常德柳叶湖及其连通水体浮游甲壳动物群落结构与水环境特征

为研究连通水体中浮游甲壳动物的群落结构,于2018年6月至2019年3月,对常德市柳叶湖、穿紫河和沅江常德市区河段组成的连通水体浮游甲壳动物和理化环境进行每季度一次的采样调查.共发现浮游甲壳动物27种,其中桡足类10种,枝角类17种.连通水体浮游甲壳动物丰度变化范围为1-132 ind./L,沅江常德市区河段浮游甲壳动...     

深圳湾浮游动物的群落结构及季节变化

2008年2月、5月、8月和11月分别对深圳湾浮游动物进行了周年的季节调查,结果共检出浮游动物38种和浮游幼体13类,其中原生动物2种,腔肠动物4种,介形类1种,桡足类22种,软甲类3种,毛颚类3种,被囊类1种,多毛类2种,浮游幼体（包括仔鱼）13类。年均丰度和生物量分别为406.7 ind.m-3和764.0 mg.m-3,高峰均位于夏季,低谷分别位于冬、春季。种类数（包括浮游幼虫）秋季最多为43种,夏季次之为30种,冬季最少仅23种。主要优势种为太平洋纺锤水蚤Acartia pacifica、刺尾纺锤水蚤Acartia spinicauda、短角长腹剑水蚤Oithona brevicornis、双生水母Diphyes chamissonis、卡玛拉水母Malagazzia carolinae、蔓足类幼体和桡足幼体等。多样性指数和均匀度年均值分别为2.568和0.526。回归分析表明浮游动物丰度和生物量与各环境因子之间存在明显的相关性,但有季节变化。     

Vertical distribution of zooplankton glutamate dehydrogenase in relation to chlorophyll in the vicinity of the Nantucket Shoals

The vertical distributions of chlorophyll, and zooplankton glutamate dehydrogenase (GDH) and respiratory electron transport system (ETS) activities were measured at five stations in the vicinity of the Nantucket Shoals using a submersible pump-profiling system. Distinctly lower zooplankton GDH activities and chlorophyll concentrations were found at a station showing little vertical stratification as compared to the other stations where vertical stratification was more pronounced. Maximum GDH activity was observed at or immediately above the chlorophyll maximum at the stratified stations. Respiration to excretion (O:N) ratios determined from the enzyme data were lowest in or just above the chlorphyll maximum, suggesting proteolytic catabolism at those depths. Both features had previously been observed in the oligotrophic Gulf of Mexico. Ammonium excretion determined from GDH activity was estimated to provide 20 to 40% of the total algal nitrogen requirement.Bigelow Laboratory Contribution No. 82016     

Seasonal changes in the diet and feeding behaviour of a top predator indicate a flexible response to deteriorating oceanographic conditions

Shifts in the diet of top predators can be linked to changes in environmental conditions. In this study, we tested relationships between environmental variation and seasonal changes in diet of a top predator, the grey-headed albatross Thalassarche chrysostoma, breeding at Bird Island, South Georgia in an austral summer of 1999/2000. Oceanographic conditions in that year around South Georgia were abnormal (i.e. anomalously high sea surface temperature to a relative 19-year long-term mean). The diet of grey-headed albatrosses showed high seasonal variation, shifting from cephalopods (42.9 % by mass) in late February to Antarctic krill Euphausia superba (58.3 %) in late April, and grey-headed albatrosses breeding performance was low (16.8 %). This study shows these albatrosses did not manage to find sufficient alternative prey and highlight the risk to top predators if there is an increase in the frequency or severity of food shortages in Antarctic waters.     

Larval fishes in the zooplankton community of the North Pacific Central Gyre

Patterns of species structure are described for the larval fish assemblage in the North Pacific Central Gyre. About 30,000 larvae, primarily of mesopelagic fish species, were identified for 7 cruises. Samples were collected using Isaacs-Kidd plankton trawls on 6 cruises over a 4 1/2 year period; stratified samples were taken with an opening/closing bongo net on one late-summer cruise. Data on absolute and relative abundances, size ranges and summertime depth distributions of over 150 species of larvae are presented. The depth distribution and abundance of the ichthyoplankton are compared to those of the total zooplankton community. The larval assemblage is also examined with respect to the known adult mesopelagic fish assemblage. Seasonal changes in ichthyoplankton species structure occur but, within seasons, species structure is remarkably constant from year to year. Despite seasonal changes in species abundance and rank order of abundance, a constant cumulative frequency structure was found to exist in the ichthyoplankton, both between seasons and between years. The implications of this result are discussed in light of similar findings in a terrestrial community and with respect to possible mechanisms of regulation.     

