Freshwater fish and mussel diversity is declining at an alarming rate across North America. Human land uses and disturbances within watersheds have been implicated as the primary cause of declines. In this paper, we demonstrate the utility of land use/land cover (LULC) variables in species distribution modeling and conservation planning using a straightforward multiscale approach for prioritizing freshwater fish and mussel conservation areas in the upper Green River catchment (Ohio River basin, USA). We developed distribution and species richness models for 10 uncommon fishes and 14 rare mussels using multiscale landscape data and boosted regression tree (BRT) analyses based on LULC composition and pattern, geology composition, and soil composition data. We then used probability of occurrence, endemicity, prevalence, trend and range of individual species to estimate the conservation value of each stream reach. Conservation areas were defined for three spatial scales nested within the catchment management zone (focal areas, riparian management buffer and subcatchment management zone) using a simple optimization technique. Priority conservation areas were located primarily in the eastern (upper Green River) and southern (upper Barren River) portions of the catchment. We found that focal species richness is explained most by soil composition in the subcatchment. However, nested within the subcatchment scale focal species richness responded positively to percent forest and negatively to patch density of developed/exposed land in the reach buffer. For both the reach and riparian buffers, retaining forested tracts of land and limiting the level of development and fragmentation would benefit the focal species.

Extirpation or even extinction of freshwater invertebrate species is a neglected conservation issue; declines in abundance and spatial distribution for freshwater invertebrates are far less documented than for vertebrate species. In the Minho River tidal freshwater wetlands (northwest of Iberian Peninsula), a rapid decline in density and biomass of the bivalve Pisidium amnicum was recorded at 16 different sites over seven years, from 2004 to 2010, without any sign of a potential recovery. Mean density values reached more than 80 ind.m−2 in 2004, but declined to less than 1 ind.m−2 in 2009 and 2010. An identical declining trend was observed for biomass. A significant reduction in the spatial distribution also occurred. The abiotic changes resulting from the 2005 heat wave and possibly the negative interactions imposed by the non-indigenous invasive bivalve Corbicula fluminea were the main factors responsible for the declining trends. Given the very low density, P. amnicum is facing a serious risk of extirpation in this ecosystem and conservational measures are urgently needed.

The golden mussel Limnoperna fortunei was introduced into Argentina in 1991 and has since been spreading through the Plata and Guaíba basins at a rate of 240 km.year−1. To assess their ability to invade the Andean tributaries of the Plata Basin (Pilcomayo, Bermejo and Salado del Norte rivers), their current range was assessed and related to the abiotic parameters of sites where they were present and absent. These data were then compared with their known tolerances to identify possible barriers to invasion. Outputs suggested that three environmental parameters are barriers to invasion: salinity and river flow intermittence in different sectors of the rivers Pilcomayo and Salado del Norte, and concentration of suspended sediments in the Bermejo River and in the upper reaches of the Salado del Norte and Pilcomayo rivers. The importance of these findings is discussed in relation to using environmental data to infer the invasion possibilities and the utility of environmental data to better understand invasion patterns and processes.

River floodplains and riparian areas are often considered efficient traps for sediment and sediment-associated nutrients such as nitrogen (N) and phosphorus (P). However, few studies have focused on the fate of sediment-bound N and P after deposition on floodplains. In this study, the leaching of N and P from sediment deposited on a Danish-restored floodplain was quantified by placing trapped sediment samples under a rainfall simulator and exposing them to in situ temperatures and precipitation for two months. The nitrate release was 2.72–1600 μg NO3-N.g−1 DW which corresponded to 0.06–6.42% of the total nitrogen contained in the sediment. Total dissolved phosphorus (TDP) release was 0.44–3.17 μg P.g−1 DW, corresponding to 0.021–0.065% of the TP content of the sediment. Our results indicate that N and P release from floodplain sediment subjected to rainfall events is very low, which should be considered when applying floodplain restoration to mitigate the load of N and P to rivers.

A microcosm experiment was carried out in order to test the effect of the herbicide metolachlor on river periphytic diatoms and to find potential diatom bioindicators of contamination. Effects were investigated at different biological organization levels (biofilm, diatom community, population and individual levels). The colonization of glass substrates by natural biofilm in artificial streams did not vary quantitatively between control and contaminated conditions (5 and 30 μg.L−1). However, non-parametric multivariate analysis of variance revealed a significant difference between contaminated and control diatom communities with regard to species composition. The difference was due to the greater development of probably tolerant species in the presence of the herbicide (e.g., Planothidium frequentissimum, Planothidium lanceolatum, Amphora montana, Surirella brebissonii and Nitzschia gracilis). An increase in the occurrence of abnormal forms was observed in relation to metolachlor concentration. In particular, up to 8% of the frustules of the species Surirella angusta exhibited prominent deformities. Monospecific acute toxicity tests were then performed on two species to estimate toxicity parameters based on growth inhibition. These tests also confirmed the teratogenic effect of the herbicide on S. angusta. This study shows that low concentrations of metolachlor in natural streams may significantly alter diatom community structure and that abnormal diatom forms should be taken into account in water contamination assessment.

