We measured selenium (Se) speciation in the waters of 16 lakes located near two major metal smelters and compared it to Se concentrations in a potential biomonitor, the planktivorous insect Chaoborus. We used this sentinel because planktonic algae and crustaceans, which are lower in the trophic chain leading to Chaoborus, are more difficult to separate and identify to species, whereas many fish species are not obligate planktivores. Percentages of selenate and organo-Se were generally higher in acidic lakes, whereas those of selenite were usually greater in alkaline waters. Chaoborus Se concentrations varied widely among lakes and, with the exception of a single high-sulfate lake, were significantly and highly correlated with those of dissolved organo-Se plus selenate (Se(VI)). We suggest that Chaoborus larvae would be highly effective for monitoring the Se-exposure of planktonic food webs in lakes.

The usage of inadequately processed industrial waste water (WW) can lead to strong soil alkalinity and soil salinization of agricultural fields with negative consequences on soil properties and biota. Gypsum as a soil amendment to saline-sodic soils is widely used in agricultural fields to improve their soil physical, chemical and hence biological properties. This study aimed at analysing the effects of intensive WW irrigation on the structure and composition of soil-dwelling arthropods on spinach fields (Spinacia oleracea L.) in a West African urban vegetable production system. We used gypsum as a soil amendment with the potential to alleviate soil chemical stress resulting in a potentially positive impact on soil arthropods. A total of 32 plots were established that showed a gradient in soil pH ranging from slight to strong soil alkalinity and that were irrigated with WW (n = 12) or clean water (CW; n = 20), including eight plots into which gypsum was incorporated. Our study revealed a high tolerance of soil-dwelling arthropods for alkaline soils, but spinach fields with increased soil electrical conductivity (EC) showed a reduced abundance of Hymenoptera, Diptera and Auchenorrhyncha. Arthropod abundance was positively related to a dense spinach cover that in turn was not affected by WW irrigation or soil properties. Gypsum application reduced soil pH but increased soil EC. WW irrigation and related soil pH affected arthropod composition in the investigated spinach fields which may lead to negative effects on agronomical important arthropod groups such as pollinators and predators.

Artificial illumination at night represents an increasingly concerning threat to ecosystems worldwide, altering persistence, behaviour, physiology and fitness of many organisms and their mutual interactions, in the long-term affecting ecosystem functioning. Bats are very sensitive to artificial light at night because they are obligate nocturnal and feed on insects which are often also responsive to lights. Here we tested the effects of LED lighting on prey-predator interactions at riverine ecosystems, using bats and their insect prey as models, and compared bat and insect reactions in terms of bat activity and prey insect abundance and diversity, respectively, on artificially lit vs. unlit nights. Artificial light influenced both insect and bat assemblages in taxon-specific directions: insect abundances increased at lit sites, particularly due to an increase in small dipterans near the light source. Composition of insect assemblages also differed significantly between lit and unlit sites. Total bat activity declined at lit sites, but this change was mainly due to the response of the most abundant species, Myotis daubentonii, while opportunistic species showed no reaction or even an opposite pattern (Pipistrellus kuhlii). We show that artificial lighting along rivers may affect trophic interactions between bats and insects, resulting in a profound alteration of community structure and dynamics.

Glyphosate-based herbicides are the world’s most consumed agrochemicals, and they are commonly used in various agroecosystems, including forests, as well as in urban zones and gardens. These herbicides are sold as formulations containing adjuvants. Other tank-mixing adjuvants (most often surfactants) are commonly added to these formulations prior to application. According to the manufacturers of agrochemicals, such tank mixes (as these are known in agronomic and horticultural practice) have modified properties and perform better than do the herbicides as used alone. The effects of these tank mixes on the environment and on beneficial arthropods are almost unknown. Therefore, we studied whether a herbicide formulation mixed with adjuvant has modified effects on one of the most common genera of ground-dwelling wolf spiders vis-à-vis the herbicide formulation and adjuvants themselves. Specifically, we studied the synergistic effect in the laboratory on the predatory activity (represented by the number of killed flies) of wolf spiders in the genus Pardosa after direct treatment using the glyphosate-based herbicide formulation Roundup klasik Pro®, Roundup klasik Pro® in a mixture with the surfactant Wetcit®, Roundup klasik Pro® in a mixture with the surfactant Agrovital®, and the surfactants alone. We found that pure surfactants as well as herbicide-and-surfactants tank mixes significantly decrease the predatory activity of Pardosa spiders in the short term even as Roundup klasik Pro® did not itself have any such effect. Our results support the hypothesis that plant protection tank mixes may have modified effect on beneficial arthropods as compared to herbicide formulations alone. Therefore, testing of pesticide tank mixes is highly important, because it is these tank mixes that are actually applied to the environment.

