Role Of Transparent Exopolymer Particles Research Articles

Concentrations of transparent exopolymer particles (TEPs) and their role in the carbon export in the South China Sea and western tropical North Pacific

The role of TEPs in the carbon cycle remains inadequately understood in oligotrophic tropical oceans. This study investigates TEP concentrations, distributions, sinking behavior and fluxes in the oligotrophic South China Sea (SCS) and western tropical North Pacific (WTNP). The results suggested that TEPs levels were relatively low [< 60 μg Xeq. L−1 (μg xanthan gum equivalent per liter)] in both regions, and they were higher in the epipelagic layer than in deeper layers. TEP concentrations correlated significantly positively with Chl a and picophytoplankton biomass, and TEP-associated carbon contributed significantly to particulate organic carbon (POC) pool in the SCS and WTNP. The sinking flux of TEPs constituted a mean of 61% of the total POC flux in the SCS and 46% in the WTNP, highlighting their important role in carbon export in these areas. Generally, this study should provide good insight into the role TEPs play in the carbon cycle in oligotrophic tropical oceans.

The potential role of transparent exopolymer particles (TEP) and their pseudo-precursors on biofouling of RO water treatment membranes

The potential role of transparent exopolymer particles (TEP) and their pseudo-precursors on biofouling of RO water treatment membranes

Role of transparent exopolymer particles (TEP) in initial bacterial deposition and biofilm formation on reverse osmosis (RO) membrane

The fouling potential of transparent exopolymer particles (TEP) was evaluated to reveal its role in the biofouling mechanism of reverse osmosis (RO) membrane process. A methodology to determine the fouling potential of TEP was systematically developed based on cake filtration theory. The resulting cake fouling index of TEP (CFITEP) was then correlated to initial bacterial deposition observed in RO biofouling tests. Alginic acid was employed to simulate TEP and Pseudomonas aeruginosa PA14 was inoculated for biofouling test. The results showed that the fouling propensity of TEP could be assessed by cake fouling potential of particulate TEP (>0.45μm). Furthermore, the analysis of biofouled RO membranes indicated that bacterial deposition on RO membranes was enhanced significantly with increasing the cake fouling potential of TEP (i.e., CFITEP). This work demonstrated the importance of TEP at the initial stage of biofilm formation, suggesting TEP control by pretreatment for mitigating biofouling in RO applications.

Microbial metabolism of transparent exopolymer particles during the summer months along a eutrophic estuary system.

This study explores the role of transparent exopolymer particles (TEP) as an additional carbon source for heterotrophic microbial activity in the eutrophic Qishon estuary. From the coastal station and upstream the estuary; TEP concentrations, β-glucosidase activity, bacterial production and abundance have gradually increased. TEP were often found as bio-aggregates, scaffolding algae, detritus matter and bacteria that likely formed “hotspots” for enhance microbial activity. To further demonstrate the link between TEP and heterotrophic bacterial activity, confined incubations with ambient and polysaccharide-enriched estuary water were carried out. Following polysaccharide addition, elevated (~50%) β-glucosidase activity rates were observed, leading to TEP hydrolysis. This newly formed bioavailable carbon resulted in significantly higher growth rates, with up to a 5-fold increase in heterotrophic bacterial biomass, comprising mostly high nucleic acid content bacteria. Taking together the findings from this research, we conclude that even in highly eutrophic environments heterotrophic bacteria may still be carbon limited. Further, TEP as a polysaccharide matrix can act as a metabolic surrogate, adding fresh bioavailable carbon through tight associations with bacteria in eutrophic ecosystems such as the Qishon estuary.

Role of transparent exopolymer particles on membrane fouling in a full-scale ultrafiltration plant: Feed parameter analysis and membrane autopsy

Ultrafiltration (UF) is widely used for water purification, but membrane fouling remains an important issue. In this study, the role of transparent exopolymer particles (TEPs), recently put forward as possible major foulants, was investigated in the fouling process of a full-scale UF installation. Algae, TEPs and other parameters in the UF feed were monitored and correlated during an 8months long full-scale operation. Results revealed a complex fouling mechanism involving interactions mainly between algae, Fe (flocculant) and TEPs. Algae related parameters rather that TEP concentrations correlated stronger with irreversible fouling rates, suggesting that the overall role of TEPs in membrane fouling seems limited for this application. Finally, membrane autopsy showed the formation of a thick Fe-rich fouling layer on top of the fouled membranes, which could mostly be removed via cleaning-in-place. It remained partly irremovable in the form of some Fe-organic complexes.

