Transparent Exopolymer Particles Production Research Articles

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.

Diatom-associated bacteria are required for aggregation of Thalassiosira weissflogii

Aggregation of algae, mainly diatoms, is an important process in marine systems leading to the settling of particulate organic carbon predominantly in the form of marine snow. Exudation products of phytoplankton form transparent exopolymer particles (TEP), which acts as the glue for particle aggregation. Heterotrophic bacteria interacting with phytoplankton may influence TEP formation and phytoplankton aggregation. This bacterial impact has not been explored in detail. We hypothesized that bacteria attaching to Thalassiosira weissflogii might interact in a yet-to-be determined manner, which could impact TEP formation and aggregate abundance. The role of individual T. weissflogii-attaching and free-living new bacterial isolates for TEP production and diatom aggregation was investigated in vitro. T. weissflogii did not aggregate in axenic culture, and striking differences in aggregation dynamics and TEP abundance were observed when diatom cultures were inoculated with either diatom-attaching or free-living bacteria. The data indicated that free-living bacteria might not influence aggregation whereas bacteria attaching to diatom cells may increase aggregate formation. Interestingly, photosynthetically inactivated T. weissflogii cells did not aggregate regardless of the presence of bacteria. Comparison of aggregate formation, TEP production, aggregate sinking velocity and solid hydrated density revealed remarkable differences. Both, photosynthetically active T. weissflogii and specific diatom-attaching bacteria were required for aggregation. It was concluded that interactions between heterotrophic bacteria and diatoms increased aggregate formation and particle sinking and thus may enhance the efficiency of the biological pump.

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.

Bacterial colonization of transparent exopolymeric particles in mesocosms under different turbulence intensities and nutrient conditions

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 55:301-312 (2009) - DOI: https://doi.org/10.3354/ame01308 Bacterial colonization of transparent exopolymeric particles in mesocosms under different turbulence intensities and nutrient conditions M. L. Pedrotti1,*, S. Beauvais1, M.-E. Kerros1, K. Iversen2, F. Peters3 1Marine Microbial Ecology Group, Laboratoire d’Océanographie de Villefranche, University of Paris VI, CNRS UMR 7093, Observatoire Océanologique de Villefranche-sur-Mer, Station Zoologique, BP 28, 06234 Villefranche-sur-Mer, France 2Department of Aquatic Biosciences, Norwegian College of Fishery Science, University of Tromsø, Breivika, 9037 Tromsø, Norway 3Institut de Ciències del Mar, CMIMA (CSIC) Passeig Maritim de la Barceloneta, 08003 Barcelona, Catalunya, Spain *Email: pedrotti@obs-vlfr.fr ABSTRACT: We examined bacterial colonization of transparent exopolymeric particles (TEP) in nutrient-manipulated mesocosms subjected to different turbulence intensities. We quantified heterotrophic bacterial abundance, production and diversity using fluorescence in situ hybridization (FISH). The abundance of attached bacteria increased significantly with TEP size in all treatments. The slope values of the number of bacteria scaled with TEP size varied from 1.15 on Day 1 to 2.04 on Day 11 in still and turbulent tanks, respectively. Comparison between these slopes indicated that the number of attached bacteria for a given TEP diameter was higher under turbulence. The addition of nutrients and turbulence in mesocosms neither supported higher bacterial abundance nor resulted in a correlation between bacterial concentrations and TEP. However, in enriched turbulent tanks, the number of attached bacteria was higher and was linked to rapid TEP formation after the diatom bloom. This was accompanied by higher bacterial production (1.21 µmol C l–1 d–1 at the intermediate level of turbulence on Day 9), which was positively related to TEP. These correlations highlight the finding that higher bacterial productivity was due to a larger fraction of attached bacteria (up to 56.4%). Changes in bacterial production occurred with simultaneous changes in the community structure, i.e. the percentages of the Cytophaga-Flavobacteria-Bacteroides cluster increased significantly. By Day 9, this cluster became the dominant group of bacteria attached to TEP (85 and 90%, respectively at intermediate and high levels of turbulence). Among the marine heterotrophic bacterioplankton, this phylum is known to be common as attached bacteria. Therefore, it seems that the added nutrients and subsequent TEP production can be used by bacteria more efficiently under turbulent conditions through a shift in group-specific composition towards more attached bacteria with higher production rates. KEY WORDS:Transparent exopolymer particles · Particle colonization · Bacteria · FISH · Turbulence · Nutrients · Mesocosms Full text in pdf format PreviousNextCite this article as: Pedrotti ML, Beauvais S, Kerros ME, Iversen K, Peters F (2009) Bacterial colonization of transparent exopolymeric particles in mesocosms under different turbulence intensities and nutrient conditions. Aquat Microb Ecol 55:301-312. https://doi.org/10.3354/ame01308 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 55, No. 3. Online publication date: June 24, 2009 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2009 Inter-Research.

