activities (FDAase, β-D-glucosidase, protease) with C, N, and P and negative
correlations with heavy metals (Jaiswal and Pandey 2018, 2019e). Earlier studies
show significant positive correlations of heavy metals with microbial metabolic
quotient (qCO 2 ) indicating further that heavy metals are major stressors affecting
microbial activity (Wardle 1993).
These results suggest that EE activities in the riverbed sediment can be a sensitive
indicator of C, N, and P status in the river. Further, the metals accumulated in the
sediment inhibit EE activities, although C-rich sediment can reduce the toxic effects
probably by reducing the bioavailability (Jaiswal and Pandey 2018). A recent study
conducted in the Ganga River has shown that when total heavy metal concentration
(ƩTHM; a sum of six most common heavy metals (Cd, Cr, Cu, Ni, Pb, and Zn) of
human-impacted riverine systems) exceeds 347.44 μg g
À1 , it becomes detrimental to
EE activities. However, if a site has very high concentration of TOC, this limit may
reach 472.53 μg g
À1 indicating a modulatory effect of TOC in metal toxicity (Jaiswal
and Pandey 2019a). The study further shows that the stimulatory effect of substrate
on EE activities declines when ƩTHM exceeds 284.73 μg g
À1 (Jaiswal and Pandey
2019e). Thus, the EE activities can be a good indicator of river response toward
metal pollution and C eutrophy in large rivers, and the accuracy has displayed to be
higher than other biological variables (Pandey and Yadav 2017; Jaiswal and Pandey
2018, 2019e).
10.3.2 Shift in Aquatic Diversity
One of the major impacts of human-induced environmental change is the loss of
biodiversity and altered ecosystem processes. A recent global-scale study by Hooper
et al. (2012) reveals that biodiversity loss can be considered as one of the major
drivers of ecosystem change. Accordingly systematic database on interaction among
biodiversity loss, environmental change, and associated impacts on ecosystem
functioning is necessary. The Ganga River, which is under strong influence of
anthropogenic perturbations, has been identified as a system with a massive shift
in aquatic diversity and abundance. The Ganges dolphin has been an indicator
species of this river, but due to increasing pollution load, this species is now at the
boundary of extinction (Bashir et al. 2010). Dolphins are now found in some
restricted locations of the upper stretch, and even there they are under threat due to
increasing pollution and decreasing deepwater pools (Bashir et al. 2010). A sharp
decline in abundance of major carp and spawn has been reported due to massive
exploitation, habitat fragmentation, water abstraction, and increasing pollution load
(Jhingran and Ghosh 1978). Besides this, large-scale reduction in clupeid fisheries
has been reported due to increasing pollution in the river. This has increased the
pressure on other commercially important fishes, such as Aorichthys seenghala
(Sykes) and Aorichthys aor (Ham.), causing a threat to these species as well (Seth
and Katiha 2003). A study conducted by Singh and Sharma (1998) reported 14 abundant, 7 vulnerable, 15 low-risk, 1 data-deficient, and 2 endangered fish species in
10 Ecosystem Responses to Pollution in the Ganga River: Key Issues to Address. . .
227
correlations with heavy metals (Jaiswal and Pandey 2018, 2019e). Earlier studies
show significant positive correlations of heavy metals with microbial metabolic
quotient (qCO 2 ) indicating further that heavy metals are major stressors affecting
microbial activity (Wardle 1993).
These results suggest that EE activities in the riverbed sediment can be a sensitive
indicator of C, N, and P status in the river. Further, the metals accumulated in the
sediment inhibit EE activities, although C-rich sediment can reduce the toxic effects
probably by reducing the bioavailability (Jaiswal and Pandey 2018). A recent study
conducted in the Ganga River has shown that when total heavy metal concentration
(ƩTHM; a sum of six most common heavy metals (Cd, Cr, Cu, Ni, Pb, and Zn) of
human-impacted riverine systems) exceeds 347.44 μg g
À1 , it becomes detrimental to
EE activities. However, if a site has very high concentration of TOC, this limit may
reach 472.53 μg g
À1 indicating a modulatory effect of TOC in metal toxicity (Jaiswal
and Pandey 2019a). The study further shows that the stimulatory effect of substrate
on EE activities declines when ƩTHM exceeds 284.73 μg g
À1 (Jaiswal and Pandey
2019e). Thus, the EE activities can be a good indicator of river response toward
metal pollution and C eutrophy in large rivers, and the accuracy has displayed to be
higher than other biological variables (Pandey and Yadav 2017; Jaiswal and Pandey
2018, 2019e).
10.3.2 Shift in Aquatic Diversity
One of the major impacts of human-induced environmental change is the loss of
biodiversity and altered ecosystem processes. A recent global-scale study by Hooper
et al. (2012) reveals that biodiversity loss can be considered as one of the major
drivers of ecosystem change. Accordingly systematic database on interaction among
biodiversity loss, environmental change, and associated impacts on ecosystem
functioning is necessary. The Ganga River, which is under strong influence of
anthropogenic perturbations, has been identified as a system with a massive shift
in aquatic diversity and abundance. The Ganges dolphin has been an indicator
species of this river, but due to increasing pollution load, this species is now at the
boundary of extinction (Bashir et al. 2010). Dolphins are now found in some
restricted locations of the upper stretch, and even there they are under threat due to
increasing pollution and decreasing deepwater pools (Bashir et al. 2010). A sharp
decline in abundance of major carp and spawn has been reported due to massive
exploitation, habitat fragmentation, water abstraction, and increasing pollution load
(Jhingran and Ghosh 1978). Besides this, large-scale reduction in clupeid fisheries
has been reported due to increasing pollution in the river. This has increased the
pressure on other commercially important fishes, such as Aorichthys seenghala
(Sykes) and Aorichthys aor (Ham.), causing a threat to these species as well (Seth
and Katiha 2003). A study conducted by Singh and Sharma (1998) reported 14 abundant, 7 vulnerable, 15 low-risk, 1 data-deficient, and 2 endangered fish species in
10 Ecosystem Responses to Pollution in the Ganga River: Key Issues to Address. . .
227