Farm ponds make a contribution to the biodiversity of aquatic insects in a French agricultural landscape

Manmade ecosystems provide a variety of resources that have strong economic values. We assessed the importance of 37 farm ponds for the biodiversity of Odonata in an agricultural landscape lacking natural wetlands in southwestern France. Farm ponds captured 40% of the regional species pool, including both common and rare species. The species assemblages were not correlated with pond use (e.g., cattle watering, duck farming, etc.) or to landscape variable. Species richness was correlated with pond area, suggesting that community diversity was primarily driven by autoecological processes. Farm ponds thus made a positive contribution to the maintenance of aquatic biodiversity. This added value for biodiversity should be considered when calculating the costs and benefits of constructing water bodies for human activities.     

Pollution status of a tropical forest river using aquatic insects as indicators

Aquatic insects inhabiting Okhuo River, in a tropical forest near Benin City, Southern Nigerian, were studied between January and December 2006 to determine the taxa composition, diversity, EPT index, relative proportions of the various groups and hence the pollution level of the waterbody. Three stations were selected and sampled monthly using the kick sampling technique. A total of 3235 individual aquatic insects belonging to 24 taxa distributed among 23 genera in six orders were collected. The insect orders occurred in the following order of dominance: Ephemeroptera > Odonata > Coleoptera > Diptera > Plecoptera > Tricoptera. Based on the diverse composition of the community dominated by organisms intolerant of organic enrichment, and the high diversity and EPT index, water quality in Okhuo River is not significantly degraded. Community composition varies seasonally, with a trend toward a declining proportion during the rainy season and increasing proportions during the dry season. Aquatic insect composition in Okhuo River compares favourably with those in similar, relatively undisturbed forest streams and rivers in Nigeria, but the diversity and proportional distribution of taxa vary considerably between streams.     

Ordination of deep river invertebrate communities in relation to environmental variables

A deep Main river was examined to determine the effects of selected environmental variables on benthic invertebrate community structure. Thirty-three sites were sampled by divers using artificial substrates. The Bray-Curtis ordination was used to establish community types based upon combinations of current velocity, siltation, and organic detritus. While some invertebrates were tightly clustered within particular communities, most taxa tended to concentrate in one community type but were not excluded from others. The results tended to support the individualistic hypothesis of species distribution.     

Spatial variation in composition and richness of fish communities in a southwestern Australian river system

Thirteen species of fish were recorded from the non-tidal reaches of the Murray River system, southwestern Australia. Of these, nine were indigenous species. Although this system occurs in a zone of moderate to high rainfall, the species richness of this system is comparable to that of much harsher environments, such as the Canadian boreal zone or the Nevada desert. Species richness tends to increase in a downstream direction, and most changes in species composition are due to addition, rather than replacement of species. Stream order was strongly and significantly positively correlated with species richness (P < 0.001), but was in effect functioning as a composite variable. Stepwise multiple regression analysis showed that stream width, pH range, distance from the main stream, distance from the estuary, barriers and stream gradient together explained more than 80% of the variation in species richness. The variables, barriers, distance from the main stream and distance from the estuary, support island biogeography type explanations for variations in species richness, while the variable, stream width complies with the river continuum concept. A predictive model for species richness of any given reach of a lower west coastal stream in Australia was tried using variables that can be gathered almost entirely from detailed topographic maps and aerial photographs.     

Allochthonous aquatic insects increase predation and decrease herbivory in river shore food webs

Rivers produce an abundance of aquatic insects that traverse land, where they can have bottom-up effects on predators, who, in turn, can have top-down effects on terrestrial herbivores. This effect can cascade down to plants. These trophic relationships were demonstrated in a field of stinging nettles, Urtica dioica , along a river in Germany. At the shore compared to similar microhabitats 30–60 m away the abundance and biomass of: midges were highest, spiders were also highest, while herbivorous leafhoppers were lowest. At the shore, nettle plants were less damaged by herbivores and thus had less regrowth. Spiders regularly captured both aquatic midges as well as terrestrial leafhoppers and they captured more individuals of both groups at the shore than further away. Midges supported high densities of shore spiders. This was inferred from correlation of distribution and diet in the absence of other environmental gradients. Removal of spiders from experimental plots caused leafhoppers to increase at the shore, causing more plant damage. These effects were not evident at spider-removal sites away from the shore. This demonstrated that spiders depressed leafhoppers and decreased herbivory on plants only at the shore. It is concluded that aquatic insects had a bottom-up effect on spiders and that this subsidy facilitated a top-down effect that cascaded from spiders to leafhoppers to plants. Similar effects would explain the distribution of arthropods along many rivers. Allochthony connects river food webs with shore food webs, making both components essential for each other.     

