Influence of competing and predatory invertebrate taxa on larval populations of mosquitoes in temporary ponds of wetland areas in Germany

Abundances of mosquito larvae and associated invertebrate communities were assessed in 27 temporary ponds during the spring season in wetland areas of Germany. Four genera of mosquitoes were identified: Aedes, Anopheles, Culex, and Culiseta. We focused our analyses on Aedes spp. because this genus was the most abundant (92% of total abundance) and frequently encountered mosquito (present in 65% of investigated sites). The abundance of Aedes spp. was negatively associated with the abundance of competitors for food, and to a lesser extent with those of intraguild predators and strict predators. The influence of these natural antagonists on larvae of Aedes was stronger in ponds with higher levels of dissolved oxygen (53 ± 4%) than in ponds with lower levels (16 ± 1%). The overall abundance of antagonists explained 42% of the variation in abundance of Aedes spp. at sites with higher levels of dissolved oxygen. Of this explained variation, competitors accounted for 34.7%, whereas the abundance of intraguild predators and strict predators accounted for only 6.8 and 0.5%, respectively. Therefore, the promotion of competing species might be an appropriate ecological approach for the control of Aedes spp. in temporary ponds in these areas.     

Species diversity in native fish community in Japan: comparison between non-invaded and invaded ponds by exotic fish

The relationship between invasions by two exotic fishes (Micropterus salmoides and Lepomis macrochirus) and species diversity in native fish communities was studied in 14 Japanese farm ponds. We found that mean number of species in native fish communities was three times higher in the ponds without the exotic fish than in the ponds with them. Further, negative relationships were observed between abundance of the two exotic fish and the total abundance of native fish communities. Our results suggest that invasions by the two exotic fish caused serious depletion of native fish communities, although another process can also be considered , that is, that ponds with poor native fish communities were prone to colonization by these exotic fish.     

Changes in trophic state and aquatic communities in high Arctic ponds in response to increasing goose populations

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Aquatic insects associated with two morphologically different submerged macrophytes, <Emphasis Type="Italic">Lagarosiphon ilicifolius</Emphasis> and <Emphasis Type="Italic">Vallisneria aethiopica</Emphasis>, in small fishless ponds

The study assessed the composition and abundance of insect assemblages associated with two submerged macrophytes, Lagarosiphon ilicifolius and Vallisneria aethiopica, in fishless ponds. Six ponds were used, with each plant occurring singly in two ponds, whilst the remainder had both plants. The insects were sampled using a 500-μm mesh. The number of insect taxa, diversity and total abundance on Lagarosiphon were greater than on Vallisneria when the plants occurred in separate ponds. In ponds comprising both plants, the total insect abundance on Lagarosiphon was greater than on Vallisneria. In all ponds, anisopteran naiads were dominant. Hemicordulia, Diplacodes and Trithemis made up 36.2, 27.1 and 15.2%, respectively, of the total number of insects on Lagarosiphon in single plant ponds. Trithemis was the only odonate in ponds comprised exclusively of Vallisneria and made up 68.7% of insects. In ponds that were cultured with both plants, four anisopteran taxa, Hemicordulia, Diplacodes, Trithemis and Tramea, were collected. In single plant ponds, the body-size class distribution of naiads on Lagarosiphon was characterised by a broader range, with significantly greater numbers of smaller and larger size classes than on Vallisneria (Kolmogorov–Smirnov test, P < 0.05). The study shows that in fishless waters, epiphytic insect assemblages may differ between the two plant species, especially when they are widely separated in space, probably due to greater predator–prey interactions on Vallisneria than on Lagarosiphon. The two plants may also differentially affect water physicochemical conditions, which may possibly influence insect ovipositing behaviour, and so affect insect community assemblage.     

