Bioavailability of microplastics and ingestion in zooplankton in Sepanggar Bay, Sabah

• Main Author: Tang, Chung Ngo
• Format: Thesis
• Language: English; English
• Published: 2023
• Subjects: QL1-355 General Including geographical distribution; QL1-991 Zoology
• Online Access: https://eprints.ums.edu.my/id/eprint/40985/1/ABSTRACT.pdf; https://eprints.ums.edu.my/id/eprint/40985/2/FULLTEXT%20%281%29.pdf; https://eprints.ums.edu.my/id/eprint/40985/

Microplastics (MP) is an emerging global environmental concern due to their widespread abundance in the marine environment and increasing documentation of ingestion by marine organisms, including small lower trophic zooplankton. This study examined the spatiotemporal variation of MP in the water column and ingestion by marine zooplankton relative to monsoon seasons in Sepanggar Bay, Sabah, Malaysia. MP and zooplankton samples were collected in vertical tows using 20 μm and 300 μm plankton nets, respectively, from October 2021 to August 2022, covering the Northeast monsoon (NEM), Southwest monsoon (SWM) and inter-monsoon periods (INTER). Preliminary investigation showed that MP were vertically distributed in the water column, with a significantly higher MP concentration in the water column (82.7 ± 10.8 particles/m3) than in the surface water (34.8 ± 5.7 particles/m3). MP concentration decreased from SWM (106.6 ± 23.0 particles/m3) to NEM (63.0 ± 8.0 particles/m3) and INTER (31.2 ± 6.7 particles/m3), with a significant seasonal difference between SWM and INTER. MP were observed in all eight zooplankton taxonomic groups examined (Appendicularia, Chaetognatha, Cladocera, Copepoda, Decapoda, Hydrozoa, Ostracoda and Salpidae). The average MP ingestion varied from 0.001 ± 0.001 (Ostracoda and Appendicularia) to 0.045 ± 0.028 particles/ind. (Salpidae) and increased along the planktonic food chain. MP ingestion decreased significantly from carnivorous to omnivorous and herbivorous zooplankton, suggesting the influence of zooplankton feeding behaviour on MP ingestion. The composition of MP in the water column and zooplankton was homogeneous, dominated by fibrous and translucent MP. Nine of the twelve polymers identified were high-density polymers, with polyethylene terephthalate being the most prevalent in the water column (55.6%) and zooplankton (23.1%) samples. The presence of lowand high-density polymers in zooplankton highlights their susceptibility to ingesting MP due to their vertical migration behaviour. MP composition in the water column formed distinct groups relative to monsoon seasons and associated with temperature, rainfall and wind speed, suggesting that MP composition in the water column tracked monsoonal changes of environmental conditions. In addition, all environmental variables were found to have a significant influence on MP concentration in the water column in the order of salinity > rainfall > wind speed > temperature. Increased rainfall during SWM may have increased the concentration of MP from land-based sources (river discharge and runoffs). The low MP concentration coincided with high wind speed during monsoon transition periods could be due to the high dispersion towards the open sea caused by heavy winds. The interactions of salinity, rainfall and temperature are important in regulating seawater density and the vertical distribution of MP in the water column. The present work provides new insight into the interactions between MP and zooplankton in the water column in the tropical marine ecosystem. This information is of great importance to bridging field observations and laboratory studies to improve impact assessment of marine MP pollution, which contributes to the United Nations Sustainable Development Goal 14 - conserve and sustainably use the oceans, seas and marine resources for sustainable development.