Marine mucilage in Ariake Sound, Japan, is composed of transparent exopolymer particles produced by the diatom Coscinodiscus granii

Concomitant with the bloom of a diatom, Coscinodiscus sp., there was a sudden production of mucilage in the central area of Ariake Sound during the autumn of 2007. To obtain basic information about this marine mucilage and identify the causative organism, we have examined the morphological characteristics of Coscinodiscus sp. and the production of transparent exopolymer particles (TEPs) by this species. Light and electron microscopy studies revealed that the morphological characteristics of the species under investigation were consistent with previous descriptions of Coscinodiscus granii and, hence, we identified this species as C. granii. Alcian blue staining revealed that the TEPs produced by C. granii were composed of acidic polysaccharides. The properties of these polysaccharides were examined using two fluorescein isothiocyanate (FITC)-labeled lectins: FITC-concanavalin A (Con A), which is specific for d-mannose and/or d-glucose, and Ulex europaeus agglutinin-1 (UEA-1)-FITC, which is specific for l-fucose. The Con A label scarcely reacted with the surface of the marine mucilage produced by C. granii, while UEA-1-FITC showed a strong reaction. These results indicate that the TEPs produced by C. granii contain more l-fucose than d-mannose and/or d-glucose. Such TEPs with high l-fucose content are known to be highly viscous. We conclude, therefore, that the polysaccharide composition of the TEPs produced by C. granii may determine the viscosity of the marine mucilage.

Biocalcification by Emiliania huxleyi in batch culture experiments

AbstractCoccolithophores, among which Emiliania huxleyi is the most abundant and widespread species, are considered the most productive calcifying organism on earth. The export of organic carbon and calcification are the main drivers of the biological CO2 pump and are expected to change with oceanic acidification. Coccolithophores are further known to produce transparent exopolymer particles (TEP) that promote particle aggregation. As a result, the TEP and biogenic calcium carbonate (CaCO3) contribute to the export of carbon from the surface ocean to deep waters. In this context, we followed the development and the decline of E. huxleyi using batch experiments with monospecific cultures. We studied the link between different processes such as photosynthesis, calcification and the production of TEP. The onset of calcification was delayed in relation to photosynthesis. The timing and the general feature of the dynamics of calcification were closely related to the saturation state of seawater with respect to calcite, Ωcal. The production of TEP was enhanced after the decline of phytoplankton growth. After nutrient exhaustion, particulate organic carbon (POC) concentration increased linearly with increasing TEP concentration, suggesting that TEP contributes to the POC increase. The production of CaCO3 is also strongly correlated with that of TEP, suggesting that calcification may be considered as a source of TEP precursors.

Coupling between autocatalytic cell death and transparent exopolymeric particle production in the marine cyanobacterium Trichodesmium

Extracellular polysaccharide aggregates, operationally defined as transparent exopolymeric particles (TEP), are recognized as an important conduit for carbon recycling and export in aquatic systems. Yet, the factors controlling the build-up of the TEP pool are not well characterized. Here we show that increased TEP production by Trichodesmium, an oceanic bloom-forming nitrogen-fixing (diazotrophic) cyanobacterium, is coupled with autocatalytic programmed cell death (PCD) process. We demonstrate that PCD induction, in both laboratory cultures and natural populations, is characterized by high caspase-like activity, correlates with enhanced TEP production, and occurs under iron and phosphorus starvation, as well as under high irradiance and oxidative stress. Enhanced TEP production was not observed in actively growing populations. We provide further evidence that iron is a key trigger for the induction of PCD. We demonstrate, for the first time, the concomitant enhanced build-up of the TEP pool when Trichodesmium is Fe-stressed. These results suggest a functional linkage between activation of caspases and PCD in Trichodesmium and regulation of vertical carbon and nitrogen fluxes. We hypothesize that modulation of TEP formation and its qualities by different mortality pathways could regulate the fate of phytoplankton blooms and particulate organic matter in aquatic ecosystems.

