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- Progress in the Industry-University-Institute Cooperative Use of Research
Vessels-
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Abstract: Abstract With the support of the Ministry of Oceans and Fisheries of Korea, the Korea Institute of Ocean Science and Technology (KIOST) promoted ‘The study for the industry-university-institute cooperative use of research vessels’, which was an opportunity to advance domestic ocean research to the next level, in line with the launch of the R/V Isabu in 2017. A brief history in relation to the project is described in Lee (Ocean Sci J 57(2), 2022) in this issue. Celebrating the 5th year of the project, KIOST (Marine scientists on a boat, KIOST Korea Institute of Ocean Science and Technology, Busan, 2021) has published a resource book on the progress of the project excluding scientific papers. In this special issue, some of the scientific results from the project are grouped together and introduced. The joint use of research vessels started with large research vessels and gradually expanded to small research vessels. Thus, the target area of the study also included from the open ocean to the coastal waters (KIOST, in Marine scientists on a boat, KIOST Korea Institute of Ocean Science and Technology, Busan, 2021) as shown in the papers featured in this issue.
PubDate: 2022-06-22
- Multi-proxy Stratigraphy and Paleoceanographic Variations in Sediment from
the Korea Plateau, East Sea (Japan Sea), Over the Last 500 kyr-
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Abstract: Abstract High-resolution geochemical measurements were performed on core E09-08, which was taken from the top flat area of the Korea Plateau in the East Sea (Japan Sea). Based on analyses of sedimentary lamination, high-resolution oxygen isotopes, alkenone sea surface temperature (SST) variations, and comparison with previous results from the eastern part of the East Sea, a detailed multi-proxy-based stratigraphy was reconstructed. The results demonstrated that the core bottom dates approximately 500 kyr in the late marine isotope stage (MIS) 13, and provides high-resolution data on the paleoceanographic regime in the study area. Biogenic components of total organic carbon (TOC), carbon and nitrogen isotopes of organic matter (δ13Corg and δ15Norg), and alkenone concentrations indicate a paleoceanographic regime shift within the last 500 kyr. The excursion of proxies of δ18O, δ13Corg and δ15Norg and alkenone-based SST indicate two modes of oceanographic conditions: strong negative coupled mode (SNCM) during MIS 2, 10, and 12, and normal oceanographic decoupled mode (NODM) during other MIS. These two modes were interpreted as the terrestrial organic matter source domain and high-productivity oceanographic domain, respectively. The SNCM is characterized by relatively low δ13Corg and δ15Norg, and a high C/N ratio (> 12), whereas the NODM is characterized by relatively high δ13Corg and high δ15Norg, implying that larger amounts of terrestrial material were supplied during MIS 2, 10 and 12, with enhanced productivity during other MIS. The SNCM and NODM mode are also strongly associated with eustatic sea-level changes. The δ13Corg and δ15Norg values and alkenone-based SST excursions over glacial-interglacial periods were generally consistent with global-scale paleoclimate variation, as well as local paleoclimate. This study employed multi-proxy-based stratigraphy to demonstrate dramatic oceanographic variations since MIS 13, indicating that the local oceanographic setting was superimposed on global glacial-interglacial variations.
PubDate: 2022-06-14
- Seasonal Growth Dynamics of Posidonia oceanica in a Pristine Mediterranean
Gulf-
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Abstract: Abstract Seasonal growth dynamics and ecology of Posidonia oceanica were studied in a space alongshore a pristine Mediterranean gulf in 2011–2012. About one-third of the present study surface area was occupied meadows where only calcite rocks were found on bottoms between 0.5 and 29 m. Shoot density was not significantly different among seasons, and was above 364 ± 27 shoots m−2, but was different among the depths. The density variables decreased along the bottom depth gradient along which the number of leaves per shoot, inter shoot distance and the morphometrical variables tended to increase. Inferring the dynamics of biometrics (length and width of leaf, orthotropic rhizomes and leaf sheath) and density (LAI, leaf biomass and the number of leaves per shoot), the biometrics of the meadow grew seasonally between growth by March and mortality by August–September, regardless of the coverage area. Mortality occurred due to the highest annual salinity in late summer. A transition depth in space and month in time was assessed as 15 m and as August for variation of the biometrics, respectively. Rhizome related-biometrics (length, thickness, weight, sheath length and width) were dynamically initialized mainly by water nitrogen content which was high by winter-spring. A PAR in the range of 10–32%, and surface water temperature up to 28.8–29.3 °C corresponding to up to ~ 40 PSU were critical limiting factors for P. oceanica to survive in space. Water physics, chemistry, and optical properties governed the annual course of biometrics. Total organic carbon was also negatively affecting the seasonal dynamics of the rhizome.
