Piezocone penetration test (CPTu), the preferred in-situ tool for submarine investigation, is significant for soil classification and soil depth profile prediction, which can be used to predict soil types and states. However, the accuracy of these methods needs to be validated for local conditions. To distinguish and evaluate the properties of the shallow surface sediments in Chengdao area of the Yellow River Delta, seabed CPTu tests were carried out at ten stations in this area. Nine soil classification methods based on CPTu data are applied for soil classification. The results of classification are compared with the in-situ sampling to determine whether the method can provide sufficient resolution. The methods presented by Robertson (based on soil behavior type index I_c), Olsen and Mitchell are the more consistent and compatible ones compared with other methods. Considering that silt soils have potential to liquefy under storm tide or other adverse conditions, this paper is able to screen soil classification methods suitable for the Chengdao area and help identify the areas where liquefaction or submarine landslide may occur through CPTu investigation.

We aim to directly invert wave parameters by using the data of a compact polarimetric synthetic aperture radar (CP SAR) and validate the effectiveness of ocean wave parameter retrieval from the circular transmit/linear receive mode and π/4 compact polarimetric mode. Relevant data from the RADARSAT-2 fully polarimetric SAR on the C-band were used to obtain the compact polarimetric SAR images, and a polarimetric SAR wave retrieval algorithm was used to verify the sea surface wave measurements. Using the data and algorithm, there is no need to estimate complex hydrodynamic modulation transfer functions, even at large radar incidence angles. First, the radar backscattering cross-sections and backscattering cross-section of the radar linearly polarized with any polarization orientation angle were calculated in the two compact polarimetric SAR modes. Then, the wave slopes along the azimuth direction and the range direction were calculated directly using CP SAR data. Finally, we obtained the slope spectrum of the wave from the estimated wave slopes along azimuth and range directions. The wave parameters extracted from the synthetic wave slope spectrum were compared with those obtained from buoy observations of the National Data Buoy Center, verifying a suitable agreement.

In this study a novel synthetic aperture radar (SAR) scattering model for sea surface with breaking waves is proposed. Compared with existing models, the proposed model considers an empirical relationship between wind speed and wave breaking scattering to present the contribution of wave breaking. Moreover, the scattering weight factor p, and wave breaking rate q, are performed to present the contribution of the quasi-specular scattering term, Bragg scattering term, and wave breaking scattering term to the total scattering from the sea surface. To explore the modeling accuracy of sea-surface scattering, a simulated normalized radar cross-section (NRCS) and measured NRCS are compared. The proposed model generated the simulated NRCS and a matching GF-3 dataset was used for the measured NRCS. It was revealed that the performance of the VV polarization of our model was much better than that of HH polarization, with a correlation of 0.91, bias of −0.14 dB, root mean square error (RMSE) of 1.26 dB, and scattering index (SI) of −0.11. In addition, the novel model is explored and compared with the geophysical model of CMODs and satellite-measured NRCS from GF-3 SAR wave mode imagery. For an incidence angle 40°–41°, the relationship between the NRCS and wind speed, relative wind direction is proposed. As with the SAR-measured NRCS, the performance of VV polarization was much better than HH polarization, with a correlation of 0.99, bias of −0.25 dB, RMSE of 0.64 dB, and SI of −0.04.

The melt onset dates (MOD) over Arctic sea ice plays an important role in the seasonal cycle of sea ice surface properties, which impacts Arctic surface solar radiation absorbed by the ice-ocean system. Monitoring interannual variations in MOD is valuable for understanding climate change. In this study, we investigated the spatio-temporal variability of MOD over Arctic sea ice and 14 Arctic sub-regions in the period of 1979 to 2017 from passive microwave satellite data. A set of mathematical and statistical methods, including the Sen’s slope and Mann-Kendall mutation tests, were used to comprehensively assess the variation trend and abrupt points of MOD during the past 39 years for different Arctic sub-regions. Additionally, the correlation between Arctic Oscillation (AO) and MOD was analyzed. The results indicate that: (1) all Arctic sub-regions show a trend toward earlier MOD except the Bering Sea and St. Lawrence Gulf. The East Siberian Sea exhibits a significantly earlier trend, with the highest rate of −9.45 d/decade; (2) the temporal variability and statistical significance of MOD trend exhibit large interannual differences with different time windows for most regions in the Arctic; (3) during the past 39 years, the MOD changed abruptly in different years for different sub-regions; (4) the seasonal AO has more influence on MOD than monthly AO. The findings in this study can improve our knowledge of MOD changes and are beneficial for further Arctic climate change study.

