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1.
Depth profiles of the naturally-occurring radionuclides 238U, 234U, 226Ra, 228Ra and 228Th were obtained in two diverse anoxic marine environments; the permanently anoxic Framvaren Fjord in southern Norway and the intermittently anoxic Saanich Inlet in British Columbia. Concentrations of total H 2S were over three orders of magnitude greater in the anoxic bottom waters of Framvaren Fjord compared to those in Saanich Inlet.In Framvaren Fjord, the O 2/H 2S interface was located at 17 m. While dissolved 238U behaved conservatively throughout the oxic and anoxic water columns, concentrations based on the 238U/salinity ratio in oxic oceanic waters were almost 30% lower. Dissolved 226Ra displayed a sharp maximum just below the O 2/H 2S interface, coinciding with dissolved Mn (II) and Fe (II) maxima in this zone. It is suggested that reductive dissolution of Fe-Mn oxyhydroxides remobilizes 226Ra in this region.In Saanich Inlet, the O 2/H 2S interface was located at 175 m. Dissolved 238U displayed a strongly nonconservative distribution. The depth profiles of dissolved 226Ra and 228Th correlated well with the distribution of dissolved Mn (II) in the suboxic waters above the O 2/H 2S interface, suggesting that reduction of particulate Mn regulates the behavior of 226Ra and 228Th in this region.Removal residence times for dissolved 228Th in the surface oxic waters of both systems are longer than those generally reported for particle-reactive radionuclides in coastal marine environments. In the anoxic waters of Framvaren Fjord and Saanich Inlet, however, the dissolved 228Th removal residence times are quite similar to values reported for dissolved 210Pb in the anoxic waters of the Cariaco Trench and the Orca Basin. This implies that the geochemistries of Th and Pb may be similar in anoxic marine waters. 相似文献
2.
热液喷口附近的羽状流中存在明显的化学及浊度异常,通过探测这些异常可判断是否存在热液喷口及确定喷口的具体位置。本文研制了一款可用于探测热液喷口的多通道化学传感器,该传感器具有体积小、精度高的特点,且可在4000米深海中进行工作。该化学传感器共配备五个全固态电极,一个为参比电极,其余四个为离子选择性电极,并且可根据所测量的化学离子进行更换。本文基于该化学传感器共进行了两组实验。在第一组浅海试验中,化学传感器集成了pH,Eh,CO 32-和SO 42-电极,在浅海海域中测量对应化学量,结果表明该化学传感器可在实际应用中获得高精度、稳定的测量数据。第二组实验为深海热液探测,装配了pH,Eh,CO 32-和H 2S电极的化学传感器在西南印度洋中脊区域的29次测线中投入使用,共获得有效数据27组。通过对测量所得到的化学量进行分析,本文提出了一种确定热液喷口的化学异常探测方法,若某时间段内Eh和H 2S的电势降低,而pH和CO 32-的电势上升则可判定存在化学异常。利用该方法对27组有效数据进行分析,共发现5个潜在的热液喷口。实验结果表明,该化学传感器可有效地探测由热液引起的化学异常,适用于实际热液探测中。 相似文献
3.
In June 1981, dissolved Zn, Cd, Cu, Ni, Co, Fe, and Mn were determined from two detailed profiles in anoxic Baltic waters (with extra data for Fe and Mn from August 1979). Dramatic changes across the O 2H 2S interface occur in the abundances of Cu, Co, Fe, and Mn (by factors of ?100). The concentrations of Zn, Cd, and Ni at the redox front decrease by factors between 3 to 5.Equilibrium calculations are presented for varying concentrations of hydrogen sulfide and compared with the field data. The study strongly supports the assumption that the solubility of Zn, Cd, Cu, and Ni is greatly enhanced and controlled by the formation of bisulfide and(or) polysulfide complexes. Differences between predicted and measured concentrations of these elements are mainly evident at lower ΣH 2S concentrations.Cobalt proved to be very mobile in anoxic regions, and the results indicate that the concentrations are limited by CoS precipitation. The iron (Fe 2+) and manganese (Mn 2+) distribution in sulfide-containing waters is controlled by total flux from sediment-water interfaces rather than by equilibrium concentrations of their solid phases (FeS and MnCO 3). The concentrations of these metals are therefore expected to increase with prolonged stagnation periods in the basin. 相似文献
4.