Plant communities as a tool in temporary ponds conservation in SW Portugal

Temporary ponds are seasonal wetlands annually subjected to extreme and unstable ecological conditions, neither truly aquatic nor truly terrestrial. This habitat and its flora have been poorly studied and documented because of the ephemeral character of the flora, the changeable annual weather that has a great effect on the small, herbaceous taxa and the declining abundance of temporary ponds. The objectives of this study are: (a) to define plant community diversity in terms of floristic composition of ephemeral wetlands in SW Portugal, (b) to identify temporary pond types according to their vegetation composition and (c) to identify those ponds that configure the European community priority habitat (3170* – Mediterranean temporary ponds). Vegetation sampling was conducted in 29 ponds, identifying 168 species grouped among 15 plant communities. Soil texture, pH, organic C and N content were measured, but only N and percent of clay appear to be related with the distribution of each community type. The results showed that ephemeral wetlands could be classified into four type: vernal pools, marshlands, deep ponds and disturbed wetlands. Vernal pools correspond to the Mediterranean temporary ponds (3170*), protected as priority habitat under the EU Habitats Directive. Submersed Isoetes species (Isoetes setaceum and Isoetes velatum) represents, together with Eryngium corniculatum, the indicator species for vernal pools. We identify also indicator plant communities of this priority habitat, namely I. setaceum and E. corniculatum–Baldellia ranunculoides plant communities. In this region, the conservation of temporary ponds has so far been compatible with traditional agricultural activities, but today these ponds are endangered by the intensification of agriculture and the loss of traditional land use practices and by the development of tourism. Guest editors: B. Oertli, R. Cereghino, A. Hull & R. Miracle Pond Conservation: From Science to Practice. 3rd Conference of the European Pond Conservation Network, Valencia, Spain, 14–16 May 2008     

Impact of three aquatic invasive species on native plants and macroinvertebrates in temperate ponds

Biological plant invasions pose a serious threat to native biodiversity and have received much attention, especially in terrestrial habitats. In freshwater ecosystems impacts of invasive plant species are less studied. We hypothesized an impact on organisms from the water column and from the sediment. We then assessed the impact of three aquatic invasive species on the plants and macroinvertebrates: Hydrocotyle ranunculoides, Ludwigia grandiflora and Myriophyllum aquaticum. Our research on 32 ponds in Belgium indicated that the reduction in the native plant species richness was a common pattern to invasion. However, the magnitude of impacts were species specific. A strong negative relationship to invasive species cover was found, with submerged vegetation the most vulnerable to the invasion. Invertebrate richness, diversity and abundance were measured in sediments of invaded and uninvaded ponds along a gradient of H. ranunculoides, L. grandiflora, and M. aquaticum species cover. We found a strong negative relationship between invasive species cover and invertebrate abundance, probably due to unsuitable conditions of the detritus for invertebrate colonization. Taxonomic compositions of aquatic invertebrate assemblages in invaded ponds differed from uninvaded ponds. Sensitive benthos, such as mayflies were completely absent in invaded ponds. The introduction of H. ranunculoides, L. grandiflora, and M. aquaticum in Belgian ponds has caused significant ecological alterations in the aquatic vegetation and the detritus community of ponds.     

Relationship between freshwater gastropods and plant communities reflecting various trophic levels

Plant communities were examined in ponds in Brittany (north-west France) and then classified into six types reflecting different trophic levels: oligotrophic, oligodystrophic, mesotrophic, meso-dystrophic, meso-eutrophic an eutrophic. In 45 of these ponds, aquatic snails were sampled in order to determine the relationship between the gastropod species richness and the water trophic levels as indicated by plant community types. The second aim of this study was to determine whether some gastropod species were characteristic of a particular trophic level. The number of plant communities in the ponds was also taken into consideration.A trophic gradient was found along the F1 axis on the principal plane of the correspondence analyses. The species richnesses low or zero and especially the lymneid, Lymnaea glabra were close to the oligo-dystrophic and oligotrophic communities. In contrast, the highest numbers of snail species (5 and above) were found in the most eutrophic ponds where Hippeutis complanatus, Planorbis planorbis, Lymnaea stagnalis and Planorbarius corneus were particularly common. The latter species inhabited the ponds including on average the greatest number of macrophyte communities but no significant differences were found between snail species. The ponds which contained the greatest numbers of plant communities included the richest gastropod communities (7 and more) but also the poorest ones (0 or 1 species). Relationships between freshwater snails, macrophytes and trophic levels are discussed.Laboratoire de Zoologie et d'Ecophysiologie     

The loss of submerged plants with eutrophication I. Experimental design, water chemistry, aquatic plant and phytoplankton biomass in experiments carried out in ponds in the Norfolk Broadland

