Contributions of airborne dispersal and dormant propagule recruitment to the assembly of rotifer and crustacean zooplankton communities in temporary ponds

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A comparison between predation effects on zooplankton communities by Neomysis and Chaoborus

Community level effects of predation by two invertebrate predators, the opossum shrimp (Neomysis intermedia), and the larva of the phantom midge (Chaoborus flavicans) were studied and compared. N. intermedia appeared abundantly in the shallow eutrophic Lake Kasumigaura and had a significant impact on the zooplankton community. The predation pressure by Neomysis was highest on cladocerans, followed by rotifers, and finally copepods. At high densities (maximum nearly 20 000 individuals m^–2), Neomysis excluded almost all cladocerans, rotifers and copepods from the lake.Zooplankton communities were established in experimental ponds, into which C. flavicans was introduced. The predator's density was around 1 individual l^–1, and was probably controled by cannibalism. Although Chaoborus larvae feed on various zooplankton species, their predation impact on zooplankton populations was markedly selective. They eliminated medium- and small-sized cladocerans and calanoid copepods from the ponds, but rotifers increased.Although the feeding selectivities of Neomysis and Chaoborus individuals were similar, the predation effects on zooplankton communities by the two predators were different.     

Zooplankton Composition and Ecology in Western Boreal Shallow-water Wetlands

Zooplankton are a functionally important but poorly studied component of western boreal forest (WBF) wetland ecosystems. To characterize patterns in zooplankton abundance and composition an exploratory study of 24 shallow-water wetlands in northern Alberta, Canada was carried out over the summers of 2001 and 2002. Results suggest zooplankton communities in WBF wetlands tend to exist as: (1) small-cladoceran dominated communities, (2) larger sized cladoceran (e.g. Daphnia) dominated communities, or (3) communities composed primarily of rotifers and/or other crustacean zooplankton. The presence/absence of brook stickleback (Culea inconstans) was the factor most strongly linked to zooplankton structure with small cladocerans tending to dominate in wetlands with stickleback. In fishless wetlands, communities dominated by medium-large sized cladocerans tended to correspond with low-chlorophyll/high-submerged aquatic vegetation (SAV) conditions. Conversely, communities composed of rotifers and other crustaceans were associated with high-chlorophyll/low-SAV states. Macro-invertebrate predator abundance was not strongly linked to patterns in zooplankton composition suggesting macro-invertebrate predation is not a significant factor influencing zooplankton structure in fishless wetlands. Results suggest activities that spread stickleback (e.g. ditching) or inhibit development of macrophyte-dominated/clear-water conditions (e.g. nutrient loading) may seriously alter the zooplankton community structure, and thereby the functional ecology, of these valuable wetland ecosystems.     

Habitat predictors of genetic diversity for two sympatric wetland‐breeding amphibian species

Population genetic diversity is widely accepted as important to the conservation and management of wildlife. However, habitat features may differentially affect evolutionary processes that facilitate population genetic diversity among sympatric species. We measured genetic diversity for two pond‐breeding amphibian species (Dwarf salamanders, Eurycea quadridigitata; and Southern Leopard frogs, Lithobates sphenocephalus) to understand how habitat characteristics and spatial scale affect genetic diversity across a landscape. Samples were collected from wetlands on a longleaf pine reserve in Georgia. We genotyped microsatellite loci for both species to assess population structures and determine which habitat features were most closely associated with observed heterozygosity and rarefied allelic richness. Both species exhibited significant population genetic structure; however, structure in Southern Leopard frogs was driven primarily by one outlier site. Dwarf salamander allelic richness was greater at sites with less surrounding road area within 0.5 km and more wetland area within 1.0 and 2.5 km, and heterozygosity was greater at sites with more wetland area within 0.5 km. In contrast, neither measure of Southern Leopard frog genetic diversity was associated with any habitat features at any scale we evaluated. Genetic diversity in the Dwarf salamander was strongly associated with land cover variables up to 2.5 km away from breeding wetlands, and/or results suggest that minimizing roads in wetland buffers may be beneficial to the maintenance of population genetic diversity. This study suggests that patterns of genetic differentiation and genetic diversity have associations with different habitat features across different spatial scales for two syntopic pond‐breeding amphibian species.     

