Small Volumes Of Seawater Research Articles

Environmental DNA sampling protocols for the surveillance of marine non-indigenous species in Irish coastal waters

Understanding the spread and distribution of Non-Indigenous Species (NIS) is key when implementing legislation to maintain good ecosystem health. Environmental DNA (eDNA) has shown great potential to detect aquatic organisms in a rapid and cost-effective way, however their applicability to new environments must be validated prior to their implementation. Here, we tested different field sampling methods in combination with eDNA metabarcoding to develop a tool to detect NIS. Large and small volumes of seawater were filtered, in addition to the collection of sediment and horizontal tow net samples at 12 locations across four distinct geographic areas in Ireland. The biggest dissimilarity in the species recovered was found between sediment and town net samples. Tow nets showed to be the most efficient. A total of 357 taxa were identified, including 16 NIS. Fine mesh tow nets were identified as the most cost-efficient for large-scale monitoring and surveillance of NIS.

On the Quality Control for the Determination of Ultratrace-Level 236U and 233U in Environmental Samples by Accelerator Mass Spectrometry.

Our recent attempt to determine ultratrace-level 236U and 233U in small-volume seawater samples was challenged by high and unstable procedure blanks in our environmental radioactivity laboratory, which used to be a spent fuel research facility. Through intercomparison experiments with different laboratories and background checks on the chemical reagents and laboratory dust, the resuspended U-bearing dust was identified as the dominating source of the 236U and 233U contamination. With the implementation of background control (especially dust control) measures, the procedure blanks and detection limits of 236U and 233U for the radiochemical separation procedure have been significantly improved by three orders of magnitudes. With well-controlled blanks, the analytical precision for 236U and 233U predominantly relies on the AMS counting statistics. Background check and dust control are strongly recommended before the analyses of environmental-level long-lived radionuclides (such as 236U and 233U) that are conducted in the former or active nuclear facilities, even if clearance of radioactivity relevant for radioprotection was achieved.

Development and evaluation of a method for concentration and detection of salmonid alphavirus from seawater

Waterborne viral infections represent a major threat to fish health. For many viruses, understanding the interplay between pathogens, host and environment presents a major hurdle for transmission. Salmonid alphavirus (SAV) can infect and cause pancreas disease (PD) in farmed salmonids in seawater. During infection, SAV is excreted from infected fish to the seawater. We evaluated two types of filters and four different eluents, for concentration of SAV3. One L of seawater was spiked with SAV3, followed by filtration and virus elution from membrane filters. For the negatively charged MF hydrophilic membrane filter (MF-) combined with NucliSENS® lysis buffer the SAV3 recovery was 39.5 ± 1.8 % by RT-ddPCR and 25.9 ± 5.7 % by RT-qPCR. The recovery using the positively charged 1 MDS Zeta Plus® Virosorb® membrane filter (MD+), combined with NucliSENS® lysis buffer was 19.0 ± 0.1 % by RT-ddPCR and 13.3 ± 3.8 % by RT-qPCR. The limits of quantification (LOQ) and detection (LOD) were estimated to be 5.18 × 103 and 2.0 × 102 SAV3 copies/L of natural seawater, by RT-ddPCR. SAV3 recovery from small volumes of seawater, and the requirement for standard laboratory equipment, suggest the MF-filter combined with NucliSENS® lysis buffer would be a candidate for further validation in experimental trials.

Determination of Ultratrace Level 135Cs and 135Cs/137Cs Ratio in Small Volume Seawater by Chemical Separation and Thermal Ionization Mass Spectrometry.

