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1.
《Marine Chemistry》2007,103(1-2):122-130
Phosphomolybdenum blue (PMB) paired with cetyltrimethylammonium bromide (CTAB) can be extracted using a solid phase extraction technique on C18 sorbent. Based on this, a novel on-line solid phase extraction method coupled with flow injection (FI) analysis and colorimetric detection has been established to determine nanomolar level orthophosphate in seawater. A stopped flow technique was employed to assure the complete formation of the PMB–CTAB compound, which was sequentially extracted on an in-line Sep-Pak C18 cartridge. The adsorbed PMB–CTAB can be rapidly eluted by 0.56 mol/L H2SO4 in ethanol, and determined with a spectrophotometer at 700 nm. Experimental parameters, including reaction temperature, sample loading flow rate, stopped time and eluting flow rate, were optimized throughout the experiments based on univariate experimental design. The results show that reaction temperature and stopped time were the major factors affecting the formation of PMB–CTAB. Silicate concentration up to 5000 times higher than that of orthophosphate would not interfere with the determination of orthophosphate. Using artificial seawater with salinity of 35 as a matrix under the optimized conditions, the standard curve shows a linear range between 3.2 and 48.5 nmol/L, and the recovery and the detection limit of the proposed method are 96.4% and 1.57 nmol/L, respectively. The relative standard deviation (RSD) (n = 8), which was determined daily for 8 days, was 4.52% for the artificial seawater at a concentration of 32.4 nmol/L orthophosphate. Two typical seawater samples were analyzed using both the proposed method and the MAGnesium hydroxide-Induced Coprecipitation (MAGIC) method. The results of the two methods show no significant difference using the t test. Compared to the MAGIC method, the proposed method has the advantage of being more sensitive, faster, sample saving and easy for on-line analysis. 相似文献
2.
A method for the determination of nanomolar concentrations of orthophosphate in oligotrophic seawater developed by Liang et al. (2007) has been modified to make it fully feasible for shipboard application and for faster sample throughput with minimized
sample volume. The technique is based on the flow injection method with solid phase extraction on a Sep-Pak C18 cartridge
and colorimetric detector. The Schlieren effect was minimized by rinsing the cartridge sequentially with 5 mL water and 2
mL 95% ethanol solution. With three micro pumps in parallel, savings of up to 80% in amount of reagents and 25% volume of
seawater samples could be achieved in comparison to the previous method. Variation of stopped flow time and sample loading
time gave 3 different standard curves, which corresponded to 3 linear ranges within 3.4 and 515 nM. The modified method permits
the analysis of samples over a wide range of concentrations, and has been successfully applied to shipboard determination
of trace orthophosphate in more than 200 seawater samples during a one-month cruise in the South China Sea. For seawater at
concentrations of 20.6, 82.5, 206.2 nM orthophosphate, the relative standard deviations (RSD) (n = 6), determined daily for 6 days on board ship were 4.45%, 4.73% and 6.75%, respectively. Five seawater samples collected
in the Station SEATS (South East Asia Time Series Station at 18°N, 116°E) were analyzed using the present method both on board
and in a land-based laboratory, as well as with the magnesium hydroxide-induced coprecipitation (MAGIC) method, and showed
no significant difference according to the statistical t-test. 相似文献
3.
In parallel with the process of lead removal from gasoline in Italy, a research programme was undertaken to study the lead content of Adriatic coastal seawater. In the period 2000–2004 seawater was collected systematically at three sites along the coast line close to the city of Ancona: (i) the mouth of the River Esino, (ii) an area close to the Api refinery and (iii) Portonovo beach, a less impacted zone located along the coast of Mt. Conero. All samples were analyzed by Square-Wave Anodic-Stripping Voltammetry (SWASV). The results show that dissolved Pb content in coastal seawater diminished from an overall median value of 0.25 nmol/L in 2000–2001 to 0.12 nmol/L in 2003–2004, with a decrease of about 50% (statistically significant at 95% significance level). This decrease has been correlated to the concurrent decrease of lead consumption in gasoline in Italy which led to a reduction of ~ 65% Pb emissions into the atmosphere in the same period (r = 0.8791, p < 0.05). 相似文献
4.
