While marine aquaculture, or mariculture, has been growing rapidly and globally in recent decades, many environmental concerns remain to be fully addressed to achieve its long-term goal of sustainable development. This paper aims to provide a synthesized perspective on these issues by reviewing and discussing the characterization, transport, and current modelling and management tools associated with effluents released from mariculture sites. Specifically, we examined the effluent characteristics and behavior from source-to-sink, including the composition and load of effluent discharge, its transport and transformation processes in the water column and at the seabed, and its impacts on the pelagic and benthic environments. We then focused on management-related issues, including the setting of the regulatory mixing zone, the establishment of environmental standards, monitoring measures, and modelling techniques to depict the current state-of-the-art modes in a global context. Our study shows that while substantial progress has been made in understanding the nature of the mariculture effluent, as well as in monitoring and modelling its transport and fate, the regulatory framework still lags behind in many countries where the mariculture industry is relevant. This is particularly evident in the lack of consistent criteria for the definition of regulatory mixing zones and the associated environmental standards for water quality and benthic impacts. Besides, as new predictive models are emerging quickly, their proper evaluation and validation are imperative in view of their increasing application in regulatory practices. This review is intended to provide references for advancing regulatory management of mariculture effluents, as well as for promoting sustainable mariculture development.

Satellite remote sensing data, such as moderate resolution imaging spectroradiometers (MODIS) and advanced very high-resolution radiometers (AVHRR), are being widely used to monitor sea ice conditions and their variability in the Bohai Sea, the southernmost frozen sea in the Northern Hemisphere. Monitoring the characteristics of the Bohai Sea ice can provide crucial information for ice disaster prevention for marine transportation, oil field operation, and regional climate change studies. Although these satellite data cover the study area with fairly high spatial resolution, their typically limited cloudless images pose serious restrictions for continuous observation of short-term dynamics, such as sub-seasonal changes. In this study, high spatiotemporal resolution (500 m and eight images per day) geostationary ocean color imager (GOCI) data with a high proportion of cloud-free images were used to monitor the characteristics of the Bohai Sea ice, including area and thickness. An object-based feature extraction method and an albedo-based thickness inversion model were used for estimating sea ice area and thickness, respectively. To demonstrate the efficacy of the new dataset, a total of 68 GOCI images were selected to analyze the evolution of sea ice area and thickness during the winter of 2012–2013 with severe sea ice conditions. The extracted sea ice area was validated using Landsat Thematic Mapper (TM) data with higher spatial resolution, and the estimated sea ice thickness was found to be consistent with in situ observation results. The entire sea ice freezing–melting processes, including the key events such as the day with the maximum ice area and the first and last days of the frozen season, were better resolved by the high temporal-resolution GOCI data compared with MODIS or AVHRR data. Both characteristics were found to be closely correlated with cumulative freezing/melting degree days. Our study demonstrates the applicability of the GOCI data as an improved dataset for studying the Bohai Sea ice, particularly for purposes that require high temporal resolution data, such as sea ice disaster monitoring.

Rapid invasion of Spartina alterniflora in coastal wetlands throughout the world has attracted much attention. Some field and imagery evidence has shown that the landward invasion of S. alterniflora follows the tidal channel networks as the main pathway. However, the specific patterns and processes of its invasion in salt marshes in relation to tidal channel networks are still unclear. Based on yearly satellite images from 2010 to 2018, we studied the patterning relationship between tidal channel networks and the invasion of S. alterniflora at the south bank of the Yellow River Estuary (SBYRE). At the landscape (watershed and cross-watershed) scale, we analyzed the correlation between proxies of tidal channel network drainage efficiency (unchanneled flow lengths (UFL), overmarsh path length (OPL), and tidal channels density (TCD)) and spatial distribution of S. alterniflora. At the local (channel) scale, we examined the area and number of patches of S. alterniflora in different distance buffer zones outward from the tidal channels. Our results showed that, overall, the invasion of S. alterniflora had a strong association with tidal channel networks. Watershed with higher drainage efficiency (smaller OPL) attained larger S. alterniflora area, and higher-order (third-order and above) channels tended to be the main pathway of S. alterniflora invasion. At the local scale, the total area of S. alterniflora in each distance buffer zones increased with distance within 15 m from the tidal channels, whereas the number of patches decreased with distance as expansion stabilized. Overall, the S. alterniflora area within 30 m from the tidal channels remained approximately 14% of its entire distribution throughout the invasion. The results implicated that early control of S. alterniflora invasion should pay close attention to higher-order tidal channels as the main pathway

Despite the backdrop of continuous global warming, sea ice extent has been found not to consistently decrease across the globe, and instead exhibit heterogeneous variability at middle to high latitudes. However, the existing studies are focused primarily on high latitude frozen seas, while studies on the long-term variability of sea ice cover at middle latitudes are generally lacking. Afforded by continuous satellite imagery, evolution of sea ice cover over nearly three decades from 1988 to 2015 in the Bohai Sea as a peculiar mid-latitude frozen sea area is reported for the first time. An anomalous trend of slight overall increase of 1.38 ± 1.00% yr^–1 (R = 1.38, i.e. at a statistical significance of 80%) in Bohai Sea ice extent was observed over the 28 year period. The detrended annual average ice area (AAIA) was further found to correlate with a slight decreasing mean ice-period average temperature (IAT, r = –0.58, p < 0.01) of 11 meteorological stations around the Bohai Sea as well as a mild increasing cumulative freezing degree days (CFDD, r = 0.65, p < 0.01). Correlation with decreasing Arctic Oscillation (AO) index (r = –0.60, p < 0.01) and North Atlantic Oscillation (NAO) index (r = –0.69, p < 0.01) over the study period suggested AO and NAO as the primary large-scale climate factors for Bohai Sea ice. In addition, the seasonal cycle of ice cover showed a single peak with longer freezing phase than melting phase, due to the different temperature change rate during the freezing and melting phases. The results can provide important references for monitoring the recent climate change in the region and beyond.