PubDate: 2022-06-13
- New Opportunities in Global Ocean Research for Academia and Industry
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Abstract: Abstract Since 2017, requesting ship time has become possible for university researchers and businesses on research vessels. They include Isabu and Onnuri of the Korea Institute of Ocean Science and Technology (KIOST) and the icebreaking research vessel Araon of the Korea Polar Research Institute (KOPRI). There was no regulation barring the chartering of the significant national scientific infrastructure in the first place, but the exorbitant cost of ship time had made their usage virtually impossible. Shared Use Committee (SUC) was set up to handle applications and coordinate the cruises. A modest amount of research funds is also granted. Currently, the KIOST vessels conduct surveys in the Pacific and the central Indian Ocean annually. The KOPRI vessel routinely operates around Antarctica during the austral summer and in the Arctic seas during the boreal summer. Other government-supported institutions are likely to follow this shared used example. Here I provide a brief historical background leading to the shared use of research and information for potential applicants. The description is given from the perspective of geological oceanography, and thus some accounts may differ in other fields of study. A case study is given where a team of international university scientists successfully conducted a joint experiment to investigate the upper mantle structure by deploying ocean bottom instruments and recovering them one year later in the Pacific using Korean research vessels. Finally, some long and short-term recommendations are made to improve the system further.
PubDate: 2022-06-10
- Suppressed Upwelling Events in the Seychelles–Chagos Thermocline Ridge
of the Southwestern Tropical Indian Ocean-
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Abstract: Abstract A prominent subsurface upwelling over the Seychelles–Chagos Thermocline Ridge (SCTR) in the southwestern tropical Indian Ocean is suppressed when downwelling Rossby waves propagate from the eastern Indian Ocean during the positive phase of the Indian Ocean Dipole (IOD) or El Niño periods. Recent studies have suggested that the upwelling can be further suppressed during the co-occurrence years of positive IOD and El Niño, associated with the strong easterly wind anomalies in the eastern Indian Ocean. This study examines the temporal variations in the SCTR upwelling strength during 1968–2017, identifies strong upwelling suppression events, and analyzes their characteristics by focusing on the role of both remote and local wind forcing, not limited to the remote influence linked to the IOD and the El Niño Southern Oscillation. A total of nine events were identified for the 50-year period, with seven of them occurring 3–6 months after the co-occurring peaks of positive IOD and El Niño in the eastern Indian Ocean. However, only IOD exhibited a positive phase before the 2011–2012 suppression event associated with the downwelling-favorable anticlockwise local wind anomalies in the SCTR. Moreover, the 1978–1979 suppression event was primarily caused by the strong anticlockwise wind anomalies in the SCTR, without any significant influence of the positive IOD or El Niño. The results suggest that the role of local winds, as well as the remote forcing, are significant in the upwelling suppression over the SCTR, which would contribute to understanding the potential predictability of the upwelling variations.