Evaluating the use of macroscale variables as proxies for local aquatic variables and to model stream fish distributions

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Factors influencing fish distribution and community structure in a small coastal river in southwestern Costa Rica

We evaluated the relative importance of habitat size and diversity and distance from the ocean in explaining longitudinal patterns of fish distribution and community structure (species richness, evenness, and diversity) in the lower 5 km of the Rio Claro. The Rio Claro is a small coastal river in Corcovado National Park, southwestern Costa Rica, with a depauperate freshwater fish fauna. We observed 22 species in pools, 19 of which occured during quantitative sampling. Most of these species probably spent part of their lives in the Pacific Ocean. We observed no species in riffles, although these habitats were common and several taxa (e.g., Gobiesocidae, Gobiidae) were adapted for life in fast turbulent water. Fish abundance, and species richness, evenness, and diversity were highest near the ocean, where high tides influenced river levels and salinity. Eight species were not observed further than 2900 m from the ocean, whereas 6 species were not encountered in samples nearest the ocean; the remaining 8 species were present throughout the study area. Distance from the ocean was a better predictor of fish abundance and community structure than were pool width, pool depth, pool surface area, pool volume, amount of cover present, substrate diversity, or depth diversity. Based in qualitative comparisons of our data with previously published data from 1980–1986, the fish assemblage of the Rio Claro is persistent in both species composition and relative abundance.     

Environmental DNA detects a rare large river crayfish but with little relation to local abundance

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The aquatic insects of a standard small plain river in NE France,with emphasis on remarkable species

A five-year macroinvertebrate study was conducted on a 55 km river (le Rupt-de-Mad, Lorraine region, north-eastern France), a standard for the region. A list of 300 species was drawn up, and remarkable species were listed for some better known orders: Ephemeroptera, Plecoptera, Trichoptera and Odonata. Some faunistic results are emphasised: about 42% of the identified species were more or less ubiquitous, 26% were meso- to polysaprobic species of potamon, present only in the main course of the river, while 31% were rather stenoecious species restricted to certain tributaries. Fifty-one remarkable species were listed, taking into account their regional status, according to IUCN categories: more than three quarters were hosted in the small tributaries, and 55% found exclusively in these latter (versus 23.5% only present in the main course of the river). Calcareous lotic tributaries were hosting particularly original communities with many remarkable species. Ephemeroptera, Plecoptera and Trichoptera were pertinent groups to assess the global faunistic interest of lotic habitats, but lentic habitats are probably better evaluated using other groups, e.g. Odonata and Coleoptera; the latter unfortunately poorly known from an ecological point of view.     

Feeding ecology of three predacious aquatic insects and two fish in a riffle of the Speed River,Ontario

The food habits of two fish (Etheostoma flabellare and Rhinichthys atratulus) and three predacious aquatic insects (Nigronia serricornis, Paragnetina media and Agnetina capitata) were examined for one year in a riffle of the Speed River, Ontario. Adult E. flabellare fed primarily on net-spinning caddisflies whereas juvenile E. flabellare relied heavily on chironomids. Rhinichthys atratulus had a more varied diet composed of chironomids, Antocha larvae (Tipulidae) and net-spinning caddisflies. Two of the aquatic insect predators consumed large numbers of net-spinning caddisflies; however, P. media contained large percentages of Hydropsyche and Cheumatopsyche whereas N. serricornis fed primarily on non-hydropsychid net-spinners. The diet of A. capitata was composed largely of chironomids and mayflies. Schoener's diet overlap index () suggested that large E. flabellare and P. media had similar diets; however, E. flabellare ingested much larger prey than P. media. Adult E. flabellare contained a significantly greater proportion of larger prey items in comparison with benthic samples whereas similar comparisons with other predators showed no selection for larger prey. These data demonstrate that E. flabellare was size selective given the range of prey sizes available whereas the other predators were not. Also, there was little dietary overlap among the fish and invertebrate predators suggesting a partitioning of resources.     

