Contaminant fluxes across ecosystems mediated by aquatic insects

Metals and organic contaminants in aquatic systems affect the coupling of aquatic and terrestrial ecosystems through two pathways: contaminant-induced effects on insect emergence and emergence-induced contaminant transfer. Consequently, the impact of aquatic contaminants on terrestrial ecosystems can be driven by modifications in the quantity and quality of adult aquatic insects serving as prey or contaminants entering terrestrial food webs as part of the diet of terrestrial predators. Here, we provide an overview of recent advances in the field, separating metals from organic contaminants due to their differential propensity to bioaccumulate and thus their potential contribution to either of the two pathways. Finally, this review highlights the knowledge gap in the relative impact of these pathways on terrestrial insectivores

Subsidy Quality Affects Common Riparian Web-Building Spiders: Consequences of Aquatic Contamination and Food Resource

Anthropogenic stressors can affect the emergence of aquatic insects. These insects link aquatic and adjacent terrestrial food webs, serving as high-quality subsidy to terrestrial consumers, such as spiders. While previous studies have demonstrated that changes in the emergence biomass and timing may propagate across ecosystem boundaries, the physiological consequences of altered subsidy quality for spiders are largely unknown. We used a model food chain to study the potential effects of subsidy quality: Tetragnatha spp. were exclusively fed with emergent Chironomus riparius cultured in the absence or presence of either copper (Cu), Bacillus thuringiensis var. israelensis (Bti), or a mixture of synthetic pesticides paired with two basal resources (Spirulina vs. TetraMin (R)) of differing quality in terms of fatty acid (FA) composition. Basal resources shaped the FA profile of chironomids, whereas their effect on the FA profile of spiders decreased, presumably due to the capacity of both chironomids and spiders to modify (dietary) FA. In contrast, aquatic contaminants had negligible effects on prey FA profiles but reduced the content of physiologically important polyunsaturated FAs, such as 20:4n-6 (arachidonic acid) and 20:5n-3 (eicosapentaenoic acid), in spiders by approximately 30% in Cu and Bti treatments. This may have contributed to the statistically significant decline (40%-50%) in spider growth. The observed effects in spiders are likely related to prey nutritional quality because biomass consumption by spiders was, because of our experimental design, constant. Analyses of additional parameters that describe the nutritional quality for consumers such as proteins, carbohydrates, and the retention of contaminants may shed further light on the underlying mechanisms. Our results highlight that aquatic contaminants can affect the physiology of riparian spiders, likely by altering subsidy quality, with potential implications for terrestrial food webs. (c) 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC

Aquatic contaminants reduce the quantity and nutritional quality of aquatic subsidy to riparian consumers

Neighboring ecosystems are connected by fluxes of organic and inorganic matter. At the aquatic-terrestrial interface, researchers have primarily focused on the magnitude of resource fluxes, while largely disregarding differences in their nutritional quality for consumers in the recipient ecosystem. Aquatic resources, such as emergent aquatic insects, contain substantially higher levels of physiologically important long-chain polyunsaturated fatty acids (long-chain PUFA) than terrestrial resources. Since animals cannot typically biosynthesize long-chain PUFA in quantities sufficient to meet their physiological demands, they must obtain these compounds through their diet. Aquatic subsidy by emergent aquatic insects can therefore benefit the physiological condition and breeding success of riparian consumers such as birds and spiders. However, aquatic contaminants may disrupt aquatic insect emergence, altering the quantity and nutritional quality of aquatic subsidy to recipient terrestrial systems. Despite its importance to local consumers, effects of aquatic contaminants on this process are poorly studied and understood. The primary aim of this thesis is therefore to assess the effects of aquatic contaminants on aquatic-to-terrestrial subsidy, focusing on FA fluxes, and to determine whether shifts in subsidy quality affect riparian consumers. Effects were examined in a set of complex laboratory bioassays that also considered environmental factors (e.g., basal food resource) to increase environmental relevance. Metals (i.e., cadmium, Cd and copper, Cu) substantially reduced aquatic insect emergence (up to 95%) and the flux of physiologically important long-chain PUFA (up to 80%) while being efficiently excreted during metamorphosis (reduction by ~90%). Given their relative scarcity in terrestrial ecosystems, local consumers may be particularly vulnerable to changes in the flux of physiologically important long-chain PUFA. Indeed, contaminant-induced alterations of aquatic subsidy quality can affect the physiological condition of riparian spiders, as suggested by a consistent decline in spider growth (40-50%), irrespective of the contaminant group (Cu, Bacillus thuringiensis var. israelensis (Bti) or a mixture of synthetic pesticides) to which their prey was exposed. Since spider neutral lipid FA contents were only reduced in two out of three contaminant treatments compared to the control (up to ~30%, Cu and Bti), this implies contaminant-dependent effect pathways modifying the transfer of energy within food webs at the aquatic-terrestrial interface. Furthermore, results from a multigeneration experiment point to a relatively constant reduction in aquatic insect emergence and thus sustained alteration in the aquatic-to-terrestrial subsidy. Finally, the basal resource quality and sex-specific differences in aquatic insects and terrestrial consumers may further complicate the assessment of contaminant-induced effects. This thesis therefore recommends to consider fluxes of long-chain PUFA to better understand and anticipate implications of aquatic contaminants on the aquatic-terrestrial meta-ecosystem and develop efficient measures to protect riparian systems and their communities

