Zooplankton Communities In Lakes Research Articles

Discriminating zooplankton communities in lakes with brook trout (Salvelinus fontinalis) and in fishless lakes

Natural geographic barriers and escarpments inhibited the post-glacial colonization of many lakes by fish on the eastern Canadian Boreal Shield. Hence, fishless lakes containing freshwater communities that evolved without fish predation are commonly found on the Boreal Shield next to fish-present lakes. The aim of this study was thus to assess how different top-down control from fish or invertebrate predation structure zooplankton communities in eastern Canadian Boreal Shield lakes throughout the ice-free season. We examined zooplankton community characteristics using univariate indices such as abundance, richness (S), evenness (J'), diversity (H'), and multivariate species assemblages (Bray—Curtis dissimilarity) in 5 lakes with a single fish population, brook trout, Salvelinus fontinalis, and in 5 naturally fishless lakes throughout the ice-free season. The total abundance of zooplanktonic organisms was significantly higher in fishless lakes over the whole sampling period; this was related to the presence of small herbivorous species such as rotifers. Species assemblages of zooplankton were also significantly different between the 2 types of lakes throughout the season, principally due to the high abundance of rotifers and the scarcity of immature and mature daphnids in fishless lakes. Our results suggest that the low intensity of selective predation by brook trout on large herbivores and the heavy predation by Chaoborus americanus larvae on daphnids in fishless lakes appear to be the key factors for structuring the zooplankton community. Multivariate indicators identified patterns that were not revealed with the usual univariate indices, showing the importance of selecting appropriate indicators for the assessment of community structure.

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.

Seasonal dynamics of the crustacean zooplankton of a shallow eutrophic lake from the Mediterranean region

Little is known about the trophic interactions within shallow lakes from the Mediterranean region, although there is evidence of their distinctive features compared to northern temperate shallow lakes (particularly when considering their ichthyocenosis). To address this gap, we conducted a study on the seasonal dynamics of the zooplankton community in Lake Vela (Portugal), a turbid and eutrophic shallow lake, which exhibits marked dominance of alien fish species. Lake Vela was shown to be highly productive and turbid, except during a period of higher transparency, from January to April. The increase in transparency was attributable to a rise in water level, which reduced the amount of re-suspended particles. Transparency was additionally improved by a peak in Daphnia longispina densities (February and March), which transiently reduced chlorophyll concentrations to low levels (clear water phase). In the remainder of the year, the zooplanktonic assemblage was dominated by small-sized zooplankters (mainly Bosmina and cyclopoid copepods). Daphnia were virtually absent from August to December. Regression and multivariate analyses identified seston and fish predation as the main environmental gradients shaping the zooplanktonic assemblage. During the clear water phase, competition for resources also seemed to contribute to Daphnia dynamics. The observed pattern of seasonal dynamics of the zooplankton of Lake Vela was overall concordant with the PEG model, although the timing of certain events was different, most notably the peak of Daphnia dominance and the more prolonged influence of fish, relatively to northern temperate lakes. Our results suggest that both planktivory (by alien fish) and turbidity (seston) are issues that need to be addressed if adequate restoration programs are to be implemented.

Genetic composition of resident populations influences establishment success of immigrant species

We conducted an outdoor container experiment to test the hypothesis that the genetic composition of resident populations influences the establishment success of immigrant species. We manipulated the genetic compositions (source populations) of populations of the water flea Daphnia magna, a strong competitor in pond and shallow lake zooplankton communities, and monitored the establishment success of immigrant cladoceran species of a regional species pool. We show that establishment success is affected by the source population of the resident D. magna as well as by the presence/absence of macrophytes and the presence/absence of fish in the containers. Our results provide evidence that the genetic composition of resident populations can impact community assembly and metacommunity dynamics, and that community genetics can influence ecosystem functioning.

