free-sinking copepod using chemoreception to detect algalparticles is also indicated. It is shown that advection by thefluid motion dominates over diffusion in transporting the chemicalsignals inside the active space to the location of a copepod'schemoreceptors. The feeding current structure for a hoveringcopepod is described. It is suggested that the feeding currentstructure and re-routing or re-orienting response by a copepodin response to its antennule or other cephalic appendage inputsallow the copepod to capture the food particles that would otherwisepass outside its capture area and increase the amount of foodcaptured.     

Alpine newts (Triturus alpestris) as top predators in a high-altitude karst lake: daily food consumption and impact on the copepod Arctodiaptomus alpinus

1. Population dynamics and feeding ecology of adult and larval alpine newts (Triturus alpestris, Laurenti) were investigated in a high-altitude karts lake to estimate their feeding pressure on the copepod Arctodiaptomus alpinuf (Imhof). Estimates of population size for reproducing adults ranged from 666 to 864 individuals in the lake during July and August. Total abundance of larvae before the onset of ice cover varied considerably between 4400 and 25400 individuals in different years. 2. Arctodiaptomus alpinus was an important prey item for adult and larval alpine newts. During the second half of their aquatic period, adult newts moved to deeper water where the copepod reached its highest densities near the sediment. Adults and larvae exhibited no periodic feeding pattern. The feeding rhythm was more synchronized among the larvae than among the adults. 3. Daily food consumption, estimated using the Elliott & Persson (1978) model, reached 4–21 mg dry biomass in adults. The daily ration of larvae was about 7% of body dry weight in the temperature range 6-11°C. Compared to published estimates of daily food consumption in salmonid fishes, the feeding pressure of newts appears low.     

Effect of food preservation on the grazing behavior and on the gut flora of the harpacticoid copepod Paramphiascella fulvofasciata

Harpacticoids owe their ‘reputation’ as primary consumers in aquatic food webs to their substantial grazing on diatoms, thus assuring an efficient energy flow to higher trophic levels. Due to the complex feeding behavior of harpacticoids, the nature and dynamics of diatom-harpacticoid trophic interactions remain poorly understood. In addition, there is a growing interest from aquaculture industry in mass-culturing harpacticoids with algal foods but the labor costs of maintaining algal stock cultures are high. This study focuses on the palatability of preserved diatoms for copepods and considers the possible role of bacterially mediated effects on diatom food uptake.The grazing of Paramphiascella fulvofasciata on a preserved freeze-dried diatom diet was tested and compared to the grazing on fresh cells. P. fulvofasciata assimilated the preserved diet, but assimilation of fresh cells was higher. When both cell types were mixed, no selective feeding was observed. Community fingerprinting of the bacteria associated with diatoms and fecal pellets suggests that the copepod gut flora was modified depending on the food source. Furthermore, the results suggest that the egestion of gut bacteria enriches the microenvironment and this can have an additional influence on the feeding behavior of the copepod.Experimental research using preserved foods must take into account that copepod grazing assimilations of fresh foods are likely to be significantly higher. Yet, the stated high assimilation of the mixed diet, encourages further exploration of the application of preserved ‘balanced’ foods for harpacticoid mass-culturing.     

Gut evacuation of walleye pollock larvae in response to feeding conditions

Gut residence times of first-feeding walleye pollock larvae were measured at 6°C in continuous and discontinuous feeding regimes. Larvae fed tagged copepod prey evacuated their guts more quickly in continuous feeding as compared to the discontinuous feeding treatment. The mean gut residence time was estimated to be 5.0 h for larvae feeding continuously. Gut evacuation by larvae fed tagged prey and then isolated without food (discontinuous treatment) was slower and more variable, with an estimated gut residence time exceeding 8.0 h. Field and laboratory observations suggest that the larval fish gut may be modeled as an intermittent plug-flow reactor (PFR) in response to diel feeding patterns. The cyclical nature of gut dynamics has implications for gut content analyses and the estimation of daily food rations.     

