8 - Tropical High-Altitude Streams

Abstract

This chapter describes the features of tropical high-altitude streams, including physico-chemical conditions, primary producers and macrophytes, fishes, and macro-invertebrates. A particular aim was to describe similarities and differences in the environment, community composition, and functioning of these streams compared to streams in tropical lowlands as well as those at higher latitudes. One prominent difference between the conditions in high-altitude or alpine streams at different latitudes is the less pronounced seasonality in the tropics. Tropical streams originating at high altitudes often have better water quality than streams further down. Precipitation at very high altitudes is less than that at lower elevations. Low water temperature is the most characteristic feature of high-altitude streams. Oxygen concentration is almost constant with increasing altitude. Most alpine streams at temperate latitudes are relatively nutrient poor compared to streams at lower altitudes. The fish fauna of tropical high-altitude streams is very poor in species. The macroinvertebrates fauna in tropical high-altitude streams is dominated by insects. High-altitude streams in the tropics are affected by a number of human activities, which include contamination by pesticides, sediments from fields, livestock grazing, wastewaters from human settlements and cities, acidification and contamination with heavy metals from mining, sedimentation arising from erosion of gravel pits and construction works, reductions in stream discharge due to water abstraction, and fragmentation of longitudinal connectivity caused by dams.