Abstract
Plastic debris is a widespread contaminant, prevalent in aquatic ecosystems across the globe. Zooplankton readily ingest microscopic plastic (microplastic, < 1 mm), which are later egested within their faecal pellets. These pellets are a source of food for marine organisms, and contribute to the oceanic vertical flux of particulate organic matter as part of the biological pump. The effects of microplastics on faecal pellet properties are currently unknown. Here we test the hypotheses that (1) faecal pellets are a vector for transport of microplastics, (2) polystyrene microplastics can alter the properties and sinking rates of zooplankton egests and, (3) faecal pellets can facilitate the transfer of plastics to coprophagous biota. Following exposure to 20.6 μm polystyrene microplastics (1000 microplastics mL(-1)) and natural prey (∼1650 algae mL(-1)) the copepod Calanus helgolandicus egested faecal pellets with significantly (P < 0.001) reduced densities, a 2.25-fold reduction in sinking rates, and a higher propensity for fragmentation. We further show that microplastics, encapsulated within egests of the copepod Centropages typicus, could be transferred to C. helgolandicus via coprophagy. Our results support the proposal that sinking faecal matter represents a mechanism by which floating plastics can be vertically transported away from surface waters.
Highlights
Consumption of plastic debris by marine organisms is commonplace,[4] with studies identifying microplastics in the intestinal tracts of 25−28% of fish and 33% of shellfish sold at markets in the U.S and Indonesia,16 83% of the crustacea Nephrops norvegicus sampled from the Clyde Sea (U.K.), and approximately 3% of the copepod Neocalanus cristatus and 6% of the euphausid Euphasia pacif ica sampled in the NE Pacific.[17]
Our results demonstrate for the first time that microplastics can significantly alter the structural integrity, density, and sinking rates of faecal pellets egested by marine zooplankton
We identified that copepods readily ingested and egested microplastics, which is consistent with previous findings.[21,31]
Summary
Plastic debris is a pervasive anthropogenic contaminant, identified in marine ecosystems across the globe.[1,2] In recent years, there has been growing concern that microscopic plastic (microplastic, < 1 mm diameter) debris could pose a threat to aquatic life, marine ecosystems, and human health.[3−5] Microplastics include consumer items manufactured to be of a microscopic size (e.g., exfoliates in personal care products),[6] or derive from the biological-, photo-, and/or mechanical degradation and subsequent fragmentation of larger plastic.[7]Marine plastic debris stems from both terrestrial and maritime sources,[8] and owing to its environmental persistence and buoyancy can be transported vast distances upon oceanic currents, affecting remote ecosystems including Arctic waters, deep-sea habitats, and midoceanic gyres.[9−12] Recently Eriksen et al estimated there are over 5 trillion microplastics floating in the ocean.[2]. Plastic debris is a pervasive anthropogenic contaminant, identified in marine ecosystems across the globe.[1,2] In recent years, there has been growing concern that microscopic plastic (microplastic, < 1 mm diameter) debris could pose a threat to aquatic life, marine ecosystems, and human health.[3−5] Microplastics include consumer items manufactured to be of a microscopic size (e.g., exfoliates in personal care products),[6] or derive from the biological-, photo-, and/or mechanical degradation and subsequent fragmentation of larger plastic.[7]. Laboratory-based, toxicological studies have identified that microplastic ingestion can lead to adverse health effects in a number of marine organisms, including: heightened immunological response in mussels;[18] a reduction in the energetic reserves and bioturbation activity of polychaete worms;[19] hepatic toxicity in fish;[20] and reduced feeding, fecundity, and survival in marine copepods.[21,22] a number of studies have suggested that some larval organisms with more simplistic intestinal tracts, including oyster larvae[23] and sea urchin larvae,[24] demonstrate
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