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1.
Primary productivity off Enshu-nada was measured by the13C method in September 1989. Primary productivity was estimated in a cold water mass developed off Enshu-nada for the first time. The obtained value was 469 mgC·m–2·d–1 and higher than those in the pelagic area of Kuroshio, but equivalent to those in the neritic and the Oyashio areas. It was indicated that cold water mass is the place where organic matter is produced actively. Extremely high chlorophylla of more than 5g·l–1 were found in the cold water mass. The high productivity was due to high standing crop of phyoplankton. Furthermore, calculated light efficiency and quantum yield showed consistent increase with depth and showed a maximum at 10% light level. Both were larger on the coastal side than those on the oceanic side of the Kuroshio current.  相似文献   

2.
Distribution and seasonal variability of dissolved organic carbon (DOC) and surface active substances (SAS) were studied along the depth profile (15 m) in a small eutrophicated and periodically anoxic sea lake (Rogoznica Lake, Eastern Adriatic coast) in 1996 and 1997. The range of DOC concentrations was characteristic for productive coastal marine ecosystems (60% of samples in the range of 1–2 mg l−1and 40% between 2 and 3 mg l−1). Distribution of SAS concentrations was uniform and shifted toward higher concentrations in comparison to other coastal areas in the Adriatic Sea. Eutrophication in the lake is generated by nutrient recycling under anaerobic conditions. Systematically higher concentrations of chlorophyll a, DOC and SAS were determined at the chemocline in the bottom layer (10–12 m) than in the upper water layer (0·5–2 m). Seasonal variability of organic matter was discussed regarding distributions of microphytoplankton (cells >20 μm) and photosynthetic pigments as well as oxygen and salinity changes along the depth profile. The dissolved oxygen saturation reaching up to 300% in the water layer between 8 m and 10 m depths in May and June 1996, was correlated with enhanced concentrations of phytoplankton biomass (reflected as chl a and b, fucoxanthin, peridinin, zeaxanthin) and increased concentrations of DOC and SAS.  相似文献   

3.
To clarify the beneficial roles of naturally occurring organic ligands on the growth of phytoplankton in newly upwelled water, phytoplankton culture experiments using disphotic zone water were conducted to discriminate between the effects of EDTA in the detoxification of certain toxic metal ions and increasing the availability of essential metals. Culture media were prepared by adding EDTA and Chelex-100, separately or in combination, to disphotic zone water samples. Our proposed working hypothesis is that phytoplankton growth can be enhanced by removing toxic metal ions from culture media by Chelex-100 and by detoxification of toxic metal ions or increasing the availability of essential metals by EDTA. A shortening of the lag period and an increase of the specific population growth rate were clearly observed after the addition of Chelex-100; nd EDTA. The effects of EDTA were more considerable than those of Chelex-100; a 17 to 44% in shortening the lag period and a 35 to 56% increase in the growth rate, when comparing the effects of Chelex-100 with those of EDTA. The similar effects of removing toxic metal ion by Chelex-100 as those of detoxification by EDTA suggested that EDTA has a role not only of detoxification but also of increasing the availability of essential metals. The present study suggests that the low productivity in newly upwelled water observed by Barber and Ryther (1969) can be ascribed to both toxic metal ions and a lack of available forms of essential metals because of their low contents of free natural organic ligands.  相似文献   

4.
The activity of234Th (t 1/2=24.1 days) in dissolved, particulate and sediment trap samples was determined in the water column off southwestern Taiwan during 2–4 October, 1993. Vertical234Th fluxes measured by the free-floating sediment traps ranged from 363 to 2290 dpm m–2 d–1 in the upper 450 m. Th-234 fluxes predicted from the irreversible scavenging model concur with those measured by the sediment traps. Comparison of the residence times of particulate234Th and particulate organic carbon showed that their respective values differ by a factor of approximately 23, which suggests organic carbon is preferentially recycled relative to234Th in the euphotic zone.  相似文献   

