Marine vs freshwater microalgae exopolymers as biosolutions to microplastics pollution

Abstract

Microalgae can excrete exopolymer substances (EPS) with a potential to form hetero-aggregates with microplastic particles. In this work, two freshwater (Microcystis panniformis and Scenedesmus sp.) and two marine (Tetraselmis sp. and Gloeocapsa sp.) EPS producing microalgae were exposed to different microplastics. In this study, the influence of the microplastic particles type, size and density in the production of EPS and hetero-aggregates potential was studied. Most microalgae contaminated with microplastics displayed a cell abundance decrease (of up to 42%) in the cultures. The results showed that the formed aggregates were composed of microalgae and EPS (homo-aggregates) or a combination of microalgae, EPS and microplastics (hetero-aggregates). The hetero-aggregation was dependent on the size and yield production of EPS, which was species specific. Microcystis panniformis and Scenedesmus sp. exhibited small EPS, with a higher propension to disaggregate, and consequently lower capabilities to aggregate microplastics. Tetraselmis sp. displayed a higher ability to aggregate both low and high-density microplastics, being partially limited by the size of the microplastics. Gloeocapsa sp. had an outstanding EPS production and presented excellent microplastic aggregation capabilities (adhered onto the surface and also incorporated into the EPS). The results highlight the potential of microalgae to produce EPS and flocculate microplastics, contributing to their vertical transport and consequent deposition. Thus, this work shows the potential of microalgae as biocompatible solutions to water microplastics treatment.

Biogenic Aggregation of Small Microplastics Alters Their Ingestion by a Common Freshwater Micro-Invertebrate

“…This conglomerate of plastics and biota is called "plastisphere" (Zettler et al, 2013;Kirstein et al, 2019;Amaral-Zettler et al, 2020). Moreover, extracellular polymeric substances (EPS), particularly transparent exopolymers particles (TEP), produced by microorganisms play a significant role in the formation of nano-and microplastic agglomerates (Cunha et al, 2019). These aggregated particles might be ingested by invertebrates having low feeding selectivity, such as filter-feeders (Scherer et al, 2017).…”

<em> </em>Current Research on Microbe-Plastic Interactions in the Marine Environment

“…The effects of interactions between biogenic material (such as marine snow 310 and marine microalgae 77,91,103,116 ) and very small, sub-millimetre microplastics (down to 2 µm) have in fact been investigated in a number of laboratory studies. These studies, however, have either focussed on heteroaggregation 38,77,91,103,116 , rather than the colonisation of individual microplastic particles or polymers that are denser than seawater 38 (and would therefore readily sink in the marine environment even without biofouling).…”

Database with pollution sources and impact assessment in Bega and Timis River basins

“…Industrial activities are the largest and main source of water pollution due to the generation of effluents with distinct characteristics. Pollutants commonly found in water include pesticides, organic contaminants, metals, nitrogen compounds and sometimes-even radionuclides [6][7][8][9]. Moreover, water can contain many disease-causing organisms, such as bacteria, viruses, and parasites, which must be removed or inactivated for the human safety [3].…”