Diversity of aquatic macrophytes in relation to environmental factors in the Slatina river (Slovakia)

Distribution and plant mass of aquatic macrophytes, and their relation to environmental conditions was studied in the submontane-colline Slatina river in 2004. Diversity of macrophytes was low, only 8 vascular plants, 3 mosses and group Algae filamentosae were found. Myriophyllum spicatum is dominant species, Fontinalis antipyretica, Rhynchostegium riparioides and Algae filamentosae are frequent. Interactions between flow class, bed material, depth of water and the first three mentioned macrophytes, as well as Jungermannia leiantha were detected. Sparganium erectum prefers more antrophogenic conditions and Myriophyllum spicatum prefers the light. According to cluster analysis, three distinct and ecologically well separated parts of the river were identified. Based on Reference index, poor ecological status for the studied part of the Slatina river was estimated.     

Movement of immature aquatic insects in a lotic habitat

The movement of immature insects up down and across Salem Creek, Ontario, was measured with traps and nets at two week intervals from January to December 1977. Drift of most taxa was more strongly correlated with water velocity from August to December than it was over the whole year. That of Baetis, however, was not correlated with water velocity and it was significantly greater at the side of the stream than at the centre from May to July. Upstream movement, as measured in three different ways, was small compared with drift, being only 2.1, 7.3 and 15.2 percent respectively.Upstream and across stream movements were not consistently different from one another, changes in their intensity apparently merely representing changes in numbers and behaviour of the animals. It is concluded therefore that upstream movement is only random movement.Colonization of empty sediment in trays on and above the substratum confirmed that most reoccupation of denuded areas is by drift. This supports the finding that drift is far geater than random wandering of the insects.     

Using social and physical variables to assess vulnerability of northwestern Montana lakes to illegal fish introductions

Hydrobiologia - The spread of non-native fish species is a common problem in lakes and streams worldwide. Species that establish viable populations in a new environment can seriously deplete...     

Macroalgae of a stream in southeastern Brazil: composition,seasonal variation and relation to physical and chemical variables

Macroalgal seasonality was studied monthly in a second-order stream in the north-west of São Paulo State, S.E. Brazil. Seasonal variation was based on frequency and percentage cover. Seven species were found during the study period, three of which (Chantransia stage of Sirodotia delicatula, Homoeothrix juliana and Klebsormidium subtile) were encountered throughout the year and showed well-defined seasonal patterns as well as the highest value of frequency and percentage cover. Chantransia and H. juliana dominated in summer and fall, while for K. subtile winter was the most favourable period. The remaining species (Oscillatoria agardhii, Microcoleus subtorulosus, Oedogonium sp. and Chaetophora elegans) had no clear seasonal pattern, in addition to their low values of frequency and percentage cover. Individually, K. subtile correlated with higher number of physical and chemical variables (oxygen, pH, precipitation, temperature, daylength, conductance and turbidity) than Chantransia and H. juliana (discharge and depth). Principal component analyses revealed that no single variable was responsible for the macroalgal seasonal dynamics. The variables most closely related to seasonal variation of the macroalgal community were daylength, precipitation, discharge, turbidity and dissolved oxygen. Precipitation and flow were suggested as key factors in determining seasonality of the macroalgae.     

Changes of river morphology and physical fish habitat following weir removal

Gongneung Weir-2 was built in the 1970s to supply water for irrigation. For a long time, the weir was left untended due to the land-use changes that were made to a nearby area. This weir was removed completely on April 4, 2006. The present study investigated the effect of the resultant flow-regime changes on river morphology and fish habitat. Observed changes in the grain size distribution, bed elevation, and cross-section pre- and post-weir removal are provided and discussed in this paper. Various bed zones such as a sand island and a vegetated marshy zone, which can diversify an aquatic habitat, formed after the removal. In fact, changes in the number of observed fish species post-removal also were investigated. Finally, specific changes to the physical habitat of Zacco platypus were numerically simulated using the River2D model. The results indicated that habitat suitability post-removal was enhanced for all flow discharges. The WUA values increased 32.3-53.4% for all life stages in the flow discharge of 1.5 m³ s⁻¹. The numerical results also showed that after the removal of the weir, the distribution of the physical habitat changed to reflect continuity near the weir.     