Recovery of zooplankton diversity in a restored Mediterranean temporary marsh in Doñana National Park (SW Spain)

Over 30 years after drainage for agriculture, a 2700 ha temporary marshland was recently restored in Doñana National Park. We describe the recovery of zooplankton communities (copepods, cladocerans and rotifers) in 47 new temporary ponds excavated as part of the restoration project during the first two hydroperiods (April 2006 and 2007), and compare them to those of eight reference sites in the surrounding marshland. Major changes in the species composition and abundance occurred in new ponds between years. While rotifers and cyclopoid copepods dominated in terms of number of individuals in 2006, calanoid copepods and cladocerans were the most abundant groups in 2007. Rotifer species richness was significantly lower in 2007, but there was an increase in Simpson and β-diversity in 2007 owing largely to a dramatic decline in the abundance of Hexarthra cf. fennica (rare in reference sites) from 93% of all rotifer individuals in new ponds in 2006 to only 32% in 2007. In contrast, species richness of copepods and cladocerans was significantly higher in new ponds in 2007, but there were no changes in Simpson diversity. β-Diversity of cladocerans was also significantly higher in 2007. In 2006, the species richness of cladocera and copepods was significantly lower in new ponds than in reference sites, but by 2007 there were no differences in richness or Simpson diversity. Overall, 7 copepod, 13 cladoceran and 26 rotifer taxa were recorded in new ponds, including 80% of taxa recorded in reference sites. These results indicate that zooplankton communities can be rapidly restored in Mediterranean temporary wetlands, at least when large source populations in the surrounding area reduce dispersal limitation. They also illustrate the importance of comparing different metrics of richness and diversity in studies of zooplankton restoration.     

Impact of common tern colonies upon the zooplankton in Rybinsk Reservoir shallow waters

The comparison of the zooplankton communities developing in the semiprotected shallow waters of Rybinsk Reservoir under the impact of common tern (Sterna hirundo Linnaeus) colonies with communities in sheltered overgrowing habitats situated apart from colonies, has reveled some peculiar features of the former: higher biomass, prevalence of cladocerans, lower share of rotifers, and decrease in species diversity.     

Influence of overwinteringDaphnia on spring zooplankton communities: An experimental study

To evaluate the influence of overwintering individuals of zooplankton on spring zooplankton communities, the dynamics of zooplankton communities with or without overwintering individuals were observed in experimental ponds from fall to spring. An insecticide, carbaryl, was used to regulate the overwintering individuals. In ponds which received insecticide applications in November or January, all cladoceran and rotiferan species were eliminated by the treatments and did not reappear until late March or early April, even when the chemical disappeared rapidly. The low water temperature may delayed the establishment of the populations from resting eggs. In these ponds, populations of various cladoceran and rotiferan species, which seemed to be originated from resting eggs, were built up in the spring. In control ponds,Daphnia ambigua orD. longispina overwintered as juveniles and adults and established a large spring population earlier than other cladocerans and rotifers overwintering as resting eggs. The latter zooplankters did not increase in the spring probably because their growth was suppressed by the precedingDaphnia species through competition. In nature, even if the number of overwintering individuals is small, they may have a potential to build up a large population earlier than the individuals hatching from resting eggs. As a result, the species which have overwintered as individuals seem to predominate in the spring and have a large influence on the spring zooplankton community.     

