New Publications

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.

We determined whether a realistic mixture of hydrophobic chemicals affects the growth dynamics of a marine diatom and how this effect compares to the effect of temperature, light regime and nutrient conditions. Passive dosing was used to expose a marine diatom to a realistic mixture of hydrophobic compounds accumulated from Belgian coastal waters using passive samplers. Although ∑7PCBs exceeded the environmental quality standards (2 ng L− 1), we did not observe adverse ecotoxicological effects in a 72 h algal growth inhibition test with P. tricornutum. Natural drivers such as nutrients, temperature and light availability, explaining about 85% of the observed variability, are more important drivers of the growth of P. tricornutum than the mixture of organic pollutants present in Belgian coastal waters.

The chronic toxicity of Ni is strongly dependent on the physico-chemistry of freshwater environments. Metal bioavailability models predict metal toxicity in receiving waters by taking into account the effects of pH and the formation of (in)organic ligand on metal bioavailability and the effects of cations, such as Ca & Mg, on metal uptake. Currently, the Environmental Quality Standard (EQS) for Ni in the Water Framework Directive (WFD) is bioavailability based. Although some of the available chronic Ni bioavailability models are only validated for pH up to 8.2, a considerable fraction of the European surface waters has a pH above 8.2. Therefore, we investigated the effect of a change in pH from 8.2 to 8.7 on chronic Ni toxicity to 3 invertebrate and 2 plant species. Next, we investigated whether the existing chronic Ni bioavailability models could be used to predict chronic Ni toxicity above pH 8.2.

As the human population continues to expand, scientists and politicians are faced with a simple question: will we be able to feed ourselves in the future? Many of our food sources are at peak productivity and only in a few sectors, such as the aquaculture industry, is significant growth feasible. However, these sectors are also faced with global concerns like climate change. The rise of sea surface temperature will affect marine ecosystems in drastic ways. Among others, pathogens and harmful algae are expected to benefit from a warmer environment. As a result, both wild and cultured bivalves will become more frequently exposed to these stressors.

For the Marine Environmental Research Special Issue on “Particles in Oceans”, we contributed with a comprehensive review on microplastics in sediments. For this review we analysed literature dating back to the 1970s, in order to gain insights in the worldwide occurrence of microplastics in sediments, processes that drive their distribution and effects of this type of pollution on sediment associated organisms. Based on this extensive literature review (over 120 publications), we were able to identify several shortcomings in microplastics research and formulate recommendations to deal with these issues in the future. Although important advances have been made in the past decade, we describe the need for standardisation and harmonisation of sampling and extraction techniques, and the need for more realistic effect assessments for microplastics.
 

There is growing evidence that pollution has consequences that can extend beyond exposed generations and may involve trans-generational responses as well as rapid micro-evolutionary processes. A recent testimony of microevolution in fish of the Elizabeth River in Virginia, a water body so polluted that it has been termed a "toxic hot spot", reported costs of adaptation to this polluted environment. These fish displayed lower survival in clean water and appeared more sensitive to additional stressors. Most ecotoxicological test guidelines are only considering effects within one generation, thus potential detrimental effects across generations are under-evaluated. Here we conducted a natural selection experiment over several generations with a natural Daphnia magna population.

Over the past years, GhEnToxLab has developed an active and fascinating collaboration with the UGhent’s X-ray Microspectroscopy and Imaging Group (XMI). This lab, led by Prof. dr. Laszlo Vincze, is specialized in the development of synchotron radiation-based tools for micro X-ray imaging, absorption spectroscopy and fluorescence analysis. Among other techniques, they are currently developing a method that uses lasers to trap and manipulate single celled organisms in their native environment. The optically trapped organism can then be subjected to micro X-ray fluorescence imaging, providing us with a radically new tool to map the subcellular elemental composition of these cells.

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