Source-Specific Patterns of Marine Debris and Associated Ecological Impacts in the Red River Estuary of Xuan Thuy National Park, Vietnam

Abstract

Vietnamese rivers are among the top ten contributors of anthropogenic debris to the ocean. However, there is limited empirical research documenting debris and its effects in Northern Vietnam. The goal of our research was to conduct the first baseline assessment of anthropogenic debris in the Red River. We aimed to understand the sources, accumulation patterns, and ecological effects of anthropogenic debris in the Red River (Song Hong) estuary. To assess debris patterns, we conducted standing stock debris surveys at sites in the mouth, and upstream of the Red River. To assess the ecological effects of anthropogenic debris on mangrove ecosystems, we measured mangrove diameter, canopy cover, and number of crab burrows/m2 in the same debris transects. Anthropogenic debris was found at all sites, and plastic was the most common material. We identified a non-significant trend, whereby ecological indices declined with increasing amounts of debris. Overall, our results demonstrate that anthropogenic debris is ubiquitous in the Red River estuary, composition varies among sites, and this debris may have adverse or neutral ecological effects on mangrove ecosystem health. Future work should conduct debris assessments at larger spatial scales, and assess ecological responses at the community or population level over extended time periods.

Plastic pollution of four understudied marine ecosystems: a review of mangroves, seagrass meadows, the Arctic Ocean and the deep seafloor

“…In Indonesian mangroves, four indicators of tree health were negatively correlated with debris density [39]. Similarly, three indices of mangrove health decreased with increasing amounts of debris, although only non-significantly, with variation explained ranging from 6% to 13% [43]. Observations further suggest that plastic debris hindered photosynthesis, smothered and thus suffocated pneumatophores, led to root deformation, disrupted aeration and water movement, which can lead to decreased soil quality, and directly sacrificed mangrove trees, particularly seedlings, because plastics physically broke down seedlings [39,[44][45][46][47][48][49][50][51].…”

“…For mangroves, we have a number of observational studies reported harm. However, to the best of our knowledge, we have so far only three correlational studies [39,43,47] and one experimental study [42] for the impacts of macroplastics and one meta-analysis for the impacts of microplastics [30]. For seagrass meadows, there were only three mesocosm experiments [67,69,70] for the impacts of macroplastics and none for microplastics.…”

Developing a method for estimation of plastic waste leaked into the ocean

“…However, the method for a global scale estimation is uncertain due to lack of consideration for local conditions of each country. Other studies in Viet Nam have previously focused on riverine plastic debris [13][14][15][16]. Lack of reliable and scientific methods for marine plastic debris estimation is a knowledge gap in the action against plastic pollution in Vietnam [17].…”