In the western and central Pacific Ocean, upper strata waters exhibit highly dynamic oceanographic features under ENSO variability. This has been proved to be responsible for the dynamic change of both abundance and zonal distribution of skipjack tuna (Katsuwonus pelamis). Although causality has been suggested by researchers using physical–biological interaction models, cumulative evidence needs to be obtained and the tenability of assertion needs to be tested from an ecological habitat perspective, based on fisheries data. For purse seine fishery, the use of catch per unit effort (CPUE) as an indication of the abundance is confusing because of technical improvements over the whole exploitation history and unbalanced individual fishing characteristic of vessels. It is particularly interesting to discriminate between habitat characteristics in comparative scenarios of CPUE application. This study identified habitat traits based on a series of oceanographic factors from a global ocean reanalysis model. A comparison was conducted between two habitat models based on unprocessed purse seine CPUE and standardized CPUE considering fishing characteristics. The results suggest that standardized CPUE could model the regular zonal shift of habitat compatible with the observed fishing efforts transfer, and achieved better prediction capacity than unprocessed CPUE. Furthermore, the habitat of skipjack tuna was also characterized and linked with surface and subsurface thermal environment, ocean current, dissolved oxygen, biotic environment, and ENSO variability. The monthly-averaged habitat suitable index, derived from the optimal habitat model prediction, showed a significant linear relationship with the southern oscillation index, which suggested that El Niño episodes eventually provide more preferable habitat for skipjack tuna under ENSO variability.

The majority of fishery stocks in the world are data limited, which limits formal stock assessments. Identifying the impacts of input data on stock assessment is critical for improving stock assessment and developing precautionary management strategies. We compare catch advice obtained from applications of various data-limited methods (DLMs) with forecasted catch advice from existing data-rich stock assessment models for the Indian Ocean bigeye tuna (Thunnus obesus). Our goal was to evaluate the consistency of catch advice derived from data-rich methods and data-limited approaches when only a subset of data is available. The Stock Synthesis (SS) results were treated as benchmarks for comparison because they reflect the most comprehensive and best possible scientific information of the stock. This study indicated that although the DLMs examined appeared robust for the Indian Ocean bigeye tuna, the implied catch advice differed between data-limited approaches and the current assessment, due to different data inputs and model assumptions. Most DLMs tended to provide more optimistic catch advice compared with the SS, which was mostly influenced by historical catches, current abundance and depletion estimates, and natural mortality, but was less sensitive to life-history parameters (particularly those related to growth). This study highlights the utility of DLMs and their implications on catch advice for the management of tuna stocks.

Long-term variations in population structure, growth, mortality, length at median sexual maturity, and exploitation rate of threadfin bream (Nemipterus virgatus) are reported based on bottom trawl survey data collected during 1960–2012 in the Beibu Gulf, South China Sea. Laboratory-based analyses were conducted on 16791 individuals collected quarterly in eight different sampling years. Average body length, estimated asymptotic length, and percentage of large individuals have decreased significantly with the growth of marine catch and fishing power, indicating individual miniaturization of this fish species. Estimated exploitation rates indicate that the N. virgatus stock in the Beibu Gulf was moderately exploited in 1960 and 1962 and overexploited after 1992. This stock was taking a good turn in status in 2012, with the lowest exploitation rate since 1992 and ceased downward trend in length indexes. These results suggest that management measures to reduce fishing pressure may have a positive influence on the biological characteristics of this commercial fish species. Biological characteristics of most commercial fish species have phenotypic plasticity and might change over years in response to fisheries management. Therefore, attentions should be paid on variations in fish biological characteristics, when evaluating the effectiveness of current measures to control the total catch for all fisheries.

