Transparent Exopolymer Particles Dynamics Research Articles

Heterogeneity of Transparent Exopolymer Particles in a Coastal Marine Environment (Sagami Bay, Japan): Seasonal Variation and Its Possible Bacterial Causes

Transparent exopolymer particles (TEPs) play important roles in the regulation of carbon and pollutant (microplastics and spilled oils) transport in marine environments; however, the factors controlling TEP dynamics in coastal systems have yet to be fully clarified. A widely used colorimetric method quantifies TEPs as a homogeneous pool, which hampers the examination of internal TEP dynamics. Here, we used the microscopy to elucidate the seasonal dynamics of TEP subgroups and their controlling factors in Sagami Bay, Japan. TEPs were classified into three types: those not associated with other types of particles (Type I), those colonized by multiple types of particles (bacteria, algal cells, and detritus) (Type II), and those densely colonized by only bacterial clusters (Type III). Type II was generally the most dominant TEP component in terms of area, except in February, when Type I contributed substantially to the total TEP area. Type III was less abundant in terms of area but contributed substantially (up to 34%) to the total number of TEPs. The mean diameters were 14.0 ± 2.8 μm, 17.0 ± 5.8 μm, and 7.5 ± 0.9 μm for Type I, Type II, and Type III TEPs, respectively. Type I and Type III TEPs likely represent a transient phase of TEP development toward the formation of Type II, characterized by a high turnover and relatively low abundance in terms of area. The power-law slopes of the distributions of each TEP size, which reflected geometric features of the TEPs at steady state, changed dynamically over the seasons. The abundance of each type of TEP was significantly positively correlated with bacterial abundance, suggesting that bacteria are intimately involved in the regulation of internal TEP dynamics in Sagami Bay. Our results highlight the importance of investigating the internal dynamics of TEPs to improve current understanding of their roles in the regulation of carbon and pollutant transfer in marine environments.

Uncoupled seasonal variability of transparent exopolymer and Coomassie stainable particles in coastal Mediterranean waters

Transparent exopolymer particles (TEP) and Coomassie stainable particles (CSP) are gel-like particles, ubiquitous in the ocean, that affect important biogeochemical processes including organic carbon cycling by planktonic food webs. Despite much research on both groups of particles (especially TEP) over many years, whether they exist as distinctly stainable fractions of the same particles or as independent particles, each with different driving factors, remains unclear. To address this question, we examined the temporal dynamics of TEP and CSP over 2 complete seasonal cycles at 2 coastal sites in the Northwestern Mediterranean Sea, the Blanes Bay Microbial Observatory (BBMO) and the L’Estartit Oceanographic Station (EOS), as well as their spatial distribution along a coast-to-offshore transect. Biological, chemical, and physical variables were measured in parallel. Surface concentrations (mean ± standard deviation [SD]) of TEP were 36.7 ± 21.5 µg Xanthan Gum (XG) eq L–1 at BBMO and 36.6 ± 28.3 µg XG eq L–1 at EOS; for CSP, they were 11.9 ± 6.1 µg BSA eq L–1 at BBMO and 13.0 ± 5.9 µg BSA eq L–1 at EOS. Seasonal variability was more evident at EOS, where surface TEP and CSP concentrations peaked in summer and spring, respectively, and less predictable at the shore-most station, BBMO. Vertical distributions between surface and 80 m, monitored at EOS, showed highest TEP concentrations within the surface mixed layer during the stratification period, whereas CSP concentrations were highest before the onset of summer stratification. Phytoplankton were the main drivers of TEP and CSP distributions, although nutrient limitation and saturating irradiance also appeared to play important roles. The dynamics and distribution of TEP and CSP were uncoupled both in the coastal sites and along the transect, suggesting that they are different types of particles produced and consumed differently in response to environmental variability.

