Seasonal Dynamics of Algal Net Primary Production in Response to Phosphorus Input in a Mesotrophic Subtropical Plateau Lake, Southwestern China

Yue Wu,Zeying Hou,Zhaosheng Chu,Jinpeng Zhang,Zebin Tian,Shengrui Wang

doi:10.3390/w14050835

Abstract

A comprehensive 3-dimensional hydrodynamic and eutrophication model, the environmental fluid dynamics code model (EFDC) with three functional phytoplankton groups, was applied to simulate the algal dynamics in a mesotrophic P-limited subtropical plateau lake, Lake Erhai, Southwestern China. Field investigations revealed the seasonal patterns in external total phosphorus (TP) input and TP concentration, as well as the composition of the phytoplankton community. The model was calibrated to reproduce qualitative features and the succession of phytoplankton communities, and the net primary production was calculated. The modeled daily net primary production (NPP) ranged between −16.89 and 15.12 mg C/m2/d and exhibited significant seasonal variation. The competition for phosphorus and temperature was identified as the primary governing factor of NPP by analyzing the parameter sensitivity and limitation factors of the lake. The simulation of four nutrient loading reduction scenarios suggested high phytoplankton biomass and NPP sensitivity to the external TP reduction. A significant positive correlation was found among NPP, total phytoplankton biomass and TP concentration. Overall, this work offers an alternative approach to estimating lake NPP, which has the potential to improve sustainable lake management.

Highlights

IntroductionThe global spread of water eutrophication has become a critical issue of importance and research interest [1–3]
The oversupply of nutrients always leads to eutrophication, which results in elevated gross primary productivity (GPP), net primary production (NPP) and a high level of chlorophyll (Chla) [7–9]
The results of our model indicate that the water quality of Lake Erhai would not be able to attain the targeted water quality standards (maintain

Summary

Introduction

The global spread of water eutrophication has become a critical issue of importance and research interest [1–3]. Nutrients, referring to nitrogen (N) and phosphorus (P) and biogeochemical cycles in lake watersheds are strongly influenced by the input of anthropogenic nutrients via river runoffs [4–6]. NPP, defined as the net accumulation rate of carbon, is among the critical properties of ecosystems, which forms the basis of food webs, and influences ecosystem-scale biogeochemical cycling rates. Understanding and forecasting the changes in NPP in response to external forcings, such as phosphorus, are major challenges for both scientific issues and improving sustainable lake management.

Methods

Results

Conclusion