The researchers studied the seasonal changes and locations of chlorophyll-a in Lake Erhai from May 2010 to April 2011. They found that chlorophyll-a levels varied throughout the year, with higher concentrations in summer and autumn and lower in winter and spring. The southern part of the lake had the highest chlorophyll-a levels, followed by the northern and middle areas. Chlorophyll-a was linked to water temperature and transparency, with higher levels correlating with warmer water and lower transparency. Total nitrogen was related to chlorophyll-a in the northern and southern zones, while total phosphorus was linked in the southern zone. Overall, Lake Erhai was classified as mesotrophic based on its trophic state index of 50.6.