Speciation of nitrogen in the coral reef sedimentary environment of Lakshadweep archipelago,Indian ocean

This paper focuses on the spatial distributional profiles of different species of the important micronutrient element, nitrogen (nitrite, nitrate and total nitrogen) in various coral-reef sedimentary environment of Lakshadweep Archipelago. The relative abundance of the three forms of nitrogen was in the order, total-N???nitrate-N???nitrite-N. Relatively very low levels of nitrite in the different microenvironments of the islands are an indication of a higher rate of nitrification, so as to produce thermodynamically most stable form of nitrogen, namely nitrate under the condition of well-oxygenated shallow coastal/lagoon waters. A lagoon-ward enrichment pattern of total nitrogen in the lagoon transects of Agathy, Minicoy, Kadamath and Kiltan Islands also reflected the fact that the rate and space available for nitrogen fixation in shallow zones of the lagoon are high. Further, the nitrogenous waste materials produced from the reefs and surrounding environments have limited exchange with the sea, and all these factors, together with the organic nitrogen retention capacity of sediment types, contribute to total nitrogen.     

Hyperiid amphipods from the zooplankton community of the North Pacific central gyre

The hyperiid amphipods have been examined from an extensive series of depthstratified bongo net tows taken at 28°N; 155°W in the North Pacific central gyre, an open-ocean ecosystem. Seventy-nine samples from 6 depth ranges produced 14, 581 individuals belonging to 13 families, 42 genera, and 83 species. Data on depth distributions, rank orders of abundance, sex ratios, and vertical migration are presented. Most of these species are shown to be reproductively active in the gyre, and there appears to be no seasonality to their reproductive behavior. No species endemic to the gyre are yet known.     

Short-term changes in feeding and digestion by the copepodCalanus pacificus

The planktonic marine copepodCalanus pacificus exhibits an enhanced feeding rate, or hunger response, when exposed to food following short periods of starvation. In a scries of laboratory experiments with copepods collected from the main basin of Puget Sound, Washington, during 1982 and 1984, we measured maximum ingestion rate, assimilation efficiency, and digestive enzyme activity to determine the time scales over which the feeding behavior ofC. pacificus responds to increases in food. These laboratory results were then compared to field studies of diel fluctuations in digestive enzymes and gut fluorescence ofC. pacificus in Dabod Bay, a fjord of Puget Sound, during September, 1980, and the closely relatedC. marshallae off the Washington coast, in August, 1981. Laboratory experiments demonstrated that the hunger response ofC. pacificus lasts approximately 6 h before ingestion rate returns to a steady state level of about one-half maximum. On the order of 12h of starvation were required to induce the maximum ingestion rate of the hunger response. Digestive enzyme activities did not change over these time scales. Assimilation efficiency peaked within a few hours of the onset of feeding, with low initial rates possibly related to the period of starvation prior to feeding. These results were consistent with diel patterns observed in the field. The hunger response ofC. pacificus appears to be controlled by processes within the gut, and our results are discussed in relation to recent studies of the digestive processes of calanoid copepods.Contribution No. 1772 from the School of Oceanography, University of Washington, Seattle, Washington 98195, USA     

Trophodynamic function of copepods,appendicularians and protozooplankton in the late summer zooplankton community in the Skagerrak

The study was carried out in the Skagerrak during late summer when population development in the pelagic cycle culminated in the yearly maximum in zooplankton biomass. The cyclonic circulation of surface water masses created the characteristic dome-shaped pycnocline across the Skagerrak. The large dinoflagellate Ceratium furca dominated the phytoplankton biomass. Ciliates and heterotrophic dinoflagellates were the major grazers and, potentially, consumed 43–166% of daily primary production. The grazing impact of copepods was estimated from specific egg production rates and grazing experiments. The degree of herbivory differed between species (14–85%), but coprophagy (e.g. feeding on fecal pellets) and ingestion of microzooplankton were also important. The appendicularian Oikopleura dioica was present in lower numbers than copepods, but cleared a large volume of water. The grazing impact of copepods and O. dioica was estimated to 57±24% and 12±12% of daily primary production, respectively. Sedimentation of organic material (30 m) varied between 169 and 708 mg C m^–2 day^–1, and the contribution from the mesozooplankton (copepod fecal pellets and mucus houses with attached phytodetritus of O. dioica) was 5–33% of this sedimentation. Recycling of fecal pellets and mucus houses in the euphotic zone was 59% and 36%, respectively. However, there was a high respiration of organic material by microorganisms in the mid-water column, and 34% of the sedimenting material actually reached the benthic community in the deep, central part of the Skagerrak.     

