Volume Of Seawater Research Articles

Single pass saltwater disinfection using low voltage electrolysis: Potential implications for aquaculture systems

Open net pen saltwater aquaculture faces criticism due to the potential transmission of pathogens between fish farms and to wild stocks. To address this issue and improve the sustainability and growth of net pen farming, closed containment farms have been suggested, but the cost and feasibility of disinfecting large volumes of water in these types of farms is problematic. We explored the potential for using electrolysis to disinfect saltwater in a flow-through system with water flow velocities between 47 and 105 cm/s. This was the first step to investigating whether this technology could be applied to saltwater flow-through closed containment systems. Various voltage levels (3.3–9.0 V) were applied to generate chlorine from saltwater. We found the disinfection properties of the system varied with wattage (i.e., voltage × ampere), velocity of water flow over the electrodes, salinity of water, and residual chlorine contact time. Wattage was highly correlated with the production of chlorine, and this relationship was dependent on water flow (p = 0.0398). A slower flow velocity led to higher chlorine concentration, and the effect was more pronounced at higher wattages. Using a zero-inflated negative binomial regression model, we found the probability of full disinfection was increased by increasing wattage (p < 0.001) and the residual chlorine contact time (p < 0.001). The level of disinfection (count model) suggested the number of bacteria in the treated samples was determined by the interaction between wattage and flow (p = 0.0056) and the interaction between wattage and salinity (p < 0.001). The bacterial count was also associated with residual chlorine contact time (p < 0.001). The results of this study, although preliminary and limited in their scale, offering a potential solution for disinfecting large volumes of seawater, which could make closed containment fish farming in the ocean viable for reducing bacterial transmission within a farm and to wild fish stocks.

Vulnerability indicators of seawater intrusion in offshore aquifers

This study represents the first attempt to define vulnerability indicators for offshore fresh groundwater, extending prior analyses of the key threats to onshore coastal aquifers. The method applies an existing steady-state sharp-interface coastal aquifer model with semi-confined offshore extension to characterise the sensitivities of the tip and toe locations (top and bottom of the freshwater–seawater interface, respectively) and the freshwater and seawater volumes to environmental changes that threaten offshore freshwater resources. Sensitivity analysis applied to seven case studies quantifies their vulnerability to seawater intrusion from sea level rise, recharge change and a regional change in the onshore groundwater heads. The analysis demonstrates that the tip-to-toe distance in offshore aquifers is constant for different fresh groundwater discharge rates (under certain conditions). Otherwise, the interface is usually longer (flatter slope) in offshore aquifers than in onshore aquifers, except where the offshore limit of the aquifer is reached. The offshore extension of the aquifer leads to more seaward toe positions, increases the interface length and reduces the onshore seawater volume. As the freshwater discharge increases, the offshore freshwater volume becomes more vulnerable to impacts from changes in the freshwater discharge until the tip reaches the offshore limit or the toe crosses the coastline. For high values of freshwater discharge, the volume of freshwater stored offshore is more vulnerable to losses from changes in the freshwater discharge rate than is the onshore freshwater storage. For lower values of freshwater discharge, however, offshore freshwater storage is generally less vulnerable than onshore freshwater storage. Contrasts in the behaviour of onshore and offshore freshwater require that both need to be considered in coastal aquifer vulnerability assessments.

Experimental and numerical investigation of the effect of air injection on seawater intrusion mitigation

Previous studies have proposed compressed air injection to mitigate seawater intrusion, as a substitute for a hydraulic barrier created using freshwater injection. However, the current understanding of this strategy is based almost entirely on numerical simulation, and therefore, there is a need to investigate the complex processes accompanying this method within a physical setting. This study used sand tank experiments to explore the influence of air injection on the behavior of saltwater within a coastal confined aquifer, extending previous experiments by accounting for freshwater-saltwater density differences. Numerical modeling of the experiments assisted in interpreting experimental observations and allowed for field-scale conditions to be assessed. Numerical models were well matched to experimental observations, which showed a 34 % reduction in saltwater volume and a retreat of the saltwater toe length from 59 cm to 40 cm following air injection. A hypothetical field-scale confined aquifer model indicated that the largest seaward shift in the seawater wedge toe is obtained when the air-injection well is above the initial seawater wedge toe. However, maximal reductions in the seawater volume within the aquifer were obtained from injecting air within the original wedge rather than landward of the toe. This study provides the first physical evidence (through laboratory experiments) that injecting compressed air can effectively mitigate seawater intrusion. We considered a period of one year for field-scale applications, which show that the extent of desaturation likely needs to be mitigated from prolonged application of the method. Initial guidance is developed for the selection of air-injection locations, at least under simplified conditions (e.g. homogeneous, uniform aquifer, etc.).

