New Publications

Toxicity – biodiversity relationships unravelled

ecol lettersThe production and use of chemicals is regulated by environmental legislation so as to protect the diversity of our surface waters. Until recently, however, it was impossible to predict the relationship between chemical toxicity and the diversity of aquatic communities, which hampered effective environmental conservation. Together with an international consortium, the laboratory of environmental toxicology (, UGent) developed the first theory to predict biodiversity along gradients of toxic stress. Combining this theory to data from polluted algal communities, the scientists reveal that the variability of toxicity tolerance in these communities is five to ten times higher between individuals from the same species than between individuals from different species. The results of this research also demonstrate that this 'within-species variability' is a buffer against species loss in ecosystems polluted with chemicals. These findings, which have been published in the nr 1-ranked ecology journal 'Ecology Letters', raise important concerns regarding the use of species-based tolerance data for environmental protection and explain ecosystem resistance during chemical spills.

Migration and opportunistic feeding increase PCB accumulation in arctic seabirds

ESTPolychlorinated biphenyls (POPs) are resistant towards common degradation pathways and accumulate, because of their lipophilicity, in organisms' fatty tissues. In addition, the transfer of POPs in a foodweb typically results in elevated POP concentrations at the highest trophic levels (i.e. biomagnification). Previous modeling efforts hence focused on the importance of an organism's trophic level and the lipophilicity of the chemical as predictors for the organism's POP body concentration. However, field studies have not only demonstrated that Arctic seabirds, as top predators, have elevated POP body concentrations compared to their environment, but also that POP body concentrations can differ substantially between species that occupy similar trophic levels.

An investigation of the inter-clonal variation of the interactive effects of cadmium and Microcystis aeruginosa on the reproductive performance of Daphnia magna

aquatic toxicologyStressors seldomly occur isolated in the environment. In a mixture, stressors can interact with each other. That might have profound adverse effects on the animals that live in the environment. Indeed, in mixture toxicity, one plus one does not always equals two. Imagine for instance the effect of throwing a mentos candy in coke (Youtube: MythBusters - Diet Coke and mentos). The effect of both combined is much larger than what you would expect. Such (synergistic) interactions between the metal cadmium and the cyanobacterium Microcystis are what De Coninck et al. (2013) studied in their most recent paper. Cyanobacteria are toxic blue-green algae that tend to increase in occurence due to climate change (for instance, Global Water Forum).

Transcription patterns of genes encoding four metallothionein homologs in Daphnia pulex exposed to copper and cadmium are time- and homolog-dependent

aquatic toxicologyIn a recent publication, Asselman et al. (2013) studied the role of metallothioneins, or metal binding proteins, in metal detoxification upon exposure to copper and cadmium. In their study, Asselman et al. (2013) used the freshwater crustacean Daphnia as a model organism but their results will help to elucidate the function of this important protein in other (higher) organisms as well. Indeed, metal pollution has significant impacts on fish (Scientific American).

Development and validation of a quantitative structure–activity relationship for chronic narcosis to fish

etcQuantitative structure–activity relationship models (QSAR models) typically relate a set of predictor variables to the response variable. These models are useful tools in predictive ecotoxicology as the can be used to predict the (adverse) biological activity of a chemical (the response variable) based on the physico-chemical properties of the chemical (the predictor variables). As animal testing, and especially vertebrate testing, are generally strongly discouraged, the use of QSAR models offers an alternative. However, in ecotoxicology, QSAR models that describe the relationship between the physico-chemical properties of chemicals and their chronic toxicity to vertebrates are scarce. This lagoon in our knowledge is filled by the research described in our latest paper.

