Jing Yang

Since 2007, green tides have recurrently occurred in the Yellow Sea during spring and summer, with a massive outbreak recorded in 2021. Given the critical significance of green tide monitoring and prediction for marine ecological security and sustainable development, this study developed a satellite remote sensing-validated coupled simulation system for green tide drift and growth, by integrating multi-source satellite remote sensing data and oceanographic reanalysis datasets. Leveraging this system, we systematically analyzed the spatiotemporal evolution characteristics and underlying driving mechanisms of both routine green tide processes in 2014–2015 and the extreme 2021 event. Satellite images with low cloud cover and extensive green tide distribution were screened to confirm the accuracy of green tide drift trajectories and distribution ranges for validating the model’s reliability, and the results demonstrated the spatial consistency between simulation results and satellite observations. The validated model was used to track the drift and growth–decline processes of green tides and investigate the underlying cause of high-biomass appearance in 2021. Combined with environmental parameters, our analyses revealed that variations in attachment substrates alter wind resistance coefficients, thereby potentially accelerating the northward drift velocity of green tides. Furthermore, substrate properties may exert a significant regulatory effect on the attachment, germination, and biomass accumulation of Ulva prolifera spores, which could be a leading factor driving the massive green tide outbreak.

To assess the environmental impacts of tritium-containing wastewater discharge from the Fukushima Daiichi Nuclear Power Plant, we conducted a 10-year three-dimensional simulation of seabed-discharged dissolved and particulate tracers in the Pacific Ocean and its marginal seas using the Regional Ocean Modeling System (ROMS). The domain was partitioned into 11 regions to quantify dispersion pathways, particle trajectories, concentration evolution and inventory (accumulation) changes. Tracer levels are highest near the seabed discharge location (SDL) and subsequently dispersed to the deep western Pacific (DWP), the deep eastern Pacific (DEP), and ultimately into western Pacific marginal seas; subsurface and deep-layer tracers intrude into marginal seas earlier than surface tracers. Over the decade, discharge-induced concentration increments are even below the practical detection limits in most regions, with detectable maxima above natural background primarily only confined to the SDL ( >70 Bq/m3 ) and DWP (~20-30 Bq/m3). The SDL median remains near 10-4 Bq/m3. Median concentrations approach 10-4 Bq/m3 in open Ocean and some marginal seas (i.e., South China Sea), but do not reach this level elsewhere within the simulation period. Maximum concentrations exceed 10-2 Bq/m3 in most regions, except in the least and latest impacted regions (i.e., JSB). Overall, both dissolved and particulate tracers accumulate mainly in the open Pacific east of the discharge site, with limited impacts on marginal seas within 10 years. Given the planned intermittent discharge over ~30 years, longer-term simulations and sustained monitoring are needed to evaluate the longer-term cumulative risks to marginal seas.