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Crustacean Zooplankton (crustacean + zooplankton)
Selected AbstractsLong-term responses of zooplankton to invasion by a planktivorous fish in a subarctic watercourseFRESHWATER BIOLOGY, Issue 1 2009PER-ARNE AMUNDSEN Summary 1.,Introduced or invading predators may have strong impacts on prey populations of the recipient community mediated by direct and indirect interactions. The long-term progression of predation effects, covering the invasion and establishment phase of alien predators, however, has rarely been documented. 2.,This paper documents the impact of an invasive, specialized planktivorous fish on its prey in a subarctic watercourse. Potential predation effects on the crustacean plankton, at the community, population and individual levels, were explored in a long-term study following the invasion by vendace (Coregonus albula). 3.,Over the 12-year period, the density and species richness of zooplankton decreased, smaller species became more abundant and Daphnia longispina, one of the largest cladocerans, was eliminated from the zooplankton community. 4.,Within the dominant cladocerans, including Daphnia spp., Bosmina longispina and Bosmina longirostris, the body size of ovigerous females and the size at first reproduction decreased after the arrival of the new predator. The clutch sizes of Daphnia spp. and B. longirostris also increased. 5.,Increased predation pressure following the vendace invasion induced many effects on the crustacean zooplankton, and we document comprehensive and strong direct and indirect long-term impacts of an introduced non-native predator on the native prey community. [source] Incorporating life histories and diet quality in stable isotope interpretations of crustacean zooplanktonFRESHWATER BIOLOGY, Issue 7 2008MARC VENTURA Summary 1. Stable isotope studies have been extremely useful for improving general food web descriptions due to their ability to simultaneously summarize complex trophic networks and track the energy flow through them. However, when considering trophic relationships involving only two or few species, application of general isotopic interpretations based on average fractionation values may easily lead to misleading conclusions. In these cases a more accurate consideration of the current processes involved in the isotopic fractionation should be considered. 2. We investigated the trophic relationships of the crustacean zooplankton assemblage in an alpine lake (Lake Redon, Pyrenees) by means of stable isotopes of carbon and nitrogen and applied information on their life history and biochemical composition in the interpretation. 3. The three species occurring in the lake had distinct isotopic signatures: the two copepod species (the cyclopoid Cyclops abyssorum and the calanoid Diaptomus cyaneus) had higher nitrogen isotopic composition than the cladoceran (Daphnia pulicaria), indicative of a higher trophic position of the two copepods. Most intra-specific isotopic variability was associated with growth, while the effect of metabolic turnover was negligible. The effects of changes in the proportion of lipids was restricted to the adults of the two copepods. 4. Daphnia Juveniles showed ontogenetic shifts in their carbon, and nitrogen isotopic composition. Cyclops copepodites only showed changes in carbon isotopic composition. These isotopic shifts with changes in size were the result of: (i) the prevalence of growth over metabolic turnover as the main factor for isotopic variability and (ii) feeding, during the growth period, on isotopically depleted food in the case of Daphnia, and on isotopically enriched food in the case of Cyclops. 5. The carbon isotopic variation in Cyclops juveniles could be explained by fitting an isotopic growth model that considered that they fed entirely on Daphnia. However this was not the case for nitrogen isotopic variability. Cyclops nitrogen isotopic composition variation and the Cyclops to Daphnia nitrogen isotopic enrichment were closely correlated to the quantity of Daphnia protein and to the dissimilarity in the essential amino acid composition between the two species, which can be interpreted as an indication of consumer nitrogen limitation. [source] Habitat selection and diel distribution of the crustacean zooplankton from a shallow Mediterranean lake during the turbid and clear water phasesFRESHWATER BIOLOGY, Issue 3 2007BRUNO B. CASTRO Summary 1. The fish fauna of many shallow Mediterranean Lakes is dominated by small-bodied exotic omnivores, with potential implications for fish,zooplankton interactions still largely unknown. Here we studied diel variation in the vertical and horizontal distribution of the crustacean plankton in Lake Vela, a shallow polymictic and eutrophic lake. Diel sampling was carried out on three consecutive days along a horizontal transect, including an open-water station and a macrophyte (Nymphaea alba) bed. Since transparency is a key determinant of the predation risk posed by fish, the zooplankton sampling campaigns were conducted in both the turbid (autumn) and clear water (spring) phases. 