JournalTOCs

Frontiers in Marine Science
Journal Prestige (SJR): 1.225

Citation Impact (citeScore): 3
Number of Followers: 17

This is an Open Access Journal

Open Access journal
ISSN (Online) 2296-7745
Published by Frontiers Media

[96 journals]

Fisherwomen’s Indigenous and local knowledge - the hidden gems for the
management of marine and freshwater resources in Fiji
- Authors: Salanieta Kitolelei, Annette Breckwoldt, Jokim Kitolelei, Natalie Makhoul
  Abstract: Fisherwomen in Fiji play a vital role in the daily sustenance of their families and they use their Indigenous and local knowledge to harvest resources. Marine and freshwater resources harvested by fisherwomen contribute to the primary protein intake of their families, particularly for those who have limited or no access to other animal products or plant proteins. Over a span of three decades, Fiji experienced an influx in the documentation of women’s contribution and need for fisherwomen's recognition in the fisheries sector; in areas of cultural and/or socio-economic, resource management and decision-making processes. This study examines the Indigenous and local knowledge which fisherwomen utilize to identify their targeted marine and freshwater resources and gauge the population health of their resources. Furthermore, fisherwomen’s perceptions on the conservation status of their resources is used to provide the basis for improved management of culturally, economically and ecologically valuable species. The results of this study compiles Indigenous taxonomic classifications and associated species knowledge which fisherwomen from 11 communities use to help them in identifying and capturing resources. Moreover, the fishing methods, ecological knowledge and perceptions on environmental changes over thirty years provides temporal background on the fisherwomen’s knowledge. The results address knowledge gap between fisherwomen's Indigenous and local knowledge and science by marrying the well-developed knowledge systems. Finally, this study provides recommendations on how the Indigenous and local knowledge of women can contribute to practical and efficient resource management for localized challenges in Fiji.
  PubDate: 2022-12-05T00:00:00Z
Environmental DNA: State-of-the-art of its application for fisheries
assessment in marine environments
- Authors: Sergio Ramírez-Amaro, Marta Bassitta, Antònia Picornell, Cori Ramon, Bàrbara Terrasa
  Abstract: Fisheries management involves a broad and complex set of tasks that are necessary to prevent overfishing and to help the recovery of overfished stock. Monitoring fishing activities based on two main sources, landings data and scientific surveys, is a challenging task. Fisheries collection data is often limited, which compromises the accuracy of the results obtained. Therefore, several emerging applications of molecular methods have the potential to provide unique understanding of ecological processes in marine environments and to build stronger empirical underpinnings for the Ecosystem-Based Fisheries Management. Environmental DNA (eDNA) is a complex mixture of genetic material shed by those organisms that inhabit a given environment, whereby DNA is extracted from an environmental sample without accessing the target organism. eDNA studies can be categorized into two main approaches, i) eDNA metabarcoding or semi-targeted (community) approaches and ii) species-specific or targeted approaches (single). Although both categories are often discussed, they differ drastically in their methodology, interpretations and accuracy. Both approaches involve a series of steps that include eDNA capture, preservation, extraction and amplification. This detection will depend on the affinity to the targeted taxa sequences and completeness and accuracy of DNA reference collection databases. The eDNA method applied in marine environments are probably the most challenging aquatic environments for applying this technique. This is because of the extreme relationship between water-volume to biomass, dynamics and the physical and chemical properties of seawater that affect dispersion, dilution and preservation. Here, we review the present application of this novel method in fishery assessment in marine environments. To date, many studies suggest that this method offers the potential to revolutionize fisheries monitoring, which will contribute to improving the range of tasks involved in fisheries management. The compelling conclusion is that the methodological steps including in eDNA surveys should be standardized and that research efforts should focus on developing appropriately validated tests to address environmental and sampling factors that may affect eDNA detection in marine environments in order to draw reliable conclusions. This bioassessment tool can assist fisheries professionals in achieve their research, management, and conservation objectives, but not as a replacement for time-proven assessment methods.
