Effects of different nitrogen species on sensitivity and photosynthetic stress of three common freshwater diatoms

Abstract

Different sources of nitrogen pose diverse effects to algal community, but the mechanism of inhibitory effects of nitrogen sources on freshwater diatoms is not fully understood. The purpose of this study was to compare biomass, photosynthetic activity, and morphological structure of three common freshwater diatoms (Cyclotella meneghiniana, Nitzschia sp., and Gomphonema parvulum) under different nitrogen sources (NO 3 -or NH 4 ?). The sorption characteristic of each diatom was investigated, and chlorophyll a (Chl-a) content and oxygen evolution rate were analyzed to investigate stress of different nitrogen sources on each diatom in the batch experiments. Ammonium lowered the growth rate of C. meneghiniana and Nitzschia sp.when it was supplied in addition to growth-saturating nitrate concentrations, suggesting a combined effect of inhibition of nitrate uptake and direct ammonium stress. Oxygen evolution rate of Nitzschia sp. showed that the direct ammonium stress on the photosynthetic activity can be alleviated by coexistence of nitrate in the nitrogen enriched treatment, but not for C. meneghiniana and G. parvulum, which may be caused by a different nitrate transporter system within algal cells. Transmission electron microscopy was used to assess the toxicity of ammonium on ultrastructural chloroplast of each diatom. Ultrastructural changes in chloroplasts showed undefined electron-dense granules and lipid droplets, but the membrane integrity of cell was maintained, suggesting an adaptation to adjustment to ammonia stress. Results showed that Cyclotella meneghiniana and Nitzschia sp. were more sensitive to ammonium stress than Gomphonema parvulum on growth, but the mechanism remains unclear.

Impact of wastewater treatment plant effluent on an urban river

“…However, considering the pollution caused by the inflow of sewage in the river, the most distinctive change in water quality in the Chuanfang River after the influx of STP effluent was actually the sudden increase in NO 3 -N concentration. Thus, in terms of water quality, NO 3 -N can be considered a key parameter that caused the dominant phytoplankton taxa to shift to diatoms in the Chuanfang River (Iriarte et al 2013;Zhang et al 2013;Deng et al 2014;Baek et al 2015). This inference is highly consistent with the laboratory experiments conducted by Deng et al (2014).…”

A river‐scale Lagrangian experiment examining controls on phytoplankton dynamics in the presence and absence of treated wastewater effluent high in ammonium

“…Cyanobacteria (blue‐green algae) are less nutritious, and some species may produce toxins (Chorus and Bartram , Lehman et al ). However, laboratory‐based studies also suggest that phytoplankton responses to the availability of vs. can vary among species or even within a single species, depending on growing conditions and other factors (e.g., Donald et al , Cloern and Jassby , Donald et al , Zhang et al , Cloern et al , Collos and Harrison , Esparza et al ).…”

Changes in phytoplankton communities along nutrient gradients in Lake Taihu: evidence for nutrient reduction strategies

“…Ammonium could lower the growth rate of C . meneghiniana at high nitrate levels (Zhang et al, 2013). Ammonium levels in Lake Taihu increased in spring along with high TN levels (Zhang et al, 2011).…”