Cadmium, copper, lead and zinc in three species of planktonic crustaceans from the east coast of Corsica     

M. Romeo  E. Nicolas 《Marine Chemistry》1986,18(2-4)

Results of trace metal analyses performed on two species of Euphausiacea, Meganyctiphanes norvegica and Stylocheiron longicorne, and one species of Decapoda, Sergestes arcticus, collected off the east coast of Corsica, are reported. Analyses were carried out by atomic absorption spectrophotometry and by differential pulse anodic stripping voltammetry.S. arcticus contained lower concentrations of phosphorus (which was also analysed as a biological indicator), cadmium (0.33 μg g⁻¹), copper (17.7 μg g⁻¹), lead (2.13 μg g⁻¹) and zinc (51 μg g⁻¹) than the two Euphausiacea (0.50 μg Cd g⁻¹, 25.4 μg Cu g⁻¹, 4.03 μg Pb g⁻¹ and 59 μg Zn g⁻¹). Moreover, manganese concentrations were low in all the samples.When the results presented here are compared with previous results on phytoplankton and mesozooplankton, there appears to be no trend of trace metal enrichment from phytoplankton to the Decapoda.  相似文献   

Nutrient flux in the Rhode River: Tidal transport of microorganisms in brackish marshes     

P. A. Rublee  S. M. Merkel  M. A. Faust 《Estuarine, Coastal and Shelf Science》1983,17(6):669-680

Concentrations of bacteria, chlorophyll a, and several dissolved organic compounds were determined during 11 tidal cycles throughout the year in a high and a low elevation marsh of a brackish tidal estuary. Mean bacterial concentrations were slightly higher in flooding (7·1 × 10⁶ cells ml⁻¹) than in ebbing waters (6·5 × 10⁶ cells ml⁻¹), and there were no differences between marshes. Mean chlorophyll a concentrations were 36·7 μg l⁻¹ in the low marsh and 20·4 μg l⁻¹ in the high marsh. Flux calculations, based on tidal records and measured concentrations, suggested a small net import of bacterial and algal biomass into both marshes. Over the course of individual tidal cycles, concentrations of all parameters were variable and not related to tidal stage. Heterotrophic activity measured by the uptake of ³H-thymidine, was found predominantly in the smallest particle size fractions (< 1·0 μm). Thymidine uptake was correlated with temperature (r = 0·48, P < 0·01), and bacterial productivity was estimated to be 7 to 42 μg Cl⁻¹ day⁻¹.  相似文献   

Phytoplankton growth, microzooplankton herbivory and community structure in the southeast Bering Sea: insight into the formation and temporal persistence of an Emiliania huxleyi bloom     