Strong spatial influence on colonization rates in a pioneer zooplankton metacommunity

The magnitude of community-wide dispersal is central to metacommunity models, yet dispersal is notoriously difficult to quantify in passive and cryptic dispersers such as many freshwater invertebrates. By overcoming the problem of quantifying dispersal rates, colonization rates into new habitats can provide a useful estimate of the magnitude of effective dispersal. Here we study the influence of spatial and local processes on colonization rates into new ponds that indicate differential dispersal limitation of major zooplankton taxa, with important implications for metacommunity dynamics. We identify regional and local factors that affect zooplankton colonization rates and spatial patterns in a large-scale experimental system. Our study differs from others in the unique setup of the experimental pond area by which we were able to test spatial and environmental variables at a large spatial scale. We quantified colonization rates separately for the Copepoda, Cladocera and Rotifera from samples collected over a period of 21 months in 48 newly constructed temporary ponds of 0.18–2.95 ha distributed in a restored wetland area of 2,700 ha in Doñana National Park, Southern Spain. Species richness upon initial sampling of new ponds was about one third of that in reference ponds, although the rate of detection of new species from thereon were not significantly different, probably owing to high turnover in the dynamic, temporary reference ponds. Environmental heterogeneity had no detectable effect on colonization rates in new ponds. In contrast, connectivity, space (based on latitude and longitude) and surface area were key determinants of colonization rates for copepods and cladocerans. This suggests dispersal limitation in cladocerans and copepods, but not in rotifers, possibly due to differences in propagule size and abundance.     

Zooplankton community structure driven by vertebrate and invertebrate predators

Summary A zooplankton community was established in outdoor experimental ponds, into which a vertebrate predator (topmouth gudgeon: Pseudorasbora parva) and/or an invertebrate predator (phantom midge larva: Chaoborus flavicans) were introduced and their predation effects on the zooplankton community structure were evaluated. In the ponds which had Chaoborus but not fish, small- and medium-sized cladocerans and calanoid copepods were eliminated while rotifers became abundant. A large-sized cladoceran Daphnia longispina, whose juveniles had high helmets and long tailspines as anti-predator devices, escaped from Chaoborus predation and increased. In the ponds which had fish but not Chaoborus, the large-sized Daphnia was selectively predated by the fish while small-and medium-sized cladocerans and calanoid copepods predominated. In the ponds containing both Chaoborus and fish, the fish reduced the late instar larvae (III and IV) of Chaoborus but increased the early instar larvae (I and II). Small- and large-sized cladocerans were scarcely found. The former might have been eliminated by predation of the early instar larvae of Chaoborus, while the latter was probably predated by fish. Consequently, the medium-sized cladocerans, which may have succeeded in escaping from both types of predator, appeared abundantly. The results suggest that various combinations of vertebrate and invertebrate predators are able to drive various kinds of zooplankton community structure.     

Diel microdistribution of physical and chemical parameters within the dense <Emphasis Type="Italic">Chara</Emphasis> bed and their impact on zooplankton

Research on the diurnal distribution of physical and chemical parameters within a single macrophyte bed was carried out on the shallow Wielkowiejskie Lake (Poland). A non-parametric statistical analysis was used to compare the water quality features in different parts of a Chara hispida habitat including the middle, both edge (vertical and horizontal) parts of a macrophyte plant, and the open water next to-and above the stonewort stand. The obtained results showed a differentiation in the physical-chemical parameters of the environmental conditions within the Chara hispida stand. The greatest variability was found for dissolved oxygen. Its lowest concentrations were noted in the central part of the macrophyte stand, irrespective of the sampling time. The zooplankton communities within the examined Chara bed were strongly influenced by the concentration of dissolved oxygen. It was also found that two main components of zooplankton communities (rotifers and cladocerans) had a similar trend in their spatial and diurnal distribution within the stonewort stand.     

