Structure – Interdisciplinary topic “biological effects”
Within project section B, the sub-projects will cooperate intensely in order to characterize the biological effects of microplastics. The project partners will cover cellular effects in vitro and in vivo and examine apical toxicological end points in various invertebrates and fish. The uptake of microplastics by fresh water organisms will further be examined spectroscopically. In addition, the food web transfer of microplastics will be assessed by cooperations within the project. Toxicity studies on primary producers (e.g. green algae) are not envisaged explicitly.
For the toxicity studies in project area B, it is important that the same microplastic testing materials be provided by means of particle distribution, polymer type, fresh and aged. The choice of microplastic material used in project section B will be made consensually. This will also take into account results from project section A on the significance of different microplastic materials. Before such results will be available, the surveys conducted in the first 6 months will include commercially available, fluorescent, as well as self-made microplastics. The used microplastics will be chosen by their density: Polymers with densities around 1 g/L remain in the aqueous phase and are therefore relevant for pelagic organisms. Microplastics with densities larger than 1 g/L sediment and therefore will be used on benthic species. The applied particles sizes will be adapted to the respective species. Solvents or dispersing agents will mostly not be utilized, as many microplastic particles – different from nanomaterials – suspend fairly well in aqueous media.
However, there are hydrophobic microplastic particle materials which easily adhere to surfaces or coagulate to flocs. This can reduce the bioavailability substantially. Therefore, it will be necessary to provide in particular very small microplastic particles in disperse states, for example using low concentrated biologically inactive dispersing agents or by partly oxidizing microplastic particles to create negatively charged surfaces. The adsorption of natural organic substances (humic substances) can also contribute strongly to dispersing, which will be examined, too.