M. Brady Olson  Suzanne L. Strom 《Deep Sea Research Part II: Topical Studies in Oceanography》2002,49(26)

Using the seawater dilution technique, we measured phytoplankton growth and microzooplankton grazing rates within and outside of the 1999 Bering Sea coccolithophorid bloom. We found that reduced microzooplankton grazing mortality is a key component in the formation and temporal persistence of the Emiliania huxleyi bloom that continues to proliferate in the southeast Bering Sea. Total chlorophyll a (Chl a) at the study sites ranged from 0.40 to 4.45 μg C l⁻¹. Highest phytoplankton biomass was found within the bloom, which was a mixed assemblage of diatoms and E. huxleyi. Here, 75% of the Chl a came from cells >10 μm and was attributed primarily to the high abundance of the diatom Nitzschia spp. Nutrient-enhanced total phytoplankton growth rates averaged 0.53 d⁻¹ across all experimental stations. Average growth rates for >10 μm and <10 μm cells were nearly equal, while microzooplankton grazing varied among stations and size fractions. Grazing on phytoplankton cells >10 μm ranged from 0.19 to 1.14 d⁻¹. Grazing on cells <10 μm ranged from 0.02 to 1.07 d⁻¹, and was significantly higher at non-bloom (avg. 0.71 d⁻¹) than at bloom (avg. 0.14 d⁻¹) stations. Averaged across all stations, grazing by microzooplankton accounted for 110% and 81% of phytoplankton growth for >10 and <10 μm cells, respectively. These findings contradict the paradigm that microzooplankton are constrained to diets of nanophytoplankton and strongly suggests that their grazing capability extends beyond boundaries assumed by size-based models. Dinoflagellates and oligotrich ciliates dominated the microzooplankton community. Estimates of abundance and biomass for microzooplankton >10 μm were higher than previously reported for the region, ranging from 22,000 to 227,430 cells l⁻¹ and 18 to 164 μg C l⁻¹. Highest abundance and biomass occurred in the bloom and corresponded with increased abundance of the large ciliate Laboea, and the heterotrophic dinoflagellates Protoperidinium and Gyrodinium spp. Despite low grazing rates on phytoplankton <10 μm within the bloom, the abundance and biomass of small microzooplankton (<20 μm) capable of grazing E. huxleyi was relatively high at bloom stations. This body of evidence, coupled with observed high grazing rates on large phytoplankton cells, suggests the phytoplankton community composition was strongly regulated by herbivorous activity of microzooplankton. Because grazing behavior deviated from size-based model predictions and was not proportional to microzooplankton biomass, alternate mechanisms that dictate levels of grazing activity were in effect in the southeastern Bering Sea. We hypothesize that these mechanisms included morphological or chemical signaling between phytoplankton and micrograzers, which led to selective grazing pressure.  相似文献   

Responses of marine phytoplankton in iron enrichment experiments in the northern North Sea and northeast Atlantic Ocean     

Klaas R. Timmermans  Martha Gledhill  Rob F. Nolting  Marcel J. W. Veldhuis  Hein J. W. de Baar  Constant M. G.van den Berg 《Marine Chemistry》1998,61(3-4)

Short-term iron enrichment experiments were carried out with samples collected in areas with different phytoplankton activity in the northern North Sea and northeast Atlantic Ocean in the summer of 1993. The research area was dominated by high numbers of pico-phytoplankton, up to 70,000 ml⁻¹. Maximum chlorophyll a concentrations varied from about 1.0 μg l⁻¹ in a high-reflectance zone (caused by loose coccoliths, remnants from a bloom of Emiliania huxleyi) and about 3.5 μg l⁻¹ in a zone in which the phytoplankton were growing, to about 0.5 μg l⁻¹ in the northeast Atlantic Ocean. From the high-reflectance zone to the northeast Atlantic Ocean, nitrate concentrations increased from 0.5 μM to 6.0 μM. Concentrations of reactive iron in surface water showed an opposite trend and decreased from about 2.6 nM in the high-reflectance zone to <1.0 nM in the northeast Atlantic Ocean. In the research area, no signs of true iron deficiency were found, but iron enrichments in the high-reflectance zone, numerically dominated by Synechococcus sp., resulted in increased nitrate uptake. Ammonium uptake was hardly affected. Strong support for the effect of Fe on cell physiology is given by the increase in the f-ratio. Net growth rates of the phytoplankton (changes in cell numbers over 24 h) were almost unchanged. Phytoplankton collected from the northeast Atlantic Ocean, did not show changes in the nitrogen metabolism upon addition of iron. Net growth rates in these incubations were low or negative, with only slightly higher values with additional iron.  相似文献   

Responses of phytoplankton and heterotrophic bacteria in the northwest subarctic Pacific to in situ iron fertilization as estimated by HPLC pigment analysis and flow cytometry   总被引：3，自引：0，他引：3  

Koji Suzuki  Akira Hinuma  Hiroaki Saito  Hiroshi Kiyosawa  Hongbin Liu  Toshiro Saino  Atsushi Tsuda 《Progress in Oceanography》2005,64(2-4):167

