Seawater Source Research Articles

16S rRNA sequences of Exiguobacterium spp. bacteria dominant in a biofloc pond cultured with whiteleg shrimp, Penaeus vannamei

Biofloc technology is being applied increasingly in shrimp aquaculture. Many countries have adopted this technology to increase shrimp aquaculture production. Owing to its major importance, this study was conducted to identify the bacterial population from biofloc aquaculture shrimp pond water of Singkir Laut, Kedah, Malaysia. Samples of mature biofloc were collected from the biofloc pond water at different shrimp ages (day of culture [DOC]): DOC30, DOC60 and DOC90. Overall, 43 sequences of bacterial species were blasted, which were identified as Exiguobacterium spp., Bacillus spp., Vibrio spp., Acinetobacter junii, Cobetia marina, Rheinheimera aquimaris and Pseudoalteromonas spp. These bacterial species were identified mostly from heterotrophic plate count agar. The bacterial species of Exiguobacterium aestuarii, Exiguobacterium profundum and Exiguobacterium aurantiacum were identified with 16S rRNA gene sequence similarities of 98.45–99.44%. Bacterial species of Bacillus pumilus, Bacillus velezensis, Bacillus cereus, Bacillus safensis and Bacillus subtilis were identified with 16S rRNA gene sequence similarities of 98.81–99.21%. Bacterial species of Vibrio diazotrophicus, Vibrio diabolicus, Vibrio natriegens and Vibrio harveyi were identified with 16S rRNA gene sequence similarities of 98.03–99.19%. Bacteria from Rheinheimera aquimaris were also identified with 16S rRNA gene sequence similarities of 98.69–99.26%; this bacterium is a novel bacterium identified from biofloc samples of the present study and has not been reported from biofloc samples in any previous study. Exiguobacterium spp. from the novel strains of E. aestuarii and E. profundum were identified as dominant, with 23 of 43 samples isolated from a shrimp pond at time points DOC30, DOC60 and DOC90; these bacteria are Gram-variable rod-shaped organisms that are capable of producing extracellular enzyme activity to break down chemical structures, thereby helping to remove organic compounds from aquaculture waste. Exiguobacterium spp. are usually identified in tidal flat sediments and on muddy sea coasts. This discovery is consistent with the site of the shrimp pond near to a muddy beach area, which might be the source of seawater leading to the predominance of this type of bacteria in the biofloc samples in the studied pond.

Hydrogeochemical processes controlling the groundwater salinity in the coastal aquifers of Southern Tamil Nadu, India

The current study identifies groundwater quality issues and investigates the most important geochemical processes that control seawater intrusion using various ionic ratios, hydrochemical facies evolution, and geochemical modelling. Cl-/Br ratio is an important indicator to identify the origin of groundwater salinity in coastal aquifers. Nineteen percent of the groundwater samples with Cl−/Br− ratio similar to that of Standard Mean Ocean Water (SMOW) are affected by seawater intrusion in the study area. Particularly, nine groundwater samples have high chloride values and are similar to SMOW, and it may derived salinity from seawater sources from the Bay of Bengal due to the over-pumping of production wells in the Uvari zone. Five samples are similar to SMOW, which is due to the presence of salt pan activities. The bivariate plots such as Ca2+ + Mg2+ vs Cl−, EC vs Cl−, and Na+/Cl− ratio indicate that seawater intrusion is the primary source for groundwater salinisation. Evaporation is the dominant process controlling groundwater chemistry, rather than rock-water interaction and precipitation, according to mechanisms controlling groundwater chemistry. Direct ion exchange and converse ion exchange are the critical controlling factors for groundwater salinisation, according to the hydrochemical facies evolution diagram (HFED). The water quality index (WQI) shows that most groundwater belongs to the poor to the marginal category. The saturation indices show that the groundwater samples are saturated with minerals such as dolomite, calcite, aragonite and magnesite. Therefore, these minerals are susceptible to precipitation due to the effective leaching of calcareous minerals from the bedrocks. Compiled hydrogeochemical analysis and multivariate statistical analysis revealed that the Tiruchendur and Uvari zone was affected by the seawater intrusion and led to an increase in the salinity of the groundwater.