  PubDate: 2022-12-05T00:00:00Z
Analysis and prediction of marine heatwaves in the Western North Pacific
and Chinese coastal region
- Authors: Yifei Yang, Wenjin Sun, Jingsong Yang, Kenny T. C. Lim Kam Sian, Jinlin Ji, Changming Dong
  Abstract: Over the past decade, marine heatwaves (MHWs) research has been conducted in almost all of the world’s oceans, and their catastrophic effects on the marine environment have gradually been recognized. Using the second version of the Optimal Interpolated Sea Surface Temperature analysis data (OISSTV2) from 1982 to 2014, this study analyzes six MHWs characteristics in the Western North Pacific and Chinese Coastal region (WNPCC, 100°E ∼ 180°E, 0° ∼ 65°N). MHWs occur in most WNPCC areas, with an average frequency, duration, days, cumulative intensity, maximum intensity, and mean intensity of 1.95 ± 0.21 times/year, 11.38 ± 1.97 days, 22.06 ± 3.84 days, 18.06 ± 7.67 °Cdays, 1.84 ± 0.50°C, and 1.49 ± 0.42 °C, respectively, in the historical period (1982 ~ 2014). Comparing the historical simulation results of 19 models of the Coupled Model Intercomparison Project Phase 6 (CMIP6) with the OISSTV2 observations, five best-performing models (GFDL-CM4, GFDL-ESM4, AWI-CM-1-1-MR, EC-Earth3-Veg, and EC-Earth3) are selected for MHWs projection (2015 ~ 2100). The MHWs characteristics projections from these five models are analyzed in detail under the Shared Socio-economic Pathway (SSP) 1-2.6, 2-4.5 and 5-8.5 scenarios. The projected MHWs characteristics under SSP5-8.5 are more considerable than those under SSP1-2.6 and 2-4.5, except for the MHWs frequency. The MHWs cumulative intensity is 96.36 ± 56.30, 175.44 ± 92.62, and 385.22 ± 168.00 °Cdays under SSP1-2.6, 2-4.5 and 5-8.5 scenarios, respectively. This suggests that different emission scenarios have a crucial impact on MHW variations. Each MHWs characteristic has an obvious increasing trend except for the annual occurrences. The increase rate of MHWs cumulative intensity for these three scenarios is 1.02 ± 0.83, 3.83 ± 1.43, and 6.70 ± 2.61 °Cdays/year, respectively. The MHWs occurrence area in summer is slightly smaller than in winter, but the MHWs average intensity is stronger in summer than in winter.
  PubDate: 2022-12-05T00:00:00Z
High-quality chromosome-level genome assembly of Pacific cod, Gadus
macrocephalus
- Authors: Yiqing Ma, Yuan Li, Chen Jiang, Li Zheng, Shenghao Liu, Linlin Zhao
  PubDate: 2022-12-05T00:00:00Z
Assessment of underwater navigation safety based on dynamic Bayesian
network facing uncertain knowledge and various information
- Authors: Ming Li, Ren Zhang, Xi Chen, Kefeng Liu
  Abstract: As ocean environment is complicated and varied, underwater vehicles (UVs) are facing great challenges in safe and precise navigation. Therefore, it is important to evaluate the underwater ocean environment safety for the UV navigation. To deal with the uncertain knowledge and various information in the safety assessment, we present an evaluation model based on the dynamic Bayesian network (DBN) theory. Firstly, characteristic indicators are extract from marine environment systems and discretized with Cloud model. Then, the DBN is constructed through structure learning and parameter learning based on Dempster-Shafer (DS) evidence theory. Finally, the dynamic evaluation and risk zoning of the navigation safety is realized based on Bayesian probabilistic reasoning. The DBN-based assessment model fully considers the uncertainty of influence relationships between marine environment and UV navigation, and effectively fuses expert knowledge and quantitative data for assessment modeling. The experimental results show the proposed model has high reliability and good value of application.