Studies on functional response and prey selection using zooplankton in the anostracan Chirocephalus diaphanus Prevost, 1803

Freshwater cladocerans and rotifers were used as prey to study functional response and prey selection by adult females of Chirocephalus diaphanus under laboratory conditions. For functional response studies, we offered three rotifer species (Brachionus calyciflorus, B. patulus and Euchlanis dilatata) and three cladoceran species (Alona rectangula, Ceriodaphnia dubia and Moina macrocopa) at various densities ranging from 0.5 to 16 ind. ml^–1. We found increased zooplankton consumption with increasing prey density but beyond 4 ind ml^–1 cladocerans and 8 ind. ml^–1 rotifers, the number of animals eaten plateaued. In general, C. diaphanus consumed fewer large prey (cladocerans) and many more smaller zooplankton (rotifers). For prey selection experiments, we used B. calyciflrous, B. patulus, C. dubia and M. macrocopa, offered at the ratio of two rotifers: one cladoceran and at three prey densities (total zooplankton numbers: 3, 6 and 12 ind. ml^–1). Prey selectivity patterns followed the functional response trends. In general, regardless of prey types, with an increase in the available zooplankton, there was an increase in the number of prey consumed. At any given prey density, C. diaphanus consumed higher numbers of rotifers than cladocerans. Among the prey offered, B. patulus and M. macrocopa were positively selected. Results are discussed in light of possible control of zooplankton by anostracans in temporary ponds.     

Factors Influencing the Seasonal Phenology and Composition of Zooplankton Communities in Mountain Temporary Pools

In 2001 nine temporary pools of the northern Apennines (Italy) were visited on 13 occasions during the ice‐free season (May to October). The aims of this research were to define the relationships between hydroperiod and other environmental variables and the zooplankton. In total, 49 zooplankton taxa were identified: 36 rotifers, 5 cladocerans, 6 copepods and 2 anostracans. Our results indicate that hydroperiod is a major determinant affecting zooplankton species richness. The highest number of taxa was found in the pond having the longest duration. Distinctive species assemblages were observed in different habitat types: pools with the shortest hydroperiod were characterised by organisms with brief life cycles (e.g. rotifers) and/or typical of temporary habitat (e.g. anostracans). Of the physical and chemical characteristics, pH and chlorophyll‐a appeared to have the largest influence on zooplankton distribution in the studied pools. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Dispersal-limited zooplankton distribution and community composition in new ponds

Twelve new experimental ponds were constructed identically, filled simultaneously, had similar physical and chemical properties, and were maintained with minimal manipulation. Colonizing zooplankton communities were sampled bi-weekly for one year. Rotifers dominated zooplankton communities in densities, biomass, and species number (47 of 61 observed species were rotifers). Only 14 species were observed in all 12 ponds; 9 were rotifers. Twenty-nine species (26 rotifers) were recorded in <-6 ponds. Species with high vagility exhibited greater viability. Ponds differed in zooplankton community composition throughout the year, due to differences in both vagility and viability among colonizing species.     

Horned grebe habitat use of constructed wetlands in Alberta,Canada

Wetland degradation has resulted in declines in populations of aquatic birds throughout North America. Horned grebe (Podiceps auritus), a migratory diving bird experiencing population decline, may benefit from wetland construction. We examined horned grebe use of borrow pits (ponds created during highway construction) in Alberta, Canada. Our goals were to document patterns of occurrence and breeding success of grebes on borrow pits and to determine if occupied and unoccupied sites differed in local habitat or landscape characteristics. In May 2003 and 2007, 330 constructed ponds were surveyed for horned grebes. We chose 100 occupied and 100 unoccupied ponds for additional surveys in 2007 and 2008, and collected habitat and landscape data for these sites. We used generalized linear mixed model and generalized linear model regression, coupled with Akaike's Information Criterion, to determine which environmental variables were most effective in explaining occurrence of horned grebes. The best model included all measured local and landscape habitat features. Horned grebes occurred on 36% of ponds in May 2003 and 2007, and chicks were produced on 74.5–81.3% of occupied ponds in 2007 and 2008. Grebes occupied larger ponds with more emergent and riparian vegetation and avoided ponds that supported beavers, contained human structures, and were primarily surrounded by forest within 1 km. On ponds with grebe pairs, chicks were produced more often on sites surrounded by more riparian vegetation. We conclude that the construction of small wetlands offers a promising means of increasing breeding habitat for horned grebes and present specific recommendations for breeding pond construction. © 2012 The Wildlife Society.     