Diel dissolved oxygen (DO) measurements can be used to estimate water metabolism of aquatic systems, in particular, lakes, lagoons and streams in terms of gross primary production (GPP), ecosystem respiration (Reco) and net ecosystem production (NEP). One of the main assumptions in the calculation of lake metabolism is that Reco is the same for daytime (Rdaytime) and nighttime (Rdarkhr). This study aimed at testing the equal Rdaytime and Rdarkhr assumption to estimate GPP, Reco and NEP in a littoral zone of a temperate shallow lake (Lake Yeniçağa) in northwestern Turkey with and without the assumption. Based on the equal Rdarkhr and Rdaytime assumption, values calculated for GPP and Rdaytime were different than those based on the different Rdarkhr and Rdaytime assumption (P<0.001). GPP was lower by 7.5% in July, 49.6% in September and 14.9% in October, while Reco was lower by 5.9% in July and 55.8% in September. GPP was higher by 8.9% in August and 55% in November, while Reco was higher by 7.8% in August and 23.9% in November.

Seasonal dynamics of zooplankton were investigated in three different habitats of the shallow and temperate Kačležský pond (Czech Republic) during 2003–2004. The studied habitats included the limnetic zone and two littoral zones, each dominated by a different type of emergent macrophyte, reed grass (Glyceria maxima) and common reed (Phragmites australis). Species richness (calculated as number of taxa) was higher in both littoral zones than in the limnetic zone. The seasonal development of limnetic and littoral zooplankton communities differed. In contrast to the two littoral zones, close correlation with chlorophyll-a concentration was found for rotifers and cladocerans in the limnetic zone. Moreover, cladocerans inhabiting littoral areas (mainly Bosmina longirostris) reached annual maxima during spring when chlorophyll-a concentrations were low.

Similar to other Mediterranean lakes, Lake Vela displays a marked dominance of alien species, but the impact of such an assemblage on the lower trophic levels of shallow eutrophic lakes has been overlooked. In this study, zooplanktivory in the omnivorous fish assemblage of Lake Vela was examined from April to October 2003 (and also in January 2004). During this period, ichthyocenosis was characterized by abundance of juvenile fish, which strongly depended on zooplankton. Adult mosquitofish (Gambusia holbrooki) and pumpkinseed (Lepomis gibbosus) foraged on the same zooplanktonic prey than juveniles, although planktivory was less important in larger fish. Using multivariate analysis, it was possible to attribute most of the variability in planktivory to resource availability, as both fish foraged on the most abundant prey in each month. Albeit this opportunistic behaviour, mosquitofish was found to be positively selective towards small-sized littoral cladocerans, while pumpkinseed displayed positive selection towards Alona and Daphnia. In the absence of more efficient planktivores, pumpkinseed is now the main planktivore in Lake Vela and the main predator of Daphnia. However, due to low densities of Daphnia during most of the study period, Daphnia was virtually absent from the diet of pumpkinseed from June to October, a period during which this benthi–planktivore foraged chiefly on less-rewarding planktonic prey (small-sized cladocerans and cyclopoid copepods). Mosquitofish was an important planktivore in littoral and structured habitats. Flexible foraging behaviour partly explains the success of these two species in Lake Vela.

The habitats of 356 phytocoenoses dominated by 15 species of aquatic plants were investigated. Among the properties of water, Na+, pH, total Fe, Ca2+, NO3−, SO42−, hardness and COD-KMnO4 were the most important in differentiating the habitats of the phytocoenoses studied. Considerable physicochemical differences were found between the waters of the phytocoenoses of Ranunculus circinatus (hard waters rich in Na+), Nuphar pumila (soft waters with high levels of total Fe), Elodea canadensis, Ceratophyllum demersum (alkaline waters) and Stratiotes aloides (waters containing high concentrations of Ca2+ and SO42−). The substrate properties that best differentiated the habitats compared were PO43−, hydration, organic matter content, total N, dissolved SiO2, Ca2+, Na+ and pH. Patches of R. circinatus inhabited substrates containing the highest levels of PO43−. Those of S. aloides were associated with substrates poor in PO43−. Patches of C. demersum were confined to substrates rich in total N. Phytocoenoses of R. circinatus were associated with large lakes, whereas those of N. pumila were restricted mostly to smaller lakes. The deepest parts of lakes were inhabited by Potamogeton lucens. Phytocoenoses of S. aloides occurred mostly in shallow waters, on thick sediments. The investigated phytocoenoses also represent different stages of succession. The phytocoenoses of Potamogeton perfoliatus, R. circinatus, Myriophyllum spicatum and Polygonum amphibium, which develop on mineral substrates, initiate the process of succession, whereas those of Myriophyllum verticillatum, Nymphaea candida, Nymphaea alba, N. pumila and S. aloides, which inhabit highly hydrated organic substrates, are characteristic of the late stages of succession.

Microvelia picinguaba sp. nov., Microvelia ubatuba sp. nov., Paravelia gabrielae sp. nov. and Rhagovelia pseudotijuca sp. nov. are described. The male of Microvelia ioana is described. Microvelia mimula and Microvelia aemulana are synonymized. Microvelia hinei, M. ioana, Microvelia longipes, Microvelia pulchella, Microvelia venustatis, Oiovelia brasiliensis, Oiovelia cunucunumana, Paravelia basalis, Paravelia itatiayana, Rhagovelia denticulata, Rhagovelia hambletoni, Rhagovelia janeira, Rhagovelia robusta, Rhagovelia tenuipes, Rhagovelia zela and Stridulivelia ayacucho are recorded for the first time from São Paulo State. New locality records are given for Husseyella diffidens, Rhagovelia accedens, Rhagovelia aiuruoca, Rhagovelia henryi, Rhagovelia lucida, Rhagovelia modesta, Rhagovelia occulcata, Rhagovelia trepida and Rhagovelia triangula.