Marine Gel Interactions with Hydrophilic and Hydrophobic Pollutants

Abstract

Microgels play critical roles in a variety of processes in the ocean, including element cycling, particle interactions, microbial ecology, food web dynamics, air–sea exchange, and pollutant distribution and transport. Exopolymeric substances (EPS) from various marine microbes are one of the major sources for marine microgels. Due to their amphiphilic nature, many types of pollutants, especially hydrophobic ones, have been found to preferentially associate with marine microgels. The interactions between pollutants and microgels can significantly impact the transport, sedimentation, distribution, and the ultimate fate of these pollutants in the ocean. This review on marine gels focuses on the discussion of the interactions between gel-forming EPS and pollutants, such as oil and other hydrophobic pollutants, nanoparticles, and metal ions.

From Nano-Gels to Marine Snow: A Synthesis of Gel Formation Processes and Modeling Efforts Involved with Particle Flux in the Ocean

“…Even though the bulk P/C ratios that are used as a proxy for the stickiness of biopolymers that are mainly comprised of the two major components (proteins and carbohydrates) [37,88,97], one still needs to take the individual monosaccharides or amino acid composition (i.e., individual species and their relative abundances) into account for more accurate analysis of the relative hydrophobicity/hydrophilicity of the biopolymers. For example, at neutral pH (6.8), acidic carbohydrates (i.e., glucuronic acid) are negatively charged while amino sugars like glucosamine are positively charged, which results in opposite electrostatic interactions.…”

“…This includes but is not limited to engineered nanoparticles (e.g., [25,26]), oil spills and dispersants (e.g., [27][28][29][30]), and nano-and micro-plastics (e.g., [31][32][33][34]). In the recent literature, we often now see reference to marine oil snow (MOS; [29,35]) and marine plastic snow (MPS; [36,37]) reflecting the increased awareness and studies in this important arena. This review is not intended to be comprehensive but rather a synthesis of studies across a variety of fields.…”

Marine Biopolymer Dynamics, Gel Formation, and Carbon Cycling in the Ocean

“…After 12 h of UV-cracking chain size must decrease sufficiently as to prevent self-assembly and gel formation. To address previous and recent unwarranted criticisms [ 65 , 66 ], notice that in these experiments the radiated species were not gels, but freshly 0.2 μm-filtered DOM polymers that were subsequently allowed to self assemble, in absence of UV light.…”

Effect of Culture pH on Properties of Exopolymeric Substances from Synechococcus PCC7942: Implications for Carbonate Precipitation

“…Constituents making up microbial EPS include polysaccharides, proteins, nucleic acids, and lipids [29,35,36], with polysaccharides and proteins typically accounting for ~75-90% [37]. The molecular size of EPS ranges from 0.5 to >100 kDa [29], and the hydrophobicity, amphiphilicity, and intermolecular hydrogen bonds determine the colloidal density and dimensions of the polymeric matrix [37][38][39], which in turn depend on the properties (pH, ionic strength) of the solvent [39,40]. EPS interact with their environment through electrostatic and ionic forces, hydrophobic interactions, hydrogen bonds, and covalent crosslinking [33,38].…”