Phytoplankton Community Response to Environmental Factors along a Salinity Gradient in a Seagoing River, Tianjin, China

Abstract

A river-estuary ecosystem usually features a distinct salinity gradient and a complex water environment, so it is enormously valuable to study the response mechanism of living organisms to multiple abiotic factors under salinity stress. Phytoplankton, as an important part of aquatic microorganisms, has always been of concern for its crucial place in the aquatic ecosystem. In this study, phytoplankton data and 18 abiotic factors collected from 15 stations in Duliujian River, a seagoing river, were investigated in different seasons. The results showed that the river studied was of a Cyanophyta-dominant type. Salinity (SAL) was the key control factor for phytoplankton species richness, while water temperature (WT) was critical not only for species richness, but also community diversity, and the abundance and biomass of dominant species. Apart from WT, the abundance and biomass of dominant species were also driven by total nitrogen (TN), nitrate (NO3−), pH, and water transparency (SD). Moreover, total dissolved phosphorus (TDP), pH, and chemical oxygen demand (COD) were crucial for community diversity and evenness. The bloom of dominant species positively associated with TDP led to lower diversity and evenness in autumn. In addition, when available nitrogen was limited, Pseudoanabaena sp. could obtain a competitive advantage through the N2 fixation function. Increased available nitrogen concentration could favor the abundance of Chlorella vulgaris to resist the negative effect of WT. The results show that Oscillatoria limosa could serve as an indicator of organic contamination, and nutrient-concentration control must be effective to inhibit Microcystis bloom. This could help managers to formulate conservation measures.

Responses of Zooplankton Community Pattern to Environmental Factors along the Salinity Gradient in a Seagoing River in Tianjin, China

“…The river’s proximity to the ocean renders it susceptible to saltwater intrusion. Consequently, the entire river exhibits a salinity gradient that, in conjunction with other abiotic conditions, influences the survival, growth, and reproduction of aquatic creatures [ 10 ]. Please refer to [ 10 ] for the specific study area and sampling station, and the map is depicted in the Supplementary Materials for the convenience of reviewers and readers.…”

“…Furthermore, the environmental factors had significant seasonal variations, and the distributions of important environmental factors are shown in the Supplementary Materials (Table S2 and Figure S2) . For detailed descriptions of the environmental factors, please refer to the previous article [ 10 ], which was about the effects of environmental factors on the phytoplankton community. Since the sampling time of the zooplankton data in this paper was exactly the same as that of the phytoplankton data in the previous paper, the descriptions of the environmental factors are not described again in this paper in order to avoid duplication.…”

“…Zooplankton play important parts in transforming energy from lower-trophic organisms to higher ones, regulating phytoplankton growth, and shaping planktonic ecosystems [ 2 , 4 ]. Numerous previous studies on zooplankton have paid great attention to the effects of physicochemical environmental factors and nutrients on community parameters [ 5 , 6 , 7 , 8 , 9 , 10 ]. Local environmental factors, such as water temperature, pH, salinity, trophic state, or combinations of these factors, are responsible for shaping the local community structure (i.e., the species-sorting hypothesis) [ 11 , 12 ].…”

“…Local environmental factors, such as water temperature, pH, salinity, trophic state, or combinations of these factors, are responsible for shaping the local community structure (i.e., the species-sorting hypothesis) [ 11 , 12 ]. Moreover, nutrients are major environmental factors affecting zooplankton [ 5 , 10 ]. Nutrients can also affect zooplankton indirectly by affecting phytoplankton through a top-down effect.…”

Phytoplankton Community Stability as a Health Indicator of Whiteleg Shrimp in an Intensive Pond

“…Numerous studies on phytoplankton communities have demonstrated that phytoplankton-community characteristics such as species richness, community diversity, and community evenness can be driven by many abiotic factors and biological factors [Sun et al, 2023]. Studies have proven that phytoplankton community, species richness, community diversity, and species abundance are all closely related to nutrient concentrations [Soininen and Meier, 2014; Lusiana et al, 2020].…”