Dissolved Carbohydrate Concentrations Research Articles

Seasonal variations and distributions of dissolved free and total carbohydrates at the İzmir Bay, Aegean Sea

Seasonal variations and distributions of dissolved carbohydrate concentrations at the Izmir Bay were investigated with salinity, chlorophyll a (Chl a), and dissolved organic carbon (DOC) levels to understand their relationships. Samples were collected from surface, subsurface and bottom depths at seven stations. DOC concentrations ranged from 32.2 to 244.2 µmol/L, and in general, DOC levels increased from winter to summer, then slightly decreased in autumn. Monosaccharide (MCHO), polysaccharide (PCHO) and total dissolved carbohydrate (TDCHO) levels were found between 0.7–8.3, 0.7–19.5, and 2.6–24.6 µmol/L. DOC, MCHO, PCHO and TDCHO levels were found higher in middle-inner bays, under the influence of anthropogenic inputs, compared to outer bay. Seasonal changes of MCHO/DOC, PCHO/DOC and TDCHO/DOC ratios were statistically significant (p<0.05) and the ratios showed decrease trends from winter to summer-autumn seasons. Distributions of TDCHO/DOC ratios at wide ranges (2.5%–42.3%) indicated the presence of newly forming and degrading fractions of DOM. According to results of factor analysis, Chl a, MCHO and TDCHO were explained in the same factor groups. In conclusion, the results showed that dissolved carbohydrate levels in the Izmir Bay might be influenced by biological processes and terrestrial/anthropogenic inputs.

Microbial activities and organic matter degradation at three sites in the coastal North Atlantic: Variations in DOC turnover times and potential for export off the shelf

The Mid-Atlantic Bight is a highly productive region where considerable quantities of organic matter are processed, transformed, and respired. Much of this organic matter is in the form of dissolved organic carbon (DOC). We investigated the activities of heterotrophic microbial communities responsible for DOC processing at three sites in the coastal Mid-Atlantic Bight/northern end of the South Atlantic Bight: near the Chesapeake Bay mouth, off Cape Hatteras, and near Cape Lookout, NC. Activities of endo- and exo-acting extracellular enzymes (polysaccharide hydrolases, and glucosidase and peptidases, respectively), and bacterial protein production were measured in surface and subsurface waters at the three stations. Total suspended material, cell counts, and particle-associated enzyme activities were also quantified. Water masses at each station showed distinct physical characteristics (temperature, salinity, total suspended material), and differed notably in rates and spectrum of enzyme activities, as well as in the fraction of particle-associated activities. Despite similar cell counts, bacterial productivity differed by a factor of ca. 30 among depths and stations. Glucosidase and peptidase activities differed by a factor of ca. 40 among stations, but the differences in enzyme activities among stations did not scale with the differences in bacterial productivity. Theoretical turnover times of dissolved carbohydrates – calculated from total dissolved carbohydrate concentrations and polysaccharide hydrolase activities – range from weeks to months, suggesting that dissolved carbohydrates may be among the components of DOC that can be advected from the Mid-Atlantic Bight into the open ocean, connecting the carbon cycle in the ocean margin with the ocean's interior.

Distributions of dissolved monosaccharides and polysaccharides in the surface microlayer and surface water of the Jiaozhou Bay and its adjacent area

Sea surface microlayer (SML) samples and corresponding bulk surface water (SW) samples were collected in the Jiaozhou Bay and its adjacent area in July and November 2008. The average concentrations of dissolved monosaccharides (MCHO) and polysaccharides (PCHO) revealed similar temporal variability, with higher concentrations during the green-tide period (in July) than during the non-green-tide period (in November). Average enrichment factors (EF) of MCHO and PCHO, defined as the ratio of the concentration in the SML to that in the SW, were 1.3 and 1.4 in July, respectively, while those values in November were 1.9 and 1.6. Our data also showed that the concentrations of MCHO and PCHO in the SML were strongly correlated with those in the SW, indicating that most of the organic materials in the SML came from the SW. The total dissolved carbohydrate concentrations (TDCHO) in the bulk surface water were closely correlated with salinity during the cruises (July: r=−0.580, n=18, P=0.01; November: r=−0.679, n=26, P<0.001), suggesting that riverine input had an important effect on the distribution of TDCHO in surface seawater of the study area.

Organic Carbon Degradation in Arctic Marine Sediments, Svalbard: A Comparison of Initial and Terminal Steps

Degradation of marine organic matter under anoxic conditions involves microbial communities working in concert to remineralize complex substrates to CO 2 . In order to investigate the coupling between the initial and terminal steps of this sequence in permanently cold sediments, rates of extracellular enzymatic hydrolysis and sulfate reduction were measured in parallel cores collected from 5 fjords on the west and northwest coast of Svalbard, in the high Arctic. Inventories of total dissolved carbohydrates were also measured in order to evaluate their potential role in carbon turnover. Polysaccharide hydrolysis rates exhibited substrate-related and, to a lesser extent, depth-related differences (p < 0.0001); laminarin hydrolysis was consistently most rapid at nearly all depths and sites, and fucoidan hydrolysis was least rapid. Although there was a high degree of variability in parallel cores, sulfate reduction rates also exhibited statistically significant depth-and station-related differences. A comparison with data from previous investigations in Svalbard sediments suggests that this variability is linked to substrate availability rather than to organism distribution. Total dissolved carbohydrate concentrations were comparable to those measured in more temperate sediments, and likely comprise a considerable fraction of porewater dissolved organic carbon. A comparison of dissolved carbohydrate inventories with hydrolysis and sulfate reduction rates suggests that the turnover of carbon through the dissolved pool occurs quite rapidly, on the order of a few days to weeks. The transformation of particulate to dissolved organic matter must also be sufficiently rapid to maintain the measured rates of terminal remineralization.

Formation of transparent exopolymeric particles (TEP) from macroalgal detritus

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 282:1-12 (2004) - doi:10.3354/meps282001 Formation of transparent exopolymeric particles (TEP) from macroalgal detritus Daniel C. O. Thornton* Integrative Biology Group, Darwin Building, School of Health, Natural and Social Sciences, University of Sunderland, Sunderland SR1 3SD, UKPresent address: Department of Oceanography, Texas A&M University, 3146 TAMU, College Station, Texas 77843-3146, USA *Email: dthornton@ocean.tamu.edu ABSTRACT: Detritus derived from macroalgae often accumulates in the littoral and sublittoral of temperate shores. Experiments were conducted to test the hypothesis that macroalgal detritus is a source of transparent exopolymer particles (TEP). Macroalgal detritus was incubated in artificial seawater media under various experimental conditions. TEP concentrations were found to be proportional to the concentration of macroalgal detritus; however, dissolved carbohydrate concentrations were not related to detritus concentration. As TEP concentration did not increase over time, it was probably washed off the detritus when it was initially placed in the media. However, higher concentrations of TEP (262 µg Gum Xanthan equivalent [g detritus]-1) were produced if inorganic nutrients were added to the media compared to controls (75 µg Gum Xanthan equivalent [g detritus]-1). Dissolved carbohydrate and TEP concentrations increased with incubation temperature. TEP did not form abiotically from carbohydrate precursors derived from macroalgal detritus, indicating that microbial activity was important in their formation. TEP from macroalgal detritus will result in a flux of small, sticky particles into the water column which may subsequently affect the aggregation of both biotic and abiotic particles. This will affect both biogeochemical nutrient cycling in coastal waters and food web dynamics. KEY WORDS: Transparent exopolymer particles · TEP · Macroalgae · Detritus · Carbohydrate · Biogeochemistry · Coastal waters Full text in pdf format NextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 282. Online publication date: November 16, 2004 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2004 Inter-Research.

Carbohydrate dynamics and contributions to the carbon budget of an organic-rich coastal sediment

Potential hydrolysis rates of three different polysaccharides, pullulan, laminarin, and xylan, were measured in intact sediment cores from Cape Lookout Bight, North Carolina, in order to constrain the rates at which a fraction of the high-molecular-weight sedimentary carbon pool may be hydrolyzed to lower molecular weights. Potential hydrolysis rates of pullulan were somewhat higher than those of laminarin and xylan. Highest potential rates were measured in surface sediments; rates at depths of 5–7 and 14–16 cm differed relatively little from one another. Total dissolved carbohydrates, dissolved organic carbon (DOC), sulfate, and sulfate reduction rates were also measured and compared with data previously collected at Cape Lookout Bight in order to investigate carbohydrate dynamics and establish the relative contribution of carbohydrates to the sedimentary carbon budget. Total porewater carbohydrates constitute a disproportionate fraction of DOC, ranging from a maximum of 85% in near-surface intervals to 24% at depths of 14–16 cm. A comparison of potential hydrolysis rates, dissolved carbohydrate concentrations, DOC, and sulfate reduction rates, along with results from a wide range of studies previously conducted at this site suggests that hydrolysis of high-molecular-weight polysaccharides can potentially be very rapid relative to carbon remineralization rates. Dissolved porewater carbohydrates form a dynamic pool that is likely turned over on short timescales in Cape Lookout Bight sediments.

The role of particulate carbohydrate exudates in the flocculation of diatom blooms

Diatom blooms are frequently terminated by mass aggregation of cells into large, rapidly sinking aggregates. It has been hypothesized that transparent exopolymer particles (TEP), abundant particles formed from the polysaccharides exuded by living cells, may be essential for this mass flocculation processes. We investigated the abundance of TEP and their role in the aggregation of diatoms in laboratory cultures and during a natural diatom bloom off California. TEP and dissolved carbohydrates accumulated appreciably over the growth cycle of Chaetoceros gracilis in the laboratory. The flocculation of C. gracilis in a laboratory flocculator was dominated by TEP, not cells, and large flocs, consisting predominantly of particulate polysaccharides, formed at a rate more than an order of magnitude higher than predicted by coagulation theory for cells alone. The frequency of interparticle attachment was three orders of magnitude higher for TEP than for cells. The pattern of flocculation of a natural diatom bloom was similar to that of laboratory cultures. Prior to bloom flocculation the abundance and total quantity of TEP and the concentration of particulate carbohydrates increased, while dissolved carbohydrate concentrations decreased. During the flocculation stage TEP aggregated into fewer, but much larger particles and concentrations of dissolved carbohydrates decreased further. The percentage of diatom cells which were attached to TEP increased during the flocculation period from 3 to 90% and TEP formed the matrix of all the natural diatom aggregates observed. During the late flocculation stage the quantity of TEP and TEP aggregates did not increase further and concentrations of diatoms decreased, presumably because large flocs sank out. Our findings indicate that TEP should be included in models of particle aggregation in the ocean. The abundance, large size and high sticking coefficient of TEP make them essential to the aggregation of diatom blooms. The extracellular release of polysaccharides by growing cells may be an adaptation for aggregation. The abiotic formation of particulate organic matter (TEP) from dissolved organic matter (DOC) may help to explain the extremely high turnover rates of DOC observed during blooms.

Dissolved Carbohydrate Distribution and Dynamics in Two Southeastern United States Reservoirs

Dissolved carbohydrate concentrations were measured in the waters of two southeastern United States reservoirs (Pond B and Par Pond) in 1982 and 1983 with attention to the influence of rooted aquatic macrophytes, spatial and temporal variability, and depth. Mean concentrations for all sampling locations were 2.86 ± 1.01 mg∙L−1 in Pond B and 1.72 ± 1.24 mg∙L−1 in Par Pond. There were no consistent spatial or temporal differences within a reservoir, nor were there consistent differences between macrophyte beds and open waters in either impoundment. Dissolved carbohydrate concentrations increased in both reservoirs during the day, reaching maxima in late afternoon, with an accompanying decrease in the dissolved organic carbon (DOC). The dissolved carbohydrates comprised 5.8–20.2% of the DOC in Par Pond and 25.7–42.3% of the DOC in Pond B. In both reservoirs, vertical profiles show the presence of carbohydrates at all depths during aerobic and anaerobic conditions. Midwater concentration maxima were present in Par Pond during periods of holomixis and stratification. The maxima were coincident with an intense pycnocline during periods of stratification; but during holomixis, the maximum was apparently unsupported by physical structure.

Dependence of dissolved carbohydrate concentrations upon small scale nanoplankton and bacterioplankton distributions in the western Sargasso Sea

Significant correlations between trophic components of the <20 μm microbial plankton and the concentrations of total dissolved carbohydrate (TCHO) and polysaccharide (PCHO) have been found at two drogued buoy stations which were sampled at 3 or 4-h intervals over diel cycles. An attempt was made to sample on two pre-selected isotherms (approximating isopycnals) at each station. Significant inverse correlations of TCHO and of PCHO with numbers of phototrophic nanoplankton (PNAN) were found along both isotherms at a station off the Carolina coast. Off central Florida, TCHO and/or PCHO were significant multiple linear functions of PNAN, heterotrophic bacterioplankton (BAC) and sometimes heterotrophic nanoplankton (HNAN) counts. Partial regression coefficients for PNAN were always negative and those for HNAN were positive. Inverse trends dominated the relations of BAC with PCHO and TCHO. The combined data from the two stations (300 nautical miles apart) produced very similar multiple linear relations. This suggests that the observed relationships are real, resulting from general physiological processes and interactions of the microbial plankton groups rather than from chance occurrences at a particular station, and that the combined activities of the <20 μm plankton actively regulate dissolved carbohydrate concentrations in the Sargasso Sea.