5.
Dissolved organic carbon (DOC), stable carbon isotopic (δ13C) compositions of DOC and particulate organic carbon (POC), and elemental C/N ratios of POC were measured for samples collected from the lower Mississippi and Atchafalaya rivers and adjacent coastal waters in the northern Gulf of Mexico during the low flow season in June 2000 and high flow season in April 2001. These isotopic and C/N results combined with DOC measurements were used to assess the sources and transport of terrestrial organic matter from the Mississippi and Atchafalaya rivers to the coastal region in the northern Gulf of Mexico. δ13C values of both POC (−23.8‰ to −26.8‰) and DOC (−25.0‰ to −29.0‰) carried by the two rivers were more depleted than the values measured for the samples collected in the offshore waters. Strong seasonal variations in δ13C distributions were observed for both POC and DOC in the surface waters of the region. Fresh water discharge and horizontal mixing played important roles in the distribution and transport of terrestrial POC and DOC offshore. Our results indicate that both POC and DOC exhibited non-conservative behavior during the mixing especially in the mid-salinity range. Based on a simple two end-member mixing model, the comparison of the measured DOC-δ13C with the calculated conservative isotopic mixing curve indicated that there was a significant in situ production of marine-derived DOC in the mid- to high-salinity waters consistent with our in situ chlorophyll-a measurements. Our DOC-δ13C data suggest that a removal of terrestrial DOC mainly occurred in the high-salinity (>25) waters during the mixing. Our study indicates that the mid- to high- (10–30) salinity range was the most dynamic zone for organic carbon transport and cycling in the Mississippi River estuary. Variability in isotopic and elemental compositions along with variability in DOC and POC concentrations suggest that autochthonous production, bacterial utilization, and photo-oxidation could all play important roles in regulating and removing terrestrial DOC in the northern Gulf of Mexico and further study of these individual processes is warranted.  相似文献   

6.
To unravel the factors that regulate DOC dynamics in the freshwater tidal reaches of the Schelde estuary, DOC concentration and biodegradability were monitored in the upper Schelde estuary and its major tributaries. Although the Schelde estuary possesses a densely populated and industrialized catchment, our data suggest that the bulk of DOC in the freshwater tidal reaches is not derived from waste water. This was concluded from the low biodegradability of DOC (on average 9%), DOC concentrations that are close to the mean for European rivers (4.61 mg l−1) and the absence of an inverse relationship between DOC and discharge. Most DOC originating from waste water being discharged in tributaries of the estuary appears to be remineralised before these tributaries reach the main estuary. Although dense phytoplankton blooms were observed in the upper estuary during summer (up to 700 μg chl a l−1), these blooms did not appear to produce large quantities of DOC in the freshwater tidal reaches as DOC concentrations were low when phytoplankton biomass was high. The fact that DOC concentrations were high in winter and decreased in summer suggests a predominantly terrestrial source of DOC in the freshwater tidal reaches of the Schelde estuary.  相似文献   

7.
Phytoplankton communities, production rates and chlorophyll levels, together with zooplankton communities and biomass, were studied in relation to the hydrological properties in the euphotic zone (upper 100 m) in the Cretan Sea and the Straits of the Cretan Arc. The data were collected during four seasonal cruises undertaken from March 1994 to January 1995.The area studied is characterised by low nutrient concentrations, low 14C fixation rates, and impoverished phytoplankton and zooplankton standing stocks. Seasonal fluctuations in phytoplankton densities, chlorophyll standing stock and phytoplankton production are significant; maxima occur in spring and winter and minima in summer and autumn. Zooplankton also shows a clear seasonal pattern, with highest abundances occurring in autumn–winter, and smallest populations in spring–summer. During summer and early autumn, the phytoplankton distribution is determined by the vertical structure of the water column.Concentrations of all nutrients are very low in the surface waters, but increase at the deep chlorophyll maximum (DCM) layer, which ranges in depth from about 75–100 m. Chlorophyll-a concentrations in the DCM vary from 0.22–0.49 mg m−3, whilst the surface values range from 0.03–0.06 mg m−3. Maxima of phytoplankton, in terms of cell populations, are also encountered at average depths of 50–75 m, and do not always coincide with chlorophyll maxima. Primary production peaks usually occur within the upper layers of the euphotic zone.There is a seasonal succession of phytoplankton and zooplankton species. Diatoms and ‘others’ (comprising mainly cryptophytes and rhodophytes) dominate in winter and spring and are replaced by dinoflagellates in summer and coccolithophores in autumn. Copepods always dominate the mesozooplankton assemblages, contributing approximately 70% of total mesozooplankton abundance, and chaetognaths are the second most abundant group.  相似文献   