Spatial and temporal shifts in stable isotope values of the bottom-dwelling shrimp<Emphasis Type="Italic"> Nauticaris marionis</Emphasis> at the sub-Antarctic archipelago

Spatial and temporal dynamics of carbon and nitrogen stable isotope signatures of the bottom-dwelling caridean shrimp Nauticaris marionis were measured during April and May between 1984 and 2000 in the vicinity of Marion Island (the Prince Edward Islands, Southern Ocean). There was one trophic-level enrichment in bulk ¹⁵N and ¹³C signatures between small (<20 mm long) and large (>20 mm) specimens of N. marionis, suggesting distinct trophic differentiation among major shrimp size groups. Both ¹⁵N and ¹³C values of N. marionis increased with the depth, reflecting changes in their diet. There were no clear temporal trends in bulk ¹⁵N signatures of N. marionis. However, compound-specific ¹⁵N measurements of amino acids indicated that N. marionis from the inter-island realm occupied the trophic level of second order carnivores, while similarly sized shrimps in the near-shore realm were at the trophic level of first order carnivores. Compound-specific measurements also identified a change in the source of inorganic nitrogen at the base of the food web between the inter-island and near-shore realms. In contrast to the bulk ¹⁵N values, a significant shift in bulk ¹³C values of N. marionis was observed between 1984 and more recent years. This temporal change appears to be linked to changes in the overall productivity of the Prince Edward Island inter-island system, which could be linked to global climate change.Communicated by J.P. Thorpe, Port Erin     

Surface zooplankton dynamics and community structure in the Gulf of Aqaba (Eilat), Red Sea

Winter and summer zooplankton maxima were observed on both near-reef and offshore sampling sites in the northern part of the Gulf of Aqaba, with summer maxima smaller than those of winter and more characterized by larval forms. Near-reef zooplankton biomass was generally several times greater than that observed 2 km offshore. During 1987, a near-reef maximum of 155 ind. or 12.2 g wet biomass m^–3 was observed in March, while 103 ind. or 8.5 g wet biomass m^–3 was observed in July. In the same year, 2 km offshore a maximum of 53 ind. or 2.5 g wet biomass m^–3 was observed in February, while a maximum of 33 ind. or 0.5 g wet biomass m^–3 was noted in July. The following year, 1988, the near-reef zooplankton abundances were little changed, but offshore zooplankton abundances were much higher (317 m^–3). During 1987, the dominant winter (March) forms near the reef were gammarid amphipods, at maximum concentrations of 100 ind. m^–3, where the summer (July) maximum was composed primarily of mysids (34 m^–3), gammarid amphipods (30 m^–3), and fish eggs (24 m^–3). The offshore winter zooplankton fauna was characterized by copepods and appendicularians, each at a maximum concentrations of ca 13 ind. m^–3, while the summer maximum was dominated by brachyuran zoea (31 m^–3). Though the 1988, winter near-reef zooplankton community compositions were similar to those of 1987, the offshore zooplankton fauna was dominated by ostracods, which were relatively rare in previous years. Preliminary data suggests that holoplanktonic forms like chaetognaths, copepods and appendicularians, at an offshore site exhibit different patterns of vertical migration than those near the reef. This different behavior may result from different species compositions of these taxa or from high concentrations of pseudoplanktonic bentho-neritic peracarid crustaceans.Please address correspondence and reprint requests to T. Echelman, Marine Science Research Center, State University of New York, Stony Brook, New York 11794-5000, USA     

Intraspecific variation in a predator affects community structure and cascading trophic interactions

Intraspecific phenotypic variation in ecologically important traits is widespread and important for evolutionary processes, but its effects on community and ecosystem processes are poorly understood. We use life history differences among populations of alewives, Alosa pseudoharengus, to test the effects of intraspecific phenotypic variation in a predator on pelagic zooplankton community structure and the strength of cascading trophic interactions. We focus on the effects of differences in (1) the duration of residence in fresh water (either seasonal or year-round) and (2) differences in foraging morphology, both of which may strongly influence interactions between alewives and their prey. We measured zooplankton community structure, algal biomass, and spring total phosphorus in lakes that contained landlocked, anadromous, or no alewives. Both the duration of residence and the intraspecific variation in foraging morphology strongly influenced zooplankton community structure. Lakes with landlocked alewives had small-bodied zooplankton year-round, and lakes with no alewives had large-bodied zooplankton year-round. In contrast, zooplankton communities in lakes with anadromous alewives cycled between large-bodied zooplankton in the winter and spring and small-bodied zooplankton in the summer. In summer, differences in feeding morphology of alewives caused zooplankton biomass to be lower and body size to be smaller in lakes with anadromous alewives than in lakes with landlocked alewives. Furthermore, intraspecific variation altered the strength of the trophic cascade caused by alewives. Our results demonstrate that intraspecific phenotypic variation of predators can regulate community structure and ecosystem processes by modifying the form and strength of complex trophic interactions.     