  PubDate: 2022-12-05T00:00:00Z
Confocal Raman microscopy for assessing effects of preservation methods on
symbiotic deep-sea mussel gills
- Authors: Wanying He, Minxiao Wang, Mengna Li, Zhaoshan Zhong, Hao Chen, Shichuan Xi, Zhendong Luan, Chaolun Li, Xin Zhang
  Abstract: Confocal Raman microscopy (CRM) is a powerful tool for biological research, which can provide information regarding the composition and distribution of biomolecules in an in situ, label-free, non-destructive manner and with high spatial resolution. Sample preservation is often an unavoidable step, especially for symbiotic deep-sea samples. Moreover, protocols for the preservation of samples for CRM have not been established and specific effects of different preservation methods on biomolecules have not been studied for relevant samples. In this study, we used deep-sea mussel Gigantidas platifrons, an ideal model in the study of deep-sea symbiosis and investigated the effect of four common preservation methods on the results of CRM imaging and signals. The methods included snap-freeze (SF), SF followed by rapid fixation in methanol (SF-MeOH), 2.5% glutaraldehyde and 2% paraformaldehyde fixation (SF-GP), and 4% paraformaldehyde and alcohol fixation (PS-PA). The results of this study indicate that SF was the most effective method for the comprehensive analysis of the biomolecular composition although the sectioning success rate was relatively low. Moreover, SF-MeOH was found to be effective when SF is not sufficient in obtaining good morphology in sections, or when the effect of chemical bonding on the composition of biomolecules upon SF-MeOH can be neglected. Finally, SF-GP and PS-PA were found to be the most effective methods considering the overall morphological observation. However, they were less suitable for metabolic studies. We believe our results can provide guidance for further studies of Raman on symbiotic deep-sea biological samples. It is of great importance for the wide application of Raman technique.
  PubDate: 2022-12-05T00:00:00Z
Effects of Bacillus sp. and Lactobacillus sp. combination as a water
additive on the culture pond water and growth performance of hybrid
grouper (Epinephelus fuscoguttatus × Epinephelus polyphekadion)
- Authors: Jianpeng Huang, Eric Amenyogbe, Guanghai Ou, Yu Li, Zhenwei Wen, Xingtao Jiang, Gang Chen
  Abstract: The individual Probiotic application has become increasingly widespread in aquaculture and has been extensively studied. However, investigating probiotics as water additives in the grouper culture is still lacking. This study evaluated the functional efficacy of the Bacillus subtilis CICC 10071 (3 × 1011 CFU / g) and Lactobacillus sp. (8 × 1011 CFU / g) combination in a 1:1 ratio on the rearing water quality, water microbial community structure, and growth performance of hybrid grouper. Depending on the additive concentrations of probiotics, we designed four groups, each in triplicate: control (WT, 0g/m3), low concentration (WL, 0.038g/m3), middle concentration (WM, 0.075g/m3), and high concentration (WH, 0.113g/m3). The result shows that throughout the 22-day feeding period, the water supplementation of probiotics significantly decreased Ammonia (NH3) and nitrite (NO2-) in culture water. Final weight (FW), Specific growth rate (SGR), and Weight gain rate (WGR) in treated groups were higher than that in the control group (P
  PubDate: 2022-12-02T00:00:00Z
Sensitivity analysis of seismic attributes and oil reservoir predictions
based on jointing wells and seismic data – A case study in the Taoerhe
Sag, China
- Authors: Na Li, Jinliang Zhang, Jun Matsushima, Cheng Song, Xuwei Luan, Ming Dou, Tao Chen, Lingling Wang
  Abstract: It is important to identify the location of gravelly sandstone in Taoerhe Sag, an oil target area in the Chezhen Depression. To date, most attention has focused on sedimentary characteristics; hence, information regarding a clear sensitivity analysis of seismic attributes is incomplete. To address this, we used well analysis and seismic attribute interpretation to find sensitive seismic attributes and sand bodies. Based on the well analysis and core data, a geologicald model of mudstone and sandstone was established, and the electrical characteristics of three kinds of lithology were identified. We used correlation analysis to select the optimal logging parameters and seismic attributes to identify sandstone. We used multi-attribute fusion technology and stratigraphic slices to characterize the spatial distribution characteristics of gravelly sandstone in the target area and used genetic algorithm inversion volume to evaluate the prediction results. The results indicate that the three main lithologies of the lower submember of Shahejie Formation 3 (P2S3X) in the Taoerhe Sag can be distinguished by natural gamma (GR), acoustic time difference (AC) and saturated hydrocarbon content (SH) logging curves. The seismic attribute characteristics of gravelly sandstone of P2S3X are high root mean square amplitude (RMS) values, high instantaneous bandwidth (BW) values, low 3D curvature (Curv) values, medium-high instantaneous phase (Phase) values and high instantaneous frequency (Freq) values. In this study, we found two nearshore underwater fans in P2S3X. Gravelly sandstone is located along the slope zone and the lake bottom, with a total sedimentary area of 57.9 km2. The method summarized in this paper can be applied to other similar deep-water basins.
