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1.
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   

2.
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   

3.
Measurements of bromoform (CHBr3), diiodomethane (CH2I2), chloroiodomethane (CH2ICl) and bromoiodomethane (CH2IBr) were made in the water column (5–100 m depth) of the Southern Ocean within 0–40 km of the Antarctic sea ice during the ANTXX1/2 transect of the German R/V Polarstern, at five locations between 70–72°S and 9–11°W in the Antarctic spring/summer of 2003–2004. Some of the profiles exhibited a very pronounced layer of surface sea-ice meltwater, as evidenced by salinity minima and temperature maxima, along with surface maxima in concentrations of CHBr3, CH2I2, CH2ICl and CH2IBr. These results are consistent with in situ surface halocarbon production by ice algae liberated from the sea ice, although production within the sea ice followed by transport cannot be entirely ruled out. Additional sub-surface maxima in halocarbons occurred between 20 and 80 m. At a station further from shore and not affected by surface sea-ice meltwater, surface concentrations of CH2I2 were decreased whereas CH2ICl concentrations were increased compared to the stations influenced by meltwater, consistent with photochemical conversion of CH2I2 to CH2ICl, perhaps during upward mixing from a layer at  70 m enhanced in iodocarbons. Mean surface (5–10 m) water concentrations of halocarbons in these coastal Antarctic waters were 57 pmol l− 1 CHBr3 (range 44–78 pmol l− 1), 4.2 pmol l− 1 CH2I2 (range 1.7–8.2 pmol l− 1), 0.8 pmol l− 1 CH2IBr (range 0.2–1.4 pmol l− 1), and 0.7 pmol l− 1 CH2ICl (range 0.2–2.4 pmol l− 1). Concurrent measurements in air suggested a sea-air flux of bromoform near the Antarctic coast of between 1 and 100 (mean 32.3, median 10.4) nmol m− 2 day− 1 and saturation anomalies of 557–1082% (mean 783%, median 733%), similar in magnitude to global shelf values. In surface samples affected by meltwater, CH2I2 fluxes ranged from 0.02 to 6.1 nmol m− 2 day− 1, with mean and median values of 1.9 and 1.1 nmol m− 2 day− 1, respectively.  相似文献   

4.
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   

5.
Modelling trace metal concentration distributions in estuarine waters   总被引：2，自引：1，他引：2  
The concentration of dissolved organic carbon (DOC) was measured every few months from September 2000 through October 2001 at a coastal location in the center of Suruga Bay, Japan (34°51′N, 138°38′E). Water samples were collected three times per day (midday, night and predawn). DOC concentrations ranged from 91.3 to 45.2 μM C on the surface to 100 m depth. Diel variation in DOC concentrations, among the three sampling times, was greater in the upper 20 m, with a maximum difference of 21.7 μM C in July 2001, and reflected in diel DOC inventory variations from the surface to 50 m. Diel variations were controlled by both physical and biological factors. DOC concentrations were significantly correlated with potential density in the deeper layers (100–1000 m), indicating that the distribution of DOC concentrations in the deeper layer was mainly due to mixing. Most DOC concentrations in the upper layer (0–50 m) did not display the same relationship as in the deeper layer. Using the relationship with potential density at 100–1000 m, the DOC concentration in the upper layer, due simply to mixing, was calculated. The difference between the calculated and observed DOC was used to estimate biological contribution. The biological contributions to the DOC inventory in the upper layer (0–50 m) were found greatly in November 2000 and April 2001. This indicates that excess DOC accumulated, by biological processes, in the upper layer during these periods. In November 2000, the excess DOC in the inventory was constant throughout the sampling days (0.36–0.37 mol C m−2), whereas diel variations of DOC in the vertical profile were large and contrary to the variation between 10 and 20 m. This suggests that the excess DOC was contributed biologically during daytime in the uppermost layer and reached to the 50 m depth by deeper mixing. As a result, the inventory appeared to be stable over a day because of the compensating effects of DOC production and consumption throughout 50 m. In contrast, in spring and summer, there was a distinct diel inventory decrease in the nighttime, with apparent rates ranging from −0.61 to −0.35 μM C h−1. It is probable that the DOC, which accumulated during the daytime, was mostly labile, with a turnover time of a few hours. The results indicate that the dynamics of diel DOC variations varied seasonally, and suggest that these variations need to be considered when estimating seasonal DOC pools in the coastal ocean.  相似文献   

