Pesticides from wastewater treatment plant effluents affect invertebrate communities

We quantified pesticide contamination and its ecological impact up- and downstream of seven wastewater treatment plants (WWTPs) in rural and suburban areas of central Germany. During two sampling campaigns, time-weighted average pesticide concentrations (c_TWA) were obtained using Chemcatcher® passive samplers; pesticide peak concentrations were quantified with event-driven samplers. At downstream sites, receiving waters were additionally grab sampled for five selected pharmaceuticals. Ecological effects on macroinvertebrate structure and ecosystem function were assessed using the biological indicator system SPEAR_pesticides (SPEcies At Risk) and leaf litter breakdown rates, respectively. WWTP effluents substantially increased insecticide and fungicide concentrations in receiving waters; in many cases, treated wastewater was the exclusive source for the neonicotinoid insecticides acetamiprid and imidacloprid in the investigated streams. During the ten weeks of the investigation, five out of the seven WWTPs increased in-stream pesticide toxicity by a factor of three. As a consequence, at downstream sites, SPEAR values and leaf litter degradation rates were reduced by 40% and 53%, respectively. The reduced leaf litter breakdown was related to changes in the macroinvertebrate communities described by SPEAR_pesticides and not to altered microbial activity. Neonicotinoids showed the highest ecological relevance for the composition of invertebrate communities, occasionally exceeding the Regulatory Acceptable Concentrations (RACs). In general, considerable ecological effects of insecticides were observed above and below regulatory thresholds. Fungicides, herbicides and pharmaceuticals contributed only marginally to acute toxicity. We conclude that pesticide retention of WWTPs needs to be improved.

Pesticides are the dominant stressors for vulnerable insects in lowland streams

Despite elaborate regulation of agricultural pesticides, their occurrence in non-target areas has been linked to adverse ecological effects on insects in several field investigations. Their quantitative role in contributing to the biodiversity crisis is, however, still not known. In a large-scale study across 101 sites of small lowland streams in Central Europe, Germany we revealed that 83% of agricultural streams did not meet the pesticide-related ecological targets. For the first time we identified that agricultural nonpoint-source pesticide pollution was the major driver in reducing vulnerable insect populations in aquatic invertebrate communities, exceeding the relevance of other anthropogenic stressors such as poor hydro-morphological structure and nutrients. We identified that the current authorisation of pesticides, which aims to prevent unacceptable adverse effects, underestimates the actual ecological risk as (i) measured pesticide concentrations exceeded current regulatory acceptable concentrations in 81% of the agricultural streams investigated, (ii) for several pesticides the inertia of the authorisation process impedes the incorporation of new scientific knowledge and (iii) existing thresholds of invertebrate toxicity drivers are not protective by a factor of 5.3 to 40. To provide adequate environmental quality objectives, the authorisation process needs to include monitoring-derived information on pesticide effects at the ecosystem level. Here, we derive such thresholds that ensure a protection of the invertebrate stream community.

Competition increases toxicant sensitivity and delays the recovery of two interacting populations

We investigated how persistent competitive pressure alters toxicant sensitivity and recovery from a pesticide pulse at community level. Interacting populations of Daphnia (Daphnia magna) and Culex larvae (Culex pipiens molestus) were pulse-exposed (48 h) to the pyrethroid fenvalerate. The abundance and biomass of the populations were monitored by non-invasive image analysis. Shortly after exposure, Daphnia showed a concentration-response relationship with the toxicant with an LC₅₀ of 0.9 μg/L. Culex larvae were slightly less sensitive with an LC₅₀ of 1.7 μg/L. For both species, toxicant sensitivity increased with the population biomass of the respective species before exposure, which is explained by intraspecific competition. Several weeks after exposure to the highest treatment concentration of 1 μg/L, the slight differences in sensitivity between the two species were amplified to contrasting long-term effects due to interspecific competition: high interspecific competition impaired the recovery of Daphnia. Subsequently, Culex larvae profited from the slow recovery of Daphnia and showed an increased success of emergence. We conclude that, in natural systems where competition is present, such competitive processes might prolong the recovery of the community structure. Hence, natural communities might be disturbed for a longer period by toxic exposure than predicted from single-species tests alone.

Indication of pesticide effects and recolonization in streams

The agricultural use of pesticides leads to environmentally relevant pesticide concentrations that cause adverse effects on stream ecosystems. These effects on invertebrate community composition can be identified by the bio-indicator SPEAR_pesticides. However, refuge areas have been found to partly confound the indicator. On the basis of three monitoring campaigns of 41 sites in Central Germany, we identified 11 refuge taxa. The refuge taxa, mainly characterized by dispersal-based resilience, were observed only nearby uncontaminated stream sections and independent of the level of pesticide pressure. Through incorporation of this information into the revised SPEAR_pesticides indicator, the community structure specifically identified the toxic pressure and no longer depended on the presence of refuge areas. With regard to ecosystem functions, leaf litter degradation was predicted by the revised SPEAR_pesticides and the median water temperature at a site (R² = 0.38, P = 0.003). Furthermore, we designed the bio-indicator SPEAR_refuge to quantify the magnitude of general recolonization at a given stream site. We conclude that the taxonomic composition of aquatic invertebrate communities enables a specific indication of anthropogenic stressors and resilience of ecosystems.