Spatial and temporal variability of phytoplankton biomass,primary production and community structure in the Pontevedra Ria (NW Iberian Peninsula): oceanographic periods and possible response to environmental changes

The spatial distribution of phytoplankton assemblages, chlorophyll, primary production and physical and chemical parameters were studied in the Pontevedra Ria in Galicia (NW Iberian Peninsula) from October 1997 to October 1998. In addition to the usual oceanographic periods described for the Galician Coast, two other periods were observed: a Prebloom or winter bloom, occurring during calm, sunny days in winter and a Continental period, related to the allochthonous intrusion of low salinity water from the Miño River in late spring. The phytoplankton biomass and production in both periods reached values of up to 145 mgChl-a m^?2 and 3.6 gC m^?2 day^?1, respectively, which were similar to those found in summer upwelling blooms. Throughout the year, the phytoplankton biomass and primary production gradients along the ria’s axis were highly dependent on the balance between upwelling and runoff. When the latter prevailed, increased values were measured toward the inner ria, while the opposite pattern was observed during summer upwelling blooms. According to projections derived from climate models and the analysis of wind patterns, temperature and precipitation trends in the area, a drop in the productivity of the ria would be expected as a result of reduced upwelling intensity in summer and decreasing rainfall in spring. In any case the estuarine part of the ria would be the most seriously affected.     

Prediction of response of zooplankton biomass to climatic and oceanic changes

This paper examines the long-term variation in zooplankton biomass in response to climatic and oceanic changes, using a neural network as a nonlinear multivariate analysis method. Zooplankton data collected from 1951 to 1990 off the shore of northeastern Japan were analyzed. We considered patterns of the Kuroshio and the Oyashio, sea surface temperature, and meteorological parameters as environmental factors that affect zooplankton biomass. Back propagation neural networks were trained to generate mapping functions between environmental variables and zooplankton biomass. The performance of the network models was tested by varying the numbers of input and hidden units. Changes in zooplankton biomass could be predicted from environmental conditions. The neural network yielded predictions with smaller errors than those of predictions determined by linear multiple regression. The sensitivity analysis of networks was used to extract predictive knowledge. The air pressure, sea surface temperature, and some indices of atmospheric circulation were the primary factors for predictions. The patterns of the Kuroshio and the Oyashio demonstrated different effects among sea areas.     

Effects of zooplankton diel vertical migration on a phytoplankton community: A scenario analysis of the underlying mechanisms

A mechanistic model was applied to study the influence of diurnal vertical migration (DVM) of planktonic crustaceans on the succession and composition of the phytoplankton community. While zooplankton was restricted to only one functional group, the phytoplankton community was divided into two functional groups which are distinguished by their maximum growth rates and vulnerability to zooplankton grazing. DVM causes a pulsed grazing regime and may also entail a corresponding reduction of the cumulative daily rates of ingestion and losses of zooplankton. To study the relative importance of these two mechanisms of DVM to phytoplankton we performed a scenario analysis consisting of 5 different scenarios. The results show that DVM has a strong influence on the phytoplankton community. Well edible algae benefit during the first 3–4 weeks of summer stratification by reduced daily grazing. The typical shift from small, well edible algae to larger, poorly or non-edible phytoplankton is distinctly delayed. Under the assumption of unchanged daily grazing, however, a pulsed grazing regime has nearly no influence on the resulting phytoplankton composition. As similar effects are also found for completely non-edible phytoplankton, indirect effects via phosphorus availability must be assumed. Thus, the scenario analysis reveals that the observed effects of DVM on phytoplankton can be explained by a combination of two mechanisms: (1) reduction of the daily zooplankton grazing, and (2) changed assimilation and remineralisation of phosphorus. Surprisingly and in contradiction to earlier reports there is almost no DVM effect on phytoplankton due to the sole action of a pulsed grazing regime.     

