Species In Seawater Research Articles

Isolation and Characterization of Surface and Subsurface Bacteria in Seawater of Mantanani Island, Kota Belud, Sabah by Direct and Enrichment Techniques

The distribution of hydrocarbon-utilizing bacterial may vary between surface and subsurface of the seawater. One of the identified contributors is the Total Petroleum Hydrocarbon. The isolation and characterization of bacteria using Direct and Enrichment techniques helps in identifying dominant bacterial populations in seawater of Mantanani Island, Kota Belud, Sabah, potential of further investigation as hydrocarbon degrader. Crude oil (5% v/v) was added as the carbon source for bacteria in Enrichment technique. For surface seawater, the highest population of bacteria identified for both Direct and Enrichment technique were 2.60 × 107 CFU/mL and 3.84 × 106 CFU/mL respectively. Meanwhile, for subsurface seawater, the highest population of bacteria identified for both Direct and Enrichment technique were 5.21 × 106 CFU/mL and 8.99 × 107 CFU/mL respectively. Dominant species in surface seawater were characterized as Marinobacter hydrocarbonoclasticus-RMSF-C1 and RMSF-C2 and Alcanivorax borkumensis-RMSF-C3, RMSF-C4 and RMSF-C5. As for subsurface seawater, dominant species were characterized as Pseudomonas luteola-SSBR-W1, Burkholderia cepacia-SSBR-C1, Rhizobium radiobacter- SSBR-C3 and Leuconostoc-cremois -SSBR-C4.

The Impact of Egg Ozonation on Hatching Success, Larval Growth, and Survival of Atlantic Cod, Atlantic Salmon, and Rainbow Trout.

The direct exposure of fish eggs to ozonated water has generated interest as a means of ensuring pathogen-free eggs without the use of harsh chemicals. However, there are numerous knowledge gaps, including safe contact times, exposure levels, and potential long-term effects on aquaculture species in both freshwater and seawater. The effect of different ozone (O3) doses (0.5-1.0, 1.5-2.0, and 2.5-3.0 mg of O3/L for 90 s) on recently fertilized eggs of Atlantic Cod Gadus morhua and eyed eggs of Atlantic Salmon Salmo salar and Rainbow Trout Oncorhynchus mykiss was evaluated in comparison with the effects of two commercial disinfectants: Perosan (0.004 mg/L) and Ovadine (100 mg/L). The impact of ozone application was evaluated based on hatching success, larval nucleic acid concentration, larval growth, and survival. Overall, results indicated that ozonation of Atlantic Cod eggs at a dose less than 3.0 mg/L for 90 s produced no negative effect on the larvae up to 30 d posthatch. Furthermore, ozonation of Atlantic Salmon and Rainbow Trout eggs generated no negative effect on the larvae, based on monitoring until 85% yolk sac re-absorption (16 d posthatch).

새만금지역 내방수제 착공 이후 식물플랑크톤 군집의 분류군

The present study examined the phytoplankton communities of 4 regions, fresh water sites, estuary, Mankyeong and Dongjin lake and offshore regions, 4 times a year from 2011 to 2013. The number of species were 48-59 in 2011 (March, June, September, and November). From Mankyeong and Dongjin lake, fresh water species were dominated in June and coexisted with seawater species in September 2011. 45-65 species were observed in 2012 (April, June, September, and November) and diverse cyanophytes were present at the fresh water sites in September. The number of species reached up to 56-69 in 2013 (March, June, September, and November). In particular, owing to the diverse dinoflagellates from seawater and various cyanophytes and chlorophytes from fresh water, the maximum species number was recorded in June, 2013.

Thiol-functionalized silica microspheres for online preconcentration and determination of mercury species in seawater by high performance liquid chromatography and inductively coupled plasma mass spectrometry

Thiol-functionalized silica microspheres were synthesized from aminosilica for online mercury preconcentration, followed by high performance liquid chromatographic separation and inductively coupled plasma mass spectrometry detection.