PubDate: 2022-06-09
- Current Structure and Volume Transport in the Jeju Strait Observed for a
Year with Multiple ADCP Moorings-
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Abstract: Abstract The seasonal and spatial variation of the current structure and volume transport across the Jeju Strait (JS) is described based on an analysis of the data from five bottom mounted acoustic Doppler current profilers from February 13, 2020 to February 23, 2021. The current was weak and the mixed layer was well developed in winter, so the vertical current shear was not large. Whereas in summer, the inflow of high-temperature and low-salinity surface water built up the stratification, and the surface current velocity increased, resulting in a large vertical current shear. One salient feature to be found was that a westward flowing counter current in the lower layer appeared from June to December near the bottom trough of the JS. We named this seasonal counter current in the lower layer the Jeju Strait Under Current. The eastward net volume transport passing through the JS was large in summer–autumn and small in winter-spring, but did not follow a simple sinusoidal pattern. The annual mean net volume transport was 0.48 Sv (Sv ≡ 106 m3 s−1), with a minimum (0.27 Sv) in December and a maximum (0.79 Sv) in October 2020. When there were strong northerly winds in winter, a net volume transport to the west was temporarily caused by Ekman transport, but the direction reverted to the east as soon as the northerly winds lessened. When there were strong northwesterly (southeasterly) winds due to typhoons, the volume transport decreased (increased) sharply and then recovered rapidly.
PubDate: 2022-06-08
- Influence of Sea Surface Fluctuation on Internal Waves’ Vertical
Structures in a Two-Layer Model-
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Abstract: Abstract Using a two-layer linear ocean wave model that is quasi-incompressible and two-dimensional, we studied the relationships between surface fluctuation and ocean internal waves (IWs). The main conclusions were as follows. In a two-layer ocean, the analytical solution of IW was obtained by solving a homogeneous ordinary differential equation with constant coefficients according to the frequency, wave number (wavelength), and vertical velocity amplitude of the ocean surface fluctuation. The vertical structure and characteristics of IW in the ocean were analyzed under the conditions of different stratification parameters and background currents. Once the surface fluctuations were determined, the features of IW showed different shapes, which indicated the indeterminacy of the solution. Such indeterminacy reflects the characteristics of the inverse problem. To obtain a definite solution, the constraint conditions of the inverse problem should be provided—that is, the environmental parameters of the two layers, such as the background flow, stratification parameters, thickness of the two layers, and geostrophic parameters. If the environmental parameters are fixed, four situations of solutions can be determined. The first three solutions have IWs, and the fourth solution only has an external wave. For certain environmental parameters, the wave number and natural frequency (characteristic frequency) of the first three situations of IWs were determined in this study. We showed that a resonance phenomenon will occur and cause very severe ocean internal waves when the wave number and frequency of the surface fluctuation are analogous or equivalent to the natural wave number and natural frequency.
PubDate: 2022-05-31
- Abandoned, Lost and Discarded Fishing Gear from the Fishing Sector of
Kerala, India-
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Abstract: Abstract Abandoned, lost or otherwise discarded fishing gear (ALDFG) is rapidly becoming a major global environmental problem. In the present study, a survey of 390 fishermen operating ten different types of fishing gear was conducted, to get a quantitative estimate of ALDFG generated in the fishing intense coastal state of India (Kerala). On average, the total gear loss from 10 selected marine fishing gears operated in Kerala was estimated to be 167.5 ± 251.7 kg.vessel−1 year−1. Fishing crews reported that each year, 11.6% of the total gear used is lost, 7.5% is abandoned, and 2.3% is discarded. There was significant variation in the ALDFG incurred regarding different types of fishing gears. Motorized large mesh ring seine recorded the highest gear loss (35.5%), followed by motorized small mesh ring seine (29.7%), mini trawl (27.4%), trammel net (24.4%), motorized gillnet (18.75%), non-motorized gillnet (16.3%), small trawl (14.6%), large trawl (12.07%), medium trawl (11.25%) and shore seine (0.32%). The ALDFG estimates and associated trends worked out in the current study can assist filling in data gaps about fishing gear loss and aid in the design of strategies to manage marine debris from the fishing industry.