8.
Dissolved Fe and ligand concentrations and the Fe-binding strength of the organic ligands were measured in samples from the upper water column (150 m) of the oligotrophic waters of the Canary Basin (eastern North Atlantic Ocean). Concentrations of major nutrients, phytoplankton abundance and photosynthetic characteristics were also measured in the same samples.The concentrations of dissolved Fe and dissolved organic ligands were low with mean values of 0.31 ± 0.18 nM Fe and 1.79 ± 0.73 nEq of M Fe(n = 47), respectively. The conditional binding constant varied between 1019.8–1022.7 (n = 47). The largest variation with depth in the ligand concentrations (between 4.78 and 1.1 nEq of M Fe) was observed in the upper layer, above the Deep Chlorophyll Maximum (DCM located between 80 and 100 m), with high surface values in stations at 18 and 34.At the DCM where Fe was depleted, the ligand concentrations were still relatively high showing the same trend with depth as the amount of phytoplankton cells. Here 62% of the vertical variation in ligand concentrations can be explained by parameters describing phytoplankton cell abundance or biomass and orthosilicic acid concentration, which could reflect diatom growth. Ligand concentrations below the maximum of the DCM (n = 4) showed good linear positive relationships with the total phytoplankton biomass as well as with 2 out of 4 distinguished groups of phytoplankton (Synechococcus and pico-eukaryote I).In the maximum of the DCM and below this maximum the phytoplankton origin of the dissolved organic ligands of Fe is very probable. Data suggest a release of ligands by cell lysis and not by an active production. However, the origin in the surface layer is more difficult to explain. Although the amount of phytoplankton cells in the surface layer is reduced, it is still  25% of the cell concentration observed in the DCM. High concentrations of organic ligands could then be a remnant of past blooms or present production under nutrient depleted conditions. Input of Sahara dust can be another source of ligands.  相似文献   

9.
We describe an investigation into the reactivity of dissolved organic carbon (DOC), produced from marine algae, to conventional persulphate and ultraviolet (UV) oxidation methods. Marine algae were grown in batch culture in the presence of 14C bicarbonate and filtered samples of the phytoplankton dissolved organic carbon (PDOC) were oxidized with persulphate and UV techniques. The amount of fixed label found in solution after the oxidation procedures was compared with the initial amount of labelled DOC. Marine algae examined in this way included: the diatoms, Chaetoceros gracilis, Skeletonema costatum, Phaeodactylum tricornutum; the flagellate, Isochrysis galbana; and the cyanobacterium, Synechococcus strain DC2. It was found that 5–18% of the DOC produced by these phytoplankton resisted persulphate oxidation. Samples were also measured for their resistance to UV oxidation by an autoanalyzer method. It was found that 15–27% of these samples resisted UV oxidation. However, 95% of PDOC was oxidized after exposure for 6 h to high intensity UV irradiation using a variable exposure time system. P. tricornutum and Synechococcus PDOC samples were ultrafiltered into low molecular weight (< 10 000 Da) and colloidal (> 10 000 Da) size fractions. Both species produced mainly (> 68%) low molecular weight material. Slightly greater resistance to persulphate oxidation was generally found for the colloidal Synechococcus PDOC (15–22%) than for the low molecular weight material (14–17%). However, the opposite was found for the P. tricornutum PDOC which generally showed less resistance for the colloidal fraction (5–12%) than for the low molecular weight fraction (10–15%).Experiments were also conducted to determine the effects of short-term (days) and long-term (months) ageing of PDOC solutions in the presence of microbial populations from coastal seawater. Long-term ageing decreased the amount of PDOC that resisted oxidation in all cases. However, the fraction of PDOC resisting persulphate oxidation increased by small amounts over a short-term experiment. Increased resistance was attributed to preferential degradation of biologically and chemically labile components of PDOC by bacteria.The percentages of phytoplankton-produced (and microbially aged) DOC found in this study to resist UV or persulphate oxidation were low (5–27%), compared with those values (50–65%) reported for DOC in surface seawater on the basis of recent high temperature catalytic oxidation analyses.  相似文献   