Application of chitosan microparticles for reduction of vibrio species in seawater and live oysters (Crassostrea virginica).

Human Vibrio infections associated with consumption of raw shellfish greatly impact the seafood industry. Vibrio cholerae-related disease is occasionally attributed to seafood, but V. vulnificus and V. parahaemolyticus are the primary targets of postharvest processing (PHP) efforts in the United States, as they pose the greatest threat to the industry. Most successful PHP treatments for Vibrio reduction also kill the molluscs and are not suitable for the lucrative half-shell market, while nonlethal practices are generally less effective. Therefore, novel intervention strategies for Vibrio reduction are needed for live oyster products. Chitosan is a bioactive derivative of chitin that is generally recognized as safe as a food additive by the FDA, and chitosan microparticles (CMs) were investigated in the present study as a potential PHP treatment for live oyster applications. Treatment of broth cultures with 0.5% (wt/vol) CMs resulted in growth cessation of V. cholerae, V. vulnificus, and V. parahaemolyticus, reducing culturable levels to nondetectable amounts after 3 h in three independent experiments. Furthermore, a similar treatment in artificial seawater at 4, 25, and 37°C reduced V. vulnificus levels by ca. 7 log CFU/ml after 24 h of exposure, but 48 h of exposure and elevated temperature were required to achieve similar results for V. parahaemolyticus and V. cholerae. Live oysters that either were artificially inoculated or contained natural populations of V. vulnificus and V. parahaemolyticus showed significant and consistent reductions following CM treatment (5%) compared to the amounts in the untreated controls. Thus, the results strongly support the promising potential for the application of CMs as a PHP treatment to reduce Vibrio spp. in intact live oysters.

Leaching test of gamma-emitting Cs, Ru, Zr, and U from neutron-irradiated UO2/ZrO2 solid solutions in non-filtered surface seawater

The leaching behaviors of gamma-ray radionuclides, Cs-137, Ru-103, and Zr-95, produced by neutron irradiation of UO2/ZrO2 solid solutions, in real surface seawater were investigated under atmospheric conditions. The fraction of radionuclide inventory leached in the seawater was in the order of Cs > Ru (∼U) ≫ Zr, indicating that the fraction was significantly affected by the chemical state of the radionuclides. However, the amount of soluble nuclides was proportional to that of uranium regardless of whether the solid solutions were prepared under an oxidative or reductive environment. A tiny fraction of Ru was filtered out by a 3 kDa nominal molecular weight cut-off filter after the 160 d leaching test, suggesting a different behavior from its ionic form, but Cs and U did not form a colloid-like species in seawater.

Adsorption Behavior of Radionuclides Using Novel Tannic Acid-type Resin Embedded in High-porous Silica Beads in Seawater

The adsorption behavior of Cs(I), Sr(II), I(I), and Ln(III) species on the novel synthesized tannic acid-type resin embedded in high-porous silica beads (TA resin) in seawater with initial pH 7.7 has been studied at room temperature, compared with those of typical resins such as bisphenol A-type (BA), DIAION CR10, WK10, and PK228 resins. As a result, it was found that the obtained distribution coefficients (Kd) of these metal ions using the examined resins increase in order of WK10, CR10, BA, and TA resins (≒ PK228 resin) for Cs(I) species, in order of WK10, BA, TA, CR10, and PK228 resins for Sr(II) species while these resins have no adsorption ability of I(I) species. Moreover, it was also revealed that these resins can adsorb stronger trivalent lanthanides from La to Lu except for Pm in order of PK228, WK10, BA, TA, and CR10 resins. These results imply that the adsorption ability of our synthesized TA resin for the metal ions such as Cs(I), Sr(II), and Ln(III) species are much higher than those of commercial resins, that is, we have succeeded in the synthesis of the novel effective resin for removal of Cs(I), Sr(II), and Ln(III) species in seawater. The Kd values of Ln(III) species with TA resin were relatively larger than those of Cs(I) and Sr(II) species. The obtained Kd values of Ln(III) species with TA resin increased sharply with increasing the pH (1.5, 2.8, 6.3, 7.2, 7.4, and 8.1) in seawater due to the dissociation of OH groups in TA resin and decreased gradually with an increase of the dilution factor (1.0, 2.0, 3.0, 5.0, and 10.0) of seawater because the complexation reactions between Ln(III) species and CO32− contained in seawater are depressed. In addition, we have examined the adsorption isotherms and thermodynamics (Temp. = 297 - 330 K) of Ln(III) species on TA adsorbent in seawater. As a result, it was found that the adsorption processes between TA resin and Ln(III) species are strongly influenced by the components contained in seawater. Furthermore, their processes were found to be endothermic and spontaneous reactions in nature. From these results, we concluded that the developed TA resin is suitable for removal of Ln(III) species rather than that of Cs(I) and Sr(II) species in contaminated seawater.