PubDate: 2022-05-31
- Dissolved Pb Concentrations and Stable Pb Isotope Ratios in the Ulleung
Basin, East/Japan Sea-
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Abstract: Abstract The spatial distributions of dissolved lead (Pb) concentrations and stable Pb isotope ratios in the Ulleung Basin, East/Japan Sea, were investigated to identify the Pb source, the behavior of Pb in seawater, and the relationship between Pb isotopes and water masses. The Pb concentrations showed a surface maximum and rapidly decreased with increasing water depth. In the slope area, Pb concentrations increased near the seafloor due to diffusive flux from the sediments. The Pb concentrations in the surface layer were higher than in the Northwest Pacific Ocean and western Philippine Sea due to the proximity and downwind location of the sampling site from a Pb source area. The bottom Pb concentrations were lower in the study area than in the open ocean, indicating a higher scavenging rate due to the presence of well-developed bottom boundary layers from the continental slope to the basin. The Pb isotope ratios obtained from the continental slope and basin area were relatively constant among water masses. The Pb isotope ratios in the surface layer were similar to those of coal from northern China, which may indicate Pb supply from coal combustion in China. Meanwhile, Pb in the bottom water had a similar isotopic signature to Russian ore deposits and coal, indicating that bottom Pb is associated with thermohaline circulation in the East/Japan Sea. The Pb isotope ratios of the intermediate layer were constant across the depths of East Sea Central Water (ESCW) and were similar to aerosols measured previously (in 2003–2004) around Ulleung Island, which may indicate the timing of ESCW formation.
PubDate: 2022-05-31
- The First Recorded Occurrences and the Distribution of Physalia physalis
(Hydrozoa: Physaliidae) in Algerian Waters-
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Abstract: Abstract Recently, there have been recorded findings of the pleustonic siphonophore Physalia physalis Linnæus, 1758, in different regions of Algeria. Several colonies washed ashore during March and May 2021 along the Algerian coast. Thirty colonies were observed on surface water and stranded on the beach between March and May from Beni Saf (35.30182° N;-1.40293° W) to Skikda (36.916557° N;7.162915° E). The highest number of such strandings of this species was recorded in Tipaza and Algiers. This is the first record of P. physalis in Algeria, extending the previously known distributions from the tropical and sub-tropical latitudes of Atlantic, Pacific and Indian oceans and may represent a danger to human health and the coastal economy. Strandings of P. physalis were notably associated with sea surface current and wind forces pushing P. physalis to become stranded on beaches. Our findings highlight the need for a monitoring program to be developed to understand more about trends associated with changes in the distribution and impact of this species. This work provides an update on the spatial distribution of P. physalis in the Mediterranean Sea.
PubDate: 2022-05-25
- Unusual Mass Appearance of Salpa fusiformis (Thaliacea: Salpida) in Early
Spring at a Nuclear Power Plant at Mid-western Boundary of the East Sea-
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Abstract: Abstract In the spring of 2021, a large number of Salpa fusiformis suddenly appeared along the east coast of the Korean Peninsula and invaded a nuclear power plant (NPP) in large numbers. To understand the mechanisms and causes of the mass appearance and intrusion of S. fusiformis, field surveys were undertaken and collected observational data such as temperature, salinity, and ocean currents, and wind data were tabulated and analyzed. Field surveys in the offshore area of the NPP revealed that warm, saline, and less-oxygenated water flowed northward at approximately 25 km from the coastline, and that this water mass was that of the East Korean Warm Current (EKWC), with aggregated individuals (blastozooids) dominating the population of S. fusiformis. In the EKWC region, S. fusiformis were more abundant in the coastal area than in the center of the EKWC. Sea surface temperature and surface currents from satellite data showed that a thermal front was formed between the EKWC and the cold coastal waters off the NPP. The main path of the EKWC was close to the coast, and on days when S. fusiformis invaded the NPP in large numbers, the wind direction near the NPP was west-northwest. We suggest that large-scale invasions of the NPP by S. fusiformis can be predicted by incorporating appropriate field survey data into a particle tracking model that considers the direction and speed of the EKWC, the abundance of S. fusiformis in the EKWC, the location of thermal fronts, and wind direction and speed.
