Numerical simulation of nitrogen-phosphorus nutrient dynamics and ecological responses in Laizhou Bay during typhoon Lekima

Typhoons have a significant impact on the ecological environment of semi enclosed bays. This article takes the impact of typhoon Lekima on Laizhou Bay in August 2019 as an example, and constructs a physical biological coupled numerical model of Laizhou Bay to study the spatiotemporal distribution and ecological effects of dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP) under the influence of typhoons. The research results indicate that during typhoons, the pulse type input of nitrogen and phosphorus nutrients into the rivers around Laizhou Bay leads to corresponding supplementation of nutrients in Laizhou Bay. After the typhoon, the concentrations of DIN and DIP in the waters near the estuary increased to a certain extent, with the most significant increase in the Mihe estuary, reaching 4 mg/L and 0.15 mg/L, respectively; At the same time, the concentration of chlorophyll a (Chl a) in the Mihe estuary exceeded 10 μg/L, accompanied by algal blooms. Chl a concentration is sensitive to the maximum growth rate, initial slope of P-I curve, and mortality rate of phytoplankton. This study quantitatively analyzed the response of typhoons to ecological processes in semi enclosed bays, providing scientific reference for environmental management and ecological disaster prevention and control in Laizhou Bay.