Simultaneous Determination of Inorganic Nitrogen Species in Seawater by Ion Chromatography —Addition Effect of EDTA to Seawater—

イオンクロマトグラフィー（IC）を用いた海水中無機態窒素［亜硝酸イオン（NO2－），硝酸イオン（NO3－），アンモニウムイオン（NH4＋）］の同時定量のために，マスキング剤としてEDTA［エチレンジアミン四酢酸三ナトリウム（EDTA・3Na）あるいはエチレンジアミン四酢酸四ナトリウム（EDTA・4Na）］を海水サンプルに添加する方法を検討した．亜硝酸イオン，硝酸イオンを，分離カラムとしてポリマー系の高イオン交換容量の陰イオン交換カラム，溶離液として1.0 M塩化ナトリウム＋5 mMリン酸緩衝液（pH 5.0）を用いて分離後，測定波長225 nmで検出した．一方，アンモニウムイオンを，ジクロロイソシアヌル酸ナトリウムと1-ナフトールを用いたインドフェノール青法によるポストカラム反応を用いて測定波長710 nmで検出した．EDTA（EDTA・3NaとEDTA・4Na）の添加は，海水中に存在する陽イオン（マグネシウム，カルシウムイオン，ストロンチウムイオン）によるアンモニウムイオン測定の妨害抑制に有効であった．EDTA添加は亜硝酸イオン，硝酸イオン測定を妨害しなかった．実際海水にはEDTA・3Naの添加が有効であり微量無機態窒素3成分の同時測定を可能にした．35‰ 人工海水中での各イオンのピーク面積法による検量線は，0～2 mg L－1の範囲で良好な直線性（R2＝0.995以上）を示した．亜硝酸イオン，硝酸イオン，アンモニウムイオンの検出限界値（S/N＝3）は，それぞれ0.3 μg L－1，1.8 μg L－1，1.9 μg L－1であった．繰り返し精度（各イオン濃度1.0 mg L－1，n＝5）は，0.23％ 以下（保持時間），1.70％ 以下（ピーク面積），1.50％ 以下（ピーク高）であった．本法をEDTA・3Na添加海水の直接導入による無機態窒素の同時定量に適用した．標準添加回収率は98～105％ の範囲内にあった．

Physico-chemical surface properties of microalgae

This study reports a comprehensive set of experimentally measured physico-chemical surface properties of 12 different microalgae including fresh and seawater species of green algae, diatoms and cyanobacteria. The surface free energy and its components including the acid-base (AB), van der Waals (LW), electron donor/acceptor parameters were quantified based on contact angle measurements along with the Lifshitz–van der Waals acid–base approach using the probe liquid surface tension parameters proposed by van Oss et al. as well as by Della Volpe and Siboni. Moreover, the zeta and surface potentials of all species were determined using electrophoretic mobility measurements along with using Smoluchowski's model. Finally, the free energy of cohesion of the microalgae was also determined based on the calculated surface energy properties. The results showed that the electron donor parameter correlated well with the free energy of cohesion in all groups of microalgae. Moreover, species known to form colonies and exhibit benthic cultures had distinctly hydrophobic surfaces compared to microalgae prefering planktonic growth. These results indicate the importance of surface hydrophobicity for causing biofouiling or flocculation of cultures. Finally, the zeta potentials did not show a distinctive trend with the types of microalgae but the surface potentials were markedly larger for the salt water species. The reported methods and data are expected to provide critical information for researchers and technology developers concerned with cell to cell and cell to substrata interactions of microalgae in algal biomass cultivation and harvesting, biofouling of membranes and surfaces, as well as cell-surface interactions in photosynthetic microbial fuel cell technologies.