Mixture effects of a fungicide and an antibiotic: Assessment and prediction using a decomposer-detritivore system

Antimicrobials, such as fungicides and antibiotics, pose a risk for microbial decomposers (i.e., bacteria and aquatic fungi) and invertebrate detritivores (i.e., shredders) that play a pivotal role in the ecosystem function of leaf litter breakdown. Although waterborne toxicity and diet-related effects (i.e., dietary exposure and microorganism-mediated alterations in food quality for shredders) of fungicides and antibiotics on decomposer-detritivore systems have been increasingly documented, their joint effect is unknown. We therefore assessed waterborne and dietary effects of an antimicrobial mixture consisting of the fungicide azoxystrobin (AZO) and the antibiotic ciprofloxacin (CIP) on microbial decomposers and the shredder Gammarus fossarum using a tiered approach. We compared effect sizes measured in the present study with model predictions (i.e., independent action) based on published data. During a 7-day feeding activity assay quantifying waterborne toxicity in G. fossarum, the leaf consumption of gammarids was reduced by similar to 60 % compared to the control when subjected to the mixture at concentrations of each component causing a 20 % reduction in the same response variable when applied individually. Moreover, the selective feeding of gammarids during the food choice assay indicated alterations in food quality induced by the antimicrobial mixture. The food selection and, in addition, the decrease in microbial leaf decomposition is likely linked to changes in leaf-associated bacteria and fungi. During a long-term assay, energy processing, growth and energy reserves of gammarids were increased in presence of 15 and 500 mu g/L of AZO and CIP, respectively, through the dietary pathway. These physiological responses were probably driven by CIP-induced alterations in the gut microbiome or immune system of gammarids. In general, model predictions matched observed effects caused by waterborne exposure on the leaf consumption, energy processing and growth of gammarids during short- and long-term assays, respectively. However, when complex horizontal (bacteria and aquatic fungi) and vertical (leaf-associated microorganisms and shredders) interactions were involved, model predictions partly over- or underestimated mixture effects. Therefore, the present study identifies uncertainties of mixture effect predictions for complex biological systems calling for studies targeting the underlying processes and mechanisms

Policy Brief zum Zwischenbericht der wissenschaftlichen Evaluation des Bundesprogramms „Sprach-Kitas : Weil Sprache der Schlüssel zur Welt ist“ ; Die Bedeutung der zusätzlichen Fachberatungen und Kita-Tandems für die Implementation des neuen Querschnittsthemas Digitalisierung

Ziel ist die Untersuchung der Voraussetzung der Porgammbeteiligten hinsichtlich ihrer professionellen Kompetenzen zum Querschnittsthema Digitalisierung. Untersucht werden die strukturellen Voraussetzungen sowie zentrale Umsetzungsaspekte des Bundesprogramms und ihre Bedeutug für das Thema Digitalisierung

Metal Exposure and Sex Shape the Fatty Acid Profile of Midges and Reduce the Aquatic Subsidy to Terrestrial Food Webs

Aquatic micropollutants can be transported to terrestrial systems and their consumers by emergent aquatic insects. However, micropollutants, such as metals, may also affect the flux of physiologically important polyunsaturated fatty acids (PUFAs). As certain PUFAs have been linked to physiological fitness and breeding success of terrestrial consumers, reduced fluxes from aquatic systems could affect terrestrial populations and food webs. We chronically exposed larvae of the aquatic insect Chironomus riparius to a range of environmentally relevant sediment contents of cadmium (Cd) or copper (Cu) in a 28-day microcosm study. Since elevated water temperatures can enhance metals’ toxic effects, we used two temperature regimes, control and periodically elevated temperatures (heat waves) reflecting an aspect of climate change. Cd and Cu significantly reduced adult emergence by up to 95% and 45%, respectively, while elevated temperatures had negligible effects. Both metal contents were strongly reduced (∼90%) during metamorphosis. Furthermore, the chironomid FA profile was significantly altered during metamorphosis with the factors sex and metal exposure being relevant predictors. Consequently, fluxes of physiologically important PUFAs by emergent adults were reduced by up to ∼80%. Our results suggest that considering fluxes of physiologically important compounds, such as PUFAs, by emergent aquatic insects is important to understand the implications of aquatic micropollutants on aquatic-terrestrial meta-ecosystems