Are litter, plastic and microplastic quantities increasing in the ocean?

Abstract

Whilst both plastic production and inputs at sea have increased since the 1950s, several modelling studies predict a further increase in the coming years in these respective quantities. We compiled scientific literature on trends in marine litter, consisting largely of plastic and microplastics in the ocean, understanding that monitoring programs or assessments for these aspects are varied, frequently focusing on limited components of the marine environment in different locations, and covering a wide spectrum of marine litter types, with limited standardization. Here we discuss how trends in the amounts of litter in the marine environment can be compared with the information provided by models. Increasing amounts of plastic are found in some regions, especially in remote areas, but many repeated surveys and monitoring efforts have failed to demonstrate any consistent real temporal trend. An observed steady state situation of plastic quantities in many marine compartments and the fate and transport of plastic in the marine environment remain areas for much needed further research.

A multilevel dataset of microplastic abundance in the world’s upper ocean and the Laurentian Great Lakes

“…Level 0 -raw data Data from 27 research projects conducted during the period from 2000 through 2019 (Table 1) were used to create the Level-0 data on pelagic microplastic abundance in the world's oceans and the Laurentian Great Lakes. We synthesized the data collected during the past 20 years to represent the 'current status' of microplastic abundance, because a long-term trend is undetectable in such a short period, as shown by Law et al [26], who provided a time series of plastic-debris abundance from 1986 to 2008, and because long term change is not a common scheme for floating plastics and microplastics [11,26,[33][34][35]. In total, 23 of the 27 projects collected microplastics only by surface net towing, but Projects #13 and #26 (Table 1) collected data via continuous seawater intake at a depth of 3 m (#12 partly included seawater intake; Table 1): Nonetheless, the target of these two projects was microplastics over several tens of μm in size (see 'Mesh size' in Table 1).…”

Monitoring Plastic Beach Litter by Number or by Weight: The Implications of Fragmentation

“…Recently, Galgani et al (2021) have pointed out that despite the growing number of global time series from beach, floating and seabed plastic litter monitoring, there are currently few discernible trends in the plastic content of the sea, possibly suggesting a steady state between inputs and removals. In order to close the budgets of global marine plastic more accurately, many aspects of marine plastic science need to be improved, including better knowledge of all marine plastic sources and sinks, and Galgani et al (2021) point out the considerable challenges involved.…”

“…Recently, Galgani et al (2021) have pointed out that despite the growing number of global time series from beach, floating and seabed plastic litter monitoring, there are currently few discernible trends in the plastic content of the sea, possibly suggesting a steady state between inputs and removals. In order to close the budgets of global marine plastic more accurately, many aspects of marine plastic science need to be improved, including better knowledge of all marine plastic sources and sinks, and Galgani et al (2021) point out the considerable challenges involved. This paper addresses three aspects requiring improvement; an understanding of how large plastic breaks down into small plastic items (i.e., fragmentation), knowledge of the weights of plastic litter items in the sea, and the standardization of monitoring programs so that data around the world can be compared and merged (e.g., Carvalho et al, 2021).…”

Editorial: Microplastics in the Marine Environment: Sources, Distribution, Biological Effects and Socio-Economic Impacts

“…Manuscripts in this RT aim at fulfilling knowledge gaps while creating new research questions to fully understand the ubiquitousness of plastics in the environment. Although there is still a long way to go within this research extensive knowledge gathered so far [see for example Galgani et al (2021)] will allow decision makers to make better decisions surrounding this global problem, while consolidating microplastic pollution as a permanent research field.…”