Automated Method for the Sensitive Analysis of Volatile Amines in Seawater.

Methylamines are polar, volatile, and organic nitrogen-containing compounds. They are challenging to analyze, limiting our understanding of their occurrence and role within the marine nitrogen cycle. We describe an automated headspace solid-phase microextraction method, coupled with gas chromatography and nitrogen phosphorus detection (HS-SPME-GC-NPD), for analyzing methylamines in seawater. Three SPME conditions were investigated: temperature, equilibration, and extraction. The method was 6-24 times more sensitive to trimethylamine (TMA) than to dimethylamine (DMA) and monomethylamine (MMA). DMA and TMA were detected in small seawater volumes (2.5-10 mL), at volumes 100-400 times that previously reported. Detection limits of 19.1, 6.6, and 4.1 nM (nMol L-1) for MMA, DMA, and TMA, respectively, were measured in 10 mL sample volumes. Sample throughput was 4-6 times greater than previously reported similar methods. According to the Blue Applicability Grade Index (BAGI) metric, the method was considered "practical" and scored 62.5. The method was used to measure methylamines in seawater samples collected from the Southern Ocean. DMA and TMA were detected at concentrations from < LoD-35 nM and < LoD-48 nM, respectively. This study offers a systematic and standardized method for MA analysis in seawater and can significantly advance understanding of their role in marine systems.

Rapid removal and replacement of dissolved organic matter during circulation through ultramafic crust

Large volumes of seawater have passed through the rocky subseafloor throughout Earth's history. The scale of circulation is sufficiently large to impact the cycling of marine dissolved organic carbon (DOC), one of the largest pools of reduced carbon on Earth whose sources and sinks remain enigmatic, and to sequester carbon over geologic timescales. While the fate of DOC in numerous mafic systems has been examined, no previous reports are available on the less studied but still abundant ultramafic systems. We analyzed the concentration and composition of DOC from the Lost City hydrothermal field (30°N, Mid-Atlantic Ridge), a long-lived ultramafic system with minimal magmatic input. We show that per liter of seawater, more DOC is removed and a rate >650 times faster rate than in mafic ridge flank systems. Simultaneously, newly synthesized 14C-free organics are exported into the water column, adding a pre-aged component to the deep DOC pool. The sequestration of oceanic organic molecules onto minerals could partially account for the substantial total organic carbon present in ultramafic rocks, which is currently interpreted as evidence of chemoautotrophy or abiotic synthesis.

Continuous Flow-Double Purge and Trap Method for Preconcentrating Mercury in Large Volumes of Seawater for Stable Isotope Analysis.

Mercury (Hg) isotopes provide a useful tool to understand Hg sources and processes in the environment. The Hg isotopic composition of seawater remains poorly constrained due to the lack of an efficient method to process large volumes of low-Hg-concentration seawater samples. Here, we develop a continuous flow-double purge and trap device for the in situ preconcentration of Hg in seawater. This method yielded a good Hg recovery of 91.7 ± 3.3% (n = 4, 1SD) for spiked seawater samples and gave reasonably similar Hg isotope ratios of NIST 8610, indicating a limited matrix effect and limited Hg isotope fractionation during processing of seawater. NIST 8610 δ202Hg (-0.55 ± 0.09‰, n = 4, 1SD) and Δ199Hg (0.07 ± 0.02‰, n = 4, 1SD) were similar to previously published data. The method was successfully applied to seawater collected from the Xiamen Bay and the South China Sea. The seawater samples showed a Hg recovery of 91.6 ± 5.4% (n = 12, 1SD). Seawater Δ199Hg (-0.04 ± 0.05‰, n = 7, 1SD) in the Xiamen Bay was different from seawater Δ199Hg (0.05 ± 0.07‰, n = 5, 1SD) in the South China Sea, which implies distinct Hg sources to coastal and open ocean areas and highlights the robustness of our method in understanding the Hg isotopic composition of seawater.

