As the development of marine ecosystem models, the number of biological parameters increases, which consequently causes determination of these parameters to become a bottleneck in ecosystem modeling. Intrinsic regional characteristics of the ecosystem require spatial variability of biological parameters. To explore spatial difference of key parameters and their sensitivity, a highly resolved physical-biological ecosystem model ROMS-CoSiNE of the Bohai Sea and Yellow Sea is established. Sensitivity analysis of thirteen biological parameters indicates that strong difference in sensitivity exist between the south center Yellow Sea, the Bohai Sea and it’s coastal areas as well. The most sensitive parameter in the Bohai Sea is the initial slope of P-I curve. The second and third are the half saturation constant for zooplankton grazing and the maximum specific growth rate of zooplankton. For the south Yellow Sea, the most sensitive parameters are the maximum specific growth rate of zooplankton, the death rate of phytoplankton and the initial slope of P-I curve. Based on sensitivity distribution and phytoplankton budget, it is concluded that the low transparency in the Bohai Sea and high transparency in the Yellow Sea are mainly responsible for spatial difference of sensitivity relative to the initial slope of P-I curve. Spatial difference of sensitivity relative to the maximum specific growth rate of zooplankton and the death rate of phytoplankton, is affected by phytoplankton amount difference between the Bohai Sea and the Yellow Sea, and related to high nonlinearity in the ecosystem.

Nutrient enrichment, followed by economic development, has already had a significant impact on the costal ecosystem of China. Field investigations on seaweed beds adjacent to Lingshui River in Dalian were conducted in present studies to elucidate the response of the seaweed communities to the sewage effluents along a natural nutrient gradient. Further, the studies were conducted in the laboratory on the uptake and growth kinetics of NO₃ ^–, NH₄ ⁺ and PO₄ ^3– of the clone of Enteromorpha linza, r-strategic green alga dominating in the nutrient-rich estuaries, and Ceramium tenerrimum, k-strategic red alga distributing in the oligotrophic areas. Comparative analyses were carried out on the absorption and utilization of nutrient, and reproduction strategies of the two species to explain the responses of seaweed communities to different nutrient environments. The results show that with the decrease of environmental nutrients, species number of seaweed increases, and the coverage of dominant species decreases. According to the response of seaweed communities to nitrogen nutrient, it is considered that the threshold of category I of inorganic nitrogen in the current seawater quality standard should be revised from the current 14.29 μmol/L to 6.69 μmol/L. In a nutrient-rich area, increasing nutrient concentration promotes the competitiveness and fertility of shoots of r-strategic seaweeds, which makes them occupy a large number of space niches and form dominant populations, resulting in decreasing of the diversity of seaweed communities. However, in the oligotrophic environment, r-strategic algae is limited in the fertility of shoots, occupying only small amount of space niche, while those k-strategic algae with high efficiency in nutrient utilization shows greater competitiveness and could quickly break through early environmental sieves and grow into adults, which contributes to the rich diversity of seaweed communities.

Chub mackerel (Scomber japonicus) is one of the important fishery resources in the northwest Pacific Ocean. Building a scientific forecast model of abundance index to this species is beneficial for its exploitation and utilization. In this study, based on the biomass data of the Pacific-cohort of Scomber japonicus during 1987–2012 obtained from Japan Fisheries Institution, as well as the marine environmental data and climatic data of spawning ground and fishing ground, we analyzed the relationship between the environmental and climatic factors and the biomass of this cohort. The significant factors were selected and the forecast models were established by using the generalized addictive models (GAM). The result shows the significant factors affecting the biomass of this cohort conclude the Arctic Oscillation index (AOI), Pacific Decadal Oscillation index (PDOI) and sea surface height (SSH2), sea surface salinity (SSS2) and sea surface temperature (SST2) both in the fishing ground. Result based on Akaike’s Information Criterion (AIC) suggests that the model 1 which included AOI, SSH2 and SST2 has the optimal model impacts. The model 1 passes the significant test (P<0.05) and the t test (P<0.05) is also passed based the validation result of model 1. Therefore, we suggest that this model can be used to forecast the abundance of the Pacific-cohort of Scomber japonicus.