10.
The study on dissolved organic ligands capable to complex copper ions (LT), surface-active substances (SAS) and dissolved organic carbon (DOC) in the Northern Adriatic Sea station (ST 101) under the influence of Po River was conducted in period from 2006–2008. The acidity of surface-active organic material (Acr) was followed as well. The results are compared to temperature and salinity distributions. On that way, the contribution of the different pools of ligands capable to complex Cu ions could be determined as well as the influence of aging and transformation of the organic matter. The LT values in the investigated period were in the range of 40–300 nmol l−1. The range of DOC values for surface and bottom samples were 0.84–1.87 mg l−1 and 0.80–1.30 mg l−1, respectively. Total SAS concentrations in the bottom layer were 0.045–0.098 mg l−1 in equiv. of Triton-X-100 while those in the surface layer were 0.050–0.143 mg l−1 in equiv. of Triton-X-100. The majority of organic ligands responsible for Cu binding in surface water originate from new phytoplankton production promoted by river borne nutrients. Older, transformed organic matter, possessing higher relative acidity, is the main contributor to the pool of organic ligands that bind copper in the bottom samples. It was estimated that 9% of DOC in surface samples and 12% of DOC in the bottom samples are present as ligands capable to complex copper ions.  相似文献   

11.
Sources and discharges of dissolved organic carbon (DOC) from the central Sumatran river Siak were studied. DOC concentrations in the Siak ranged between 560 and 2594 μmol l−1 and peak out after its confluence with the river Mandau. The Mandau drains part of the central Sumatran peatlands and can be characterized as a typical blackwater river due to its high DOC concentration, its dark brown-coloured, acidic water (pH 4.4–4.7) and its low concentration of total suspended matter (12–41 mg l−1). The Mandau supplies about half of the DOC that enters the Siak Estuary where it mixes conservatively with ocean water. The DOC input from the Siak into the ocean was estimated to be 0.3 Tg C yr−1. Extrapolated to entire Indonesia the data suggest a total Indonesian DOC export of 21 Tg yr−1 representing 10% of the global riverine DOC input into the ocean.  相似文献   

12.
Time-series measurements of temperature, salinity, suspended matter and beam attenuation coefficient () were measured at four hour intervals for about two days in June/ July 1982 in the middle shelf region and the coastal region of the southeastern Bering Sea. Current meters were also moored at the same locations.Depth-time distributions of indicated that profiles of suspended matter resulted from a combined process of resuspension of underlying sediments and sinking of suspended particles. Average-values for all measurements for particles revealed that the upward transport of particles due to resuspension formed a boundary layer, with a thickness apparently related to scalar speed. The average-profiles of the particle volume concentration were assumed to result from a balance between the sinking and diffusive flux of particles under a steady state, and the upward fluxes were calculated. Within the boundary layer, values of the upward fluxes of particulate organic matter linearly decreased with the logarithm of distance from the bottom. Fluxes of organic carbon at the upper edge of the boundary layer were 0.375 gC·m–2·day–1 in the middle shelf region (18 m above the bottom, bottom depth=78m) and 0.484gC·m–2·day–1 in the coastal region (25 m above the bottom, bottom depth=33m), and fluxes of nitrogen in both regions were 0.067 gN·m–2·day–1. The flux of organic carbon obtained in the middle shelf region (18 m above the bottom) agreed approximately with the flux (0.416 gC·m–2·day–1) calculated by substituting primary production data into the empirical equation of Suess (1980).  相似文献   

13.
The effects of tidal flushing on the abundance, productivity, and community structure of phytoplankton in response to eutrophication were examined every 2–3 months for more than 2 years in Tapong Bay, a tropical lagoon with only 1 tidal inlet connecting it to the sea in southern Taiwan. Water flushing time ranged from 4–12 d (8–25% d−1) in the outer region subject to fast flushing to 8–24 d (4–12% d−1) in the inner region subject to poor flushing. Chlorophyll a, cell number, and gross production (GP) rate of phytoplankton were significantly greater in the inner region than in the outer region. However, while GP rate was normalized by chlorophyll a (PB) and was expressed as photosynthetic intensity, no significant differences were detected among the study sites. These parameters exhibited a unimodal seasonal pattern across all study sites, with greater values in summer and lower values in winter. No significant differences in species richness or Shannon–Wiener diversity were detected among the study sites. Nevertheless, diversity indices were significantly higher in winter and lower in summer. Classification of phytoplankton communities showed that the grouping patterns were primarily determined by sampling time. Ordination by non-metric multidimensional scaling (MDS) revealed a clear temporal continuum of changes in species composition across all study sites, suggesting that the communities were primarily structured by time, but that it was little affected by study site. Analyses of similarities (ANOSIM) showed that phytoplankton communities sampled in winter could be separated from those in summer, but others were barely separable at all. In summer, the most frequently observed species were the diatom Skeletonema costatum and the cyanobacterium Oscillatoria sp., and these shifted to the diatoms S. costatum and Cylindrotheca closterium in winter. Our results suggest that tidal flushing is an important factor for regulating responses of phytoplankton abundance and productivity to eutrophication in tropical lagoons, but the community structure was little affected due to horizontal mixing by the tidal circulation.  相似文献   