Speciation and cycling of iodine in the subtropical North Pacific Ocean

Iodine intersects with the marine biogeochemical cycles of several major elements and can influence air quality through reactions with tropospheric ozone. Iodine is also an element of interest in paleoclimatology, whereby iodine-to-calcium ratios in marine carbonates are widely used as a proxy for past ocean redox state. While inorganic iodine in seawater is found predominantly in its reduced and oxidized anionic forms, iodide (I−) and iodate (IO3−), the rates, mechanisms and intermediate species by which iodine cycles between these inorganic pools are poorly understood. Here, we address these issues by characterizing the speciation, composition and cycling of iodine in the upper 1,000 m of the water column at Station ALOHA in the subtropical North Pacific Ocean. We first obtained high-precision profiles of iodine speciation using isotope dilution and anion exchange chromatography, with measurements performed using inductively coupled plasma mass spectrometry (ICP-MS). These profiles indicate an apparent iodine deficit in surface waters approaching 8% of the predicted total, which we ascribe partly to the existence of dissolved organic iodine that is not resolved during chromatography. To test this, we passed large volumes of seawater through solid phase extraction columns and analyzed the eluent using high-performance liquid chromatography ICP-MS. These analyses reveal a significant pool of dissolved organic iodine in open ocean seawater, the concentration and complexity of which diminish with increasing water depth. Finally, we analyzed the rates of IO3− formation using shipboard incubations of surface seawater amended with 129I−. These experiments suggest that intermediate iodine species oxidize to IO3− much faster than I− does, and that rates of IO3− formation are dependent on the presence of particles, but not light levels. Our study documents the dynamics of iodine cycling in the subtropical ocean, highlighting the critical role of intermediates in mediating redox transformations between the major inorganic iodine species.

Experimental analysis of triangular solar distiller with a new form of absorber

To better improve the evaporation of seawater in solar distillers, and consequently boost the production of distillate, we suggest that the structure of the conventional absorber surface should be modified. The present work aims to study the thermal performance of the Triangular Solar Distiller (Henceforth, TSD) by using a new form of a Trapezoidal Absorber (Henceforth, TA). This new design (Henceforth, TSDTA) proves to reduce the influence of shadow created by the sloped sidewalls and the volume of seawater of the TSD. The experimental results obtained from the TSD are compared to those obtained from a conventional Triangular Solar Distiller equipped with a Plate Absorber (henceforth, TSDPA) under the same weather conditions of Sfax – a central-eastern town Tunisia. The findings show that the trapezoidal structure of the absorber increases the diurnal production of distillate by 22.73% as compared to the plate one. The thermal efficiency reaches a maximum value of 49% for the TSDTA and only 46% for the TSDPA during the daytime.

Assessing land subsidence and analyzing tidal flooding in Tangerang, Banten

The increase in ocean temperature causes the expansion of seawater volume, resulting in an increase in sea level rise. The phenomenon of land subsidence also exacerbates the occurrence of tidal floods in coastal areas of Indonesia. This has prompted the need for a study of land subsidence and the distribution of tidal floods in Tangerang as a basis for taking anticipatory steps to reduce the negative impacts. The methods used for estimating land subsidence involved the SAR Sentinel-1A. The research utilized a total of 170 data points, spanning from 2017 until 2022. Data processing was carried out using the Parallel Small Baseline Subset method. The supporting data used in this study included SRTM data, tidal range, rainfall data, wind speed and direction. The results of this study reveal that the city of Tangerang has a maximum deformation value of -10.8 cm per year in the Periuk Sub District. Meanwhile, Tangerang Regency experienced land subsidence at a rate of -8.6 cm per year in Kosambi Sub District. Significant subsidence deformations occurred on the northeast side of Tangerang District and the southeast side of Tangerang City. Based on data analysis, it is evident that the total area inundated by tidal floods in Tangerang covers 33.267 hectares, with the largest affected area being in Pakuhaji District, spanning 9,262 hectares.

In Situ Capture and Real-Time Enrichment of Marine Chemical Diversity.