Transparent exopolymer particle dynamics along a shelf-to-sea gradient and impacts on the regional carbon cycle

Transparent exopolymer particles (TEPs) have drawn extensive attention in recent decades due to their crucial role in the biogeochemical and ecological processes of the ocean. However, TEP distribution and fluxes are relatively less addressed in the shelf-seas, where its variability can be affected by not only biology but also complex physical dynamics. Here, we present a comprehensive study of TEP from the coast to the basin (12 sampling sites) of the northern South China Sea (NSCS). We found a large TEP variability from 0.6 to 78.6 μg Xeq. L−1 with higher levels in the coastal waters than the offshore epipelagic waters and the deep waters. In addition, the spatial distribution of TEP was significantly correlated to the cross-shelf change of temperature, salinity, and chlorophyll-a, revealing the complex physical-biogeochemical controls on TEP variability. We found the TEP dynamics nearshore largely influenced by the sedimentation and transportation of TEP-rich aggregates from the river plume. The contribution of TEP to particulate organic carbon (POC) increased gradually when approaching the shore from the sea, suggesting an elevated role of TEP in the coastal carbon cycle. Finally, a good correlation of particle-attached bacteria (PAB) with TEP but not POC revealed a preferential utilization of TEP by PAB. Thus, TEP may play an essential role in the recycling of carbon and nitrogen in the shelf-sea. These findings are crucial for understanding of the TEP dynamics under a changing environment and the associated impacts on the oceanic carbon cycle.

Distribution and Settling Regime of Transparent Exopolymer Particles (TEP) Potentially Associated With Bio‐Physical Processes in the Eastern Indian Ocean

AbstractThe detailed transparent exopolymer particles (TEP) distribution, sinking behavior and the potential mechanisms behind that were revealed in the upper 200 m water column of the eastern Indian Ocean (EIO). The biological process and nutrient limitation have proved to be non‐negligible, both of which possessed potential functions in controlling the TEP pool. TEP production and fate presented significant subregional variations in the study area. The vertical distributions of TEP displayed coherent declined patterns with depth between the marginal sea and pelagic ecosystems, but the concentration of TEP horizontally decreased from marginal sea to open ocean. Dissimilarly, variable distribution patterns and magnitudes were distinguished between stratified and active current zones with the conclusion that the stratified condition was in favor of downward remove of TEP pool but turbulence facilitated the accumulation of TEP especially in the deep chlorophyll maximum (DCM) layer. Distinct sinking regimes of TEP in the stratified zone were distinguishable between layers, with the regulatory mechanisms in the upper, DCM and lower layer of water column being physical diffusion of denser seawater and solutes, aggregation by biotic and abiotic processes and buoyancy effect by entrained lighter fluid, respectively. By comparing the theoretical and measured sinking rates of TEP‐formed aggregates and considering the complicated and uncontrollable situations in non‐culture scenarios, the coupling effects of physical and biological variables on TEP dynamics were elucidated, thus providing a compelling theory for predicting the downward fate of carbon flux in the field environments.

Assessing the Temporal Variability and Drivers of Transparent Exopolymer Particle Concentrations and Production Rates in a Subtropical Estuary

Transparent exopolymer particles (TEP) are the central mechanism by which carbon is shuttled from the surface to the deep ocean. Despite the importance of these particles, the magnitude and drivers of temporal variability in the concentration and production rate of TEP in the ocean are not well resolved, especially in highly dynamic and productive regions like estuaries. Here, TEP dynamics were evaluated across weekly, tidal, and diel time scales within the Skidaway River Estuary (GA, USA) and adjacent coastal waters in the South Atlantic Bight. No significant trends in TEP concentration or production rates were observed over weekly time scales, though over tidal cycles, TEP concentration varied between tide stage and TEP:chlorophyll ratios were always lower at low relative to high tides. Over sequential diel cycles, TEP concentrations were two times higher at night relative to midday. Different biological and environmental variables were correlated with TEP dynamics (Spearman ρ) depending on the time scale considered, reinforcing the importance of time-specific drivers of TEP. These results emphasize the importance in considering the temporal variability of field-based TEP measurements, with implications for accurate assessments of carbon cycling in coastal ecosystems and the incorporation of TEP into carbon export models.

