Chinese Gaofen-3 (GF-3) is the first civilian satellite to carry C-band (5.3 GHz) synthetic aperture radar (SAR). During the period of August 2016 to December 2017, 1 523 GF-3 SAR images acquired in quad-polarization (vertical-vertical (VV), horizontal-horizontal (HH), vertical-horizontal (VH), and horizontal-vertical (HV)) mode were recorded, mostly around China’s seas. In our previous study, the root mean square error (RMSE) of significant wave height (SWH) was found to be around 0.58 m when compared with retrieval results from a few GF-3 SAR images in co-polarization (VV and HH) with moored measurements by using an empirical algorithm CSAR_WAVE. We collected a number of sub-scenes from these 1 523 images in the co-polarization channel, which were collocated with wind and SWH data from the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis field at a 0.125° grid. Through the collected dataset, an improved empirical wave retrieval algorithm for GF-3 SAR in co-polarization was tuned, herein denoted as CSAR_WAVE2. An additional 92 GF-3 SAR images were implemented in order to validate CSAR_WAVE2 against SWH from altimeter Jason-2, showing an about 0.52 m RMSE of SWH for co-polarization GF-3 SAR. Therefore, we conclude that the proposed empirical algorithm has a good performance for wave retrieval from GF-3 SAR images in co-polarization.

Environmental uncertainty represents the limiting factor in matched-field localization. Within a Bayesian framework, both the environmental parameters, and the source parameters are considered to be unknown variables. However, including environmental parameters in multiple-source localization greatly increases the complexity and computational demands of the inverse problem. In the paper, the closed-form maximum-likelihood expressions for source strengths and noise variance at each frequency allow these parameters to be sampled implicitly, substantially reducing the dimensionality and difficulty of the inversion. This paper compares two Bayesian-point-estimation methods: the maximum a posteriori (MAP) approach and the marginal posterior probability density (PPD) approach to source localization. The MAP approach determines the sources locations by maximizing the PPD over all source and environmental parameters. The marginal PPD approach integrates the PPD over the unknowns to obtain a sequence of marginal probability distribution over source range or depth. Monte Carlo analysis of the two approaches for a test case involving both geoacoustic and water-column uncertainties indicates that: (1) For sensitive parameters such as source range, water depth and water sound speed, the MAP solution is better than the marginal PPD solution. (2) For the less sensitive parameters, such as, bottom sound speed, bottom density, bottom attenuation and water sound speed, when the SNR is low, the marginal PPD solution can better smooth the noise, which leads to better performance than the MAP solution. Since the source range and depth are sensitive parameters, the research shows that the MAP approach provides a slightly more reliable method to locate multiple sources in an unknown environment.

A preliminary study shows that the submarine groundwater discharge (SGD) exists around Taiwan even though groundwater overdrawing on the island is serious. Fifteen of the 20 sites studied for major anions and cations recorded a clear SGD signal with freshwater outflow. A total of 278 salinity and major ion measurements were made. Sixteen nearly freshwater SGD (salinity≤1.0) samples were obtained, providing strong and direct evidence for the existence of fresh meteoric groundwater entering the ocean from Taiwan. The total SGD flux is estimated to be 1.07×10¹⁰ t/a which is about 14% of the annual river output. The freshwater component of the SGD is 3.85×10⁹ t which is about 5.2% of the annual river discharge in Taiwan. The collected SGD has a composition similar to seawater with an addition of Ca, CO₃ and HCO₃ due to dissolution of calcareous rocks. Some samples with high Cl/(Na+K) may indicate pollution.

Eutrophication of freshwater systems in cities is a major concern worldwide. Physical, biological and chemical methods have been used in eutrophic lakes and reservoirs to reduce their eutrophic state and algal biomass, but these approaches are not effective without a substantial reduction in nutrients input, which could take decades to achieve in the developing countries. This study aims to assess the risk of eutrophication and algal bloom in a coastal reservoir with high nutrient inputs to confirm the feasibility of inhibiting the reservoir's eutrophic state by hydrodynamic operations. A variety of water quality indexes (e.g., water temperature, secchi depth, dissolved oxygen, total nitrogen, total phosphorus, phytoplankton chlorophyll a) at five observed sites were investigated in the Qingcaosha reservoir, which located in the Changjiang Estuary, during the construction, trial and normal operation periods from 2009 to 2012. No water exchange happened during the construction from April 2009 to October 2010, and the water exchange increased during the trial from October 2010 to January 2011, and during normal operation period from January 2011. The comprehensive nutrition state index (TLI) calculated by several representative water quality indexes was adopted to evaluate the variation of the trophic state in the reservoir. The peak values of TLI reached 51 in the summer of 2009, and 55 in the summer of 2011, higher than the eutrophication threshold value 50. The lowest TLI, about 32, appeared in the summer of 2010. The values of TLI in other observation periods could keep under 50. The results showed that the reservoir could easily deteriorate into the eutrophic state because of excess nutrients and algal blooms in the summer of 2009 and 2011, while the eutrophication and algal blooms could be reduced by the lack of nutrients in 2010 or adequate water replacement in 2012. The temporal and spatial variations of water quality indexes were presented based on observation data and analysis. The adequate water replacement in the reservoir driven by tides was tested to be an efficient and economical method for controlling eutrophication and algae blooms in the water environment with high nutrient inputs.

