The vertical distribution of buoyant plastics at sea: an observational study in the North Atlantic Gyre

Abstract

Abstract. Millimetre-sized plastics are numerically abundant and widespread across the world's ocean surface. These buoyant macroscopic particles can be mixed within the upper water column by turbulent transport. Models indicate that the largest decrease in their concentration occurs within the first few metres of water, where in situ observations are very scarce. In order to investigate the depth profile and physical properties of buoyant plastic debris, we used a new type of multi-level trawl at 12 sites within the North Atlantic subtropical gyre to sample from the air-seawater interface to a depth of 5 m, at 0.5 m intervals. Our results show that plastic concentrations drop exponentially with water depth, and decay rates decrease with increasing Beaufort number. Furthermore, smaller pieces presented lower rise velocities and were more susceptible to vertical transport. This resulted in higher depth decays of plastic mass concentration (milligrams m −3 ) than numerical concentration (pieces m −3 ). Further multilevel sampling of plastics will improve our ability to predict at-sea plastic load, size distribution, drifting pattern, and impact on marine species and habitats.

Microplastics Baseline Surveys at the Water Surface and in Sediments of the North-East Atlantic

“…Microplastic abundance at the sea surface has been shown to vary with wind speed due to vertical mixing (Kukulka et al, 2012; Claessens et al (2011) and the findings in this study. Claessens et al, 2011 This study Reisser et al, 2015). Data from the eastern North Pacific suggest that the abundance of suspended plastic within 10-30 m of the sea surface averages two orders of magnitude less than that of surface (Ryan et al, 2009).…”

Microplastic in three urban estuaries, China

“…MP ingestion not only could pose physical impacts by internal abrasions and blockages, but also provide a possible pathway of exposure to the respective organisms via adsorbing organic contaminants and metals from the ambient environment. Due to being associated with most of the toxic pollutants listed by the United States Environmental Protection Agency and European Union, plastic waste is thought to be categorized as hazardous (Rochman et al, 2013).…”

Modeling the Fate and Distribution of Floating Litter Particles in the Aegean Sea (E. Mediterranean)

“…Once deposited into the oceans, plastics are gradually fragmented into smaller particles (< 5 mm), due to the synergistic effect of environmental variables and the inherent material instability, and this forms floating marine debris (Thompson et al, 2004;Pastorelli et al, 2014). Floating litter items are found in oceans around the world, such as in the Pacific ocean (Martinez et al, 2009;Law et al, 2014), the southeast Atlantic gyre (Ryan, 2014), the North Atlantic sub-tropical gyre (Reisser et al, 2015), and the Mediterranean Sea (Suaria and Aliani, 2014;Cózar et al, 2015).…”