Dynamics of spatio-temporal distributions of phytoplankton in Lake Biwa in the recent years using satellite remote sensing

Abstract

　Recent estimates using data from the Earth observation satellite GCOM-C/SGLI have examined the impact of global warming on the spatiotemporal distribution of phytoplankton in Lake Biwa. This high-resolution satellite data allowed for comprehensive observations over a large area. This study analyzed the temporal variation in chlorophyll a concentration in the northern basin of Lake Biwa from 2018 to 2022. The results showed a significant decline in chlorophyll a concentration over the five years (p < 0.001, -0.03 mg m^-3 month^-1). Seasonally, there was no clear trend in chlorophyll a concentration during spring, summer, and winter, but a notable decreasing trend was observed in autumn. The study also noted a significant reduction in precipitation in the catchment area of Lake Biwa and a decrease in the deepening rate of the mixed layer during the over the observation period (five years). In summary, the decline in phytoplankton biomass in Lake Biwa is linked to reduced nutrient supply from within and outside the lake during autumn, resulting from changes in the hydrological cycle due to global warming.