Design and assessment of water source alternatives for Mariout 2 water treatment plant extension

Abstract Factors such as population increase and industrialization, coupled with the establishment of touristic villages, have necessitated an upgradation of water treatment plants (WTPs) in Egypt. In this study, three different water source alternatives were designed and compared with a simple decision matrix to select the most appropriate one for upgrading and extending the Mariout 2 WTP. The first two alternatives are located on the k-40 Alex-Cairo desert road and k-77 EL Nasr canal, respectively, where the water source is obtained from the Nile River. The third alternative is located at the k-51 Alex-Matrouh coastal road and a non-conventional seawater source is used. The design results showed that the required energy power of the first, second, and third alternatives were 0.31, 0.066, and 0.72 kw/purified m3, respectively. The operational costs of the first, second, and third alternatives were 0.665, 0.426, and 6.621 EGP/m3, respectively. The cost of the intake pipes was found to be the lowest for the third alternative, whereas it was found to be the highest for the first one. Based on the results obtained from the decision matrix, the third alternative was found to be the most appropriate alternative followed by the second one. This study may assist in making decisions regarding the water source selection and treatment methods for the extension of the fourth stage of the Mariout 2 WTP.

Correlating trace element compositions, petrology, and Raman spectroscopy data in the ∼3.46 Ga Apex chert, Pilbara Craton, Australia

The Apex chert unit (∼3.46 Ga, Pilbara Craton, Australia) constitutes one of the oldest sedimentary units on Earth in which putative carbonaceous microfossils have been reported. The source of carbonaceous matter (CM) in this unit, however, is hotly debated. Hydrothermal fluids have circulated through the underlying crust and up into the bedded unit; these fluids could have remobilized sedimentary microbial biomass, generated abiological hydrocarbons, or harbored in situ chemolithoautotrophic microbial communities. Are there parts of the unit where microfossils might be best preserved?A potential fossil microbiota – if present – would probably be best preserved in the stratiform portion of the unit where hydrothermal influence seems to have been lowest. In order to shed light on the history of hydrothermal overprinting and the source of carbonaceous fractions in the Apex chert, we correlate here at a high spatial resolution petrographic observations and trace element analyses over a transect from the dyke where putative microfossils were found to the stratiform part where remnants of microbial mats were found. The layered, stratiform part of the unit has positive La anomalies up to 1.7, and Light Rare Earth Element depletions, indicating a seawater source. However, as far as 300 m from the dyke, the stratiform part also shows hydrothermal brecciation, high Eu anomalies (2–12; µ = 4.2) and chondritic Y/Ho ratios (24.3–30.3; µ = 27.0), indicating that hydrothermal fluids have laterally infiltrated over large distances. Overall, the pervasive influence of hydrothermal fluids throughout the entire unit and the presence of carbonaceous matter both in the sedimentary part and the hydrothermal dyke is consistent with a ‘hydrothermal pump’ model that was earlier proposed for the nearby Dresser Formation. In this model, organic matter from surface environments is circulated along with hydrothermal fluids and redistributed in the crust and overlying sediments, therefore complicating paleobiological interpretations. Raman measurements show that most of the CM experienced temperatures of ∼350 °C, while some samples contain CM with a variable, but markedly lower maturity (temperature ranging from 200 to 350 °C). Correlation to texture points out a potential mixing of pre-metamorphic CM with post-metamorphic CM during late hydrothermal events.