Analyzing the chemical composition of seawater to understand its influence on ecosystem functions is a long-lasting challenge due to the inherent complexity and dynamic nature of marine environments. Describing the intricate chemistry of seawater requires optimal in situ sampling. Here is presented a novel underwater hand-held solid-phase extraction device, I-SMEL (In Situ Marine moleculELogger), which aims to concentrate diluted molecules from large volumes of seawater in a delimited zone targeting keystone benthic species. Marine benthic holobionts, such as sponges, can impact the chemical composition of their surroundings possibly through the production and release of their specialized metabolites, hence termed exometabolites (EMs). I-SMEL was deployed in a sponge-dominated Mediterranean ecosystem at a 15 m depth. Untargeted MS-based metabolomics was performed on enriched EM extracts and showed (1) the chemical diversity of enriched seawater metabolites and (2) reproducible recovery and enrichment of specialized sponge EMs such as aerothionin, demethylfurospongin-4, and longamide B methyl ester. These EMs constitute the chemical identity of each targeted species: Aplysina cavernicola, Spongia officinalis, and Agelas oroides, respectively. I-SMEL concentrated sponge EMs from 10 L of water in a 10 min sampling time. The present proof of concept with I-SMEL opens new research perspectives in marine chemical ecology and sets the stage for further sustainable efforts in natural product chemistry.

Field test on the mechanism of composite bucket foundation penetrating sandy silt overlying clay

Composite bucket foundation has been gradually applied in China, involving six tilting supports to connect an upper pillar with a lower suction bucket with even honeycomb components separated by bulkheads. However, there are limited field measurements for such new type of offshore wind turbine foundation structure currently. In this study, field test campaign is launched to investigate the evolution of critical parameters for composite bucket foundation during the penetration process in soils. Results indicate that the coefficient of lateral pressure on the exterior skirt increases dramatically when traversing a shallow sandy silt layer, and the maximum value is approximately 2.81 times the passive soil pressure coefficient; the presence of negative pressure within the bucket causes a coefficient of lateral pressure on the interior skirt within the range between active and passive pressure coefficients. Nonetheless, as the penetration depth increases, the muddy-silty clay layer inside the bucket prevents further generation of seepage channels. By comparing the volume of seawater discharged from the bucket with its penetration volume into the mud surface, it is found that the bucket is under an over-speed penetration state. This study serves to promote the understanding of self-weight and negative pressure penetration mechanism for composite bucket foundation.

Comparison of methods to determine extraction efficiencies of Ra isotopes and 227Ac from large volume seawater samples

Radium isotopes, other than 226Ra, and 227Ac are typically present at low activities in the open ocean. The analysis of these isotopes thus requires the collection of large volumes of seawater and high sensitivity, low background instruments. To obtain the required large volumes (hundreds to thousands of liters), these radionuclides are typically preconcentrated on cartridge-style filters impregnated with MnO2 (Mn-cartridges) deployed on in-situ pumps. This technique, however, requires the determination of the extraction efficiency of the Mn-cartridges for the radionuclides of interest. For Ra isotopes, we used two methods to estimate the extraction efficiency of these Mn-cartridges at two stations on the South-West Indian Ridge in the Southern Ocean (GEOTRACES GS02). Method (1) compares the 226Ra activities recovered on the Mn-cartridges versus the activities determined in Mn-fibers, through which seawater was passed at a flow rate < 1 L min−1 to quantitatively sorb Ra (Mn-fiber method) while method (2) combines the 226Ra activities determined from two Mn-cartridges placed in series on in-situ pumps (A-B method). The second method is also applied to determine the 227Ac extraction efficiency. We find a relatively wide-range of Ra and 227Ac extraction efficiencies across the dataset (from 44.8% to 99.6% for Ra, and from 23.7% to 77.5% for 227Ac). Overall, the yield of 227Ac extraction is lower than that of Ra (mean value of 49.3 ± 19.0% for 227Ac, n = 10, mean value of 79.2 ± 10.3% for Ra, n = 13, using the Mn-fiber method; and a mean value of 63.9 ± 12.5%, n = 11 using the A-B method). Our dataset suggests that the Ra extraction efficiencies using either the A-B method or the Mn-fiber method are in relatively good agreement. Consequently, the 223Raex, 224Raex and 228Ra activities determined from the Mn-cartridges by applying the two Ra extraction yields are similar. We also show that the 227Ac extraction efficiency can be estimated from the Ra extraction efficiency allowing the use of a single Mn-cartridge. Finally, we recommend to determine the Ra and 227Ac extraction efficiencies in each individual Mn-cartridge, rather than applying a single extraction efficiency to all the Mn-cartridges, since a significant variability in the extraction efficiencies was observed between the different Mn-cartridges.

