Long-term joint e ect of nutrients and temperature increase on algal growthin Lake Taihu, China

To study how global warming and eutrophication a ect water ecosystems, a multiplicative growth Monod model, modified byincorporating the Arrhenius equation, was applied to Lake Taihu to quantitatively study the relationships between algal biomass andboth nutrients and temperature using long-term data. To qualitatively assess which factor was a limitation of the improved model,temperature variables were calculated using annual mean air temperature (AT), water temperature (WT), and their average temperature(ST), while substrate variables were calculated using annual mean total nitrogen (TN), total phosphorus (TP), and their weightedaggregate (R), respectively. The nine fitted curves showed that TN and AT were two important factors influencing algal growth; ATlimited growth as algal photosynthesis is mainly carried out near the water surface; N leakage of phytoplankton and internal phosphorusload from sediment explains why TN was the best predictor of peak biomass using the Monod model. The fitted results suggest thatannual mean algal biomass increased by 0.145 times when annual mean AT increased by 1.0°C. Results also showed that the moreeutrophic the lake, the greater the e ect AT had on algal growth. Subsequently, the long-term joint e ect of annual temperature increaseand eutrophication to water ecosystems can be quantitatively assessed and predicted.