6.
The photosynthetic properties of phytoplankton populations as related to physical–chemical variations on small temporal and spatial scales and to phytoplankton size structure and pigment spectra were investigated in the Northern Adriatic Sea off the Po River delta in late winter 1997. Large diatoms (fucoxanthin) dominated the phytoplankton in the coastal area whereas small phytoflagellates (mainly 19′-hexanoyloxyfucoxanthin, chlorophyll b, 19′-butanoyloxyfucoxanthin) occurred outside the front. The front was defined by the steep gradient in density in the surface layer separating low-salinity coastal waters from the offshore waters.Physical features of the area strongly influenced phytoplankton biomass distributions, composition and size structure. After high volumes of Po River discharge several gyres and meanders occurred in the area off the river delta in February. Decreasing river discharge and the subsequent disappearance of the gyres and the spreading dilution of the river plume was observed in March. The dynamic circulation of February resulted in high photosynthetic capacity of the abundant phytoplankton population (>3.40 mg m−3). In March, the slow circulation and an upper low-salinity water layer, segregated from the deeper layers, resulted in lack of renewal of this water mass. The huge phytoplankton biomass, up to 15.77 mg chl a m−3, became nutrient depleted and showed low photosynthetic capacity. In February, an exceptionally high PmaxB, 20.11 mg C (mg chl a)−1 h−1 was recorded in the Po River plume area and average PmaxB was three-fold in February as compared to the March recordings, 10.50 mg C (mg chl a)−1 h−1 and 3.22 mg C (mg chl a)−1 h−1, respectively.The extreme variability and values of phytoplankton biomass in the innermost plume area was not always reflected in primary production. Modeling of circulation patterns and water mass resilience in the area will help to predict phytoplankton response and biomass distributions. In the frontal area, despite a considerable variability in environmental conditions, our findings have shown that the phytoplankton assemblages will compensate for nutrient depression and hydrographic constraints, by means of size and taxonomic composition and, as a result, the variability in the photosynthetic capacity was much less pronounced than that observed for other parameters.  相似文献   

7.
Measurements of sub-surface light attenuation (Kd), Secchi depth and suspended particulate material (SPM) were made at 382 locations in transitional, coastal and offshore waters around the United Kingdom (hereafter UK) between August 2004 and December 2005. Data were analysed statistically in relation to a marine water typology characterised by differences in tidal range, mixing and salinity. There was a strong statistically significant linear relationship between SPM and Kd for the full data set. We show that slightly better results are obtained by fitting separate models to data from transitional waters and coastal and offshore waters combined. These linear models were used to predict Kd from SPM. Using a statistic (D) to quantify the error of prediction of Kd from SPM, we found an overall prediction error rate of 23.1%. Statistically significant linear relationships were also evident between the log of Secchi depth and the log of Kd in waters around the UK. Again, statistically significant improvements were obtained by fitting separate models to estuarine and combined coastal/offshore data – however, the prediction error was improved only marginally, from 31.6% to 29.7%. Prediction was poor in transitional waters (D = 39.5%) but relatively good in coastal/offshore waters (D = 26.9%).SPM data were extracted from long term monitoring data sites held by the UK Environment Agency. The appropriate linear models (estuarine or combined coastal/offshore) were applied to the SPM data to obtain representative Kd values from estuarine, coastal and offshore sites. Estuarine waters typically had higher concentrations of SPM (8.2–73.8 mg l−1) compared to coastal waters (3.0–24.1 mg l−1) and offshore waters (9.3 mg l−1). The higher SPM values in estuarine waters corresponded to higher values of Kd (0.8–5.6 m−1). Water types that were identified by large tidal ranges and exposure typically had the highest Kd ranges in both estuarine and coastal waters. In terms of susceptibility to eutrophication, large macrotidal, well mixed estuarine waters, such as the Thames embayment and the Humber estuary were identified at least risk from eutrophic conditions due to light-limiting conditions of the water type.  相似文献   