The atomic ratio of 135Cs/137Cs is a powerful fingerprint for distinguishing the source terms of radioactive contamination and tracing the circulation of water masses in the ocean. However, the determination of the 135Cs/137Cs ratio is very difficult due to the ultratrace level of 135Cs (<0.02 mBq/m3) and 137Cs (<2 Bq/m3) in the ordinary seawater samples. In this work, a sensitive method was developed for determination of 135Cs concentration and 135Cs/137Cs ratio in seawater using chemical separation combined with thermal ionization mass spectrometry (TIMS) measurement. Cesium was first preconcentrated from seawater using ammonium molybdophosphate-polyacrylonitrile column chromatography and then purified using cation exchange chromatography to remove the interferences. With this method, decontamination factors of 6.0 × 106 for barium and 1800 for rubidium and a chemical yield of more than 60% for cesium were achieved. By using glucose as an activator, the ionization efficiency of cesium was significantly improved to 50.6%, and a constant high current of Cs+ (20 V) can be maintained for more than 180 min, which ensures sensitive and reliable measurement of low level 135Cs and 137Cs. Detection limits of 4.0 × 10-17 g/L for both 135Cs and 137Cs for 200 mL seawater were achieved, which enables the accurate determination of 135Cs concentration and 135Cs/137Cs ratio in a small volume of seawater samples (<200 mL). The developed method has been validated by analysis of seawater reference material IAEA-443. Seawater samples collected from the Greenland Sea, Baltic Sea, and Danish Straits have been successfully analyzed for 135Cs concentrations and 135Cs/137Cs ratios, and the results showed that 135Cs concentrations in the seawater of the Baltic Sea is much higher than that in the Greenland Sea, which is attributed to the high deposition of Chernobyl accident derived radiocesium in the Baltic Sea region.

Diel, daily, and spatial variation of coral reef seawater microbial communities.

Reef organisms influence microorganisms within the surrounding seawater, yet the spatial and temporal dynamics of seawater microbial communities located in proximity to corals are rarely investigated. To better understand reef seawater microbial community dynamics over time and space, we collected small-volume seawater samples during the day and night over a 72 hour period from three locations that differed in spatial distance from 5 Porites astreoides coral colonies on a shallow reef in St. John, U.S. Virgin Islands: near-coral (sampled 5 cm horizontally from each colony), reef-depth (sampled 2 m above each colony) and surface seawater (sampled 1 m from the seawater surface). At all time points and locations, we quantified abundances of microbial cells, sequenced small subunit rRNA genes of bacterial and archaeal communities, and measured inorganic nutrient concentrations. Prochlorococcus and Synechococcus cells were consistently elevated at night compared to day and these abundances changed over time, corresponding with temperature, nitrite, and silicate concentrations. During the day, bacterial and archaeal alpha diversity was significantly higher in reef-depth and near-coral seawater compared to the surface seawater, signifying that the reef influences the diversity of the seawater microorganisms. At night, alpha diversity decreased across all samples, suggesting that photosynthesis may favor a more taxonomically diverse community. While Prochlorococcus exhibited consistent temporal rhythmicity, additional taxa were enriched in reef seawater at night compared to day or in reef-depth compared to surface seawater based on their normalized sequence counts. There were some significant differences in nutrient concentrations and cell abundances between reef-depth and near-coral seawater but no clear trends. This study demonstrates that temporal variation supersedes small-scale spatial variation in proximity to corals in reef seawater microbial communities. As coral reefs continue to change in benthic composition worldwide, monitoring microbial composition in response to temporal changes and environmental fluctuations will help discern normal variability from longer lasting changes attributed to anthropogenic stressors and global climate change.

Experimental observations of marine iodide oxidation using a novel sparge-interface MC-ICP-MS technique

Iodine speciation is used as a redox indicator and water mass tracer. However, the kinetics and mechanisms of oxidation of the reduced iodine species, iodide (I−), in seawater remain largely unresolved. Here, we provide constraints on I− oxidation rates from seawater incubation experiments using a sensitive radiotracer–incubation approach with high-precision mass spectrometry. Samples are inoculated with iodine-129 as I−, incubated under controlled conditions, then oxidized and reduced iodine species are isolated using liquid chromatographic separation. Samples are subsequently aspirated using a novel sparging interface, and the 129I/127I ratio of both iodine species is determined via multi-collector inductively-coupled plasma mass spectrometry. This highly-sensitive analytical approach is optimized for estimating the predicted slow rates of iodine redox transformations in small volume seawater samples at marine-relevant total iodine concentrations. Application of this method to coastal samples from Martha's Vineyard Sound, USA, evidences the heretofore-elusive oxidation of I− under marine-analogue conditions. Our results demonstrate an increase in the 129I/127I of aqueous oxidized iodine species in unamended seawater, most likely due to formation of hypoiodous acid and then dissolved organic iodine, at rates of 118–189 nM/ yr. These rates are comparable to those inferred from previous open ocean mass balance approaches but have the benefit of directly linking iodine speciation changes to in situ I− oxidation. Though our treatment experiments do not definitively isolate the oxidation mechanism, they provide preliminary insight into important roles for both abiotic and biotic factors as well as iodine transformations between dissolved, particulate, and gaseous forms. Ultimately, the derived rates and novel experimental technique have potential to improve marine iodine cycling models and provide constraints on the importance of in situ processes in setting patterns of iodine speciation.