The radionuclide ²¹⁰Pb is suitable for century-scale dating and has been used to calculate the sedimentation rate in a variety of environments. However, two common ways to apply ²¹⁰Pb dating techniques may give misleading results. One is “prolonging of age”, i.e., using the calculated sedimentation rate to date back to 200 or 300 years. This practice must be treated with caution because the ²¹⁰Pb dating techniques do not guarantee direct dating for ages much older than 100 years. Another is “loss of age”, i.e., the calculated time span between the topmost layer and the ²¹⁰Pb background layer in cores is less than 100 years when an apparent sedimentation rate is used in the calculation. Here, we propose that based on the principle of ²¹⁰Pb dating, the upper limit of age suitable for direct ²¹⁰Pb dating is between 110 and 155 years. The “prolonging” application is acceptable only if the sedimentary environment in the past several hundred years was stable and the sedimentation rate was generally constant, and verification with independent evidence (such as historical records or biomarker methodology) is needed. Furthermore, after analyzing many published and collected data, we found four possible reasons for the “loss of age”. First, the compaction effect of sediment should be corrected in laboratory analysis or else the calculated age will be underestimated. Second, the accuracy and uncertainty of ²¹⁰Pb activity measurement affect the judgment of the background. To be cautious, researchers are apt to choose a background activity with a younger age. Third, use of a slightly smaller value of supported ²¹⁰Pb activity in a calculation will lead to considerable underestimation of the time span. Finally, later-stage erosion and migration are common for sedimentation, which lead to loss of sedimentary records and are often reflected as a “loss of age” in cores. We believe that proper use of ²¹⁰Pb dating data may provide helpful information on our understanding of sediment records and recent environmental changes.

In order to carry out the genetic improvement of turbot upper thermal tolerance, it is necessary to estimate the genetic parameters of UTT (upper thermal tolerance) and growth-related traits. The objective of this study was to estimate genetic parameters for BW (body weight) and UTT in a two-generational turbot (Scophthalmus maximus L.) pedigree derived from four imported turbot stocks (England, France, Denmark and Norway). A total of 42 families including 20 families from G₁ generation and 22 families from G₂ generation were used to test upper thermal tolerance (40–50 animals per family) in this study and the body weight of individuals were measured. The heritability of BW and UTT and the correlation between these two traits were estimated based on an individual animal model using Bayesian method based on two types of animal models with and without maternal effects. These results showed that the heritabilities for BW and UTT and phenotypic and genetic correlations between the two traits estimated from model without maternal effects were 0.239±0.141, 0.111±0.080, 0.075±0.026 and –0.019±0.011, respectively. The corresponding values from model with maternal effects were 0.203±0.115, 0.055±0.026, 0.047±0.034 and –0.024±0.028, respectively. The maternal effects of BW and UTT were 0.050±0.017 and 0.013±0.004, respectively. The maternal effects had a certain influence on the genetic evaluation of the two traits. The findings of this paper provided the necessary background to determine the best selection strategy to be adopted in the genetic improvement program.

Genetic parameters and response to selection were estimated for harvest body weight in turbot. The data consisted of 10 952 individuals of 508 full-sib families from three generations (G0, G1, and G2). The heritability estimates for G0, G1, and G2 were 0.11±0.08, 0.18±0.09, and 0.17±0.07, respectively. Over three generations, the heritability estimate was 0.19±0.04. Maternal and common environmental effects were 0.10±0.04, 0.14±0.04, and 0.13±0.03 within each generation and 0.12±0.01 across generations. The selection differential in growth was 18.24 g in G0 and 21.19 g in G1 corresponding to an average of 19.72 g per generation. The genetic gains were also calculated, they were 22.06 g in G1 and 11.93 g in G2, corresponding to 6.36% and 3.52% body weight. The total genetic gain after two generations was 10.10% body weight, which indicated that the selective breeding program for the body weight trait in turbot was successful.