海水溶解有机物(dissolvedorganicmatter,DOM)中含有的生物活性物质在海洋生态系统中作用巨大,但因缺乏适合的分离提取方法而严重阻碍了对其不同组分在生态系统中作用的探索。固相萃取法对富集提取海水DOM十分有效,在用其提取海水DOM时,海水pH对活性物质提取效果的影响很大,但目前针对海水的这种影响尚存在很大争议。本文以天然近海海水作为基质,探究不同pH条件下用亲水-疏水平衡(hydrophilic-lipophilicbalanced,HLB)固相萃取小柱萃取海水中活性分子的提取效率,并使用高效液相色谱-四极杆飞行时间质谱(HPLC-Q-TOF-MS)在负离子(ESI-)模式下检测解析提取物的组成。研究结果表明,当海水样品pH为中性和强酸性时都能获得较好的提取效率,随着pH的降低,提取物质谱的整体响应值降低,但可识别的谱峰数目增加,提取出有机物的分子量和性质差异都更广泛。分析提取物分子在范克雷维伦(van Krevelen)图和质荷比-氢碳比(m/z-H/C)图上的分布发现,中性条件适合提取饱和度较高的小分子化合物,而具有生物活性的带有不饱和基团的化合物及蛋白质、糖类等生物大分子在强酸性提取条件时提取效果和分辨率更好。综合提取效率、有效峰数目和分子组成特征考虑,用HLB固相萃取小柱提取近海海水中的小分子活性物质时,将海水样品pH调节为2较为适宜。 相似文献
5.
A low-blank pre-concentration procedure is described for the analysis of picomolar iron (Fe) in seawater by isotope dilution high-resolution inductively coupled plasma mass-spectrometry (HR-ICPMS). The procedure uses a two-step Mg(OH)2 co-precipitation procedure to extract Fe from a 50 ml seawater sample into a 100 μl 4% nitric acid (HNO3) solution followed by HR-ICPMS measurement. The high pre-concentration ratio ( 500:1) achieved by the procedure minimizes the Fe blank due to ICPMS instrumental Fe background and results in a detection limit of 2 pM and a precision of 4% at the 50 pM Fe level. The measurement of a low-Fe seawater sample spiked with gravimetric Fe standard shows that the method can clearly distinguish 0.01 nM Fe from 0.02 nM Fe in seawater with high accuracy. The method is demonstrated by the analysis of dissolved Fe in the equatorial Pacific Ocean. 相似文献
6.
A chemoreduction-purge-and-trap gas chromatographic method has been developed for the determination of trace dimethylsulfoxide (DMSO) in seawater. In the analysis procedure, DMSO was first reduced to dimethylsufide (DMS) by sodium borohydride and then the produced DMS was analyzed using the purge-and-trap technique coupled with gas chromatographic separation and flame photometric detection. Under the optimum conditions, 97% DMSO was reduced in the standard solution samples with a standard deviation of 5% (n=5). The detection limit of DMSO was 2.7 pmol of sulfur, corresponding to a concentration of 0.75 nmol/L for a 40 ml sample. This method was applied to determine the dissolved DMSO (DMSOd) and particulate DMSO (DMSOp) concentrations in the surface seawater of the Jiaozhou Bay, and the results showed that the DMSOd and DMSOp concentrations varied from 16.8 to 921.1 nmol/L (mean:165.2 nmol/L) and from 8.0 to 162.4 nmol/L (mean:57.7 nmol/L), respectively. The high concentrations of DMSOp were generally found in productive regions. Consequently, a significant correlation was found between the concentrations of DMSOp and chlorophyll a, suggesting that phytoplankton biomass might play an important role in controlling the distribution of DMSOp in the bay. Moreover, in the study area, the concentrations of DMSOd were significantly correlated with the levels of DMS, implying that the production of DMSOd is mainly via photochemical and biological oxidation of DMS. 相似文献
7.
