Jellyfish blooms have become a marine environmental issue with detrimental effects on marine ecosystems around the world. The jellyfish Aurelia aurita is one of dominant species of blooms worldwide and also in the Bohai and Yellow Seas (BYSs) of China. To investigate population dynamics and controlling factors on population biomass, a complex population-dynamic model is developed for jellyfish of A. aurita in the BYSs that includes three components, namely, a three-dimensional coupled physical–biogeochemical model, a Lagrangian particle-tracking model, and an energy balance model for the jellyfish life cycle. By comparison, the model well reproduces the individual growth and seasonal evolution of A. aurita population. During individual growth period, the temperature is a key factor controlling growth and dry weight, characterized by a nearly linear growth rate. Longer period tends to favor larger medusa size and further to promote the biomass. The yearly peak biomass shows interannual variations that are controlled by the jellyfish magnitude, food concentration, and effective accumulative temperature of growth, with their contributions quantified through statistical analyses. Only considering the effect of temperature, the yearly peak biomass can be obtained through the durations of suitable temperature ranges for strobilization and individual growth that determines the magnitude and the averaged individual weight, respectively, with longer strobilation duration leading to higher magnitude. The simplified statistical relationships would favor to understand the temperature control on population dynamics of A. aurita.
Lingdingyang (LDY) is an important navigation waterway for the Pearl River delta (PRD), and an important passage for fresh water and sediments entering the sea. The data and hydrological information, including SSC, current, water level, and bed sediment was collected on July 6 -7, 2005 to analyze its characteristics, and sediment transport. The data was entered into a hydrodynamic simulation model used to characterize the processes of sedimentation and morphological evolution of the Pearl River estuary (PRE). LDY was divided into three sub-areas dominated by (1) west shoal area, (2) jet flow area, and (3) saline water area. Navigation engineering and other human activities result in an increase of deposition rate. These characteristics can be greatly accelerated by human activities. Field data and model results indicate that the front system, composed of the shear front and tide incursion front, has an important impact on sedimentation.
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