To verify the hypothesis that the growth of phytoplankton in the Western Subarctic Gyre (WSG), which is located in the northwest subarctic Pacific, is suppressed by low iron (Fe) availability, an in situ Fe fertilization experiment was carried out in the summer of 2001. Changes over time in the abundance and community structure of phytoplankton were examined inside and outside an Fe patch using phytoplankton pigment markers analyzed by high-performance liquid chromatography (HPLC) and flow cytometry (FCM). In addition, the abundance of heterotrophic bacteria was also investigated by FCM. The chlorophyll a concentration was initially ca. 0.9 μg l⁻¹ in the surface mixed layer where diatoms and chlorophyll b-containing green algae (prasinophytes and chlorophytes) were predominant in the chlorophyll biomass. After the iron enrichment, the chlorophyll a concentration increased up to 9.1 μg l⁻¹ in the upper 10 m inside the Fe patch on Day 13. At the same time, the concentration of fucoxanthin (a diatom marker) increased 45-fold in the Fe patch, and diatoms accounted for a maximum 69% of the chlorophyll biomass. This result was consistent with a microscopic observation showing that the diatom Chaetoceros debilis had bloomed inside the Fe patch. However, chlorophyllide a concentrations also increased in the Fe patch with time, and reached a maximum of 2.2 μg l⁻¹ at 5 m depth on Day 13, suggesting that a marked abundance of senescent algal cells existed at the end of the experiment. The concentration of peridinin (a dinoflagellate marker) also reached a maximum 24-fold, and dinoflagellates had contributed significantly (>15%) to the chlorophyll biomass inside the Fe patch by the end of the experiment. Concentrations of 19′-hexanoyloxyfucoxanthin (a prymnesiophyte marker), 19′-butanoyloxyfucoxanthin (a pelagophyte marker), and alloxanthin (a cryptophyte marker) were only incremented a few-fold increment inside the Fe patch. On the contrary, chlorophyll b concentration reduced to almost half of the initial level in the upper 10 m water column inside the Fe patch at the end of the experiment. A decrease with time in the abundance of eukaryotic ultraphytoplankton (<ca. 5 μm in size), in which chlorophyll b-containing green algae were possibly included was also observed by FCM. Overall, our results indicate that Fe supply can dramatically alter the abundance and community structure of phytoplankton in the WSG. On the other hand, cell density of heterotrophic bacteria inside the Fe patch was maximum at only ca. 1.5-fold higher than that outside the Fe patch. This indicates that heterotrophic bacteria abundance was little respondent to the Fe enrichment.  相似文献   

A laboratory and field comparison of sediment polycyclic aromatic hydrocarbon bioaccumulation by the cosmopolitan estuarine polychaete Streblospio benedicti (Webster)     

P.Lee Ferguson  G.Thomas Chandler 《Marine environmental research》1998,45(4-5)

Polycyclic aromatic hydrocarbon (PAH) bioaccumulation by the polychaete worm Streblospio benedicti (Webster) was measured under exposure to PAH-contaminated sediments in the field and for 28 d in the laboratory. Streblospio benedicti collected from field sediments contaminated at 2.94, 1.07, and l.52 μg g⁻¹ fluoranthene (FLU), benz[a]anthracene (BAA), and benzo[a]pyrene (BAP), bioaccumulated those PAHs at 1.53, 0.215, and 0.332 μg g⁻¹, while worms isolated from less contaminated field sediments (0.399, 0.228, 0.288 μg g⁻¹ FLU, BAA, and BAP) had FLU, BAA, and BAP body burdens of 0.543, 0.236, and 0.083 μg g⁻¹. Worms incubated for 28 d in PAH-spiked sediments (1.52, 0.991, 0.504 μg g⁻¹ FLU, BAA, and BAP) bioaccumulated those PAHs at 0.382, 0.966, and 0.602 μg g⁻¹, respectively. Data normalization to organism lipid and sediment organic carbon (biota-sediment accumulation factors [BSAFs] strongly suggest that Streblospio PAH bioaccumulation was directly related to percent sediment organic carbon, but BSAFs were substantially lower than predicted by equilibrium partitioning theory. BSAFs decreased with increasing PAH log K_ow, in worms collected from field sediments, but in spiked sediments BSAFs increased with increasing PAH hydrophobicity. This disparity may have been caused by insufficient spiked-sediment equilibration time (1.5h) in the case of the laboratory test sediments.  相似文献   