Renewable Water Harvesting by Amyloid Aerogels and Sun

AbstractSolar distillation is an appealing and facile technology for seawater desalination and water purification, but constructing stable, environmentally‐friendly, and cost‐effective solar evaporators often remain unfeasible. Here, amyloid hybrid aerogels are introduced for universal and renewable freshwater production by relying on the combination of sustainable materials and solar energy, thus making the process highly ecological and virtually costless. Amyloid fibrils obtained from whey, a byproduct of the dairy industry, are used as the main scaffold for the aerogels, whose solar energy harvesting properties of the top surface are enhanced by bioinspired dark polymers, such as polydopamine. Due to the fast water transport throughout the porous aerogels, the high‐yielding photothermal conversion ability of the top surface, and efficient heat insulation at the bottom, the hybrid amyloid fibrils aerogel exhibits a water evaporation rate of 1.61 kg·m−2 h−1 with a solar‐thermal conversion efficiency as high as 91.3% under 1 sun illumination. The process allows desalinating various seawater sources with different salinities to levels below the drinking water threshold recommended by the World Health Organization. Moreover, the same hybrid amyloid evaporator is highly efficient in removing heavy metals, organic pollutants, bacteria, and viruses from water, introducing a general, sustainable and energy‐efficient solution for desalination and water purification.

Study of Biocrudes Obtained via Hydrothermal Liquefaction (HTL) of Wild Alga Consortium under Different Conditions

Microalga-based fuels are promising solutions for replacing fossil fuels. This feedstock presents several advantages such as fast growth in a harsh environment and an ability to trap gases emitted from industries, thus reducing global warming effects. An efficient way to convert harvested microalgae into biofuels is hydrothermal liquefaction (HTL), which yields an intermediate product called biocrude. In this study, the elemental and molecular compositions of 15 different HTL biocrudes were determined by means of different techniques. Wild algae were cultivated in an industrial environment with plant emissions as a carbon source in fresh or seawater. It was notably observed that the culture medium had an influence on the biochemical composition and mineral matter content of algae. Thus, seawater algae were characterized by larger amounts of carbohydrates and mineral matter than freshwater ones, which also affected the oil yields and the light and heavy fractions of biocrudes.

Predicting Flux Rates against Pressure via Solution-Diffusion in Reverse Osmosis Membranes

This paper suggests a new method of predicting flux values at Reverse Osmosis (RO) desalination plants. The solution-diffusion model is utilized to determine the osmotic pressure drops for seawater sources. The same technique was applied to the groundwater source at the Abqaiq plant (500 RO plant) to calculate the osmotic pressure. The calculated osmotic pressures were utilized to determine the appropriate flux rates and membrane resistances of different BWRO Toray membranes and a performance comparison between various membranes has been established. The model results confirm an inverse relationship between membrane thickness and water flux rate. Also, a proportional linear relation between the overall water flux and the applied pressure is identified. Higher flux rates and lower salinity indicate lower membrane resistance yielding higher production. The modeled data predict that BWRO Toray TM720D-440 with an 8" membrane is the optimal choice for treating waters from the three water sources at the Abqaiq plant.

Biogeochemical reappraisal of the freshwater–seawater mixing‐zone diagenetic model

AbstractFirst proposed nearly half a century ago, the mixing‐zone model of dolomitization enjoyed a brief stay in the limelight before falling out of favour. Despite extended past criticism, arguments that build on its current validity are presented and discussed. The coastal mixing zone can be seen as an aquifer system exhibiting marked physicochemical gradients, reflective of the admixture of low salinity freshwater and seawater sources with variable redox potentials. This perspective requires a more holistic look at the mixing zone, not only as a gradient of major element concentrations, but also as the locus of enhanced subsurface redox sensitive reactions that occur at the pore‐space scale within a moveable diagenetic front. Combined genomic and isotopic data indicate that an active subsurface biosphere thrives in the mixing zone. This could facilitate Mg2+ dehydration, generate alkalinity, consume protons and mobilize potentially catalyzing ions (i.e. Mn and Zn), which are all low temperature factors thought to promote dolomite formation from soluble precursors. In the updated model, the advective mix of fluids with contrasting composition modulate a range of biogeochemically induced mineral dissolution and reprecipitation reactions. Biotic and abiotic interactions between these fluids affect carbonate equilibrium and result in dissolution of soluble aragonitic and calcitic phases, while dolomite precipitates (as cement) and neomorphic replacement. The secondary dolomite often exhibits compositional heterogeneity and contentious δ18O signatures indicative of re‐equilibration. The role of manganese, zinc, intermediate sulphur species and ammonia are far from being fully understood, nor is their fingerprint in ancient deposits. Application of in situ spectroscopic imaging techniques, clumped and metal isotope analyses, as well as a more extended use of traditional approaches, such as sulphur isotopes, are poised to open many opportunities to further explore the biogeochemistry of this diagenetic environment and how it relates to platform dolomitization.