14.
In this study, we examine the distribution and carbon stable isotope signature of dissolved organic carbon (DOC) and humic substances (HS) along a salinity gradient in the Altamaha and Satilla River estuaries. The maximum DOC concentrations in the Altamaha and Satilla were 10 and 29 mg C l−1, respectively, though concentrations were similar at the mouth of both estuaries. There was a decrease in HS content of DOC from 50 to 80% at the head of the estuaries to 10% at salinities higher than 30‰. The δ13C DOC varied between −25.5 and −19‰ and between −27 and −21‰ in the Altamaha and Satilla estuaries, respectively. The tendency towards more depleted δ13C DOC in the Satilla, especially in the lower salinity portion of this estuary, suggests greater terrestrial inputs in the Satilla than in the Altamaha. Seasonal fluctuations were observed in the form of increased (two to three times) range in DOC concentration, heavier δ13C DOC and increased proportion of estuarine–marine-derived DOC (average enrichment of δ13C DOC from +1 to +2) during low river flow (July–October). The δ13C HS in both rivers showed a similar trend, but was consistently more depleted than DOC, with an average range from −28 to −24.5‰. This suggests that HS have larger proportions of terrestrial components (a maximum of >60% at the mouth of the estuary) than DOC. The less depleted δ13C values of DOC in comparison with HS indicate a different source for the non-humic (non-HS) component of DOC (range in δ13C non-HS, −22 to −16‰). That source could either be the decomposition of detrital material derived from saltmarsh environments or microalgal-derived DOC of estuarine or marine origins.  相似文献   

15.
Distribution of particulate organic carbon (POC) and dissolved organic carbon (DOC) in seawater, and chemical composition of surficial sediments were studied in relation to pulpmill effluent and dumping of dredge spoil containing wood debris in Alberni Inlet, British Columbia, Canada. The maximum concentration of POC (377–584µg Cl–1) was observed at the surface around the dumping area (5–7 km seaward of the inlet's head), and at the location immediately adjacent to the dump site POC was elevated throughout the water column (50 m). While POC tended to decrease in the surface layer for a distance of about 25km down-inlet, measureable effects of POC in the deeper water did not extend beyond 600m from the dump site. The dump site was conspicuous by the large maximum in C:N ratio (46.3). In contrast, DOC was observed to be highest (4.25mg Cl–1) at the head of the inlet where pulpmill effluent was being discharged and a secondary maximum was found about 10km down-inlet from the dump site. The data suggest that a considerable proportion of the dredge spoil sinks rapidly near the dump site, probably within several hundred metres. Some of the spoil, perhaps low density wood debris may travel considerably further with the surface water where by leaching it may contribute to some extent to the surface DOC before sinking into deeper water.  相似文献   

