Field observations reveal microplastic transfer in marine planktonic food chains

Microplastics widely distributed in the ocean are readily ingested by marine organisms, particularly zooplankton, whose food particles are similar in size to microplastics.

Chaetognaths, typical carnivorous zooplankton in the ocean, feed primarily on copepods. They play a crucial role in linking secondary producers (such as copepods) to higher trophic level organisms within the food chain.

Recently, a research team led by Prof. Sun Xiaoxia from the Jiaozhou Bay Station at the Institute of Oceanology of the Chinese Academy of Sciences (IOCAS) conducted a pioneering study on the seasonal characteristics and risks of microplastic ingestion by chaetognaths in Jiaozhou Bay based on field observation data.

The study is published in the Journal of Hazardous Materials.

Researchers assessed the impact of copepods on chaetognaths' microplastic ingestion. Copepods are the primary prey of chaetognaths.

Results indicated that there was no seasonal variation in microplastic ingestion by chaetognaths. The Pollution Load Index (PLI) of microplastics in chaetognaths was relatively low, whereas both the Polymeric Hazard Index (PHI) and Potential Ecological Risk Index (PERI) were relatively high.

This study is among the first to provide field evidence of microplastic transfer along marine planktonic food chains.

Further comparison between chaetognaths and copepods demonstrated that the number of microplastics in chaetognaths was positively correlated with copepod abundance and the number of microplastics in copepods.

"The microplastics ingested by chaetognaths were found to be highly similar to those in copepods, predominantly fiberous in shape, 101-400 μm in size and polyester in polymer type," said Meng Liujiang, first author of the study and a researcher from Sun's team.

Long-term exposure and ingestion of microplastics by higher trophic level organisms may lead to continuous accumulation of microplastics within their bodies. Calculation of the biomagnification factor showed that chaetognaths have a much higher individual-level accumulation of microplastics in the copepod–chaetognath food chain, suggesting a potential risk of biomagnification.

"Our work provides critical field evidence for the transfer of microplastics through marine planktonic food chains, laying an important foundation for future research on the fate of microplastics in the ocean and their potential ecological risks," said Prof. Sun, the corresponding author.