Degradation modeling of water environmental DNA: Experiments on multiple DNA sources in pond and seawater

AbstractEnvironmental DNA (eDNA) analysis methods have been developed to detect organism distribution and abundance/biomass in various environments. eDNA degradation is critical for eDNA evaluation. However, the dynamics and mechanisms of eDNA degradation are largely unknown, especially when considering different eDNA sources, for example, cells and fragmental DNA. We experimentally evaluated the degradation rates of eDNA derived from multiple sources, including fragmental DNA (internal PCR control [IPC]), free cells (from Oncorhynchus kisutch), and resident species. We conducted the experiment with pond and seawater to evaluate the differences between freshwater and marine habitats. We quantified the eDNA copies of free cells, fragmental DNA, and resident species (Cyprinus carpio in the pond and Trachurus japonicus in the sea). We found that eDNA derived from both cells and fragmental DNA decreased exponentially in both the sea and pond samples. The degradation of eDNA from resident species showed similar behavior to the cell‐derived eDNA. We evaluated three degradation models with different assumptions and degradation steps and found that a simple exponential model was effective in most cases. Our findings on cell‐ and fragmental DNA‐derived eDNA provide fundamental information about the eDNA degradation process and can be applied to quantify eDNA behavior in natural environments.

Suitability Evaluation of Seawater Source Heat Pump in a Seashore Refrigeration Station

In this paper, the suitability of using seawater source heat pump in a seaside refrigeration station in Qingdao was evaluated. A systematic evaluation was made on the conventional chiller with cooling tower system, the conventional chiller with titanium plate heat exchanger system and the seawater source heat pump system, including energy saving evaluation, economic evaluation (initial investment cost and operating cost) and environmental evaluation. The evaluation results showed that the initial investment cost was slightly increased, the operating cost was low, the cop value was high and the impact on the marine environment was small when the seawater source heat pump system was directly used.

Efforts to Reduce SO2 Emission in Paiton Coal-Fired Power Plant

Several breakthrough methods are needed to reduce the exhaust emissions of coal combustion in the boiler in order to meet the environmental quality standard requirements. The implementation of coal mixing is one of the short-term programs to reduce SO2 emissions, which is carried out by mixing several types of coal which have different calorific values and sulfur content to obtain the right coal mixture so that coal combustion will produce low SO2 emissions. Supply of coal with low sulfur content is getting smaller due to limited reserves, which causes the coal switching method will no longer be effective. Installation of flue gas desulfurization (FGD) facilities is an effective way to reduce SO2 emissions. Considering the condition and location of the Paiton 1-2 coal-fired power plant, the seawater desulfurization system is the most appropriate to be implemented because it is close to abundant seawater sources and the system has high reliability and effective economic value. By implementing flue gas desulphurization, SO removal efficiencies will be more than 95%.

Multistage electrodialysis for desalination of natural seawater

Electrodialysis (ED) is receiving increasing attention as promising technology for seawater desalination. However, most of the ED investigations are typically performed using artificial NaCl solutions, while the effect of multivalent ions (such as Mg2+ and Ca2+) on membrane scaling and resistance has been so far overlooked. In this work, we investigate the influence of multivalent ions in seawater on the desalination performance of multistage ED. In particular, natural seawater was used as feed solution, and two different strategies were compared, i.e. by using conventional cation exchange membranes (CEMs), as well as CEMs with preferential removal of multivalent ions. For both CEMs, we found that the removal of calcium and magnesium was higher compared to that of sodium and no effect due to operation at low current density was observed. More magnesium was removed with the multivalent ion permeable CEM. Starting from ~27 g/l (i.e. inlet concentration of the natural seawater source), the upscaled multistage ED system produced a continuous diluate concentration of 1.9 g/l. The system performance was stable over 18 days, with an average energy consumption of 3 kWh/m3, demonstrating the potential of multistage ED seawater desalination.