16.
As part of E-Flux III cruise studies in March 2005, we investigated phytoplankton community dynamics in a cyclonic cold-core eddy (Cyclone Opal) in the lee of the Hawaiian Islands. Experimental incubations were conducted under in situ temperature and light conditions on a drift array using a two-treatment dilution technique. Taxon-specific estimates of growth, grazing and production rates were obtained from analyses of incubation results based on phytoplankton pigments, flow cytometry and microscopy. Cyclone Opal was sampled at a biologically and physically mature state, with an 80–100 m doming of isopycnal surfaces in its central region and a deep biomass maximum of large diatoms. Depth-profile experimentation defined three main zones. The upper (mixed) zone (0–40 m), showed little compositional or biomass response to eddy nutrient enrichment, but growth, grazing and production rates were significantly enhanced in this layer relative to the ambient community outside of the eddy. Prochlorococcus spp. dominated the upper mixed layer, accounting for 50–60% of its estimated primary production both inside and outside of Opal. In contrast, the deep zone of 70–90 m showed little evidence of growth rate enhancement and was principally defined by a 100-fold increase of large (>20-μm) diatoms and a shift from Prochlorococcus to diatom dominance (80%) of production. The intermediate layer of 50–60 m marked the transition between the upper and lower extremes but also contained an elevated biomass of physiologically unhealthy diatoms with significantly depressed growth rates and proportionately greater grazing losses relative to diatoms above or below. Microzooplankton grazers consumed 58%, 65% and 55%, respectively, of the production of diatoms, Prochlorococcus and the total phytoplankton community in Cyclone Opal. The substantial grazing impact on diatoms suggests that efficient recycling was the major primary fate of diatom organic production, consistent with the low export fluxes and selective export of biogenic silica, as empty diatom frustules, in Cyclone Opal.  相似文献   

17.
During France JGOFS campaign ANTARES 2 (R.V. Marion Dufresne), samples were taken along a section of the 62°E meridian from 49° to 66°S. The high temperature catalytic oxidation (HTCO) method was used to determine the concentration of dissolved organic carbon (DOC). The analyses were conducted both on-board ship and after the cruise in the laboratory. Collecting and storing acidified samples for post-cruise analysis induced no significant differences. The use of two separate but identical channels on the carbon analyzer increased the number of samples analysed per day and allowed independent monitoring of the instrument blank and the calibration of the detector response. The mixed layer concentrations of organic carbon varied from about 52 μM C in the Antarctic Divergence (64°S) to about 63 μM C in the Polar Frontal Zone (49°S). Vertical profiles showed a slight, but significant, decrease in organic carbon below the mixed layer, to about 42 μM C below 2000 m across the transect. The homogeneity and low concentration of organic carbon in deep water is consistent with values recently reported for the equatorial Atlantic and Pacific Ocean and supports the evidence for a constant deep water DOC concentration. In addition, this provides a verification of the instrument performance, thus validating observed DOC data trends and allowing a comparison with the ‘modern' DOC literature. In general, the organic carbon concentration in the mixed layer was lower than previously published data of the main ocean basins, which might -reflect the low chlorophyll a concentration (<0.5 μg/l) encountered in this region. Along the 62°E meridian section, organic carbon showed a trend with corresponding measurements of phytoplankton biomass and bacterial production, underlining the dependence of bacterial growth on a pool of ‘freshly' produced DOC. Organic carbon was found to exhibit a weak inverse trend versus apparent oxygen utilization (AOU). This suggests that only a small part of the oxygen consumption is due to the mineralisation of DOC.  相似文献   

18.
The sources and distribution of organic matter (OM) in surface waters and sediments from Winyah Bay (South Carolina, USA) were investigated using a variety of analytical techniques, including elemental, stable isotope and organic biomarker analyses. Several locations along the estuary salinity gradient were sampled during four different periods of contrasting river discharge and tidal range. The dissolved organic carbon (DOC) concentrations of surface waters ranged from 7 mg l−1 in the lower bay stations closest to the ocean to 20 mg l−1 in the river and upper bay samples. There was a general linear relationship between DOC concentrations and salinity in three of the four sampling periods. In contrast, particulate organic carbon (POC) concentrations were significantly lower (0.1–3 mg l−1) and showed no relationship with salinity. The high molecular weight dissolved OM (HMW DOM) isolated from selected water samples collected along the bay displayed atomic carbon:nitrogen ratios ([C/N]a) and stable carbon isotopic compositions of organic carbon (δ13COC) that ranged from 10 to 30 and from −28 to −25‰, respectively. Combined, such compositions indicate that in most HMW DOM samples, the majority of the OM originates from terrigenous sources, with smaller contributions from riverine and estuarine phytoplankton. In contrast, the [C/N]a ratios of particulate OM (POM) samples varied significantly among the collection periods, ranging from low values of 5 to high values of >20. Overall, the trends in [C/N]a ratios indicated that algal sources of POM were most important during the early and late summer, whereas terrigenous sources dominated in the winter and early spring.In Winyah Bay bottom sediments, the concentrations of the mineral-associated OM were positively correlated with sediment surface area. The [C/N]a ratios and δ13COC compositions of the bulk sedimentary OM ranged from 5 to 45 and from −28 to −23‰, respectively. These compositions were consistent with predominant contributions of terrigenous sources and lesser (but significant) inputs of freshwater, estuarine and marine phytoplankton. The highest terrigenous contents were found in sediments from the river and upper bay sites, with smaller contributions to the lower parts of the estuary. The yields of lignin-derived CuO oxidation products from Winyah Bay sediments indicated that the terrigenous OM in these samples was composed of variable mixtures of relatively fresh vascular plant detritus and moderately altered soil OM. Based on the lignin phenol compositions, most of this material appeared to be derived from angiosperm and gymnosperm vascular plant sources similar to those found in the upland coastal forests in this region. A few samples displayed lignin compositions that suggested a more significant contribution from marsh C3 grasses. However, there was no evidence of inputs of Spartina alterniflora (a C4 grass) remains from the salt marshes that surround the lower sections of Winyah Bay.  相似文献   