Microplastic pollution in deep-sea sediments

env pollutWe have all heard the phrase: "We know more about the surface of the moon than the deep sea". Unfortunately, this is not exaggeration: the deep sea is the largest ecosystem on Earth, but also one of the least studied despite it harbouring a high biodiversity and a wealth of resources. Sadly, the deep seafloor is still, for most people, out of sight and therefore out of mind. This has encouraged the dumping of waste of all sorts into deep waters. For centuries, this was organic, degradable matter. Now, our solid wastes often contain synthetic elements, plastics in particular. In recent years, more and more reports have been published that demonstrate the large presence of plastic litter in the deep sea: the seafloor of the Mediterranean, Atlantic canyons and even Arctic waters are covered with plastic litter. Recently, our lab added another pollutant to the list: for the first time ever, microplastics were recorded in deep-sea sediments originating from several location worldwide. These results show that microplastics have penetrated the marine environment to a larger extent than previously assumed.

Epigenetics in an ecotoxiological context

mutation researchChildren of obese fathers are more likely to have chronic diseases in their later life. That was the conclusion of a remarkable study by Dr. Adelheid Soubry in BMC Medicine (De Standaard, 08/02/2013). She identified one of the mechanisms responsible to be DNA-methylation. DNA-methylation, among other mechanisms, are so-called epigenetic mechanisms. They can alter the DNA without actually altering the DNA code itself. These epigenetic mechanisms are also shown to be important in an ecotoxicological context. This was recently summarized by our post-doc Michiel Vandegehuchte in a review in Mutation Research/Genetic Toxicology and Environmental Mutagenesis.

Combined exposure to cyanobacteria and carbaryl results in antagonistic effects on the reproduction of Daphnia pulex
etcIn aquatic ecosystems, Daphnia are exposed to a wide variety of natural and chemical stressors that can cause interactive effects resulting in an increased impact on aquatic ecosystems. The authors therefore investigated the interactive effects of harmful cyanobacteria (cyanoHABs) with carbaryl in Daphnia pulex, because cyanobacteria have become an important concern for aquatic ecosystems. Daphnia were exposed for 21 d to 4 selected cyanobacteria (Aphanizomenon sp., Cylindrospermopsis raciborskii, Microcystis aeruginosa, and Oscillatoria sp), carbaryl, and all binary combinations of carbaryl and each individual cyanobacterium. Results were analyzed with both the independent action and the concentration addition model.

Assessment of marine debris on the Belgian Continental Shelf

marinepollutionbulletinA two-year comprehensive assessment of marine litter in Belgian coastal waters was performed. Abundance, weight and composition of marine debris, including microplastics, was assessed by performing beach, sea surface and seafloor monitoring campaigns. Plastic items were the dominant type of macrodebris recorded: over 95% of debris present in the three sampled marine compartments were plastic. In general, concentrations of macrodebris were quite high. Especially the number of beached debris reached very high levels: on average 6,429 ± 6,767 items per 100m were recorded. Microplastic concentrations were determined to assess overall abundance in the different marine compartments of the Belgian Continental Shelf. In terms of weight, macrodebris still dominates the pollution of beaches, but in the water column and in the seafloor microplastics appear to be of higher importance: microplastic weight is approximately 100 times and 400 times higher, respectively, than macrodebris weight.


Ecotoxicity and uptake of polymer coated gold nanoparticles

nanotoxicologyBioconjugated gold nanoparticles (Au NPs) are a promising tool for pharmaceutical applications. However, the ecotoxicity of these types of NPs has hardly been studied. We investigated the ecotoxicity and uptake of 4-5 nm Au NPs to which two types of polymer coatings were attached. One coating was an amphiphilic polymer only and the other an amphiphilic coating to which 10 kDa polyethylene glycol chains were attached. In both 72 h algal growth inhibition tests with the alga Pseudokirchneriella subcapitata and in 24 h resazurin cytotoxicity tests with the rainbow trout gill cell line RTGill-W1, the pegylated Au NPs were found less toxic compared to the amphiphilic coated particles. No uptake or direct interaction between particles and algal cells was observed. However, uptake/adsorption in fish gill cells reached up to >10(6) particles/cell after 1 h and particles were eliminated for ≥96% after 24 h depuration. Both particle types were found within membrane enclosed vesicles in the cytoplasm of RTgill-W1 cells.