  PubDate: 2022-12-02T00:00:00Z
Seasonal variability of eddy kinetic energy in the East Australian current
region
- Authors: Jia Liu, Shaojun Zheng, Ming Feng, Lingling Xie, Baoxin Feng, Peng Liang, Lei Wang, Lina Yang, Li Yan
  Abstract: The East Australian Current (EAC) is an important western boundary current of the South Pacific subtropical Circulation with high mesoscale eddy kinetic energy (EKE). Based on satellite altimeter observations and outputs from the eddy-resolving ocean general circulation model (OGCM) for the Earth Simulator (OFES), the seasonal variability of EKE and its associated dynamic mechanism in the EAC region are studied. High EKE is mainly concentrated in the shear-region between the poleward EAC southern extension and the equatorward EAC recirculation along Australia's east coast, which is confined within the upper ocean (0-300 m). EKE in this area exhibits obvious seasonal variation, strong in austral summer with maximum (465±89 cm² s-²) in February and weak in winter with minimum (334±48 cm² s-²) in August. Energetics analysis from OFES suggests that the seasonal variability of EKE is modulated by the mixed instabilities composed of barotropic and baroclinic instabilities confined within the upper ocean, and barotropic instability (baroclinic instability) is the main energy source of EKE in austral summer (winter). The barotropic process is mainly controlled by the zonal shear of meridional velocities of the EAC southern extension and the EAC recirculation. The poleward EAC southern extension and the equatorward EAC recirculation are synchronously strengthened (weakened) due to the local positive (negative) sea level anomalies (SLA) under geostrophic equilibrium, and the barotropic instability dominated by zonal shear is enhanced (slackened), which results in a high (low) level of EKE in the EAC region.
  PubDate: 2022-12-02T00:00:00Z
Two canonically aerobic foraminifera express distinct peroxisomal and
mitochondrial metabolisms
- Authors: Christopher Powers, Fatma Gomaa, Elizabeth B. Billings, Daniel R. Utter, David J. Beaudoin, Virginia P. Edgcomb, Colleen M. Hansel, Scott D. Wankel, Helena L. Filipsson, Ying Zhang, Joan M. Bernhard
  Abstract: Certain benthic foraminifera thrive in marine sediments with low or undetectable oxygen. Potential survival avenues used by these supposedly aerobic protists include fermentation and anaerobic respiration, although details on their adaptive mechanisms remain elusive. To better understand the metabolic versatility of foraminifera, we studied two benthic species that thrive in oxygen-depleted marine sediments. Here we detail, via transcriptomics and metatranscriptomics, differential gene expression of Nonionella stella and Bolivina argentea, collected from Santa Barbara Basin, California, USA, in response to varied oxygenation and chemical amendments. Organelle-specific metabolic reconstructions revealed these two species utilize adaptable mitochondrial and peroxisomal metabolism. N. stella, most abundant in anoxia and characterized by lack of food vacuoles and abundance of intracellular lipid droplets, was predicted to couple the putative peroxisomal beta-oxidation and glyoxylate cycle with a versatile electron transport system and a partial TCA cycle. In contrast, B. argentea, most abundant in hypoxia and contains food vacuoles, was predicted to utilize the putative peroxisomal gluconeogenesis and a full TCA cycle but lacks the expression of key beta-oxidation and glyoxylate cycle genes. These metabolic adaptations likely confer ecological success while encountering deoxygenation and expand our understanding of metabolic modifications and interactions between mitochondria and peroxisomes in protists.