Effect of watershed land use and lake age on zooplankton species richness

Results of a field survey of southern Wisconsin shallow lakes suggested that watershed (catchment basin) land use has a significant and adverse effect on zooplankton species richness. Zooplankton communities in lakes with no riparian buffer zone, in agriculture-dominated watersheds, contained about half as many species as lakes in least-impact watersheds. In that study, the age of the lake was not taken into account. It is possible that agricultural lakes, often artificial, were so recently-constructed that they had not yet accumulated the equilibrium number of species characteristic of older lakes. In other words, it is possible that the interpretation of the results of the previous study is fatally flawed, if the results were an artifact of lake age, rather than an effect of land use. The major aim of this current study was to determine the ages of agricultural lakes and of lakes in least-impact watersheds, to test for an effect of lake age on zooplankton species richness, using the same sites from the previous study. We used an anova approach to test the null hypothesis that two factors, watershed land use and lake age, had no systematic effect on zooplankton species richness. We determined the age of 35 shallow lakes, using aerial photos, satellite images, and interviews of resource managers and land owners. We identified five artificial agricultural sites and five artificial sites in least-impact prairie watersheds. The artificial sites in this study ranged from 3 to 37 years in age, while natural lakes dated from the melting of the last glacier, about 9500 years ago. Our results suggest, that because artificial lake made up only about a third of the sites, and for the range of lake age and watershed land use, lake age did not have a significant effect on zooplankton species richness, while land use had a highly significant adverse effect. These results pose a larger question for future research. Namely, how quickly do newly-constructed lakes attain the equilibrium number of species seen in the previous study, and what is the quantitative relationship between lake age and zooplankton richness?

Effect of water pH and total dissolved solids on the species diversity of pelagic zooplankton in lakes: A statistical analysis

Statistical analysis of the combined influence of lake surface area (S), water pH, and total dissolved solids (TDS) on the formation of zooplankton communities in lakes has been made on the basis of available data on the number of species (N sp ) of pelagic zooplankton in 256 lakes of the temperate zone of Europe, Asia, and North America. Graphic analysis and analysis of variance have shown that extremely high or extremely low values of pH and TDS inhibit lake zooplankton. If the value of one of these factors is extremely high, any increase in the other factor is favorable for the inhibited zooplankton, and this second factor determines the value of N sp .

Comparisons of zooplankton community size structure in the Great Lakes

Zooplankton mean size and size spectra distribution potentially reflect the condition of trophic interactions and ecosystem health because they are affected by both resource availability and planktivore pressure. We assessed zooplankton mean size and size spectra using an optical plankton counter (OPC) on 35 site visits among lakes Superior, Michigan, Huron, Erie, and Ontario (2002–2003). The surveys were conducted in both nearshore regions (5–20 m depth) and on associated transects to offshore regions either greater than 8 km from shore or greater than 100 m depth. The survey sites were distributed across a gradient of land use disturbance in watersheds adjacent to the nearshore regions. The mean size, biomass density, statistical size distribution, and normalized biomass size spectra of zooplankton were determined from OPC measurements for all locations. Significant differences among lakes were observed in mean size, biomass, and the parameters of size spectra distributions for both nearshore and offshore regions. Significant differences within lakes were observed in some parameters that also allowed for significant discrimination between nearshore and offshore zooplankton communities in lakes Michigan (mean size, biomass, one spectral parameter), Ontario (mean size, three spectral parameters), and Superior (one spectral parameter). Similarly, some parameters allowed for discrimination between offshore epilimnion and hypolimnion waters in lakes Michigan (mean size, biomass, and four spectral parameters), Huron (biomass), and Ontario (two spectral parameters). The use of OPC technology and parameters that characterize spectral shape may have potential as an efficient and economic way for developing a size‐based zooplankton metric to discriminate among zooplankton communities in the Great Lakes.

Selective predators and their parasitized prey: Are epidemics in zooplankton under top-down control?

Seasonal change in the intensity of fish predation affects succession in lake zooplankton communities. Predation affects not only the zooplankton prey, but also their parasites. Because the ability of a parasite to spread depends in part on the death rate of the hosts, seasonal reductions in the intensity of predation on zooplankton could lead to parasite epidemics. We examined seasonal population dynamics, mortality rate, and incidence of parasitism in lake populations of Daphnia to determine whether parasitism displayed seasonality and synchrony among lake populations and whether any such patterns are consistent with seasonal changes in predation rates. Infections of a bacterial parasite (Spirobacillus cienkowskii )i nDaphnia dentifera populations were seasonal with epidemics in many lakes occurring synchronously in autumn. In situ foraging behavior of the dominant fish planktivores, bluegill sunfish, is highly selective on infected Daphnia. Mortality rates on the Daphnia drop just prior to the initiation of epidemics. An epidemiological model shows that this magnitude of decrease in mortality rate, if driven largely by a reduction in predation, can account for the seasonal occurrence of epidemics in our Daphnia populations. Together, these results suggest that parasitism in Daphnia populations may be seasonally restricted by fish predation.