Adaptation of the polychaete Neanthes Arenaceodentata to copper     

Carol E. Pesch  Gerald L. Hoffman 《Marine environmental research》1982,6(4):307-317

Neanthes arenaceodentata were exposed to 292, 146, 92 and 56 μg litre⁻¹ Cu (measured) and control seawater after a 27-day pre-exposure to a sublethal concentration of Cu (10, 16 and 28 μg litre⁻¹ and control) to determine if the worms increased their tolerance to Cu after the pre-treatment. The worms pre-exposed to 28 μg litre⁻¹ Cu were significantly more resistant to Cu toxicity than control and 10 and 16 μg litre⁻¹ Cu pre-exposed worms. For example, the time to 50 % mortality at 92 μg litre⁻¹ Cu was 18 and 11 days for worms pre-exposed to 28 μg litre⁻¹ Cu and control conditions, respectively. The net rate of Cu uptake during the toxicity test was lower for worms pre-exposed to 28 μg litre⁻¹ Cu than for the control and 10 and 16 μg litre⁻¹ Cu pre-exposed worms. For example, the net rate of Cu uptake at 292 μg litre⁻¹ Cu by worms pre-exposed to 28 μg litre⁻¹ Cu and control conditions was 42 and 102 μg g⁻¹ day ⁻¹, respectively.  相似文献   

Observations of resuspended diatoms in the turbid tidal edge     

Cathy H. Lucas 《Journal of Sea Research》2003,50(4):301-308

Observations of resuspended diatoms in the shallow waters (<60 cm) of the turbid tidal edge are described for single sites on two tidal flats–the Molenplaat in the Westerschelde estuary, and the Hond in the Ems-Dollard estuary, The Netherlands. High concentrations of chlorophyll-a (chl-a) were observed in the trailing edge of the ebbing tide in water depths of <20 cm, after which concentrations decreased markedly. Peak mean values were 19 μg chl-a l⁻¹ in 10 cm of water at the Molenplaat, and 45 μg chl-a l⁻¹ in 5 cm of water at the Hond. Similar trends were observed on the flooding tide, although peak values were far less pronounced (6 and 30 μg chl-a l⁻¹ respectively). Microscopic examination of the diatom community within the turbid tidal edge at the Molenplaat revealed that peaks in biomass were caused by suspended benthic diatoms, as well as the large centric diatom Coscinodiscus sp., particularly on the ebb tide. Planktonic diatoms other than Coscinodiscus sp. were more randomly distributed and did not appear to follow any particular trend. It would seem that as the tide recedes, resuspended benthic diatoms and large Coscinodiscus sp. cells become concentrated in the shallow water. However, the virtual absence of Coscinodiscus sp. from the leading edge of the flooding tide suggests that most of the resuspended cells do not settle to the seabed, but are washed away into the channels. The small peak of benthic diatoms at the leading edge of the flood tide is most likely resuspended locally from the sediment, along with large numbers of diatom frustules.  相似文献   

Distribution of algal chlorophyll and carotenoid pigments in a stratified estuary: the Krka River, Adriatic Sea     

V. Denant  A. Saliot  R. F. C. Mantoura 《Marine Chemistry》1991,32(2-4)

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   

Simultaneous determination of dissolved organic carbon and total dissolved nitrogen in seawater by high temperature catalytic oxidation: conditions for precise shipboard measurements   总被引：1，自引：0，他引：1  

Xos A. lvarez-Salgado  Axel E. J. Miller 《Marine Chemistry》1998,62(3-4)

