Transparent exopolymer particles (TEP) link phytoplankton and bacterial production in the Gulf of Aqaba

Abstract

Variations in transparent exopolymer particles (TEP), bacterial biomass production (BP) and primary productivity (PP) were followed over 52 h at a deep water station in the Gulf of Aqaba (Eilat, Israel) during the spring, in April 2008. About 20 h after the start of the study, there was a short (~15 h) but intense storm event that probably caused a nutrient pulse and, subsequently, a brief outgrowth of diatoms in the euphotic layer. Concentrations of TEP and BP ranged from 23 to 228 µg gum xanthan equivalents l -1 and from 0.2 to 0.6 µg C l -1 h -1, respectively. Concentrations of TEP and BP were measured in unfiltered and in GF/C (1.2 µm)-prefiltered samples. Most of the TEP (59 ± 21% of total TEP, mean ± SD) were in the smaller (GF/C-filtered) size fraction (0.4-1.2 µm); however, after the crash of the diatom bloom, the majority of TEP were in the >1.2 µm size fraction. In the GF/Cfiltered fraction, BP averaged 59 ± 12% and 93 ± 5% of total BP in the upper water column and from 300 m, respectively. Significant correlations were observed between TEP and BP, suggesting that active heterotrophic bacteria may have been associated with these particles. During the 3 d of our study, PP and BP in the euphotic zone averaged 480 and 225 mg C m -2 d -1 , respectively, suggesting that about half or more of the primary produced carbon was metabolized by heterotrophic bacteria in the upper water column. Coincident with strong mixing caused by the storm, TEP concentrations decreased in the surface water and increased at depth. We suggest that TEP acted to link carbon flux between the primary producers and heterotrophic bacteria, and that the downward movement of TEP from the upper water layers may be an important process in transferring organic carbon to deeper waters of the Gulf of Aquaba. Sinking TEP could provide not only organic carbon substrates for associated bacteria but also form 'hot spots' of elevated microbial metabolism and nutrient cycling throughout the water column.

Potential terrestrial influence on transparent exopolymer particle concentrations in boreal freshwaters

“…The occurrence and formation of TEP depend on several environmental parameters (e.g., turbulence, multivalent cation concentrations, pH) and on the concentrations of precursors present (Kloareg and Quatrano ; Engel and Passow ). Higher TEP fluxes are frequently associated with peaks of particle fluxes to sediments in marine (Passow et al ; Bar‐Zeev et al ) and inland (de Vicente et al ) waters. For example, TEP contributed with up to 30% to the carbon export to the sediment in an oligotrophic reservoir in Spain (de Vicente et al ).…”

Azotobacter vinelandiisiderophore can provide nitrogen to support the culture of the green algaeNeochloris oleoabundansandScenedesmussp. BA032

“…Because the sugar provided to support A. vinelandii is an external source, this relationship is currently an open‐loop system. However, many strains of algae and cyanobacteria are known to produce extracellular reduced carbon compounds that could support the growth of A. vinelandii (Brechignac & Schiller, ; Wolf, ; De Philippis & Vincenzini, ; Corzo et al ., ; Bar‐Zeev et al ., ) and could be used as a secondary selection pressure. Under such conditions, the two strains could be grown in such a manner that a symbiotic relationship might evolve.…”

“…Each data point represents the average and standard deviation from three independent samples. carbon compounds that could support the growth of A. vinelandii (Brechignac & Schiller, 1992;Wolf, 1997;De Philippis & Vincenzini, 1998;Corzo et al, 2000;Bar-Zeev et al, 2009) and could be used as a secondary selection pressure. Under such conditions, the two strains could be grown in such a manner that a symbiotic relationship might evolve.…”

“…Under such conditions, the two strains could be grown in such a manner that a symbiotic relationship might evolve. Examples of phototrophs producing extracellular carbon that is released to the environment in the form of polysaccharides and simple sugars are common, although the exact reason for the energetically wasteful excretion of extracellular reduced carbon is not clear (Passow, 2002;Bar-Zeev et al, 2009). This research provides clear evidence that the nitrogen released to the environment as siderophores can be utilized by other organisms not only for obtaining metals from the environment (D'Onofrio et al, 2010), but also to provide requisite nitrogen required for growth and replication in some strains of green algae.…”

Role of Transparent Exopolymer Particles on Phytoplankton Dynamics in a Subtropical Estuary, Cananéia-Iguape (Sp, Brazil)

“…In this way, loss of TEP-derived carbon through sedimentation from 7 to 490 mg TEP-C/m 2 ·d was related for different coastal environments [1]. TEP have also been related to the termination of diatom spring blooms in temperate waters, since they increase aggregate formation [10][11][12].…”