Pesticide impact on aquatic invertebrates identified with Chemcatcher® passive samplers and the SPEAR(pesticides) index

Pesticides negatively affect biodiversity and ecosystem function in aquatic environments. In the present study, we investigated the effects of pesticides on stream macroinvertebrates at 19 sites in a rural area dominated by forest cover and arable land in Central Germany. Pesticide exposure was quantified with Chemcatcher® passive samplers equipped with a diffusion-limiting membrane. Ecological effects on macroinvertebrate communities and on the ecosystem function detritus breakdown were identified using the indicator system SPEARpesticides and the leaf litter degradation rates, respectively. A decrease in the abundance of pesticide-vulnerable taxa and a reduction in leaf litter decomposition rates were observed at sites contaminated with the banned insecticide Carbofuran (Toxic Units≥-2.8), confirming the effect thresholds from previous studies. The results show that Chemcatcher® passive samplers with a diffusion-limiting membrane reliably detect ecologically relevant pesticide pollution, and we suggest Chemcatcher® passive samplers and SPEARpesticides as a promising combination to assess pesticide exposure and effects in rivers and streams.

Automated Nanocosm test system to assess the effects of stressors on two interacting populations

There is a great need in environmental research for test systems that include ecologically important factors and that are also easy to use. We present here the automated test system Nanocosm, which is composed of populations of Daphnia magna and Culex pipiens molestus. The Nanocosm system allows the investigation of stressed populations in the presence of interspecific competition, which is a very important factor involved in the dynamics of ecosystems. With the Nanocosm system, the abundance and size structure of populations of both species are quantified by image analysis. The technique enables a time-efficient, non-invasive and reliable long-term monitoring of interactions between two aquatic populations. We recommend the Nanocosm system as a novel tool for the simplified integration of competition into environmental and ecotoxicological research as well as for the assessment of risk due to stressors.

Long-term effects of a catastrophic insecticide spill on stream invertebrates

Accidental spills or illegal discharges of pesticides in aquatic ecosystems can lead to exposure levels that strongly exceed authorized pesticide concentrations, causing major impacts on aquatic ecosystems. Such short-term events often remain undetected in regular monitoring programs with infrequent sampling. In early spring 2015, we identified a catastrophic pesticide spill with the insecticide cypermethrin in the Holtemme River, Germany. Based on existing pre-event macroinvertebrate community data, we monitored the effects and recovery of the macroinvertebrate community for more than two years after the spill. Strong short-term effects were apparent for all taxa with the exception of Chironomidae and Tubificidae. Effects could also be observed on the community level as total abundance, taxa number and biomass strongly decreased. Total abundance and taxa number showed a fast recovery. Regarding long-term effects, the total biomass remained substantially below the pre-contamination level (76%) until the end of the study. Also the abundances of three taxa (Gammarus, Leuctra, Limnius Ad.) did not return to levels prior to the spill even after 26 months. This lack of the taxon-specific recovery was likely due to their long generation time and a low migration ability due to a restricted connectivity between the contaminated site and uncontaminated stream sections. These factors proved to be stronger predictors for the recovery than the pesticide tolerance. We revealed that the biological indicators SPEARpesticides and share of Ephemeroptera, Plecoptera and Trichoptera (EPT) are not suitable for the identification of such extreme events, when nearly all taxa are eradicated. Both indicators are functioning only when repeated stressors initiate long-term competitive replacement of sensitive by insensitive taxa. We conclude that pesticide spills can have significant long-term effects on stream macroinvertebrate communities. Regular ecological monitoring is imperative to identify such ecosystem impairments, combined with analytical chemistry methods to identify the potential sources of spills.

The use of laser-assisted cart positioning significantly reduces the docking time of multimodular robotic systems

The Hugo RAS system is characterized by its multimodular design, which leads to an increased docking effort. Exact data for docking time and the learning curve is missing. We describe for the first time the use of a laser-guided cart positioning to reduce the docking time. In this prospective monocentric study, the docking time was evalutated for a consecutive series of pelvic surgeries with the Hugo RAS system. In a subgroup, a cross-line laser was adapted at the cart for positioning using fix points at the ceiling. The medical personnel were classified as "inexperienced" with ≤ 5 consecutive dockings and as "experienced" with > 5 consecutive dockings. From 10/2023 to 08/2024, 82 procedures were performed with the Hugo RAS. For the evaluation 75 procedures could be considered. The mean docking time was 7.6 ± 3.5 min. There was a reduction in docking time from 13.5 ± 3.7 min in the first 5 procedures to 4.4 ± 0.9 min in the last 5 procedures (p < 0.001). Docking with laser (n = 45) was faster than without laser (n = 30) (6.2 ± 2.5 vs. 9.8 ± 3.7 min, p < 0.001). Faster docking time was observed with inexperienced surgical nursing staff with laser than without laser (10.4 ± 3.7 vs. 5.4 ± 1.4 min; p < 0.001). With experienced nursing staff, the laser had no influence (6.6 ± 1.3 vs. 6.7 ± 2.9 min; p = 0.9). As a reference docking time for daVinci Xi procedures was 2.4 ± 1.7 min (n = 5). Laser-guided cart positioning has a significant impact on docking time, especially for unexperienced medical personnel. Especially in the times of experienced staff shortage, laser-guided cart positioning can save operating time.