MeHg biomagnification by the phantom midge Chaoborus in relation to MeHg concentrations in their prey and its migratory behavior was investigated in two Canadian Precambrian Shield lakes. Three Chaoborus species with contrasted migratory behavior were collected in a fishless and a fish-inhabited lake. All species accumulated MeHg through their ontogenic development. In the lake inhabited by fish, all instars of Chaoborus punctipennis displayed a marked migratory behavior and were unable to biomagnify MeHg, whereas in the fishless lake, Chaoborus americanus and Chaoborus trivittatus biomagnified MeHg. Reduced biomagnification capacity of C. trivittatus, the coexisting species living with C. americanus, was also ascribed to a progressive vertical segregation with age. Growth dilution, amount and type of prey items or trophic position could not explain the different patterns of biomagnification. Our findings demonstrate that the most common invertebrate predator of temperate planktonic food webs can biomagnify mercury, contrarily to previous reports.

In the artificial reservoir of the Isahaya reclaimed land, Nagasaki, Japan, algal blooms have become an annual event, dominated primarily by the microcystin (MC) producing cyanobacteria Microcystis aeruginosa. Although the majority of MCs are either degraded by bacteria or washed out to sea, some remain in the sediment of the reservoir and bay throughout the year. As a result, they also accumulate in aquatic organisms (mullet, oyster, etc.) that inhabit the reservoir and surrounding areas, as well as midge flies that spend their larval period in the bottom of the reservoir. Accordingly, MCs also accumulate in the predators of these organisms, allowing the toxin to spread from the hydrosphere to terrestrial ecosystems. The most effective method for resolving this potentially dangerous condition is to introduce seawater into the reservoir by opening the drainage gates at high tide.

Lake Mallusjärvi in the cultural landscape of Mallusjoki, southern Finland, suffers from algal blooms during summers and oxygen depletions during winters due to increased nutrient input resulting from extensive agricultural activities in the catchment. In this study, a sediment profile from the lake was studied using fossil midge (Diptera: Nematocera) analysis and a hypolimnetic oxygen transfer function was applied to establish baseline conditions of hypolimnetic oxygen. In addition, physical properties of the sediment were determined. The inferred late winter hypolimnetic oxygen content was elevated in the beginning of the sediment sequence, but decreased dramatically at ca. 200 cal BP, as the inferred values indicated frequently anoxic condition coinciding with increased agricultural use in the catchment. The results indicated that dramatic changes have occurred in the taxon composition. The high-oxygen Stempellina–Ablabesmyia monilis-type community first changed to moderate-oxygen Procladius–Stempellinella community, and finally to low-oxygen Microchironomus tener–Chironomus plumosus-type community, following the eutrophication process. These changes in macrobenthic faunal assemblages reproduced considerably higher inferred hypolimnetic oxygen reference condition values for hypolimnetic oxygen, compared to the present status.

Urban streams are degraded through multiple mechanisms, including severely altered flow regimes, elevated concentrations of waterborne contaminants, removal of riparian vegetation and the loss of a mosaic of heterogeneous aquatic habitats. Engineering of urban stream reaches using concrete is a widespread and extreme case of deliberate alteration of flow regimes and concomitant habitat simplification. To assess the effect of such engineering practices on stream ecosystems, we compared aquatic macroinvertebrate communities from concrete-lined engineered urban reaches, non-engineered urban reaches with natural substrates and reference reaches flowing through minimally disturbed forested subcatchments and with natural substrates, in the Sydney metropolitan region, Australia. The communities from all urban reaches were impoverished and distinctly different from more diverse communities in forested reference reaches. Despite low aquatic habitat heterogeneity, engineered urban reaches had very high abundances of Diptera and some other tolerant taxa. Diptera and/or Gastropoda were dominant in non-engineered urban reaches. Multivariate community structures were dissimilar between the urban reaches and forested reference reaches and between non-engineered and engineered urban reaches. However, the low family-level richness and SIGNAL scores in both urban reach types indicated they were severely ecological impaired, whether engineered or not. Most macroinvertebrate taxa in the regional pool that were hardy enough to inhabit urban reaches with natural substrates were also present in nearby concreted reaches. The results add weight to the growing evidence that in urban landscapes, regional-scale changes in water quality and flow regimes limit the establishment of diverse macroinvertebrate communities, which cannot be addressed through the provision of increased reach-scale habitat heterogeneity.