A method has been developed for the determination of ammonium concentration and isotopic enrichment in seawater samples at the low nanomolar range (10–100 nmol/kg). It is based on the reaction of phenol/hypochlorite with ammonium to form indophenol, with subsequent solid phase extraction, derivatisation and analysis by Gas Chromatography Mass Spectrometry. The precision of the method was maximised by incorporating a deuterated indophenol internal standard. A system was developed which generated seawater with extremely low ammonium concentrations thus matching sample and standard matrices for quantitative analysis. Data are presented from a study of ammonium regeneration rates at three stations in the oligotrophic North–East Atlantic where ambient ammonium concentrations were < 21 nmol/kg. Results suggested that ammonium availability for phytoplankton was limited by the rate of ammonium regeneration. Efficient ammonium assimilation contributed to the very low ambient ammonium concentrations measured at these stations. The study highlights the need for the accurate determination of ammonium regeneration rates in studies of new production, particularly in extreme oligotrophic conditions. If not corrected for isotope dilution, f-ratio estimates may be overestimated by 10.7–13.7%. 相似文献
8.
9.
A.C. Fischer J.J. Kroon T.G. Verburg T. Teunissen H.Th. Wolterbeek 《Marine Chemistry》2007,107(4):533-546
Iron chemistry in seawater has been extensively studied in the laboratory, mostly in small-volume sample bottles. However, little has been reported about iron wall sorption in these bottles. In this paper, radio-iron 55Fe was used to assess iron wall adsorption, both in terms of capacity, affinity and kinetics. Various bottle materials were tested. Iron sorption increased from polyethylene/polycarbonate to polymethylmetacrylate (PMMA)/high-density polyethylene/polytetrafluoroethylene to glass/quartz, reaching equilibrium in a 25–70 h period. PMMA was studied in more detail: ferric iron (Fe(III)) adsorbed on the walls of the bottles, whereas ferrous iron (Fe(II)) did not. Considering that in seawater the inorganic iron pool mostly consists of ferric iron, the wall will be a factor that needs to be considered in bottle experiments.The present data indicate that for PMMA with specific surface (S)-to-volume (V) ratio S/V, both iron capacity (42 ± 16 × 10− 9 mol/m2 or 1.7 × 10− 9 mol/L recalculated for the S/V-specific PMMA bottles used) and affinity (log KFe'W = 11.0 ± 0.3 m2/mol or 12.4 ± 0.3 L/mol, recalculated for the S/V-specific PMMA bottles used) are of similar magnitude as the iron capacity and -affinity of the natural ligands in the presently used seawater and thus cannot be ignored.Calculation of rate constants for association and dissociation of both Fe'L (iron bound to natural occurring organic ligands) and Fe'W (iron adsorbed on the wall of vessels) suggests that the two iron complexes are also of rather similar kinetics, with rate constants for dissociation in the order of 10 −4–10− 5 L/s and rate constants for association in the order of 108 L/(mol s). This makes that iron wall sorption should be seriously considered in small-volume experiments, both in assessments of shorter-term dynamics and in end-point observations in equilibrium conditions. Therefore, the present data strongly advocate making use of iron mass balances throughout in experiments in smaller volume set-ups on marine iron (bio) chemistry. 相似文献
10.
M. Bourquin P. van Beek J.-L. Reyss M. Souhaut M.A. Charette C. Jeandel 《Marine Chemistry》2008,109(3-4):226
In the framework of the KEOPS project (KErguelen: compared study of the Ocean and the Plateau in Surface water), we aimed to provide information on the water mass pathways and vertical mixing on the Kerguelen Plateau, Southern Ocean, based on 228Ra profiles. Because 228Ra activities are extremely low in this area (~ 0.1 dpm/100 kg or ~ 2.10− 18 g kg− 1), the filtration of large volumes of seawater was required in order to be able to detect it with minimal uncertainty. This challenging study was an opportunity for us to test and compare methods aimed at removing efficiently radium isotopes from seawater. We used Mn-fiber that retains radium and that allows the measurement of all four radium isotopes (226Ra, 228Ra, 223Ra, 224Ra). First, we used Niskin bottles or the ship's seawater intake to collect large volumes of seawater that were passed onto Mn-fiber in the laboratory. Second, we filled cartridges with Mn-fiber that we placed in tandem on in situ pumps. Finally, we fixed nylon nets filled with Mn-fiber on the frame of in situ pumps to allow the passive filtration of seawater during the pump deployment.Yields of radium fixation on the cartridges filled with Mn-fiber and placed on in situ pumps are ca. 30% when combining the two cartridges. Because large volumes of seawater can be filtered with these pumps, this yields to effective volumes of 177–280 kg (that is, higher than that recovered from fourteen 12-l Niskin bottles). Finally, the effective volume of seawater that passed through Mn-fiber placed in nylon nets and deployed during 4 h ranged between 125 and 364 kg. Consequently, the two techniques that separate Ra isotopes in situ are good alternatives for pre-concentrating radium from seawater. They can save ship-time by avoiding repeated CTD casts to obtain the large volumes of seawater. This is especially true when in situ pumps are deployed to collect suspended particles. However, both methods only provide 228Ra/226Ra ratios. The determination of the 228Ra specific activity is obtained by multiplying this ratio by the 226Ra activity measured in a discrete sample collected at the same water depth. 相似文献
11.
