Influence of Salinity Gradient Changes on Phytoplankton Growth Caused by Sluice Construction in Yongjiang River Estuary Area

Menglin Yuan,Cuiling Jiang,Manxue Zhang,Xi Weng

doi:10.3390/w12092492

Abstract

Though the number of sluices and dams in coastal areas has increased rapidly in recent years, the influence of their construction on phytoplankton in estuary areas is hardly known. This paper aims to provide a reference for quantitative research on the ecological influence of sluice construction and give ecological justifications for the setting of environmental standards in the estuary areas. The survey data gained at the lower reach of the Yongjiang River and its estuarine areas in June 2015 were used in MIKE21 software (Danish Hydraulic Institute (DHI), Denmark)) for establishing a two-dimensional numerical model to simulate the salinity field distribution after sluice construction. Based on the simulation results, the salinity gradient changes caused by the construction were analyzed. The one-dimensional Gaussian model was applied to calculated the phytoplankton’s ecological threshold interval over the salinity changes, which helped predict the influence of salinity changes on phytoplankton cell density. The study shows that salinity in the Yongjiang estuary increases obviously, beyond the phytoplankton ecological threshold, after sluice construction without water discharge. Salinity will become a restriction factor to phytoplankton growth after sluice construction in the study area, which may cause a sharp decrease of certain phytoplankton species.

Highlights

The increasing demand for oceanic resources and services from mankind has brought great pressure to the aquatic ecosystem [1,2]
Several studies have analyzed the reaction of phytoplankton to ecological factors [8,9,10,11], but little analysis has been done from the perspective of an ecological threshold
This paper focuses on the study in the Yongjiang River estuary in Ningbo, Zhejiang Province, China

Summary

Introduction

The increasing demand for oceanic resources and services from mankind has brought great pressure to the aquatic ecosystem [1,2]. Rojo C et al studied phytoplankton species richness related to drought in the semiarid wetland of. Las Tablas de Daimiel National Park in Central Spain and found out that phytoplankton could be used to effectively track the environmental changes in the wetland [6]. Rath A R et al investigated the relationship between seasonal-spatial distribution of phytoplankton and environmental factors in the New Mangalore Port along the western coast in India. Several studies have analyzed the reaction of phytoplankton to ecological factors [8,9,10,11], but little analysis has been done from the perspective of an ecological threshold. Phytoplankton is very suitable for analyzing the ecological threshold of environmental gradients on large spatial scales because of its unique performance as an ecological indicator of environmental changes in different ecosystems [12]

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Conclusion