A research agenda for scaling up agroecology in European countries.

A profound transformation of agricultural production methods has become unavoidable due to the increase in the world's population, and environmental and climatic challenges. Agroecology is now recognized as a challenging model for agricultural systems, promoting their diversification and adaptation to environmental and socio-economic contexts, with consequences for the entire agri-food system and the development of rural and urban areas. Through a prospective exercise performed at a large interdisciplinary institute, INRAE, a research agenda for agroecology was built that filled a gap through its ambition and interdisciplinarity. It concerned six topics. For genetics, there is a need to study genetic aspects of complex systems (e.g., mixtures of genotypes) and to develop breeding methods for them. For landscapes, challenges lie in effects of heterogeneity at multiple scales, in multifunctionality and in the design of agroecological landscapes. Agricultural equipment and digital technologies show high potential for monitoring dynamics of agroecosystems. For modeling, challenges include approaches to complexity, consideration of spatial and temporal dimensions and representation of the cascade from cropping practices to ecosystem services. The agroecological transition of farms calls for modeling and observational approaches as well as for creating new design methods. Integration of agroecology into food systems raises the issues of product specificity, consumer behavior and organization of markets, standards and public policies. In addition, transversal priorities were identified: (i) generating sets of biological data, through research and participatory mechanisms, that are appropriate for designing agroecological systems and (ii) collecting and using coherent sets of data to enable assessment of vulnerability, resilience and risk in order to evaluate the performance of agroecological systems and to contribute to scaling up. The main lessons learned from this collective exercise can be useful for the entire scientific community engaged in research into agroecology.

Effect of thiram and of a hydrocarbon mixture on freshwater macroinvertebrate communities in outdoor stream and pond mesocosms: I. Study design, chemicals fate and structural responses.

Higher-tier ecological risk assessment (ERA) in mesocosms is commonly performed in lotic or lentic experimental systems. These systems differ in their physico-chemical and hydrological properties, leading to differences in chemical fate, community characteristics and potential recovery. This raises the issue of the relevance and sensitivity of community-level endpoints in different types of mesocosms. In this study, macroinvertebrate abundance and biomass estimates were used to assess the effects of a dithiocarbamate fungicide, thiram (35 and 170 µg l(-1)), and a petroleum middle distillate (PMD; 0.01, 0.4, 2 and 20 mg l(-1)) in outdoor stream and pond mesocosms. Streams were continuously treated during 3 weeks followed by a 2-month long post-treatment period. Ponds were treated weekly for 4 weeks, followed by a 10-month long post-treatment period. Taxonomic structure of macroinvertebrate communities was characterized using the α, ß and γ components of taxa richness, Shannon and Gini-Simpson indices. Computations were based either on abundance or biomass data. Results clearly highlighted that the effects of chemicals depended on the exposure regime (for thiram) and type of system (for the PMD). Causes of the differences between streams and ponds in the magnitude and nature of effects include differential sensitivity of taxa dwelling in lentic and lotic systems and the influence of hydrology (e.g., drift from upstream) and mesocosm connectivity on recovery dynamics. This study also showed complementarities in the use of both types of mesocosms to improve the characterization of chemical effects on communities in ERA.

Effect of thiram and of a hydrocarbon mixture on freshwater macroinvertebrate communities in outdoor stream and pond mesocosms: II. Biological and ecological trait responses and leaf litter breakdown.

Higher-tier ecological risk assessment of chemicals often relies upon studies in dynamic and/or static mesocosms. Physico-chemical and hydrological properties of each type of mesocosm result in specific chemicals fate, community functioning, and potential recovery. In the present study, macroinvertebrate abundance- and biomass-weighted biological and ecological trait matrices were used to assess the effects of a dithiocarbamate fungicide, thiram (35 and 170 µg l(-1)), and of a petroleum middle distillate (0.01, 0.4, 2 and 20 mg l(-1)) in outdoor stream and pond mesocosms. Trait sensitivity was characterized using functional diversity indices and trait modality distributions to assess the influence of the type of experimental systems and the ability of traits to disentangle chemical-induced effects from temporal and stochastic variations. In addition, leaf litter breakdown was used as an integrative functional endpoint. Regardless to the substance, treatments had a direct effect on the functional structure of benthic macroinvertebrate communities in streams but not in ponds, suggesting that global functional responses to chemicals are system-specific. Although both substances had an effect in streams, differences were noticed in the nature of the affected traits suggesting that chemical mode of action plays a role in functional alterations. This was illustrated by the link between negative effects of chemical exposure on detritivorous taxa and reduced litter breakdown rate in streams. Therefore, characterisation of macroinvertebrate biological traits associated with the measurement of a functional process such as litter breakdown may provide a comprehensive understanding of the effects occurring in mesocosms exposed to organic chemicals.