Effect of ocean warming on pigment and photosynthetic carbon fixation of plankton assemblage in Pingtan Island of Southeast China

Temperature plays an important role in affecting the physiological traits of marine plankton. In this study, we conducted an outdoor incubation experiment to investigate the effects of elevated temperature on Chl a, photosynthetic carbon fixation and the composition of plankton communities in the surface seawater around Pingtan Island, the northwest Taiwan Strait in Autumn 2022. After 3–4 days of incubation, elevated temperature (1–4 °C higher than ambient temperature) led to a decrease in Chl a concentration across all three stations, did not result in significant increases in the particulate organic carbon (POC) and nitrogen (PON) concentrations in seawater with high nitrate concentrations, whereas increased POC and PON concentrations in nitrate-limited seawater. These findings suggest that the effect of temperature on the POC and PON contents of plankton is affected by the availability of nitrate. Diatoms were the dominant phytoplankton group in all three stations. Our results indicate that ocean warming has a potential to increase the POC contents of marine plankton per volume of seawater, which may increase the ability of phytoplankton to absorb atmospheric CO2 and to alleviate global warming.

Analisis Kenaikan Muka Air Laut di Belawan

Climate change can cause an increase in sea temperatures which will have an impact on sea level rise due to the expansion of sea water volume and melting ice at the poles. Rising sea levels pose a threat to areas in coastal and coastal areas, one of which is Medan Belawan District. One of the impacts is tidal flooding. Tidal floods caused by high tides are then exacerbated by the phenomenon of rising sea levels so that it becomes a factor in increasing tidal flood inundation. The purpose of this study is to analyze sea level rise in Medan Belawan District by processing tidal data for 2012-2022 and sea level anomalies for 1993-2022 in the rate of sea level rise. The method used to calculate the tidal component uses the Admiralty method, sea level rise uses the linear regression method. The results of this study show that the value of sea level rise based on tidal data is 0.22 mm/year and 4.5 mm/year based on altimetry satellite data.

Inter-comparison of marine microbiome sampling protocols

Research on marine microbial communities is growing, but studies are hard to compare because of variation in seawater sampling protocols. To help researchers in the inter-comparison of studies that use different seawater sampling methodologies, as well as to help them design future sampling campaigns, we developed the EuroMarine Open Science Exploration initiative (EMOSE). Within the EMOSE framework, we sampled thousands of liters of seawater from a single station in the NW Mediterranean Sea (Service d'Observation du Laboratoire Arago [SOLA], Banyuls-sur-Mer), during one single day. The resulting dataset includes multiple seawater processing approaches, encompassing different material-type kinds of filters (cartridge membrane and flat membrane), three different size fractionations (>0.22 µm, 0.22–3 µm, 3–20 µm and >20 µm), and a number of different seawater volumes ranging from 1 L up to 1000 L. We show that the volume of seawater that is filtered does not have a significant effect on prokaryotic and protist diversity, independently of the sequencing strategy. However, there was a clear difference in alpha and beta diversity between size fractions and between these and “whole water” (with no pre-fractionation). Overall, we recommend care when merging data from datasets that use filters of different pore size, but we consider that the type of filter and volume should not act as confounding variables for the tested sequencing strategies. To the best of our knowledge, this is the first time a publicly available dataset effectively allows for the clarification of the impact of marine microbiome methodological options across a wide range of protocols, including large-scale variations in sampled volume.