Role of Transparent Exopolymer Particles on Phytoplankton Dynamics in a Subtropical Estuary, Canan&amp;#233;ia-Iguape (Sp, Brazil)

Transparent Exopolymer Particles (TEP) has a known crucial role in vertical fluxes of carbon in the ocean and has been intensively studied in the last decade. Nevertheless, few studies have considered horizontal fluxes of TEP. These fluxes arise prominently between estuaries and the coast, where its importance is associated to the predominant horizontal transport. This is due both to the low density of the TEP agglomerate generated in low density waters of continental origin, and to the fact that the main component of the advective transport at estuarine regions is the horizontal one. In this study, the significance of TEP in the particulate matter exchange between estuary and coast was analyzed in the estuarine lagoon system of Cananéia-Iguape (southeast coast of Brazil). TEP, total seston (TS), organic seston (OS) and chlorophyll a (Chl.a) were analyzed over complete tidal cycles, during the dry and rainy seasons both at spring and neap tides. Horizontal fluxes and net transport rates of these variables were also calculated. TEP concentrations (max. 4991 μg Xeq/L) were almost one order of magnitude higher during the rainy season. TEP horizontal transport rates as high as 1.8 g Xeq. m/s were observed at the northern inlet of the system. In terms of particulate carbon, it represents 32.7 g TEP-C m/s or 4% of the OS transport rates. Our study quantifies the advective transport of TEP and their importance in particulate matter exchange between a subtropical estuarine system and the adjacent coastal region. Our results contribute to the knowledge of exopolimer particles dynamics in subtropical estuarine systems, and their relationship to phyto-plankton biomass and particulate matter.

Transparent exopolymer particles (TEP) from marine suspension feeders enhance particle aggregation

Transparent exopolymer particles (TEP) are known to form from dissolved precursors released by phytoplankton and bacteria. Many benthic suspension feeders also have been shown to produce significant amounts of TEP under field and laboratory conditions. Although TEP from phyto- plankton have been implicated in enhancing aggregation and sedimentation of suspended material, the role of TEP from suspension feeders in aggregate formation is still unknown. In order to deter- mine if TEP produced by suspension feeders enhance the formation of marine aggregates, organic matter from actively feeding blue mussels Mytilus edulis and sea vases Ciona intestinalis held in recirculating chambers was collected. Control water was collected from chambers without animals. Animal-conditioned and control water were then mixed with 1 of 2 non-sticky particles (silica-amino beads or diatomaceous earth). The suspensions were transferred to 250 ml bottles, which were placed on a roller table to generate aggregates. Particle aggregation was quantified by examining the size distribution of particles over time by means of an electronic particle counter (particles between 6 and 90 μm), and by counting large (greater than ca. 100 μm) aggregates under a microscope at the end of the experiment. We found that significantly more aggregates formed in the animal-conditioned water than in control water after 48 h, for both species and both kinds of added particles. The number of large aggregates that formed was related to TEP concentration, and not related to total or dissolved organic carbon. Our results suggest that suspension feeders produce significant quantities of TEP that can enhance particle aggregation.

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.

Magnitude of excess carbon sequestration into the deep ocean and the possible role of TEP

It has been suggested that TEP (transparent exopolymer particles) may provide a vehicle for non-Redfield excess carbon export into the deep sea. Here, the hypothesis that organic carbon produced in excess of the Redfield C:N ratio is sequestered in the deep ocean is tested by a model-based mass balance approach. The model looks for a value of the C:N ratio of export production which is consistent with current knowledge of the rapid change of organic matter fluxes over depth, the remineralisation C:N ratio in the interior of the ocean, and the observed C:N ratios of sinking particles in the deep sea and at the sea floor. It is estimated that the contribution of excess carbon export into the deep ocean is equivalent to 3 to 5.6% (medians, depending on model assumptions; overall range: –16 to 21%) of the conventional Redfield biological pump (C:N = 6.6). Elevated C:N ratios of sinking particles in the deep ocean of 9 to 23, and their increase with depth, can be explained by C:N ratios of export production being only slightly larger than the vertically integrated C:N ratio of remineralisation in the interior of the ocean. The basin scale effect of this preferential nitrogen remineralisation, within the seasonal thermocline, on carbon sequestration is 1 order of magnitude lower compared with Redfield equivalent remineralisation or CaCO3 sequestration. The often observed increase in the C:N ratio of sinking particles with depth does not require that the remineralisation C:N ratio increases with depth, but can also arise under conditions of constant C:N remineralisation ratios. It is concluded that only a small fraction of carbon overconsumption in the surface ocean is sequestered into the deep ocean. The majority appears to be remineralised in the upper twilight zone.