A coordinated set of ecosystem research platforms open to international research in ecotoxicology, AnaEE-France.

The infrastructure for Analysis and Experimentation on Ecosystems (AnaEE-France) is an integrated network of the major French experimental, analytical, and modeling platforms dedicated to the biological study of continental ecosystems (aquatic and terrestrial). This infrastructure aims at understanding and predicting ecosystem dynamics under global change. AnaEE-France comprises complementary nodes offering access to the best experimental facilities and associated biological resources and data: Ecotrons, seminatural experimental platforms to manipulate terrestrial and aquatic ecosystems, in natura sites equipped for large-scale and long-term experiments. AnaEE-France also provides shared instruments and analytical platforms dedicated to environmental (micro) biology. Finally, AnaEE-France provides users with data bases and modeling tools designed to represent ecosystem dynamics and to go further in coupling ecological, agronomical, and evolutionary approaches. In particular, AnaEE-France offers adequate services to tackle the new challenges of research in ecotoxicology, positioning its various types of platforms in an ecologically advanced ecotoxicology approach. AnaEE-France is a leading international infrastructure, and it is pioneering the construction of AnaEE (Europe) infrastructure in the field of ecosystem research. AnaEE-France infrastructure is already open to the international community of scientists in the field of continental ecotoxicology.

Genetic variation of Lymnaea stagnalis tolerance to copper: A test of selection hypotheses and its relevance for ecological risk assessment.

The use of standardized monospecific testing to assess the ecological risk of chemicals implicitly relies on the strong assumption that intraspecific variation in sensitivity is negligible or irrelevant in this context. In this study, we investigated genetic variation in copper sensitivity of the freshwater snail Lymnaea stagnalis, using lineages stemming from eight natural populations or strains found to be genetically differentiated at neutral markers. Copper-induced mortality varied widely among populations, as did the estimated daily death rate and time to 50% mortality (LT50). Population genetic divergence in copper sensitivity was compared to neutral differentiation using the QST-FST approach. No evidence for homogenizing selection could be detected. This result demonstrates that species-level extrapolations from single population studies are highly unreliable. The study provides a simple example of how evolutionary principles could be incorporated into ecotoxicity testing in order to refine ecological risk assessment.

Analysing chemical-induced changes in macroinvertebrate communities in aquatic mesocosm experiments: a comparison of methods.

Mesocosm experiments that study the ecological impact of chemicals are often analysed using the multivariate method 'Principal Response Curves' (PRCs). Recently, the extension of generalised linear models (GLMs) to multivariate data was introduced as a tool to analyse community data in ecology. Moreover, data aggregation techniques that can be analysed with univariate statistics have been proposed. The aim of this study was to compare their performance. We compiled macroinvertebrate abundance datasets of mesocosm experiments designed for studying the effect of various organic chemicals, mainly pesticides, and re-analysed them. GLMs for multivariate data and selected aggregated endpoints were compared to PRCs regarding their performance and potential to identify affected taxa. In addition, we analysed the inter-replicate variability encountered in the studies. Mesocosm experiments characterised by a higher taxa richness of the community and/or lower taxonomic resolution showed a greater inter-replicate variability, whereas variability decreased the more zero counts were encountered in the samples. GLMs for multivariate data performed equally well as PRCs regarding the community response. However, compared to first axis PRCs, GLMs provided a better indication of individual taxa responding to treatments, as separate models are fitted to each taxon. Data aggregation methods performed considerably poorer compared to PRCs. Multivariate community data, which are generated during mesocosm experiments, should be analysed using multivariate methods to reveal treatment-related community-level responses. GLMs for multivariate data are an alternative to the widely used PRCs.