Haemolytic activity and characterization of nematocyst venom from Pelagia noctiluca (Cnidaria: Scyphozoa)

We investigated the haemolytic capacity of the crude venom extracted from isolated nematocysts of Pelagia noctiluca (Cnidaria: Scyphozoa), and evidenced the proteic fractions responsible for this activity. The nematocyst venom was used at various concentrations to evaluate the haemolytic activity and the lysosomal membrane stability of red blood cells of two teleostean species treated with the extract. The nematocyst extract was assayed against erythrocytes of the two teleostean species living in different environments, Carassius auratus as a common freshwater species, and Liza aurata as a representative of seawater species. Experiments on the haemolytic activity of P. noctiluca in the presence of lipid components of erythrocyte membranes showed that sphyngomyelin strongly inhibited this activity. The crude venom was analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis SDS-PAGE and high performance liquid chromatography (HPLC) to detect the proteic composition, and it was found that the active haemolytic components of this venom are distributed in at least four protein fractions. The results of our experiments indicated that Pelagia noctiluca venom induces haemolysis and lysosomal membrane destabilisation in both species and that Carassius auratus was more susceptible to jellyfish venom than was Liza aurata. No significant differences in glutathione (GSH) levels were observed between control and treatments; consequently the toxins do not cause the oxidative stress but likely recognize specific targets (i.e. sphyngomyelin) in the plasmatic membrane of red blood cells.

Ionised silica in the estuary of a river as supply to seawater: Identification and ionization efficiency of silica species by FAB-MS

Measurement of the dissolution state of silicic acid is difficult. In river water, silica exists in particle form, but silica particles with a diameter of less than approximately 0.45 μm are considered as dissolved silica. In seawater, silica exists in two forms: ionic silica and particle silica. In this study, we focused on ionic silica. Using fast atom bombardment mass spectrometry (FAB-MS), the silica species in river water and seawater were detected as ionic forms. Ionic silica forms various chemical species in aquatic solutions, including the monomer ([Si(OH)3O−]) and dimer ([Si2(OH)5O2−]). The relative abundances of these species in aquatic solutions depend on the chemical and physical conditions. Silica species such as [Si(OH)2O2Na]− ([monomer-Na+]−), [Si2(OH)5O2]− ([dimer]−), [Si2(OH)4O3Na]−([dimer-Na+]−), [Si4(OH)7O5]− ([cyclic tetramer]−), [Si4(OH)6O6Na]− ([cyclic tetramer-Na+]−), [Si4(OH)9O4]− ([linear tetramer]−) and [Si4(OH)8O5Na]− ([linear tetramer-Na+]−) were directly observed by FAB-MS in river water and seawater. Some of these ionic silica species are expected to serve as “nutrients” for diatoms in seawater. Large silica particles are transported in river water, whereas in estuaries, a large amount of silica is precipitated and a small amount of silica is dissolved as ionic forms in sodium chloride solution. In river water, the concentration of silica was high, but the ionic silica species were hardly ionised by FAB-MS. In seawater, the concentration of silica was low, but the ionic silica species were well ionised. Thus, the ionization efficiency of silica species by FAB-MS indicates the type of silica species. The filtration process of silicic acid and the ionization of silicic acid to dissolve the silica species in seawater, which is an electrolyte (sodium chloride), occur in the estuary of a river. Thus, the estuary of a river plays an important role in the restructuring of silica from particle form to ionic form.