Carbon isotopic fractionation during a mesocosm bloom experiment dominated by Emiliania huxleyi: Effects of CO 2 concentration and primary production

We investigated the effect of CO 2 and primary production on the carbon isotopic fractionation of alkenones and particulate organic matter (POC) during a natural phytoplankton bloom dominated by the coccolithophore Emiliania huxleyi. In nine semi-closed mesocosms (∼11 m 3 each), three different CO 2 partial pressures ( pCO 2) in triplicate represented glacial (∼180 ppmv CO 2), present (∼380 ppmv CO 2), and year 2100 (∼710 ppmv CO 2) CO 2 conditions. The largest shift in alkenone isotopic composition (4–5‰) occurred during the exponential growth phase, regardless of the CO 2 concentration in the respective treatment. Despite the difference of ∼500 ppmv, the influence of pCO 2 on isotopic fractionation was marginal (1–2‰). During the stationary phase, E. huxleyi continued to produce alkenones, accumulating cellular concentrations almost four times higher than those of exponentially dividing cells. Our isotope data indicate that, while alkenone production was maintained, the interaction of carbon source and cellular uptake dynamics by E. huxleyi reached a steady state. During stationary phase, we further observed a remarkable increase in the difference between δ 13C of bulk organic matter and of alkenones spanning 7–12‰. We suggest that this phenomenon is caused mainly by a combination of extracellular release of 13C-enriched polysaccharides and subsequent particle aggregation induced by the production of transparent exopolymer particles (TEP).

Production of transparent exopolymer particles (TEP) by benthic suspension feeders in coastal systems

In the marine environment, transparent exopolymer particles (TEP) are ubiquitous and abundant, playing a significant role in carbon cycling and the structuring of food webs. Previous studies have shown that phytoplankton, bacteria, and oysters contribute to the production of TEP through the release of exopolymers. However, little is known about other potential sources of TEP and TEP precursors, especially in coastal systems. It was hypothesized that suspension feeders contribute to the TEP pool in near-shore environments through the release of exopolymers in both the dissolved and particulate form, and tested these hypotheses in both laboratory and field experiments. In the laboratory, the production of TEP by several species of benthic suspension feeders (the blue mussel, Mytilus edulis; the bay scallop, Argopecten irradians; the slipper snail, Crepidula fornicata; and the solitary ascidians, Ciona intestinalis and Styela clava) was investigated from October to November 2002 and June 2003. Concentrations of TEP and DOC were determined by spectrophotometry after alcian blue staining and high-temperature, catalytic oxidation, respectively. Similar analyses were conducted on water samples from the field in July 2003, collected in close proximity to dense beds of mussels in the Poquonnock River, Connecticut, USA (41°19′ N, − 72°02′ W). Laboratory results indicated that actively-pumping blue mussels, bay scallops, slipper snails, and both species of solitary ascidians significantly enhanced TEP concentrations above background levels over a five-hour period. However, only the solitary tunicate S. clava significantly enhanced DOC concentrations above background levels over the same period of time. Field samples indicated that TEP and DOC concentrations were high in close proximity to dense beds of mussels. These results imply that a variety of benthic suspension feeders produce TEP during feeding activities which could lead to enhanced flocculation of organic matter and carbon deposition in near-shore waters.

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.

Distribution of TEP in the euphotic and upper mesopelagic zones of the southern Iberian coasts

The spatial and temporal distributions of transparent exopolymer particles (TEP) were studied for the Gulf of Cádiz, by analyzing its abundance in the euphotic and upper mesopelagic zones. Both layers of the water column should reflect a distinct pattern in TEP distribution, as production of TEP is mainly linked to phytoplankton activity, which is sited in the euphotic zone, while losses of TEP due to aggregation-sinking and degradation occur from the surface to further below in the water column. Concentration of TEP in the euphotic zone reflected the varied oceanographic characteristics of the studied region. It was higher in coastal upwellings, fronts and such areas of topographic forcing, suggesting that TEP were being produced by active growing phytoplankters. A comparison with a well-known ecosystem, the coastal upwelling in the northwestern Alboran Sea, showed that the TEP:Chl a ratio at stations with clear eutrophic characteristics was several orders of magnitude lower than in the area southwest of the anticyclonic current of the Gulf. This ratio in the highly dynamic system of the Strait of Gibraltar seems to have a much clearer relation with the stage of a bloom and, at a basin scale, to the trophic condition of the ecosystem than TEP concentrations alone. Throughout the area studied in the Gulf of Cádiz, the role of TEP for aggregation processes was analyzed based on two aggregation models. Both approximations pointed to the importance of TEP in the export of matter from the euphotic zone to deeper waters in the Gulf of Cádiz.