Structural and biological trait responses of diatom assemblages to organic chemicals in outdoor flow-through mesocosms.

The sensitivity of diatom taxonomy and trait-based endpoints to chemicals has been poorly used so far in Environmental Risk Assessment. In this study, diatom assemblages in outdoor flow-through mesocosms were exposed to thiram (35 and 170 µg/L), and a hydrocarbon emulsion (HE; 0.01, 0.4, 2 and 20 mg/L). The effects of exposure were assessed for 12 weeks, including 9 weeks post-treatment, using taxonomic structure and diversity, bioindication indices, biological traits, functional diversity indices, indicator classes and ecological guilds. For both chemicals, diversity increased after the treatment period, and responses of ecological traits were roughly identical with an abundance increase of motile taxa tolerant to organic pollution and decrease of low profile taxa. Bioindication indices were not affected. Traits provided a complementary approach to biomass measurements and taxonomic descriptors, leading to a more comprehensive overview of ecological changes due to organic chemicals, including short- and long-term effects on biofilm structure and functioning.

Isotopic niche metrics as indicators of toxic stress in two freshwater snails.

Descriptors of trophic niche and of food web structure and function have been suggested as integrative and sensitive endpoints of toxicant effects. In the present study, carbon and nitrogen stable isotope signatures were used to assess the effects of the dithiocarbamate fungicide thiram (35 and 170µg/L nominal concentrations) and of a petroleum distillate (0.01, 0.4, 2 and 20mg/L nominal loadings as Hydrocarbon Emulsion or Hydrocarbon Water Accommodated Fraction) on the trophic niche of two freshwater gastropods in artificial streams (Radix peregra) and ponds (Lymnaea stagnalis). Results were analyzed using classical univariate statistical methods and recently proposed uni- and multivariate metrics of the realized trophic niche of species. The trophic niche metrics were highly sensitive to both types of chemicals, but exposure resulted in different response patterns according to the nature of the tested compound. Thiram clearly affected gastropod trophic niche leading to a change in the food resources used and resulting in trophic niche expansion (i.e., increase of diversity of used resources, especially dead animals) or trophic niche contraction (i.e., decrease of diversity of used resources) across time. Both gastropod taxa exposed to hydrocarbons showed a clear trophic niche expansion. Trophic niche metrics therefore provide a promising way of investigating non-lethal effects of exposure to organic chemicals on aquatic invertebrates, and subsequent disturbances in food webs.

Secondary production of freshwater zooplankton communities exposed to a fungicide and to a petroleum distillate in outdoor pond mesocosms.

Ecological risk assessment of chemicals in mesocosms requires measurement of a large number of parameters at the community level. Studies on invertebrate communities usually focus on taxonomic approaches, which only provide insights into taxonomic structure changes induced by chemicals. In the present study, abundance, biomass (B), theoretical production (P), and instantaneous P/B ratio were used as endpoints to assess the effects of the commercial form of the dithiocarbamate fungicide thiram (35 µg/L and 170 µg/L nominal concentrations) and of the hydrocarbon water accommodated fraction (HWAF) of a petroleum distillate (0.01 mg/L, 0.4 mg/L, 2 mg/L, and 20 mg/L loadings) on the zooplankton community in freshwater pond mesocosms. Endpoints were measured during a 4-wk treatment period (1 pulse/wk) followed by a 5-mo posttreatment period to evaluate zooplankton population recovery. The chlorophyll a concentration in water was significantly increased after treatment with HWAF, whereas it was not affected by thiram treatment. Zooplankton abundance-based analysis showed effects on a limited number of taxa, whereas other endpoints (mainly the P/B ratio) revealed that more taxa were impacted, with recovery depending on the chemical and concentration. Exposure to HWAF mainly had a negative impact on cladocerans, which resulted in top-down effects (between cladocerans and phytoplankton). Thiram negatively affected rotifers and copepods, suggesting more direct toxic effects. The results show that the use of secondary production as an endpoint provides a more comprehensive assessment of potential direct and indirect effects of chemicals on a community, and they also support evidence of alteration in functional processes.