Behavior of platinum during estuarine mixing (Pontevedra Ria, NW Iberian Peninsula)

The concentrations of Pt in sediments, water and suspended particulate matter (SPM) were determined in the Lérez River estuary (Pontevedra Ria, NW Iberian Peninsula) on two sampling dates in 2008 and 2011, by means of catalytic adsorptive stripping voltammetry. Average concentrations in sediments (1.2±0.5ngg−1; n=13) corresponded to an enrichment factor of 2–4 compared to background values, and were in the range of those found in the SPM during the 2011 sampling (2.1±2.4ngg−1; n=15), but significantly lower than those in 2008 SPM (8.0±4.4ngg−1; n=15). Higher dissolved Pt concentrations were also found in 2008 (0.21 and 0.62pM in the freshwater and seawater end-member) compared to the 2011 campaign (0.03 — freshwater and 0.40pM — seawater end-member). Concentrations in the seawater end-members exceed those of typical North Atlantic waters, suggesting inputs of this element within the estuary. The extremely low value for the freshwater end-member in 2011 appears to be among the lowest Pt concentrations ever reported in the literature. Non-conservative behavior of Pt during estuarine mixing was observed on both sampling dates. Particle–water distribution coefficients (KD) show a decrease with salinity, in agreement with speciation calculations, which predict a transfer from neutral Pt(II) (as Pt(OH)2) in freshwater to negatively charged Pt(IV) (as PtCl5(OH)2−) species in seawater. Such behavior during estuarine mixing can play an important role in Pt mobilization from contaminated particles discharged into estuaries and coasts.

29Si{1H} CP-MAS NMR comparison and ATR-FTIR spectroscopic analysis of the diatoms Chaetoceros muelleri and Thalassiosira pseudonana grown at different salinities

Diatoms are key indicators of marine environmental health. To further understand how diatoms respond to varying degrees of salinity, either due to climate change or brine waste discharge into marine environments, two different diatom species were studied. Thalassiosira pseudonana and Chaetoceros muelleri were cultured at three different salinities namely, 26 practical salinity units (PSU or parts per thousand), 36 PSU (standard salinity for culturing of seawater species) and 46 PSU. Changes in silica and organic content within the cultured diatoms were analysed using solid-state (29)Si{(1)H} cross-polarization-magic angle spinning (CP-MAS) nuclear magnetic resonance (NMR) and attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopies coupled with analysis of variance. (29)Si CP-MAS NMR showed that qualitatively the Q4:Q3 area ratios of C. muelleri, grown away from standard salinities, increased in response to the formation of more condensed (2 ≡SiOH → ≡Si-O-Si≡ + H2O) and/or an increase in closely associated organic matter to the Q4 component of the diatoms. This was not observed for T. pseudonana. However, both species showed the appearance of a new peak centered at 1575-1580 cm(-1) in the ATR-FTIR spectra, designated as the C═N band of nitrogenous purine-type compounds. Further, the C. muelleri species was shown to produce more extracellular polymeric substances at non-standard salinities. On this basis, results suggest that there is a strong relationship between diatom composition and salinity and that C. muelleri is more sensitive to its environment than T. pseudonana.

Shipboard measurements of gaseous elemental mercury along the coast of Central and Southern California