The size-spectrum model has been considered a useful tool for understanding the structures of marine ecosystems and examining management implications for fisheries. Based on Chinese tuna longline observer data from the central and eastern tropical Pacific Ocean and published data, we developed and calibrated a multispecies size-spectrum model of twenty common and commercially important species in this area. We then use the model to project the status of the species from 2016 to 2050 under five constant-fishing-mortality management scenarios: (1) F=0; (2) F=F _recent, the average fishing mortality from 2013 to 2015; (3) F=0.5F _recent; (4) F=2F _recent and (5) F=3F _recent. Several ecological indicators were used to track the dynamics of the community structure under different levels of fishing, including the mean body weight, slope of community size spectra (Slope), and total biomass. The validation demonstrated that size-at-age data of nine main catch species between our model predictions and those empirical data from assessments by the Western and Central Pacific Fisheries Commission matched well, with the R ²>0.9. The direct effect of fishing was the decreasing abundance of large-sized individuals. The mean body weight in the community decreased by ~1 500 g (21%) by 2050 when F doubled from F _recent to 2F _recent. The higher the fishing mortality, the steeper the Slope was. The projection also indicated that fishing impacts reflected by the total biomass did not increase proportionally with the increasing fishing mortality. The biomass of the main target tuna species was still abundant over the projection period under the recent fishing mortality, except Albacore tuna (Thunnus alalunga). For sharks and billfishes, their biomass remained at relatively higher levels only under the F=0 scenario. The results can serve as a scientific reference for alternative management strategies in the tropical Pacific Ocean.

In contrast to typical planktonic hydromedusae, Cladonema medusae are mostly benthic, with specialised adhesive branches to adhere to the substrate. In this study, a Cladonema species discovered in a laboratory aquarium in Fuzhou, China, was confirmed as a new species, based on morphological and molecular analyses. The species was named Cladonema multiramosum sp. nov. Its medusa is distinct from that of congeners possessing substantially more adhesive branches (8–24, rarely 5–7), and tiny branches on the upper radial canals. The validity of C. multiramosumum sp. nov. was also supported by molecular phylogenetic analyses based on the mitochondrial 16S rDNA sequence. However, C. multiramosum sp. nov. medusa also displayed considerable phenotypic plasticity with respect to its radial canals, tentacles, stinging branches per tentacle, oral tentacles, manubrium, and gonads, hindering species identification based solely on morphology. Although some morphological characteristics of hydroids (filiform tentacles and medusa buds) and nematocysts could also be used as diagnostic characters in the genus Cladonema, this information is unavailable for some Cladonema species. Thus, the taxonomy within the genus Cladonema was re-evaluated based mainly on the morphological characteristics of the medusa. Further revision of the genus Cladonema should be made when supplementary information on the life cycle and DNA barcoding are updated.

Antitumor activity is one characteristic function of some certain antimicrobial peptides (AMPs) found in recent years. In the present study, we attempted to detect potential anticancer activity of a recombinant piscidin 5-like from Larimichthys crocea (rLc-P5L) which owned widely antibacterial and strong antiparasitic activity in vitro. The light microscope observation indicated rLc-P5L was of antitumor activity to HeLa cells, 293T cells and L929 cells. MTT assay showed the toxic sensitivity of rLc-P5L to three tumor cell strains was 293T>L929>HeLa. Scanning electron microscope (SEM) results showed rLc-P5L behaved like a lytic peptide to cause damage on cells membrane of L929 cells by forming globular clusters, even pores at 60 μmol/L, or degrading membrane to make it completely lose cytoskeleton structure at 80 μmol/L; rLc-P5L treatment also resulted in DNA degradation. Fluorescence observation results indicated rLc-P5L could cause L929 cells at least two obvious changes: one is nucleus, nuclear chromatin condensed in the margin, nuclear volume became smaller and shrank to be out of shape, or lysed to be debris; the other is cytoskeleton, they became disordered and polarized to make cells atrophic shapes, or even lysed to be debris. In summary, rLc-P5L owned potential anticancer activity causing membrane structure damage and genome DNA degradation. Interestingly, treatment with different concentration of rLc-P5L seemingly caused the similar but different changes, whether it indeed gave rise to cancer cells diverse death way, the further studies should be performed, and the detailed mechanisms were still need further explored.