New Publications

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.

Through global shipping and trade, mankind has inadvertently spread marine organisms to such an extent that many are now considered cosmopolitan. Further aggravated by changes in the foodweb structure (overfishing), eutrophication and climate change, this has led to a substantial increase in the occurrence of harmful algal blooms (HABs). Next to the large potential for environmental damage, these recurring events have become a global public health concern as many species produce potent marine toxins that may lead to shellfish poisoning. To ensure food safety, the mouse bioassay has long been used to screen seafood for the presence of these toxins. Due to ethical concerns, however, this test is now being replaced by alternative chemical analyses.

Microplastic pollution is increasingly being considered as a threat to the marine environment in general and to small marine invertebrates at the base of the food chain in particlular As microplastics occur both in the seawater and in the sediment, we investigated the potential for microplastic ingestion in two organisms inhabiting these environments: the blue mussel (Mytilus edulis) and the lugworm (Arenicola marina). As a follow-up to our previously published research, the microplastic load in field-collected organisms - i.e. exposed to ambient microplastic concentrations - was assessed.  In all collected specimens, we detected low concentrations of microplastics in both species, although the sediment dwelling lugworms contained somewhat higher concentrations. Subsequently, potential impacts of microplastic uptake of these species were assessed. Although some responses were measured, we detected no significant adverse effects of microplastic ingestion.