Environmental Toxicology Group members work on the toxicological evaluation of microplastics or microfibers on the marine organism and micro-ecosystem. We are interested in evaluating the effects of microplastics/microfibers on the aquatic environment from the molecular to the community level.
Over the past ten years, microplastics (MPs) have become a prominent environmental concern of the public and scientific community, mainly because of their frequent and ubiquitous detection in salt- and freshwater ecosystems. The term “microplastic” was first proposed by Ryan and Moloney in the 1980s and was defined as a small plastic particle < 5 mm in diameter by NOAA in 2008. Aquatic organisms can interact with MPs through various pathways, including direct or indirect ingestion, respiration, or attachment to their surface. Microfibers (MFs), as one of the most common MPs, distribute highly overlaps with the dense population areas and pose a threat to biota, especially to humans.
The members of the Environmental Toxicology Group focus on the toxicological evaluation of MPs/MFs on the shellfish and microcosmic system. The results can provide the necessary data for ecological risk assessment and help raise public risk perception of MFs. Eventually, contribute to the formulation of risk management policies for MPs.
研究テーマ １：Uptake and Effects of Microfibers on Freshwater Indoor Microcosm System
This research proposes to conduct synthetic, plant, and mineral MFs exposure experiments in a freshwater indoor microcosmic system with three trophic levels of the food chain (producer, first-level consumer, and second-level consumer). The stress response and adaptation of three model species on introduced MFs will be evaluated from molecule to community-level under controlled biotic and abiotic conditions. Combining multivariate and statistical analysis methods, qualitative and quantitative analysis of the comprehensive effect of different materials and different concentrations of MFs on the microcosm will be carried out. We want to figure out:
a. Does MFs provide special effects on the biota due to their fibrous shape?
b. Compared with the natural MFs, what is the difference in the effects of synthetic MFs on the biota?
c. To obtain data with higher ecological relevance than previous studies that on each species separately
It is possible to build a bridge between the laboratory and the ecosystem, which helps confirm extrapolations from laboratory data to the environment.
研究テーマ ２：Uptake and Effects of Microplastic Fibers and Fragments on Seawater Commercial Bivalves (Oyster and Scallop)
In 2018, global plastic production has almost reached 360 million tons and approximately 8 million metric tons of plastic enters the ocean annually. Petroleum-based plastics do not biodegrade; they will break down into smaller pieces over time into microplastics. In the ocean water column, microplastics are mostly found in fiber shape and fragments with a concentration of 52% and 29% respectively. In terms of polymer type, the greatest proportion found was polypropylene (PP) with 17% followed by polyethylene (PE) and polyethylene terephthalate(PET) with 15% each. The presence of these microplastics in the ocean poses risks to marine biota as they are ingested by various marine organisms. Due to their high surface area to volume ratio, microplastics are able to adsorb hydrophobic contaminants such as Persistent Organic Pollutants (POPs) which may increase their toxicity when ingested. Based on the fishery production statistic survey in Japan, oysters and scallops are the two most produced bivalves. They both are susceptible to microplastics exposure from the water column and sediment. This research aims to study the effects of microplastic ingestion by bivalves. PP and PET with benzo(a)pyrene (BaP) are used to represent plastics and POPs in the ocean. Exposure of plastics are carried out in the form of microplastic fragment and fiber to find the type and shape preferred by the bivalves during ingestion. Qualitative and quantitative analysis is carried out by using laser scanning confocal microscope (Fig. 1). Subsequently, the most ingested plastic will be spiked with BaP to observe the transfer of contaminant into the oysters and scallops. Toxicological analysis will be performed to determine the systematic effects in the bivalves.