19.
This study examined the relationship between carbon isotopic composition of sinking organic matter (OM) and the biological, physical and chemical properties of the surface ocean in the Cariaco Basin. The 13C/12C ratio of OM (δ13Corg) in sinking particles was determined on sediment trap samples from four depths collected from 1996 to 1999 as part of the CArbon Retention In A Colored Ocean time series. Water column properties, including temperature, productivity, chlorophyll and concentration of dissolved CO2, were concurrently measured on monthly cruises. The δ13Corg varied from a high of –17.7‰ to a low of –22.6‰ during the study period. The variation of the δ13Corg throughout seasonal cycles was directly proportional to the strength of upwelling and was negatively correlated with temperature (r2=0.64). During the 1996–1997 upwelling event, the strongest during the study period, the δ13Corg increased by 4.4‰ whereas during the 1998–1999 upwelling event, the weakest during the study period, the δ13Corg only increased by 3.3‰. Contrary to most previous studies, we observed a negative relationship (r2=0.53) between [CO2 aq] and the estimated isotopic fractionation factor (εp). However, there was no correlation between εp and the calculated growth rates indicating that there was non-diffusive uptake of carbon into phytoplankton cells. It thus appears that [CO2 aq] does not control the δ13Corg in the water column of the study site. The best explanation for the isotopic enrichment observed is a carbon concentrating mechanism (CCM) in phytoplankton. The existence of a CCM in phytoplankton has major implications for the interpretation of the δ13Corg in the Cariaco Basin.  相似文献   

20.
Winter-spring phytoplankton blooms in Dabob Bay, Washington   总被引：4，自引：2，他引：4  
Scientific investigations in Dabob Bay, Washington State, USA, have been extensive since the early 1960s, but phytoplankton blooms have been studied mostly with regard to chlorophyll concentrations and little is known about the phytoplankton species themselves. Here we provide information on the species present, their abundances during blooms, their contribution to organic carbon concentrations and the ability of some phytoplankton species to produce toxic aldehydes that may impact metazoan grazers.Multiple blooms of phytoplankton, dominated by diatoms, occurred in the late winter-early spring period, with depth-integrated chlorophyll levels ranging from <20 to 230 mg m−2 and peaks in February and April. The major bloom species included Skeletonema costatum, Thalassiosira spp. and Chaetoceros spp; Phaeocystis cf. pouchetii occurred in 2002 and 2004. Other taxa or groups of organisms that were sometimes abundant included unidentified small flagellates <10 μm in size and unidentified heterotrophic dinoflagellates. Large diatoms usually comprised most of the cell carbon, but a large, heterotrophic dinoflagellate, identified only as Gyrodinium “tear” because of its shape, was a major contributor to the microplankton carbon when present even in small numbers. Five Thalassiosira species and S. costatum were found to produce polyunsaturated aldehydes (PUA) that are known to affect copepod reproduction and hatching success. Our findings are similar to the few previous studies in the last four decades that included phytoplankton species and suggest long-term similarities and relative stability in the phytoplankton species present and their timing in Dabob Bay.  相似文献   

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