8.
Seasonal change in the downward carbon transport due to respiration and mortality through diel vertical migration (DVM) of the calanoid copepods Metridia pacifica and Metridia okhotensis was estimated in the Oyashio region, western subarctic Pacific during six cruises from June 2001 to June 2002. M. pacifica (C4, C5 and adult females) was an active migratory species throughout the year though its DVM amplitude varied among seasons and stages. The mean distribution depths of adult females during the daytime were positively related with the illumination level in the water column, being shallowest in April and deepest in January. M. okhotensis generally showed less-extensive migrations than M. pacifica. Therefore, together with their lower abundance, this species is considered to be a less-important mechanism of downward transport of carbon except for April when their DVM was more active and descended deeper than M. pacifica, which remained in the upper 150 m even during the daytime. The mean migrating biomass of the two Metridia species was 558 mg C m−2 d−1 and was high during summer to winter (263–1676 mg C m−2 d−1) and low during spring (59–63 mg C m−2 d−1). Total downward flux through DVM fluctuated between 1.0 and 20.0 mg C m−2 d−1 with an annual mean of 8.0 mg C m−2 d−1. Contribution of the respiratory flux was greater than the mortality flux and accounted for 64–98% of total migratory flux throughout the year except for January when contribution of both fluxes was equal. Overall the annual carbon transport by DVM of Metridia spp. was estimated as 3.0 g C m−2 year−1, corresponding to 15% of the annual total POC flux at 150 m at the study site, suggesting that DVM is a significant process for carbon export in the subarctic region as well as that in tropical and subtropical oceanic regions. Since DVM in M. pacifica is more active during the non-bloom season when the gravitational flux of particulate matter is low, this species plays an important role in driving the biological pump in the subarctic Pacific during summer to winter.  相似文献   

9.
Samples were collected and preserved for onshore measurement of dissolved organic carbon (DOC) in the area extending over the Polar Frontal Zone (PFZ) (26–40°W, 48–52°S) in September-December 1988. The highest concentrations of DOC were found in the pycnocline layer, near the southern boundary of the PFZ and in dynamically active areas, such as meanders and mesoscale eddies, where the DOC concentrations amounted to 6–8 mg l−1. To the north and south of the PFZ, concentration of DOC diminished considerably, as a result of less intensive processes of organic matter production.  相似文献   

10.
Dissolved Al carried in river water apparently undergoes a fractional removal at the early stages of mixing in the Conway estuary. On the other hand, dissolved Al behaves almost conservatively in high salinity (>13) estuarine waters. In order to understand the geochemistry of Al in these estuarine waters, simple empirical sorption models have been used. Partitioning of Al occurs between solid and solution phases with a distribution coefficient, Kd, which varies from 0.67 × 105 to 3.38 × 106 ml g−1 for suspended particle concentrations of 2–64 mg l−1. The Kd values in general decrease with increasing suspended particulate matter and this tendency termed the “particle concentration effect” is quite pronounced in these waters. The sorption model derived by previous workers for predicting concentrations of dissolved Al with changing suspended sediment loads has been applied to these data. Reasonable fits are obtained for Kd values of 105, 106 and 107 ml g−1 with various values of α. Further, a sorption model is proposed for particulate Al concentrations in these waters that fits the data extremely well defined by a zone with Kd value 107 ml g−1 and C0 values 16 × 10−6 mg ml−1 and 92 × 10−6 mg ml−1. These observations provide strong evidence of sorption processes as key mechanisms influencing the distribution of dissolved and particulate Al in the Conway estuary and present new insight into Al geochemistry in estuaries.  相似文献   

