Klamath lake (Oregon) ecology

jansons jansons at ftp.botan.su.se
Sun Jan 7 23:55:35 EST 1996


In response to the question of the ecological importance of 
cyanobacteria (blue-gree algae) in Klamath lake.
The short answer is that no person can answer this question unless 
there has been a thourough analysis of the lake, before and after the 
harvesting started. 

Since I have some interest in cyanobacterial ecology and have passed by Klamath 
lake, your letter inspiried me to reply. 
The cyanobacterial species in Klamath lake is called Aphanizomenon 
flos-aquae. It belongs to the group of cyanobacteria that can fix 
nitrogen from the air and convert it to a biologically more useful 
form, like amino acids and proteins. Potentially this could give a 
large input of nutrients to the, presumably, nutrient poor lake. The 
question is whether there are any organisms present in the lake that 
can use this biomass. 
There are relatively few organisms known to feed directly on 
cyanobacteria. This could be due to the fact that they sometimes 
produce toxins, but no one has ever proven that these toxins give the 
cyanobacteria an advantage. Some isolates of Aphanizomenon flos-aquae 
are well known toxin producers.
The only pathogen I know of is a fungus that attacks the akinets 
(cyanobacterial spores) of Aphanizomenon flos-aquae.
Bacteria could benefit from the primary production of cyanobacteria, 
and these bacteria could either re-mineralise, or if they are eaten 
up, move biomass further up in the nutrient chain.
It could also be the case that biomass is just falling to the bottom, 
termed "snow". In which case the harvesting would have small or no 
input on the ecosystem.

Hope you find this contribution useful

Sven Janson
Department of Botany
Stockholm University
Sweden




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