Phytoplankton, as the base of the oceanic food chain, plays a fundamental role in marine ecosystems. Since the Bohai Sea, the largest inner sea in China, is an important spawning ground and nursery field as well as a feeding ground for marine creatures, it is critical to understand variations of phytoplankton in the area. Chlorophyll a (Chl a) concentration is an important proxy for phytoplankton biomass. Chl a derived from both the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) from 1997 to 2010 and the MODerate resolution Imaging Spectroradiometer (MODIS) sensor on satellite Aqua from 2002 to 2018 were combined into one time series to investigate the spatial and temporal variability of Chl a concentrations in the Bohai Sea using Google Earth Engine. Annual Chl a concentrations increased significantly by 14.1% in the study area over the past two decades. Chl a concentrations in every season and in all months except November have stagnated or increased. Chl a concentrations increased mainly in the middle part of the sea. Sea surface temperature (SST), wind speed and precipitation were also analyzed. Increases in precipitation over the land around the Bohai Sea and wind speed in summer, as well as decrease in SST in autumn, all contributed to the rises of Chl a concentrations. Nutrients from land may play an important role in phytoplankton growth.

Based on the ionospheric correction data of Global Ionospheric Map (GIM) and dual-frequency, extracting the Pacific Ocean dataset from the Jason-2 Altimeter’s Geophysical Data Set (GDR) including 38-period in 2015. The dataset is divided into small twelve cell according to the features of ionosphere over seasons and in latitude. The result shows that there is a significant difference between the GIM and the dual-frequency correction value, and the GIM correction value is generally higher than the dual-frequency correction value, indicating that GIM overestimates the ionosphere path delay, also, the difference between the GIM and the dual-frequency is related to the season and latitude. Applying the modified equation to the 2016 Jason-2 annual data, the corrected GIM value is very close to the dual-frequency correction value, and the applicability of the modified equation remains the same over time. In the case where the single-frequency altimeter cannot use the ionospheric dual-frequency correction algorithm, the GIM value of the altimeter of the same height can be corrected by using the correction equations of different quarters and different latitude regions to achieve the accuracy level of the dual-frequency correction value.

Variation of pore pressure between soil particles, which caused by the cyclic loading from waves to seabed, is the main reason for soil liquefaction. By using a self-designed pore pressure monitoring equipment, we monitored pore pressure with a long-period, high-precision way in the easy-liquefied zone in Chengdao sea area of Yellow River Estuary. The monitoring results show that the maximum wave-affected depth is between 0.5 m to 1.5 m and no obvious pore pressure response in the deeper sediment during this period. Pore pressure variation in soil is mainly determined by tide level and wave height. Tide level changes can result in smooth change in pore pressure but can not cause the emergence of excess pore pressure while wave height changes can result in severe oscillation in pore pressure and lead to the appearance of excess pore pressure.

The shipboard ADCP (Acoustic Doppler Current Profilers) backscatter intensity data in the Eighth Arctic Science Expedition are analyzed for the temporal and spatial characteristics of the sound scattering layer (SSL), by combining the solar altitude, the sea ice concentration and the in-situ data of the water environment parameters. The results show that the higher the latitude is, the shorter the time of the SSL is on the sea surface. Even during the period of polar day and all covered by sea ice, the migration amplitude and backscattering intensity of the SSL are weakened, but they are still affected by the change of the solar elevation, and there is a strong temporal correlation between them and solar altitude angle. In the middle section of the Arctic, the migration of the SSL is weak, and there is no obvious SSL observed, the reason may be that the concentration of zooplanktons and fishes are relatively lower and the migration is weak, which is beyond the accuracy range of ADCP used in this paper. ADCP data in the back and forth from the Okhotsk Sea to the southwest of the Bering Sea, show that there are two SSLs, the shallower depth and the greater backscatter intensity, but their vertical migration time is synchronized, and the spacing between them is gradually reduced and combined as the latitude increases, it may be caused by marine organisms with different life habit.