11.
The Mussel Watch program conducted along the French coasts for the last 20 years indicates that the highest mercury concentrations in the soft tissue of the blue mussel (Mytilus edulis) occur in animals from the eastern part of Seine Bay on the south coast of the English Channel, the “Pays de Caux”. This region is characterized by the presence of intertidal and submarine groundwater discharges, and no particular mercury effluent has been reported in its vicinity. Two groundwater emergence systems in the karstic coastal zone of the Pays de Caux (Etretat and Yport with slow and fast water percolation pathways respectively) were seasonally sampled to study mercury distribution, partitioning and speciation in water. Samples were also collected in the freshwater–seawater mixing zones in order to compare mercury concentrations and speciation between these “subterranean” or “groundwater” estuaries and the adjacent macrotidal Seine estuary, characterized by a high turbidity zone (HTZ). The mercury concentrations in the soft tissue of mussels from the same areas were monitored at the same time.The means of the “dissolved” (< 0.45 μm) mercury concentrations (HgTD) in the groundwater springs were 0.99 ± 0.15 ng l− 1 (n = 18) and 0.44 ± 0.17 ng l− 1 (n = 17) at Etretat and Yport respectively. High HgTD concentrations were associated with strong runoff over short water pathways during storm periods, while low concentrations were associated with long groundwater pathways. Mean particulate mercury concentrations were 0.22 ± 0.05 ng mg− 1 (n = 16) and 0.16 ± 0.10 ng mg− 1 (n = 17) at Etretat and Yport respectively, and decreased with increasing particle concentration probably as a result of dilution by particles from soil erosion. Groundwater mercury speciation was characterized by high reactive-to-total mercury ratios in the dissolved phase (HgRD/HgTD: 44–95%), and very low total monomethylmercury concentrations (MMHg < 8 pg l− 1). The HgTD distributions in the Yport and Etretat mixing zones were similar (overall mean concentration of 0.73 ± 0.21 ng l− 1, n = 43), but higher than those measured in the adjacent industrialized Seine estuary (mean: 0.31 ± 0.11 ng l− 1, n = 67). In the coastal waters along the Pays de Caux dissolved monomethylmercury (MMHgD) concentrations varied from 9.5 to 13.5 pg l− 1 (2 to 8% of the HgTD). Comparable levels were measured in the Seine estuary (range: 12.2– 21.1 pg l−1; 6–12% of the HgTD). These groundwater karstic estuaries seem to be mostly characterized by the higher HgTD and HgRD concentrations than in the adjacent HTZ Seine estuary. While the HTZ of the Seine estuary acts as a dissolved mercury removal system, the low turbid mixing zone of the Pays de Caux receives the dissolved mercury inputs from the groundwater seepage with an apparent Hg transfer from the particulate phase to the “dissolved” phase (< 0.45 μm). In parallel, the soft tissue of mussels collected near the groundwater discharges, at Etretat and Yport, exhibited significantly higher values than those found in the mussel from the mouth of the Seine estuary. We observe that this difference mimics the differences found in the mercury distribution in the water, and argue that the dissolved phase of the groundwater estuaries and coastal particles are significant sources of bioavailable mercury for mussels.  相似文献   