Seasonal dynamics of transparent exopolymer particles (TEP) and their drivers in the coastal NW Mediterranean Sea

Transparent Exopolymer Particles (TEPs) are a subclass of organic particles with high impact in biogeochemical and ecological processes, such as the biological carbon pump, air-sea interactions, or the microbial loop. However, the complexity in production and consumption makes TEP dynamics hardly predictable, calling for the need of descriptive studies about the in situ dynamics of these particles. We followed monthly TEP dynamics and combined them with a dataset of environmental variables during three years in a coastal site of the oligotrophic North Western Mediterranean (Blanes Bay). TEP concentration, ranging from 11.3 to 289.1μgXGeqL−1 (average 81.7±11.7μgXGeqL−1), showed recurrent peaks in early summer (June–July). TEP were temporally disconnected from chlorophyll a maxima, that occurred in late winter and early spring (maxima 1.21μgL−1), but they were significantly related to the abundance of specific phytoplankton groups (diatoms and dinoflagellates) and also coincided with periods of low nutrient concentrations. The fraction of particulate organic carbon in the form of TEP (the TEP:POC and TEP:PM ratios) were also highest in early summer, indicating that TEP-enriched particles of low density accumulate in surface waters during stratified periods. We hypothesize that the accumulation of these particles affects the microbial food web by enhancing the activity of specific prokaryotic extracellular enzymes (esterase, β-glucosidase and alkaline phosphatase) and promoting the abundance of heterotrophic nanoflagellates.

Seagrass as major source of transparent exopolymer particles in the oligotrophic Mediterranean coast

Abstract. The role of seagrass, Posidonia oceanica, meadows as a source of transparent exopolymer particles (TEPs) to Mediterranean coastal waters was tested by comparing the TEP dynamics in two adjacent coastal waters in the oligotrophic NW Mediterranean Sea, one characterized by oligotrophic open-sea waters and the other accumulating seagrass leaf litter, together with an experimental examination of TEP release by seagrass litter. TEP concentrations ranged from 4.6 to 90.6 µg XG (xanthan gum) Eq L−1, with mean (±SE) values of 38.7 (± 2.02) µg XG Eq L−1 in the site devoid of seagrass litter, whereas the coastal beach site accumulating leaf litter had > 10-fold mean TEP concentrations of 487.02 (± 72.8) µg XG Eq L−1. Experimental evaluation confirmed high rates of TEP production by P. oceanica litter, allowing calculations of the associated TEP yield. We demonstrated that P. oceanica is an important source of TEPs to the Mediterranean Sea, contributing an estimated 76 Gg C as TEPs annually. TEP release by P. oceanica seagrass explains the elevated TEP concentration relative to the low chlorophyll a concentration in the Mediterranean Sea.

Modeling aggregate dynamics of transparent exopolymer particles (TEP) and their interactions with a pelagic food web

Modeling aggregate dynamics of transparent exopolymer particles (TEP) and their interactions with a pelagic food web

Dynamics and Origin of Transparent Exopolymer Particles in the Oyashio Region of the Western Subarctic Pacific during the Spring Diatom Bloom

The seasonal biological drawdown of the partial pressure of CO2 (pCO2) in the surface waters of the Oyashio region of the western subarctic Pacific is one of the greatest among the world’s oceans. This is attributable to spring diatom blooms. Transparent exopolymer particles (TEPs) are known to affect efficiency of the biological carbon pump, and higher TEP levels are frequently associated with massive diatom blooms.However, TEP dynamics in the Oyashio region remain unclear. This study investigates the TEP distribution from three cruises during the spring diatom bloom periods in 2010 and 2011. TEP concentrations varied from -1 above 300 m and generally declined with depth. Vertical TEP concentrations were significantly related not only to chlorophyll a concentrations but also to bacterial abundance. Average TEP concentrations within the mixed layer were significantly higher during the bloom (155 ± 12 µg Xanthan gum equiv. L-1) than in the post-bloom phase (90 ± 32 µg Xanthan gum equiv. L-1). In contrast, bacteria abundance within the mixed layer changed little during the bloom to post-bloom phases. These results suggest that the abundance of phytoplankton greatly contributed to dynamics of the TEP distribution. To evaluate the ability of the phytoplankton to produce TEP, an axenic strain of the diatom Thalassiosira nordenskioeldii, which is a representative species of Oyashio blooms, was examined within a batch culture system. Cell abundance-normalized TEP and dissolved organic carbon (DOC) production rates changed simultaneously with growth of the strain. Although these production rates were significantly higher in the stationary phase than in the exponential growth period, values of the TEP/DOC ratio changed little throughout incubation. These findings suggest that TEP production in the Oyashio region may be enhanced by an increase in DOC production from spring diatoms.

