Marine microplastics: how water mass dispersion affects transport rates.

Simulation of the trajectory of microplastic particles released into the North Atlantic Ocean after 0 days (a), 12 days (b), 38 days (c) and 76 days (d). Credit: Credit: Frontiers in Marine Science (2024). DOI: 10.3389/fmars.2024.1314754

Marine microplastics (1 μm–5 mm in diameter) are an ongoing concern, given their long lifetime (>100 years) in the environment and their impact on the organisms that inhabit them, especially when ocean currents transport the particles. It takes a long distance. Reaching the polar basin.

Often these microplastics wash up on beaches and mix into the sandy beaches we’re familiar with, but some zones have become particularly hot spots. The pollution is famously associated with five subtropical ocean gyres (circular currents in the North and South Atlantic, North and South Pacific, and Indian Oceans) that span millions of kilometers.2 Area of ​​floating surface microplastics.

Previous studies have suggested that the global floating marine debris crisis involves 15.6 trillion particles/year.

New research published I Frontiers in Marine Science He has focused on the beaches of the Canary Islands, famous Spanish tourist resorts, investigating the possible sources and transport routes of microplastics, both through ocean basins and the water column, until they finally Do not go ashore on these beaches.

Notably, the Canary Islands lie in the direct path of the North Atlantic subtropical gyre, as well as the surface wind-driven Canary Current. Four north-northeast-oriented beaches across the archipelago were studied for large-scale (>100 km) and mesoscale (10–100 km) transport mechanisms, these are: Playa Grande (Tenerife ), Playa de Famara (Lanzarote), Playa Lambra (La Graciosa) and Arenas Blancas (El Hierro).

These beaches are known for their marine debris problems, which exceed 100 grams of plastic/m.2 and 3,000 particles/m2.

Credit: Frontiers in Marine Science (2024). DOI: 10.3389/fmars.2024.1314754

Dr. Daura Vega Moreno, assistant professor at the Universidad de las Palmas de Gran Canaria, Spain, and colleagues focused over a multi-year period on the speed of currents, specifically in the 27°–32°N latitude range, and How was it affected? Transport of marine debris through the water column in the open ocean.

An open ocean focus is important because the factors affecting microplastic transport differ from those in coastal areas, where the latter are generally related to density, size and shape, so smaller and lighter materials are transported by wind and waves. are taken further inland.

In contrast, for open waters, the internal structure of the plastic and its state of degradation play an additional role, as well as water column temperature, convection and the Coriolis effect (wind to the right in the Northern Hemisphere and to the right in the Southern Hemisphere). I turn left).

The research team used data from several projects where microplastic particles had been released into the ocean since 2017, developing sea-based technologies as well as direct sampling of the water column during research cruises. Monitored.

After processing, a microscope was used to identify each type of marine debris, which contained a total of 260 microplastic fragments and fibers. All of this data was later used in modeling software to determine source-to-batch sink velocities and generate distribution maps.

Marine microplastics: how water mass dispersion affects transport rates.

Concentrations of marine microplastics (both fibers and fragments) obtained from 5 collection stations, sampled through the water column at depths of 50–1100 m. (NASW, North Atlantic Surface Water; NACW, North Atlantic Central Water; AAIW, Antarctic Intermediate Water; MW, Mediterranean Water). Credit: Credit: Frontiers in Marine Science (2024). DOI: 10.3389/fmars.2024.1314754

Dr. Vega-Moreno and colleagues identified a water depth of 200 m as a key depositional window for both fragments and fibers, while a water depth of 1,100 m <200 μm اور >200 μm is a critical point for high accumulation of both fractions. While the former may be caused by natural sinking the latter possibly connected in part to the inflow of Mediterranean water, the outflow of salinity from the Strait of Gibraltar.

This water sinks to a depth of 1,000–1,200 m to the sea floor in the Atlantic Basin under the Central Water of the North Atlantic and disperses towards the Canary Islands. The Mediterranean basin has high concentrations of both large pieces of plastic and microplastics, with an estimated 10% of global marine plastic pollution in the Mediterranean basin alone.

Smaller microplastics (<1 mm) and those that are flattened or degradable are likely to enter this descending water mass and therefore travel vast distances into deep ocean basins.

Estimating the transport pathways of marine microplastics and therefore where they may wash ashore is important for targeting removal techniques as well as for minimizing impacts on marine and coastal biota. This research highlights the role of deep-water bodies in dispersing plastic pollution, thus further work in intermediate (~1,000 m) to deep-water (>2,000 m) formation sites is essential, especially This includes the polar regions.

More information:
Daura Vega-Moreno et al., Exploring the origin and fate of surface and subsurface marine microplastics in the Canary Islands region, Frontiers in Marine Science (2024). DOI: 10.3389/fmars.2024.1314754

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Reference: Marine microplastics: How water mass affects dispersion transport rates (2024, February 21) Accessed 21 February 2024 at https://phys.org/news/2024-02-marine-microplastics-mass Retrieved from -dispersal-impacts.html

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