Appropriate conditions have been achieved for the accurate, rapid, and highly precise shipboard simultaneous determination of dissolved organic carbon and total dissolved nitrogen in seawater by high temperature catalytic oxidation. A nitrogen-specific Antek 705D chemiluminescence detector and a CO₂-specific LiCor Li6252 IRGA have been coupled in-series with a Shimadzu TOC-5000 organic carbon analyser. Precision of both simultaneous measurements is ≤1.5%, i.e. ±1 μmol C l⁻¹ and ±0.3 μmol N l⁻¹, respectively. Quality of analysis is not compromised by vibrations associated with ocean going research vessels.  相似文献   

Grazing by meso- and microzooplankton on phytoplankton in the upper reaches of the Schelde estuary (Belgium/The Netherlands)   总被引：1，自引：1，他引：1  

M. Lionard  F. Azmar  S. Boulêtreau  K. Muylaert  M. Tackx  W. Vyverman 《Estuarine, Coastal and Shelf Science》2005,64(4):764-774

In contrast with the marine reaches of estuaries, few studies have dealt with zooplankton grazing on phytoplankton in the upper estuarine reaches, where freshwater zooplankton species tend to dominate the zooplankton community. In spring and early summer 2003, grazing by micro- and mesozooplankton on phytoplankton was investigated at three sites in the upper Schelde estuary. Grazing by mesozooplankton was evaluated by monitoring growth of phytoplankton in 200 μm filtered water in the presence or absence of mesozooplankton. In different experiments, the grazing impact was tested of the calanoïd copepod Eurytemora affinis, the cyclopoid copepods Acanthocyclops robustus and Cyclops vicinus and the cladocera Chydorus sphaericus, Moina affinis and Daphnia magna/pulex. No significant grazing impact of mesozooplankton in any experiment was found despite the fact that mesozooplankton densities used in the experiments (20 or 40 ind. l⁻¹) were higher than densities in the field (0.1–6.9 ind. l⁻¹). Grazing by microzooplankton was evaluated by comparing growth of phytoplankton in 30 and 200 μm filtered water. Microzooplankton in the 30–200 μm size range included mainly rotifers of the genera Brachionus, Trichocerca and Synchaeta, which were present from 191 to 1777 ind. l⁻¹. Microzooplankton had a significant grazing impact in five out of six experiments. They had a community grazing rate of 0.41–1.83 day⁻¹ and grazed up to 84% of initial phytoplankton standing stock per day. Rotifer clearance rates estimated from microzooplankton community grazing rates and rotifer abundances varied from 8.3 to 41.7 μl ind.⁻¹ h⁻¹. CHEMTAX analysis of accessory pigment data revealed a similar phytoplankton community composition after incubation with and without microzooplankton, indicating non-selective feeding by rotifers on phytoplankton.  相似文献   

Multi-proxy evidence of long-term changes in ecosystem structure in a Danish marine estuary, linked to increased nutrient loading   总被引：3，自引：0，他引：3  

Marianne Ellegaard  Annemarie L. Clarke  Nina Reuss  Simon Drew  Kaarina Weckstrm  Stephen Juggins  N. John Anderson  Daniel J. Conley 《Estuarine, Coastal and Shelf Science》2006,68(3-4):567

This paper presents a study of changes in eutrophication over the past 100 years in a fertile estuary. The Danish estuary Mariager Fjord is a long, narrow sill-fjord with a permanently anoxic basin. In 1997 anoxia spread from the basin to the entire inner estuary, killing almost all eukaryotes and prompting debate on the causes. This paper reports a multi-proxy survey of ²¹⁰Pb-dated sediment cores from the anoxic basin. Analyses of diatoms, dinoflagellates, pigments and geochemical proxies were used to determine changes in ecosystem structure over the past 100 years. The aim was to establish ‘base-line conditions’, for management purposes, of the biological structure prior to 1900, and to examine possible causes of changes observed. Geochemical proxies total nitrogen (TN), total carbon (TC) and biogenic silica (BSi) were consistently high throughout the sediment record. Increased concentrations of pigments and natural isotopes (δ¹³C, δ¹⁵N) suggested increasing production and nutrient loading. The main changes in the biological proxies occurred between 1915 and the 1940s, and indicated that the estuary has been somewhat eutrophic since 1900, but that the eutrophication process increased over the past 100 years. A reconstruction of TN concentration by a diatom-based transfer function supports this interpretation, with inferred TN ca. 1900 around 60 μmol l⁻¹, and an increase in TN concentration over the past century to ca. 130 μmol l⁻¹ by 1995. Inferred TN decreased to ca. 100 μmol l⁻¹ by 2001, similar to present day monitoring data.  相似文献   