Long-term changes of the crustacean zooplankton community in Lake Mjøsa, the largest lake in Norway

Lake Mjøsa has been subject to an accelerating eutrophication from the 1950s to the mid 1970s, but comprehensive nutrient reduction efforts caused marked reductions of phytoplankton production and biomass during the 1980s, a process that continued during the 1990s. Zooplankton biomass and species composition was considerably affected during the eutrophication and subsequent oligotrophication. Total crustacean zooplankton biomass decreased along with decreasing algal biomass during the 1980s and 1990s. The seasonal means of zooplankton biomass were positively correlated with seasonal means of phytoplankton biovolume and chlorophyll-a, indicating a primarily bottom up regulation of the zooplankton biomass. Several herbivorous and omnivorous zooplankton species (Daphnia galeata, Bosmina longispina, Limnocalanus macrurus and Cyclops lacustris) were probably negatively affected by reduced algal biomass, whereas other species (Holopedium gibberum and Thermocyclops oithonoides/Mesocyclops leuckarti) seemed to be positively affected. H. gibberum disappeared in the 1960s, but reappeared in the 1980s after the significant reduction in algal biomass and primary production. The temporal trend of T. oithonoides/M. leuckarti indicated a strong competition with cladocerans (mainly B. longispina and D. galeata) in periods with high algal biomass. Early warming of the lake could also have promoted a biomass increase of T. oithonoides/M. leuckarti in later years, although the mean epilimnion temperature did not correlate with seasonal mean biomass of these species. The seasonal mean biomass of Eudiaptomus gracilis, the dominant calanoid, showed substantial fluctuations with 6-7 years between tops, but a decreasing trend during the 1990s. However, there were no significant correlations between this species and any of the environmental variables. The study indicated that dominant cladocerans (D. galeata and B. longispina) are decisive for the success of cisco (Coregonus albula), one of the most important planktivorous fish species, as also described by earlier studies. However it also demonstrated top down control on cladocerans in years with especially large stocks of cisco.

Crustacean zooplankton communities in lakes recovering from acidification

Large reductions in sulphur emissions at the Sudbury, Ont., Canada, smelters in recent decades have resulted in decreased lake acidity, and biological improvements have followed. Lakes in the Sudbury area offer a very unique opportunity to develop our understanding of the processes regulating biological restructuring in aquatic ecosystems recovering from acidification. Here, we examine changes in crustacean zooplankton communities that have accompanied the chemical recovery of Whitepine and Sans Chambre lakes, near Sudbury, over the last two decades. In both these formerly acidic lakes, pH has increased to ~6.0, and some zooplankton community recovery has occurred. However, zooplankton communities have not completely recovered based on multivariate comparisons with the community composition of reference lakes. Although a number of acid-sensitive species have appeared, many did not persist, or did not achieve abundances typical of the reference lakes. This indicates that zooplankton community recovery will most likely depend on biotic and abiotic interactions within these lakes and not on factors affecting species dispersal. Both chemical and biological factors have large influences on biological recovery processes. Assessing biological recovery is very important since the restoration of healthy aquatic communities is a major objective of large-scale sulphur emission control programs.

Size-dependent foraging efficiency, cannibalism and zooplankton community structure.

To examine size-dependent food web interactions in systems with cannibalism, we compared the abundances of zooplankton and phytoplankton over 2 years in four lakes with cannibalistic perch (Perca fluviatilis) of which two also supported the top predator pike (Esox lucius). The abundance of perch 2 years and older was lower in lakes with pike than in lakes with only perch. In contrast, the abundance of small perch (young-of-the-year and 1-year old) was lower in lakes with only perch suggesting that intense cannibalism reduced these size classes to low levels in lakes lacking pike. Functional response experiments with differently sized perch and zooplankton showed that the attack rate of small perch susceptible to cannibalism was much higher than that of large cannibalising perch. The optimal body size of perch with respect to attack rate was also lower for small zooplankton prey than for large zooplankton. The zooplankton communities in lakes with only perch were dominated by the relatively small species Ceriodaphnia quadrangula and Bosmina spp. and total zooplankton biomass was higher in these lakes than in lakes with both pike and perch. In contrast, the mean size of cladoceran zooplankton was largest in lakes with both pike and perch owing to a dominance of the large zooplankton species Holopedium gibberum in these lakes. We relate these patterns to (1) the low foraging efficiency of large perch on small zooplankton and (2) the low abundance of small zooplanktivorous perch (due to cannibalism) in lakes with only perch. The differences in zooplankton community structure also resulted in different seasonal dynamics of phytoplankton between lakes. Cannibalism introduces a vertical heterogeneity to food webs that causes consumer-resource dynamics that are not predictable from linear food chain models.

