The effects of microplastics on freshwater phytoplankton and zooplankton communities in a boreal lake
Our understanding of the potential impacts of microplastics (MPs) on freshwater ecosystems is limited. There is evidence that high MP concentrations can negatively impact phytoplankton and zooplankton under laboratory conditions, but community level effects under natural conditions are unknown. Two large scale in-situ mesocosm (limnocorral) experiments were conducted at the International Institute for Sustainable Development Experimental Lakes Area (IISD-ELA) in northwestern Ontario, Canada to assess the responses of phytoplankton and zooplankton communities to MP additions. In the first experiment, a mixture of common polymers (polyethylene; PE, polystyrene; PS, and polyethylene terephthalate; PET) were added in equal contributions to limnocorrals in a range of environmentally relevant nominal concentrations (0-29,240 MPs/L for all polymers together). In the second experiment, the same mixture of polymers was added to limnocorrals at a total concentration of 29,240 MPs/L each with and without chemical additives and these were compared to controls with no MPs to distinguish if there was a physical or chemical mechanism for MP toxicity. Phytoplankton biomass was not affected in either experiment, but there may be some potential for MPs to affect chlorophyll a production and community composition over time. There was weak evidence that zooplankton abundance and biomass were stimulated by MPs in both experiments, and copepod reproduction was slightly reduced. Overall, there was little evidence of significant negative impacts of MPs on the plankton communities.
microplastic, zooplankton, phytoplankton, community effects