Gaseous elemental mercury (GEM) in the atmosphere was measured during an oceanographic cruise in coastal waters between San Diego and San Francisco, California during the CalNex 2010 campaign. The goal of the measurements was to quantify GEM in the various environments that the ship encountered, from urban outflow, the Port of Long Beach and associated shipping lanes, coastal waters affected by upwelling, the San Francisco Bay, and the Sacramento ship channel. Mean GEM for the whole cruise was 1.41 ± 0.20 ng m–3, indicating that background concentrations were predominantly observed. The ship's position was most often in waters off the coast of Los Angeles (74% of time with latitude < 34.3°N) and mean GEM for this section was not significantly (P > 0.05) higher than the whole cruise mean. South of 34.3°N, GEM was observed to vary diurnally and as a function of wind direction, displaying significantly higher concentrations at night and in the morning associated with general transport from the land to the sea. GEM and CO concentrations were positively correlated with a slope of 0.0011 ng m–3 ppbv–1 (1.23 × 10–7 mol mol–1) during periods identified as “Los Angeles urban outflow”, which given the inventoried CO emissions for the region, suggests a larger source of GEM than is accounted for by the inventory. The timing of the diel maximum in GEM (9:00 local time) was intermediate between the maxima of CO and NO2 (6:00) and that of NO and SO2 (10:00–12:00), suggesting that a mixture of urban and industrial sources were contributing to GEM. There was no observable postsunrise dip in GEM concentrations due to reaction with atomic chlorine in the polluted coastal atmosphere. On three occasions, significantly higher GEM concentrations were observed while in the Port of Long Beach (~ 7 ng m–3), and analyses of wind directions, ratios of GEM with other copollutants, and the composition of single particles, suggest that these plumes originated from the local waste incinerator in the Port area. A plume encounter from a large cargo ship allowed for the estimation of a mass‐based emission factor for GEM (0.05 ± 0.01 mg kg–1 fuel burned). GEM enhancements observed in the Carquinez Straits, were lower than expected based on the observed NOx/SO2 ratios in the plumes and emissions inventories of the nearest oil refineries. In a region north of Monterey Bay known for upwelling, GEM in the air was positively correlated with dimethyl sulfide (DMS) in seawater and in the air. Using the observed GEM/DMS(g) relationship and the calculated mean DMS ocean‐atmosphere flux for the cruise, an ocean‐atmosphere flux of GEM of 0.017 ± 0.009 µmol m–2 d–1 was estimated. This flux was on the upper end of previously reported GEM ocean‐atmosphere fluxes and should be verified with further measurements of Hg species in seawater and air.

Bringing part of the lab to the field: On-site chromium speciation in seawater by electrodeposition of Cr(III)/Cr(VI) on portable coiled-filament assemblies and measurement in the lab by electrothermal, near-torch vaporization sample introduction and inductively coupled plasma-atomic emission spectrometry

A field-deployable electrochemical approach to preconcentration, matrix clean up and selective electrodeposition of Cr(III) and Cr(III)+Cr(VI) in seawater is described. Using portable, battery-operated electrochemical instrumentation, Cr species in seawater were electrodeposited in the field on portable coiled-filament assemblies made from Re. Assemblies with dried residues of Cr(III) or Cr(III)+Cr(VI) on them were transported to the lab for concentration determination by electrothermal, near-torch vaporization (NTV) sample introduction and inductively coupled plasma-atomic emission spectrometry (ICP-AES).Electrodeposition offers selective species deposition, preconcentration and matrix clean up from seawater samples. For selective deposition, free Cr(VI) was electrodeposited at −0.3V and Cr(III)+Cr(VI) at −1.6V (both vs Ag/AgCl). Interestingly, at 0V (vs Ag/AgCl) and in the absence of an electrodeposition potential only Cr(VI) was spontaneously and selectively adsorbed on the coil and reasons for this are given. Due to preconcentration afforded by electrodeposition, the detection limits obtained after a 60s electrodeposition at the voltages stated above using buffered (pH=4.7) artificial seawater spiked with either Cr(III) or Cr(VI) were 20pg/mL for Cr(III) and 10pg/mL for Cr(VI). For comparison, the detection limit for Cr obtained by pipetting directly on the coil 5μL of diluted standard solution was 500pg/mL, thus it was concluded that electrodeposition offered 40 to 60 fold improvements. Matrix clean up is required due to the high salt content of seawater and this was addressed by simply rinsing the coil with 18.2MΩ water without any loss of Cr species. Reasons for this are provided. The method was validated in the lab using buffered artificial seawater and it was used in the field for the first time by sampling seawater, buffering it and immediately electrodepositing Cr species on portable assemblies on-site.Electrodeposition in the field addressed species transformation during sample pre-treatment. Such transformations occur due to sample acidification and may take place during transport and possibly storage prior to analysis. Thus, electrodeposition in the field is more reflective of Cr species concentration at the environmental conditions (e.g., temperature) at the time of sampling. It also opens up the possibility for shipping to the lab portable assemblies with Cr species on them rather than shipping large volumes of sample to the lab, thus also reducing shipping, handling and storage costs.