Trophic significance of solitary cells of the prymnesiophyte Phaeocystis globosa depends on cell type

With the use of five different isolates of Phaeocystis globosa solitary cells from the North Sea, we conducted experiments to reveal whether grazing and development of the nauplii of the calanoid copepod Temora longicornis varies in response to the cell type. Two P. globosa strains representing nonflagellated cells were ingested at intermediate to high rates and resulted in high survival and development, comparable to the Rhodomonas sp. control. In contrast, the response to three mesoflagellate strains was highly variable. Feeding on two of these strains was avoided, whereas the third strain was ingested; however, the mesoflagellates induced poor survival and development regardless of the feeding response. These observations differ from previous results, which generally demonstrate microzooplankton feeding on Phaeocystis. The morphological characterization of strains, together with mixture experiments, revealed that neither the production of transparent exopolymer particles and chitinous threads nor toxicity can explain the observed response. The cohesion of the threads into pentagonal stars was observed only in the avoided mesoflagellate and might cause a mechanical hindrance for the ingestion of mesoflagellates. Our results suggest that grazing loss and trophic transfer efficiency might be overestimated when solitary cells are treated as a single functional group with regard to their trophic position.

Dynamics of transparent exopolymeric particles (TEP) production by Phaeocystis globosa under N- or P-limitation: a controlling factor of the retention/export balance

The concentration of transparent exopolymeric particles (TEP) was monitored during Phaeocystis globosa blooms that developed in mesocosms under different initial N:P ratios (from N- to P-limited conditions). TEP concentration was measured using the microscopic (TEP micro, ppm) and the colorimetric (TEP color, Xanthan equiv. L −1) methods. TEP concentrations varied from 5 to >75 ppm and from 60 to >1500 μg Xanthan equiv. L −1, and were relatively low until the mesocosms reached nutrient (either N or P) depletion and then increased abruptly. From the TEP micro versus TEP color concentrations comparison and from their relation to chlorophyll a concentrations, two phases for the dynamics of TEP production were identified: (1) production through active release of precursors during the growth phase of P. globosa — defined as TEP 1 — and their integration into the TEP pool through coagulation processes; (2) release of large TEP from the mucilaginous matrix of P. globosa colonies subsequent to disruption caused by nutrient depletion — defined as TEP 2 — and their direct integration into the TEP pool outside the constraint of coagulation. The formation of a multiorigin TEP pool during P. globosa blooms may have implications for the fate of the blooms, due to difference in TEP bioreactivity according to their source and to difference in timing and intensity of TEP 1 versus TEP 2 production according to N- or P-depletion. For P. globosa blooms developing under N-limiting conditions, the transition from the first source (i.e. TEP 1) to the second one (i.e. TEP 2) was a slow and continuous process. In contrast, the P. globosa bloom developing under P-limiting conditions showed the sudden formation of heavy mucous aggregates when P became depleted, that may have been caused by a massive release of TEP 2. Our study suggests that the nutrient regime may control the export vs. retention balance during P. globosa blooms, via production of a multiorigin TEP pool.

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.

Inhibition of copepod feeding by exudates and transparent exopolymer particles (TEP) derived from a Phaeocystis globosa dominated phytoplankton community

We investigated if (1) dissolved compounds excreted by Phaeocystis globosa and (2) transparent exopolymer particles (TEP) formed from carbohydrates excreted into the water affect the feeding of nauplii and females of the calanoid copepod Temora longicornis during a P. globosa bloom. Copepod grazing on the diatom Thalassiosira weissflogii in the presence of these possible grazing deterrents was measured during three successive weeks of a mesocosm study, simulating the development of a P. globosa bloom. Our results demonstrate no indication for the presence of feeding deterrents in the dissolved phase, but a strong inhibitory effect of transparent exopolymer particles (TEP) on the consumption of algae by both nauplii and adult copepods. The inhibitory effect of TEP was connected to the accumulation of DOM during the progress of the bloom. We suggest that a reduction in the grazing pressure of zooplankton may increase the survival of the liberated single cells during disruption of colonies and allow seeding populations to persist. Furthermore, P. globosa reduces the trophic efficiency of the food web not only by withdrawal of its colonies from grazing but also by a relaxation of the grazing pressure on co-occurring phytoplankton and by alteration of the food web structure via TEP production.

