Nitrate cycling in lake titicaca peru bolivia the effects of high altitude and tropicality

Vincent, W.F.; Vincent, C.L.; Downes, M.T.; Richerson, P.J.

Freshwater Biology 15(1): 31-42

1985


ISSN/ISBN: 0046-5070
DOI: 10.1111/j.1365-2427.1985.tb00694.x
Accession: 005984647

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Abstract
The vertical distribution of dissolved O2 and inorganic N differed considerably between 3 stratification cycles in Lake Titicaca, tropical lake (latitude 16.degree. S) in the high Andes (3800 m altitude). In 1980-1981 an anoxic layer of water extended from 200-275 m and contained high levels of NH4+ but zero NO3-. During the annual deep mixing period in 1981 this layer was substantially eroded, and was completely eliminated during deep-mixing in 1982. Nitrapyrin assays of nitrification demonstrated highest activity in the surface mixed layer, lowest activity just beneath the thermocline, and then increasing nitrification rates with increasing depth towards the bottom anoxic zone. Denitrification rates were slow, but detectable, in the surficial sediments of Lake Titicaca during late 1982. Much faster rates were estimated for the periods of water column anoxia. Lake Titicaca is a productive lake with low saturation levels of O2 because of its high altitude. These features favor hypolimnetic anoxia; denitrification varies in magnitude from year to year.

Nitrate cycling in lake titicaca peru bolivia the effects of high altitude and tropicality