Competition between rotifers and cladocerans of different body sizes

Summary We conducted laboratory experiments to test the hypothesis that rotifers could coexist with small (<1.2 mm) but not large (>1.2 mm) cladocerans. Keratella cochlearis was excluded in <8 days by the large cladocerans Daphnia pulex and D. magna, probably through both interference and exploitative competition. On the other hand, K. cochlearis persisted for 8 weeks with two small cladocerans (Bosmina longirostris and Ceriodaphnia dubia) and excluded a third small cladoceran (D. ambigua). Similarly, Synchaeta oblonga coexisted with B. longirostris for >7 weeks, and K. testudo coexisted with D. ambigua for >4 weeks. Coexistence of small cladocerans and rotifers was always accompanied by suppression of one or both populations, probably primarily if not exclusively by exploitative competition for limiting food resources. These results indicate that the competitive dominance of cladocerans over rotifers decreases markedly with cladoceran body size and that factors other than body size may determine the competitive outcome between rotifers and small cladocerans. Our study provides a mechanistic explanation for a commonly observed pattern in natural zooplankton communities: planktonic rotifers often are abundant when only small cladocerans occur but typically are rare when large cladocerans are present.     

The influence of bird colonies on the zooplankton in the Rybinsk Reservoir overgrown shallows

This article describes the peculiarities of the structural organization of zooplankton influenced by the waste products of the black-headed gull (Larus ridibundus Linnaeus) nesting colony in the protected overgrown shallow in Rybinsk Reservoir. The bird colony facilitates a modification of the zooplankton structure that is similar to the modifications of communities at early stages of eutrophication: the number of invertebrate species increases thanks to rotifers and cladocerans and the number and biomass of community increases due to cladocerans and copepods.     

Biological Invasions Across Spatial Scales: Intercontinental, Regional, and Local Dispersal of Cladoceran Zooplankton

The frequency of dispersal of invertebrates among lakes depends upon perspective and spatial scale. Effective passive dispersal requires both the transport of propagules and the establishment of populations large enough to be detected. At a global scale, biogeographic patterns of cladoceran zooplankton species suggest that effective dispersal among continents was originally rare, but greatly increased in the past century with expanded commerce. Genetic analysis allows some reconstruction of past dispersal events. Allozyme and mitochondrial DNA comparisons among New World and Old-World populations of several exotic cladocerans have provided estimates for likely source populations of colonists, their dispersal corridors, and timing of earlier dispersal events. Detecting the Old-World tropical exotic Daphnia lumholtzi early in its invasion of North America has allowed detailed analysis of its spatial spread. Twelve years of collection records indicate a rapid invasion of reservoirs in the United States, by both regional spread and long-distance jumps to new regions. Combining landscape features with zooplankton surveys from south-central US reservoirs revealed higher colonization rates of D. lumholtzi at lower landscape positions, a result which can be explained by either greater propagule load or by higher susceptibility of these downstream reservoirs. Because invaded reservoirs provide a source of propagules for nearby floodplain ponds, the rarity of this species in ponds suggests limitation by local environments. Such analyses of invading species over multiple spatial scales allow a better understanding of ecological processes governing invasion dynamics.     

