Pesticide effects on macroinvertebrates and leaf litter decomposition in areas with traditional agriculture.

Traditional forms of agriculture have created and preserved heterogeneous landscapes characterized by semi-natural meadows and pastures, which have high conversation value for biodiversity. Landscapes in Central and Eastern European countries with traditional agriculture are a stronghold for pollinators, butterflies and amphibians, which have declined in other parts of Europe. Despite different landscape structures, agriculture-associated pesticide exposure in streams can be similarly high as in Western Europe. This raises the question whether the heterogeneous landscape can buffer a temporary water quality decline by agriculture. We investigated the influence of landscape heterogeneity and water quality, in particular pesticide exposure, on macroinvertebrate communities in 19 small streams in Central Romania. We sampled the macroinvertebrate community, assessed the ecosystem function of leaf litter decomposition and analyzed the parasite prevalence in Baetis sp. and Gammarus balcanicus. No association between pesticide toxicity towards macroinvertebrates and several macroinvertebrate metrics was found. However, the level of pesticide toxicity was generally high, constituting a rather short gradient, and the pesticide indicator SPEARpesticides implied pesticide-driven community change in all sites. Landscape heterogeneity and forested upstream sections were among the most important drivers for the macroinvertebrate metrics, indicating increased dispersal and recolonization success. Agricultural land use in the catchment was negatively associated with vulnerable macroinvertebrate taxa such as Ephemeroptera, Plecoptera and Trichoptera. G. balcanicus dominated the shredder taxa and its abundance was positively associated with the pesticide indicator SPEARpesticides. Parasite prevalence in G. balcanicus increased with extensive land use (pastures and forests), whereas it decreased with arable land. Our results suggest that heterogeneous landscapes with structures of low-intensive land use may buffer the effects of agricultural land use and facilitate dispersal and recolonization processes of pesticide-affected macroinvertebrate communities.

Spatio-temporal insights into microbiology of the freshwater-to-hypersaline, oxic-hypoxic-euxinic waters of Ursu Lake.

Ursu Lake is located in the Middle Miocene salt deposit of Central Romania. It is stratified, and the water column has three distinct water masses: an upper freshwater-to-moderately saline stratum (0-3 m), an intermediate stratum exhibiting a steep halocline (3-3.5 m), and a lower hypersaline stratum (4 m and below) that is euxinic (i.e. anoxic and sulphidic). Recent studies have characterized the lake's microbial taxonomy and given rise to intriguing ecological questions. Here, we explore whether the communities are dynamic or stable in relation to taxonomic composition, geochemistry, biophysics, and ecophysiological functions during the annual cycle. We found: (i) seasonally fluctuating, light-dependent communities in the upper layer (≥0.987-0.990 water-activity), a stable but phylogenetically diverse population of heterotrophs in the hypersaline stratum (water activities down to 0.762) and a persistent plate of green sulphur bacteria that connects these two (0.958-0.956 water activity) at 3-3.5 to 4 m; (ii) communities that might be involved in carbon- and sulphur-cycling between and within the lake's three main water masses; (iii) uncultured lineages including Acetothermia (OP1), Cloacimonetes (WWE1), Marinimicrobia (SAR406), Omnitrophicaeota (OP3), Parcubacteria (OD1) and other Candidate Phyla Radiation bacteria, and SR1 in the hypersaline stratum (likely involved in the anaerobic steps of carbon- and sulphur-cycling); and (iv) that species richness and habitat stability are associated with high redox-potentials. Ursu Lake has a unique and complex ecology, at the same time exhibiting dynamic fluctuations and stability, and can be used as a modern analogue for ancient euxinic water bodies and comparator system for other stratified hypersaline systems.

Paradise lost? Pesticide pollution in a European region with considerable amount of traditional agriculture.

Pesticide contamination of agricultural streams has widely been analysed in regions of high intensity agriculture such as in Western Europe or North America. The situation of streams subject to low intensity agriculture relying on human and animal labour, as in parts of Romania, remains unknown. To close this gap, we determined concentrations of 244 pesticides and metabolites at 19 low-order streams, covering sites from low to high intensity agriculture in a region of Romania. Pesticides were sampled with two passive sampling methods (styrene-divinylbenzene (SDB) disks and polydimethylsiloxane (PDMS) sheets) during three rainfall events and at base flow. Using the toxic unit approach, we assessed the toxicity towards algae and invertebrates. Up to 50 pesticides were detected simultaneously, resulting in sum concentrations between 0.02 and 37 µg L-1. Both, the sum concentration as well as the toxicities were in a similar range as in high intensity agricultural streams of Western Europe. Different proxies of agricultural intensity did not relate to in-stream pesticide toxicity, contradicting the assumption of previous studies. The toxicity towards invertebrates was positively related to large scale variables such as the catchment size and the agricultural land use in the upstream catchment and small scale variables including riparian plant height, whereas the toxicity to algae showed no relationship to any of the variables. Our results suggest that streams in low intensity agriculture, despite a minor reported use of agrochemicals, exhibit similar levels of pesticide pollution as in regions of high intensity agriculture.

Do agricultural pesticides in streams influence riparian spiders?

Freshwater ecosystems are coupled with their riparian area. Emerging insects are prey for predators in the riparian zone, enriching the terrestrial ecosystem with energy and nutrients. Stressors associated with agriculture can alter insect communities in water and on land, resulting in complex response patterns of terrestrial predators relying on prey from both systems. Examining the effects from individual agricultural stressors such as pesticides is hampered in landscapes with intensive agriculture where multiple stressors like habitat degradation and typically co-occur. In rural regions of Eastern Europe, traditional low intensity agriculture based on working animals and human labour prevails alongside intensive, mechanised agriculture. Assuming that low-intensity agriculture relies on no or limited pesticide use, whereas fertilizer use is similar across different agricultural intensities, such regions may allow to study in-stream pesticide effects independent from other stressors, such as nutrient input or habitat degradation. We examined the taxonomic and trait response of riparian spider communities to gradients of agricultural stressors and environmental variables in the region around Cluj-Napoca, Romania. Pesticide sampling was done using passive samplers in the streams adjacent to spider sampling sites. To capture spiders with different traits and survival strategies, we used multiple collection methods. Community composition was best explained by in-stream pesticide toxicity and shading of the stream bank, a proxy for the quality of the habitat. Species richness and the number of spider individuals were negatively associated with in-stream pesticide toxicity. In contrast, mean body size and shading preference of spider communities responded strongest to shading, whereas mean niche width (habitat preference for moisture and shading) responded strongest to the other environmental variables. Our study suggests that in-stream pesticide toxicity can influence riparian communities. The identification of mechanisms requires further studies targeting the potential contributions of direct toxicity and indirect effects from reduced aquatic and terrestrial prey availability.