Polycyclic Aromatic Hydrocarbons in the North Atlantic Ocean and the Arctic Ocean: Spatial Distribution and Water Mass Transport

It is still not clear what role the oceanic transport plays in the fate of persistent organic pollutants (POPs) in the Arctic Ocean. The strong-stratified Arctic Ocean undergoes complex inputs and outputs of polycyclic aromatic hydrocarbons (PAHs) from the neighboring oceans and continents. To better understand PAHs’ transport processes and their contribution in high-latitude oceans, surface seawater, and water column samples were collected from the North Atlantic Ocean and the Arctic Ocean in 2012. The spatial distribution of dissolved PAHs (∑9PAH) in surface seawater showed an “Arctic Shelf > Atlantic Ocean > Arctic Basin” pattern, with a range of 0.3-10.2 ng L-1. Positive matrix factorization (PMF) modeling results suggested that vehicle emissions and biomass combustion were the major PAHs sources in the surface seawater. According to principal component analysis (PCA), PAHs in different water masses showed unique profiles indicating their different origins. The net transport mass flux of PAH individuals ranged from -4.4±1.7 to 53±39 tons/year to the Arctic Ocean, with a sum of 63±53 tons/year. The direct contribution of ocean currents was limited for PAHs transporting to the Arctic Ocean, but their role in modulating atmospheric POPs should be further considered.

Identification of a Novel Thermostable Alkaline Protease from Bacillus megaterium-TK1 for the Detergent and Leather Industry.

Simple SummaryIn the current investigation, we describe the characteristic features of a novel Bacillus megaterium bacterium-derived protease with excellent thermostable enzyme activity under stringent alkaline conditions. The protease is highly compatible with various detergents and thus appears to be an eco-friendly additive for a variety of industrial applications.An increased need by the green industry for enzymes that can be exploited for eco-friendly industrial applications led us to isolate and identify a unique protease obtained from a proteolytic Bacillus megaterium-TK1 strain from a seawater source. The extracellular thermostable serine protease was processed by multiple chromatography steps. The isolated protease displayed a relative molecular weight (MW) of 33 kDa (confirmed by zymography), optimal enzyme performance at pH 8.0, and maximum enzyme performance at 70 °C with 100% substrate specificity towards casein. The proteolytic action was blocked by phenylmethylsulfonyl fluoride (PMSF), a serine hydrolase inactivator. Protease performance was augmented by several bivalent metal cations. The protease tolerance was studied under stringent conditions with different industrial dispersants and found to be stable with Surf Excel, Tide, or Rin detergents. Moreover, this protease could clean blood-stained fabrics and showed dehairing activity for cow skin with significantly reduced pollution loads. Our results suggest that this serine protease is a promising additive for various eco-friendly usages in both the detergent and leather industries.

Solar hydrogen production from seawater splitting using mixed-valence titanium phosphite photocatalyst

A unique magnesium salt of titanium phosphite (MgTiP) was synthesized by the hydrothermal method and applied for the photocatalytic hydrogen evolution using seawater. The spent MgTiP was analyzed by XPS after photocatalytic reaction indicating that Ti3+ in MgTiP structure was oxidized to Ti4+ by photo-induced holes in a pure water environment, i.e., photo-corrosion. A sacrificial agent, 2 mM FeCl2 in the photocatalytic system, could enhance hydrogen evolution and prevent photo-corrosion of MgTiP. Thus this research conducted the reaction of photocatalytic hydrogen evolution using seawater. Two seawater sources were taken from the estuary of the Tamsui River and the east coast of Taiwan. The ions in seawater could act as a sacrificial agent. The result showed that the ions of seawater could enhance photocatalytic hydrogen evolution and also prevent MgTiP from photo-corrosion. The unique 12-membered ring (12 R) channels structure of MgTiP with tunable hexa-hydrated magnesium ions showed excellent photo-stability. The concentration of proton (pH) and chloride ions as hole scavenger were favorable factors. Its H2 production rate could reach up to 629.3 µmol·gcat−1·h−1 under simulated sunlight. Furthermore, the hydrogen evolution from photocatalytic seawater splitting showed better stability than pure water in a long-term test.

