Bacterial Colonization and Vertical Distribution of Marine Gel Particles (TEP and CSP) in the Arctic Fram Strait

Abstract

Gel particles-a class of abundant transparent organic particles-have increasingly gathered attention in marine research. Field studies on the bacterial colonization of marine gels however are still scarce. So far, most studies on respective particles have focused on the upper ocean, while little is known on their occurrence in the deep sea. Here, we report on the vertical distribution of the two most common gel particle types, which are polysaccharide-containing transparent exopolymer particles (TEP) and proteinaceous Coomassie stainable particles (CSP), as well as numbers of bacteria attached to gel particles throughout the water column, from the surface ocean down to the bathypelagial (< 3,000 m). Our study was conducted in the Arctic Fram Strait during northern hemispheres' summer in 2015. Besides data on the bacterial colonization of the two gel particle types (TEP and CSP), we present bacterial densities on different gel particle size classes according to 12 different sampling depths at four sampling locations. Gel particles were frequently abundant at all sampled depths, and their concentrations decreased from the euphotic zone to the dark ocean. They were colonized by bacteria at all sampled water depths with risen importance at the deepest water layers, where fractions of bacteria attached to gel particles (%) increased within the total bacterial community. Due to the omnipresent bacterial colonization of gel particles at all sampled depths in our study, we presume that euphotic production of this type of organic matter may affect microbial species distribution within the whole water column in the Fram Strait, down to the deep sea. Our results raise the question if changes in the bacterial community composition and functioning on gel particles occur over depth, which may affect microbial respiration and remineralization rates of respective particles in different water layers.

Transparent exopolymer particles (TEP) in the deep ocean: full-depth distribution patterns and contribution to the organic carbon pool

“…Largely different prokaryote-TEP relationships between the upper and deep oceans under- score the complexity of interactions between TEP and prokaryotes. Prokaryotes can be a source of TEP as well as consumers (decomposers) of TEP and TEP precursors (Yamada et al 2013, Busch et al 2017. The prokaryotic parameters−TEP relationship may be the net outcome of opposing (i.e.…”

“…In the Mediterranean Sea, the TEP concentration was higher in deep waters (300−1000 m) than in the subsurface chlorophyll maximum layer, where most TEP were associated with prokaryotic cells (Bar-Zeev et al 2011). A recent study conducted in the Arctic Fram Strait also revealed that TEP in meso-and bathypelagic waters were colonized by prokaryotes, with densities (cell abundance per unit area of TEP) similar to those in upper waters (Busch et al 2017). This evidence suggests that TEP are potentially a significant component of the POC pool and can provide organic carbon substrates for microbial consumption in deep waters.…”

“…However, our current knowledge of TEP distribution and dynamics is mostly based on information obtained in the upper oceans (Passow 2002, Orellana & Leck 2014, Mari et al 2017. Only a few studies have investigated TEP distribution in the deep ocean (Bar-Zeev et al 2011, Wurl et al 2011, Cisternas-Novoa et al 2015, Busch et al 2017). In the subtropical North Pacific (maximum depth, 4580 m), TEP were found throughout the water column with concentrations that varied little over depth (Cisternas-N ovoa et al 2015).…”

Rising bubbles enhance the gelatinous nature of the air–sea interface

“…Whereas it is most likely that all TEP aggregates are colonized to some extent by bacteria, some studies reported that up to 68% of total bacterial cells found in water were attached to EPS (Mari and Kiorboe 1996). A recent study suggests that this might have implications for the transport of bacterial communities between different waterbodies (Busch et al 2017). During aggregation, heterotrophic bacteria may change TEP quantity and composition by extracellular enzyme activities (Smith et al 1995) and/or uptake of TEP microgels (Taylor and Cunliffe 2017).…”

Identification of Bacterial Genes Expressed During Diatom-Bacteria Interactions Using an in Vivo Expression Technology Approach

“…These colonization processes have been studied intensively (Grossart et al, 2006b;Thiele et al, 2015;Busch et al, 2017). Interactions of bacteria with microalgae or detritus will result in a series of biochemical or physical events, which change the characteristics of the colonized particle, let it grow or shrink in size, and alter its density, porosity, stickiness, and sinking velocity (Alldredge and Youngbluth, 1985;Alldredge et al, 1986;Biddanda and Pomeroy, 1988;Kiørboe and Jackson, 2001;Kiørboe et al, 2002).…”