New Publications

In a recent research paper published in Chemosphere, Gert Everaert and co-workers quantified the relative contribution of persistent organic pollutants to marine phytoplankton biomass dynamics. To do so, they used concentrations of persistent organic pollutants (POPs) to infer potential POP-induced effects on marine primary production in the Kattegat and the North Sea. They modelled phytoplankton dynamics using four classical drivers (light and nutrient availability, temperature and zooplankton grazing) and tested whether extending this model with a POP-induced phytoplankton growth limitation term improved predictions of the observed chlorophyll a concentrations.

In the European Union and the United States, two differently structured bioavailability models are used in risk assessments of copper. These models, the biotic ligand models (BLM), are valuable tools based on the concept that toxicity depends on the concentration of metal bound to a biological binding site; the biotic ligand. The application of these different BLMs implies that a discrepancy exists between regulation of aquatic toxicity in the U.S. and the E.U. In this study we evaluated the capacity of these BLMs to predict chronic copper toxicity to two water flea clones (Daphnia magna). We found that one BLM performed best with one clone, while the other BLM performed best with the other clone.

Over the last decade, scientific technologies have improved significantly. While it took more than ten years and about 3 billion dollars to sequence the first human genome, prices for genome sequencing are currently plummeting. Now, you can even send your own DNA sample to commercial compagnies for about 100 dollars and learn about your genetic ancestry. Yet, despite this massive amount of data generated, we still cannot understand what the majority of that DNA is doing. Which genes are causing diseases? Which genes are responding to toxicants?

Species interactions are often overlooked when assessing the ecological impact of chemicals. However, they can greatly influence the way a population is affected by a chemical, either increasing or decreasing a chemical’s effects. In this publication, we examined three types of species interactions – intraspecific competition, interspecific competition and predation – in Daphnia magna populations exposed to pyrene. Predation and high initial intraspecific competition were shown to interact antagonistically with pyrene exposure i.e. the effect of pyrene was less pronounced. This was attributed to differences in population structure prior to pyrene exposure and pyrene-induced reductions in predation pressure. This study is a good example of how species interactions can alter the response of a population to chemical exposure in a way that cannot be predicted from single species tests alone.

We investigated the effects of a binary Ni-Zn mixture on chronic reproductive toxicity to the water flea Daphnia magna. The results suggested that the type of interactive effect is dependent on the effect size at which Ni and Zn are combined in the mixture. Weak antagonistic or non-interactive effects occurred in the mixture treatments where each of the individual metals produced insignificant or only weak adverse effects on their own. Conversely, synergistic mixture effects, i.e., stronger effects than expected, only occurred when at least one of both metals in the mixture caused a greater than 20% effect on reproduction. Since low effect sizes are the most relevant ones in most regulatory frameworks, our data suggest that the CA and IA mixture toxicity models can both serve as conservative models for predicting effects of Ni-Zn mixtures.

etc cover thumb100 Recently a harmful algae bloom made Lake Erie's water temporarily undrinkable in Toledo and surrounding towns in northwest Ohio. Over the last 50 years harmful algal blooms have been a regular occurrence in Lake Erie, with peak concentrations in late summer months. Such harmful algal blooms are commonly produced by cyanobacteria and not only impact water quality but they also have the potential to produce toxins that can harm humans, pets and wildlife. The blooms are caused by a combination of factors that promote high densities and reproduction of algae, one major factor being warmer temperatures. Therefore climate change has been linked to the global expansion of cyanobacteria through changes in temperature.

chemosphere thumb100 Due to their extensive use, continuous discharge and inefficient removal by wasterwater treatment plants, increasing levels of antibiotics are commonly detected in surface waters. Even though environmental levels are generally low, it has been shown that long-term exposure may adversely affect aquatic organisms. As such, there is an urgent need to improve classical water treatment techniques.

plantsoilThe biotic ligand model (BLM) is a bioavailability model for metals based on the concept that toxicity depends on the concentration of metal bound to a biological binding site; the biotic ligand. Here, we evaluated the BLM to interpret and explain mixture toxicity of metals (Cu and Zn). The mixture toxicity of Cu and Zn to barley (Hordeum vulgare L.) was tested with a 4 days root elongation test in resin buffered nutrient solutions.

Toxicity of lead (Pb) to freshwater green algae: Development and validation of a bioavailability model and inter-species sensitivity

aquatic toxicology thumb100 Scientifically sound risk assessment and derivation of environmental quality standards for lead (Pb) in the freshwater environment are hampered by insufficient data on chronic toxicity and bioavailability to unicellular green algae. Here, we first performed comparative chronic (72-h) toxicity tests with three algal species in medium at pH 6, containing 4 mg fulvic acid (FA)/L and containing organic phosphorous (P), i.e. glycerol-2-phosphate, instead of PO43− to prevent lead-phosphate mineral precipitation. Pseudokirchneriella subcapitata was 4-fold more sensitive to Pb than Chlorella kesslerii, with Chlamydomonas reinhardtii in the middle. The influence of medium physico-chemistry was therefore investigated in detail with P. subcapitata. In synthetic test media, higher concentrations of fulvic acid or lower pH protected against toxicity of (filtered) Pb to P. subcapitata, while effects of increased Ca or Mg on Pb toxicity were less clear. When toxicity was expressed on a free Pb2+ ion activity basis, a log-linear, 260-fold increase of toxicity was observed between pH 6.0 and 7.6. Effects of fulvic acid were calculated to be much more limited (1.9-fold) and were probably even non-existent (depending on the affinity constant for Pb binding to fulvic acid that was used for calculating speciation).

Microplastics in bivalves cultured for human consumption

env pollutToday, 27 years after Cpt. Charles J. Moore first discovered the Great Pacific Garbage Patch, marine plastic pollution continues to be a growing threat to the marine environment. As plastic debris is ubiquitious across the world's seas and oceans, the consequences of macroplastics for most (vertebrate) wildlife have been identified over the years. Yet, to date, the impacts of microplastics are less understood. These plastic particles (< 1mm), which are found in cosmetics and can be formed through the degradation of larger plastic items, are becoming increasingly abundant. As our research has shown, they can now be found from the surface layer all the way down to the deep-sea sediment. Worringly, microplastics can be ingested by a wide range of marine organisms because of their small dimensions which in turn creates an understudied risk of exposure for human consumers. Here we present the first study to report on the possible consequences of marine microplastics for human consumers by analysing the occurence of microplastics in commercially available shellfish. From our results, we calculated that the average European shellfish consumer has an uptake of 6400 microplastics per year. As there is a lack of (mammal) effect studies, this exposure poses an unknown risk for human health.

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