Jyoti Verma

The health of benthic diatom assemblages in lower stretch of a lesser Himalayan glacier-fed river, Mandakini

This study examines the ecological state of epilithic diatom assemblages along the lower stretch of Mandakini, a glacier-fed Himalayan river. The diatoms were sampled at four stations during winter and summer, only once in each season. Valve counts were obtained from Naphrax mounts prepared from each sample. Assemblages were recorded for each location. The software OMNIDIA Ver. 5.3 was used for computing the ecological values from the sample counts. Normally Achnanthidium spp. dominated the assemblages, except Nitzschia fonticola (Grunow) at S1 (Kund) and Encyonema minutum (Hilse in Rabh) at S4 (Rudraprayag), only during summer. The ecological values revealed that the assemblages were in β-mesosaprobic and mésotraphentic states. However, at S4, trophic state was observed to be eutraphentic. Louis Leclercq index indicated that organic pollution was nonexistent, while the anthropogenic eutrophication was low except at S2 (Tilwara) and S3 (Medanpur) in summer and was moderate at S4 in winter characterized by a lean flow. The most abundant indicator taxa for anthropogenic eutrophication are varied; Cymbella tumida (Brebisson-Van Heurck) at S1, Encyonema minutum at S2, S4 while Surirella aungusta (Kutzing) at S3. Ordination showed that the taxa indicating degradation and anthropogenic eutrophication figured as characteristic taxa at respective locations.

Ecosystem health indicators in the Ganga Basin (Uttarakhand, India): Biodiversity, spatial patterns in structure and distribution of benthic diatoms, macro-invertebrates and ichthyofauna

This is the pioneering attempt to study the spatial patterns in structure of lotic ecosystems that form the Ganga River system in the Himalaya. The diversity of source (glacier-fed [GF], snow-fed [SN] and spring-fed [SF]) and stream-size (both interrelated) across the altitudinal panorama, create numerous habitats that contribute to structural diversity. The spatial patterns in richness, density and taxonomic composition and distribution of benthic diatoms are less affected by source compared with macro-invertebrates but shows strong influence on the distribution of fish fauna that are poikiliotherms, because a glacier-fed river carries ice-cold water (usually <20°C) in contrast to normal waters in spring-fed system (22°C near snowline, 32°C in foothills). The abundance patterns of biota of lower organisation grade (diatoms, macro-invertebrates) do not differ sharply even across distant river basins as they are more influenced by proximate factors; thus the sub-basins of the Alaknanda resemble more by virtue of one basin and there is notable resemblance between distant SF Bemunda (lower Ganga basin) and SF Gomti (East Rāmgangā basin) and even the farthest Yamuna and Rāmgangā. Fish are more sensitive to temperature and current velocities that are related to altitude and hence longitudinal rather than the spatial gradients in the mountains. The lotic ecosystem of Doon Valley harbour rich and diverse diatom flora, macroinvertebrate fauna and ichthyofauna. The examination of trophic, saprobic and ecological status shows that organic pollution, degradation and anthropogenic eutrophication are non-existent in the Lesser Himalayan rivers and streams, but the fragile Doon Valley is under severe anthropogenic stress. This and habitats fragmented by hydropower projects in the major rivers has threatened the iconic game fish Himalayan mahseer in the Ganga.

Applicability and efficacy of diatom indices in water quality evaluation of the Chambal River in Central India

Diatom indices have gained considerable popularity in estimation of the trophic state and degree of pollution in lotic ecosystems. However, their applicability and efficacy have rarely been tested in Indian streams and rivers. In the present study, benthic diatom assemblages were sampled at 27 sites along the Chambal River in Central India. PCA revealed three groups of sites, namely, heavily polluted (HVPL), moderately polluted (MDPL), and least polluted (SANT). A total of 100 diatom taxa belonging to 40 genera were identified. Brachysira vitrea (Grunow) was the most abundant species recorded from the least polluted sites with an average relative abundance of 29.52. Nitzschia amphibia (Grunow) was representative of heavily polluted sites (average relative abundance 31.71) whereas moderately polluted sites displayed a dominance of Achnanthidium minutissimum (Kϋtzing) with an average relative abundance of 26.33. CCA was used to explore the relationship between diatom assemblage composition and environmental variables. Seventeen different diatom indices were calculated using diatom assemblage data. The relationship between measured water quality variables and index scores was also investigated. Most of the diatom indices exhibited strong correlations with water quality variables including BOD, COD, conductivity, and nutrients, particularly phosphate. Best results were obtained for TDI and IPS indices which showed a high level of resolution with respect to discrimination of sites on the basis of pollution gradients. Water quality maps for the Chambal River were hence prepared in accordance with these two indices. However, satisfactory results with respect to water quality evaluation were also obtained by the application of EPI-D and IGD indices. The present study suggests that TDI and IPS are applicable for biomonitoring of rivers of Central India. Diatom indices, which are simpler to use such as IGD, may be considered, at least for a coarser evaluation of water quality.

River ecosystems of the Central Highland ecoregion: Spatial distribution of benthic flora and fauna in the Plateau rivers (tributaries of the Yamuna and Ganga) in Central India

This study reveals the relationship of biotic assemblages to their environments in the Central Highland Ecoregion rivers (Ken, Paisuni and Tons). Such knowledge will enhance our predictive abilities in the ecological studies and resource management in the concerned region. Rivers of an ecoregion are expected to harbour similar flora, fauna, and communities. This hypothesis was examined by tracking the spatial variation in richness, density, and taxonomic composition of benthic diatom and macroinvertebrate assemblages in three Plateau rivers whose course lay within 3°N latitude. Taxonomic richness and density decreased with the reduction of substrate size from the headwaters to the lowlands. Cluster and ordination analyses indicate prevalence of intrabasin rather than interbasin gradients of abundance. In both assemblages, the most abundant taxon is rarely similar longitudinally or across the river sections in the ecoregion. Hence, proximate factors govern the assemblages rather than ecoregional properties (latitude, altitude). This, and the high richness of diatom flora, points to diverse assemblages from the headwater to the lowland section in each river and among the rivers of the ecoregion.

Distribution of Major Floral and Faunal Diversity in the Mountain and Upper Gangetic Plains Zone of the Ganga: Diatoms, Macroinvertebrates and Fish

Present study examines the distribution of biodiversity elements (diatom, macroinvertebrate and fish) in respect of their taxonomic richness, density, composition in the high gradient mountain zone (MZ) and low gradient plains zone (PZ) consisting PZ I (Hardwar to Allahabad) and PZ II (Allahabad to Varanasi). The richness of benthic diatom and algal flora declines with loss of substrate heterogeneity from MZ to PZ, but that of plankton, macroinvertebrate and fish, increases gradually. Diatom predominate the benthic flora in MZ but richness declines mildly in PZ. The plankton community of PZ is mildly richer in diatom flora, as share of green algae is substantial. The macroinvertebrate fauna is predominated by insects in the MZ and a combination of insects and molluscs in the PZ. Low Jaccard’s similarity and high distances among MZ and PZ I, illustrate unique flora in these zones. Since, PZ II shows greater distance from both MZ and PZ I, this zone has different biodiversity in respect of these communities. In contrast the fauna is unique in MZ, while PZ I and PZ II have relatively more similarity, less in case of macroinvertebrate but high in fish.