Published on March 14, 2013

Using additive modelling to quantify the effect of chemicals on phytoplankton diversity and biomass

scitotenvEnvironmental authorities require the protection of biodiversity and other ecosystem properties such as biomass production. However, the endpoints listed in available ecotoxicological datasets generally do not contain these two ecosystem descriptors. Inferring the effects of chemicals on such descriptors from micro- or mesocosm experiments is often hampered by inherent differences in the initial biodiversity levels between experimental units or by delayed community responses. Here we introduce additive modelling to establish the effects of a chronic application of the herbicide linuron on 10 biodiversity indices and phytoplankton biomass in microcosms. We found that communities with a low (high) initial biodiversity subsequently became more (less) diverse, indicating an equilibrium biodiversity status in the communities considered here. Linuron adversely affected richness and evenness while dominance increased but no biodiversity indices were different from the control treatment at linuron concentrations below 2.4 μg/L. Richness-related indices changed at lower linuron concentrations (effects noticeable from 2.4 μg/L) than other biodiversity indices (effects noticeable from 14.4 μg/L) and, in contrast to the other indices, showed no signs of recovery following chronic exposure. Phytoplankton biomass was unaffected by linuron due to functional redundancy within the phytoplankton community. Comparing thresholds for biodiversity with conventional toxicity test results showed that standard ecological risk assessments also protect biodiversity in the case of linuron.

Published on February 14, 2013

Dr. ir. Frederik De Laender joined the Young Academy

jongeacademie Recently, the Royal Flemish Academy of Belgium decided to establish a Young Academy. Forty young researchers, amongst whom Frederik De Laender of our lab, have joined the Young Academy. They were selected from as many as 146 high-potential candidates who responded to the call for membership. These young researchers have three objectives: (international) interdisciplinary research, reflection about the current science policy, and science communication to the youth. Congratulations, Frederik!

Update: In total 13 researchers of Ghent University were selected. More information: (Dutch)

Published on February 13, 2013

Best oral presentation award on the 18th national symposium on applied biological sciences

awardA few days ago, the 18th National Symposium on Applied Biological Sciences took place in Ghent at which we were present with four oral presentations and four poster presentations. It was a successful symposium, not the least for our lab-member David Deruytter who won the award for best oral presentation in the Environmental Quality session with his talk entitled "The combined effect of DOC and salinity on the accumulation and toxicity of copper in mussel larvae". Congratulations, David!

Published on February 12, 2013

Interactive effects of a bacterial parasite and the insecticide carbaryl to life-history and physiology of two Daphnia magna clones differing in carbaryl sensitivity

aquatic toxicologyNatural and chemical stressors occur simultaneously in the aquatic environment. Their combined effects on biota are usually difficult to predict from their individual effects due to interactions between the different stressors. Several recent studies have suggested that synergistic effects of multiple stressors on organisms may be more common at high compared to low overall levels of stress. In this study, we used a three-way full factorial design to investigate whether interactive effects between a natural stressor, the bacterial parasite Pasteuria ramosa, and a chemical stressor, the insecticide carbaryl, were different between two genetically distinct clones of Daphnia magna that strongly differ in their sensitivity to carbaryl. Interactive effects on various life-history and physiological endpoints were assessed as significant deviations from the reference Independent Action (IA) model, which was implemented by testing the significance of the two-way carbaryl × parasite interaction term in two-way ANOVA's on log-transformed observational data for each clone separately. Interactive effects (and thus significant deviations from IA) were detected in both the carbaryl-sensitive clone (on survival, early reproduction and growth) and in the non-sensitive clone (on growth, electron transport activity and prophenoloxidase activity). No interactions were found for maturation rate, filtration rate, and energy reserve fractions (carbohydrate, protein, lipid). Furthermore, only antagonistic interactions were detected in the non-sensitive clone, while only synergistic interactions were observed in the carbaryl sensitive

Published on February 4, 2013

Master dissertation subjects available

Recently some new Master dissertation subjects have been added to the website, for students wanting to make their Bioscience Engineering Master dissertation in our research group. The following topics can now be chosen:

  • Pesticides in aquatic ecosystems – from patterns to predictionsBiodiversity vs. Chemodiversity – exploring a new ecotoxicological conceptBack to the future: paleo-ecotoxicology.
  • The role of algal toxins in host-microbial interactions in the development of a sustainable larviculture of mussels and brine shrimp
  • Microplastics in the marine environment
  • Samen sterker? Het effect van metaalmengsels op de garnaal
  • Metal toxicology in freshwater sediments: environmental and biological factors affecting the sensitivity of benthic invertebrates
  • Marine toxins in the Belgian coastal zone from microalgae
  • Microplastic vervuiling op stranden en rond koraalriffen in Kenia? Een blinde vlek
  • Is 1 + 1 steeds gelijk aan 2? Modelleren van interactiepatronen in toxische mengsels met behulp van biologische netwerken