Based on the in-situ data from mooring deployed in the northwest South China Sea, we investigate the dynamical and thermal dynamical response of upper ocean to Typhoon Doksuri. In the aspect of dynamic response, as the Typhoon passing, the currents in upper layer enhanced strikingly, the zonal currents in the mixed layer reaches 1.20 m/s. After the passage of Typhoon Doksuri, the currents in the upper layer are dominated by near-inertial oscillation, which rotate clockwise with a period between 36–40 hours. The kinetic energy of near-inertial wave shows two high energetic cores in vertical, which locates at the mixed layer and the thermocline layer, respectively. The estimated e-folding time-scale of near-inertial energy decay is about 3.7 d, and we believe that the downward propagation of energy is the major reason for the decay. The power spectra analysis of currents reveals that power density at inertial frequency, during the period of Typhoon Doksuri, increases about 29.4 times larger than that before the Typhoon arriving. Nevertheless, power density both at diurnal (K₁) and semidiurnal (M₂) frequency decreases during Typhoon period. Additionally, a blue shift at inertial frequency is identified. We find that the averaged near-internal frequency in upper 400 m is 1.167 f₀ for zonal near-inertial currents and 1.170 f₀ for meridional near-inertial currents (where f₀ is the local inertial frequency). This blue shift is connected with the downward propagation of near-inertial waves and input of positive relative vorticity. In the aspect of thermodynamic response, the temperature rises in the upper layer between 40–250 m depth, due to the stirring induced by strong wind, and the maximum increased temperature amplitude is about 1℃. In addition, the decrease of salinity above 70 m may be related to the precipitation caused by the Typhoon. While the upwelling induced by Ekman pumping may have significant contribution to the increase of salinity at the depth of 70–100 m.

Comparison with Geophysical Model Function (GMF) developed by methods of empirical statistics, ocean microwave scattering model works well at all microwave frequency. Composite radar backscattering model is comprised of Bragg scattering model and geometrical optics model. We calculated the normalized radar cross sections (NRCSs) from the composite scattering model by using the sea surface wind speeds and directions measured by buoys moored in the northern of South China Sea in the whole year of 2014, and then compared them with SAR on board RADARSAT-2 at C-band, microwave scatterometer on board HY-2A satellite (HSCAT) at Ku-band, respectively. The biases of comparison are (–0.22±1.88) dB ( for SAR), (0.33±2.71) dB (for HSCAT in VV polarization) and (–1.35±2.88) dB (for HSCAT in HH polarization), respectively. We also calculated the NRCSs from the model by using the sea surface wind speeds and directions measured by NDBC buoys in the time period from October 1, 2011 to September 30, 2014, and then compared them with radar altimeter on board Jason-2 and HY-2A both at Ku-band with the bias of (1.01±1.15) dB and (1.12±1.29) dB, respectively. Although the biases of NRCSs between space-borne sensors and composite scattering model in medium and normal incidence are different each other, the accuracies of their sea surface wind speed products are the same(i.e. the root mean square errors are all less than 1.71 m/s). The results show that we can simulate the sea surface radar NRCSs of satellite-borne SAR, microwave scatterometer, and altimeter by using the composite radar backscattering model, and the simulations are consistent with that of CMOD5, NSCAT-2 and the GMF of operational wind retrieval for altimeter. It also indicates that the composite radar backscattering model could be used in calibration and validation of microwave sensors and simulation of radar backscatter from sea surface.

By monitoring the typical profiles of the artificial cobble and sandy beach on Xiamen Tianquan Bay and Huizhan before and after the super Typhoon No.1614 Meranti, combined with the observation and numerical simulation of hydrodynamic factors, we calculate the wave field together with the total water level during the typhoon process, and analyze the morphology and the average variation of the profile. Results show that the characteristics of response to typhoon between artificial cobble and sandy beach on macro-tidal coast are significantly different. The majority of cobbles transported onshore, the beach face eroded while the beach berm accumulated to form a higher beach berm, and the slope of the artificial cobble beach is obviously steepened. In contract, the artificial sandy beach shows obvious sediment transport offshore, the upper beach face eroded and the lower beach face deposited, the slope of the beach face obviously become gentler, moreover the top of the beach berm become flattened due to the strong onshore wind after the typhoon landing, and the height of the beach berm almost remain unchanged. Whether the beach berm eroded during typhoon process is closely related to the total water level including astronomical tide, storm surge and wave run-up. During the process of typhoon, the artificial cobble beach characterized with higher wave energy and steeper beach slope showed less profile variation comparing to that of the artificial sandy beach. The artificial cobble beach performed a small degree of response to typhoon. Taken together, it is an effective approach of slowing sandy beach erosion by using gravels and other coarse-grained sediments for beach nourishment on strong eroded high-energy macro-tidal coasts.