Vertical profiles of dissolved and particulate 210Po and 210Pb were measured across the redox transition zone at Station F1 in Framvaren Fjord, Norway. In this fjord, a sharp decrease in pH above the O 2/H 2S interface facilitates the aerobic dissolution of MnO 2. In contrast, Fe(II) concentrations begin to increase only at the O 2/H 2S interface depth. Activity profiles reveal that dissolved 210Po and 210Pb are sequestered efficiently by particulates in surface waters. As polonium-210 and lead-210 activities descend down into the aerobic manganese reduction (AMR) zone, they are remobilized during the reductive dissolution of the carrier phase oxyhydroxides. Both 210Po and 210Pb are highly enriched at the O 2/H 2S interface where an active community of microbes, such as anoxygenic phototrophs (e.g., Chromatium, Chlorobium sp.), thrives. The coincident peaks in 210Po, 210Pb and microbial biomass suggest a strong biological influence on the behavior of these radionuclides. There is a strong covariance between the vertical distribution of Mn and Pb, indicating that their redox cycling is closely coupled and is likely microbially mediated. 相似文献
5.
The thermodynamics and kinetics of the H 2S system in natural waters have been critically reviewed. Equations have been derived for the solubility and ionization of H 2S in water and seawater as a function of salinity, temperature and pressure. Pitzer parameters for the interaction of the major cations (Na +, Mg 2+ and Ca 2+) with HS − have been determined to allow one to calculate values of pK1* in various ionic media. The limited data available for the interaction of trace metals for HS − are summarized and future work is suggested.The kinetics of oxidation of H 2S have also been examined as a function of pH, temperature, and salinity. The discrepancies in the available data are largely due to the different [O 2]/[HS−] ratios used in various studies. Over a limited pH range (6–8) the pseudo first order rate constant for the oxidation is shown to be directly proportional to the activity of HS −. Further studies are suggested to examine the effect of ionic media and temperature on the rate of oxidation. 相似文献
6.
The rates of the reduction of Cr(VI) with S(IV) were measured in deaerated NaCl solution as a function of pH, temperature and ionic strength. The rates of the reaction were found to be first order with respect to Cr(VI) and second order with respect to S(IV), in agreement with previous results obtained at concentrations two order higher than the present study. The reaction also showed a first-order dependence of the rates on the concentration of the proton and a small influence of temperature with an apparent energy of activation Δ Happ of 22.8 ± 3.4 kJ/mol. The rates were independent of ionic strength from 0.01 to 1 M. The rate of Cr(VI) reduction is described by the general expression −d[Cr(VI)]/dt=k[Cr(VI)][S(IV)]2 | where k (M− 2 s− 1) can be determined from thein the pH range 2 to 5, from 5 to 40 °C and 0.01 to 1 M.The effect of pH and ionic strength on the reaction suggest that the rates are due towhere H2A = H2CrO4, HA = HCrO4−, H2B = H2SO3 and HB = HSO3−. The overall rate expression over the investigated pH range can be determined fromk=kH2A–H2B(αH2A)(αH2B)2+kHA–H2B(αHA)(αH2B)2+kH2A–HB(αH2A)(αHB)2
with kH2A−H2B = 5.0 × 107, kHA–H2B = 1.5 × 106 and kH2A–HB = 6.7 × 107.Fe(III) in the range 1.5 to 20 μM exerts a small catalytic effect on the reaction and significantly lowers the initial concentration of Cr(VI) compared to the nominal value. Contrary to Fe(III), formaldehyde (20 to 200 μM) reacts with S(IV) to form the hydroxymethanesulfonate adduct (CH2OHSO3−), which does not react with Cr(VI). Major cations Mg2+ and some minor elements such as Ba2+ and Cu2+ did not affect the rates. The application of this rate law to environmental conditions suggest that this reaction may have a role in acidic solutions (aerosols and fog droplets). This reaction becomes more important in the presence of high Fe(III) and low HMS concentrations, contributing to affect the atmospheric transport of chromium species and the distribution of redox species of chromium, which reach surface water from atmospheric depositions. 相似文献
7.
