Alaknanda of upper Ganges. The exotic species are comparatively stronger, cause
habitat modification, and generate competition for food, light, and other resources.
Singh et al. (2010) have reported that abundance of exotic fishes such as Cyprinus
carpio and Oreochromis niloticus in the Ganga River has negatively influenced the
economically important indigenous fishes such as Catla, Labeo rohita, and
Cirrhinus mrigala. Khanna et al. (2007) have reported that prolonged exposure of
fishes to deteriorated environmental conditions causes severe irreversible damage to
scale circuli and lepidonts resulting in loosening of scales.
The excessive inputs of nutrients promote phytoplankton growth. Although they
are the basis of food chain, they can be harmful to human and other vertebrates as
they release toxic substances (Ariyadej et al. 2004). At Kanpur (Jajmau),
Phormidium, Aphanocapsa, and Oscillatoria have been reported in abundance
(Singh et al. 2014). These species generally occur at places with high concentration
of nutrients. A study conducted in Varanasi region has reported negative relationship
between benthic algal biomass and DOC and a positive correlation with Secchi depth
suggesting the role of water transparency (Pandey 2013). Furthermore, large biomass of Phormidium uncinatum was reported in high DOC region. The study
suggests that the increasing DOC concentration is changing the light climate and
fate of benthic producers in the Ganga River (Pandey 2013). A point source-linked
study at Bijnor (UP) has reported the prevalence of pollution-tolerant species
Synedra, Cocconeis, Spirulina, Botryococcus, and Chlamydomonas. Sensitive species such as Cladophora and Euglena disappeared from these sites (Negi and Rajput
2013). In another study of Kanpur region, abundance of Chlorococcales members
such as Microcystis aeruginosa, M. flos-aquae, Chroococcus minutus, C. varius,
C. minor, Aphanocapsa grevillei, A. montana, Aphanothece microscopica, and
Coelosphaerium kuetzingianum has been reported (Singh et al. 2014). The prevalence of these species indicates conditions less conducive for sensitive species.
A shift in microbial diversity, in response to human perturbations, has also been
reported in the Ganga River (Singh et al. 2013; Reddy et al. 2019). For example,
multiple drug resistance has been observed in coliform, fecal coliform, fecal streptococci, and E. coli between Fatehgarh and Kannauj (Malik et al. 1995). A large
number of multiple antimicrobial-resistant, Shiga toxin and enterotoxin-producing
E. coli and virulence traits of Enterococci have been reported in the Ganga River
near Kanpur city between Bithoor to Shuklaganj region (Lata et al. 2009). Due to
increasing human intervention, a large number of harmful bacterial species including
Bacillus, Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and
Salmonella typhi have been reported in the most polluted stretch of the river between
Kanpur and Varanasi (Singh et al. 2013).
10.3.3 Shifts in Diatom Diversity
Being fast growing, phytoplankton responds quickly to nutrient, temperature, and
light regimes. Because light and temperature do not generally observe as limiting in
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D. Jaiswal et al.
habitat modification, and generate competition for food, light, and other resources.
Singh et al. (2010) have reported that abundance of exotic fishes such as Cyprinus
carpio and Oreochromis niloticus in the Ganga River has negatively influenced the
economically important indigenous fishes such as Catla, Labeo rohita, and
Cirrhinus mrigala. Khanna et al. (2007) have reported that prolonged exposure of
fishes to deteriorated environmental conditions causes severe irreversible damage to
scale circuli and lepidonts resulting in loosening of scales.
The excessive inputs of nutrients promote phytoplankton growth. Although they
are the basis of food chain, they can be harmful to human and other vertebrates as
they release toxic substances (Ariyadej et al. 2004). At Kanpur (Jajmau),
Phormidium, Aphanocapsa, and Oscillatoria have been reported in abundance
(Singh et al. 2014). These species generally occur at places with high concentration
of nutrients. A study conducted in Varanasi region has reported negative relationship
between benthic algal biomass and DOC and a positive correlation with Secchi depth
suggesting the role of water transparency (Pandey 2013). Furthermore, large biomass of Phormidium uncinatum was reported in high DOC region. The study
suggests that the increasing DOC concentration is changing the light climate and
fate of benthic producers in the Ganga River (Pandey 2013). A point source-linked
study at Bijnor (UP) has reported the prevalence of pollution-tolerant species
Synedra, Cocconeis, Spirulina, Botryococcus, and Chlamydomonas. Sensitive species such as Cladophora and Euglena disappeared from these sites (Negi and Rajput
2013). In another study of Kanpur region, abundance of Chlorococcales members
such as Microcystis aeruginosa, M. flos-aquae, Chroococcus minutus, C. varius,
C. minor, Aphanocapsa grevillei, A. montana, Aphanothece microscopica, and
Coelosphaerium kuetzingianum has been reported (Singh et al. 2014). The prevalence of these species indicates conditions less conducive for sensitive species.
A shift in microbial diversity, in response to human perturbations, has also been
reported in the Ganga River (Singh et al. 2013; Reddy et al. 2019). For example,
multiple drug resistance has been observed in coliform, fecal coliform, fecal streptococci, and E. coli between Fatehgarh and Kannauj (Malik et al. 1995). A large
number of multiple antimicrobial-resistant, Shiga toxin and enterotoxin-producing
E. coli and virulence traits of Enterococci have been reported in the Ganga River
near Kanpur city between Bithoor to Shuklaganj region (Lata et al. 2009). Due to
increasing human intervention, a large number of harmful bacterial species including
Bacillus, Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and
Salmonella typhi have been reported in the most polluted stretch of the river between
Kanpur and Varanasi (Singh et al. 2013).
10.3.3 Shifts in Diatom Diversity
Being fast growing, phytoplankton responds quickly to nutrient, temperature, and
light regimes. Because light and temperature do not generally observe as limiting in
228
D. Jaiswal et al.