PubDate: 2022-05-25
- Status, Biodiversity, and Ecosystem Services of Seagrass Habitats Within
the Coral Triangle in the Western Pacific Ocean-
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Abstract: Abstract Area of the Coral Triangle (CT), namely Indonesia, Malaysia, Papua New Guinea, Philippines, Solomon Islands, and Timor-Leste, comprises 5.7 million km2 of the Pacific Ocean. It is one of the most bio-diverse marine eco-regions on the planet, as well as a global hotspot for seagrass species. Many sea creatures of this eco-region rely on the seagrass ecosystem, especially dugong species extensively (a total number of 2279 individuals), sea turtles (4–6 species), benthic organisms, and fish. Apart from these ecological services, carbon sequestration (2.6 billion Mg CO2 storage) by the seagrass ecosystem is considerably higher in comparison to terrestrial vegetation. In this paper, we scrutinized previously acknowledged seagrass species distribution, the associated fauna in seagrass meadows, the total carbon sequestration in the Coral Triangle, past and present research conducted on seagrass and other aspects, and major threats to seagrass ecosystems within this biogeographic region. Depending on their different locations, the six CT countries have a minimum of 10 to a maximum of 19 seagrass species that belong to four distinct families (Hydrocharitaceae, Cymodoceaceae, Zosteraceae, and Ruppiaceae) and cover almost 58,550.63 km2. While a total of 21 species of seagrass have been found throughout this eco-region, very little research has been conducted to assess the overall status of the ecosystems within this eco-region. Seagrass ecosystems and services from these habitats within the Coral Triangle are also associated with 100 million human inhabitants, who are supported directly or indirectly by the resources of this ecosystem. These inhabitants may cause considerable disturbance to seagrass ecosystems. For the long-term sustainable management and conservation of these ecosystems, two types of threats, namely local human activities and global transboundary issues including climate change, have been identified and need to be taken into consideration. In terms of human activities, local threats include water quality deterioration due to sewage and pollutant discharge, agricultural activities mainly from palm oil plantations, over-exploitation of seagrass-associated resources, sediment runoff, and destructive fishing practices. Global threats comprise macro and microplastics, sea-level rise due to climate change, global warming, and acidification. Further study of social, cultural, and economic interaction between the local inhabitants and seagrass ecosystems is highly recommended for assessing the ecological and economic contribution of this habitat to the human societies of the Coral Triangle. Despite their importance for human food services and the maintenance of the food web for marine and coastal animals, human activities have a negative impact on seagrass ecosystems around the world, particularly in the Coral Triangle.
PubDate: 2022-05-20
- Evolution and Sedimentation Mechanisms of Estuarine Beach in the Nakdong
River Estuary, Korea: Natural and Human Impact-
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Abstract: Abstract Dadae Beach located in the Nakdong River estuary has been continuously evolving as the result of natural and anthropogenetic activities. Due to the geographic characteristics of an estuarine beach, in which the estuary, ocean, and human activities converge, it is very difficult to identify the factors shaping changes in the sedimentary environment and present quantitative results. Nevertheless, this study presents a survey of hydrological characteristics that reveals major depositional mechanisms and the factors impacting the sedimentary environment by analyzing morphological variations over the last five decades. We found that Dadae Beach has transformed from a marine system to an estuarine system through three major stages of evolution over the last five decades and has now reached a quasi-equilibrium state. The depositional mechanism contributing to the deposition of Dadae Beach is mainly driven by rainfall during the wet season. In addition, the strengthening of ocean energy during the dry season causes erosion. By proposing a new evolutionary history of Dadae Beach which had previously been considered a byproduct of the barrier island generation process of the Nakdong River, we suggest a novel conceptual model for estuarine beach evolution.
PubDate: 2022-05-12
- Application of a Length-Based Stock Assessment Model for the Chub Mackerel
(Scomber japonicus) in Korean Waters-
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Abstract: Abstract We modified Quinn’s size-based model for the assessment of chub mackerel (Scomber japonicus) stock in Korean waters, using annual data about body lengths (fork lengths), fishery catches, and catch-per-unit-effort. One of the strengths of Quinn’s size-based model is the construction of an imaginary age structure for a fish population, allowing the estimation of year- and age-based population sizes. Our modification was twofold. First, we applied a likelihood theory for numerical optimization, instead of the least squares method that Quinn et al. (1998) used. Second, we not only made point estimates of parameters, but also measured their uncertainties, using ADMB (automatic differentiation model builder) software. Estimates of annual biomass from 2001 to 2017 ranged from 1.01 × 106 to 2.15 × 106 MT, and estimates of annual fishing mortality from 1996 to 2017 ranged from 0.11 to 0.32 per year. Using a sensitivity analysis, we obtained the natural mortality of the stock, which was 0.1 per year.