Marielle Lacombe Vronique Garon Maurice Comtat Louise Oriol Joël Sudre Danile Thouron Nadine Le Bris Christine Provost 《Marine Chemistry》2007,106(3-4):489-497
Silicate has been determined in sea water by four different electrochemical methods based on the detection of the silicomolybdic complex formed in acidic media by the reaction between silicate and molybdenum salts. The first two methods are based on the addition of molybdate and protons in a seawater sample in an electrochemical cell. Cyclic voltammetry presents two reduction and two oxidation peaks giving four values of the concentration and therefore increasing the precision. Then chronoamperometry is performed on an electrode held at a constant potential. A semi-autonomous method has been developed based on the electrochemical anodic oxidation of molybdenum, the complexation of the oxidation product with silicate and the detection of the complex by cyclic voltammetry. This method is tested and compared with the classical colorimetric one during ANT XXIII/3 cruise across Drake Passage (January–February 2006). The detection limit is 1 μM and the deviation between both methods is less than 3% for concentrations higher than 10 μM. Finally a complete reagentless method with a precision of 2.6% is described based on the simultaneous formation of the molybdenum salt and protons in a divided electrochemical cell. This latter method should be very useful for developing a reagentless sensor suitable for long term in situ deployments on oceanic biogeochemical observatories. 相似文献
12.
离子色谱-电感耦合等离子体质谱联用测定海水中的IO3^-和I^- 总被引：1，自引：0，他引：1
研究了离子色谱-电感耦合等离子体质谱（IC-ICPMS）联用技术直接进样测定海水中IO3^-和I^-的方法．采用IonPacAG23离子色谱保护柱分离IO3^-和I^-,以浓度4．0mmol／dm3的KOH为流动相,流量为1．0cm3／min,每个样品的分析时间为2．5min．采用2．5×10^-3cm^3的进样量,IO3^-和I^-的检出限分别达到0．6和0．4nmol／dm2,可满足海水中碘形态的定量分析．该方法的IO3^-和I^-浓度范围在2．0nmol／dm3～2．0μmol／dm3． 相似文献
13.
Benzyl butyl phthalate (BBP) is an endocrine-disrupting chemical, and its sorption behaviour on marine sediments was investigated. BBP sorption on the sediments was a rapid process, which could reach equilibrium in 6 h. The sorption equilibrium results could be well described by a linear isotherm. The BBP partition coefficient, Kd, varied from 7.16 to 12.54 L/g in approximately proportion to the organic content of the sediments. After H2O2 oxidation for removing the organic material from the sediments, the Kd values were reduced by more than 70%, but the organic normalised partition coefficient averaged 2165 L/g for the H2O2-treated sediments, which was more than three times of 598 L/g for the raw sediments. The sorption of BBP on the sediments increased with a decrease in temperature and an increase in salinity. A salting constant of 1.14 L/mol was obtained for BBP in artificial seawater. These research findings are of importance to an assessment of the fate and transport of BBP and other similar endocrine-disrupting chemicals (EDCs) in seawater–sediment systems. 相似文献
14.