Diel trophic interactions between vertically-migrating zooplankton and their fish predators in an eelgrass community

Diel changes in the composition of crustacean zooplankton and the diets of fish predators from an intertidal eelgrass flat were monitored concurrently. The zooplankton is characterized by two major components. The obligate zooplankters (holoplanktonic calanoid copepods and meroplanktonic decapod larvae) appear to exhibit vertical migration, being present in higher densities near the surface of the water column at night. The facultative zooplankton (amphipods and ostracods) are benthic during the day, but move up into the water column at night. Planktivorous midwaterdwelling fish consume calanoid copepods and decapod larvae during the day and cease feeding or switch their diet to amphipods at night. Benthic-dwelling fish consume some amphipods during both day and night. The factors important in prey selection by fish and the functional significance of vertical migration in both components of the zooplankton are discussed in the light of the changing patterns of fish predation.This paper is Publication No. 183 in the Ministry for Conservation of Victoria, Environmental Studies Series.     

Hyperbenthic crustacean fauna of the Gullmarfjord area (western Sweden): Species richness,seasonal variation and long-term changes

Distribution of 118 species of Amphipoda, Mysidacea and Decapoda, sampled in 1984 and 1985 with an epibenthic sledge along a transect from the Skagerrak to the inner Gullmarfjord (Sweden), is described. Amphipods were richest in species in the Skagerrak, while most mysid species were taken at the sill. Deca-impoverished and the Lilljeborgidae, earlier represented by three species, had disappeared since the 1930s. The changes are most likely caused by eutrophication of the fjord. and deep-basin samples; (III) sill samples; (IV) Skagerrak samples. Characteristic species of the groups were identified with a pseudoF-test. Detrended Correspondence Analysis indicated seasonal faunal changes at 42 and 72 m depths. At both depths a shift in numerical dominance from amphipods to mysids was found in winter. The most pronounced changes seemed to occur at 42 m. Changes in composition and abundance of species during a renewal of the bottom water indicated that mysids were influenced by presumed near-bottom currents, while amphipods and decapods were not. Comparison of the present amphipod fauna with the fauna in 1933–37 revealed significant differences. The fauna in the deep basin was impoverished and the Lilljeborgidae, earlier represented by three species, had disappeared since the 1930s. The changes are most likely caused by eutrophication of the fjord.     

Short-term and long-term facilitation of goose grazing by livestock in the Dutch Wadden Sea area

We studied the impact of livestock grazing on the distribution ofBranta bernicla bernicla (Dark-bellied Brent goose) in the Dutch Wadden Sea during spring. It was hypothesized that livestock facilitate short-term (within-season) grazing for geese as well as long-term (over years). Therefore we measured grazing pressure by geese in salt marsh and polder areas that were either grazed (spring-grazed) or ungrazed during spring (summer-grazed). Additionally, we carried out a preference experiment with captive geese to test the preference between spring-grazed and summer-grazed polder swards. We furthermore compared patterns of use by geese between long-term ungrazed and grazed salt marshes. In May, there is a difference in grazing pressure by geese between polder pastures that are grazed or ungrazed during spring. In this month, the ungrazed polder pastures are abandoned and the geese shift to either the grazed polder pastures or to the salt marsh. Vegetation in the polder that had been spring-grazed had a lower canopy height and a higher tiller density than summer-grazed vegetation. The captive geese in the preference experiment showed a clear preference for vegetation that had been spring-grazed by sheep over ungrazed vegetation. Goose grazing pressure was negatively correlated to canopy height, both on the polder and on the salt marsh. Within the plant communities dominated byFestuca rubra andPuccinellia maritima, marshes that were intensively grazed by livestock generally had higher grazing pressure by geese than long-term ungrazed or lightly grazed salt marshes.     

The community effects of phenotypic and genetic variation within a predator population

Natural populations are heterogeneous mixtures of individuals differing in physiology, morphology, and behavior. Despite the ubiquity of phenotypic variation within natural populations, its effects on the dynamics of ecological communities are not well understood. Here, we use a quantitative genetics framework to examine how phenotypic variation in a predator affects the outcome of apparent competition between its two prey species. Classical apparent competition theory predicts that prey have reciprocally negative effects on each other. The addition of phenotypic trait variation in predation can marginalize these negative effects, mediate coexistence, or generate positive indirect effects between the prey species. Long-term coexistence or facilitation, however, can be preceded by long transients of extinction risk whenever the heritability of phenotypic variation is low. Greater heritability can circumvent these ecological transients but also can generate oscillatory and chaotic dynamics. These dramatic changes in ecological outcomes, in the sign of indirect effects, and in stability suggest that studies which ignore intraspecific trait variation may reach fundamentally incorrect conclusions regarding ecological dynamics.