Microplastics increase the marine production of particulate forms of organic matter

Abstract

Microplastics are a major environmental challenge, being ubiquitous and persistent as to represent a new component in all marine environments. As any biogenic particle, microplastics provide surfaces for microbial growth and biofilm production, which largely consists of carbohydrates and proteins. Biofilms influence microbial activity and modify particle buoyancy, and therefore control the fate of microplastics at sea. In a simulated 'plastic ocean', three mesocosms containing oligotrophic seawater were amended with polystyrene microbeads and compared to three control mesocosms. The evolution of organic matter, microbial communities and nutrient concentrations was monitored over 12 days. The results indicated that microplastics increased the production of organic carbon and its aggregation into gel particulates. The observed increase of gel-like organics has implications on the marine biological pump as well as the transport of microplastics in the ocean.

Marvelous Marine Microgels: On the Distribution and Impact of Gel-Like Particles in the Oceanic Water-Column

“…Microscopic plastic fragments and fibers, another recently recognized threat to the environment, are widespread in the oceans and have accumulated in the pelagic zone and sedimentary habitats. Due to their stickiness, gel particles may easily attach on such artificial particles (Michels et al, 2018) and the amount of both TEP and CSP increases in their presence (Galgani et al, 2019). Depending on plastic sizes, material, aging and shape, gel particles act as an accelerator for up-or downward transport of organic matter in the water column, modifying plastic particles buoyancy and bioavailability (Galloway et al, 2017) with potential consequences for global carbon sequestration and turnover.…”

Algal growth at environmentally relevant concentrations of suspended solids: implications for microplastic hazard assessment

“…Recently, the latter effects have been suggested to occur in the algae exposed to microplastic; moreover, increased production of organic carbon and its aggregation into gel particulates have been demonstrated in mesocosms amended with polystyrene microbeads (Galgani et al, 2019). It is, therefore, crucial to understand whether algae-plastic aggregates have a higher capacity to inhibit growth compared to the aggregates with natural solids.…”

Algal Growth at Environmentally Relevant Concentrations of Suspended Solids: Implications for Microplastic Hazard Assessment

“…The mechanisms of the growth inhibition in the presence of suspended solids, including microplastic, may vary, including shading effects and trapping of microalgae in the aggregates and subsequent inhibition of photosynthesis (He et al, 2017;Mao et al, 2018). Recently, such effects have been suggested to occur in the algae exposed to microplastic; moreover, increased production of organic carbon and its aggregation into gel particulates have been demonstrated in mesocosms amended with polystyrene microbeads (Galgani et al, 2019). Therefore, it is crucial to understand whether algae-microplastic aggregates have a higher capacity to inhibit growth compared to the aggregates with natural solids.…”