Simple and fast method for the analysis of 236U, 237Np, 239Pu and 240Pu from seawater samples by Accelerator Mass Spectrometry

A simple and fast radiochemical procedure for the sequential extraction of U, Np and Pu from small-volume seawater samples (<10 L) is presented. The method has been developed and optimized for the final determination of 236U, 237Np, 239Pu and 240Pu by Accelerator Mass Spectrometry (AMS). It is based on the use of 242Pu as tracer for both Np and Pu isotopes. Samples are pre-concentrated by Fe(OH)2 co-precipitation. TEVA® and UTEVA® resins are used in a very simplified way for the final purification of the Pu+Np and U fractions, respectively. The radiochemical yields of the three elements have been investigated in detail by alpha spectrometry (AS) and gamma spectrometry (GS). The obtained results indicate high and robust chemical yields for the three elements and similar ones for Pu and Np. Furthermore, the use of 242Pu as tracer for 237Np is validated by analyzing a reference seawater sample (IAEA-443) by radiometric techniques. We demonstrated that, if chemicals are properly chosen, processed blank levels can be kept at the same level of the extremely low detection limits that can be achieved by AMS (105–106 atoms/sample). The procedure is finally applied for the study by AMS of a reference seawater sample from the Mediterranean Sea (IAEA-418).

Rapid and precise analysis of rare earth elements in small volumes of seawater - Method and intercomparison

Rare earth elements (REEs) are used as tracers for oceanic trace element cycling. However, the low (picomolar level) dissolved REE concentrations and time-consuming methods have so far hindered their extensive use in marine studies. This study reports the first application of the automated seaFAST-pico system (Elemental Scientific Inc.) in offline mode and using multi-element isotope dilution inductively coupled plasma-mass spectrometry (ID ICP-MS) for the robust and rapid pre-concentration, purification, and analysis of dissolved REEs from small volumes of seawater (11–12mL). Accuracy of our new method is checked with replicates of GEOTRACES intercalibration seawater from BATS (Bermuda Atlantic Time Series, North Atlantic) at 15m and 2000m water depths. Our results show excellent agreement (within the analytical uncertainty, 2σ SD) with the published intercalibrated values from the GEOTRACES intercalibration study. Replicates of GEOTRACES intercalibration seawater from SAFe at 3000m water depth (Sampling and Analysis of Iron, North Pacific) indicate a procedural long-term error of ≤3.9% 2σ RSD for all REEs, except for Ce and Gd. An international intercomparison from 4 labs using SAFe 3000m seawater aliquots, 2 of which also use the seaFAST-pico system in offline mode, and different pre-concentration, purification, and analytical methods shows excellent agreement between REE concentrations within 7% (2σ RSD) (except for Ce 71%, Gd 14%, Lu 12%). This is comparable to the agreement obtained for the BATS 15m and 2000m samples by six different labs for the international GEOTRACES intercalibration study (van de Flierdt et al., 2012). The REE intercomparison values of SAFe 3000m (i.e., the average of the values from the 4 labs) in this study agree within the analytical uncertainties (2σ SD) with published REE values of deep seawater from nearby stations. Our international intercomparison provides the first REE intercomparison values for the GEOTRACES intercalibration station SAFe at 3000m, and establishes the first reference seawater REE values for quality control of future REE studies in the Pacific Ocean as SAFe will remain a GEOTRACES baseline, and hence intercalibration station, for cruises in the North Pacific. Our method is easy to adopt and enables the extensive use of REEs, thereby opening the way to build a global seawater REE data set.