Long-term changes in fish community structure in relation to the establishment of Asian carps in a large floodplain river

The Upper Mississippi River System, including the Illinois River, has been invaded by a number of nonnative species including silver carp Hypophthalmichthys molitirx and bighead carp H. nobilis, collectively referred to here as Asian carps. Silver carp densities in the Illinois River have increased dramatically and now represent some of the highest densities of wild silver carp anywhere in the world. Asian carps have the potential to alter existing ecosystems by consuming planktonic resources and therefore, could have the ability to alter existing fish communities as most fishes are dependent on planktonic resources during early development. However, identifying the relationship of fish community structure to the establishment of Asian carps has yet to be thoroughly investigated. Using long-term fish community data collected by the Upper Mississippi River Restoration’s Long Term Resource Monitoring element, we investigate changes in fish community structure pre- and post-establishment of Asian carps. Significant differences in the pre- and post-establishment communities were observed for the majority of gears and habitats. Species contributing to changes between establishment periods included most sportfish species and catostomids, which were less abundant post-establishment of Asian carps, while shortnose gar, grass carp, and emerald shiner were more abundant. While our analyses show Asian carps are likely contributing to major differences in fish community structure, future research and long-term monitoring should investigate the mechanisms and interactions responsible for community changes as well as identifying any potential concurrent or confounding factors such as changes in river hydrology or sedimentation.     

Patterns of composition and species richness of crustaceans and aquatic insects along environmental gradients in Mediterranean water bodies

Differences in the dynamics of ecological processes between Mediterranean and colder temperate aquatic systems could imply different patterns in faunal communities in terms of composition and biodiversity (i.e. species richness and rarity). In order to identify some of these patterns the crustacean and aquatic insect composition and biodiversity of four water body types, classified according to their salinity and water permanence, were compared. Moreover, the relationships between species richness and water, pond and landscape variables were analysed. A total number of 91 water bodies located throughout Catalunya (NE Iberian Peninsula) were sampled. Three species assemblages were observed: one for permanent freshwaters, another for temporary freshwaters, and a third one for saline waters (SW), since permanent and temporary saline water bodies had similar composition. Differences in salinity were associated with proportion of crustaceans versus insects and with singularity. Thus, saline ponds had a higher proportion of crustaceans, and lower values of singularity. Conductivity was significantly related to total (crustaceans plus insects) richness, and also related to insect richness. The main difference between the models obtained for crustacean species richness and insect species richness is the significance of landscape variables in the latter, and this fact could be related to the different dispersion types of these two faunal groups: active for insects versus passive for crustaceans. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Guest editors: R. Céréghino, J. Biggs, B. Oertli & S. Declerck The ecology of European ponds: defining the characteristics of a neglected freshwater habitat     

Spatio-temporal distribution of young fish in tributaries of natural and flow-regulated sections of a neotropical river in French Guiana

1. We investigated which environmental parameters control the variation in density, in space and time, of young stages of fish in tributaries of a natural and a flow-regulated section of the Sinnamary River, French Guiana.
2. The density of the progeny in most taxa varied in space and/or time. However, most non-Perciformes responded differently to space and/or time in the two sections.
3. Oxygen, turbidity and habitat structure (i.e. bank length, occurrence of undercut bank, richness in litter, vegetation and substratum) were important, as was the position of the sampling site relatively to the main channel in the downstream tributaries, in explaining the variation of density in space in both sections. Both habitat complexity and distance from the main channel protect young fish against unpredictable flow releases downstream from the Petit Saut dam.
4. Hydrological events played an important role in the temporal variation in densities of many fish taxa. The density of most early life and many juvenile stages (mostly Characiformes) was positively related to hydrological events.
5. Some fish taxa had reproductive habits which were relatively independent of abiotic factors, such as flow variability, and the density of their progeny did not vary with time.
6. The nursery areas of more than 45% of species in the Sinnamary River have been degraded by flow regulation.     

Patterns of fish community composition along a river affected by agricultural and urban disturbance in south-central Chile

Patterns of fish community composition in a south-central Chile river were investigated along the altitudinal-spatial and environmental gradient and as a function of anthropogenic factors. The spatial pattern of fish communities in different biocoenotic zones of the Chillan River is influenced by both natural factors such a hydrologic features, habitat, and feeding types, and also by water quality variables which can reduce the diversity and abundance of sensitive species. A principal component analysis incorporating both water quality parameters and biomarker responses of representative fish species was used to evaluate the status of fish communities along the spatial gradient of the stream. The abundance and diversity of the fish community changed from a low in the upper reaches where the low pollution-tolerant species such as salmonid dominated, to a reduced diversity in the lower reaches of the river where tolerant browser species such as cypriniformes dominated. Even though the spatial pattern of fish community structure is similar to that found for the Chilean Rivers, the structure of these communities is highly influenced by human disturbance, particularly along the lower reaches of the river. Handling editor: C. Sturmbauer