The origin of the polysaccharides contributing to TEP formation is biological production, mainly primary production by plankton in the sunlit surface ocean. Today, most published information on gels in the marine environment is available for TEP and CSP. After staining, TEP and CSP can be quantified by spectrophotometric measurements of the total amount of stain absorbed ( Passow and Alldredge, 1995 Cisternas-Novoa et al., 2014) or by sizing and counting of individual particles using microscopy (e.g., Engel, 2009). It is used for identifying protein-containing Coomassie stainable particles (CSP) ( Long and Azam, 1996). Another dye is Coomassie Brilliant Blue, a disulfonated triphenylmethane dye that binds to proteins and longer peptides ( Chial and Splittgerber, 1993). Alcian Blue, a cationic copper-phthalocyanine dye that reacts with the carboxyl (COO –) and sulfate half ester ( OSO 3 -) functional groups of acid mucopolysaccharides and glycosaminoglycans ( Parker and Diboll, 1966 Decho, 1990) and the fluorescein labeled lectin Concanavalin A (ConA) have been used to determine polysaccharide-containing gels, referred to as transparent exopolymer particles (TEP) ( Alldredge et al., 1993 Engel et al., 2017). Gel particles in seawater have been determined through staining with dyes specific for the organic compounds they contain. In the reverse, processes like fragmentation and dispersions are responsible for gel size reduction. More stable and larger sized polymer gels result from collisions of two annealing nanogels. According to this theory, gel growth is achieved through annealing of small nanogels that can create larger sized gels (~5 μm) ( Chin et al., 1998). Nanogels assemble from individual polymers and are held together by ionic forces, such as divalent cation (Ca 2+, Mg 2+) bridging and hydrogen bondings, or by hydrophobic interactions. Here, marine gels are defined as three-dimensional networks of organic polymers with seawater as solvent entrapped in the network pores. A useful concept to describe the structure and properties of gels comes from gelation theory ( Chin et al., 1998 Verdugo et al., 2004 Verdugo, 2012 Orellana and Leck, 2015). The large and continuous size spectrum of marine gels is the result of dynamic formation and disintegration processes that yet are not fully understood. Marine EPSs typically have a high content of gelling agents, such as mucopolysaccharides and they occur over a large range of sizes in various chemical and structural forms ( Verdugo et al., 2004). Gels are a fraction of exopolymeric substances (EPS), representing dissolved or particulate polymeric organic substances outside the cell. Natural organic gels have gained considerable attention in marine and atmospheric research over the past decades due to their widespread occurrence in the environment and their involvement in biological, chemical, and physical processes. Finally, we exploit current research topics, where consideration of microgels may give new insight into the role of organic matter for marine biogeochemical processes. We also discuss how the observed distributional patterns inform about productivity and particle dynamics of these distinct oceanic regimes. We show the variations of TEP and CSP over the water-column, and compare them to dissolved organic carbon (DOC). We exhibit size spectra of two major classes of marine gels, transparent exopolymer particles (TEP) and Coomassie stainable particles (CSP) for three different ocean regimes: (a) Polar Seas, (b) Eastern Boundary Upwelling Systems, and (c) the oligotrophic open ocean. Here, we demonstrate the widespread abundance of microgels in the ocean, from the surface to the deep sea. As a consequence, marine gels are often disregarded in biogeochemical or ecosystem models. However, their abundance and distribution in the ocean are hardly known, strongly limiting an assessment of their global significance. Three-dimensional hydrogels of organic polymers have been suggested to affect a variety of processes in the ocean, including element cycling, microbial ecology, food-web dynamics, and air-sea exchange. 4Department of Biotechnology, Chemistry and Pharmacy, University of Siena, Siena, Italy.3Center for Colloid and Surface Science, Sesto Fiorentino, Italy. 2WTSH Business Development and Technology Transfer Corporation of Schleswig-Holstein, Kiel, Germany.1GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany.Anja Engel 1*, Sonja Endres 1,2, Luisa Galgani 3,4 and Markus Schartau 1
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |