Ratio Of Particulate Organic Carbon Research Articles

Upper ocean export of particulate organic carbon in the Arabian Sea derived from thorium-234

Thorium-234 is used in the Arabian Sea as a tracer of sinking particle fluxes. Samples were collected from January to August 1995 on four cruises during the Northeast Monsoon, the Spring Intermonsoon and the mid- and late-Southwest Monsoon periods. In this study, 234Th activity distributions are used to quantify the 234Th flux on sinking particles, and the measured ratio of particulate organic carbon (POC) to particulate 234Th is used to convert from 234Th to POC export at 100 m. The calculated POC fluxes range from <1 to >25 mmols C m -2 d -1, and strong seasonal and spatial gradients are observed. The single largest feature is a basinwide export maximum associated with the late-SW Monsoon cruise when POC export rates are 17–28% of the observed primary production rates along the southern sampling line. During all other cruises, this export ratio is <2–10%, with an increase near shore where POC fluxes are generally elevated. Also, during the Spring Intermonsoon, a POC export maximum is observed along the northern sampling line. Both this Spring export feature and late-SW Monsoon flux maximum appear to be associated with a phytoplankton community structure dominated by diatoms. The timing of the late-SW Monsoon flux peak agrees with the observed flux maximum in the deep moored time-series sediment traps (Honjo et al., 1998). This dramatic increase in export between the mid- and late-SW Monsoon also corresponds to measured decreases in the stocks of total organic C in the upper 150 m (Hansell and Peltzer, 1998) and a sharp decline in surface water Al and Fe (Measures and Vink, 1998). These 100 m flux results, plus a series of POC flux profiles, allow for a more complete understanding of the magnitude and timing of sub-euphotic zone export in the Arabian Sea.

Enhanced microbial utilisation of dissolved amino acids indicates rapid modification of organic matter in the benthic boundary layer

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 156:43-50 (1997) - doi:10.3354/meps156043 Enhanced microbial utilisation of dissolved amino acids indicates rapid modification of organic matter in the benthic boundary layer Will Ritzrau1,*, Laurenz Thomsen2, Rubén J. Lara3, Gerhard Graf4 1Sonderforschungsbereich 313, Heinrich-Hecht-Platz 10, D-24118 Kiel, Germany 2GEOMAR, Wischhofstr. 1-3, D-24148 Kiel, Germany 3Zentrum für Marine Tropenökologie, Klagenfurter Str. 1, D-28359 Bremen, Germany 4Universität Rostock, Freiligrathstr. 7/8, D-18055 Rostock, Germany *E-mail: will@sfb313.uni-kiel.de Recent information on activity, abundance, and size of bacteria as well as concentration and composition of particles in the benthic boundary layer (BBL, range of water depths 191 to 479 m) was compared to the distribution of these parameters in 2 layers of the water column, the chlorophyll maximum layer (range of water depths 13 to 25 m) and the intermediate water depth (IWC, range of water depths 136 to 486 m). Microbial activities and concentrations of various biochemical parameters displayed distinct variation patterns in the BBL, exhibiting higher values compared to their variations in the chlorophyll maximum layer and the IWC. In the BBL the microbial utilisation of 14C-amino acids revealed no correlation with concentrations of particulate organic carbon (POC), but was related to chlorophyll a (chl a) equivalents and the ratio of POC and chl a equivalents. The distribution of dissolved free amino acids (DFAA) suggests that not necessarily the concentration but alternatively the accessibility (concentration and transport rate) of DFAA to bacteria determines heterotrophic activity. Results indicate that the BBL represents a distinct environment with rapid modification of organic matter prior to its final incorporation into the sediment. Benthic boundary layer · Microbial activity · Polynya Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 156. Publication date: September 25, 1997 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1997 Inter-Research.

The dynamics of CO 2 fixation in the Southern Ocean as indicated by carboxylase activities and organic carbon isotopic ratios

Recent studies have suggested that a direct relationship exists between the dissolved CO 2 concentration and the carbon isotopic composition of phytoplankton in the surface ocean. Thus, measurement of the δ 13C of planktonic organic matter in deep-sea cores can potentially yield a record of the past atmospheric CO 2 variations. However, we present here results from three cruises in the Indian and Atlantic sectors of the Southern Ocean (between 40 and 66°S) in which biochemical and physiological factors associated with photosynthetic processes lead to carbon isotopic fractionation by phytoplankton which cannot be directly related to variations within the mineral carbon pool. Simultaneous measurements of the carboxylase activities and the l3C/ l2C ratio of particulate organic carbon show that there is a large variability in phytoplankton carbon metabolism, especially on a seasonal scale, in spite of a relative uniformity of the environmental conditions. Phytoplankton carbon metabolism is clearly a main factor governing variations in the stable isotopic composition of organic matter in the euphotic layer. Interrelationships between light, Rubisco activity and δ 13C are clearly shown by our data. Heterotrophic processes also may influence the carbon isotope mass balance, especially during the break-up of the ice pack. In addition to the influence of photosynthetic metabolism, the effect of the meridional temperature gradient is also verified by our data set.

Laboratory investigations into the effect of marine organic material on the sea-salt aerosol generated by bubble bursting

A simple aerosol generation rig has been used to investigate the effect of marine organic material on the flux and inorganic particulate enrichment of marine aerosol. Aerosol was generated in the laboratory from UK coastal seawater samples collected on a monthly basis for 1 year, starting February 1988. Initial aerosol generation rates in the laboratory apparatus were typically between 0.3 and 1.0 ml min−1, dropping to a baseline value of around 0.1 ml min−1 after a prolonged period of bubbling. Initial aerosol generation rates showed no significant seasonal trend, whereas the total amount of aerosol generated before the rate fell to the baseline reached a plateau at around 60 ml from March to October, a factor of six greater than earlier in the year. Dissolved organic carbon (DOC) and surfactant activity have been measured in seawater from February 1988 to June 1990. The measurements show evidence of seasonal cycles for both determinands. Surfactant activity (expressed in equivalent units of the non-ionic model surfactant Triton X-100) shows a broad peak in the late autumn (2.5-3.2 mg l−1). Peak DOC concentrations were seen in early summer (1.9-3.4 mg Cl−1). It was also found that the surfactant-to-DOC ratio varies seasonally, which suggests that the DOC pool changes through the year. Neither initial aerosol generation rate nor total aerosol generated can be correlated with surfactant activity or DOC, although high surfactant levels can dramatically reduce both. Particulate organic carbon (POC) is highly variable (0.1-14 mg Cl−1), the ratio of POC to particulate loading being more useful. This ratio ranged from 15 to 4000 mg C g−1. Peak values may indicate biological production. Laboratory experiments investigating the aerosol enrichment of 3, 5 and 10 μm diameter synthetic silica particles were carried out at various seawater particulate loadings and surfactant activities. The enrichment factor (EF) of the particles was found to increase approximately linearly with surfactant activity. Particulate loading increases produced only a small increase in the uptake of silica particles in the aerosol, with EF remaining essentially constant. Varying the particle size appeared to have no effect on EF.

Subsurface chlorophyll maximum in the tropical and subtropical western Pacific Ocean: Vertical profiles of phytoplankton biomass and its relationship with chlorophylla and particulate organic carbon

Vertical distribution of phytoplankton biomass in terms of carbon content (PC) and its relationship with chlorophylla and particulate organic carbon (POC) were examined together with phytoplankton growth rates in the tropical and subtropical western Pacific in 1979, where a prominent subsurface chlorophyll maximum (SCM) developed between 65 and 150 m. Fluorescence microscopy combined with image analysis was used for measurement of cell volume which was converted to PC. The SCM coincided consistently with subsurface maximum of PC, and the SCM primarily reflected in situ accumulation of phytoplankton biomass. The PC:chlorophylla ratio decreased with depth; the ratio was 1.8 times, on average, higher in populations at the SCM compared to those near the surface. This increase in relative cellular chlorophylla along with depth accentuated the magnitude of the SCM. The PC:POC ratio was substantially lower near the surface, 0.17 on average, and increased sharply around the SCM, with a mean value of 0.53. Thus suspended particles around SCM were richer in phytoplankton than those in the upper layers. A major part of PC was contributed by autotrophic eukaryotes both near the surface and at the SCM, and prokaryotic picoplankton comprised a relatively small proportion (6.3 to 14.9%) of PC. The high phytoplankton biomass around the SCM was suggested to be ascribed to in-situ growth of phytoplankton.

Vertical Fine Structure of Particulate Matter and Nutrients in Sea Ice of the High Arctic

The vertical fine structure of particulate matter and inorganic nutrients through the bottom layers of sea ice was determined at a site in the Canadian high arctic. Intense vertical gradients of chlorophyll a, nitrate, ammonium, nitrite, phosphate, and silicate developed in the lower 6 cm of the ice as ice algae attained standing crops of 250 mg∙m−2 (up to 60 mg∙L−1) of chlorophyll a. Pigment and inorganic nutrient concentrations were closely correlated, and pools of inorganic nutrient were shown to exist in the particulate matter, suggesting that the extremely high dissolved nutrient concentrations in the bottom ice (e.g. up to 400 μmol∙L−1 nitrate) were derived at least in part from leakage of algal intracellular pools. Nitrogen and phosphorus were present in excess of algal needs, but silicon may not have been. The ratios of particulate organic carbon to chlorophyll a and to particulate organic nitrogen increased from the ice–water interface upwards, consistent with a physiological response of the ice algae to the strong corresponding gradient of light availability. Although spatially compact, the assemblage of algae in the bottom ice inhabits a highly stratified environment.

Time Series Analyses of Suspended Sediment Concentrations at North Inlet, South Carolina

Daily water samples have been collected at three stations in the North Inlet (South Carolina) marshestuary system since February 1981 as part of the NSF Long-Term Ecological Research (LTER) project. As a result of this sampling regime, nearly continuous time series of inorganic and organic suspended sediment, particulate organic carbon (POC), Secchi disk, salinity, and water temperature are now available. Power spectrum analysis of these data reveals that most of the explainable variance in the inorganic suspended sediment, POC, and Secchi disk data is related to a yearly cycle that is strongly coherent with water temperature such that high turbidity is associated with high water temperature. Only a small fraction of the explainable variance is associated with frequencies that can be related to the semidiurnal tide. Simple correlation analysis also indicates that turbidity is more closely associated with water temperature than with tide height or salinity. The ratio of POC to inorganic suspended sediment shows no discernible power spectra peaks and is weakly, but inversely, correlated with temperature. From these results we hypothesize that temperature-regulated bioturbation is the main factor controlling turbidity variations in the system. The lack of a strong inverse correlation between turbidity and salinity suggests that river runoff has little immediate impact on the suspended sediment of nearshore coastal waters in systems similar to North Inlet.

Stable isotope ratios of particulate organic carbon in surface water at inner part of Tokyo Bay

Stable isotope ratios of particulate organic carbon in surface water at inner part of Tokyo Bay

Suspended particulate organic material from hydrothermal vent waters at 21° N

Ocean floor spreading centres described recently consist of several sites with chemical and biological features unlike any oceanic sites previously known1–4. The high-pressure and warm-temperature regimes at these sites, coupled with dynamic hydrothermal water circulation, support biological communities that utilize a source of primary production which appears to be non-photosynthetic5. A detailed biochemical analysis of the suspended matter at a biologically-active site has been undertaken, with the goal of describing the relationship between microorganisms, benthic organisms and suspended particulate material within these hydrothermal systems. Suspended particulate matter from warm hydrothermal vent waters (5–38°C) of the East Pacific Rise1–4 (21° N, 106° W) was sampled on the OASIS expedition with an in situ pumping system in April 1982. Particulate organic carbon (POC) and nitrogen (PON) as well as individual organic compound classes from the lipid fraction were analysed to ascertain the sources and composition of the organic matter in this highly productive area. We show here that the particulate organic material (POM) of the vent water was both quantitatively and qualitatively different from the non-vent bottom water. The POC and PON measured within the vent and non-vent waters vary by a factor of 2–5, the higher values being in warm water. The organic matter in the non-vent water was found to be more resistant towards degradation or remineralization than in the vent water, as shown by the C:N ratio and the total lipid:POC ratio. Contributions to the lipid class compounds were assessed using well-known organic compound source biomarkers such as hydrocarbons, fatty alcohols, sterols, triacylglycerols and steryl and wax esters.