The expression for the bottom convection intensity is derived from the equality of the advective vertical flux of H
2S within 1000–2000 m to the diffusion turbulent flow close to the H
2S zone upper boundary. The upwelling rate, which is expressed via the H
2S concentration in deep waters and the gradient of the H
2S concentration near the upper boundary, is 10
–4 cm/s. It is shown that the H
2S diffusion flux in deep waters is an order less than the advective one. The conclusion that below 1000 m the age of H
2S does not exceed 30 years and H
2S reaches the upper boundary in approximately 150 years is derived.Translated by Mikhail M. Trufanov.
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8.
The absorption of anthropogenic CO
2 and atmospheric deposition of acidity can both contribute to the acidification of the global ocean. Rainfall
pH measurements and chemical compositions monitored on the island of Bermuda since 1980, and a long-term seawater CO
2 time-series (1983–2005) in the subtropical North Atlantic Ocean near Bermuda were used to evaluate the influence of acidic deposition on the acidification of oligotrophic waters of the North Atlantic Ocean and coastal waters of the coral reef ecosystem of Bermuda. Since the early 1980's, the average annual wet deposition of acidity at Bermuda was 15 ± 14 mmol m
− 2 year
− 1, while surface seawater
pH decreased by 0.0017 ± 0.0001
pH units each year. The gradual acidification of subtropical gyre waters was primarily due to uptake of anthropogenic CO
2. We estimate that direct atmospheric acid deposition contributed 2% to the acidification of surface waters in the subtropical North Atlantic Ocean, although this value likely represents an upper limit. Acidifying deposition had negligible influence on seawater CO
2 chemistry of the Bermuda coral reef, with no evident impact on hard coral calcification.
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9.
During CREAMS expeditions,
fCO
2 for surface waters was measured continuously along the cruise tracks. The
fCO
2 in surface waters in summer varied in the range 320–440 μatm, showing moderate supersaturation with respect to atmospheric
CO
2. In winter, however,
fCO
2 showed under-saturation of CO
2 in most of the area, while varying in a much wider range from 180 to 520 μatm. Some very high
fCO
2 values observed in the northern East Sea (Japan Sea) appeared to be associated with the intensive convection system developed
in the area. A gas-exchange model was developed for describing the annual variation of
fCO
2 and for estimating the annual flux of CO
2 at the air-sea interface. The model incorporated annual variations in SST, the thickness of the mixed layer, gas exchange
associated with wind velocity, biological activity and atmospheric concentration of CO
2. The model shows that the East Sea releases CO
2 into the atmosphere from June to September, and absorbs CO
2 during the rest of the year, from October through May. The net annual CO
2 flux at the air-sea interface was estimated to be 0.032 (±0.012) Gt-C per year from the atmosphere into the East Sea. Water
column chemistry shows penetration of CO
2 into the whole water column, supporting a short turnover time for deep waters in the East Sea.
This revised version was published online in August 2006 with corrections to the Cover Date.
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10.
Hydrogen peroxide (H
2O
2) was measured in marine surface waters of the eastern Atlantic Ocean between 25°N and 25°S. H
2O
2 concentrations decreased from 80 nM in the north to 20 nM in the south, in agreement with earlier observations. A diel cycle of H
2O
2 production as a function of sunlight in surface waters was followed twice whilst the ship steamed southward. Around 23°N a distinct diel cycle could be measured which correlated well with irradiance conditions.The wavelength dependency of H
2O
2 formation was studied near the equator. For 16 hours, water samples were incubated with wavelength bands of the solar spectrum, i.e. visible (VIS: 400–700 nm), VIS and ultraviolet A radiation (UVAR: 320–400 nm) and VIS, UVAR and ultraviolet B radiation (UVBR: 280–320 nm). A significant relationship was found between wavelength band and the production of H
2O
2. In addition, a clear positive relationship between intensity and production was found. UVAR was 6.5 times more efficient than VIS in producing 1 nM of H
2O
2, whereas UVBR was 228 times more efficient than VIS. When these data were weighted with respect to the energy of the solar spectrum at zenith hour, 28% of the H
2O
2 was formed by VIS, 23% was formed by UVAR and 48% was formed by UVBR. Considering the strong attenuation of UVBR in marine waters as compared with UVAR and VIS radiation, the role of UVAR deeper in the water column is recognised. Furthermore results of this research emphasise the importance of VIS radiation in the formation of H
2O
2.
