Seasonal variations in response of periphytic algal community to nutrient enrichment in the river Ganga (Varanasi, India)

Abstract

Effect of nutrient enrichment on periphyton was studied using chemical diffusing substrates that released, singly or in combination, PO43−-P and nitrogen, both NO3−-N and NH4+-N. The study was carried out in March and June 2014 as these two time periods showed abundance of different groups of algae. Whereas diatoms and green algae were abundant in March, cyanobacteria dominated in June. Nitrogen was primarily growth limiting in river water as its enrichment enhanced the growth of periphyton. Phosphate limitation was secondary in nature. Enrichment of NH4+-N caused greater enhancement of periphytic growth than that of NO3−-N. Nutrient enrichment reduced species diversity, further enhancing total biovolume of the periphytic group that was predominant at that particular point of time. Nutrient enrichment markedly increased cyanobacterial populations in June due inter alia to high temperature. In spite of nutrient enrichment, the periphytic biomass did not reach the level (chl a ≥ 100–150 mg m−2) considered as the nuisance, except in March when combined enrichment of PO43−-P and NO3−-N greatly enhanced the periphytic biomass.

Nutrient Exposure Alters Microbial Composition, Structure, and Mercury Methylating Activity in Periphyton in a Contaminated Watershed

“…This pattern may be due to variations in physiochemical parameters such as nutrients, light, and temperature. Temperature is a large determinant of algal growth ( Allen and Hershey, 1996 ; Teubner, 2000 ; Pfeiffer et al, 2013 ; Yadav et al, 2018 ) but the water temperature in our experiment did not change. Additionally, our nutrient exposure was consistent and regulated by the NDS cups across seasons.…”

“…The highest algae and cyanobacteria abundance were measured in nitrate treatments while nitrate + phosphate treatments had the lowest abundance in autumn, suggesting that algal communities may be nitrogen and not phosphorus limited in autumn. Periphytic nitrogen limitation in aquatic systems has been confirmed ( Dodds and Welch, 2000 ; Yadav et al, 2018 ); however, phosphorus limitation is common ( McDowell et al, 2020 ). It is possible that the associated changes with phosphorus may be directly due to the interaction of nutrient status with light availability and temperature ( McCall et al, 2017 ) or indirectly from changes in secondary metabolites ( Leflaive and Ten-Hage, 2007 ) or negative interactions from microbiome changes associated with physiochemical properties ( Beck and Hall, 2018 ).…”

<em>In situ</em> effects of arsenic, aluminium and chromium stresses on algal periphyton of the river Ganga at Varanasi, India

“…These three concentrations were chosen on the basis of our laboratory and field trails for 1 month. Based on these trails our group already published several research papers in the past (Pandey et al, 2014;Pandey and Bergey, 2018;Yadav et al, 2018). The CDS constructed earlier were then filled with one of the different metal solutions and deployed in triplicate in the river Ganga.…”

“…The CDS encompasses a porous substratum, which not only releases the test chemical via its porous surface but also provides a substratum for the attachment of periphyton. Diffusing substrates have been proven to be a good system which could be satisfactorily employed for the field study (Fairchild et al, 1985;Pandey et al, 2014;Yadav et al, 2018). Thus, prompted by earlier studies, the present investigations employed CDS for in situ study of heavy metal stress on periphyton.…”

“…Periphytic algae are an important component in these ecosystems, where they constitute a major proportion of primary producers at the base of the aquatic food web. Periphyton plays an important role in nutrient cycling and has been acclaimed to be excellent indicator of water quality (Yadav et al, 2018). Although substantial progress has been made in understanding the response of these communities to various metal contaminants, the perusal of literature suggests that aluminium, arsenic and chromium have been little explored with regard to their effects on algal periphyton.…”