2018 Fiscal Year Annual Research Report
Connecting community level impacts of micro-plastics to differences in feeding modes among species
| Project/Area Number |
18F17405
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| Research Institution | Kochi University |
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Principal Investigator |
池島 耕 高知大学, 教育研究部自然科学系農学部門, 教授 (30582473)
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| Co-Investigator(Kenkyū-buntansha) |
VERMEIREN PETER 高知大学, 自然科学系, 外国人特別研究員
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| Project Period (FY) |
2018-04-25 – 2020-03-31
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| Keywords | microplastics / sediment / analysis protocol / crabs |
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| Outline of Annual Research Achievements |
1) The protocol to extract microplastics from sediments and crabs has developed. The protocol includes a method for organic matter reduction, that specifically targets samples with high organic matter content such as estuarine sediments. Additionally, the method uses a process of density separation using Zinc Chloride Solution and a newly developed extraction column. This new column allows larger amounts of sediment to be processed, is more cost effective and has above 90% recovery rates across different microplastic types. The protocol further includes staining with fluorescent dyes for microplastics quantification and measurement using microscopic imaging and automated image analyses software. In a final step, the protocol allows for material (polymer) identification of selected microplastics using micro-Fourier Transform Infrared Spectroscopy (μFT-IR). With this protocol, we could quantify microplastics down to 60 μm and detect microplastics down to 30 μm. We also initiated a collaboration with colleagues in Uruguay. They successfully tested our protocol on beach sediments and will now apply it in further research.
2) We collected samples of crabs and from the sediment surface at the Kokubu estuary, Kochi, and extracted microplastics from the sediment using our newly developed protocol, revealing up to 6000 microplastics per kg. The density tended to be higher in vegetated sites than on mudflats. Preliminary analysis of crab gut also showed microplastic contamination.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
Regarding objective 1) We identified that μFT-IR mapping, although suggested as a methodological improvement in the scientific literature, did not work when applied to a real life environmental monitoring situation. Indeed, due to the long time required to process samples using this technology (more than 1 day per sample for quantification alone), we found that it could not be used for large scale environmental monitoring of microplastic pollution. Consequently, we had to spend more time in developing a new protocol than originally planned, and test a number of different alternatives. Nonetheless, the protocol is now ready, and a final draft of a publication on this protocol is ready for submission to an international scientific journal.
Regarding objective 2) All samples have been collected. Sediment analysis is complete. However, analyses of crab gut content samples is still ongoing. The requirement to develop a new protocol for microplastic extraction and identification required us to delay analysing these samples. Nonetheless, the analyses are ongoing and we have the assistance of a research student to finish these analyses.
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| Strategy for Future Research Activity |
We will finish analysing crab gut content samples to establish their feeding ecology. We will also use stable isotope analyses to back up gut content samples. By combing gut content and stable isotope analyses, we can get an accurate idea of the feeding ecology of the species. We can then link the feeding ecology and habitat preferences of crabs to their exposure to microplastics. By explicitly taking into account the ecology of the species, the results of the analyses can also be applied to make predictions regarding the effects of microplastics on other estuarine organisms.
We will continue field sampling and analyses of microplastics in the environment. These samples will allow us to develop a microplastics risk map. This risk map links the concentrations of microplastics in the sediment surface of estuarine habitats to the concentrations detected in the crabs. Field sampling is already finished and laboratory analyses of the samples using our newly develop protocol are currently ongoing.
Laboratory experiments will be used to verify the observed correlation between crabs and microplastics under controlled conditions. Laboratory and field observations will then be combined into a statistical model of the relationship between crab community structure and microplastics concentrations in the environment. We will also take other environmental influence factors such as sediment composition and salinity into account. Statistical modelling will focus on generalized linear models to capture species diversity and abundance relations with multivariate environmental conditions.
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Research Products
(3 results)