Zooplankton community structure and environmental conditions in a set of interconnected ponds

We studied the zooplankton community structure in a set of 33 interconnected shallow ponds that are restricted to a relatively small area (`De Maten', Genk, Belgium, 200 ha). As the ponds share the same water source, geology and history, and as the ponds are interconnected (reducing chance effects of dispersal with colonisation), differences in zooplankton community structure can be attributed to local biotic and abiotic interactions. We studied zooplankton community, biotic (phytoplankton, macrophyte cover, fish densities, macroinvertebrate densities), abiotic (turbidity, nutrient concentrations, pH, conductivity, iron concentration) and morphometric (depth, area, perimeter) characteristics of the different ponds. Our results indicate that the ponds differ substantially in their zooplankton community structure, and that these differences are strongly related to differences in trophic structure and biotic interactions, in concordance with the theory of alternative equilibria. Ponds in the clear-water state are characterised by large Daphnia species and species associated with the littoral zone, low chlorophyll-a concentrations, low fish densities and high macroinvertebrate densities. Ponds in the turbid-water state are characterised by high abundances of rotifers, cyclopoid copepods and the opposite environmental conditions. Some ponds show an intermediate pattern, with a dominance of small Daphnia species. Our results show that interconnected ponds may differ strongly in zooplankton community composition, and that these differences are related to differences in predation intensity (top-down) and habitat diversity (macrophyte cover).     

Developing landscape habitat models for rare amphibians with small geographic ranges: a case study of Siskiyou Mountains salamanders in the western USA

To advance the development of conservation planning for rare species with small geographic ranges, we determined habitat associations of Siskiyou Mountains salamanders (Plethodon stormi) and developed habitat suitability models at fine (10 ha), medium (40 ha), and broad (202 ha) spatial scales using available Geographic Information Systems data and logistic regression analysis with an information theoretic approach. Across spatial scales, there was very little support for models with structural habitat features, such as tree canopy cover and conifer diameter. Model-averaged 95% confidence intervals for regression coefficients and associated odds ratios indicated that the occurrence of Siskiyou Mountains salamanders was positively associated with rocky soils and Pacific madrone (Abutus menziesii) and negatively associated with elevation and white fir (Abies concolor); these associations were consistent across 3 spatial scales. The occurrence of this species also was positively associated with hardwood density at the medium spatial scale. Odds ratios projected that a 10% decrease in white fir abundance would increase the odds of salamander occurrence 3.02–4.47 times, depending on spatial scale. We selected the model with rocky soils, white fir, and Oregon white oak (Quercus garryana) as the best model across 3 spatial scales and created habitat suitability maps for Siskiyou Mountains salamanders by projecting habitat suitability scores across the landscape. Our habitat suitability models and maps are applicable to selection of priority conservation areas for Siskiyou Mountains salamanders, and our approach can be easily adapted to conservation of other rare species in any geographical location.     

The longitudinal distribution and community dynamics of zooplankton in a regulated large river: a case study of the Nakdong River (Korea)

The longitudinal distribution and seasonal dynamics of zooplankton were examined along a 200-km section of the middle to lower Nakdong River, Korea. Zooplankton was sampled twice a month from January 1995 to December 1997 at five sites in the main river channel. There was considerable longitudinal variation in total zooplankton abundance (ANOVA, p < 0.001). All major zooplankton groups (rotifers, cladocerans, copepodids and nauplii) increased significantly with distance downstream along the river. There also were statistically significant seasonal differences in zooplankton abundance at the sampling sites (ANOVA, p < 0.01). Zooplankton abundance was high in spring and fall and low in summer and winter. The seasonal pattern of rotifers was similar to that of total zooplankton. This reflected the fact that rotifers (Brachionus calyciflorus, B. rubens, Keratella cochlearis and Polyarthra spp.) strongly dominated the zooplankton community at all locations. Among the macrozooplankton, small-bodied cladocerans (e.g. Bosmina spp.) dominated; the abundance of large-bodied cladocerans (e.g. Daphnia) was negligible (0–5 ind. l^–1). Among the environmental variables considered, partial residence time seemed to play the most important role in determining characteristics of the river zooplankton community.