Validation of a method for the determination of tributyltin in seawater by stir bar sorptive extraction–liquid chromatography tandem mass spectrometry

The main objective of this work is to develop an accurate, sensitive, simple and cost-effective method for the determination of tributyltin species (as cationic form) in seawater at ultra-trace levels. The method is based on the use of stir bar sorptive extraction (SBSE) followed by solvent desorption and liquid chromatography tandem mass spectrometry (SD–LC–MS/MS (QqQ)) analysis, operating in positive electrospray ionisation (ESI) and in the selected reaction monitoring (SRM) mode. Extraction and LC–MS/MS parameters were accurately optimised to achieve the highest recoveries and to enhance the analytical characteristics of the method. The different parameters that affect the extraction procedure, the chromatographic and spectrometric conditions, and the surrogate selection were evaluated. In contrast with previously proposed methods, the proposed method involves a simplified sample treatment. Quality parameters such as linearity, accuracy in terms of trueness and precision, uncertainty and specificity were examined with good results. The evaluation of two surrogates (tri-n-propyltin chloride and tripentyltin chloride) was also carried out. The limit of detection (LOD) and limit of quantification (LOQ) obtained were 0.8 and 2.5ngL−1, respectively. Precision, expressed as relative standard deviation (%RSD), was lower than 16%, and the determination coefficient (R2) was higher than 0.990 with a residual deviation for each calibration point lower than ±25%. Mean recoveries were between 92% and 102%. The accuracy of the method was also studied by participating in an external proficiency testing scheme. After validation, the method was applied to the analysis of all tributyltin species found in natural seawater samples. The method meets the requirements of the United States Environmental Protection Agency (US-EPA).

Low colloidal associations of aluminium and titanium in surface waters of the tropical Atlantic

The distribution of dissolved, soluble and colloidal fractions of Al and Ti was assessed by ultrafiltration studies in the upper water column of the eastern tropical North Atlantic. The dissolved fractions of both metals were found to be dominated by the soluble phase smaller than 10kDa. The colloidal associations were very low (0.2–3.4%) for Al and not detectable for Ti. These findings are in some contrast to previous estimations for Ti and to the predominant occurrence of both metals as hydrolyzed species in seawater. However, low tendencies to form inorganic colloids can be expected, as in seawater dissolved Al and dissolved Ti are present within their inorganic solubility levels. In addition, association with functional organic groups in the colloidal phase is unlikely for both metals. Vertical distributions of the dissolved fractions showed surface maxima with up to 43nM of Al and 157pM of Ti, reflecting their predominant supply from atmospheric sources to the open ocean. In the surface waters, excess dissolved Al over dissolved Ti was present compared to the crustal source, indicating higher solubility and thus elevated inputs of dissolved Al from atmospheric mineral particles. At most stations, subsurface minima of Al and Ti were observed and can be ascribed to scavenging processes and/or biological uptake. The dissolved Al concentrations decreased by 80–90% from the surface maximum to the subsurface minimum. Estimated residence times in the upper 100m of the water column ranged between 1.6 and 4years for dissolved Al and between 14 and 17years for dissolved Ti. The short residence times are in some contrast to the low colloidal associations of Al and Ti and the assumed role of colloids as intermediates in scavenging processes. This suggests that either the removal of both metals occurs predominantly via direct transfer of the hydrolyzed species into the particulate fraction or that the colloidal phase is rapidly turned over in the upper water column.

