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Nitrate cycling in Lake Titicaca (Peru‐Bolivia): the effects of high‐altitude and tropicality
Author(s) -
VINCENT W. F.,
VINCENT C. L.,
DOWNES M. T.,
RICHERSON P. J.
Publication year - 1985
Publication title -
freshwater biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.297
H-Index - 156
eISSN - 1365-2427
pISSN - 0046-5070
DOI - 10.1111/j.1365-2427.1985.tb00694.x
Subject(s) - hypolimnion , anoxic waters , thermocline , nitrification , water column , stratification (seeds) , nitrate , environmental science , denitrification , altitude (triangle) , transect , hydrology (agriculture) , oceanography , geology , nutrient , nitrogen , ecology , eutrophication , biology , chemistry , seed dormancy , germination , botany , geometry , organic chemistry , mathematics , geotechnical engineering , dormancy
SUMMARY.1 The vertical distribution of dissolved oxygen and inorganic nitrogen differed considerably between three stratification cycles in Lake Titicaca, a tropical lake (latitude 16°S) in the high Andes (3800 m altitude). In 1980/81 an anoxic layer of water extended from 200 to 275 m and contained high levels of NH 4 but zero NO 3 . During the annual deep mixing period in 1981 this layer was substantially eroded, and was completely eliminated during deep‐mixing in 1982. 2 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. 3 Lake Titicaca is a productive lake with low saturation levels of oxygen because of its high altitude. These features favour hypolimnetic anoxia, and thus denitrification which varies in magnitude from year to year.