An environmentally friendly method for the determination of triazine herbicides in estuarine seawater samples by dispersive liquid-liquid microextraction.

A fast, simple, sensitive and green chemistry method using dispersive liquid-liquid microextraction (DLLME) for the simultaneous determination of seven triazine herbicides (ametryn, atrazine, cyanazine, propazine, simazine, simetryn and terbuthylazine) in estuarine seawater samples has been developed. DLLME was carried out using a small volume of seawater (25 mL) and 300 μL of 1-octanol. Herbicide concentrations were determined by liquid chromatography-diode array detection, and results were confirmed by liquid chromatography-electrospray ionisation tandem spectrometry analysis. The analytical features of the proposed method were satisfactory with repeatability < ±5% and intermediate precision < ±10%, and recoveries ranged from 81-102% for all compounds. All the triazines exhibited linear matrix calibration curves with coefficients of determination >0.999 for all the analytes except for simazine (0.9975). Limits of quantification ranged between 0.19 and 1.12 μg L(-1). The method was applied to the analysis of seawater samples from ten points susceptible to contamination by triazines from estuary of A Coruña (Galicia, NW of Spain). The levels of the seven triazines were below the LODs in the analysed samples. Use of proposed method will allow for monitoring of triazines at levels below the regulatory limits set by the European Directive 2008/105/EC of 2 and 4 μg L(-1) for atrazine and simazine, respectively.

Ultra-trace plutonium determination in small volume seawater by sector field inductively coupled plasma mass spectrometry with application to Fukushima seawater samples

Long-term monitoring of Pu isotopes in seawater is required for assessing Pu contamination in the marine environment from the Fukushima Dai-ichi Nuclear Power Plant accident. In this study, we established an accurate and precise analytical method based on anion-exchange chromatography and SF-ICP-MS. This method was able to determine Pu isotopes in seawater samples with small volumes (20–60L). The U decontamination factor was 3×107–1×108, which provided sufficient removal of interfering U from the seawater samples. The estimated limits of detection for 239Pu and 240Pu were 0.11fgmL−1 and 0.08fgmL−1, respectively, which corresponded to 0.01mBqm−3 for 239Pu and 0.03mBqm−3 for 240Pu when a 20L volume of seawater was measured. We achieved good precision (2.9%) and accuracy (0.8%) for measurement of the 240Pu/239Pu atom ratio in the standard Pu solution with a 239Pu concentration of 11fgmL−1 and 240Pu concentration of 2.7fgmL−1. Seawater reference materials were used for the method validation and both the 239+240Pu activities and 240Pu/239Pu atom ratios agreed well with the expected values. Surface and bottom seawater samples collected off Fukushima in the western North Pacific since March 2011 were analyzed. Our results suggested that there was no significant variation of the Pu distribution in seawater in the investigated areas compared to the distribution before the accident.

Disk mini-adsorbers with radial flow for determination of 234Th concentration in seawater

A modified method has been developed for measuring the 234Th concentration in seawater, which is based upon the use of MnO2-impregnated disk mini adsorbers with radial flow connected in-line and the direct beta counting of 234Th and/or its daughter 234mPa. This allows determining the 234Th concentration in a relatively small volume of seawater (20–50 L) with the possibility to check the extraction efficiency in every individual sample. The field testing, which was carried out at different areas of Sevastopol Bay during different seasons, has shown applicability of the proposed method to evaluate particle fluxes in marine environments within a wide range of concentrations of suspended matter.

Determination of low 137Cs concentration in seawater using ammonium 12-molybdophosphate adsorption and chemical separation method

A new method has been developed for analyzing 137Cs in a small volume of seawater. Ammonium 12-molybdophosphate (AMP) was used two times during pretreatment procedure. The first step was to adsorb 137Cs in seawater samples into AMP in order to reduce sample volume, and the second was to remove 87Rb, interference nuclide for β counting. The AMP adsorbing 137Cs was dissolved by sodium hydroxide solution, and then 137Cs was finally formed to be cesium chloroplatinate precipitate by adding 10% hexachloroplatinic acid. The beta rays emitted from 137Cs were measured with a low background gas-proportional α/β counter. This method was applied to several seawater samples taken in the East Sea of Korea. Compared to the routinely used γ-spectrometry method, this new AMP method was reliable and suitable for analyzing 137Cs in deep seawater.