Population genetics of Lymnaea stagnalis experimentally exposed to cocktails of pesticides.

Freshwater invertebrates may be regularly exposed to pesticides in agricultural landscapes, as water bodies such as ditches and ponds are the final recipient of many chemicals, through various transfer pathways. Local evolutionary impacts may hence be expected on populations, especially for species with a completely aquatic life cycle. We tested the hypothesis that exposure to combinations of pesticides used in crop protection programmes could increase the effect of random genetic drift in a non-target species, via demographic impacts. To do so, experimental populations of the freshwater snail Lymnaea stagnalis were created from a common genetic pool and exposed for three successive generations to treatments corresponding to two different crop protection plans (conventional and low pesticide input). Population genetic parameters were estimated in each generation on the basis of ten polymorphic microsatellite loci. Effects consistent with increased random genetic drift were observed for one sampling campaign performed in the third generation, i.e., decreased genetic variability and increased population differentiation in the group of populations exposed to the treatment programme whose demographic impact was the most effective on L. stagnalis. Otherwise, no clear pattern emerged and even opposed effects could be observed. All populations were found significantly inbred, mostly due to biparental inbreeding. Conversely, selfing was generally not significant, and did not express preferentially under high pesticide pressure. We conclude from this study that population genetics should be used very cautiously in the context of ecological risk assessment, especially when applied to natural populations.

An integrated environmental approach to investigate biomarker fluctuations in the blue mussel Mytilus edulis L. in the Vilaine estuary, France.

Estuarine areas represent complex and highly changing environments at the interface between freshwater and marine aquatic ecosystems. Therefore, the aquatic organisms living in estuaries have to face highly variable environmental conditions. The aim of this work was to study the influence of environmental changes from either natural or anthropogenic origins on the physiological responses of Mytilus edulis. Mussels were collected in the Vilaine estuary during early summer because this season represents a critical period of active reproduction in mussels and of increased anthropogenic inputs from agricultural and boating activities into the estuary. The physiological status of the mussel M. edulis was evaluated through measurements of a suite of biomarkers related to: oxidative stress (catalase, malondialdehyde), detoxication (benzopyrene hydroxylase, carboxylesterase), neurotoxicity (acetylcholinesterase), reproductive cycle (vitelline, condition index, maturation stages), immunotoxicity (hemocyte concentration, granulocyte percentage, phagocytosis, reactive oxygen species production, oxidative burst), and general physiological stress (lysosomal stability). A selection of relevant organic contaminant (pesticides, (polycyclic aromatic hydrocarbons, polychlorobiphenyls) was measured as well as environmental parameters (water temperature, salinity, total suspended solids, turbidity, chlorophyll a, pheopigments) and mussel phycotoxin contamination. Two locations differently exposed to the plume of the Vilaine River were compared. Both temporal and inter-site variations of these biomarkers were studied. Our results show that reproduction cycle and environmental parameters such as temperature, organic ontaminants, and algal blooms could strongly influence the biomarker responses. These observations highlight the necessity to conduct integrated environmental approaches in order to better understand the causes of biomarker variations.

Structural and functional effects of conventional and low pesticide input crop-protection programs on benthic macroinvertebrate communities in outdoor pond mesocosms.

The impacts of current and alternative wheat crop protection programs were compared in outdoor pond mesocosms in a 10-month long study. Realistic exposure scenarios were built based upon the results of modelling of drift, drainage and runoff of pesticides successively applied under two environmental situations characteristics of drained soils of northern France. Each situation was associated to two crop protection programs ("Conventional" and "Low-input") differing in the nature of pesticides used, number of treatments and application rate. Both programs induced significant direct negative effects on various invertebrate groups. Bifenthrin and cyprodynil were identified as the main responsible for these effects in conventional and low-input program, respectively. Indirect effects were also demonstrated especially following treatments with cyprodynil. Litter breakdown was significantly reduced in all treated mesocosms as the functional consequence of the decrease in the abundance of shredders (asellids, Gammarus pulex) illustrating the link between structural and functional effects of pesticides on macroinvertebrate communities. Recovery was observed for many taxa before the end of the study but not for the most sensitive non mobile taxa such as G. pulex. No influence of the agropedoclimatic situation on the effects was shown, suggesting than the main impacts were associated to inputs from drift. The results confirm that the proposed low-input program was less hazardous than the conventional program but the observed structural and functional impact of the low-input program suggest that further improvement of alternative crop protection programs is still needed.