Regional versus local processes in determining zooplankton community composition of Little Rock Lake, Wisconsin, USA

The species present within a community result from a combination of local and regional processes. We experimentally tested the importance of these two processes for lake zooplankton communities by examining the ability of additional species to persist when introduced into mesocosms in Little Rock Lake, Wisconsin, from other nearby lakes in the Northern Highland Lake District. We established a control treatment with only Little Rock Lake zooplankton and two treatments that supplemented the Little Rock communities with zooplankton from nearby lakes. Species richness declined during the 3 weeks of the experiment so that, at the end of the third week, the treatments with added zooplankton species had the same number of species as the controls; increasing the initial number of species in the community did not increase its final species richness. A plot of the mean species richness in the local habitat against the mean species richness of the regional pool fell below a 1:1 slope. This suggested that local processes were more important in structuring Little Rock Lake zooplankton communities.

Size structure of river zooplankton: seasonal variation, overall pattern and functional aspect

Density–size distributions of a river zooplankton community were examined about biweekly over a year in the upper tidal freshwater portion of a regulated Australian river, specifically the Hawkesbury–Nepean. Results were compared with those of similar studies in lakes (and reservoirs) to characterize the similarities and differences in the structure and grazing function of river and lake zooplankton communities. The density–size distributions of the river zooplankton community were similar to those of lake plankton communities, in terms of a marked temporal variation in shape and overall bimodal shape. They differed in terms of the truncation of the upper body size and the absence of a significant relationship between the slope (regression coefficient) of a log-linear density–size model and environmental variables. The river zooplankton community appeared to have a high average rate of biomass increase when measured against body-mass class and a low mass-specific grazing rate, compared with those of lake communities. Because of methodological differences between studies, inter-system comparisons of size spectra and grazing rates need cautious interpretations and generalizations.

Distribution and Species Composition of Zooplankton in Himalayan Ecosystems

AbstractThe zooplankton communities of lakes, Sars, wetlands and ponds in Jammu‐Kashmir Himalayas were examined. The waters are situated between 600–3800 m a. s. l. and, in the ordinates 30°–36° N. Significant variations in Rotifers and Crustacean distribution patterns were encountered. Some species having wide tolerance limits are more frequent while a few species due to their rigid environmental demands are restricted to few water bodies. Such species serve as good indicators of trophic evolution. The general distribution of these groups and their ecological implication have been discussed in the paper.

Prey selectivities of threespine sticklebacks (Gasterosteus aculeatus) and phantom midge larvae (Chaoborus spp.) in Newfoundland lakes

SUMMARY. 1. Threespine stickleback (Gasterosteus aculeatus) and Chaoborus (C. punctipennis and C. trivittatus) planktivore populations were sampled from several oligotrophic lakes on the Avalon Peninsula of Newfoundland, Canada. Pelagic zooplankton communities in these lakes consist of Daphnia catawba, Holopedium gibberum, Eubosmina longispina, Leptodiaptorma minutus, Epischura nordenskioldi, Cyclops scutifer and rotifers (Conochilus unicornis, Keratella and Kellicottia spp.).2. Comparison of gut contents of G. aculeatus and crop contents of later instar Chaoborus larvae with lake zooplankton communities indicated that the vertebrate and invertebrate plank tivores show contrasting species and size selectivities in their choice of zooplankton prey. Prey selectivities were quantified by means of the selectivity index α.3. G. aculeatus showed positive selectivity for larger zooplankton (greater than 0.76 mm in length), typically the cladoceran D. catawba, while Chaoborus larvae showed positive selectivity for smaller zooplankton (less than 0.50 mm in length), typically the cladoceran E. longispina. While rotifers never featured in the diet of the sticklebacks, these zooplankters were a common component of the chaoborid diet. H. gibberum, with its gelatinous sheath, was rarely found in the gut contents of G. aculeatus and was never found in the crop contents of Chaoborus larvae.4. Selective predation by these planklivores in the relatively shallow and well‐mixed oligotrophic Avalon lakes may influence species composition and size structure of the pelagic zooplankton communities.