SUMMARY. 1 During eutrophication of shallow lakes, communities of submerged plants are often replaced by dense phytoplankton populations, but the mechanism by which this occurs is obscure though often assumed to involve shading. 2. This paper introduces a series investigating this change and describes a system of experimental ponds which were variously fertilized with nitrogen and phosphorus, had fish added or removed, and had their submerged aquatic plants cleared or left intact. 3. Fertilization with phosphate and ammonium nitrate in quantities effectively greater than those in a series of lakes in the adjacent Norfolk Broads, which have lost their submerged plants, did not displace the plant populations. 4. Total phosphorus and soluble reactive phosphorus concentrations in the water did not increase much with increasing loading in the presence of submerged plants but did so if the plants were manually cleared. Ammonium and nitrate concentrations were kept low, despite large additions in both plant dominated and manually cleared ponds. 5. In the absence of fish there were modest increases in chlorophyll a concentrations with phosphorus loading in the presence or absence of submerged plants. The concentrations achieved, however, were much lower than anticipated probably because of grazing by large-bodied Cladocera. 6. Ponds dominated by plants continued to have low phytoplankton populations even when fish were stocked. Low fish survival in these ponds permitted grazing zooplankters to flourish. In ponds cleared of plants, however, there were significant relationships between cholorophyll a concentration with Daphnia biomass (inverse) and log stock of potentially zooplanktivorous fish (positive). There was a significant relationship between chlorophyll a and total phosphorus concentrations in the plant and cleared ponds in 1982 but only in the plant ponds in 1983. In all cases the phytoplankton communities were dominated by small, often flagellated, organisms.     

Influence of submerged vegetation and fish abundance on water clarity in peri-urban eutrophic ponds

Despite the presence of high nutrient concentrations, most ponds located around Brussels (Belgium) show a considerable variation in turbidity. The importance of submerged macrophytes in maintaining the clear-water state requires identification of the main factors determining macrophyte abundance and diversity in ponds and small lakes. In this study, the inter-relationships between submerged macrophyte cover, fish abundance and turbidity were investigated in 13 eutrophic peri-urban ponds. Along a turbidity gradient, vegetation switched from dominance by Stoneworts (Chara and Nitella spp.) in the clearest ponds, to dominance by Potamogeton pectinatus in ponds with a slightly lower water transparency. Despite the presence of both P. pectinatus and Stoneworts in each of the vegetated ponds, only one became dominant. Only a very low abundance (around 20%) of submerged vegetation was found in ponds of intermediate turbidity, while macrophytes were absent in turbid ponds. Multi- and univariate analysis showed a marked difference in chemical, physical and biological properties between ponds deliberately used for fish stocking and ponds that were not. Macrophyte cover was significantly negatively correlated with turbidity and plankti-benthivorous fish abundance. No such correlation was observed with piscivorous fish abundance, except for pike that were associated with a charophyte vegetation in the study ponds. The strong relationship found between fish abundance and turbidity, its negative effect on submerged vegetation cover, and the importance of submerged vegetation in controlling phytoplankton abundance, should be taken into account when selecting ponds for fish stocking. It also suggests that the study ponds have a good potential for ecological quality restoration by biomanipulation.     

Crustacean biodiversity as an important factor for mosquito larval control

Newly established ponds, which are highly dynamic systems with changing levels of biological interactions among species, are common larval mosquito habitats. We investigated the impact of crustacean abundance and taxa diversity on mosquito oviposition and larval development. The effects of the biological larvicide Bacillus thuringiensis israelensis (Bti) on mosquito larvae were monitored according to fluctuations in crustacean communities. Populations of the mosquito Culex pipiens colonized artificial ponds that contained crustacean communities at different time points of colonization by crustaceans: 1) ‘no colonization’ (no crustaceans), 2) ‘simultaneous colonization’ by crustaceans and mosquitoes, and 3) ‘head‐start colonization’ by crustaceans (preceding colonization by mosquitoes). All types of ponds were treated with three concentrations of Bti (10, 100, or 1,000 µg/liter). Colonization of all ponds by Cx. pipiens (in terms of oviposition, larval abundance, and larval development) decreased significantly with increasing diversity of crustacean taxa. The total abundance of crustaceans had a minor effect on colonization by Cx. pipiens. The presence of crustaceans increased the sensitivity of Cx. pipiens larvae to Bti treatment by a factor of 10 and delayed the time of recolonization. This effect of Bti was relevant in the short term. In the long term, the presence of Cx. pipiens was determined by crustacean biodiversity.     