Seasonal variations in dimethylsulfoniopropionate and dimethylsulfide concentrations in relation to the plankton community in the St. Lawrence Estuary   总被引：1，自引：1，他引：1  

Sonia Michaud  Maurice Levasseur  Guy Cantin   《Estuarine, Coastal and Shelf Science》2007,71(3-4):741-750

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   

Geochemistry of suspended matter from the Baltic Sea 2. Results of bulk trace metal analysis by AAS     

Lutz Brügmann  Paul C. Bernard  Rene van Grieken 《Marine Chemistry》1992,38(3-4)

In 1984, on a transect covering the whole Baltic Sea and parts of the adjacent North Sea, 160 water samples were taken and analysed for their concentrations of particulate and dissolved metals. In addition, the suspended materials were investigated for their elemental bulk composition.The particulate fractions represented from about 5% (Cd, Cu and Ni) to 50% (Fe and Pb) of the total (particulate plus dissolved) concentrations. For some elements (Ba, Cd, Cu, Pb and Zn), the particulate matter from the surface microlayer was enriched with respect to those suspended materials taken from 0.2 m depth. This could reflect the atmospheric input of metal-rich aerosols. In anoxic deep waters, maximum contents of Zn (6400 μg g⁻¹), Cu (1330 μg g⁻¹) and Cd (12 μg g⁻¹) were observed in the particulate matter, indicating sulphidic forms. On the other hand, under oxic conditions the distribution coefficients (K_d) decreased with the water depth (Cd, Fe and Pb).Relative to global background levels, the particulate matter contained metal “excesses” amounting to more than 90% of the total contents (Cd, Mn, Pb and Zn). Automated electron probe X-ray microanalysis (EPXMA) revealed that the elemental composition of sediments is mainly governed by post-depositional processes of early diagenesis and is only weakly related to the composition of suspended matter in the overlying water body. For instance, in relation to surface mud sediments of the central Baltic net-sedimentation basins, Zn, Cd, Cu and Mn had 30–100% higher levels in the suspended materials. The general pattern of metal contents of particulate matter taken from 10 m depth on a transect between the Bothnian Bay and the North Sea were—possibly as a result of anthropogenic inputs—rather similar for Pb, Zn and Cu. For Fe and Mn, the distribution patterns along the transect were probably governed by the natural loading characteristics and by the biogeochemistry of those elements.  相似文献   

Eutrophication and the rate of net nitrification in a coastal marine ecosystem     

Veronica M. Berounsky  Scott W. Nixon 《Estuarine, Coastal and Shelf Science》1985,20(6):773-781

Rates of net nitrification were calculated for four large (13 m³) estuarine-based microcosms that had been subjected to inorganic nutrient enrichment. Calculated rates were based on two years of weekly nitrate and nitrite measurements and ranged from a maximum of 0·55 μmol NO₂₊₃⁻ produced l⁻¹ day⁻¹ in the control tank (no enrichment) to over 13 μmol NO₂₊₃⁻ produced l⁻¹ day⁻¹ in the most enriched tank (receiving 18·6 μmol NH₄ l⁻¹ day⁻¹). Almost all NO₂₊₃⁻ production was pelagic, little was benthic. Net NO₃⁻ production or net NO₂⁻ production dominated the net nitrification rates during different seasons. Good correlations were found between various oxidation rates and substrate concentrations. The calculated net nitrite production rates were 10 to 1000 times higher than previously reported rates for open ocean systems, demonstrating the potential importance of nitrification to estuarine systems.  相似文献   