Improvement of 137Cs analysis in small volume seawater samples using the Ogoya underground facility

137Cs in seawater is one of the most powerful tracers of water motion. Large volumes of samples have been required for determination of 137Cs in seawater. This paper describes improvement of separation and purification processes of 137Cs in seawater, which includes purification of 137Cs using hexachloroplatinic acid in addition to ammonium phosphomolybdate (AMP) precipitation. As a result, we succeeded the 137Cs determination in seawater with a smaller sample volume of 10 liter by using ultra-low background gamma-spectrometry in the Ogoya underground facility. 137Cs detection limit was about 0.1 mBq (counting time: 106 s). This method is applied to determine 137Cs in small samples of the South Pacific deep waters.

A single vs. double spike approach to improve the accuracy of 234Th measurements in small-volume seawater samples

234Th is a particle-reactive radionuclide widely used to trace biogeochemical oceanic processes occurring over short timescales. During the last few years, small-volume techniques based on the co-precipitation of 234Th with MnO 2 coupled with beta-counting have been developed as an alternative to large volume gamma-spectrometric techniques. Here a procedure has been developed to enhance quantitative measurement of 234Th in MnO 2 precipitates. The main objectives were to obtain a purified Th fraction for beta-counting and to determine the chemical recovery of 234Th using Th spikes and alpha-spectrometry as an alternative to ICP-MS based methods. Two variations of the procedure are presented. In the first “1 spike” method a 230Th tracer is added to the sample prior to precipitation of MnO 2, and UTEVA® extraction chromatography is used to obtain a NdF 3(Th) purified source that can be used for both beta-counting of 234Th and alpha-spectrometry of 230Th. In the “2 spike” method a 230Th spike is added and the MnO 2(Th) precipitate is directly beta-counted for 234Th and subsequently spiked with 228Th or 229Th prior to UTEVA® purification and alpha-spectrometry. The results confirm the need to process small-volume seawater samples for 234Th measurement in presence of a yield tracer, and show that both the 1 spike and 2 spike methods allow an accurate and precise determination of 234Th (relative percent difference, RPD, between expected and mean measured value < 1%; CV between replicate samples < 3%). Our work also suggests that, although the combined analytical uncertainty on total 234Th measurements accomplished with both versions of the NdF 3 procedure is promising (∼6% for 2-L samples), the precision of the 234Th flux estimation will ultimately depend on the degree of disequilibrium between 234Th and 238U.

Quantification of 234Th recovery in small volume sea water samples by inductively coupled plasma-mass spectrometry

Quantification of 234Th recovery in small volume sea water samples by inductively coupled plasma-mass spectrometry

Preparation of Graphite Targets from Small Marine Samples for AMS Radiocarbon Measurements

A vacuum sample processing line was set up and methods were developed for the determination of radiocarbon in small-volume seawater and biota samples. Seawater samples (500 mL per borosilicate glass bottle and poisoned with HgCl2) were acidified with 5 mL concentrated hydrochloric acid. Pure N2 was used as a carrier gas to strip CO2 from the samples for 10 min in a circulation mode. After purification through several water traps, the CO2 was isolated cryogenically. Using Na2CO3 standard solutions, recovery yields were calculated superior to 95 ± 5%. Freeze-dried marine biota samples were thoroughly mixed with Cu(II)O and combusted at 900°. The CO2 was purified by passing through Ag wool and Cu granules at 450° before reduction to graphite. Finally, graphite was synthesized using Zn dust heated to 450° in the presence of an Fe catalyst at 550°. Although this method takes about 8 hr (synthesis done overnight), the advantage is that no water vapor by-product is formed to hinder the reaction. The graphite yields, measured both by gravimetric methods and by pressure readings, were 95 ± 5%. Accelerator mass spectrometry (AMS) measurements were carried out at the NSF-Arizona AMS Facility. Results for water samples from the northwest Pacific Ocean are reported which are in agreement with data reported elsewhere.