Measures to develop a rich-fen wetland landscape with a full range of successional stages

Species-rich plant communities characteristic for succession from mesotrophic open water to fen are very rare in The Netherlands. These vegetation types used to occur in turf ponds in the low lying peatland area, created by peat dredging and filled with water due to seepage of mesotrophic, well-buffered groundwater. One of the goals of the National Nature Policy Plan is to create new opportunities for the initial terrestrialization communities through ecological engineering, e.g., restoration and creation of open water habitats. Restoration of the abiotic conditions in acidified floating fen communities is only possible by a combined measure of removal of the Sphagnum-layer and superficial drainage of surplus rain water. New turfponds have been excavated. This study showed that the abiotic conditions (i.e., water depth and water chemistry) are favorable for the development of aquatic communities characteristic of mesotrophic conditions. The aquatic plant species found in the new ponds also point in this direction, e.g., Chara major and Ch. delicatula are very abundant as are seven Potamogeton species. It is concluded that a constant discharge of groundwater and a good connectivity between the ponds and the existing remnants of plant communities desired in the area are essential for the conservation and development of these species-rich plant communities.     

Flower resource and land management drives hoverfly communities and bee abundance in seminatural and agricultural grasslands

Pollination is a key ecosystem service, and appropriate management, particularly in agricultural systems, is essential to maintain a diversity of pollinator guilds. However, management recommendations frequently focus on maintaining plant communities, with the assumption that associated invertebrate populations will be sustained. We tested whether plant community, flower resources, and soil moisture would influence hoverfly (Syrphidae) abundance and species richness in floristically‐rich seminatural and floristically impoverished agricultural grassland communities in Wales (U.K.) and compared these to two Hymenoptera genera, Bombus, and Lasioglossum. Interactions between environmental variables were tested using generalized linear modeling, and hoverfly community composition examined using canonical correspondence analysis. There was no difference in hoverfly abundance, species richness, or bee abundance, between grassland types. There was a positive association between hoverfly abundance, species richness, and flower abundance in unimproved grasslands. However, this was not evident in agriculturally improved grassland, possibly reflecting intrinsically low flower resource in these habitats, or the presence of plant species with low or relatively inaccessible nectar resources. There was no association between soil moisture content and hoverfly abundance or species richness. Hoverfly community composition was influenced by agricultural improvement and the amount of flower resource. Hoverfly species with semiaquatic larvae were associated with both seminatural and agricultural wet grasslands, possibly because of localized larval habitat. Despite the absence of differences in hoverfly abundance and species richness, distinct hoverfly communities are associated with marshy grasslands, agriculturally improved marshy grasslands, and unimproved dry grasslands, but not with improved dry grasslands. Grassland plant community cannot be used as a proxy for pollinator community. Management of grasslands should aim to maximize the pollinator feeding resource, as well as maintain plant communities. Retaining waterlogged ground may enhance the number of hoverflies with semiaquatic larvae.     

Fish growth enhances microbial sulfur cycling in aquaculture pond sediments

Microbial sulfate reduction and sulfur oxidation are vital processes to enhance organic matter degradation in sediments. However, the diversity and composition of sulfate-reducing bacteria (SRB) and sulfur-oxidizing bacteria (SOB) and their environmental driving factors are still poorly understood in aquaculture ponds, which received mounting of organic matter. In this study, bacterial communities, SRB and SOB from sediments of aquaculture ponds with different sizes of grass carp (Ctenopharyngodon idellus) were analysed using high-throughput sequencing and quantitative real-time PCR (qPCR). The results indicated that microbial communities in aquaculture pond sediments of large juvenile fish showed the highest richness and abundance of SRB and SOB, potentially further enhancing microbial sulfur cycling. Specifically, SRB were dominated by Desulfobulbus and Desulfovibrio, whereas SOB were dominated by Dechloromonas and Leptothrix. Although large juvenile fish ponds had relatively lower concentrations of sulfur compounds (i.e. total sulfur, acid-volatile sulfide and elemental sulfur) than those of larval fish ponds, more abundant SRB and SOB were found in the large juvenile fish ponds. Further redundancy analysis (RDA) and linear regression indicated that sulfur compounds and sediment suspension are the major environmental factors shaping the abundance and community structure of SRB and SOB in aquaculture pond sediments. Findings of this study expand our current understanding of microbial driving sulfur cycling in aquaculture ecosystems and also provide novel insights for ecological and green aquaculture managements.     