12.
Physical forcing plays a major role in determining biological processes in the ocean across the full spectrum of spatial and temporal scales. Variability of biological production in the Bay of Bengal (BoB) based on basin-scale and mesoscale physical processes is presented using hydrographic data collected during the peak summer monsoon in July–August, 2003. Three different and spatially varying physical processes were identified in the upper 300 m: (I) anticyclonic warm gyre offshore in the southern Bay; (II) a cyclonic eddy in the northern Bay; and (III) an upwelling region adjacent to the southern coast. In the warm gyre (>28.8 °C), the low salinity (33.5) surface waters contained low concentrations of nutrients. These warm surface waters extended below the euphotic zone, which resulted in an oligotrophic environment with low surface chlorophyll a (0.12 mg m−3), low surface primary production (2.55 mg C m−3 day−1) and low zooplankton biovolume (0.14 ml m−3). In the cyclonic eddy, the elevated isopycnals raised the nutricline upto the surface (NO3–N > 8.2 μM, PO4–P > 0.8 μM, SiO4–Si > 3.5 μM). Despite the system being highly eutrophic, response in the biological activity was low. In the upwelling zone, although the nutrient concentrations were lower compared to the cyclonic eddy, the surface phytoplankton biomass and production were high (Chl a – 0.25 mg m−3, PP – 9.23 mg C m−3 day−1), and mesozooplankton biovolume (1.12 ml m−3) was rich. Normally in oligotrophic, open ocean ecosystems, primary production is based on ‘regenerated’ nutrients, but during episodic events like eddies the ‘production’ switches over to ‘new production’. The switching over from ‘regenerated production’ to ‘new production’ in the open ocean (cyclonic eddy) and establishment of a new phytoplankton community will take longer than in the coastal system (upwelling). Despite the functioning of a cyclonic eddy and upwelling being divergent (transporting of nutrients from deeper waters to surface), the utilization of nutrients leading to enhanced biological production and its transfer to upper trophic levels in the upwelling region imply that the energy transfer from primary production to secondary production (mesozooplankton) is more efficient than in the cyclonic eddy of the open ocean. The results suggest that basin-scale and mesoscale processes influence the abundance and spatial heterogeneity of plankton populations across a wide spatial scale in the BoB. The multifaceted effects of these physical processes on primary productivity thus play a prominent role in structuring of zooplankton communities and could consecutively affect the recruitment of pelagic fisheries.  相似文献   

13.
Dissolved organic carbon (DOC), dissolved organic nitrogen (DON) and dissolved organic phosphorus (DOP) measured in deep profiles in the N-E Atlantic and in the N-W Mediterranean in the period 1984–2002 are described. After accurate validation, they show close agreement with those previously published.Classic profiles were obtained, with concentrations decreasing in deep waters. In the Mediterranean and in the Atlantic comparable concentrations were found in the 1500–2000 m waters, 44–46 μmol l−1 DOC, 2.6–2.8 μmol l−1 DON and 0.02–0.03 μmol l−1 DOP. In the surface layers, DOC concentrations were higher, but DON and DOP concentrations lower, in the Mediterranean than in the Atlantic, leading to higher element ratios in the Mediterranean. In autumn, values were, respectively, DOC:DON 17 vs. 14, DOC:DOP 950 vs. 500 and DON:DOP 55 vs. 35. The data suggest an increase in DOC and DON in the North Atlantic Central Water over 15 years, which may be linked to the North Atlantic climatic oscillations.Refractory DOM found in the 1500–2000 m layer exhibited C:N:P ratios of 1570:100:1. The labile+semi-labile (=non-refractory) DOM (nrDOM) pool was computed as DOM in excess of the refractory pool. Its contribution to total DOM above the thermocline in the open sea amounted to 25–35% of DOC, 30–35% of DON, and 60–80% of DOP. Element ratios of the nrDOM varied among stations and were lower than those of refractory DOM, except for C:N in the Mediterranean: nrDOC:nrDON 10–19, nrDOC:nrDOP 160–530 and nrDON:nrDOP 15–38. The specific stoichiometry of DOM in the Mediterranean led us to postulate that overconsumption of carbon is probably a main process in that oligotrophic sea.By coupling non-refractory DOM stoichiometry and relationships between the main DOM elements in the water column, the relative mineralization of C, N and P from DOM was studied. Below the thermocline, the preferential removal of phosphorus with regard to carbon from the semi-labile DOM can be confirmed, but not the preferential removal of nitrogen. In the ocean surface layers, processes depend on the oceanic area and can differ from deep waters, so preferential carbon removal seems more frequent. Bacterial growth efficiency data indicate that bacteria are directly responsible for mineralization of a high proportion of DON and DOP in the deep water.  相似文献   

