Distribution Patterns of Floating Microplastics in Open and Coastal Waters of the Eastern Mediterranean Sea (Ionian, Aegean, and Levantine Seas)

Abstract

Microplastic pollution is a pervasive anthropogenic phenomenon at the ocean surface. Numerous studies have been performed worldwide; nevertheless, the distribution patterns, morphological properties, and sources of origin in the Eastern Mediterranean Sea are still poorly explored. The purpose of this study is to investigate the distribution patterns of surface floating microplastics (MPs) in the Ionian, Aegean, and Levantine Seas in relation to their sources and sea surface circulation. In total, eighty-four samples were collected using manta nets from 2014 to 2020, covering open waters, coastal waters, and enclosed gulfs (Corfu and Saronikos). MPs concentration measurements revealed high variability ranging from 0.012 to 1.62 items m–2 and did not present maximum concentrations close to MPs hotspot areas. The presence of sea surface slicks, as recorded visually during our samplings, seems to play a key role on the distribution pattern of MPs, and highest concentrations were recorded in samples affected by these formations. The dominant MPs shape type identified were fragments (50–60%), whilst filaments (1–23%), films (3–26%), and foams (0–34%) varied among the studied areas. The majority of MPs in open waters had sizes ≤2 mm peaking between 0.6 and 1.4 mm. Spectroscopic analysis of MPs revealed the presence of 11 polymer types in both open sea and gulfs; the most abundant type was polyethylene (PE), followed by polypropylene (PP), and polystyrene (PS). The relative abundance of polymer types was more diverse in Saronikos Gulf, compared to the open sea due to the proximity to major urban and industrial sources. Our findings suggest that the vicinity to coastal population centers determined the properties, size and polymer types of MPs and highlight that MPs concentrations are affected significantly by local oceanographic conditions, such as surface slicks.

Microplastics in the Mediterranean: Variability From Observations and Model Analysis

“…All of them were characterized for their shape and size (Figure 12). The majority of particles found were characterized as fragments that result to be the dominant shape independently of seasonal campaign and sampling area, in agreement with several studies on MPs, collected in similar regions of the Mediterranean, including the Ligurian Sea, Gulf of Lion, Gabes, and Saronikos Gulf (Fossi et al, 2017;Schmidt et al, 2018;Tziourrou et al, 2019;Zayen et al, 2020;Adamopoulou et al, 2021). The high prevalence of fragments in surface water suggests that the microplastics derived from degradation of waste, originating from population activities, especially in proximity of densely populated coastal areas, either through rivers or landfills (Collignon et al, 2012;Pedrotti et al, 2016;Schmidt et al, 2018;Simon-Sánchez et al, 2022).…”

“…The MPs abundance (mean = 0.8 × 10 5 items/km 2 during spring 2019 and 4.7 × 10 4 items/km 2 during autumn 2019), obtained from sampling in Saronikos Gulf, fall in the same range with outputs from campaigns during 2015 and 2016 (3.5 × 10 2 items/km 2 -9.2 × 10 5 items/km 2 ) (Adamopoulou et al, 2021). Interestingly, in the latter study, the maximum MPs concentration for the Aegean and Ionian Seas was not found in areas in the proximity of the anthropogenic sources, suggesting that the relationship between them is not easily predictable.…”

“…Thus, these particles were included in the final MPs abundance. Paint particles represent a significant fraction of MPs pollution in Saronikos Gulf, being recently documented (Adamopoulou et al, 2021;Gaylarde et al, 2021). Indeed, it has been recently accepted by the International Union for the Conservation of Nature (IUCN) that ships' hull scrapings, marine coatings and anti-fouling systems are potential sources of marine MPs pollution (IMO, 2019).…”

“…When buoyant plastics enter the ocean, their fate is determined not only by their physical properties (e.g., density, size, and shape) and processes in the marine environment (wind, waves, and ocean currents), but also by processes related to the MP itself, including aggregation with other particles (Long et al, 2015), biofouling (Fazey and Ryan, 2016;Kooi et al, 2017) and degradation into smaller particles (Eriksen et al, 2014;Gewert et al, 2015;Song et al, 2017;Kvale et al, 2020). The interplay of such different factors may contribute to the accumulation of MPs in an open sea or coastal area (Desforges et al, 2014;Fauziah et al, 2015;Brach et al, 2018;Adamopoulou et al, 2021). Numerical models simulating the movement and fate of marine litter provide essential tools to gain a better understanding and predict accumulation areas of plastic debris (NOAA, 2016).…”

Spatiotemporal Variability of Microplastics in the Eastern Baltic Sea

“…Next, we compare our findings with previous 2017) measured 0.19-7.73 counts/m 3 in the Stockholm Archipelago, and 0-0.8 counts/m 3 were found in the GOF (Setälä et al, 2016). In the Arctic waters, Lusher et al (2015) revealed MP concentrations of 0-1.31 counts/m 3 , 0.07-9.25 counts/ m 3 were measured in the Eastern Mediterranean Sea (Adamopoulou et al, 2021), 1.82 counts/m 3 were observed in the Mediterranean Sea (Zeri et al, 2018), and 0.06-25.9 counts/m 3 were found in the Eastern Indian Ocean (Li et al, 2021).…”