Long-term dynamics of the zooplankton community in Lake Mjøsa, the largest lake in Norway

Long-term dynamics of the zooplankton community in Lake Mjøsa, the largest lake in Norway

Seasonal variations in the trophic structure of phyto-and zooplankton communities in lakes in different trophic states

A number of environmental factors are important in regulating the trophic structure of plankton. Increased nutrient supply results in an explosive development of small algae and herbivorous zooplankton. In the eutrophic lakes (Greifensee, Hallwilersee) several algal community collapses occur each year as a consequence of the grazing habit of the zooplankton, although only the grazing phase in May/June results in a ‘clear water period’. Vertical mixing influences the zooplankton community by reactivating the resting stages of predatory copepods. Predation phases can only be observed in lake Lucerne, where the hypolimnion ist deep and aerobic. Well balanced relationships between the different trophic levels are restricted to the phases with growth limiting conditions.

LONG TERM GRAZING CONTROL OF ALGAL ABUNDANCE: A CASE HISTORY

ABSTRACT Square Lake, Minn., mimics an ideal of the biomanipulation approach. The lake's zooplankton community is dominated by large (body size) herbivorous cladocerans (Daphnia pulicaria) whose collective grazing abilities have maintained a reduced standing crop of algae, apparently since 1926. The physical and chemical environmental factors that define Daphnia's niche in Square Lake are discussed and include stable stratification, a large hypolimnetic volume, and phosphorus concentrations within certain threshold limits. These environmental limitations seem to be generally important for providing a metalimnetic refuge for Dephnia . Future biotic reconstructions that aim to encourage large-bodied Daphnia should consider these environmental limitations.

Seasonal Patterns in the Zooplankton Community of a Eutrophic Lake in Eastern Washington Prior to Multiphased Restoration

ABSTRACT The zooplankton community of eutrophic Liberty Lake, Washington was investigated at two pelagic stations for a period of one year prior to the initiation of a multiphased lake restoration treatment. Analysis of the microinvertebrate population formed an integral part of an intensive limnological investigation of the physical, chemical, and biological characteristics of the lake prior to, during, and following a series of restoration treatments completed during 1980–81 (Funk et al. 1980). Seasonal variations in the composition, density, and biomass of the major groups and species of the zooplankton are discussed in relation to patterns observed in other localities. The rotifers numerically dominated the community throughout the study period with the species Keratella cochlearis, Kellicottia longispina and Polyarthra spp. making up the largest share of zooplankton density. Cladocerans, primarily Daphnia pulex and D. galeata mendotae, accounted for the largest portion of total biomass. Copepods assumed an intermediate position between the other two groups in terms of both density and biomass. Effects upon the lake zooplankton community following the alum application phase of the lake restoration project are also presented based on preliminary data obtained during and after the treatment.

The Zooplankton Community of Lacygne Lake: A Cooling Pond in Kansas

This study provides baseline data on the zooplankton community of LaCygne Lake before its use as a cooling pond and documents changes occurring after startup of the electrical power generation station. The spring zooplankton maximum shifted from July during the summer before plant operation to May and April in the two successive years after plant operation began. Zooplankton density increased significantly after the plant began operation. In situ thermal toler- ance experiments simulated passage through the condenser and discharge canal by exposing zoo- plankton 4 h to temperatures ranging from 35° to 40°C. Bosmina longirostris was the most heat resistant species. B. longirostris increased in density more than other zooplankton species after plant startup. Reservoirs are increasingly being used as cooling ponds to dissipate heat produced during the generation of electrical power. Use of a lake as a cooling pond can potentially affect the lake zooplankton community in many ways. The plant may cause zooplankton mortality when water from the cooling pond is pumped through the plant to remove heat from the steam condensers. Water emerging from the condenser is usually heated from 6 to 17°C above ambient lake temperatures (Clark, 1969) and may ultimately reach tempera- tures above zooplankton thermal tolerances, favoring population growth of heat resistant species. Another effect is that the discharge of the heated con- denser effluent back into the cooling pond may increase lake temperatures and alter zooplankton succession which is, in part, temperature dependent (Hall, 1964; Hutchinson, 1967). Most research related to the zooplankton of cooling ponds has focused on zooplankton thermal tolerance or mortality caused by condenser entrainment (Finesinger, 1926; Brown and Crozier, 1927; Brown, 1929; Heinle, 1969; Goss and Bunting, 1976; Carlson, 1974; Storr, 1974; Buikema et al., 1978). Few stu- dies have examined the combined impact of condenser passage and lake heat- ing on the zooplankton community of the cooling pond (Carlson, 1974; Krza- nowski, 1979). This study establishes baseline data on LaCygne Lake before it was used as a cooling pond and investigates initial changes in the zoo- plankton community of LaCygne Lake following electrical generation startup.