Nutrient limitation of algal growth and nitrogen fixation in a tropical alpine lake, Lake Titicaca (Peru/Bolivia)

Wurtsbaugh, W.A.; Vincentr, W.F.; Alfaro, T.R.; Vincent, C.L.; Richerson, P.J.

Freshwater Biology 15(2): 185-195

1985


ISSN/ISBN: 0046-5070
DOI: 10.1111/j.1365-2427.1985.tb00191.x
Accession: 061830554

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Abstract
Nutrient limitation of phytoplankton growth and N2 fixation was studied during 1981-1982 in tropical, high altitude Lake Titicaca, Peru/Bolivia (16.degree. S ). In eleven 5 day in situ growth bioassays N was the most frequently limiting nutrient. NH4+ significantly stimulated C fixation or chlorophyll production in the main lake basin in 3 experiments and twice in a shallower bay. PO43- and Fe2+ stimulated C fixation once in the main basin. SiO2 and a micronutrient mixture never stimulated algal growth. N2 fixation by blue-green algae was stimulated 40-130% by PO43- and Fe2+ and inhibited by NH4+. Dissolved nutrients measured at the beginning of each bioassay indicated that N was in short supply relative to P and silicate. N limitation in Lake Titicaca is discussed relative to the geography of its drainage basin.