14.
The detailed distribution of algal chlorophyll and carotenoid pigments was determined around the halocline (freshwater-seawater interface) in the Krka Estuary on the east coast of the Adriatic Sea; in May 1988. After collection of water along the estuary, particulate matter was extracted and analyzed for pigments by high-performance liquid chromatography coupled with absorbance and fluorescence detection. Bottom marine waters were characterized by lower chlorophyll a (chl a) concentrations than encountered in surface waters, decreasing downstream from 0.50 μg l−1 to 0.16 μg l−1 at the marine end-member. The highest concentrations of chl α (up to 26.34 μg l−1) were found in the interfacial layer, an particularly at one station located off the city of ibenik, where high inputs of nutrients supported the accumulation of living algae at the halocline. Fucoxanthin was the most abundant carotenoid, which indicates a euryhaline dominance of diatoms in the estuary, whereas the dinoflagellate-derived carotenoid peridinin was confined to the interfacial and bottom saline waters of the inner estuary. High concentrations of alloxanthin and chl b were found in the interfacial layer, which also suggests an accumulation of Cryptophyceae and green algae in the inner estuary. Phaeophorbides showed higher concentrations in bottom waters than in surface waters, whereas the highest concentrations occurred in the interfacial layer. These high levels could reflect a density trapping of dead cells in an early degradation state, as suggested by the importance of allomerized chl a and chlorophyllide a vs. total chl a, or of faecal pellets originating from zooplankton grazing in the interfacial layer.  相似文献   

15.
The Laptev Sea is a high-Arctic epicontinental sea north of Siberia (Russia) that is one of the least understood regions of the world’s ocean. It is characterized by a shallow and broad shelf plateau, high influx of river water, sediments and nutrients during summer, long-lasting sea-ice cover from October to May, and the formation of a narrow flaw-lead polynya off the fast-ice edge during winter.Here, we describe results of a German–Russian research project (1993-present), presenting the distribution patterns and dynamics of its marine flora and fauna, as well as pathways and processes of coupling between sea-ice, water-column and sea-floor biota.Three ecological zones are distinguished along a combined east–west and Lena-impact gradient, differing in the composition of pelagic and benthic communities. In general, high Chl a concentrations in the sediments indicate a tight coupling between sympagic and pelagic primary production and nutrient supply to the benthos throughout the entire Laptev Sea. However, there were pronounced regional differences between the ecological zones in magnitude of primary production and trophic dynamics. Primary production during the ice-free summer was highest in the estuarine zone most strongly influenced by the Lena River (210 mg C m−2 day−1). The western and northeastern Laptev Sea yielded 55 and 95 mg C m−2 day−1, respectively. Moreover, the zones differed in the partitioning of carbon flux between zooplankton and benthic food webs. In the Lena zone zooplankton carbon demand was about 31 mg C m−2 day−1 whereas in the western zone it was 21 mg C m−2 day−1 and in the eastern zone 4 mg C m−2 day−1. Total benthic carbon demand was 32 mg C m−2 day−1 for the Lena zone, 56 mg C m−2 day−1 in the western zone and 100 mg C m−2 day−1 in the northeastern zone.A carbon budget constructed for the Laptev Sea indicates that (1) a high proportion of primary production is channelled through the benthic trophic web, bypassing the pelagic trophic web, and (2) autochthonous primary production in the northeastern and western Laptev Sea might not be sufficient to fuel both pelagic and benthic secondary production and, hence, input of allochthonous organic carbon is required to balance the overall carbon demand.  相似文献   