Effects of repeated field applications of two formulations of Bacillus thuringiensis var. israelensis on non-target saltmarsh invertebrates in Atlantic coastal wetlands.

Bacillus thuringiensis var. israelensis (Bti) is commonly used for selective control of larval populations of mosquitoes in coastal wetlands. A two year-study was implemented to investigate whether repeated treatments with Bti applied either as a liquid (VectoBac® 12AS) or a water-dispersible granule (VectoBac® WG) formulation may affect the abundance and diversity of non-target aquatic invertebrates in saltmarsh pools. Taxonomic composition of the invertebrate communities was typical of brackishwater intermittent ecosystems, with a dominance of annelids, crustaceans and nematocerans. Conditions were contrasted between the two years of the survey, both in terms of annual cumulative rainfall and rainfall distribution throughout the year. As a consequence, the hydroperiod and some other environmental characteristics associated with pool drying played a major role in the dynamics of the invertebrate community. In summer 2006, pool drying reduced the abundance of the polychaete worm Nereis diversicolor, of the amphipod crustacean Corophium volutator and of chironomid larvae. These taxa were able to recolonize rapidly the pools after flooding in September 2006. In 2007, rainfall was more regularly distributed across the year, and the pools did not get dry. Hydrozoans, Chironomini and Orthocladiinae larvae, and oligochaetes were more abundant in treated than in control pools, especially in VectoBac® WG-treated pools. No adverse effects of the treatments were shown on the abundance of N. diversicolor, C. volutator and midge larvae, suggesting that the availability of these food sources for birds was not negatively affected by Bti applications. It is concluded that, as currently performed in Western France coastal wetlands, land-based treatments of saltmarsh pools for larval mosquito control with Bti, used either as VectoBac® 12AS or VectoBac® WG, did not adversely impact non-target aquatic invertebrate communities.

Chitobiase activity as an indicator of altered survival, growth and reproduction in Daphnia pulex and Daphnia magna (Crustacea: Cladocera) exposed to spinosad and diflubenzuron.

Chitobiase is involved in exoskeleton degradation and recycling during the moulting process in arthropods. In aquatic species, the moulting fluid is released into the aqueous environment, and chitobiase activity present therein can be used to follow the dynamics of arthropod populations. Here, chitobiase activity was used for monitoring the impact of mosquito candidate larvicides on Daphnia pulex and Daphnia magna under laboratory conditions. Both species were exposed to spinosad (2, 4, 8 µg L(-1)) and diflubenzuron (0.2, 0.4, 0.8 µg L(-1)) for 14 days. Bacillus thuringiensis var. israelensis (Bti; 0.25, 0.5, 1 µL L(-1)) was used as the reference larvicide. Chitobiase activity, adult survival, individual growth and fecundity, expressed as the number of neonates produced, were measured every 2 days. Average Exposure Concentrations of spinosad were ten-fold lower than the nominal concentrations, whereas only a slight deviation was observed for diflubenzuron. In contrast to Bti, spinosad and diflubenzuron significantly affected both species in terms of adult survival, and production of neonates. As compared to D. pulex, D. magna was more severely affected by diflubenzuron, at low and medium concentrations, with reduced adult growth and much lower chitobiase activity. Chitobiase activity was positively correlated with the individual body length, number of neonates produced between two consecutive observation dates, and number of females and neonates. In addition, the significant positive correlations between chitobiase activity measured on the last sampling date before the first emission of neonates and the cumulative number of neonates produced during the whole observation period strongly support the potential of the activity of this chitinolytic enzyme as a proxy for assessing the dynamics of arthropod populations exposed to larvicides used for mosquito control.

Parental exposure to pesticides and progeny reaction norm to a biotic stress gradient in the freshwater snail Lymnaea stagnalis.