The physiology of the larva of the Chilean oyster Ostrea chilensis and the utilisation of biochemical energy reserves during development: An extreme case of the brooding habit     

O.R. Chaparro  L.R. Navarrete  R.J. Thompson 《Journal of Sea Research》2006,55(4):292-300

In the oyster Ostrea chilensis the adult female broods the young for almost the entire developmental period, releasing a large pediveliger larva (450 μm shell length) with an extremely short pelagic phase. In this study of the larval physiology, the dry weight of the embryo or larva remained constant during the early developmental stages (as far as, and including, the trochophore), but the veliger grew steadily to reach 8 μg at 450 μm shell length, the stage at which it was ready for release. During this growth period the veliger consumed metabolic reserves (62% protein and 38% lipid). Carbohydrate levels were negligible. Chilean oyster veligers larger than 275 μm shell length were able to remove particles from suspension, but clearance rate (2 μl h^− 1 larva^− 1 at 450 μm shell length) was much lower than published values for planktotrophic veligers. Low clearance rate in the veliger of O. chilensis is probably attributable to the absence of the postoral ciliary band. Oxygen uptake increased from 19 – 22 nl O₂ h^− 1 ind^− 1 for pre-veliger stages to 32 nl O₂ h^− 1 ind^− 1 for a veliger 450 μm long, which is consistent with published values for veligers in general when corrected for body weight. Excretion rate was low, increasing from 0.04 ng NH₄-N h^− 1 larva^− 1 in the trochophore to 0.13 ng NH₄-N h^− 1 larva^− 1 in a pediveliger of shell length 450 μm. Biochemical energy reserves were insufficient to meet the metabolic demands of the developing larva, suggesting that uptake of particles and/or dissolved organic matter from the mantle cavity of the female is necessary for successful development.  相似文献   

Determination of dissolved nucleic acids in seawater by the fluorescence dye, ethidium bromide     

Seiji Sakano  Akiyoshi Kamatani 《Marine Chemistry》1992,37(3-4)

A new method for the determination of dissolved double-stranded deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) in seawater was developed, evaluated and used to study the fates of these nucleic acids in marine ecosystems. These nucleic acids, which were pre-concentrated on a hydroxyapatite column, were determined fluorometrically by the use of ethidium bromide dye, which binds specifically to the double-stranded polynucleotide. No dissolved organic matter coexisting in the pre-concentrated sample solution interfered in the analysis of DNA and RNA. Column recoveries of DNA and RNA in a sample volume of up to 11 were 93% and 97%, respectively, and 90% of both at 51. The detection limits of DNA and RNA concentrated from a 51 sample by this fluorometric method were 0.6 and 1.1 μg l⁻¹, respectively. The concentration of dissolved nucleic acids in the waters from Tokyo Bay and Sagami Bay showed great variation in space and time. DNA ranged from 1 to 32 μg l⁻¹, and RNA from below the detection limit to 34 μg l⁻¹. The total amount of phosphorus in nucleic acids was an important fraction (12.9 ± 8.2%) of the dissolved organic phosphorus (DOP) and showed a good correlation with DOP.  相似文献   

Volatile halocarbons released from Arctic macroalgae     

Frank Laturnus 《Marine Chemistry》1996,55(3-4)

Twenty-two different species of Arctic brown, red and green macroalgae, collected in the Kongsfjord at Ny-Ålesund (Spitsbergen), were incubated under polar conditions and investigated for their release of volatile halogenated organic compounds (VHOC). Bromoform, dibromomethane, dibromochloromethane, bromodichloromethane, 1,2-dibromoethane, diiodomethane and chloroiodomethane have been identified and their net releases during incubations were determined. Generally, brown and green macroalgae showed higher VHOC release, while red macroalage had only low release. Bromoform was released in relatively large quantities from all species studied, with the highest release observed from the brown algae Dictyosyphon foeniculaceus (0.3 μg g⁻¹ wet algal weight day⁻¹) and Laminaria saccharina (0.15 μg g⁻¹ wet algal weight day⁻¹), and from the green algae Monostroma arcticum (0.3 μg g⁻¹ wet algal weight day⁻¹) and Blidingia minima (0.27 μg g⁻¹ wet algal weight day⁻¹). Dibromomethane, diiodomethane, dibromochloromethane and 1,2-dibromoethane showed lower net release during the incubations. The net release of chloroiodomethane and bromodichloromethane was very low for the most algae species investigated. Based on the distribution of these algae in the Arctic environment, Dictyosiphon foeniculaceus and Laminaria saccharina may be important sources for VHOC because of high release and high biomass. Release of VHOC could be detected from all parts of the thallus of the macroalga. This may provide some evidence for a possible role of VHOC production as a chemical protection mechanism in algae.  相似文献   