Respiration Patterns in the Dark Ocean

AbstractIn the dark ocean, respiring organisms are the main sink for dissolved oxygen. The respiration rate in a given seawater volume can be quantified through dissolved oxygen drawdown or organic matter consumption as a function of time. Estimates of dissolved oxygen utilization rates (OUR) abound in the literature, but are typically obtained using proxies of questionable accuracy, often with low vertical resolution, and neglecting key regions such as the Southern and Indian oceans. Respiration rates based on particulate (POC) or dissolved (DOC) organic carbon are also sparsely observed and for DOC are unavailable in many regions. Consequently, the relative contributions of POC or DOC as a respiration substrate in the dark ocean are unknown. Here, we use recent datasets of true oxygen utilization, seawater age, and DOC to derive OUR and DOC consumption‐rate profiles in 10 oceanic regions. We demonstrate that although DOC and POC consumption rates are globally consistent with OUR, they underestimate OUR in the deep, suggesting strong oxygen utilization at the seafloor. In the abyss, we find a negative correlation of the DOC consumption rate with seawater age, suggesting that DOC reactivity decreases along the deep branch of the conveyor circulation. Our results highlight that benthic organisms are sensitive to perturbations in the surface production of organic matter and to large‐scale circulation changes that affect its supply to the abyss.

Growth Performance and Survival of Malabar Spinach (Basella alba) Applied with Different Volume of Seawater

Aims: The study focused on growth performance and survival of Malabar Spinach (Basella alba) applied with different volume of seawater, in Brgy. Bolila, Malita, Davao Occidental.&#x0D; Study Design: A experimental research design was employed in the study to determine indicators that were formulated to know the survival, number leaves and growth performance of the Malabar Spinach (Basella alba). Completely randomized design technique was employed for data gathering. (ANOVA) for analyzing. Mean, percentage and average frequency used in analyzing the findings of the data.&#x0D; Place and Duration of Study: The study was conducted between April 14, 2021 and May 31, 2021.&#x0D; Methodology: The experiment was arranged completely randomized design with three replicates for each treatment. There was one plant in each pot and five treatments in each replicate. CRD (Complete Random Design) with (5) treatments and replicates of three (3). The treatment was the following: Treatment 1 – tap water, Treatment 2 – 5ml seawater, Treatment 3 – 10ml seawater and 10ml tap water, Treatment 4 – 15ml seawater and 15 tap water, Treatment 5 – 20 ml seawater and 20 ml tap water.&#x0D; Results: Overall growth performance of Malabar Spinach showed that treatment 5 gained the highest value of mean, with 150 pots in terms of final increment on the Growth (height). In terms of number of leaves on the Growth of Malabar Spinach vegetable, treatment 5 obtained the highest value of mean in replicate 3, and treatment 1 which exhibited lowest value of mean. In terms of Survival Rate of Malabar Spinach (Basella alba), treatment 5 obtained the highest value of mean in sampling period with the corresponding final growth of effect with different ratio treatment of sea H2O samples and common water samples. Based on the results on the effect of seawater on the survival rate of Malabar Spinach, the result showed that treatments obtained the highest value of mean in terms of growth. In terms of number of leaves, Treatment 1 (tap water) obtained the highest value of mean. In terms of Survival, Treatment 1 obtained the highest value of mean&#x0D; Conclusion: The result showed that treatments obtained the highest value of mean in terms of growth. In terms of number of leaves, Treatment 1 (tap water) obtained the highest value of mean. In terms of Survival, Treatment 1 obtained the highest value of mean. Based on the statistical One Way ANOVA, the results revealed that there is a statistically significant difference of growth performance of Malabar Spinach from the six treatments. The result showed that treatment 5 was the highest value of mean from the sampling period given. The results also revealed that there is no significant difference on the number of leaves, length and survival of Malabar Spinach vegetable as applied with different volume of seawater in six sampling of the study.

Radionuclides' Recovery from Seawater Using FIC and FIC A Sorbents.