Isotope evidence for multiple sources of B and Cl in Middle Miocene (Badenian) evaporites, Carpathian Mountains

Evaporites of Middle Miocene Badenian stage occur widely in basins from the Carpathian Mountain region (Poland, Slovakia and Ukraine), but their source and formation process are still debatable. A detailed boron isotope study in combination with previous chlorine isotope and chemistry data of the salt samples from three localities (Wieliczka mine, Trans-Carpathian Basin, East Slovakian Basin) reveal ranges of δ11B (−4.5 to +35.7‰) and δ37Cl (−0.2 to +0.8‰). Modelling calculation indicates that both Rayleigh fractionation and incorporation of fluid inclusion solutes cannot cause such a large shift on δ11B values in halite. Instead, the B and Cl isotope data imply multiple brine sources, including evaporite brine, dissolved diapiric halite and basin brine in addition to the predominant seawater source during the formation of these evaporites. At Wieliczka salt mine, a positive δ11B excursion (from −5‰ to + 30‰) matches the negative δ37Cl variation (from +0.5 ± 0.1‰ to -0.2‰) stratigraphically upwards, which indicate both terrestrial boron and non-marine chloride made significant contributions to the composition of the basin brine during the early development of the basin. In the upper column, the δ11B values are within the marine range, but show influence by the sorption of boron onto clay, whereas the δ37Cl values at +0.5‰ still indicate the presence of non-marine chloride, possibly from recrystallized, diapiric halite. In the Trans-Carpathian Basin, constant δ37Cl (+0.3‰) and δ11B (+15‰) in the middle of the profile are consistent with a dominant marine source, whereas the lower δ11B (+2.2‰) and higher δ37Cl (+0.8‰) in the lower column suggest terrestrial fresh water flowed into the basin during the formation of basal halite. Halites in the upper part of the profile show near 0‰ of δ37Cl, suggesting incorporation of Cl from a mixture of expelled basin brines. In the Slovakian Basin, the δ11B values (+18.1 to +19.1‰) at the base of the profile lie within the marine range, but high δ37Cl values (+0.7 to +0.8‰) require a non-marine chloride source. In the upper part of the profile, boron isotope data indicate a change from marine (+12.2 to +23.4‰) to non-marine (+5.4 to +6.1‰) derivation of B, but the sources of Cl remain marine (+0.0 to +0.5‰). Overall, both B and Cl isotopes show coupled variation in the Middle Miocene Badenian evaporites and suggest multiple sources of B and Cl.

MH-ICP-MS Analysis of the Freshwater and Saltwater Environmental Resources of Upolu Island, Samoa.

The elemental composition of freshwater and saltwater samples around the South Pacific island of Upolu, Samoa has been investigated together with other indicators of water quality. Up to 69 elements from Li (3) to U (92) are measured in each sample, analyzed by Mattauch–Herzog-inductively coupled plasma-mass spectrometry (MH-ICP-MS). One hundred and seventy-six samples were collected from surface freshwater sources (24 rivers, two volcanic lakes, one dam) and from seawater sources from the surface to 30 m depth (45 inner reef, reef, and outer reef locations) around Upolu Island, including river mouths and estuaries. Principal component and hierarchical clustering correlation analyses were performed on quantile normalized log transformed elemental composition data to identify groups of samples with similar characteristics and to improve the visualization of the full spectrum of elements. Human activities, such as the use of herbicides and pesticides, may relate to observed elevated concentrations of some elements contained in chemicals known to have deleterious obesogenic effects on humans that may also cause coral reef decline. Furthermore, the salinity of some saltwater samples tested were very high, possibly due to climate variability, which may additionally harm the health and biodiversity of coral reefs.