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11.
High resolution measurements of carbon dioxide and oxygen were made in surface waters of the central Arkona Sea (Baltic Sea) from May 2003 to September 2004. Sensors for CO
2 partial pressure (
pCO
2w) and oxygen (O
2) concentration were mounted in 7 m depth on a moored platform which is used for hydrographic and meteorological monitoring. The
pCO
2w data were obtained in half hour intervals and O
2 was measured each hour as an average of a 10 min measurement. To check the performance of the sensors,
pCO
2w and O
2 were determined by shipboard measurements on a research vessel which visited the site in 1–2 month intervals. In addition,
pCO
2w was measured on a “volunteer observing ship” (VOS) passing the platform each second day at a distance of about 25 km. Minima of 220 to 250 μatm of
pCO
2w were observed at the time of the spring bloom and a cyanobacteria bloom in mid-summer. During winter the
pCO
2w was mostly close to equilibrium with the atmosphere but maxima of 430 to 530 μatm were also observed. The seasonality of oxygen and
pCO
2w showed an opposing pattern. From a multiple regression analysis, we concluded that two processes primarily controlled
pCO
2w during our study: biological turnover and mixing. A parameterization, based on apparent oxygen utilisation (AOU) and salinity (
S) only (
pCO
2w = 1.23 AOU + 43
S), reproduced the seasonality of
pCO
2w in surface water reasonably well. Based on our
pCO
2, salinity, and temperature data set, we attempted to separate processes changing total inorganic carbon concentrations (
CT) by using an alkalinity–salinity relation for the area. The contribution of CO
2 gas exchange and mixing were calculated and from this the biological turnover was deduced to reveal the calculated
CT changes.The net annual uptake of CO
2 in the central Arkona Sea was estimated to be about 1.5 Tg (1.5·10
12 g) which was approximately balanced by a net oxygen release considering the uncertainties of the flux calculations. Near-coast CO
2 emission due to episodic upwelling partly compensated the uptake of the central part of the Arkona Sea reducing the overall magnitude of the CO
2 uptake.
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12.
Deep‐sea hydrothermal vents are unique light‐independent ecosystems that are sustained by chemosynthetic bacteria. For many of the invertebrates inhabiting in such environments, bacteria play essential roles in both energy acquisition and detoxification of potentially toxic gases such as H
2S. In this study, the bacterial flora present on the gills of
Alvinocaris longirostris (Bresiliidae: Caridea), a shrimp inhabiting hydrothermal vents (1532 m depth) at the Hatoma Knoll of the Okinawa Trough, was investigated. Bacterial 16S rDNA fragments were successfully amplified from the gills and 70% of these fragments showed an identical pattern in the restriction fragment length polymorphism analysis. These fragments were assigned to the ribotype AL‐1. Phylogenetic analyses suggest that AL‐1 forms a monophyletic clade with
Sulfurovum spp. (ε‐Proteobacteria). Fluorescence
in situ hybridization for AL‐1 and electron microscopy showed the presence of short‐rod bacteria lining up on the cuticular layer of the surface of the gill filaments. These results suggest that bacterial association with gills also occurs in bresiliid shrimps.
相似文献
13.
