Abstract
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. However, their abundance and distribution in the ocean are hardly known, strongly limiting an assessment of their global significance. As a consequence, marine gels are often disregarded in biogeochemical or ecosystem models. Here, we demonstrate the widespread abundance of microgels in the ocean, from the surface to the deep sea. 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 upwelling systems and c) the oligotrophic open ocean. We show the variations of TEP and CSP over the water-column, and compare them to dissolved organic carbon (DOC). We also discuss how the observed distributional patterns give potential insight to the productivity and particle dynamics of these distinct oceanic regimes. Finally, we exploit current research topics, where consideration of microgels may give new insight into the role of organic matter for marine biogeochemical processes.
Highlights
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
We show the vertical distribution of transparent exopolymer particles (TEP) and Coomassie stainable particles (CSP), and in comparison to dissolved organic carbon (DOC), from the surface to the deep sea
DOC distribution is driven by water mass transport and DOC concentration exhibits relatively little variability over time and space, in particular in the deeper water column where the majority of DOC is included in refractory compounds with turn-over times of more than 100 years (Hansell, 2002)
Summary
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. 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). 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 gels are defined as three-dimensional networks of organic polymers with seawater as solvent entrapped in the network pores. Nanogels assemble from individual polymers and are held together by ionic forces, such as divalent cation (Ca2+, Mg2+) bridging
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