Production of transparent exopolymer particles (TEP) by the eastern oyster Crassostrea virginica

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 288:141-149 (2005) - doi:10.3354/meps288141 Production of transparent exopolymer particles (TEP) by the eastern oyster Crassostrea virginica Michael P. McKee1,*, J. Evan Ward1, Bruce A. MacDonald2, Bridget A. Holohan1 1Department of Marine Sciences, University of Connecticut, 1080 Shennecossett Road, Groton, Connecticut 06340, USA2Department of Biology, University of New Brunswick, Saint John, PO Box 5050, New Brunswick E2L 4L5, Canada *Email: mckee@uconn.edu ABSTRACT: Transparent exopolymer particles (TEP) play an important role in aggregation, phytoplankton bloom dynamics and the fate of organic carbon. Various types of plankton are known to release exopolymers that contribute to the TEP pool. Little is known, however, about other potential sources of TEP and TEP precursors in the oceans, especially in nearshore waters. Suspension-feeding bivalves can form dense assemblages in coastal waters and can process large volumes of water during feeding activities (e.g. 5 l h–1 g–1 dry wt). They secrete mucus to maintain clean body surfaces and to aid in capturing and transporting food material. We hypothesized that mucopolysaccharides, which are released from bivalves in dissolved or particulate form, contribute to the TEP pool. To test this hypothesis, laboratory experiments were carried out to measure the concentration of TEP and DOC in chambers with actively feeding oysters Crassostrea virginica over a 9 h period. Field experiments were conducted to measure TEP and DOC production by oysters in situ, using clear Plexiglas chambers on an intertidal sand-flat in New Brunswick, Canada. TEP concentrations were determined with an Alcian blue staining technique and spectrophotometric detection. DOC concentrations were determined using high-temperature catalytic oxidation (HTCO) with a platinum catalyst. Laboratory results indicated that oysters significantly enhanced TEP and DOC concentrations compared to control levels over 9 h. Likewise, field experiments demonstrated elevated TEP concentrations in experimental chambers compared to control treatments. Our results support the hypothesis that oysters contribute to the production of TEP in coastal marine ecosystems. KEY WORDS: Transparent exopolymer particles · TEP · Mucopolysaccharides · Oysters · Dissolved organic carbon · DOC · Aggregation Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 288. Online publication date: March 10, 2005 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2005 Inter-Research.

Transparent exopolymer particles and dissolved organic carbon production by Emiliania huxleyi exposed to different CO2 concentrations: a mesocosm experiment

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 34:93-104 (2004) - doi:10.3354/ame034093 Transparent exopolymer particles and dissolved organic carbon production by Emiliania huxleyi exposed to different CO2 concentrations: a mesocosm experiment Anja Engel1,*, Bruno Delille2, Stéphan Jacquet3, Ulf Riebesell1, Emma Rochelle-Newall4, Anja Terbrüggen1, Ingrid Zondervan1 1Alfred Wegener Institute for Polar- and Marine Research, 27515 Bremerhaven, Germany 2Unité d¹Océanographie Chimique, Université de Liège, 4000 Liège, Belgium 3UMR CARRTEL, Station INRA d¹Hydrobiologie Lacustre, 74203 Thonon-les-Bains cedex, France 4Laboratoire d¹Océanographie de Villefranche-sur-Mer, 06234 Villefranche-sur-Mer, France *Email: aengel@awi-bremerhaven.de ABSTRACT: The role of transparent exopolymer particles (TEP) and dissolved organic carbon (DOC) for organic carbon partitioning under different CO2 conditions was examined during a mesocosm experiment with the coccolithophorid Emiliania huxleyi. We designed 9 outdoor enclosures (~11 m3) to simulate CO2 concentrations of estimated ŒYear 2100¹ (~710 ppm CO2), Œpresent¹ (~410 ppm CO2) and Œglacial¹ (~190 ppm CO2) environments, and fertilized these with nitrate and phosphate to favor bloom development. Our results showed fundamentally different TEP and DOC dynamics during the bloom. In all mesocosms, TEP concentration increased after nutrient exhaustion and accumulated steadily until the end of the study. TEP concentration was closely related to the abundance of E. huxleyi and accounted for an increase in POC concentration of 35 ± 2% after the onset of nutrient limitation. The production of TEP normalized to the cell abundance of E. huxleyi was highest in the Year 2100 treatment. In contrast, DOC concentration exhibited considerable short-term fluctuations throughout the study. In all mesocosms, DOC was neither related to the abundance of E. huxleyi nor to TEP concentration. A statistically significant effect of the CO2 treatment on DOC concentration was not determined. However, during the course of the bloom, DOC concentration increased in 2 of the 3 Year 2100 mesocosms and in 1 of the present mesocosms, but in none of the glacial mesocosms. It is suggested that the observed differences between TEP and DOC were determined by their different bioavailability and that a rapid response of the microbial food web may have obscured CO2 effects on DOC production by autotrophic cells. KEY WORDS: Emiliana huxleyi · Transparent exopolymer particles · TEP · Dissolved organic carbon · DOC · Carbon overconsumption · CO2 · Redfield ratios · Mesocosms Full article in pdf format PreviousExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 34, No. 1. Online publication date: January 16, 2004 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2004 Inter-Research.