The Prévost lagoon (Mediterranean coast, France), was subject to annual dystrophic crises caused by the biodegradation of opportunistic macroalgae (
Ulva lactuca) in the past. These crises result in anoxic waters with subsequent blooms of Purple Sulphur Bacteria (red waters) which, by oxidizing sulphide, contribute to the reestablishment of oxic conditions in the water column. Mechanical dredging of the macroalgal biomass has been carried out in the lagoon since 1991 with the aim of preventing the ecological and economic disturbances caused by such crises. Dredging began just before the phototrophic bloom when the water was already hypoxic (O
2 = 0.7 mg·L
−1) and contained sulphilde (H
2S = 7.3 mg·L
−1) and purple patches of phototrophic bacteria (
Thiocapsa sp.) that were beginning to develop on decaying macroalgae at the sediment surface. The dredging prevented red water formation and drastically modified both phototrophic community structure and activity and biogeochemical sulphur cycling. The dredging permitted the reestablishment of oxic conditions for a short period only (1–13 August). Resuspension of the superficial sediment layers disturbed the phototrophic bacterial community, whose numbers decreased by one order of magnitude (from 2 × 10
6 to 3.9 × 10
5 CFU.mL
−1). The phototrophic community was no longer effective in reoxidizing the reduced sulphur compounds remaining in the sediments, as shown by a drastic sulphate depletion in the superficial sediment layers. Moreover, the increase in the specific bacteriochlorophyll
a concentration of the phototrophic purple bacteria and the rapid development of Green Sulphur Bacteria (
Prosthecochloris-like microorganisms) indicated that the phototrophic community was growing under severe light-limiting conditions due to the resuspension of sediment particles in the water. These conditions did not allow the phototrophic bacterial community to efficiently reoxidize the reduced sulphur compounds originating from the sediments. In consequence, hypoxic conditions (O
2 = 4.7 to 4.8 mg·L
−1) and low sulphide concentrations (H
2S = 0.4 to 0.7 mg·L
−1) were detected in the water column until September. The ecological balance in the lagoon was reestablished only in October, whereas, in previous years it had been restored in August.
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14.
采用常规生物学方法和统计回归分析方法,对浙江近海曼氏无针乌贼的繁殖生物学特性进行了研究,比较了不同时期浙江近海曼氏无针乌贼卵巢成熟系数(GSI)、生物学体型及个体生殖力与生物学指标关系。结果表明,浙江近海曼氏无针乌贼GSI在4月份达到最高(9.51%±7.23%),相比20世纪60年代初、80年代初,自然海域曼氏无针乌贼的性腺发育提前,且生殖期延长。20世纪80年代初曼氏无针乌贼的生物学体型、怀卵量及个体生殖力均大于60年代初和自然海域曼氏无针乌贼,同时曼氏无针乌贼在人工养殖条件下生物学体型、怀卵量及个体生殖力增大。浙江近海曼氏无针乌贼的个体生殖力均随着胴长(ML)、体质量(W)、卵巢质量(WO)、GSI这些指标的增大而增大,除体质量相对生殖力(FW)与ML为密切正相关外,个体生殖力与这些指标的关系均达到了极显著水平(P<0.01)。多元线性逐步回归分析表明,WO是影响浙江近海曼氏无针乌贼个体生殖力的最重要指标。
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15.
Anoxic sulfidic waters provide important media for studying the effect of reducing conditions on the cycling of trace metals. In 1987–1988, dissolved and particulate trace metal (Mn, Fe, Co, Ni, Cu, Zn, Cd and Pb) concentrations were determined in the water column of the anoxic Drammensfjord basins, southeastern Norway. The iminodiacetic acid type chelating resin (Chelex 100) was used for the preconcentration of trace metals. The trace metal concentrations were determined using atomic absorption spectrophotometry (AAS), differential pulse polarography (DPP), and differential pulse-anodic stripping voltammetry (DP-ASV).It was observed that the trace metals Mn and Fe were actively involved in the processes of redox cycling (oxidationreduction and precipitation-dissolution) at the
O2/
H2S interface. The dissolved concentrations of Mn, Fe and Co showed maxima just below the
O2/
H2S interface. The seasonal enhancement in the maxima of both dissolved and particulate Mn and Fe at the redox cline is mainly governed by the downward movement of water which carries oxygen. An association of Co with the Mn cycle was observed, while the total dissolved Ni was decreased by only 10–35% in the anoxic waters. The dissolved concentrations of Cu, Zn, Pb and, to a lesser extent, Cd decreased in the anoxic zone.
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16.