Horizontal and Vertical Distributions of Transparent Exopolymer Particles (TEP) in the NW Mediterranean Sea Are Linked to Chlorophyll a and O2 Variability.

Transparent Exopolymer Particles (TEP) are relevant in particle and carbon fluxes in the ocean, and have economic impact in the desalination industry affecting reverse osmosis membrane fouling. However, general models of their occurrence and dynamics are not yet possible because of the poorly known co-variations with other physical and biological variables. Here, we describe TEP distributions in the NW Mediterranean Sea during late spring 2012, along perpendicular and parallel transects to the Catalan coast. The stations in the parallel transect were sampled at the surface, while the stations in the perpendicular transect were sampled from the surface to the bathypelagic, including the bottom nepheloid layers. We also followed the short-term TEP dynamics along a 2-day cycle in offshore waters. TEP concentrations in the area ranged from 4.9 to 122.8 and averaged 31.4 ± 12.0 μg XG eq L−1. The distribution of TEP measured in transects parallel to the Catalan Coast correlated those of chlorophyll a (Chla) in May but not in June, when higher TEP-values with respect to Chla were observed. TEP horizontal variability in epipelagic waters from the coast to the open sea also correlated to that of Chla, O2 (that we interpret as a proxy of primary production) and bacterial production (BP). In contrast, the TEP vertical distributions in epipelagic waters were uncoupled from those of Chla, as TEP maxima were located above the deep chlorophyll maxima. The vertical distribution of TEP in the epipelagic zone was correlated with O2 and BP, suggesting combined phytoplankton (through primary production) and bacterial (through carbon reprocessing) TEP sources. However, no clear temporal patterns arose during the 2-day cycle. In meso- and bathypelagic waters, where phytoplanktonic sources are minor, TEP concentrations (10.1 ± 4.3 μg XG eq l−1) were half those in the epipelagic, but we observed relative TEP increments coinciding with the presence of nepheloid layers. These TEP increases were not paralleled by increases in particulate organic carbon, indicating that TEP are likely to act as aggregating agents of the mostly inorganic particles present in these bottom nepheloid layers.

Dynamics of transparent exopolymer particles (TEP) during the VAHINE mesocosm experiment in the New Caledonian lagoon

Abstract. In the marine environment, transparent exopolymeric particles (TEP) produced from abiotic and biotic sources link the particulate and dissolved carbon pools and are essential vectors enhancing vertical carbon flux. We characterized spatial and temporal dynamics of TEP during the VAHINE experiment that investigated the fate of diazotroph-derived nitrogen and carbon in three replicate dissolved inorganic phosphorus (DIP)-fertilized 50 m3 enclosures in the oligotrophic New Caledonian lagoon. During the 23 days of the experiment, we did not observe any depth-dependent changes in TEP concentrations in the three sampled depths (1, 6, 12 m). TEP carbon (TEP-C) content averaged 28.9 ± 9.3 and 27.0 ± 7.2 % of total organic carbon (TOC) in the mesocosms and surrounding lagoon respectively and was strongly and positively coupled with TOC during P2 (i.e., days 15–23). TEP concentrations in the mesocosms declined for the first 9 days after DIP fertilization (P1 = days 5–14) and then gradually increased during the second phase. Temporal changes in TEP concentrations paralleled the growth and mortality rates of the diatom–diazotroph association of Rhizosolenia and Richelia that predominated the diazotroph community during P1. By P2, increasing total primary and heterotrophic bacterial production consumed the supplemented P and reduced availability of DIP. For this period, TEP concentrations were negatively correlated with DIP availability and turnover time of DIP (TDIP), while positively associated with enhanced alkaline phosphatase activity (APA) that occurs when the microbial populations are P stressed. During P2, increasing bacterial production (BP) was positively correlated with higher TEP concentrations, which were also coupled with the increased growth rates and aggregation of the unicellular cyanobacterial Group C (UCYN-C) diazotrophs that bloomed during this period. We conclude that the composite processes responsible for the formation and breakdown of TEP yielded a relatively stable TEP pool available as both a carbon source and facilitating aggregation and flux throughout the experiment. TEP were probably mostly influenced by abiotic physical processes during P1, while biological activity (BP, diazotrophic growth and aggregation, export production) mainly impacted TEP concentrations during P2 when DIP availability was limited.

