Distribution of transparent exopolymer particles (TEP) in the northeast Atlantic Ocean and their potential significance for aggregation processes

Abstract

The abundance of transparent exopolymer particles (TEP) was determined in the northeast Atlantic Ocean (40-55 N, B20 W) during several cruises from June to November 1996. An accumulation of TEP in the water column was observed at bloom and post-bloom sites along a 20 W transect in June/July (maximum concentration: 124 mg Gum Xanthan equivalents (Xeq.) l À1 ), but concentrations were uniformly low (mean concentration: 28.5710.2 mg Xeq. l À1 ) during autumn at the BIOTRANS site (47 N, 20 W). TEP concentrations in the open northeast Atlantic were considerably lower than previously published values from coastal sites. However, during June/July TEP:Chl a (weight/ weight) ratios were comparable to values at coastal seas. It is suggested that phytoplankton production modulates TEP concentration in the open ocean as it does in coastal systems. TEP contributed significantly to the organic carbon pool as derived from the ratio TEP-C:POC, in summer (mean percentage: 1777.5; w/w), as well as in autumn (mean percentage: 18711, w/w). The potential influence of TEP on particle coagulation rates in the northeast Atlantic was assessed from estimates of their influence on particle stickiness and on particle volume concentrations. This indicated that TEP may be essential for initiating particle aggregation at low biomass concentrations, typical for open ocean sites. r

Programmed cell death in diazotrophs and the fate of organic matter in the Western Tropical South Pacific Ocean during the OUTPACE cruise

“…4a, Table 2). Our measured TEP concentrations correspond 470 with values and trends reported from other marine environments (Engel, 2004 LDB a significant negative correlation of TEP with DIP was also observed (Fig. 4b, p<0.001), 485…”

“…TEP concentrations (µg GX 200 equivalents L -1 ) were measured according to Passow and Alldredge (1995). To estimate the role of 201 TEP in C cycling, the total amount of TEP-C was calculated using the TEP concentrations at each 202 depth, and the conversion of GX equivalents to carbon applying the revised factor of 0.63 based on 203 empirical experiments from both natural samples from different oceanic areas and phytoplankton 204 cultures (Engel, 2004). 205…”

Modelling aggregate formation and sedimentation of organic and mineral particles

“…(12)), which suggests that the choice of the coagulation model may become important, and aggregate-dust stickiness and dust particle release by the decay of organic material control the free dust concentration profile. Since the model results are not sensitive to the stickiness parameter value, we did not include any mixed layer TEP dynamics (Prieto et al, 2002;Engel, 2004). Aggregate-dust stickiness in the deep ocean appears to be more important, at least in our model, but according to our knowledge there is not suitable information regarding these processes.…”

Dissolved organic matter (DOM) release by phytoplankton in the contemporary and future ocean

“…Exudation by phytoplankton plays a significant role in the formation of TEP (Passow, 2002b;Gärdes et al, 2011). Numerous studies have shown that exopolymer particles accumulate in phytoplankton cultures (Passow, 2002b;Claquin et al, 2008;Fukao et al, 2010) and during blooms (Passow et al, 1994;Engel et al, 2002;Engel, 2004;Harlay et al, 2009) (Figs 3,5). Generally, TEP are not exuded directly by phytoplankton cells; they form abiotically from precursors released by cells.…”