Human-induced environmental stress may lead to rapid evolutionary processes, and can affect the ability of natural populations to respond to other environmental change or stress. We used quantitative genetics tools, pesticide exposure and a gradient of biotic stress to investigate these questions in the freshwater snail Lymnaea stagnalis. The study focused on the genetic component of variance for life-history traits within populations, and the ability of different lines to respond differently to stress. The effect of parental exposure to a xenobiotic stress on the reaction norm of the progeny to another stress was also estimated (parental non-genetic effect). First, under laboratory conditions, inter-family variance suggested significant heritability for most traits. Second, under outdoor exposure to various pesticides, variation among families was significant for individual growth. Clutch size and hatching rate of the clutches laid in the laboratory after exposure showed similar results, and moreover, family interacted significantly with pesticides. Third, under a gradient of biotic stress (food and competition), inter-family variation was again significant for growth, and a significant interaction with biotic stress was observed for juvenile growth and ultimate size. Family heterogeneity and family × environment interactions indicate the possibility of differential evolutionary responses among lines, through different reaction norms. Stressful conditions did not affect the estimated heritability, and for pesticides, no transgenerational effect was detected on progeny growth in response to the biotic stress. Focused on short-term evolutionary responses, the present study illustrates a possible way of incorporating evolutionary approaches into ecotoxicological risk assessment procedures, for example, by accounting for inter-family variation.

Effects of diquat and fomesafen applied alone and in combination with a nonylphenol polyethoxylate adjuvant on Lemna minor in aquatic indoor microcosms.

The influence of tank-mix adjuvants on pesticide toxicity remains largely unknown. Agral 90, a nonylphenol polyethoxylated tank-mix adjuvant, has been used with diquat (bipyridylium herbicide) and fomesafen (diphenyl-ether herbicide) in aquatic indoor microcosms in order to compare the toxicity of the single compounds and of binary herbicide-adjuvant mixtures to Lemna minor. Twenty-four microcosms were used and treatments were performed with substances alone or with herbicide-adjuvant binary mixtures, at two concentrations levels (44.4 and 222.2 microg/L for the herbicides, and 100 and 500 microg/L for Agral 90). Toxicity was assessed weekly for 1 month through growth measurements, as inferred from the relative frond number (RFN) and relative frond area (RFA). Concentrations of diquat and fomesafen in water and sediments were measured weekly. The herbicides showed very different behaviour in microcosms, with a rapid disappearance of diquat from the aqueous phase whereas fomesafen levels remained almost constant over time. Diquat strongly inhibited the growth of L. minor whereas fomesafen had no effect on plant growth. Presence of the adjuvant only slightly reduced the effect of the lowest concentration of diquat, probably as a result of dispersion of the herbicide at the water surface. It is concluded that tank-mix adjuvant designed to improve herbicide efficiency in the terrestrial environment did not have any effect on aquatic plants when applied to the aquatic environment.

Calibration, validation and sensitivity analysis of an ecosystem model applied to artificial streams.

There is a growing interest for the use of ecological models to improve the Ecological Risk Assessment (ERA) of toxic pollutants. However, although several models have been proposed, there is little information available on their relevance (i.e., validation through comparison with original data) and on their sensitivity to the input parameters. In this study, the Aquatox Model was used to simulate biomass dynamics of various biological compartments in artificial streams designed for measuring the effects of pollutants on aquatic communities. Calibration and validation of the model were performed using data from control streams. Multi-variate sensitivity analysis was implemented to identify those parameters that exert a prominent role in the outputs of the model. The calibrated model was able to adequately describe the dynamics of most of the simulated biological compartments of a stream. Using data from other streams, it was shown that between-streams natural variability was a source of discrepancy between observed and simulated data. Sensitivity analysis showed that the model was highly sensitive to the parameters related to the temperature limitation, maximum rate of photosynthesis of producers and consumption by consumers. This strongly suggests that particular attention should be devoted to the estimation of these parameters if this model has to be used for ERA of toxicants in aquatic ecosystems.

Influence of isolation on the recovery of pond mesocosms from the application of an insecticide. I. Study design and planktonic community responses.