Nitrous oxide (N
2O) is a trace gas that is increasing in the atmosphere. It contributes to the greenhouse effect and influences the global ozone distribution. Recent reports suggest that regions such as the Arabian Sea may be significant sources of atmospheric N
2O.In the ocean, N
2O is formed as a by-product of nitrification and as an intermediary of denitrification. In the latter process, N
2O can be further reduced to N
2. These processes, which operate on different source pools and have different magnitudes of isotopic fractionation, make separate contributions to the
15N and
18O isotopic composition of N
2O. In the case of nitrification in oxic waters, the isotopic composition of N
2O appears to depend mainly on the
15N/
14N ratio of NH
+4 and the
18O/
16O ratio of O
2 and H
2O. In suboxic waters, denitrification causes progressive
15N and
18O enrichment of N
2O as a function of degree of depletion of nitrate and dissolved oxygen. Thus the isotopic signature of N
2O should be a useful tool for studying the sources and sinks for N
2O in the ocean and its impact on the atmosphere.We have made observations of N
2O concentrations and of the dual stable isotopic composition of N
2O in the eastern tropical North Pacific (ETNP) and the Arabian Sea. The stable isotopic composition of N
2O was determined by a new method that required only 80–100 nmol of N
2O per sample analysis. Our observations include determinations across the oxic/suboxic boundaries that occur in the water columns of the ETNP and Arabian Sea. In these suboxic waters, the values of δ
15N and δ
18O increased linearly with one another and with decreasing N
2O concentrations, presumably reflecting the effects of denitrification. Our results suggest that the ocean could be an important source of isotopically enriched N
2O to the atmosphere.
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17.
The distribution of barite in sediments from D.S.D.P. sites 424 and 424A at the Galapagos hydrothermal mounds field is determined and the process of its formation is deduced. Barite in these deposits is associated with calcareous sediments and is completely absent from the hydrothermal material (manganese crusts and nontronite). Its concentrations tend to increase in the deeper sediments. Since manganese crusts contain significant amounts of Ba, a lack of barite in them is probably due to low concentrations of SO
42 in the sediment-seawater interface where they form. The formation of barite occurs within buried sediments, the interstitial waters of which are saturated with SO
42. The most probable source of SO
42− is the oxidation of H
2S which is released from the hydrothermal fluids percolating upwards through the sediments. Although nontronite is formed within buried sediments the environmental conditions occurring during its formation (reducing) prevent barite formation.The association of barite with calcareous sediments is due to the release of Ba by calcareous microorganisms and/or to high concentrations of Ca in the pore waters which maintain a high pH and hence SO
42− is stable.
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18.
采用强电场电离H2O、O2方法,在分子层次上加工成高浓度羟基自由基(OH.)溶液,喷洒在有赤潮生物的海面上,当海水的羟基质量浓度达到0.68 mg/L时,致死洛氏角刺藻(Chaetoceros lorenzianus)等31种赤潮生物效率达到99.89%,致死细菌、弧菌效率达到100%,致死膝沟藻孢囊、多甲藻孢囊效率达到100%;赤潮生物叶绿素a含量低于检测方法低限值;剩余OH.分解成H2O和O2;尸体将分解成CO2、H2O和微量无机盐。从试验数据表明,OH.是治理赤潮有效可行的绿色新方法。实现了治理赤潮以及加工羟基过程的零污染、零废物排放、零残留物。
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19.
The increasing atmospheric CO
2 concentration in the last few decades has resulted in a decrease in oceanic pH. In this study, we assessed the natural variability of pH in coastal waters off Goa, eastern Arabian Sea. pH
T showed large variability (7.6–8.1) with low pH conditions during south-west monsoon (SWM), and the variability is found to be associated with upwelling rather than freshwater runoff. Considering that marine biota inhabiting dynamic coastal waters off Goa are exposed to such wide range of natural fluctuations of pH, an acidification experiment was carried out. We studied the impact of low pH on the local population of sea urchin
Stomopneustes variolaris (Lamarck, 1816). Sea urchins were exposed for 210 days to three treatments of pH
T: 7.96, 7.76 and 7.46. Our results showed that
S. variolaris at pH
T 7.96 and 7.76 were not affected, whereas the ones at pH
T 7.46 showed adverse effects after 120 days and 50% mortality by 210 days. However, even after exposure to low pH for 210 days, 50% organisms survived. Under low pH conditions (pH
T 7.46), the elemental composition of sea urchin spines exhibited deposition of excess Sr
2+ as compared to Mg
2+ ions. We conclude that although the sea urchins would be affected in future high CO
2 waters, at present they are not at risk even during the south-west monsoon when low pH waters reside on the shelf.
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