Transparent exopolymer particles: from aquatic environments and engineered systems to membrane biofouling.

Transparent exopolymer particles (TEP) are ubiquitous in marine and freshwater environments. For the past two decades, the distribution and ecological roles of these polysaccharide microgels in aquatic systems were extensively investigated. More recent studies have implicated TEP as an active agent in biofilm formation and membrane fouling. Since biofouling is one of the main hurdles for efficient operation of membrane-based technologies, there is a heightened interest in understanding the role of TEP in engineered water systems. In this review, we describe relevant TEP terminologies while critically discussing TEP biological origin, biochemical and physical characteristics, and occurrence and distributions in aquatic systems. Moreover, we examine the contribution of TEP to biofouling of various membrane technologies used in the desalination and water/wastewater treatment industry. Emphasis is given to the link between TEP physicochemical and biological properties and the underlying biofouling mechanisms. We highlight that thorough understanding of TEP dynamics in feedwater sources, pretreatment challenges, and biofouling mechanisms will lead to better management of fouling/biofouling in membrane technologies.

Effects of nutrients and turbulence on the production of transparent exopolymer particles: a mesocosm study

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 419:57-69 (2010) - DOI: https://doi.org/10.3354/meps08840 Effects of nutrients and turbulence on the production of transparent exopolymer particles: a mesocosm study M. L. Pedrotti1,*, F. Peters2, S. Beauvais1, M. Vidal3, J. Egge4, A. Jacobsen4, C. Marrasé2 1Marine Microbial Ecology Group, Laboratoire d’Océanographie de Villefranche, CNRS-UMR 7093, BP 28, 06234 Villefranche-sur-mer, France 2Institut de Ciències del Mar, CMIMA (CSIC), Passeig Marítim de la Barceloneta 37-49, 08003 Barcelona, Catalunya, Spain 3Departament d’Ecology, Universitat de Barcelona, Barcelona, Spain 4Department of Fisheries and Marine Biology, University of Bergen, HIB, 5020 Bergen, Norway *Email: pedrotti@obs-vlfr.fr ABSTRACT: The production of transparent exopolymer particles (TEP) in response to several environmental variables was studied in 2 mesocosm experiments. The first (Expt 1) examined a gradient of 4 nutrient levels; the second (Expt 2) examined different conditions of silicate availability and zooplankton presence. Tanks were separated in 2 series, one subjected to turbulence and the other not influenced by turbulence. In tanks with nutrient addition, TEP were rapidly formed, with net apparent production rates closely linked to chl a growth rates, suggesting that phytoplankton cells were actively exuding TEP precursors. High nutrient availability increased the absolute concentration of TEP; however, the relative quantity of TEP produced was found to be lower, as TEP concentration per unit of phytoplankton biomass was inversely related to the initial nitrate dose. In Expt 1, an increase in TEP volume (3 to 48 µm equivalent spherical diameter) with nutrient dose was observed; in Expt 2, both silicate addition and turbulence enhanced TEP production and favored aggregation to larger TEP (>48 µm). The presence of zooplankton lowered TEP concentration and changed the size distribution of TEP, presumably by grazing on TEP or phytoplankton. For lower nutrient concentrations, the ratio of particulate organic carbon (POC) to particulate organic nitrogen (PON) followed the Redfield ratio. At higher nutrient conditions, when nutrients were exhausted during the post-bloom, a decoupling of carbon and nitrogen dynamics occurred and was correlated to TEP formation, with a large flow of carbon channeled toward the TEP pool in turbulent tanks. TEP accounted for an increase in POC concentration of 50% in high-nutrient and turbulent conditions. The study of TEP dynamics is crucial to understanding the biogeochemical response of the aquatic system to forcing variables such as nutrient availability and turbulence intensity. KEY WORDS: Transparent exopolymer particles · TEP production · Phytoplankton · Particulate organic carbon · POC · Turbulence · Nutrients · Mesocosms Full text in pdf format PreviousNextCite this article as: Pedrotti ML, Peters F, Beauvais S, Vidal M, Egge J, Jacobsen A, Marrasé C (2010) Effects of nutrients and turbulence on the production of transparent exopolymer particles: a mesocosm study. Mar Ecol Prog Ser 419:57-69. https://doi.org/10.3354/meps08840 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 419. Online publication date: November 30, 2010 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2010 Inter-Research.

