PeerJ Award Winners at the 7th International Zooplankton Production Symposium

by | May 15, 2024 | Award Winner Interviews

We are living in the Anthropocene. Our oceans are warmer, more acidic, have widespread plastic and other pollution, and are subjected to increasing exploitation including overfishing. Zooplankton play a pivotal role in our oceans, as grazers of primary production, as drivers of carbon and nutrient cycles, and as prey for higher trophic level consumers including both harvested fish species and iconic marine mammals and seabirds. How zooplankton will respond to the dramatic changes in our marine ecosystems will impact the health and productivity of our oceans and our planet. The 7th International Zooplankton Production Symposium aims to better understand zooplankton in this changing world. The Symposium was held over five days from 17-22 March 2024 in the historic waterfront district of Hobart, Australia.

Kengo Egami Master’s student at the University of Tokyo, Japan.

Can you tell us a bit about yourself and your research interests?

I am Japanese, 23 years old and a scuba diver. I love the ocean and marine organisms (especially coral reef animals!). My research interests are centred on ocean issues such as microplastic pollution, biodiversity conservation, and climate change.

What first interested you in this field of research?

Whenever I dive in the water, I see a lot of plastic debris floating and sinking in the ocean. I want to help solve this problem, so I have focussed my research efforts on marine plastics.

Can you briefly explain the research you presented at the zooplankton symposium?

Microplastics (MPs) have emerged as a significant threat to marine ecosystems, but information on MPs smaller than 330 μm (SMPs) is limited by the lack of simple quantification methods. We examined the potential application of salps, pelagic tunicates that employ a non-selective filter-feeding habit, to estimate in-situ SMP densities. After collection, salp gut samples were dissolved using a multi-enzyme detergent and hydrogen peroxide, and then filtered through membrane filters to analyze MPs using micro-Fourier transform infrared spectroscopy. The results showed that 83.3% of gut samples (n=24) contained MPs (1.96±1.49 particles/individual), which ranged in size from 23 to 789 µm; 92.5% of these samples were SMPs. The MP composition and size were similar to those in ambient seawater. Furthermore, when the quantity of MPs in the gut samples was converted to in-situ densities using previously published feeding parameters, MP densities ranged between 235 to 1377 particles/m3. These densities were strongly correlated with those in ambient seawater at the study site, as evidenced by a regression slope of 0.97. The findings suggest that this method accurately estimated in-situdensities of SMPs. Importantly, this method is less labor intensive than other methods and could improve the monitoring of SMP pollution, including historical assessments.

What are your next steps?

This salp-analysis method offers a novel approach to easily estimate in-situ SMP density without a laborious process and thus it will improve the monitoring of SMP pollution. This approach could be applied to examine the historical contributions of SMPs by analyzing the gut of archived salp samples, so I will analyze them as the next step. Examining such long-term changes in SMP ingestion by salps may provide valuable insights into the effect of SMP pollution on marine food chains.

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