Mercury biogeochemical cycling in the ocean and policy implications

Anthropogenic activities have enriched mercury in the biosphere by at least a factor of three, leading to increases in total mercury (Hg) in the surface ocean. However, the impacts on ocean fish and associated trends in human exposure as a result of such changes are less clear. Here we review our understanding of global mass budgets for both inorganic and methylated Hg species in ocean seawater. We consider external inputs from atmospheric deposition and rivers as well as internal production of monomethylmercury (CH3Hg) and dimethylmercury ((CH3)2Hg). Impacts of large-scale ocean circulation and vertical transport processes on Hg distribution throughout the water column and how this influences bioaccumulation into ocean food chains are also discussed. Our analysis suggests that while atmospheric deposition is the main source of inorganic Hg to open ocean systems, most of the CH3Hg accumulating in ocean fish is derived from in situ production within the upper waters (<1000m). An analysis of the available data suggests that concentrations in the various ocean basins are changing at different rates due to differences in atmospheric loading and that the deeper waters of the oceans are responding slowly to changes in atmospheric Hg inputs. Most biological exposures occur in the upper ocean and therefore should respond over years to decades to changes in atmospheric mercury inputs achieved by regulatory control strategies. Migratory pelagic fish such as tuna and swordfish are an important component of CH3Hg exposure for many human populations and therefore any reduction in anthropogenic releases of Hg and associated deposition to the ocean will result in a decline in human exposure and risk.

What regulates rhenium deposition in euxinic basins?

Rhenium is greatly enriched in black shales and euxinic basin sediments relative to its crustal abundance. The enrichment process is generally assumed to involve reduction of ReO4−, the principal Re species in seawater, to an insoluble ReIV oxide or sulfide in suboxic and anoxic environments. The specific biotic or abiotic mechanism of reduction has so far defeated efforts to discover it. Here, an alternative mechanism of fixing Re in sediments is examined experimentally: thiolation of ReO4− leading to particle-reactive thioperrhenates (ReVIIOnS4−n−) or to ReVII sulfide precipitates or coprecipitates. Using optical absorption methodology, we obtain the first measurements of equilibrium constants for formation of ReO3S− and ReS4− as well as a solubility constant for a colloidal Re2S7 polymer. From these constants, we conclude that most euxinic environments contain insufficient sulfide to stabilize thioperrhenates as major species. Similarly, Re2S7 polymers are too soluble to form in near-neutral pH waters, although they might form in acidic mine waters or during supergene–hypogene enrichment processes. To explain remarkable similarities between Mo and Re vertical profiles in the Black Sea, we propose that both elements become thiolated at surfaces of a Fe–Mo–S colloidal phase and consequently coprecipitate. Coprecipitation implies that the triggering mechanism for Re removal from euxinic basins is neither reduction nor thiolation of ReO4−, but instead saturation of sulfidic waters with the Fe–Mo–S phase. Coprecipitation favors removal of Mo more than Re from the aqueous phase, explaining increasing aqueous phase Re/Mo ratios as these elements are depleted from sulfidic waters. The Raleigh fractionation law describes the process well. Similar partition coefficients describe the evolution of Re/Mo ratios quantitatively both in sulfidic Black Sea waters and in sulfidic Hingham Bay pore waters.

An intercomparison of procedures for the determination of total mercury in seawater and recommendations regarding mercury speciation during GEOTRACES cruises

We conducted a laboratory intercomparison of total mercury (Hg) determination in seawater collected during U.S. GEOTRACES Intercalibration cruises in 2008 and 2009 to the NW Atlantic and NE Pacific Oceans. Results indicated substantial disagreement between the participating laboratories, which appeared to be affected most strongly by bottle cleanliness and preservation procedures. In addition, we examined the effectiveness of various collection and sample preparation procedures that may be used on future GEOTRACES cruises. The type of sampling system and filtration medium appeared to make little difference to results. Finally, and in light of results from experiments that considered sample bottle material effect and the development of new methods for CH3Hg+ extraction from seawater, we propose a recommended procedure for determining all four of the major Hg species in seawater (elemental, dimethyl‐, monomethyl‐, and total Hg).