The presence of vast amounts of plastics in our oceans is cause for great concern for our marine wildlife due to their toxicity, persistence and ubiquity. With the production of plastics increasing, these pollutants are entering our oceans and breaking down into microplastics (MPs) at an ever-increasing rate. Microplastics are buoyant fragments of <5mm which can easily and readily enter the food chain by ingestion and bioaccumulation. This is potentially detrimental to the health of the organisms involved as plastics contain harmful chemical additives such as bisphenols and phthalates which are known to be released from the polymer over time.
Due to our limited knowledge of the effects and distribution of MPs it is important for scientists to continue research on MPs to further understand the extent of the problem and to ensure appropriate policy changes happen in regards to the reduction of plastic use; particularly in disposable products, regulating the use of additives and recycling plastic products more effectively. For this reason, we have developed a project to identify the amount of microplastic in the surface water in relation to an important food source, namely zooplankton.
Zooplankton are small organisms which drift in the surface water weakly swimming but primarily moved with currents. They make up part of the planktonic food chain along with phytoplankton. The planktonic food chain is the primary food source for a wide range of aquatic animals including fish and whales. As zooplankton are a key base component of many food webs the potential for the MP contained in zooplankton and the MP that are consumed because they are mistaken for zooplankton have a higher potential for bioaccumulation.
We are currently taking surface water samples, using a plankton net, both inshore and offshore. The samples are then fixed in 4% buffered formaldehyde to preserve zooplankton and left to separate in saturated saline solution. Once separated, the top fraction will be taken and filtered onto a 1.27 micrometre Whatman filter paper and viewed under a microscope to quantify microplastic fragments. The bottom fraction containing the denser biomass will be analysed for zooplankton and these will be counted using a Bogorov counting chamber. With these results, we can calculate the ratio of zooplankton to microplastic present.
Iskra Nicetic, BSc Biotechnology, University of New South Wales, Australia