Production of transparent exopolymer particles (TEP) by phyto- and bacterioplankton

Transparent exopolymer particles (TEP) exist abundantly in oceans and lakes and have been found to play an important role for sedimentation and biochemical cycling of matter. But the origin of these particles and the factors regulating their formation are not well understood. This study examined several strains of algae and bacteria with respect to their production of TEP or TEP-precursors. The formation rate of TEP in batch cultures of algae varied widely between species, and interspecies variability between diatoms was as large as that between species belonging to different classes or even divisions. Species, growth phase and environmental factors acted in concert in determining the accumulation of TEP in algal cultures and no general rules or patterns could be derived. The concentration of TEP during the growth phase of algal batch cultures, mesocosm or natural phytoplankton blooms was a significant function of chl. a, confirming the significance of phytoplankton for the formation of TEP. Experiments with three bacterial strains and a natural bacteria population indicated, that bacteria are also able to generate TEP, but the role of bacterial derived TEP for in situ TEP concentrations remains unclear.

Direct relationship between CO2 uptake and transparent exopolymer particles production in natural phytoplankton

Incubation experiments with natural phytoplankton revealed a relationship between CO2 concentration and the production of transparent exopolymer particles (TEP), with TEP production being linearly related to theoretical CO2 uptake rates.

Seasonal variations in phytoplankton composition and transparent exopolymer particles in a eutrophicated coastal environment

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 30:69-82 (2002) - doi:10.3354/ame030069 Seasonal variations in phytoplankton composition and transparent exopolymer particles in a eutrophicated coastal environment Neelam Ramaiah*, Ken Furuya Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, Tokyo 113-8657, Japan *Present address: SAD 35, NIO Quarter, Dona Paula, Goa 403 004, India. Email: ramaiah@darya.nio.org ABSTRACT: Annual variations in phytoplankton composition and concentrations of transparent exopolymer particles (TEP) were studied in Tokyo Bay, one of the most eutrophicated coastal environments in central Japan. This study aimed at evaluating the influence of anthropogenic input on phytoplankton composition, bloom formations and their subsequent impact on TEP concentrations. Phytoplankton composition was dominated by diatoms, particularly Skeletonema costatum, during most of the year. However, raphidophytes represented by Heterosigma akashiwo became abundant from late spring to summer. TEP concentrations varied between 14 and 1774 μg Xanthan equiv. l-1, with higher values in the inner bay (169 ± 182 μg Xanthan equiv. l-1, which in terms of carbon is equivalent to 118 ± 127 μg l-1) than the bay mouth (112 ± 70 μg Xanthan equiv. l-1, ≅78 ± 49 μgC l-1). TEP concentrations followed an empirical relationship with chlorophyll a. In addition, peak TEP coincided with the peak chlorophyll a and raphidophyte abundance. Multivariate analysis between TEP and the different groups of phytoplankton indicated a predominant influence of diatoms and raphidophytes. TEP-carbon percent of chlorophyll-carbon tended to be higher during winter, which coincided with low bacterial counts and implied low or no utilization of TEP and hence an accumulation during such periods. Laboratory experiments were conducted with cultures of S. costatum and H. akashiwo to test the species-specific variation, if any, in total organic carbon (TOC) production and TEP formation. The consistently higher chlorophyll equivalent TEP production in H. akashiwo confirmed our hypothesis that, in addition to well-known contributions by diatoms, groups like the raphidophytes contribute substantially to TEP as well as organic matter production in eutrophicated coastal regions. TOC and TOC equivalent TEP production revealed that, in addition to the biomass and composition, the growth stage(s) of the phytoplankton is an important factor controlling the C-rich TEP concentrations in aquatic ecosystems subjected to anthropogenic perturbances. KEY WORDS: TEP · Phytoplankton blooms · Heterosigma · Eutrophic Tokyo Bay Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 30, No. 1. Online publication date: November 27, 2002 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2002 Inter-Research.