  PubDate: 2022-12-02T00:00:00Z
Integrative proteomics and metabolomics reveal the stress response of
semicarbazide in the sea cucumber Apostichopus japonicus
- Authors: Lixin Lu, Lihua Ren, Lisheng Jiang, Xiaohui Xu, Weijun Wang, Yanwei Feng, Zan Li, Jianmin Yang, Guohua Sun
  Abstract: Semicarbazide (SMC), also known as carbamoyl hydrazide, is a key intermediate for the organic synthesis of drugs, pesticides, and a panoply of other applications. It is also regarded as a landmark metabolite of nitrofurazone, a banned veterinary drug. SMC produced in different ways will eventually enter the ocean and become an emerging marine pollutant, affecting the physiological metabolism, behavioral activities, and even survival of aquatic organisms. Sea cucumbers are sediment-feeding organisms, and their risk of exposure to pollutants has attracted increasing attention. In this study, an integrated proteomic and metabolomic approach was used to investigate the responses of Apostichopus japonicus treated with SMC (3.72 g/L) for 72 h. After SMC treatment, the proteins and metabolites of A. japonicus intestine changed significantly. The results showed that 342 differentially expressed proteins were identified, of which 174 were upregulated, 168 were downregulated, and 74 differentially expressed metabolites, of which 62 were upregulated and 12 were downregulated. These differential proteins and metabolites were primarily involved in energy metabolism, lipid metabolism, signal transduction, immune regulation, autophagy, and apoptosis. On the basis of a combination of proteomic and metabolomic data, a hypothetical network of proteins, metabolites, and pathways in sea cucumbers was also described; the resulting network indicated several significant biological activities in response to SMC. This work offers a thorough analysis of the intricate mechanisms by which sea cucumbers respond to SMC stress and indicates numerous possible indicators for further research on creatures exposed to SMC. Further, our results provide scientific guidance for pollution control of Apostichopus japonicus culture to ensure healthy breeding.
  PubDate: 2022-12-02T00:00:00Z
A three-dimensional experimental study on bank retreat: The coupled role
of seepage and surface flow
- Authors: Keyu Wang, Zheng Gong, Kun Zhao, Shuai Tang, Kaili Zhang
  Abstract: The coupled role of seepage and surface flow on bank retreat has long been neglected, partly due to the concealment and complexity of seepage erosion. To fill this gap, we set up a three-dimensional laboratory experiment to explore bank retreat process in response to seepage and surface flow. During each experiment, we measured the changes of total soil stress, matric suction, and water content within the bank, as well as flow velocity and suspended sediment concentration near the bank. Results show that a rapid decrease in matric suction, the bank toe undercutting consequent to seepage erosion, the formation of tension crack on the bank top, and the occurrence of toppling or shear failure is the typical sequence of the observed bank retreat process under seepage flow. The inclusion of surface flow erodes slump blocks and so promotes cantilever formation, leading to additional bank failure. Compared with the case where only seepage is considered, the frequency of toppling failure under the coupled effect of seepage and surface flow decreases, but the contribution to the bank retreat increases by 37 %. The time taken to collapse in three-dimensional experiments is at least 1.5 h earlier than that of two-dimensional experiments, indicating the importance of preferential flow pathways of seepage. Overall, this research illustrates how surface flow interacts with seepage flow to control bank retreat process and is indeed a first step toward a fully understanding of multifactor-driven bank retreat.