To solve radioecological and oceanological problems (estimate the vertical transport, flows of particulate organic carbon, phosphorus biodynamics, submarine groundwater discharge, etc.), it is necessary to determine the natural values of the radionuclides' activity in seawater and particulate matter. For the first time, the radionuclides' sorption from seawater was studied using sorbents based on activated carbon modified with iron(III) ferrocyanide (FIC) and based on activated carbon modified with iron(III) hydroxide (FIC A-activated FIC) obtained by FIC sorbent treatment with sodium hydroxide solution. The possibility of trace amounts of phosphorus, beryllium, and cesium recovery in laboratory conditions has been investigated. Distribution coefficients, dynamic, and total dynamic exchange capacities were determined. The physicochemical regularities (isotherm and kinetics) of sorption have been studied. The results obtained are characterized via Langmuir, Freindlich, and Dubinin-Radushkevich isotherm equations, as well as pseudo-first and pseudo-second-order kinetic models, intraparticle diffusion, and the Elovich model. Under expeditionary conditions, the sorption efficiency of 137Cs using FIC sorbent, 7Be, 32P, and 33P-using FIC A sorbent with a single-column method by adding a stable tracer, as well as the sorption efficiency of radionuclides 210Pb and 234Th with their natural content by FIC A sorbent in a two-column mode from large volumes of seawater was assessed. High values of efficiency of their recovery by the studied sorbents were achieved.

Compounding deep sea physical impacts on marine microbial motility

IntroductionApproximately three-fourths of all pelagic marine prokaryotes live in the deep sea, an environment characterized by high hydrostatic pressure and, in most cases, low temperature. Labile organic matter is often scarce within these settings, providing a competitive advantage to motile cells that can access the nutrients within a greater seawater volume. Because many cells present at depth are shallow water-adapted microbes descending from more productive surface waters, deep-sea conditions could significantly reduce their motility and, consequently, their biogeochemical activities.MethodsIn this study, we address this possibility by examining the impact of deep-sea physical conditions on the motility of three representative marine microbes belonging to the cosmopolitan genera Halomonas, Alcanivorax, and Shewanella. Growth-dependent motility agar assays and growth-independent microscopy assays were employed at four pressures and two temperatures.ResultsAt pressures equivalent to bathyal and abyssal depths (10 – 50 Megapascals), decreases in temperature (30°C – 4°C or 23°C – 7°C depending on the assay) had a greater negative impact on motility than pressure. In addition, the high-pressure and low-temperature impacts were additive. Exposure to high pressure and/or low temperature had varying degrees of effect on flagellar function, depending on the strain and the magnitude of the applied stress. These ranged from short-term impacts that were quickly reversible to long-term impacts that were detrimental to the function of the flagellum, leading to complete loss of motility.DiscussionThese findings highlight the sensitivity of motility systems of piezosensitive mesophilic marine bacteria to the combined pressure/temperature conditions present in the deep sea, phenotypes that in situ are likely to manifest themselves in the modulation of diverse microbial activities.

Isolation and Staining Reveal the Presence of Extracellular DNA in Marine Gel Particles.

Marine gel particles (MGP) are amorphous hydrogel exudates from bacteria and microalgae that are ubiquitous in the oceans, but their biochemical composition and function are poorly understood. While dynamic ecological interactions between marine microorganisms and MGPs may result in the secretion and mixing of bacterial extracellular polymeric substances (EPS) such as nucleic acids, compositional studies currently are limited to the identification of acidic polysaccharides and proteins in transparent exopolymer particles (TEP) and Coomassie stainable particles (CSP). Previous studies targeted MGPs isolated by filtration. We developed a new way of isolating MGPs from seawater in liquid suspension and applied it to identify extracellular DNA (eDNA) in North Sea surface seawater. Seawater was filtered onto polycarbonate (PC) filters with gentle vacuum filtration, and then the filtered particles were gently resuspended in a smaller volume of sterile seawater. The resulting MGPs ranged in size from 0.4 to 100 µm in diameter. eDNA was detected by fluorescent microscopy using YOYO-1 (for eDNA), with Nile red (targeting cell membranes) as a counterstain. TOTO-3 was also used to stain eDNA, with ConA to localise glycoproteins and SYTO-9 for the live/dead staining of cells. Confocal laser scanning microscopy (CLSM) revealed the presence of proteins and polysaccharides. We found eDNA to be universally associated with MGPs. To further elucidate the role of eDNA, we established a model experimental MGP system using bacterial EPS from Pseudoalteromonas atlantica that also contained eDNA. Our results clearly demonstrate the occurrence of eDNA in MGPs, and should aid furthering our understanding of the micro-scale dynamics and fate of MGPs that underly the large-scale processes of carbon cycling and sedimentation in the ocean.