Newly created ponds complement natural waterbodies for restoration of macroinvertebrate assemblages

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Density‐ and trait‐mediated top–down effects modify bottom–up control of a highly endemic tropical aquatic food web

Benthic invertebrates mediate bottom–up and top–down influences in aquatic food webs, and changes in the abundance or traits of invertebrates can alter the strength of top–down effects. Studies assessing the role of invertebrate abundance and behavior as controls on food web structure are rare at the whole ecosystem scale. Here we use a comparative approach to investigate bottom–up and top–down influences on whole anchialine pond ecosystems in coastal Hawai‘i. In these ponds, a single species of endemic atyid shrimp (Halocaridina rubra) is believed to structure epilithon communities. Many Hawaiian anchialine ponds and their endemic fauna, however, have been greatly altered by bottom–up (increased nutrient enrichment) and top–down (introduced fish predators) disturbances from human development. We present the results of a survey of dissolved nutrient concentrations, epilithon biomass and composition, and H. rubra abundance and behavior in anchialine ponds with and without invasive predatory fish along a nutrient concentration gradient on the North Kona coast of Hawai‘i. We use linear models to assess 1) the effects of nutrient loading and fish introductions on pond food web structure and 2) the role of shrimp density and behavior in effecting that change. We find evidence for bottom–up food web control, in that nutrients were associated with increased epilithon biomass, autotrophy and nutrient content as well as increased abundance and size of H. rubra. We also find evidence for top–down control, as ponds with invasive predatory fish had higher epilithon biomass, productivity, and nutrient content. Top–down effects were transmitted by both altered H. rubra abundance, which changed the biomass of epilithon, and H. rubra behavior, which changed the composition of the epilithon. Our study extends experimental findings on bottom–up and top–down control to the whole ecosystem scale and finds evidence for qualitatively different effects of trait‐ and density‐mediated change in top–down influences.     

Responses of plant and bird communities to prescribed burning in tallgrass prairies

Historic losses and fragmentation of tallgrass prairie habitat to agriculture and urban development have led to declines in diversity and abundance of plants and birds associated with such habitat. Prescribed burning is a management strategy that has potential for restoring and rejuvenating prairies in fragmented landscapes, and through such restoration, might create habitat for birds dependent upon prairies. To provide improved data for management decision-making regarding the use of prescribed fire in tallgrass prairies, we compared responses of plant and bird communities on five burned and five unburned tallgrass prairie fragments at the DeSoto National Wildlife Refuge, Iowa, USA, from 1995 to 1997. Overall species richness and diversity were unaffected by burning, but individual species of plants and birds were affected by year-treatment interactions, including northern bobwhite (Colinus virginianus) and ring-necked pheasant (Phasianus colchicus), which showed time-delayed increases in density on burned sites. Analyses of species/area relationships indicated that, collectively, many small sites did make significant contributions to plant biodiversity at landscape levels, supporting the overall conservation value of prairie fragments. In contrast, most birds species were present on larger sites. Thus, higher biodiversity in bird communities which contain area-sensitive species might require larger sites able to support larger, more stable populations, greater habitat heterogeneity, and greater opportunity for niche separation.     

Relationships between phytoplankton periodicity and the concentrations of total and unionized ammonia in channel catfish ponds

Phytoplankton abundance fluctuated throughout a 9 month study period in two 1.62 ha channel catfish (Ictalurus punctatus) production ponds. Summer phytoplankton communities in both ponds were dominated by blue-green algae (Cyanophyta). During periods of rapidly decreasing phytoplankton abundance, total ammonia-nitrogen concentrations increased but a decrease in pH during these same periods moderated the concentrations of unionized ammonia-nitrogen. Although unionized ammonia-nitrogen concentrations did not reach levels considered acutely toxic to fish, extended periods of moderately high unionized ammonia-nitrogen concentrations (>O.15 mg/1) occurred in the late fall months and may have serious implications for fish health.     

