Microplastics limit zooplankton’s algae control

Nov. 10, 2023
Microplastics have been found to affect zooplankton’s predation on algae, bringing concern for increased risk of algal blooms in waterways.

New research shows that microplastics can limit the ability of zooplankton to control algal proliferation, according to a press release from Purdue University.

Uncontrolled algae growth can lead to harmful algal blooms, bringing cause for concern.

The study was presented in the journal Science of the Total Environment. The study was among the first to examine the effects of microplastics in a simple food web design. This involved investigating impacts on how zooplankton feed on algae in the presence of different environmentally realistic microplastic concentrations and when faced with risk of predation from fish.

Zooplankton are tiny creatures that live in watery environments and form the base of the food web in many aquatic environments. The organisms examined for the study were two common types of crustaceous zooplankton that differ in size and feeding behavior.

When the researchers noticed increased algal densities in their laboratory experiment after adding higher microplastic concentrations, they were uncertain about its cause. Either the microplastics were getting in the way of zooplankton and preventing normal consumption rates of algae, or they served as better surfaces for algal growth.

Follow-up tests showed that adding microplastics without the zooplankton failed to increase algae production. The microplastics were somehow affecting predation on algae.

Plastics can accumulate in biological tissue, similar to mercury and other heavy metals. But plastics also cause gut blockage and related effects that impact feeding. Even though plastics break down in the environment into smaller and smaller fragments, which is not necessarily a good thing, the process plays out over many years.

“In terms of the impact that microplastics have in the environment, there’s a level of uncertainty with these very small particles, in part simply because they are just very small, and also because they take on different shapes, sizes, configurations and surface properties,” said Chris Malinowski, director of research and conservation at the Ocean First Institute. “All of the research that has gone into this already and all that needs to be done is happening at too slow of a rate relative to the amount of plastic being produced, and this is alarming because we don’t truly understand all of the consequences.”