Rimet and Bouchez 2012) as biomonitoring tools for assessment of water quality in
different parts of world. The benthic diatoms have been established as a more stable
predictor of trophic state and human perturbations as they respond directly to
nutrient and carbon inputs (Pan et al. 1996). This merits attention because benthic
diatoms grow attached to a certain substrate and thereby are less influenced by lotic
forces of river ecosystems (Pandey et al. 2017). Wide distribution of diatoms
supports the suitability and universality of diatom indices to be an indicator of
eutrophy. However, such indices have been reported to be less suitable in geographical regions other than those where these were actually developed reducing the
universal applicability of diatom-based tools across the globe. Other biomonitoring
tools that have been generally used in the assessment of human impact on river
waters are biological measures of eutrophication such as algal growth and pigments
(Potapova et al. 2004). However, the relationships of algal community, chlorophyll
a, biomass, and nutrient concentrations are often influenced by environmental
factors such as climate, upstream basin size, river width, and flow (Pan et al.
1996) which question the applicability of these determinants in lotic ecosystems.
The suitability of animal organisms as biomonitor also is hampered by factors such
as mobility, feeding behavior, and position in trophic state (Rimet and Bouchez
2012).
The riverbed sediments, an important component of riverine ecosystems, are a
biologically active and comparatively stable zone, which plays an important role in
ecosystem functions including biogeochemical cycling, carbon metabolism and
sedimentation, secondary production, and nutrient and heavy metal removal from
the water column (Covitch et al. 2004). Because microbial community constitutes
the key component of detritus system and any change in their metabolism affects the
whole ecosystem processes including organic matter decomposition and nutrient
cycling, their functional and structural attributes provide an actual picture of the
health condition of an ecosystem. Studies have shown that enzyme activities can be
used as an index of microbiological functional diversity and combining enzyme
activities with other physical and chemical measurements can provide important
information regarding ecosystem stability (Nannipieri et al. 2002). The sedimentbased determinants such as the extracellular enzymes have been proved to be the
most suitable parameter for quantification of shift in ecosystem responses toward
alteration in organic matter (substrate) and heavy metals (inhibitors) (Sinsabaugh
et al. 2008; Jaiswal and Pandey 2018, 2019a).
The extracellular enzymes β-D-glucosidase, alkaline phosphatase, and protease
are used as indicator of C acquisition, P starvation, and N mineralization, respectively (Rejsek et al. 2008; Sinsabaugh et al. 2009; Duhamel et al. 2010). Similarly
the fluorescein diacetate hydrolytic essay (FDAase) is used as an indicator of overall
microbial activities (Schnürer and Rosswall 1982). The latter involves all the three
major group of enzymes (lipases, esterases, and proteases) that mediate organic
matter decomposition (Fontvieille et al. 1992). The substrate such as carbon and
nutrients cause stimulatory effect, while toxicants such as heavy metal inhibit the
activities (Sinsabaugh et al. 2008). Our multi-year and multi-scale studies confirm
these relationships validating them for the riverbed sediment of the Ganga River
10 Ecosystem Responses to Pollution in the Ganga River: Key Issues to Address. . .
237
different parts of world. The benthic diatoms have been established as a more stable
predictor of trophic state and human perturbations as they respond directly to
nutrient and carbon inputs (Pan et al. 1996). This merits attention because benthic
diatoms grow attached to a certain substrate and thereby are less influenced by lotic
forces of river ecosystems (Pandey et al. 2017). Wide distribution of diatoms
supports the suitability and universality of diatom indices to be an indicator of
eutrophy. However, such indices have been reported to be less suitable in geographical regions other than those where these were actually developed reducing the
universal applicability of diatom-based tools across the globe. Other biomonitoring
tools that have been generally used in the assessment of human impact on river
waters are biological measures of eutrophication such as algal growth and pigments
(Potapova et al. 2004). However, the relationships of algal community, chlorophyll
a, biomass, and nutrient concentrations are often influenced by environmental
factors such as climate, upstream basin size, river width, and flow (Pan et al.
1996) which question the applicability of these determinants in lotic ecosystems.
The suitability of animal organisms as biomonitor also is hampered by factors such
as mobility, feeding behavior, and position in trophic state (Rimet and Bouchez
2012).
The riverbed sediments, an important component of riverine ecosystems, are a
biologically active and comparatively stable zone, which plays an important role in
ecosystem functions including biogeochemical cycling, carbon metabolism and
sedimentation, secondary production, and nutrient and heavy metal removal from
the water column (Covitch et al. 2004). Because microbial community constitutes
the key component of detritus system and any change in their metabolism affects the
whole ecosystem processes including organic matter decomposition and nutrient
cycling, their functional and structural attributes provide an actual picture of the
health condition of an ecosystem. Studies have shown that enzyme activities can be
used as an index of microbiological functional diversity and combining enzyme
activities with other physical and chemical measurements can provide important
information regarding ecosystem stability (Nannipieri et al. 2002). The sedimentbased determinants such as the extracellular enzymes have been proved to be the
most suitable parameter for quantification of shift in ecosystem responses toward
alteration in organic matter (substrate) and heavy metals (inhibitors) (Sinsabaugh
et al. 2008; Jaiswal and Pandey 2018, 2019a).
The extracellular enzymes β-D-glucosidase, alkaline phosphatase, and protease
are used as indicator of C acquisition, P starvation, and N mineralization, respectively (Rejsek et al. 2008; Sinsabaugh et al. 2009; Duhamel et al. 2010). Similarly
the fluorescein diacetate hydrolytic essay (FDAase) is used as an indicator of overall
microbial activities (Schnürer and Rosswall 1982). The latter involves all the three
major group of enzymes (lipases, esterases, and proteases) that mediate organic
matter decomposition (Fontvieille et al. 1992). The substrate such as carbon and
nutrients cause stimulatory effect, while toxicants such as heavy metal inhibit the
activities (Sinsabaugh et al. 2008). Our multi-year and multi-scale studies confirm
these relationships validating them for the riverbed sediment of the Ganga River
10 Ecosystem Responses to Pollution in the Ganga River: Key Issues to Address. . .
237