Influence of combined changes in salinity and copper modulation on growth and copper uptake in the tropical green macroalga Ulva reticulata     

Florence Mamboya  Thomas J. Lyimo  Tommy Landberg  Mats Bjrk 《Estuarine, Coastal and Shelf Science》2009,84(3):326-330

The influence of salinity on growth and Cu uptake in the green macroalga Ulva reticulata collected from the intertidal area in the Western Indian Ocean was studied under controlled laboratory conditions. Exposure concentrations ranged from 5 to 500 μg Cu l⁻¹ at five salinities (ranging 20–40). The accumulation of Cu increased with decreasing salinity, so that the uptake at 500 μg Cu l⁻¹ was approximately 2.7, 2.4 and 2.0 times higher at salinities of 20, 25, and 30 respectively, than uptake at salinity of 35, and with uptake being lowest at salinity of 40. Ulva maintained a positive growth rate over the whole salinity range (20–40), with highest rates at salinity of 35. When exposing to Cu at low salinities (20 and 25), the growth rate of Ulva was strongly inhibited suggesting an increase in toxicity of Cu with decreasing salinity. EC50 and NOEC increased with increase in salinity, implying a reduced Cu toxicity at high salinities. It was concluded that salinity needs to be considered when using macroalgae, such as U. reticulata, as a bioindicator of heavy metals in areas with heavy rainfall, underground fresh water intrusion or in estuaries, as they might accumulate more metals and be more negatively affected.  相似文献   

Effect of iron enrichment on the dynamics of transparent exopolymer particles in the western subarctic Pacific   总被引：1，自引：0，他引：1  

Neelam Ramaiah  Shigenobu Takeda  Ken Furuya  Takeshi Yoshimura  Jun Nishioka  Tatsuo Aono  Yukihiro Nojiri  Keiri Imai  Isao Kudo  Hiroaki Saito  Atsushi Tsuda 《Progress in Oceanography》2005,64(2-4):253

Dynamics of transparent exopolymer particles (TEP) was studied during the first in situ iron-enrichment experiment conducted in the western subarctic Pacific in July–August 2001, with the goal of evaluating the contribution of TEP to vertical flux as a result of increased primary production following iron enrichment in open ocean ecosystems. Subsequent to the enhancement of phytoplankton production, we observed increase in TEP concentration in the surface layer and sedimentation of organic matter beneath it. Vertical profiles of TEP, chlorophyll a (Chl a) and particulate organic carbon (POC) were obtained from six depths between 5 and 70 m, from a station each located inside and outside the enriched patch. TEP and total mass flux were estimated from the floating sediment traps deployed at 200 m depth. Chl a and TEP concentrations outside the patch varied from 0.2 to 1.9 μg L⁻¹ and 40–60 μg XG equiv. L⁻¹, respectively. Inside the patch, Chl a increased drastically from day 7 reaching the peak of 19.2 μg L⁻¹ on day 13, which coincided with the TEP peak of 189 μg XG equiv. L⁻¹. TEP flux in the sediment trap increased from 41 to 88 mg XG equiv. m⁻² d⁻¹, with 8–14% contribution of TEP to total mass flux. This forms the basic data set on ambient concentrations of TEP in the western subarctic Pacific, and evaluation of the effect of iron enrichment on TEP.  相似文献