Sediment matters as a route of microplastic exposure: A call for more research on the benthic compartment

Abstract

Microplastics (MPs) are ubiquitous in the marine environment. Here, most MPs are expected to sink, either due to polymer density or environmental processes, such as biofouling, leading to sediment being proposed to act as a final sink for marine MPs. There is a discrepancy between the anticipated accumulation of MPs in the sediment compartment and the MP experiments conducted, since most MP effect studies have been conducted with pelagic species using water-only exposures. Here we address fundamental questions in relation to MP pollution to close the knowledge gap related hereto. A systematic literature search was performed to address these questions. We found that benthic invertebrates ingest MPs and that, even though these organisms evolutionary are adapted to handle particles, adverse effects may be observed upon ingestion of MPs. The analysis further revealed that there is a major knowledge gap on the impacts of sediment-associated MPs in marine, benthic invertebrates. To facilitate further and structured research within this topic, we recommend more studies with emphasis on the sediment as an important exposure pathway, and to focus on sediment-associated MP effects on benthic invertebrates. We recommend studies with ecological relevant exposure concentrations and ecological relevant exposure durations with emphasis on impacts on population- and community-level to reduce the knowledge gap within this central area of MP pollution research.

Microplastics in Freshwater Sediments Impact the Role of a Main Bioturbator in Ecosystem Functioning

“…Despite the global attempts to manage plastic waste, humanity is still far from confronting the plastic crisis. , Even with efforts to reduce plastic pollution, the amount of mismanaged plastic waste expected to be released in aquatic ecosystems by 2030 may reach 53 million metric tons (Mt), twice the amount estimated for 2016 . Microplastics (plastic particles ≤5 mm in size) are part of this plastic waste and are transported to the ocean via coastal runoff and river discharge. , Once in the river environment, depending on their density, microplastics can float in the water column or sink into sediment beds − where they can be temporarily trapped . Microplastic concentrations estimated in European riverbed sediments range from 18 up to 75000 particles kg –1 dry weight, , with the majority of particles detected being polyethylene, polypropylene, and polystyrene polymer types in a wide range of sizes and shapes (fragments, fibers, and spherical forms). ,, …”

When and How to Conduct Ecotoxicological Tests Using Natural Field‐Collected Sediment

“…Thus, only a few test guidelines focus on sediment exposure using artificially formulated (Organisation for Economic Co‐operation and Development [OECD], 2004, 2007, 2014), natural field‐collected (ASTM International, 1999; US Environmental Protection Agency [USEPA], 2001), or contaminated field‐collected sediments (OSPAR Commission, 2006; OECD, 2022; International Organization for Standardization, 2005). However, there is increasing awareness of the importance of studying the ecotoxicity of contaminated sediment, predominantly due to aquatic sediments acting as reservoirs accumulating and retaining a large variety of contaminants, for example, nanoparticles (NPs), metals, microplastics (MPs), and organic contaminants (Lehoux et al, 2020; Pavoni et al, 2021; Sandgaard, Palmqvist, et al, 2023). Once accumulated in the sediment, benthic organisms are exposed via ingestion of contaminated sediment and over their surface epithelia by direct contact with the sediment during burrowing, which may lead to contaminant bioaccumulation (Grabicova et al, 2015).…”

Detection of Secondary Microplastics in an Aquatic Mesocosm by Means of Object-Based Image Analysis

“…into the environment [13], transport (e.g., water discharge from land, atmospheric deposition, etc.) through the environment [14,15], accumulation in certain areas of the environment (e.g., bodies of water) [16], ingestion by organisms (e.g., plankton) in diverse environments [17], and sedimentation (e.g., marine benthos) [18] coupled with a less understood long-term fate [19,20].…”