PubDate: 2022-05-09
- Effect of Different pCO2 Concentrations in Seawater on Meiofauna:
Abundance of Communities in Sediment and Survival Rate of Harpacticoid
Copepods-
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Abstract: Abstract The amount of CO2 dissolved in the ocean has been increasing continuously, and the results using climate change models show that the CO2 concentration of the ocean will increase by over 1000 ppm by 2100. Ocean acidification is expected to have a considerable impact on marine ecosystems. To find out about the impacts of ocean acidification on meiofaunal communities and copepod groups, we analyzed the differences in the abundance of meiofauna communities in sediment and the survival rate of harpacticoid copepod assemblages separated from the sediment, between 400 and 1000 ppm pCO2 for a short period of 5 days. In experiments with communities in sediments exposed to different pCO2 concentrations, there was no significant difference in the abundance of total meiofauna and nematodes. However, the abundance of the harpacticoid copepod community was significantly lower at 1000 ppm than that at 400 ppm pCO2. On the other hand, in experiments with assemblages of harpacticoid copepods directly exposed to seawater, there was no significant difference in their survival rates between the two concentrations. Our findings suggest that a CO2 concentration of 1000 ppm in seawater can cause changes in the abundance of specific taxa such as harpacticoid copepods among the meiofauna communities in sediments.
PubDate: 2022-05-06
- Optimized Metavirome Analysis of Marine DNA Virus Communities for
Taxonomic Profiling-
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Abstract: Abstract Recent advances in metavirome technology have provided new insights into viral diversity and function. The bioinformatic process of metavirome study is generally divided into two (or three) steps: assembly and taxonomic profiling including nucleotide alignment. Moreover, k-mer size and contig length are known to considerably affect the results of the assembly and consequently those of taxonomic profiling; however, the optimal k-mer size and contig length have not been established. In the present study, we analyzed marine virus DNA datasets with three different k-mer sizes using different assemblers: 1 k-mer (20) in the CLC Genomics Workbench, and 4 (21, 33, 55, and 77) and 5 (21, 33, 55, 77, and 99) k-mers in metaSPAdes. The use of large k-mers had the advantage of resolving more repeat regions, with higher N50 values and average contig lengths. The contig length helps reduce the error of continuous sequences and determine the number of viral operational taxonomic units. Our analysis suggested that 300 bp may be an appropriate minimum contig length, depending on the characteristics of viral samples. Based on the assembly result using metaSPAdes, we analyzed the DNA virus community using three taxonomic profiling tools: MG-RAST online server, the taxonomic profiling tools function in the CLC microbial module, and customized taxonomic assignment coding (CUTAXAC) using RStudio based on the BLASTn analysis. CUTAXAC showed the most diverse viral composition at the family and species levels along with the highest Shannon diversity index and fastest analysis time.
PubDate: 2022-05-02
- Decadal Variability of Satellite-Derived Air–Sea CO2 Flux in
Southwestern Part of the Bay of Bengal-
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Abstract: Abstract Understanding the relationship between atmospheric and oceanic carbon cycles necessitates measuring geographical and temporal variations of surface water partial pressure of carbon dioxide (pCO2). The seasonal pCO2 maps have been developed using MODIS-derived SST and chlorophyll for four different seasons to calculate air–sea flux of CO2 at basin scale. Summer in 2017 had the lowest pCO2 value (263 µatm), whereas monsoon season in 2016 had the highest (553 µatm). From 2010 to 2019, atmospheric pCO2 level fluctuated from 371 to 396 µatm with progressive growth of atmospheric pCO2 at 2.5 μatm year−1. The inter-annual CO2 flux ranged between − 3.58 and 3.64 mmol C m−2 day−1. Significant negative CO2 flux (− 3.58 mmol C m−2 day−1) was observed in 2015 premonsoon, indicating that the Bay of Bengal was a net sink for atmospheric CO2, while served as a net source of CO2 to the atmosphere in 2013 monsoon season with a significant positive flux of CO2 (3.64 mmol C m−2 day−1) to the atmosphere. The annual CO2 sink was active in 2015 (− 1.17 mmol C m−2 day−1) which showed increased trend from 2014 to 2018 with a range of − 1.17 to − 0.26 mmol C m−2 day−1. The Bay of Bengal was found to be a substantial CO2 contributor to the atmosphere in 2013 (3.64 mmol C m−2 day−1) and 2012 (3.27 mmol C m−2 day−1). In this context, the southwest Bay of Bengal serves as a net sink of atmospheric pCO2 during summer season on an annual scale, and a weak sink during postmonsoon and premonsoon seasons, while served as a strong source of CO2 to the atmosphere during monsoon season from 2010 to 2019 with super saturation of CO2.