16.
The dynamics of dissolved inorganic carbon (DIC) and processes controlling net community production (NCP) were investigated within a mature cyclonic eddy, Cyclone Opal, which formed in the lee of the main Hawaiian Islands in the subtropical North Pacific Gyre. Within the eddy core, physical and biogeochemical properties suggested that nutrient- and DIC-rich deep waters were uplifted by 80 m relative to surrounding waters, enhancing biological production. A salt budget indicates that the eddy core was a mixture of deep water (68%) and surface water (32%). NCP was estimated from mass balances of DIC, nitrate+nitrite, total organic carbon, and dissolved organic nitrogen, making rational inferences about the unobserved initial conditions at the time of eddy formation. Results consistently suggest that NCP in the center of the eddy was substantially enhanced relative to the surrounding waters, ranging from 14.1±10.6 (0–110 m: within the euphotic zone) to 14.2±9.2 (0–50 m: within the mixed layer) to 18.5±10.7 (0–75 m: within the deep chlorophyll-maximum layer) mmol C m−2 d−1 depending on the depth of integration. NCP in the ambient waters outside the eddy averaged about 2.37±4.24 mmol C m−2 d−1 in the mixed layer (0–95 m). Most of the enhanced NCP inside the eddy appears to have accumulated as dissolved organic carbon (DOC) rather than exported as particulate organic carbon (POC) to the mesopelagic. Our results also suggest that the upper euphotic zone (0–75 m) above the deep chlorophyll maximum is characterized by positive NCP, while NCP in the lower layer (>75 m) is close to zero or negative.  相似文献   

17.
Weekly variations in total dimethylsulfoniopropionate (DMSPt) and dimethylsulfide (DMS) were investigated in relation to the phytoplankton assemblage from spring to fall 1994 at a coastal fixed station in the St. Lawrence Estuary. DMSPt and DMS concentrations showed a strong seasonality and were tightly coupled in time. Maximum concentrations of DMSPt and DMS were observed in July and August, during a period of warm water and low nutrient concentrations. Seasonal maxima of 365.4 nmol l−1 for DMSPt and 14.2 nmol l−1 for DMS in early August coincided with the presence of many phytoplankton species, such as Alexandrium tamarense, Dinophysis acuminata, Gymnodinium sp., Heterocapsa rotundata, Protoperidinium ovatum, Scrippsiella trochoidea, Chrysochromulina sp. (6 μm), Cryptomonas sp. (6 μm), a group of microflagellates smaller than 5 μm (mf < 5), many tintinnids, and Mesodinium rubrum. The abundance of mf < 5 followed the general trend of DMS concentrations. The temporal occurrence of high P. ovatum abundance and DMSPt concentrations suggests that this heterotrophic dinoflagellate can either synthesize DMSP or acquire it from DMSP-rich prey. The calculated sea-to-air DMS flux reached a maximum of 8.36 μmol −2 d−1 on August 1. The estimated annual emission from the St. Lawrence Estuary is 77.2 tons of biogenic sulfur to the atmosphere.  相似文献   

18.
Zooplankton dynamics (community composition, juvenile somatic growth rate, adult egg production, secondary production) were studied in coastal waters of the Great Barrier Reef. Two sectors were compared, one adjacent to a catchment of near-pristine land use patterns, the other to a more intensively farmed catchment. Sampling was conducted in the austral winter (August) and summer (January–March) of two succeeding years. Gradients in zooplankton community composition were weak, with only moderate effects of season and sector. Overall, 37% of zooplankton biomass was in the 73–150 μm size fraction, 26% in the 150–350 μm fraction, and 38% was >350 μm. There was no biomass difference and only small differences in community composition between samples taken during the day and at night; ostracods and large calanoid copepods were occasionally more common at night. Carbon-specific growth rates averaged 0.29 d−1 for cyclopoid copepods and 0.35 d−1 for calanoid copepods, with no difference between sectors. Calanoid copepod growth showed a significant relationship to chlorophyll concentration, but cyclopoid copepods did not. Copepod egg production was low (7.9 ± 5.9 eggs female−1 d−1) and apparently food-limited. Copepod secondary production was lower in August (mean = 2.6, range 1.4–4.0 mg C m−2 d−1) than in January–March (mean = 8.5, range 2.4–15.5 mg C m−2 d−1). Secondary production by mesozooplankton in the 73–100 μm size range averaged 0.9% of total phytoplankton production.  相似文献   