2. In the turbid phase, most taxa were homogeneously distributed along the vertical and horizontal axes in the three consecutive days. The only exception was for copepod nauplii, which showed vertical heterogeneity, possibly as a response to invertebrate predators. 3. In the clear water phase, most zooplankton taxa displayed habitat selection. Vertically, the general response consisted of a daily vertical migration (DVM), despite the limited depth (1.6 m). Horizontally, zooplankters showed an overall preference for the pelagic zone, independent of the time of the day. Such evidence is contrary to the postulated role of macrophytes as an anti-predator refuge for the zooplankton. 4. These vertical (DVM) and horizontal (macrophyte-avoidance) patterns were particularly conspicuous for large Daphnia, suggesting that predation risk from size-selective predators (fish) was the main factor behind the spatial heterogeneity of zooplankton in the spring. Thus, the difference in the zooplankton spatial distribution pattern and habitat selection among seasons (turbid and clear water phases) seems to be mediated the predation risk from fish, which is directly related to water transparency. 5. The zooplankton in Lake Vela have anti-predator behaviour that minimises predation from fish. We hypothesise that, due to the distinct fish community of shallow Mediterranean lakes, aquatic macrophytes may not provide adequate refuge to zooplankters, as seen in northern temperate lakes. [source] Effects of the non-indigenous cladoceran Cercopagis pengoi on the lower food web of Lake OntarioFRESHWATER BIOLOGY, Issue 12 2003Corey L. Laxson Summary 1. In North America, the invasive predatory cladoceran Cercopagis pengoi was first detected in Lake Ontario. We explored the impact of Cercopagis on the lower food web of Lake Ontario through assessments of historical and seasonal abundance of the crustacean zooplankton, by conducting feeding experiments on the dominant prey of the invader, and by estimating its food requirements. 2. Between 1999 and 2001, a decrease in the abundance of dominant members of the Lake Ontario zooplankton community (Daphnia retrocurva, Bosmina longirostris and Diacyclops thomasi) coincided with an increase in the abundance of Cercopagis. Daphnia retrocurva populations declined despite high fecundity in all 3 years, indicating that food limitation was not responsible. Chlorophyll a concentration generally increased, concomitant with a decline in the herbivorous cladoceran zooplankton in the lake. 3. Laboratory experiments demonstrated that Cercopagis fed on small-bodied species including D. retrocurva and B. longirostris. 4. Consumption demand of mid-summer populations of Cercopagis, estimated from a bioenergetic model of the confamilial Bythotrephes, was sufficient to reduce crustacean abundance, although the degree of expected suppression varied seasonally and interannually. 5. Predatory effects exerted by Cercopagis on the Lake Ontario zooplankton, while initially very pronounced, have decreased steadily as the species became established in the lake. [source] Studies on Temporal and Spatial Variations of Phytoplankton in Lake ChaohuJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 4 2007Dao-Gui Deng Abstract Temporal and spatial variations of the phytoplankton assemblage in Lake Chaohu, a large shallow eutrophic lake in China, were studied from September 2002 to August 2003. A total of 191 phytoplankton species was identified, among which Chlorophytes (101) ranked the first, followed by Cyanophytes (46) and Bacillariophytes (28). On average over the entire lake, the maximum total algal biomass appeared in June (19.70 mg/L) with a minimum (5.05 mg/ L) in November. In terms of annual mean biomass, cyanobacteria contributed 45.43% to total algal biomass, followed by Chlorophytes (27.14%), and Bacillariophytes (20.6%). When nitrate (NO3 -N) and ammonium (NH4 -N) concentrations dropped in spring, fixing-nitrogen cyanobacterium (Anabaena) developed quickly and ranked the first in terms of biomass in summer. It is likely that dominance of zooplanktivorous fish and small crustacean zooplankton favored the development of the inedible filamentous or colony forming cyanobacteria. The persistent dominance of cyanobacteria throughout all seasons may indicate a new tendency of the response of phytoplankton to eutrophication in Lake Chaohu. [source] | ||||||||||