PubDate: 2022-04-27
- Microstructure of Antarctic Krill (Euphausia suberba) Cuticle
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Abstract: Abstract In this study, the microstructure of Antarctic krill cuticle was deeply investigated using scanning electron microscope (SEM). The krill cuticles were treated with clean water, dilute hydrochloric acid solution and dilute sodium hydroxide solution to remove the adhesive substances, inorganic salts and protein, respectively. The organic substances were removed by sintering the cuticle in a muffle furnace to obtain the inorganic salts. The resulting cuticle of Antarctic krill was then observed under SEM and it was found that the cuticle has a hierarchical structure in which the α-crystal chitin fibers, with chitin spheres, extended from the pore canals, thus shaping layers; multiple stacked layers formed the three-dimensional structure; the inorganic salts were sparsely distributed in the cuticle; protein was wrapped around the surfaces of the chitin fiber bundles and the crystals of inorganic salts. These structural investigations revealed the interrelation among the main components of Antarctic krill cuticle. This study and following studies will be helpful in understanding the relationship between the forms of fluorine in Antarctic krill cuticle and its structural changes during postmortem storage.
PubDate: 2022-04-13
DOI: 10.1007/s12601-022-00059-x
- Temporal Variations in the Antifouling Activity of Extract of the Soft
Coral Sarcophyton trocheliophorum Collected from the Red Sea-
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Abstract: Abstract Soft corals are considered as a prospective resource for the isolation of natural product antifoulants. In this study, the temporal variations in the antifouling activity of the crude extract of the soft coral Sarcophyton trocheliophorum samples collected from the Jeddah coast of Saudi Arabia during summer (June–August 2018) and winter seasons (December 2018–February 2019) were assessed using laboratory tests. The crude extract was tested against biofilm-forming bacteria and barnacle larvae in the laboratory. The results indicated significant variations (P < 0.001) in the antifouling activity of the extracts between the samples collected during the summer and winter seasons. The extract of the soft coral samples collected during the summer season showed higher inhibitory activity against the fouling bacteria and barnacle larva. In addition, the surface-associated bacteria abundance on the soft corals were analysed and the results showed higher abundance on winter season samples. Further, GC–MS analysis indicated differences in the metabolite composition with the abundance of compounds such as cis-z-a-Bisabolene epoxide and caryophyllene oxide being high in summer samples and Isoaromadendrene epoxide and β-cembrenediol showing a higher peak area percentage in winter samples. Overall, this study revealed temporal variations in the antifouling activity and metabolite composition of the Red Sea soft corals.
PubDate: 2022-03-16
DOI: 10.1007/s12601-022-00062-2
- Calibration of the XRF-Estimated CaCO3 Content in the Western Tropical
Pacific Deep-Sea Sediments-
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Abstract: Abstract X-ray fluorescence (XRF) scanning, which can be used for the rapid, high-resolution measurement of elements in marine sediments, is advantageous because multiple elements can be simultaneously analysed. However, the use of XRF scan data as quantitative data has limitations. The XRF scanning measures element intensities (cps) of sediments instead of element contents (wt%). In addition, the element intensities are influenced by physical properties, such as water content and lithification. The objective of this study is to establish a calibration method for quantifying the CaCO3 content from XRF Ca data based on comparisons between XRF Ca and inorganic carbon measured CaCO3 contents.
PubDate: 2022-03-16
DOI: 10.1007/s12601-022-00061-3
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