Production of transparent exopolymer particles by four diatom species

The production of transparent exopolymer particles (TEP) by four diatoms, Coscinodiscus granii, Eucampia zodiacus, Rhizosolenia setigera, and Skeletonema sp., was examined. Most of the TEP in C. granii (74% of the maximum) were produced during the growth phase. In contrast, most of the TEP in E. zodiacus (73%), R. setigera (74%), and Skeletonema sp. (70%) were produced during the stationary and declining phases. The C. granii TEP production rate was highest in the growth phase, whereas those in E. zodiacus, R. setigera, and Skeletonema sp. were highest in the stationary–decline phase. The TEP concentrations per cell and the cell volume of C. granii were 34.97 ± 4.114 (mean ± SD) ng Xeq./cell (xanthan gum equivalents per cell) and 341.6 ± 56.33 fg Xeq./μm3, and were 23.01 and 4.32 times higher than the values obtained from the other three diatoms, respectively. The results suggest that the mechanisms of TEP production differ with growth stage and diatom species. Therefore, it is likely that the differences in TEP production among the diatom species influence the complexity of TEP dynamics in aquatic environments.

Significance of Bacterial Activity for the Distribution and Dynamics of Transparent Exopolymer Particles in the Mediterranean Sea

The study of transparent exopolymer particles (TEP) in the Mediterranean Sea is particularly relevant as they can be promoters of mucilage events, a frequent phenomenon there. We assessed the influence of bacterioplankton on TEP distribution and dynamics across the west-east axis of the Mediterranean Sea. We performed an extensive study of TEP, dissolved carbohydrates, and their relationships with bacterial abundance and bacterial production (BP). A significant and positive relationship was observed between BP and TEP in the study region (r (2) = 0.51, p < 0.001). The direct release of TEP by bacteria was experimentally corroborated using regrowth cultures where increases in TEP tracked bacterial growth in abundance and production. These TEP increases were positively related to the increases in BP (r (2) = 0.78, p < 0.05). The consistency (similar slopes) of the regression lines between BP and TEP in natural conditions and between the increases of BP and TEP in the experiments underlines the relevant role of bacteria in the formation of TEP in this area.

Effects of ultraviolet B radiation on (not so) transparent exopolymer particles

Abstract. Transparent exopolymer particles (TEP) are the most ubiquitous gel particles in the ocean and form abiotically from dissolved precursors. Although these particles can accumulate at the ocean surface, being thus exposed to intense sunlight, the role of solar radiation for the assembly and degradation of TEP is unknown. In this study, we experimentally determined the effects of visible and ultraviolet B (UVB) radiation on (1) TEP degradation (photolysis experiments), (2) TEP assembly from dissolved polymers (photoinhibition experiments) and (3) TEP release by microorganisms. Solar radiation, particularly in the UVB range, caused significant TEP photolysis, with loss rates from 27 to 34% per day. Dissolved polysaccharides did not increase in parallel. No TEP were formed under UVB, visible or dark conditions, indicating that light does not promote TEP assembly. UVB radiation enhanced TEP release by microorganisms, possibly due to cell deaths, or as a protective measure. Increases in UVB may lead to enhanced TEP photolysis in the ocean, with further consequences for TEP dynamics and, ultimately, sea-air gas exchange.

Marine bacterioplankton production of polysaccharidic and proteinaceous particles under different nutrient regimes

The influence of inorganic nutrient concentrations on the ability of bacterioplankton to produce and degrade polysaccharidic transparent exopolymer particles (TEPs) and proteinaceous Coomassie-stained particles (CSPs) was investigated in an 11-day experiment. The dynamics of these particles were followed in prefiltered (1 microm) northern Adriatic seawater enclosures enriched either with 1 microM orthophosphate (main limiting nutrient in this area), 10 microM ammonium or both orthophosphate and ammonium. These enclosures were referenced to a nonenriched control. A high potential for bacterial TEP and CSP production was observed (10(4) - 10(5) L(-1) for particles larger than 4 microm). In conditions of high orthophosphate concentration (either orthophosphate enriched or both orthophosphate and ammonium enriched), lower abundances and surface areas of CSPs were obtained, whereas TEP dynamics were more affected by unbalanced enrichments where only orthophosphate or ammonium was added. The impact of unbalanced nutrient ratios on TEPs was indicated by their higher abundance but low capacity for Alcian blue absorption, implying a change in their structure. Inorganic nutrient availability was thus proven to affect the bacterial potential for producing and degrading bacterially derived TEPs and CSPs.

