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National Committee on Marine Sciences (NCMS)

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Author: search.filters.author.Onda, Deo Florence L.Ocean Decade Challenge: search.filters.odc.Challenge 7: Expand the Global Ocean Observing System

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    Assessing the efficiency of microplastics extraction methods for tropical beach sediments and matrix preparation for experimental controls
    Bonita, Jan Danielle P.; Gomez, Norchel Corcia F.; Onda, Deo Florence L. (Frontiers Media SA, 2023-11-03)
    Introduction: Microplastic pollution has become a global issue, eliciting attention not just from the scientific community but also both from the public and governmental bodies. Drawing data-driven policies and interventions, however, remain difficult due to the severely lacking baseline information from different environments such as beaches. One of the challenges in doing baseline studies is the lack of harmonized methodologies that will allow for comparison of results, integration of data, and its effective translation to evidence-based policies. Emphasis on quality control measures among baselining efforts through the proper implementation of experimental controls is also lacking. Methodology: To address these gaps, we compared methodologies for preparing the sediment matrix for experimental controls, as well as evaluated protocols for extracting microplastics from tropical beach sediments. Beach sediments were collected, dried, sieved, and spiked with known amounts of microplastics of different polymer types. The removal and extraction efficiencies of the protocols being compared were evaluated. Results and discussion: Our results showed that subjecting beach sediments to a furnace at 550° C for 4 hours is the most efficient way to remove plastic contamination, implying its applicability for preparing experimental controls. Meanwhile, a modified version of Masura et al. (2015), one of the widely cited methodologies for microplastics extraction, exhibited the highest mean extraction efficiency (99.05 ± 0.82%) among the protocols being compared. Results of this work will be useful in identifying methods that can be adopted and utilized for research and baselining efforts not just in the Philippines but also in Southeast Asia. This will also be helpful in the harmonization of methods, data reporting, and even skills as implemented through the regional and national action plans to address marine plastic pollution.
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    Effects of monsoons and storms on the structuring and diversity of picoeukaryotic microbial communities in a tropical coastal environment
    De La Cruz, Maria Anna Michaela; Hingpit, Brian William; Guillou, Laure; Onda, Deo Florence L. (Elsevier, 2023-06)
    Picoeukaryotes are key components in marine ecosystems that play crucial roles in food webs and biogeochemical cycles. Despite their significance, many aspects of their community ecology and diversity remain understudied. Here, we investigated the taxonomic and functional diversity of picoeukaryotic communities in response to monsoonal patterns and weather disturbances brought about by storms, characterizing tropical coastal regions. To do this, water samples were collected almost weekly or bi-weekly at a single location in a tropical coastal environment covering the late northeast (NE) and southwest (SW) monsoons. We then performed high-throughput amplicon sequencing of the V4 region of the 18S rRNA gene to generate taxonomic profiles of the communities across time. Clustering based on environmental parameters grouped our samples into months associated with NE monsoon, SW monsoon, and stormy SW monsoon, demonstrating seasonality influenced by monsoons and storms, typically observed in tropical coastal waters. In comparison, clustering based on abundance only grouped the samples into NE and SW monsoon, with most communities during storm period joining the NE monsoon samples. These samples exhibited greater diversity, with smaller taxa such as Syndiniales, Prymnesiophyceae, Picozoa, Cercozoa, Stramenopiles, and Chlorophytes being the most abundant groups present. In contrast, SW monsoon samples have lower diversity but have become generally dominated by large-celled taxa, mostly diatoms. Multivariate and correlation analyses both revealed nitrate as the strongest environmental driver of the picoeukaryotic community structuring. Meanwhile, network analysis grouped the taxa into three modules, more consistent with the clustering based on environmental parameters, implying that although storms may not significantly change the community composition, they may however influence the dominating taxa. Each module was composed of a unique set of co-occurring taxa, highlighting high turnover of picoeukaryotic communities between each season. In addition, our results showed that SW monsoon-associated module had higher interconnectivity than other modules, suggesting that the interactions during this period may be less species-specific, thus, more adaptable than during NE monsoon. However, we observed that extreme fluctuations caused by storms could have possibly allowed for selection of dominant taxa. Shotgun metagenomic sequencing of representative samples from each monsoon period also revealed that differently abundant functional genes, particularly genes associated to nitrogen metabolism, might have also helped in adaptation to the changing nutrient conditions. Our observations provide new insights on the potential trajectory of microbial communities under environmental stresses, which are important in understanding the implications of emerging threats such as coastal eutrophication and climate change.