Published on January 2, 2013

Combined and interactive effects of global climate change and toxicants on populations and communities

open access thumb medium100 100Increased temperature and other environmental effects of global climate change (GCC) have documented impacts on many species (e.g., polar bears, amphibians, coral reefs) as well as on ecosystem processes and species interactions (e.g., the timing of predator–prey interactions). A challenge for ecotoxicologists is to predict how joint effects of climatic stress and toxicants measured at the individual level (e.g., reduced survival and reproduction) will be manifested at the population level (e.g., population growth rate, extinction risk) and community level (e.g., species richness, food-web structure). The authors discuss how population- and community-level responses to toxicants under GCC are likely to be influenced by various ecological mechanisms. Stress due to GCC may reduce the potential for resistance to and recovery from toxicant exposure. Long-term toxicant exposure can result in acquired tolerance to this stressor at the population or community level, but an associated cost of tolerance may be the reduced potential for tolerance to subsequent climatic stress (or vice versa). Moreover, GCC can induce large-scale shifts in community composition, which may affect the vulnerability of communities to other stressors. Ecological modeling based on species traits (representing life-history traits, population vulnerability, sensitivity to toxicants, and sensitivity to climate change) can be a promising approach for predicting combined impacts of GCC and toxicants on populations and communities.

Full reference (

Published on November 20, 2012

Check out our project websites

  •  Aquastress

    The AquaStress project investigates multiple stress in aquatic systems across multiple levels of biological organization and to assess to what extent multiple stress effects occurring at higher levels of organization can be predicted/explained based on observations of effects occurring at lower levels.

  • Daphnia Genomics Consortium

Published on November 6, 2012

LMAE at SETAC Longbeachsetaclogo2

The research group Environmental Toxicology will be presenting some of its research at the SETAC North America 33rd Annual Meeting in Longbeach, California from 11-15 November 2012. Come and see us at these dates and places!

Published on October 26, 2012

The potential for adaptation in a natural Daphnia magna population: broad- and narrow-sense heritability of netreproductive rate under Cd stress at two temperatures

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 x 2 design with Cd concentration (control vs. 3.7 mu g Cd/L) and temperature (20 vs. 24 A degrees 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 (CVG) and additive genetic coefficients of variation (CVA) 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 A degrees C and by 88 % at 24 A degrees C. The latter difference indicates that increasing temperature increased the stress level imposed by Cd. The HA(2) and CVG 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 HA(2) was 0.392 at 20 A degrees C+Cd and 0.563 at 24 A degrees C+Cd; the CVG was 30.0 % at 20 A degrees C+Cd and was significantly higher (147.6 %) in

Published on August 27, 2012

Biodiversity of freshwater diatom communities during 1000 years of metal mining, land use, and climate change in Central Sweden

Frederik De Laender and colleagues subjected a unique set of high-quality paleoecological data to statistical modeling to examine if the biological richness and evenness of freshwater diatom communities in the Falun area, a historical copper (Cu) mining region in central Sweden, was negatively influenced by 1000 years of metal exposure. Contrary to ecotoxicological predictions, we found no negative relation between biodiversity and the sedimentary concentrations of eight metals. Strikingly, our analysis listed metals (Co, Fe, Cu, Zn, Cd, Pb) or the fractional land cover of cultivated crops, meadow, and herbs indicating land disturbance as potentially promoting biodiversity. However, correlation between metal- and land-cover trends prevented concluding which of these two covariate types positively affected biodiversity. Because historical aqueous metal concentrations—inferred from solid-water partitioning—approached experimental toxicity thresholds for freshwater algae, positive effects of metal mining on biodiversity are unlikely. Instead, the positive relationship between biodiversity and historical land-cover change can be explained by the increasing proportion of opportunistic species when anthropogenic disturbance intensifies. Our analysis illustrates that focusing on the direct toxic effects of metals alone may yield inaccurate environmental assessments on time scales relevant for biodiversity conservation.

Full reference (link)

De Laender F, Verschuren D, Bindler R, Thas O, Janssen CR. 2012. Biodiversity of Freshwater Diatom Communities during 1000 Years of Metal Mining, Land Use,