Chlorophyll a, Particulate Organic Carbon and Particulate Organic Nitrogen in Sessile Algal Communities of Nepalese Mountain Rivers

Amounts of chlorophyll a, particulate organic carbon and nitrogen of sessile algal communities in Nepalese mountain rivers were estimated. Samplings were performed at 34 points in the three main river systems of the east, middle and west Nepal from December 1978 to June 1979. Chlorophyll a amounts ranged from 1.3-189.6 mg·m-2 (average, 18.6). The ratio of particulate organic carbon (POC) to particulate organic nitrogen (PON) ranged from 5.8 to 22.1. High POC/PON ratios above 10 were obtained mainly from the samples of turbid rivers with water sources in the Inner Himalaya region.

Particulate protein in coastal waters, with special reference to seasonal variation

The quantities and the behavior of particulate proteinous carbon (PPC) were investigated at an experimental station in Funka Bay, southern Hokkaido from February 1974 to January 1975 using R. V. “Ushio Maru”. The amino acid composition of PPC, quantity of particulate organic carbon (POC), PPC:POC ratio, concentration of plant pigments and the primary productivity and heterotrophic activity in situ were measured to clarify PPC status. The net production was ca. 100 g C m-2 year-1. The inflow of Oyashio water and stagnation during early spring and summer may increase productivity. The net production during this period attained 70% of the net production for the whole year. The concentration of chlorophyll changed monthly parallel to changes in the primary production of the surface waters. The concentration of PPC and the PPC:POC ratio in the surface layer decreased gradually during the stagnation period of the Oyashio water. This implies that the PPC in the particulate organic matter was more easily consumed than the other organic constituents by the increased heterotrophic activity in summer. In contrast, low concentrations of PPC and high PPC:POC ratios were found during the stagnation period of Tsugaru warm water from autumn to winter. Concentrations of PPC and POC were not evenly distributed throughout the year; they decreased with depth during the stagnation period in summer. On the other hand, higher concentrations of PPC and POC, and an increased PPC:POC ratio were noted in samples collected near the sea bed, compared with the concentration and the ratio of the upper layer throughout the year. It seems likely that the particulate organic matter, originating from resuspension of bottom sediments containing proteins, was produced by the benthos. The turnover time of PPC in the upper layer was 7 to 11 days in summer and 45 to 100 days in winter; the turnover time for POC was 14 to 28 days in summer and 97 to 147 days in winter.

Seasonal cycles of hydrological events in Vellar Estuary : Jacob, J. and K. Rangarajan, 1962. Proc. First All-Ind., Cong. Zool., 1959, Sci. Pap., 2: 329–350. Also in: Annamalai Univ. Mar. Biol. Sta., Porto Novo, S. Ind., Publ. 1961–1962

Data are presented for particulate organic carbon (POC) and particulate nitrogen (PN) concentrations in the Humber Estuary and tidal River Ouse Estuary. The POC data were derived from approximately monthly surveys and are consistent with data reported for suspended particulate matter (SPM) in the non-tidal River Ouse (the freshwater river) and with SPM, or bed sediments, in estuarine ecosystems such as the Mississippi, Delaware, San Francisco Bay, Tolo Harbour, the Vellar Estuary and Cochin Backwater, as well as the Loire, Gironde, Ems and Tamar Estuaries. Relative to the dry weight of SPM, the Humber-averaged organic carbon and nitrogen percentages during the year February 1995–March 1996 were 2.6±0.6% (mean and S.D.) and 0.21±0.04%, respectively. The ratio of Humber-averaged POC to Humber-averaged PN was 13±3. Higher POC levels were observed near the Humber’s mouth and in the adjacent coastal zone during ‘bloom’ conditions, and in the upper estuarine reaches during large, winter and springtime freshwater inflows. At these times of high runoff, the POC content of SPM increased progressively up-estuary from the coastal zone to the tidal River Ouse. When inflows became very low, during late spring to early autumn of 1995, both the freshwater–saltwater interface (FSI) and the strengthening turbidity maximum (TM) moved further up-estuary and the POC content of SPM in the upper reaches of the Ouse became lower compared with that immediately down-estuary. This led to a poorly defined POC maximum near the confluence of the Humber, Ouse and Trent, before POC eventually decreased again towards the coastal zone. The lower POC contents in the upper estuarine reaches of the tidal Ouse may have been partly due to POC respiration by heterotrophic bacteria attached to SPM within the TM, consistent with the severe oxygen depletion observed there during high turbidity, summertime spring tides.