Vegetative composition and community structure associated with beaver ponds in Canaan valley, West Virginia, USA

Beavers (Castor canadensis) can cause dramatic changes in vegetative composition and diversity. Although alterations by beaver have been studied extensively, little attention has been paid to the effects beaver impoundments have on rare plants. Effective conservation of riparian and wetland rare plant species must consider the responses of vegetation to changes in hydrology that can occur when beaver populations are present. The goal of this research was to establish the occurrence of locally rare plant species, examine community composition, and analyze vegetative community structure of vegetation associated with beaver ponds in Canaan Valley, West Virginia, USA. Species richness and diversity were similar between plots located inside beaver ponds and adjacent to beaver ponds (P > 0.05). Although no significant difference in rare plant species was detected among pond ages, the oldest ponds (>56 years) had twice as many rare species as the youngest ponds (≤6 years). The youngest ponds had higher overall mean species richness (S) than ponds 7–56 years old (P < 0.05), but S returned to similar levels in the oldest ponds. Of the 15 rare species observed, most were classified as obligate (9) or facultative wetland (4) species. The youngest ponds contained the fewest number of rare species. Multiple response permutation procedure (MRPP) analyses of community structure detected no relation between community composition and either pond age or size. However, both MRPP and non-metric multi-dimensional scaling showed proximity to pond was important in herbaceous community structure. Wetlands in beaver ponds also were shown to be distinct from adjacent wetland areas. Conservation of existing beaver populations is necessary so that the entire spectrum of pond ages is available for the maintenance of rare plant species and communities.     

Climate‐associated tundra thaw pond formation and range expansion of boreal zooplankton predators

Most of the freshwater component of the Earth's surface is composed of shallow tundra ponds. These high latitude ecosystems have been exposed to a variety of abiotic disturbances associated with recent environmental change. However, the biological significance of these changes remains poorly understood. Here, we characterize the abiotic disturbance to the shallow tundra ponds of northwest Alaska. We used historical aerial imagery to determine that up to 53% of the sampled ponds have formed during the recent warmer decades (since the 1970s). We discovered that two top predator species (phantom midges of the genus Chaoborus) of the freshwater zooplankton have recently undergone range expansion, forming widespread (a scale of hundreds of km) stable tundra populations. We assessed the population persistence of these boreal predators by longitudinal sampling over 14 yr. Recent thaw ponds had significantly dissimilar zooplankton communities to communities of ponds that formed before 1950. Both predator and herbivore species differed by age of pond. Younger pond ages and warmer surface temperatures were the significant predictors of the presence of temperate Chaoborus americanus in tundra ponds. Ponds containing tundra populations of C. americanus and C. cf. flavicans were associated with recent formation (83–90%). Recent ponds in river valleys appeared more important than recent ponds near roads as colonization corridors for C. americanus. Only 24% of the tundra keystone predator, Heterocope septentrionalis, populations were from recent ponds. Our results suggest that climate‐associated disturbance can lead to a widespread stable range expansion of boreal species despite the propinquity of older ponds with top‐down control exerted by an endemic keystone predator.     

Restoration of lost aquatic plant communities: New habitats forChara

In the Netherlands peat was excavated for fuel until 1950. This gave rise to waterbodies (called turf ponds) which were then colonized by aquatic plants. Succession resulted in different aquatic plant communities and more terrestrialized stages such as floating fens. Nature conservation authorities started to excavate new turf ponds in 1990(ca. 2 ha y^–1) with the aim to restore calcareous, mesotraphent ecosystems by totally setting back succession. A sequence of new species was revealed by mapping the aquatic vegetation from 1990 onwards.Chara spp. proved early colonizers, which was not expected because they have not been present in ditches and ponds in the area for the last 20 years. The denseChara vegetation prevents the resuspension of organic soil and contributes to keep the water column nutrient-poor and clear. ability of species such asStratiotes aloides to colonise the ponds from adjacent waterbodies is not possible because no open contact exists between a turf pond and a ditch. Management measures, such as re-introduction, have to be considered if the full-range of aquatic plant communities remains the goal.