Submarine groundwater discharge (SGD) to coastal southern Rhode Island was estimated from measurements of the naturally-occurring radioisotopes 226Ra (t1/2 = 1600 y) and 228Ra (t1/2 = 5.75 y). Surface water and porewater samples were collected quarterly in Winnapaug, Quonochontaug, Ninigret, Green Hill, and Pt. Judith–Potter Ponds, as well as nearly monthly in the surface water of Rhode Island Sound, from January 2002 to August 2003; additional porewater samples were collected in August 2005. Surface water activities ranged from 12–83 dpm 100 L− 1 (60 dpm = 1 Bq) and 21–256 dpm 100 L− 1 for 226Ra and 228Ra, respectively. Porewater 226Ra activities ranged from 16–736 dpm 100 L− 1 (2002–2003) and 95–815 dpm 100 L− 1 (2005), while porewater 228Ra activities ranged from 23–1265 dpm 100 L− 1. Combining these data with a simple box model provided average 226Ra-based submarine groundwater fluxes ranging from 11–159 L m− 2 d− 1 and average 228Ra-derived fluxes of 15–259 L m− 2 d− 1. Seasonal changes in Ra-derived SGD were apparent in all ponds as well as between ponds, with SGD values of 30–472 L m− 2 d− 1 (Winnapaug Pond), 6–20 L m− 2 d− 1 (Quonochontaug Pond), 36–273 L m− 2 d− 1 (Ninigret Pond), 29–76 L m− 2 d− 1 (Green Hill Pond), and 19–83 L m− 2 d− 1 (Pt. Judith–Potter Pond). These Ra-derived fluxes are up to two orders of magnitude higher than results predicted by a numerical model of groundwater flow, estimates of aquifer recharge for the study period, and values published in previous Ra-based SGD studies in Rhode Island. This disparity may result from differences in the type of flow (recirculated seawater versus fresh groundwater) determined using each technique, as well as variability in porewater Ra activity. 相似文献
15.
Jianrong Lin 《海洋学报(英文版)》2022,41(3):103-108
A new spectrophotometric method based on a liquid waveguide capillary cell for an enhanced detection was developed to measure nanomolar iodate concentrations. This method has a detection limit and precision of 1–2 nmol/L, which is equivalent to 10% that of conventional methods, a recovery of 97.7%–104.0%, and a working range of 10–120 nmol/L. Water samples were collected from three estuaries and one coastal ocean for testing, and the proposed technique detected as low as 11 nmol/L and 18 nmol/L ... 相似文献
16.
β-dimethylsulfoniopropionate (DMSP) and dimethylsulfide (DMS) concentrations were recorded from September 1999 to September 2000 in two geographically close ecosystems, differently affected by eutrophication: the Little Bay of Toulon and the Niel Bay (N.W. Mediterranean Sea, France). Little Bay had higher nutrient levels ([NO3−]max. = 30.3 μM; [PO43−]max. = 0.46 μM) and higher chlorophyll a concentrations ([chl a]mean = 2.4 μg/L) compared to Niel Bay ([NO3−]max. = 19.7 μM; [PO43−]max. = 0.17 μM; [chl a]mean = 0.4 μg/L). In the two sites, we measured dissolved (DMSPd < 0.2 μm) and particulate DMSP (DMSPp > 0.2 μm) concentrations. The DMSPp was particularly analysed in the 0.2–5, 5–90 and > 90 μm fractions. In the eutrophicated Little Bay, DMSPd concentrations showed a clear seasonality with high values from January to March (124–148 nM). The temporal profile of the DMSPp concentrations was similar, peaking in February–March (38–59 nM). In the less eutrophic Niel Bay, DMSPp concentrations were much lower (6–9 nM in March–April), whereas DMSPd concentrations were relatively high (110–92 nM in February–March). DMS concentrations were elevated from the end of the winter to the spring in Little Bay, ranging from 3 nM in October to 134 nM in March. In the less eutrophic Niel Bay, lower DMS levels were observed, generally not exceeding 20 nM. Each particulate fraction (0.2–5; 5–90; > 90 μm) contained less DMSP in Niel Bay than in Little Bay. At both sites, the 5–90 μm fraction made up most of the DMSPp. This 5–90 μm fraction consisted of microphytoplankton, principally Dinophyceae and Bacillariophyceae. The 5–90 μm biomass calculated from cell biovolumes, was more abundant in Little Bay where the bloom at the end of the winter (165 μg/L in March) occurred at the same time as the DMSP peaks. The estimated DMSPp to biomass ratio for the 5–90 μm fraction was always higher in Little Bay than in Niel Bay. This suggests that the high DMSP levels recorded in Little Bay were not only due to a large Dinophyceae presence in this ecosystem. Indeed, the peak of DMSPp to biomass ratio obtained from cell biovolumes (0.23 nmol/μg in March) was consistent with the proliferation of Alexandrium minutum. This Dinophyceae species may account for between 50% (2894 cells/L) and 63% (4914 cells/L) of the total phytoplankton abundance in the Little Bay of Toulon. 相似文献
17.