  PubDate: 2022-12-02T00:00:00Z
Differential responding patterns of the nirK-type and nirS-type
denitrifying bacterial communities to an Ulva prolifera green tide in
coastal Qingdao areas
- Authors: Guihua Zhao, Hui He, Ming Yue, Hualong Wang, Hongbing Shao, Min Wang
  Abstract: Coastal eutrophication may be a vital inducement of green tide. Denitrification is an important nitrogen removal pathway that involves a series of enzymatic reactions. The rate-limiting step in the conversion of nitrite to nitric oxide is encoded by two functionally equivalent but structurally distinct genes, copper-containing nitrite reductase gene (nirK) and cytochrome cd1-containing nitrite reductase gene (nirS). Here, we used Illumina Miseq sequencing approach to examine the variations in denitrifying bacterial community characteristics and interactions during an Ulva prolifera green tide in coastal Qingdao areas. Our findings suggested that the variations in the denitrifying bacterial community structure during the green tide were closely related to the changes of chlorophyll a content, salinity and dissolved oxygen content. The nirK-type denitrifying bacteria were more sensitive to green tide than the nirS-type denitrifying bacteria. Additionally, the nirK-type denitrifying bacterial interactions were more stable and complex during the outbreak phase, while the nirS-type denitrifying bacterial interactions were more stable and complex during the decline phase. All of these characters demonstrated that the nirK-type and nirS-type denitrifying bacteria respond differently to the green tide, implying that they may occupy different niches during the green tide in coastal Qingdao areas.
  PubDate: 2022-12-02T00:00:00Z
Transcriptional responses indicate acclimation to prolonged deoxygenation
in the coral Stylophora pistillata
- Authors: Hagit Kvitt, Assaf Malik, Smadar Ben-Tabou de-Leon, Eli Shemesh, Maya Lalzar, David F. Gruber, Hanna Rosenfeld, Tuo Shi, Tali Mass, Dan Tchernov
  Abstract: The current decrease in oceanic dissolved oxygen is a widespread and pressing problem that raises concern as to how marine biota in general, and coral reefs in particular will be affected. However, the molecular response underlying tolerance of corals to prolonged severe deoxygenation where acclimation to hypoxia can accrue is not yet known. Here, we investigated the effect of two weeks of continuous exposure to conditions of extreme deoxygenation, not hitherto exerted under laboratory conditions (~ 0.35 mg L−1 dissolved oxygen), on the physiology and the diurnal gene expression of the coral, Stylophora pistillata. Deoxygenation had no physiologically significant effect on tissue loss, calcification rates, symbiont numbers, symbiont chlorophyll-a content and symbiont photosynthesis rate. However, deoxygenation evoked a significant transcriptional response that was much stronger at night, showing an acute early response followed by acclimation after two weeks. Acclimation included increased mitochondria DNA copy numbers, possibly increasing energy production. Gene expression indicated that the uptake of symbiosis-derived components was increased together with a decrease in nematocyst formation, suggesting that prolonged deoxygenation could enhance the corals’ need for symbiosis-derived components and reduces its predation abilities. Coral orthologs of the conserved hypoxia pathway, including oxygen sensors, hypoxia-inducible factor (HIF) and its target genes were differentially expressed in a similar temporal sequence as observed in other metazoans including other species of corals. Overall, our studies show that by utilizing highly conserved and coral–specific response mechanisms, S. pistillata can acclimate to deoxygenation and possibly survive under climate change-driven oceanic deoxygenation. On the other hand, the critical importance of algal symbionts in this acclimation suggests that any environmental perturbations that disrupt such symbiosis might negatively affect the ability of corals to withstand ocean oxygen depletion.
  PubDate: 2022-12-02T00:00:00Z
Lifecycle, culture, and maintenance of the emerging cephalopod models
Euprymna berryi and Euprymna morsei
- Authors: Jeffrey Jolly, Yuko Hasegawa, Chikatoshi Sugimoto, Lin Zhang, Risa Kawaura, Gustavo Sanchez, Daria Gavriouchkina, Ferdinand Marlétaz, Daniel Rokhsar
  Abstract: Cephalopod research remains limited by the inability to culture species under laboratory conditions for multiple generations to provide continuous access to animals at all stages of the life cycle. Here, we describe a multi-generational laboratory culture system for two emerging cephalopod models: the hummingbird or Berry’s bobtail squid, Euprymna berryi Sasaki, 1929, and Morse’s bobtail squid, Euprymna morsei Verrill, 1881, which are primarily found off mainland Japan. E. berryi wild adults were spawned and raised to the third filial generation, and E. morsei wild adults were spawned and raised to the second filial generation in a closed system at 20°C. We report growth and survivorship data for a cohort of 30 individuals across the first generation raised in captivity. E. berryi and E. morsei grew exponentially during the first 90 and 60 days post-hatching, respectively. Survivorship at the first spawning event for E. berryi and E. morsei was 90% and 77%. E. berryi and E. morsei females spawned after days 112 and 71 days post-hatching, respectively. We describe the life history of each species and how to distinguish sexes. We discuss the challenges of cephalopod culture and how culturing these species address those problems.
