Abstract:
Microplastic (MP) pollution is a critical global environmental issue, with severe impacts on sensitive
coastal ecosystems such as mangrove forests. These ecosystems are vital for “blue carbon” storage but
are increasingly threatened by plastic pollution. This study presents a systematic review and metaanalysis exploring how microplastics influence carbon sequestration and ecosystem functioning in
mangroves, with a specific focus on Sri Lanka. Following PRISMA 2020 guidelines, it synthesizes
findings from major electronic databases, including Web of Science, Scopus, PubMed, Google Scholar,
ScienceDirect, and ResearchGate. Alongside grey literature from Sri Lankan institutional repositories.
Studies were selected based on clear inclusion criteria. In total, 850 records were identified from
database searches, along with an additional 150 records from other sources. After duplicates were
removed, 720 records remained for screening. From these, 450 were excluded based on initial review,
leaving 270 full-text articles to be assessed for eligibility. Of these, 120 articles were further excluded
for various reasons. In the end, 150 studies were included in the systematic review, of which [X] studies
were included in the qualitative synthesis and [Y] studies with sufficient quantitative data were included
in the meta-analysis (X+Y=150). The review investigates the occurrence, distribution, and
characteristics of microplastics (including size, polymer composition, and abundance) across mangrove
sediments, water, and biota. Furthermore, it evaluates MP impacts on key ecological processes such as
carbon storage, microbial activity, nutrient cycling (N, P, and K), and biodiversity. The findings indicate
that microplastics alter the physical and chemical properties of mangrove sediments, slow down organic
matter decomposition, and potentially increase methane emissions. These changes may ultimately
reduce the long-term carbon sequestration capacity of mangrove ecosystems. Additionally, MP
contamination negatively affects mangrove organisms and associated fisheries, posing socio-economic
risks to local communities. Overall, the results emphasize the urgent need for effective conservation
strategies and evidence-based policies to reduce plastic pollution and protect mangrove ecosystems.
Key research gaps in Sri Lanka include limited field data on microplastic abundance and polymer
composition in mangroves, insufficient understanding of their effects on sediment carbon storage and
microbial communities, and a lack of long-term monitoring of ecosystem impacts. Future research
should prioritize site-specific assessments of microplastics in sediments, water, and biota, investigate
their influence on carbon sequestration, evaluate their movement through mangrove food webs and
impacts on fisheries, and establish standardized detection and monitoring methods. Addressing these
gaps will provide stronger scientific evidence to support effective mangrove conservation and policy
development in Sri Lanka.