A fluorescence-based chemistry has been developed for the detection of nitrite and nitrate (as excess nitrite following reduction of nitrate to nitrite). Detection limits are 4.6 and 6.9 nM, respectively. The technique capitalizes on the triple bond between the two nitrogen atoms within the diazonium ion formed via the well-known reaction between an acidified nitrite sample and an aromatic primary amine. Fluorescence of π-electrons within this bond allows this reaction to be probed with standard fluorescence spectroscopy. Reverse Flow Injection Analysis (rFIA) is used to correct for background fluorescence from leachates and naturally occurring dissolved organic matter (DOM). Comparisons of samples analyzed for nitrite with this technique and with a highly-sensitive chemiluminescent method [Braman, R.S., Hendrix, S.A., 1989. Nanogram nitrite and nitrate determination in environmental and biological materials by vanadium (III) reduction with chemiluminescence detection. Analytical Chemistry, 61 (24) 2716–2718] showed excellent agreement between the two methods (slope=0.9996 and r2=0.9956). These fluorescent nitrite and nitrate + nitrite chemistries were coupled in a sensor package with a modified version of a fluorescent ammonia chemistry [Jones, R.D., 1991. An improved fluorescence method for the determination of nanomolar concentrations of ammonia in natural waters, Limnology and Oceanography. 36(4) 814–819], which also has a nanomolar detection limit. The throughput rate of the fully automated three-channel instrumentation is 18 samples per hour. A field experiment demonstrated the capability of the nutrient sensor package to determine horizontal gradients in nitrate, nitrite, and ammonia in oligotrophic surface waters. 相似文献
18.
A new method for the quantification of different redox-species of molybdenum (V and VI) in seawater 总被引：1，自引：0，他引：1
A new method for the direct determination of reduced and oxidized Mo species (Mo (V) and Mo (VI)) in seawater was developed and used for the first time. The method includes the complexation of Mo (V) with tartrate, solid phase extraction of the Mo (V)–tartrate complex by a XAD 7HP resin, followed by elution with acidic acetone. In this study, the eluted Mo (V) was quantified by graphite furnace atomic absorption spectrometry. The detection limit of this protocol was on the order of 0.2 nM. The analytical precision was 10% of ~ 10 nM. This method was successfully applied to the determination of Mo (V) and Mo (VI) in surface and bottom waters at the head of Peconic River Estuary. Total Mo (Mo (V) + Mo (VI)) ranged from 100–120 nM in most bottom saline waters, and 2.5–15 nM for surface fresher waters. Concentrations of Mo (V) in these environments ranged from 0 nM to ~ 15 nM, accounting for 0%–15% of the total dissolved Mo pool. The time series experiments showed that the Mo speciation changed within 1 h after the water collection, and therefore it is strongly suggested that speciation analysis be carried out within the first 15 min. However, since these are the first Mo speciation data in concentration ranges typical of normal marine and coastal waters, additional research may be required to optimize the methodology and further explore Mo cycling mechanisms. 相似文献
19.