  PubDate: 2022-12-02T00:00:00Z
Tropical cyclone Wind Pump induced chlorophyll-a enhancement in the South
China Sea: A comparison of the open sea and continental shelf
- Authors: Ying Li, Danling Tang
  Abstract: The continental shelf and open sea region have different ocean physical and environmental responses to tropical cyclones (TC). The present study firstly compared the grid-based maximum response (GMR) of sea surface chlorophyll a (Chl-a) to TCs Wind Pump between the continental shelf (depths 50-200m) and open sea (depths>200 m) region in the South China Sea (SCS) during 1998-2020, using multiple-satellite data. For all TC events, the average Chl-a increases by 0.13 mg/m3. The comparisons between the pre- and post-TC periods show that Chl-a increases by 0.18 mg/m3 (115%) in the continental shelf and 0.07 mg/m3 (57%) in the open sea region, respectively. In both areas, TC-induced Chl-a enhancement (Chl_en) strongly depends on TC maximum wind speed and translation speed. The strong and fast-moving TCs and weak and slow-moving TCs both induce the maximum Chl_en in the continental shelf region. While in the open sea, the maximum Chl_en was induced by the strong and slow-moving TCs. Overall, our results reveal that the TC wind pump’s effects on Chl-a enhancement are stronger in the continental shelf region than in the open sea.
  PubDate: 2022-12-02T00:00:00Z
A vortex-implanted initialization scheme for the mesoscale eddy
prediction: Idealized experiments
- Authors: Yuhang Zhu, Shiqiu Peng, Yineng Li
  Abstract: Mesoscale eddy prediction has been a big challenge to oceanographers and marine environment forecasters. Although the traditional initialization for the prediction, i.e., through assimilating the satellite-derived sea level anomalies (SLA) into a model, has some improvement, it is yet unable to predict well the main characteristics of a mesoscale eddy, including its three-dimensional (3D) structure, moving track, size, and intensity. In this study, a vortex-implanted initialization scheme for the mesoscale eddy prediction (VISTMEP) is developed. With the VISTMEP, a bogus vortex is first constructed in terms of 3D SLA-derived currents, and then it is implanted into the model initial field to obtain a more accurate 3D current field of a mesoscale eddy for prediction. The results from idealized experiments show that the VISTMEP can significantly improve prediction of the mesoscale eddy with a longer valid prediction length up to 30 days compared to the experiment with the traditional initialization. Detailed analysis indicates that, as the model is integrated forward, a more “realistic” 3D structure of the eddy in terms of both current and temperature fields is formed when the VISTMEP is employed, leading to the improvement of the eddy prediction regarding to the moving track, size, and intensity of the eddy, which is largely influenced by the accuracy of the initial current field of the eddy obtained by the VISTMEP. This study provides an innovative method for the mesoscale eddy prediction, which could have great potential application in operational services of the marine environments.