The influence of relative isolation on the ecological recovery of freshwater outdoor mesocosm communities after an acute toxic stress was assessed in a 14-month-long study. A single concentration of deltamethrin was applied to 8 out of 16 outdoor 9-m3 mesocosms to create a rapid decrease of the abundance of arthropods. To discriminate between external and internal recovery mechanisms, four treated and four untreated (control) mesocosms were covered with 1-mm mesh screen lids. The dynamics of planktonic communities were monitored in the four types of ponds. The abundance of many phytoplankton taxa increased after deltamethrin addition, but the magnitude of most increases was relatively small, probably due to low nutrient availability and the survival of rotifers. The greatest impact on zooplankton was seen in Daphniidae and, to a lesser extent, calanoid copepods. Recovery (defined as when statistical analysis failed to detect a difference in the abundance between the deltamethrin-treated ponds and corresponding control ponds for two consecutive sampling dates) of Daphniidae was observed in the water column 105 and 77 d after deltamethrin addition in open and covered mesocosms, respectively, and <42 d for both open and covered ponds at the surface of the sediments. Rotifers did not proliferate, probably because of the survival of predators (e.g., cyclopoid copepods). These results confirm that the recovery of planktonic communities after exposure to a strong temporary chemical stress mostly depends upon internal mechanisms (except for larvae of the insect Chaoborus sp.) and that recovery dynamics are controlled by biotic factors, such as the presence of dormant forms and selective survival of predators.

Influence of isolation on the recovery of pond mesocosms from the application of an insecticide. II. Benthic macroinvertebrate responses.

The immediate response and recovery of the macrobenthic communities of nonisolated and isolated freshwater outdoor 9 ml mesocosms following an acute stress caused by the addition of deltamethrin were studied over a 14-month period. To discriminate between internal and external recovery mechanisms, half of the treated ponds were covered by 1-mm mesh lids that restricted aerial recolonization. Both structural (abundance of the different taxonomic groups) and functional (litter breakdown) parameters were monitored. Insects were broadly reduced in numbers by deltamethrin addition. In general, noninsect groups were not affected or increased in abundance in deltamethrin-treated ponds, probably because of relative insensitivity to deltamethrin, reduced predation, and lower competition for food. No major change in litter breakdown rates were seen, probably because of functional redundancy among the macrobenthic community. Chironominae larvae recovered in open, treated mesocosms 62 d after deltamethrin addition and most insect groups recovered 84 d after the treatment date. However, the presence of lids significantly reduced insect recovery rate, suggesting that it largely depends on the immigration of winged forms (i.e., external recovery) from surrounding non- or less affected systems. These results indicate that the recovery time of macrobenthic communities in an affected natural pond would depend on spatial characteristics of the landscape and also the season that exposure occurs. Isolated ecosystems would display posttreatment insect recovery dynamics very different from highly connected ones, evolving toward alternate pseudoequilibrium states, possibly with lower biodiversity but with preserved functionality. Consequences for higher tier risk assessment of pesticides are discussed.

Effects of pesticides on community structure and ecosystem functions in agricultural streams of three biogeographical regions in Europe.

There is a paucity of large-scale field investigations on the effects of organic toxicants on stream macroinvertebrate community structure and ecosystem functions. We investigated a total of 29 streams in two study areas of France and Finland for pesticide exposure, invertebrates and leaf-litter breakdown. To link pesticide exposure and community composition we applied the trait-based Species At Risk (SPEAR) indicator system. In the French region, pesticide stress was associated with a decrease in the relative abundance and number of sensitive species in the communities. The presence of undisturbed upstream reaches partly compensated the effects of pesticide contamination. Functional effects of pesticides were identified by a 2.5-fold reduction of the leaf-litter breakdown rate that was closely correlated with the structural changes in the contaminated streams. No effects of pesticides were observed in Finnish streams since contamination with pesticides was very low. In a follow-up analysis, the SPEAR approach successfully discriminated between reference and contaminated sites across different biogeographical regions, also including results of a previous field study in North Germany. Furthermore, change of the community structure was detectable at a concentration range as low as 1/100 to 1/1000 the acute 48 h-LC50 of Daphnia magna. Our findings demonstrate that pesticides may influence the structure and function of lotic ecosystems and that the SPEAR approach can be used as a powerful tool in biomonitoring over large spatial scales.