Altitudinal trends in the diatoms, bryophytes, macroinvertebrates and fish of a Nepalese river system

Abstract

1. Hydrobiological changes were assessed along an altitudinal transect of eighteen to twenty-three tributaries from 6(X) to 3750 m in two adjacent river systems in east-central Nepal. The transect incorporated catchments under terraced agriculture at the lowest altitudes in the Likhu Khola, through streams in forest, alpine scrub and tundra at higher altitudes in Langtang. 2. Diatoms, bryophytes, macroinvertebrates and fish all showed pronounced altitudinal changes in assemblage composition as shown by TWINSPAN and DECORANA. A few taxa were restricted to streams at high altitude, but many more occurred only at lower altitudes where taxon richness increased substantially despite catchment disturbance by terraced agriculture. 3. Diatoms characteristic of lower altitude streams were mostly motile, epipelic or episammic Navicula and Nitzschia spp., which occur typically at greater electrolyte and nutrient concentrations. Those characteristic of higher and steeper sites included attached Fragilaria spp. and prostrate Achnanthes spp., tolerant of turbulent flow. 4. Cover by bryophytes varied within catchment type; high altitude springs supported dense mats, unlike streams fed by ice and glaciers. Taxa confined to low altitudes included those characteristic of humid subtropical conditions. 5. Invertebrate families occurring only at lower altitudes included a range of burrowers and pool dwellers. Numerically, filter feeding Hydropsychidae and Simuliidae dominated streams in terraced and forested catchments, whereas grazing baetid mayflies dominated higher altitude streams in scrub and tundra. 6. The combined density and biomass of at least six fish species in the Likhu Khola were 23-250 (per 100 m"^), and 86-1282 g wet mass (per 100 m"^), respectively. No fish were found in Langtang streams, probably because torrential headwaters prevented colonization. 7. Our data confirm that altitudinal transitions in stream biota are pronounced in the Himalaya of Nepal, but are likely to reflect a wide array of potential influences.• -in the distributions of freshwater oreanisms are undescribed. Polar, high altitude, tropical and subAlthough freshwater ecology is maturing into an tropical regions are among those known inadequately, experimental and process-orientated science, there and together they cover a large proportion of the are still large areas of the world where basic patterns earth's land surface. As a result, much ecological 309

Longitudinal patterns of macroinvertebrate communities in relation to environmental factors in a Tibetan-Plateau river system

“…Baetidae and Heptageniidae (Ephemeroptera) and Brachycentridae (Trichoptera) dominated upstream sites and Chironomidae were less abundant, which are quite similar to those in Nepalese streams (Rundle et al, 1993;Ormerod et al, 1994;Suren, 1994) at family-level composition. However, the findings are different from those in European high altitude glacial and non-glacial streams (e.g.…”

“…Nepal) (e.g. Rundle et al, 1993;Ormerod et al, 1994;Suren, 1994). The Tibetan Plateau, representing an ecologically interesting transition between the Palaearctic and Oriental region, covers an area of about 2.3 million km 2 , with an average altitude of over 4000 m a.s.l.…”

Spatio-Temporal Variations of Macro-Invertebrates in Riffles and Pools of Mardi and Vijaypur Streams Pokhara, Nepal

“…Likewise, heptageniidae, baetidae, leptophlebidae, ephemerellidae and caenidae; chironomidae, ceratopogonidae and simuliidae and hydropsychidae, psychomyidae and limnephilidae were dominant representative families belonging to ephemeroptera, diptera and trichoptera respectively. Aquatic insects, their learvae or nymphs constitute more than 85% of which ephemeroptera, trichoptera, diptera and plecoptera contributed major bulk of the total faunal composition in mid-land streams or rivers (Ormerod et al 1994, Vaidya 2002. Similar pattern of composition and order/family dominance of macro-invertebrates was observed in the present work, which could be due to complex physiohydrological characteristics and zoogeographical factors.…”

“…Some works in this field have been conducted in Nepalese waterbodies (Sharma 1975, Yadav and Rajbhandari 1982, Vaidya et al 1988, Ormerod et al 1994, Brewin et al 2000, Sharma et al 2006. …”

Distribuição ecológica de comunidades de macroalgas de ambientes lóticos do Parque Nacional de Itatiaia (RJ, MG), Brasil

“…Sheath et al (1996) e Sheath & Müller (1997) apresentaram dados sobre macroalgas de águas correntes de regiões de tundra no Ártico e áreas montanhosas esparsas têm sido investigadas na Europa (Kawecka & Eloranta 1987, Uehlinger 1991, Pfister 1992, 1993, Hieber et al 2001, Medvedeva 2001, América do Norte (Wehr 1981, Ward 1986, 1994, Meegan & Perry 1996, Vavilova & Lewis Junior 1999, Gustina & Hoffmann 2000, América do Sul (McClintic et al 2003) e Ásia (Ormerod et al 1994). No Brasil, a pesquisa em riachos de montanhas encontra-se ainda em estágio muito inicial.…”