Spatial distribution and trophic ecology of dominant copepods associated with turbidity maximum along the salinity gradient in a highly embayed estuarine system in Ariake Sea, Japan

The present study aimed to investigate into the feeding ecology of the dominant copepods along a salinity gradient in Chikugo estuary. Copepod composition was studied from samples collected from stations positioned along the salinity gradient of the estuary. Copepod gut pigment concentrations were measured by fluorescence technique and hydrographical parameters such as temperature, salinity, transparency, suspended particulate matter (SPM); pigments such as chlorophyll-a (Chl-a), phaeopigment; and particulate nutrients such as particulate organic carbon (POC) and particulate organic nitrogen (PON) were measured. Two distinct zones in terms of nutrient and pigment concentrations as well as copepod distribution and feeding were identified along the estuary. We identified a zone of turbidity maximum (TM) in the low saline upper estuary which was characterized by having higher SPM, higher POC and PON but lower POC:PON ratios, higher pigment concentrations but lower Chl-a/SPM ratios and higher copepod dry biomass. Sinocalanus sinensis was the single dominant copepod in low saline upper estuary where significantly higher concentrations of nutrients and pigments were recorded and a multispecies copepod assemblage dominated by common coastal copepods such as Acartia omorii, Oithona davisae and Paracalanus parvus was observed in the lower estuary where nutrient and pigment concentrations were lower. Copepods in the estuary are predominantly herbivorous, feeding primarily on pigment bearing plants. However, completely contrasting trophic environments were found in the upper and the lower estuary. It was speculated from the Chl-a and phaeopigment values that copepods in the upper estuary receive energy from a detritus-based food web while in the lower estuary an algal-based food web supports copepod growth. Overall, the upper estuary was identified to provide a better trophic environment for copepod and is associated with higher SPM concentrations and elevated turbidity. The study demonstrates the role of estuarine turbidity maximum (ETM) in habitat trophic richness for copepod feeding. The study points out the role of detritus-based food web as energy source for the endemic copepod S. sinensis in the upper estuary, which supports as nursery for many fish species.     

Copepod feeding in the ocean: scaling patterns,composition of their diet and the bias of estimates due to microzooplankton grazing during incubations

Here, we report insights from the compilation and analysis of data on marine calanoid copepod feeding rates in the ocean. Our study shows that food availability and body weight are major factors shaping copepod feeding rates in the field, with a relatively minor role of temperature. Although the maximal feeding rates of copepods that are observed in the field agree with the well-known 3/4 of body size scaling rule for animals, copepod feeding in the oceans is typically limited and departs from this rule. Ciliates and dinoflagellates appear to be highly relevant in the composition of copepod diets, and this represents an indirect increase in the flux of primary production that is likely to reach the upper trophic levels; this contribution is higher in the less productive systems and may help to explain accounts of proportionally higher standing stocks of copepods supported per unit of primary producer biomass in oligotrophic environments. Contrary to common belief, diatoms emerge from our dataset as small contributors to the diet of copepods, except in some very productive ecosystems. We have also evaluated the bias in the estimation of copepod grazing rates due to within-bottle trophic cascade effects caused by the removal of microheterotrophs by copepods. This release of microzooplankton grazing pressure accounts for a relevant, but moderate, increase in copepod grazing estimates (ca. 20–30%); this bias has an effect on both the carbon flux budgets through copepods and on our view of their diet composition. However, caution is recommended against the indiscriminate use of corrections because they may turn out to be overestimates of the bias. We advise that both uncorrected and corrected grazing rates should be provided in future studies, as they probably correspond to the lower and upper boundaries of the true grazing rates.     

Copepod flow modes and modulation: a modelling study of the water currents produced by an unsteadily swimming copepod

Video observation has shown that feeding-current-producing calanoid copepods modulate their feeding currents by displaying a sequence of different swimming behaviours during a time period of up to tens of seconds. In order to understand the feeding-current modulation process, we numerically modelled the steady feeding currents for different modes of observed copepod motion behaviours (i.e. free sinking, partial sinking, hovering, vertical swimming upward and horizontal swimming backward or forward). Based on observational data, we also reproduced numerically a modulated feeding current associated with an unsteadily swimming copepod. We found that: (i) by changing its propulsive force, a copepod can switch between different swimming behaviours, leading to completely different flow-field patterns in self-generated surrounding flow; (ii) by exerting a time-varying propulsive force, a copepod can modulate temporally the basic flow modes to create an unsteady feeding current which manipulates precisely the trajectories of entrained food particles over a long time period; (iii) the modulation process may be energetically more efficient than exerting a constant propulsive force onto water to create a constant feeding current of a wider entrainment range. A probable reason is that the modulated unsteady flow entrains those water parcels containing food particles and leaves behind those without valuable food in them.