19.
The coupling of physics and biology was examined along a 160 km long transect running out from the north coast of South Georgia Island and crossing the Southern Antarctic Circumpolar Current Front (SACCF) during late December 2000. Surface and near surface potential TS properties indicated the presence of three water types: a near-shore group of stations characterised by water which became progressively warmer and fresher closer to South Georgia, an offshore grouping in which sea surface temperatures and those at the winter water level were relatively warm (1.8°C and 0.5°C, respectively), and a third in which surface and winter water temperatures were cooler and reflected the presence of the SACCF. The transect bisected the SACCF twice, revealing that it was flowing in opposite directions, north-westward closest to South Georgia and south-eastwards at its furthest point from the island. The innermost limb was a narrow intense feature located just off the shelf break in 2000–3500 m of water and in which rapid surface baroclinic velocities (up to 35 cm s−1) were encountered. Offshore in the outermost limb, shown subsequently to be a mesoscale eddy that had meandered south from the retroflected limb of the SACCF, flow was broader and slower with peak velocities around 20 cm s−1. Chlorophyll a biomass was generally low (<1 mg m−3) over much of the transect but increased dramatically in the region of the innermost limb of the SACCF, where a deepening of the surface mixed layer was coincident with a subsurface chlorophyll maximum (7.4 mg m−3) and elevated concentrations down to 100 m. The bloom was coincident with depleted nutrient concentrations, particularly silicate, nitrate and phosphate, and although ammonium concentrations were locally depleted the bloom lay within an elevated band (up to 1.5 mmol m−3) associated with the frontal jet. Increased zooplankton abundance, higher copepod body carbon mass and egg production rates all showed a strong spatial integrity with the front. The population structure of the copepods Calanoides acutus and Rhincalanus gigas at stations within the front suggested that rather than simply resulting from entrainment and concentration within the jet, increased copepod abundance was the result of development in situ. Estimates of bloom duration, based on silicate and carbon budget calculations, set the likely duration between 82 and 122 d, a figure supported by the development schedule of the two copepod species. Given this timescale, model outputs from FRAM and OCCAM indicated that particles that occurred on the north side of South Georgia in December would have been in the central-southern Scotia Sea 2–3 months earlier, probably in sea ice affected regions.  相似文献   

20.
In this study, the contents, sources and accumulation rate of sedimentary organic matter (OM) in the Pearl River Estuary (PRE) and adjacent coastal area were investigated. The stable carbon isotopic composition (δ13C) is a reliable geochemical proxy and was used to indicate the OM origin here. Nevertheless, the organic carbon and nitrogen molar ratios (TOC/TN) and the stable nitrogen isotopic composition (δ15N) were affected by diagenesis and could be the supplementary indicators. The sources of OM were estimated based on the two end-member model. The results showed that in the estuary, sedimentary OM originated from terrestrial and aquatic mixing origins, whereas, OM in coastal sediments was dominantly algae-derived. The accumulation rate of sedimentary OM was analyzed based on 210Pb dating. Due to the sampling sites and the distinct hydraulic environments, the accumulation rates of TOC, aquatic and terrestrial OC were obviously higher in the estuary than in coastal area. TOC accumulation rates were 18–27 mg cm−2 y−1 in the estuary, and 0.84–3.6 mg cm−2 y−1 in coastal area. Aquatic OC accumulation rates were 7.9–11.3, 0.8–1.3, and 2.6–3.1 mg cm−2 y−1, and terrestrial OC accumulation rates were 9.7–16.3, 0.02–0.14, 0.16–0.42 mg cm−2 y−1 in cores 2, 5, 6, respectively. It could be seen from the high accumulation rate of organic matter in the estuary that, when nutrients increased in the river, phytoplankton biomass and productivity would also have increased. As a result, phytoplankton sinking and organic matter sedimentation usually increased with primary productivity, resulting in the observed accumulation rate of aquatic OC in the estuary. Furthermore, terrestrial OC accumulation rates in the estuary and coastal area showed an increasing trend with the age.  相似文献   

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