Distribution patterns of microplastics in subtidal sediments from the Sado river estuary and the Arrábida marine park, Portugal

Abstract

Understanding local accumulation patterns of microplastics in subtidal sediments is crucial to assess how available such particles are for ingestion by benthic feeders and to identify the potential pollution sources in the region upon which is urgent to act. The coastal urban centers of Setúbal and Sesimbra (Portugal) and the multiple activities taking place at the contiguous Sado estuary and in the sheltered waters of Professor Luiz Saldanha Marine Park make this a relevant case study about MPs pollution in the seabed. Here, a short-term investigation assessed the spatiotemporal distribution, abundance, and composition of MPs on the nearshore seabed. Sediment samples were monthly collected from summer 2018 to winter 2019, in six stations. Despite the differences observed in rainfall between campaigns, no distinct patterns were detected in the accumulation of MPs throughout the sampled months. Yet, strong variations occurred among stations. The abundance of MPs in the Sado estuary (1042.8 ± 430.8 items kg−1) was higher in comparison to all the stations located along the marine park (52.9 ± 31.9 items kg−1). Fragments comprised 70% of particles found in estuarine sediments, while fibers were the predominant type in marine sediments. The majority of MPs collected in the estuary shared the same size class as the best represented grain size fraction: 0.250–0.500 mm. On average, the ratio between the abundance of MPs and the abundance of meiofauna organisms was higher in the estuary, suggesting more encounter rates, by both meiofauna and their predators, with MPs. The distribution of MPs throughout the study area was moderately correlated with sediment sorting and organic matter content. Also, the distinct mineralogical content of each station indicates a reduced sediment transit between stations and consequently a weak exportation of MPs from the estuary. The majority of the polymers identified by Fourier Transform Infrared Spectroscopy was denser than seawater. Polyethylene terephthalate represented 41% of the items analyzed and was mostly assigned to fibers and fiber bundles. Unveiling the distribution patterns of MPs along this segment of the Portuguese west coast enabled to identify a high-risk area where the implementation of preventive measures is urgent.

The geographical and seasonal effects on the composition of marine microplastic and its microbial communities: The case study of Israel and Portugal

“…The prevalence of PE, PP and PS polymers in Yarkon, is in line with reports from the Ionian, Aegean, and Levantine Seas (Adamopoulou et al, 2021), central Mediterranean Sea (Marrone et al, 2021) and other Mediterranean Sea studies (Suaria et al, 2016;Sharma et al, 2021). Similar to Yarkon, PE and PP polymers were also the most common in Sado, which agrees with studies in Arrábida and Setúbal (Rodrigues et al, 2022). The plastic polymer type is not considered a major factor that is affecting the plastisphere microbiome in the natural environment (Oberbeckmann et al, 2018;Laverty et al, 2020).…”

“…The high percentage of films documented in the winter (37.78%), can be explained by the faster degradation of plastic bags and packaging, which is considered their main source (Marrone et al, 2021). The same was observed for Sado, where fragments predominated during summer (63.49%) and winter (76.34%), which is in agreement with samples from the North East Atlantic (63%) and from Arrábida and Setúbal (Rodrigues et al, 2022).…”

“…These outliers in plastic concentrations may reflect patchiness in the distribution of plastic particles along the Israeli coast due to its Frontiers in 09 frontiersin.org unique geomorphology or local factors such as wind, swell, and currents causing its accumulation in specific areas. In Portugal, a recent study reported microplastic concentrations of 0.45 ± 0.52 particles m −3 in Arrábida and Setúbal coastal area (Rodrigues et al, 2022) that are proximal to Sado estuary. These concentrations are higher than those documented in our study near Sado estuary of 0.04 ± 0.02 particles m −3 and 0.08 ± 0.04 particles m −3 during summer and winter, respectively.…”

Approaches for Sampling and Sample Preparation for Microplastic Analysis in Laundry Effluents

“…The samples can be preserved by refrigeration, the use of a suitable sample container, or the addition of preservative chemicals [55]. The samples are usually stored in a refrigerator at 4 • C [56] or deepfrozen at below −20 • C [57] until they are analysed. In some cases, the identification and characterisation of the biological substance may be relevant for other aspects of the research, which is why different fixation solutions are used (70-80% ethanol [58] or 4-5% formalin [59]).…”

“…So far, the pore sizes used in different studies have not been standardised, so the amount of MPs found varies, making it impossible to compare the results (Figure 4). [86], [80], [87], [88], [89], [88], [57].…”