  PubDate: 2022-12-02T00:00:00Z
Spatial–temporal distribution of large-size light falling-net
fisheries in the South China Sea
- Authors: Jing Qian, Jiajun Li, Kui Zhang, Yongsong Qiu, Yancong Cai, Qiaer Wu, Han Tian, Shengwei Ma, Zuozhi Chen
  Abstract: With the rapid modernization of methods for monitoring fishing vessels, different ways of obtaining data on large-size light falling-net vessels have developed. In particular, the vessel monitoring system (VMS) may be used to track fishing activities in the South China Sea (SCS). In this study, we used VMS data to show the characterize and differences in the information transmitted when monitoring large-size falling-net fishing vessels, as well as their advantages and disadvantages. We investigated the spatial distribution of large-size light falling-net fisheries in the SCS using Beidou VMS data from 2017 to 2020. We also compared trajectories of fishing vessels from various provinces. According to these data, vessels operate in the Nansha Islands and the waters of the Pearl River Estuary, Beibu Gulf, Zhongsha, and Xisha Islands, and there is a clear seasonal pattern of fishing in the SCS. There are the differences of vessels in terms of distribution areas and ports of entry and exit. Additionally, we found the operation area of the large-size falling-net fishing vessels divided into four main fishing zones. The analysis compares the number of days of operation in the different fishing areas as well as seasonal variations. Our study shows that the operating area of large-size light falling-net vessels has extended southwards and that the number of days for which fishing vessels operate has increased compared with the last decade. Using the Beidou VMS to study the large-size light falling-net vessels in the SCS can provide more detailed scientific reference data for the SCS fisheries.
  PubDate: 2022-12-02T00:00:00Z
Determination of nitrogen content in Ulva fenestrata by color image
analysis – a rapid and cost-efficient method to estimate nitrogen
content in seaweeds
- Authors: Kristoffer Stedt, Gunilla B. Toth, Johan Davegård, Henrik Pavia, Sophie Steinhagen
  Abstract: There is an increasing interest in the cultivation of seaweeds for food and feed, and the seaweed aquaculture industry is rapidly developing. The nutritional status of the seaweeds is important to ensure a good quality crop. Cost-efficient and straightforward methods for farmers to analyze their crop are essential for the successful development of the industry. In this study, we developed non-destructive, labor- and cost-efficient models to estimate the nitrogen content in the crop seaweed Ulva fenestrata by color image analysis. We quantified tissue nitrogen content and thallus color in sea-farmed seaweed every week throughout a whole cultivation season (15 consecutive weeks) and analyzed data with linear regression models. We showed that color image analysis accurately estimated the nitrogen content in the seaweed (R2 = 0.944 and 0.827 for fresh tissue and dried powder, respectively), and through tenfold cross validation we showed that the developed models were robust and precise. Based on these models, we developed a web-based application that automatically analyzes the nitrogen content of U. fenestrata. Furthermore, we produced a color guide that can easily be brought to the farm for onsite crude estimation of the nitrogen content of U. fenestrata. Our results demonstrate that color can be a powerful tool for seaweed farmers (and researchers) to estimate seaweeds’ nutritional status. We anticipate that similar models can be developed for other commercially interesting seaweed species.
  PubDate: 2022-12-02T00:00:00Z
The increasing big gap of carbon sink between the western and eastern
Pacific in the last three decades
- Authors: Guorong Zhong, Xuegang Li, Jinming Song, Baoxiao Qu, Fan Wang, Yanjun Wang, Bin Zhang, Detong Tian, Jun Ma, Huamao Yuan, Liqin Duan, Ning Li, Qidong Wang, Jianwei Xing
  Abstract: The Pacific Ocean is one of the important carbon sink regions, and there is a significant west-east difference in sea-air CO2 flux. However, the influence of the long-standing greater CO2 uptakes in the western Pacific than in the east and the dynamic change of this west-east difference remain unclear. In this paper, using the gridded surface ocean pCO2 product constructed by the stepwise FFNN algorithm, we reported an increasing west-east CO2 flux difference from 0.41 PgC yr-1 in 1992 to 0.73 PgC yr-1 in 2020. This increase was mainly attributed to the strengthening western Pacific carbon sink and relatively stable eastern Pacific carbon source. During El Nino events, the west-east CO2 flux difference decreased significantly in a few years, and it then rose back rapidly when El Nino events ended. In addition, the increasing west-east difference in CO2 uptakes during the last three decades did not lead to a higher acidification speed in the western surface temperate Pacific than the east. The greater CO2 absorbed in the west was mainly transported to the deeper waters and caused a more significant carbon inventory change at 200-600 m than the eastern Pacific.
  PubDate: 2022-12-02T00:00:00Z