Biofilm Formation Influences the Wettability and Settling of Microplastics

Abstract

The fate of 99% of the plastics present in oceans is unknown. It is presumed that biofilm formation on plastics leads to their sinking to the ocean floor, thus making them undetectable at the surface. While it is established that biofilms lead to sinking of plastics, it is the mechanism by which biofilms enhance the vertical transport of plastics that remains unknown. It is commonly assumed that biofilms increase the effective mass density of the plastics, which drives their sinking. Here, we show that such an assumption is not always true, and formation of biofilms alone is an insufficient criterion to predict the sinking or floating of plastics. We study the biofilm formation and vertical transport of polyethylene microplastics in the presence of Alcanivorax borkumensis, Anabaena sp., and Synechococcus elongatus. We find that while all three microorganisms formed biofilms on microplastics, only Alcanivorax led to their sinking. The sinking of microplastics is attributed to the production of highly active biosurfactants by Alcanivorax and its adsorption onto microplastics, which is not the case for Anabaena and Synechococcus. Our study highlights that it is not only the formation but the properties of the formed biofilms that govern the sinking or floating of plastics.

Chitosan-Coated Lignin Nanoparticles Enhance Adsorption and Proliferation of Alcanivorax borkumensis at the Hexadecane–Water Interface

“…A. borkumensis is known to produce biofilms (Figure S5) and biosurfactants that assist in emulsifying oil into the water column, but at this time, there is no direct method to quantify these biosurfactants. , Because the oil–water interfacial area is a significant growth-limiting factor, emulsions formed by the NPs and A. borkumensis were also characterized.…”

Quantification of the Emission of Atmospheric Microplastics and Nanoplastics via Sea Spray

“…While the parametrization reported in this study helps to further constrain the oceanic source of atmospheric MNP, it is important to recognize that it is rudimentary in nature, considering solely pristine spherical PS and PE MNP, which are not particularly representative of the complex mixture of MNP found in the environment . Additional research is warranted to investigate how other MNP sizes, materials, and morphologies, as well as changes in surface properties due to ultraviolet aging and bioaccumulation, , affect their aerosolization via sea spray. , …”

Field based studies on aging characteristics of pristine and aged plastic debris in a coastal environment, Bohai Bay, China

“…24 However, due to temperature reduction and changes in environmental factors such as microbial products, defouling activities might occur on the surface of plastic debris, resulting in a decrease in density. 24,33 In addition, the movement of plastic debris is not only caused by the movement of plastic debris itself, but is also driven by ocean currents. 24 As for the changes in physicochemical properties (including the functional groups, hydrophobicity, and crystallinity), the plastic samples all changed significantly in the early stage (2–4 weeks) after they were placed in a coastal environment but they did not change much in the later stage.…”