Complete separation of rare earth elements from small volume seawater samples by automated ion chromatography: method development and application to benthic flux

A new Ion Chromatography–Inductively Coupled Plasma Mass Spectrometry (IC–ICP-MS) method is presented for measuring individual rare earth elements (REEs) in small volume (5 ml) seawater samples, with the goal of measuring pore water REEs. The method is shown to be accurate and reproducible for small volumes of a seawater reference standard within the determined precisions. The method has reasonable yield (75%), and, more importantly, is shown to not internally fractionate individual REEs. After describing the method, data from bottom, overlying and interfacial pore waters from four sites (three California margin, one Chile margin) are presented. These data show that there is a REE flux from sediments into bottom water. This flux ranges from 10 −11 to 10 −8 mol cm −2 ky −1 at these sites and is, therefore, on the same order as riverine input to the oceans. Benthic chamber samples support these flux estimates. When pore water and benthic chamber water are normalized to PAAS, the REE patterns can be characterized using three descriptors: the magnitude of the Ce anomaly (always negative), a “MREE bulge” and “HREE enrichment.” However, when normalized to bottom water, LREE>HREE and there is a significant positive Ce anomaly. These features generally support current understanding: that the REEs in the ocean are strongly influenced by organically driven processes. A key proviso is that the fluctuations in the Ce anomaly should be considered to be the net result of changes in dissolved La and Pr, and not mainly a function of Ce oxidation.

Low Blank Preconcentration Technique for the Determination of Lead, Copper, and Cadmium in Small-Volume Seawater Samples by Isotope Dilution ICPMS

A simple low-blank method is described for the analysis of Pb, Cu, and Cd in seawater using Mg(OH)(2) coprecipitation and isotope dilution inductively coupled plasma mass spectrometry (ICPMS). Here, 20-40 μL of 9 M aqueous NH(3) is mixed into a 1.3 mL seawater sample spiked with enriched isotopes of Pb, Cu, and Cd. After centrifugation, the supernatant is discarded and the Mg(OH)(2) precipitate dissolved in 100 μL of 5% HNO(3) for ICPMS analysis. This method is simple, accurate, and precise, with detection limits of Pb = 1.3 pM, Cu = 39 pM, and Cd = 5.0 pM and blanks of Pb = 0.62 pM, Cu = 27 pM, and Cd = 6.0 pM. The method is demonstrated by oceanographically consistent profiles of these trace metals at an ocean station in the eastern North Atlantic.

Determination of trimethylamine oxide in seawater and small volumes of seafood tissue extract using flow injection analysis

A method is described for the indirect determination of trimethylamine oxide (TMAO) in small volumes of seawater (300 μl) and in seafood tissue extracts (100 μl). After simple TMAO reduction to trimethylamine (TMA), the samples were directly injected into the flow injection system enabling the TMAO to be measured as TMA. Calibration of the method with acidic TMAO standard solutions in the range of 10–200 μmol l −1 ( n = 10) and with seawater TMAO standard solutions in the range of 10–100 μmol l −1 ( n = 8) gave linear calibration curves ( r = 0.999 in each case). The minimum detectable level for the method was 6 μmol l −1 while using the acidic standard solutions and 2.5 μmol l −1 for seawater TMAO standard solutions. Relative standard deviations were found to be <2% in all instances.

A technique for the measurement of total ammonia in small volumes of seawater and haemolymph

Abstract A rapid and precise technique combining flow-injection analysis and gas-diffusion is described for the measurement of total ammonia (NH3 + NH4 +) in small volumes (100–450 μl) of seawater and diluted haemolymph. Calibration of the method with seawater ammonia standard solutions in the range 1.0–50.0 μmol ammonia l-1 (n=8), and with saline ammonia standard solutions in the range 5.0–50.0 μmol ammonia l-1 (n=6)gave linear calibration curves (r=O.999 in each case) with precision in the range 0.2–3.0%. Precision of measurement of ammoniain samples of seawater and diluted haemolymph was 0.9–3.3% (n=11–13). The lower limit of detection is 0.20 μmol ammonia l-1. Thirty determinations can be made per hour.