Joan E. Cartes Francesc Maynou Emanuela Fanelli Chiara Romano Valeria Mamouridis Vanesa Papiol 《Journal of Sea Research》2009,61(4):244-257
The distribution of megabenthic epifauna (invertebrates) in the Balearic Basin (western Mediterranean) has been analyzed at depths between 427 and 2265 m after compiling samplings performed in 1985–1992 and 2007–2008 with an OTSB-14 bottom trawl. 84 epibenthic taxa of invertebrates (excluded decapod crustaceans) were collected. Epibenthic assemblages were organized in five groups (n-MDS analyses) as a function of increasing depth: upper slope assemblage, U, hauls between 427 and 660 m; middle slope assemblages M1 and M2, hauls between 663–876 m and 864–1412 m, respectively; lower slope assemblages L1 and L2, hauls between 1488–1789 m and 1798–2265 m, respectively). We found significant differences in assemblage composition between all depth-adjacent pairs of groups. Trends in the distribution of biomass vs. depth and within assemblages varied when hauls taken over insular were compared to those over mainland slopes. Over insular slopes we found (n-MDS) only four distinct depth assemblages, with significant differences between all depth-adjacent group pairs, except between L1 and L2. Over the mainland slope, two peaks of biomass situated at U (427–660 m) and at L1 (1488–1789 m) were clearly identified, attributable to the echinoid Brissopsis lyrifera and holothurian Molpadia musculus at U and to the synallactid holothurian Mesothuria intestinalis at L1. The distribution of biomass vs. depth on insular slopes did not follow this pattern, showing no significant biomass peak below 1000 m and a total biomass an order of magnitude lower than adjacent to the mainland. After compiling available environmental data over the mainland slope off Barcelona, we found coincidence between the peak biomass of Mesothuria intestinalis and: i) a significant increase of labile OM (%OrgC, C/N, hydrolizable aminoacids–EHAA, and the EHAA/THAA-total hydrolizable aminoacids-ratio) over 1600 m; and ii) an increase of turbidity and T at 1500–1600 m in February 2008. We suggest that such OM inputs must likely be associated to the formation of nepheloid layers close to submarine canyons, probably associated with oceanographic processes in deep water masses in the area. This would explain why aggregations of M. intestinalis were linked to the mainland part of the Balearic basin, with highest densities located south of canyons. If hotspots of biomass as cited here for M. intestinalis are regulated by factors such as river inputs, both natural climatic changes (e.g. changes in rainfall regimes) and human impact (e.g. river damming) may affect deep-Mediterranean communities below 1000 m. 相似文献
20.
Dissolved oxygen in seawater has been determined by using the Winkler's reaction scheme for decades. An interference in this reaction scheme that has been heretofore overlooked is the presence of naturally occurring iodate in seawater. Each mole of iodate can result in an apparent presence of 1.5 mol of dissolved oxygen. At the concentrations of iodate in the surface and deep open ocean, it can lead to an overestimation of 0.52 ± 0.15 and 0.63 ± 0.05 μmol kg− 1 of oxygen in these waters respectively. In coastal and inshore waters, the effect is less predictable as the concentration of iodate is more variable. The solubility of oxygen in seawater was likely overestimated in data sources that were based on the Winkler's reaction scheme for the determination of oxygen. The solubility equation of García and Gordon [Garcia H.E., Gordon, L.I., 1992. Oxygen solubility in seawater: Better fitting equations. Limnol. Oceanogr. 37, 1307–1312] derived from the results of Benson and Krause [Benson, F.B., Krause, D. Jr., 1984. The concentration and isotopic fractionation of oxygen dissolved in freshwater and seawater in equilibrium with the atmosphere. Limnol. Oceanogr. 29, 620–632] is free from this source of error and is recommended for general use. By neglecting the presence of iodate, the average global super-saturation of oxygen in the surface oceans and the corresponding efflux of oxygen to the atmosphere both have been overestimated by about 8%. Regionally, in areas where the degree of super-saturation or under-saturation of oxygen in the surface water is small, such as in the tropical oceans, the net air–sea exchange flux can be grossly under- or overestimated. Even the estimated direction of the exchange can be reversed. Furthermore, the presence of iodate can lead to an overestimation of the saturation anomaly of oxygen in the upper ocean attributed to biological production by 0.23 ± 0.07%. AOU may have been underestimated by 0.52 ± 0.15 and 0.63 ± 0.05 μmol kg− 1 in the surface mixed layer and deep water, while preformed phosphate and preformed nitrate may have been overestimated by 0.004 ± 0.001 and 0.06 ± 0.02 μmol kg− 1 in the surface mixed layer, and 0.005 ± 0.0004 and 0.073 ± 0.006 μmol kg− 1 in the deep water. These are small but not negligible corrections, especially in areas where the values of these parameters are small. At the increasing level of sophistication in the interpretation of oxygen data, this source of error should now be taken into account. Nevertheless, in order to avoid confusion, an internationally accepted standard needs to be adopted before these corrections can be applied. 相似文献