The fate of plastic litter within estuarine compartments: An overview of current knowledge for the transboundary issue to guide future assessments

Abstract

Plastics can enter biogeochemical cycles and thus be found in most ecosystems. Most studies emphasize plastic pollution in oceanic ecosystems even though rivers and estuaries are acknowledged as the main sources of plastics to the oceans. This review detected few studies approaching the transboundary issue, as well as patterns of estuarine gradients in predicting plastic distribution and accumulation in water, sediments, and organisms. Quantities of plastics in estuaries reach up to 45,500 items m À3 in water, 567,000 items m À3 in sediment, and 131 items per individual in the biota. The role of rivers and estuaries in the transport of plastics to the ocean is far from fully understood due to small sample sizes, short-term approaches, sampling techniques that underestimate small plastics, and the use of site-specific sampling rather than covering environmental gradients. Microfibres are the most commonly found plastic type in all environmental matrices but efforts to re-calculate pathways using novel sampling techniques and estimates are incipient. Microplastic availability to estuarine organisms and rising/sinking is determined by polymer characteristics and spatio-temporal fluctuations in physicochemical, biological, and mineralogical factors. Key processes governing plastic contamination along estuarine trophic webs remain unclear, as most studies used "species" as an ecological unit rather than trophic/functional guilds and ontogenetic shifts in feeding behaviour to understand communities and intraspecific relationships, respectively. Efforts to understand contamination at the tissue level and the contribution of biofouling organisms as vectors of contaminants onto plastic surfaces are increasing. In conclusion, rivers and estuaries still require attention with regards to accurate sampling and conclusions. Multivariate analysis and robust models are necessary to predict the fate of micro-and macroplastics in estuarine environments; and the inclusion of the socio-economic aspects in modelling techniques seems to be relevant regarding management approaches.

The role of mesopelagic fishes as microplastics vectors across the deep-sea layers from the Southwestern Tropical Atlantic

“…The wide availability of MPs is expected to threaten biodiversity throughout the marine environment. Plastic debris is found all along the coastal zone, continental slope, around oceanic islands, seamounts, and even in the deepest parts of the ocean (Cai et al, 2018;Monteiro et al, 2018;Lins-Silva et al, 2021;Pinheiro et al, 2021). Differences in the ecological habits, such as feeding strategy and migration, might influence the MP uptake by marine species.…”

The use of bioshields for coastal protection in Vietnam: Current status and potential

“…Similar to coral reefs, saltmarshes also have a significant potential in wave height reduction and shoreline protection. In fact, salt marshes and mangroves provide a high number of benefits (erosion control, coastal protection, tourism and recreation, food and raw materials, nursery habitat for fish, pollution storage, water purification and carbon sequestration and education) (Barbier et al 2011;Celis Hernandez et al 2020a, b;Pinheiro et al 2021). Saltmarshes are located at high elevation intertidal zones and hence can be more effective in wave attenuation compared to seagrass meadows or coral reefs, which are found in lower intertidal/subtidal areas (Bouma et al 2014).…”

Abundance and distribution of microplastics in tropical estuarine mangrove areas around Penang, Malaysia

“…Polymer detection in this study showed common polymer types that are commercially produced and highly consumed, including PE, polypropylene, polystyrene, and polyvinyl chloride (Wang et al, 2021;Yuan et al, 2022). They are commonly found in the environment because of their frequent disposal (short service life) and light weight, meaning they can easily be carried in the environment (Pinheiro et al, 2021). All of the above polymers were categorized by Brown (2022) as hazardous agents produced from plastic processing.…”