The Water Framework Directive (WFD), 2000/60/EC, requires an integrated approach to the monitoring and assessment of the quality of surface water bodies. The chemical status assessment is based on compliance with legally binding Environmental Quality Standards (EQSs) for selected chemical pollutants (priority substances) of EU-wide concern. In the context of the mandate for the period 2010 to 2012 of the subgroup Chemical Monitoring and Emerging Pollutants (CMEP) under the Common Implementation Strategy (CIS) for the WFD, a specific task was established for the elaboration of a technical report on aquatic effect-based monitoring tools. The activity was chaired by Sweden and co-chaired by Italy and progressively involved several Member States and stakeholders in an EU-wide drafting group. The main aim of this technical report was to identify potential effect-based tools (e.g. biomarkers and bioassays) that could be used in the context of the different monitoring programmes (surveillance, operational and investigative) linking chemical and ecological status assessment. The present paper summarizes the major technical contents and findings of the report.
Paper in pressVandendriessche S., Messiaen M., O'Flynn S., Vincx M., Degraer S.Hiding and feeding in floating seaweed: floating seaweed clumps as possible refuges or feeding grounds for fishes ABSTRACTFloating seaweed is considered to be an important habitat for juvenile fishes due to the provision of food, shelter, a visual orientation point and passive transport. The importance of the presence of the highly dynamical seaweed clumps from the North Sea to juvenile neustonic fishes was investigated by analysing both neuston samples (without seaweed) and seaweed samples concerning fish community structure, and length-frequency distributions and feeding habits of five associated fish species. While the neustonic fish community was mainly seasonally structured, the seaweedassociated fish community was more complex: the response of the associated fish species to environmental variables was species specific and probably influenced by species interactions, resulting in a large multivariate distance between the samples dominated by Chelon labrosus and the samples dominated by Cyclopterus lumpus, Trachurus trachurus and Ciliata mustela. The results of the stomach analysis confirmed that C. lumpus is a weedpatch specialist that has a close spatial affinity with the seaweed and feeds intensively on the seaweed-associated invertebrate fauna. Similarly, C. mustela juveniles also fed on the seaweed fauna, but in a more opportunistic way. The shape of the size-frequency distribution suggested enhanced growth when associated with floating seaweed.Chelon labrosus and T. trachurus juveniles were generally large in seaweed samples, but large individuals were also encountered in the neuston. The proportion of associated invertebrate fauna in their diet was of minor importance, compared to the proportions in C. lumpus. Individuals of Syngnathus rostellatus mainly fed on planktonic invertebrates but had a discontinuous size-frequency distribution, suggesting that some of the syngnathids were carried with the seaweed upon detachment and stayed associated. Floating seaweeds can therefore be regarded as ephemeral habitats shared between several fish species (mainly juveniles) that use them for different reasons and with varying intensity.
The initial tolerance to sub-lethal Cd exposure is the same among ten naïve pond populations of 1 Daphnia magna, but their micro-evolutionary potential to develop resistance is very different 2 3This is a post-print of a paper published in Aquatic Toxicology (Elsevier, Amsterdam, The 4 Netherlands). The contents are identical to those in the published version. Daphnia magna as well as their evolutionary potential to develop increased resistance. We did so by 31 measuring reproductive performance of 120 clones, i.e. 12 clones hatched from the recent dormant egg 32 bank of each of 10 populations, both in absence (Cd-free control) and presence of 4.4 µg Cd/L. We 33show that the initial tolerance, defined as the reproductive performance of individuals of the first 34 generation exposed to Cd relative to that in a Cd-free control was not significantly different among the 35 10 studied pond populations and averaged 0.82 ± 0.04 over these populations. Moreover, these 36 populations' initial tolerances were also not significantly different from the mean initial tolerance of 37 0.87 ± 0.08 at 4.0 µg Cd/L measured for a group of 7 often-used laboratory clones, collected from a 38 range of European ecotoxicity testing laboratories. This indicates that the initial response of naïve 39 natural pond populations to sub-lethal Cd can be relatively accurately predicted from ecotoxicity test 40 data from only a handful of laboratory clones. We then used estimates of broad-sense heritability of 41 Cd tolerance (H 2 ) -based on the same dataset -as a proxy of these populations' capacities to 42 evolutionarily respond to Cd in terms of the development of increased resistance, which is here 43 defined as the increase with time of the frequency of clones with a higher Cd tolerance in the 44 population (accompanied with an increase of mean Cd-tolerance of the population above the initial 45 tolerance). We show that the populations' estimated H 2 values of Cd-tolerance cover almost the entire 46 theoretically possible range, ranging from not significantly different from zero (for five populations) to 47 between 0.48 and 0.81 (for the five other populations). This indicates that, unlike the initial tolerance 48 to Cd, the (long-term) micro-evolutionary response to Cd may be very different among natural pond 49 populations. Therefore, we conclude that it may be very difficult to predict the long-term response of 50 an unstudied population to chemical stress from tolerance data on a sample of other populations. It is 51 therefore suggested that new methods for forecasting long-term responses should be explored, such as 52 4 the development of predictive models based on the combination of population-genomic and tolerance 53 time-series data. 54 55
The existence of genetic variability is a key element of the adaptive potential of a natural population to stress. In this study we estimated the additive and non-additive components of the genetic variability of net reproductive rate (R(0)) in a natural Daphnia magna population exposed to Cd stress at two different temperatures. To this end, life-table experiments were conducted with 20 parental and 39 offspring clonal lineages following a 2 × 2 design with Cd concentration (control vs. 3.7 μg Cd/L) and temperature (20 vs. 24 °C) as factors. Offspring lineages were obtained through inter-clonal crossing of the different parental lineages. The population mean, additive and non-additive genetic components of variation in each treatment were estimated by fitting an Animal Model to the observed R(0) values using restricted maximum likelihood estimation. From those estimates broad-sense heritabilities (H(2)), narrow-sense heritabilities (h(2)), total (CV(G)) and additive genetic coefficients of variation (CV(A)) of R(0) were calculated. The exposure to Cd imposed a considerable level of stress to the population, as shown by the fact that the population mean of R(0) exposed to Cd was significantly lower than in the control at the corresponding temperature, i.e. by 23 % at 20 °C and by 88 % at 24 °C. The latter difference indicates that increasing temperature increased the stress level imposed by Cd. The H² and CV(G) were significantly greater than 0 in all treatments, suggesting that there is a considerable degree of genetic determination of R(0) in this population and that clonal selection could rapidly lead to increasing population mean fitness under all investigated conditions. More specifically, the H² was 0.392 at 20 °C+Cd and 0.563 at 24 °C+Cd; the CV(G) was 30.0 % at 20 °C+Cd and was significantly higher (147.6 %) in the 24 °C+Cd treatment. Significant values of h(2) (= 0.23) and CV(A) (= 89.7 %) were only found in the 24 °C+Cd treatment, suggesting that the ability to produce more offspring under this stressful condition may be inherited across sexual generations. In contrast, in the less stressful 20 °C+Cd treatment the h(2) (0.06) and CV(A) (7.0 %) were very low and not significantly higher than zero. Collectively our data indicate that both the asexual and sexual reproduction phases in cyclic parthenogenetic D. magna populations may play a role in the long-term adaptive potential of Daphnia populations to chemical stress (with Cd as the current example) and that environmental variables which influence the stress level of that chemical may influence this adaptive potential (with temperature as current example).
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