Transparent exopolymeric particles' distribution in the northern Adriatic and their relation to microphytoplankton biomass and composition

Transparent exopolymer particles (TEP) are generated during transformation processes within the non-living organic matter continuum in the seawater. Seasonal dynamics of TEP along the Po River Delta–Rovinj transect was followed during the 3-year period, using a spectrophotometric method of determination of TEP. Relationships between TEP and phytoplankton biomass (chlorophyll a), abundance and composition, as well as phaeophytin, were analysed. Microphytoplankton spring blooms are confirmed to be an important source of TEP, with some species more related to TEP concentration dynamics, such as Chaetoceros sp. and Skeletonema costatum. Notable spatial west to east gradient of autotrophic biomass and consequently of TEP was observed, as well as gradual decrease with depth. In addition, TEP concentration increments were observed up to 2 months before the mucilage events followed by the decrease of TEP concentration during the event itself. Pattern of TEP dynamics in the years with mucilage events was the most pronounced in 2002, when the event was spatially and temporally the most extended.

The role of transparent exopolymer particles (TEP) in the transport of 234Th in coastal water during a spring bloom

The role of transparent exopolymer particles (TEP) in the biogeochemical cycle of reactive elements in the upper ocean was studied using a thorium isotope ( 234Th) as a tracer during a spring bloom in a coastal bay. TEP concentrations were consistently higher at 0 m ( < 5 cm ) during the bloom than at 5 m, where chlorophyll- a concentrations were highest, even though active TEP formation occurs from extracellular polysaccharides excreted by bacteria and phytoplankton. This trend is especially evident toward the end of the bloom. 234Th: 238U activity ratios measured at 0 and 5 m over the bloom period demonstrated the transport of 234Th to the surface water. The 234Th: 238U activity ratio at 0 m was positively correlated with TEP concentration. Simultaneous enrichment of 234Th and TEP in the surface water indicated that the TEP dynamics in the upper ocean play an important role for the accumulation of 234Th. A possible cause of surface TEP and 234Th enrichment is active TEP production by the subsurface phytoplankton bloom followed by their rapid transport to the surface. Our study suggests a new pathway of TEP and associated particle-reactive elements in the upper ocean biogeochemical cycles during a spring bloom in a coastal area. The observed accumulation of 234Th in the surface layer needs to be considered when the strength of the biological pump is estimated using 234Th.

Effect of iron enrichment on the dynamics of transparent exopolymer particles in the western subarctic Pacific

Dynamics of transparent exopolymer particles (TEP) was studied during the first in situ iron-enrichment experiment conducted in the western subarctic Pacific in July–August 2001, with the goal of evaluating the contribution of TEP to vertical flux as a result of increased primary production following iron enrichment in open ocean ecosystems. Subsequent to the enhancement of phytoplankton production, we observed increase in TEP concentration in the surface layer and sedimentation of organic matter beneath it. Vertical profiles of TEP, chlorophyll a (Chl a) and particulate organic carbon (POC) were obtained from six depths between 5 and 70 m, from a station each located inside and outside the enriched patch. TEP and total mass flux were estimated from the floating sediment traps deployed at 200 m depth. Chl a and TEP concentrations outside the patch varied from 0.2 to 1.9 μg L −1 and 40–60 μg XG equiv. L −1, respectively. Inside the patch, Chl a increased drastically from day 7 reaching the peak of 19.2 μg L −1 on day 13, which coincided with the TEP peak of 189 μg XG equiv. L −1. TEP flux in the sediment trap increased from 41 to 88 mg XG equiv. m −2 d −1, with 8–14% contribution of TEP to total mass flux. This forms the basic data set on ambient concentrations of TEP in the western subarctic Pacific, and evaluation of the effect of iron enrichment on TEP.