Nonstationary angular distribution of optical field radiance from an isotropic source in sea water

The spatial-angular and temporal characteristics of the radiance of the light field emitted by a nonstationary point isotropic source in sea water are studied. Using the Monte Carlo method, we calculated the pulse transfer functions and frequency responses of the angular radiance distributions at various distances from the source. Particular integral characteristics of the angular radiance distributions are estimated. It is shown that with an increase in the delay time, measured from the time of arrival of ballistic photons, the angular radiance distribution asymptotically tends to be isotropic. The frequency and phase responses of the alternating radiance component from a source modulated by power at a high frequency are studied. It is shown that with an increase in the modulation frequency, the angular distribution of the alternating radiance component is concentrated close to the direction to the source.

Optimal Stocking Density of Vannamei Shrimp Lytopenaeus Vannamei at Low Salinity Using Spherical Tarpaulin Pond

The worsening environmental conditions cause disease attack on shrimp farming cannot be avoided, the high cost of Vannamei shrimp production resulting in shrimp farming can only be owned by certain circles. Therefore, it is necessary to find alternative shrimp farming in order to avoid disease and affordable cost to increase production. The farming of vannamei shrimp (Lytopenaeus vannamei) using tarpaulin is expected to minimize production cost, utilize narrow land and far from sea water source, and facilitate control of shrimp health at the time of cultivation. The aim of this research is to obtain the data of shrimp average weight (Mean Body Weight), survival rate and best Food Conversion Ratio for vannamei shrimp at low salinity using container of 1 m3 tarpaulin pond with three different densities which are: A (density of 175 shrimp/m3), B (225 shrimp/m3) and C (275 shrimp/m3) with three replications. Shrimp seeds used were PL 11 (post larvae) which acclimatized prior to the treatment along with the decrease of media salinity until 5-10 ppt for 7 days, then shrimp seeds were placed on the tarpaulin pond according to the treatment. Maintenance was performed for 60 days with Feeding Rate of 5-10% and 4 times/day feeding frequency. Based on the result of the research, it was found that the optimal stocking density of shrimp was shrimp rearing with the density of 175 shrimp/m3 with Mean Body Weight (MBW) value of 10.52 + 0.2 gram, Survival Rate (SR) of 91.39 + 1.0% and Food Conversion Ratio (FCR) of 1.6 ± 0.1. Based on the Tukey test (<0.05) showed that stocking density had an effect on shrimp average weight and vannamei shrimp survival rate.

Molecular-Level Chemical Characterization of Dissolved Organic Matter in the Ice Shelf Systems of King George Island, Antarctica

Antarctic shelf systems play an important role in organic matter circulation on Earth; hence, identifying the characteristics of dissolved organic matter (DOM) can be a good indicator for understanding its origin, as well as climate change. In this study, to identify the characteristics of DOM in the ice shelf systems, surface water was collected from the open sea (OS) and Marian cove (Fjord; FJ). Although there were no differences in DOM characteristics between sampling sites in quantitative analyses, the DOM in surface water of each region seemed to be more affected by terrestrial than marine biological sources in optical and molecular properties. This finding indicates that the terrestrial DOM related to mosses based on the molecular properties results; high levels of lipid-like (35–39%) and unsaturated hydrocarbon-like (UH; 27–34%) in both the OS and FJ regions, and significantly higher tannin-like substance and condensed aromatic structures (CAS) in the FJ than the OS region. When comparing the FJ transect samples, those nearest to a glacier (FJ1; 0.93 km from the glacier) showed relatively low salinity, high dissolved organic carbon (DOC), and high chromophoric DOM (CDOM), indicating that terrestrial DOM (possibly produced by moss) inflow occurred with the runoff from the freshly melting land ice and glacier. However, no significant differences in molecular composition were detected, suggesting that terrestrial DOM introduced into the ice shelf systems by melting land ice and glacier runoff could be a major source of DOM-rich seawater during austral fall, when low marine biological activity occurs. This study has a great significance as background data for DOM characteristics in the ice shelf systems due to the enhanced biological activity during the austral summer.