The migratory history of the engraulid fish Coilia nasus in the Rokkaku and Chikugo River estuaries of the Ariake Sea, Japan was assessed using otolith strontium (Sr) X-ray intensity maps and strontium:calcium (Sr:Ca) ratio life history transects by an electron probe microanalyzer (EPMA). The results showed that seven of the ten specimens from the Rokkaku River Estuary (LJC) and all 15 specimens collected in the Chikugo River Estuary (ZHC) had low Sr:Ca ratios (≤3) at the central otolith area, indicating their riverine origin and initial freshwater residence. After the first regime shift adjacent to natal regions, the Sr level mapping displayed a wide variety of color patterns, and the Sr:Ca ratios obtained by the line transect analysis could be divided into one to six significantly different phases indicative of gradual life history transition. The other three specimens from the Rokkaku River Estuary had high Sr:Ca ratios (3–6.7) at the central otolith area but showed alternating changes between low and high values outside the natal region, suggesting that estuarine-origin individuals occurred in the Rokkaku River Estuary. The two-dimensional maps of the Sr level and average of the otolith Sr:Ca ratios along the life-history transects could be used as effective tools for reconstruction of past habitat use of the tapertail anchovy in estuaries of the Ariake Sea, Japan.

The Japanese common squid Todarodes pacificus is an economically important species with one year lifespan, which is significantly influenced by climatic and environmental variability. According to the fishery data of the winter cohort of T. pacificus from 2003 to 2012, as well as environmental data and the Oceanic Niño index (ONI, which was defined by the sea surface temperature (SST) anomaly in the Niño 3.4 region), variations in the SST, chlorophyll a (Chl a) concentration, suitable spawning area (SSA) and sea surface height anomaly (SSHA) on the spawning ground of T. pacificus were examined under the El Niño and La Niña conditions. Their influences on squid abundance (defined by catch per unit effort, CPUE) were further assessed. The results showed that seasonal changes were found in SST, Chl a and SSA on the spawning ground of T. pacificus. Correlation analysis suggested that annual CPUE was significantly positively correlated with Chl a and SSA (p<0.05), but had insignificant relationship with SST (p>0.05). Moreover, the El Niño and La Niña events tended to dominate the changes of SSA and Chl a concentration in the key area between 25°–29°N and 122.5°–130.5°E, driving the variability of squid abundance. However, this influence varied with the intensity of each anomalous climatic event: the weak El Niño event occurred, the spawning ground was occupied by waters with enlarged SSA but with extremely low Chl a concentration, leading to low squid recruitment, the CPUE then decreased; the moderate intensity of El Niño event resulted in shrunk SSA but with high Chl a concentration on the spawning ground, the squid recruitment and CPUE increased; the moderate intensity of La Niña events yielded elevated SSA and high Chl a concentration on the spawning ground, the squid recruitment and CPUE dramatically increased. Our findings suggested that the ENSO events played crucial effects on the incubating and feeding conditions of the winter cohort of T. pacificus during the spawning season and ultimately affected its abundance.

Due to its unique geological location, the Bering Sea is an ideal place to investigate the water exchange and ecosystem connectivity of the Pacific Ocean–Arctic Ocean and subarctic–Arctic region. Based on a number of summer surveys (July to September, 2010, 2012 and 2014), macrobenthic communities and their spatial-temporal patterns are exhibited for the majority of the Bering Sea (53°59′–64°36′N). The results show that the macrobenthic communities were dominated by northern cold-water species and immigrant eurythermic species, and the communities assumed a dispersed and patchy distribution pattern. Polychaetes (Scoloplos armiger), crustaceans (Ceradocus capensis) and sea urchins (Echinarachnius parma) were the main dominant groups in the shallow shelves; the sea star (Ctenodiscus crispatus) and the brittle star (Ophiura sarsii) were the main dominant groups in the continental slope; whereas small polychaetes (Prionospio malmgreni) dominated the basin area. Sediment type, water depth, and currents were the major factors affecting the structure and spatial distribution of the macrobenthic communities. Compared with other seas, the shallow areas of the Bering Sea showed an extremely high-standing biomass. In particular, the northern shelf area (north of St. Lawrence Islands and west of 170°W), which is primarily controlled by Anadyr Water, is an undersea oasis. In contrast, a deficiency in the downward transport of particulate organic carbon has resulted in a desert-like seabed in the basin area. By comparing our results to previous studies, we found that macrobenthic communities of the Bering Sea have undergone significant structural changes in recent decades, resulting in a decrease in abundance and an increase in biomass. In addition, populations of amphipods and bivalves in the northern shelves have decreased significantly and have been gradually replaced by other species. These changes might be associated with advanced seasonal ice melting, changes in organic carbon input, and global warming, indicating that large-scale ecosystem changes have been occurring in the Bering Sea.