Transparent exopolymer particle (TEP) dynamics in the eastern Mediterranean Sea

Abstract

Depth and spatial distribution patterns of transparent exopolymer particles (TEP) were measured during 2 east to west cruise transects across the ultra-oligotrophic Levantine basin, eastern Mediterranean Sea (SESAME, September 2008; ISRLEV, July 2009), and at 2 stations 20 and 50 km offshore (2008). TEP distribution was examined relative to chlorophyll a concentrations, bacterial production, and alkaline phosphatase activity (APA), taken as a measure of phosphorus (P) stress. During the stratified period, TEP levels were highest in a 5 m surface layer and correlated positively with APA as P concentrations decreased. On the transects, TEP concentrations from both surface and depth (1000 m) samples increased from west to east, corresponding to a pattern of increasing oligotrophy. In pelagic waters, maximal rates of bacterial production and TEP concentrations were consistently measured in surface samples. These contained abundant large (170 µm) TEP with numerous associated bacteria, possibly derived from algal or bacterial release or detritus. Lowest TEP concentrations were found in the deep chlorophyll maximum layer where TEP appeared as small (~4 µm) particles with only few attached bacteria. In deeper (300 to 1000 m) samples, both TEP concentrations and size increased, with most particles having associated bacteria. Our data augment previous studies on the formation of TEP and the subsequent utilization of this material by heterotrophic bacteria both in the euphotic zone and in deeper waters. Moreover, our study suggests that in ultra-oligotrophic environments such as the Levantine basin, TEP plays an especially important role in carbon cycling and transportation.

Revised paradigm of aquatic biofilm formation facilitated by microgel transparent exopolymer particles

“…Although only a relatively small fraction (26-47%) of Alcian Blue-staining particles was retained by the GF/F filters, this treatment appeared to effectively remove most of the protobiofilm and larger TEPs (see below). The concentration of TEPs in the untreated seawater used in the third experiment was much lower than in the previous experiments but normal [194 ± 7 μg gum xanthan (GX) L −1 ] for winter coastal waters in this area (2).…”

“…The results of this and previous studies (2,21,22) lead us to propose a revised paradigm for aquatic biofilm formation that takes into account the previously unrecognized role of microgel particles such as TEPs and protobiofilm in facilitating and accelerating this process (Fig. 6).…”

“…Since first described by Alldredge et al (1), the ubiquity and multiple ecosystem functions of TEPs have been extensively documented in the oceanographic and limnological literature (2,3).…”

“…Recently, TEPs have been implicated as an important factor in the development of aquatic biofilm (2,14,15). Like the extracellular polymeric substances (EPSs) that form the matrix of microbial biofilms, these microgel particles are partly composed of polysaccharides with highly surface-active polymers of fucose and rhamnose (16).…”

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

“…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).…”