New Publications

Darwin’s rules of “evolution” and “survival of the fittest” also apply to populations of organisms exposed to chemical substances. Our review of the scientific literature revealed that long-term exposure to two classes of persistent pollutants, PAH’s and PCB’s, can affect the evolutionary trajectory of natural populations and make them more resistant to these chemicals. In some cases, this has happened at pollutant levels below currently applicable environmental quality standards. This calls for integrating evolutionary processes into regulatory decision-making.

Over the last decade, it has become clear that epigenetic mechanisms could play a role in the toxicity of environmental toxicants. Epigenetic mechanisms are mechanisms that alter the DNA strands without changing the DNA itself.In this study, we focus on the DNA methylation patterns in the waterflea exposed to a toxic blue green algae.  We studied the methylation patterns in exposed and unexposed animals and found significant differences between the two treatments. Overall, this study suggests that DNA methylation plays an important role in the toxicity response.

Biodiversity increases the stability of ecosystem functions in fluctuating environments. Only recently, parts of the underlying processes have been uncovered. A meta-analysis of biodiversity experiments manipulating primary producer richness revealed that the increased stability in more diverse systems was driven by an increased resistance (i.e. reduced changes), rather that an increased resilience (i.e. a rapid recovery). As many ecosystem functions, comprise the joint functional contribution of the species in the system, the stability of these ecosystem functions should depend on changes in the system’s composition. Theoretical models predict that an increased number of species interactions should slow down compositional changes. By consequence, biodiversity is expected to increase both compositional and functional resistance, but these predictions have never been put to the test. In this article, Baert et al. use marine diatom microcosms to demonstrate this tight link between compositional and functional stability.

Over the past 25 years, hundreds of empirical studies established that there is generally a positive relationship between the functioning of an ecosystem and the number of species it contains. Ongoing global biodiversity loss by anthropogenic activities therefore poses a major threat to future ecosystem function provisioning. However, recent studies showed that environmental stress, including exposure to chemicals, can alter the biodiversity-ecosystem functioning (BEF) relationship, and hence the consequences of biodiversity loss. In this paper Baert et al. reveal for the first time the mechanisms underlying changes in BEF relationships by environmental stress. By using a simple community model, Baert et al. demonstrate that changes in the BEF relationship in a marine microalgal microcosm experiment could be explained from species stress tolerances and the strength of per-capita species interactions.

Snails are important organisms in freshwater ecosystems, but they can be very sensitive to pollution with certain chemical substances. Our laboratory participated in the development of an internationally accepted chemicals toxicity test with a pond snail. This toxicity test can help to set more appropriate water quality criteria for chemicals.

For years, GhEnToxLab has had a fascinating collaboration with UGhent’s Atomic and Mass Spectrometry group (A&MS), which has lead to multiple joint papers. Now, the A&MS group - led by Prof. Dr. Frank Vanhaecke – is developing another radically innovative tool to quantify the elemental composition of single cells. Using laser ablation inductively coupled plasma-mass spectrometry (LA-ICPMS), the accumulation of Cu in a metal exposed marine dinoflagellate, Scrippsiella trochoidea, was measured. In this way, the mean Cu concentration in the cells was determined across different exposure levels, and the accuracy, efficiency and ability for high through-put of this promising technique was established.

Environmental factors including chemicals can induce changes that can affect the offspring of exposed animals for multiple generations. These effects are referred to as transgenerational effects and are often the consequence of changes in DNA methylation. Within this paper, we have focused on understanding the role of DNA methylation by studying the patterns of methylation at the genomic level in two Daphnia species. We observed that these patterns are not random but are associated with the size of the gene family. This suggest that DNA methylation may help regulate the function and size of gene families which in turn may play an important role in stress response.

Harmful algal blooms, produced by cyanobacteria, 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, one major factor being warmer temperatures. 2015 was the warmest year on record. Before that it was 2014. The long-term trend of rising temperatures is likely to further promote the global expansion of cyanobacteria. As copper is commonly used as an algaecide to eradicate cyanobacterial blooms, we investigated the combined effects of copper and the toxic cyanobacterium Microcystis aeruginosa and how these were affected by temperature and food concentration. Our study shows that the interactive effects between copper and harmful algae blooms are not overly dependent on temperature and food concentration. Nevertheless the present study warns against the use of copper-based algaecides and suggests that environmental risk assessment of copper should consider specific situations where harmful M. aeruginosa blooms can co-occur.

Mostly, metal contamination comes as a mixture of different metals. These multi-component mixtures can produce significant mixture effects. In this study, metal mixture toxicity on barley root elongation was investigated. Mixture effects of four metals (Cu, Cd, Ni and Zn) were investigated when each metal was present in the mixture at a low effect concentration, i.e. individually only causing a small effect. Two commonly used ‘reference’ models (concentration addition and independent action) were used to test if it is possible to predict toxicity in these mixtures. In this study, it was shown that the toxicity of a mixture of metals was almost always larger than the effect of the most toxic metal in that mixture. In addition, it was found that a mixture of four metals, each causing individually < 10% effect, produced mixture effects up to 50%. This highlights the need to incorporate mixture toxicity in risk-assessment frameworks.

Previous studies have suggested that phosphorus (P) deficiency can increase the sensitivity of microalgae to toxic trace metals, potentially due to reduced metal detoxification at low cell P quota. The existing evidence is, however, inconsistent. This study was set up to determine the combined effects of zinc (Zn) and P supplies on Zn and P bioaccumulation and growth of the green microalgae Pseudokirchneriella subcapitata. Zinc toxicity was investigated in (i) a 24 h growth rate assay with cells varying in initial cell P quota with no supplemental P during Zn exposure and in (ii) a 48 h growth assay initiated with cells at the end of a 14-days steady state culture at three P addition rates (RARs) between 0.8 and 1.6 day−1. Our data at two experimental scenarios and the prediction under various relevant scenarios suggest a weaker effect of secondary stress factor (Zn) when nutrient deficiency (first stress factor) is prevailing.

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