The role of transparent exopolymer particles (TEP) in the increase in apparent particle stickiness (alpha) during the decline of a diatom bloom

The termination of diatom spring blooms in temperate waters has been connected with the formation and subsequent rapid sedimentation of aggregates. According to coagulation theory, the rate of aggregate formation depends on the probability of particle collision and on the efficiency with which two particles adhere once they have collided (stickiness). During this study, the variation in particle stickiness was determined over the decline of a diatom bloom using the Couette Chamber assay with low shear (G = 0.86 s–1). A mixed diatom population, dominated by Skeletonema costatum, was sampled during the spring bloom in the Baltic Sea and incubated in the laboratory for 18 days. Measurements of diatom species composition, transparent exopolymer particles (TEP) and bulk particle abundance, as well as chemical and biological variables, were conducted in order to reveal the determinants of coagulation efficiency. The investigation showed that an increase in TEP concentration relative to conventional particles at the decline of the bloom significantly enhanced apparent coagulation efficiencies. High proportions of TEP led to apparent values of stickiness >1, which indicates that collision rates can be substantially underestimated when the stickiness parameter α is calculated on the basis of conventional particle counting only, e.g. with the Coulter Counter. A new stickiness parameter, α′, was therefore estimated based on the combined volume fractions of TEP and conventional particles. The problems of stickiness measurements are discussed and the role of TEP in coagulation processes is emphasized.

Formation of macroscopic organic aggregates (lake snow) in a large lake: The significance of transparent exopolymer particles, plankton, and zooplankton

Macroscopic organic aggregates (lake snow) were collected and their abundance quantified by scuba divers at a distinct pelagic site in Lake Constance (Germany) at least twice a week throughout the growing season in 1993. Furthermore, concentrations of transparent exopolymer particles (TEP), chlorophyll, particulate organic carbon (POC), and the species composition of phytoplankton and zooplankton in the ambient water were determined. In addition, the formation of aggregates was studied in laboratory experiments by incubating water samples in rolling tanks. The abundance and composition of aggregates showed a pronounced seasonal and vertical pattern in close relation to phytoplankton and zooplankton dynamics and wind conditions. Numbers of aggregates ranged between &lt;1 and 50 liter−1, with maximum concentrations at 6 m depth in summer and fall. In spring, the peak of TEP concentration occurred simultaneously with that of lake snow, whereas the peaks in summer and fall followed those of aggregate abundance. More detailed analyses indicated that the role of TEP in aggregate formation varies throughout the season. The laboratory experiments revealed an inverse correlation between time of aggregate formation and the concentration of POC. Two different correlations, one for the spring bloom and one for the rest of the year, were established. The results show that multiple mechanisms of aggregate formation occurred throughout the seasons due to variations in source particles and physical conditions.

Aggregation of a diatom bloom in a mesocosm: The role of transparent exopolymer particles (TEP)

The role of TEP (Transparent Exopolymer Particles) in the flocculation of a diatom bloom was studied under controlled conditions in a mesocosm. The concentration of TEP increased exponentially during growth, flocculation and senescence of the bloom. Aggregation began dominating the particle dynamics of TEP during the early growth phase of the bloom, several days prior to the appearance of large flocs and nutrient depletion. TEP aggregated with themselves and with phytoplankton due to the high stickiness of TEP, but phytoplankton was not observed to aggregrate with itself. The production of TEP, estimated from changes in concentration, did not increase after nutrients were depleted. The concentration of TEP was a linear function of chl a and particulate organic carbon (POC), indicating that production of TEP was linked to growth rather than standing stocks of phytoplankton. The ratio between TEP and phytoplankton appeared to be one of the factors determining the onset of the flocculation of the bloom. The concentration of TEP may have been decreased by bacterial degradation. Bacterial degradation of TEP may explain the low TEP to chl a values, the decrease in stickiness of particles as the bloom progressed, and the retarded onset of flocculation.