L. Arvola et T. Tulonen, EFFECTS OF ALLOCHTHONOUS DISSOLVED ORGANIC-MATTER AND INORGANIC NUTRIENTS ON THE GROWTH OF BACTERIA AND ALGAE FROM A HIGHLY HUMIC LAKE, Environment international, 24(5-6), 1998, pp. 509-520
The effects of allochthonous dissolved organic matter (DOM) on the gro
wth of bacteria and algae from a highly humic lake were studied in a b
atch culture experiment. The growth rates, cell numbers, and biomasses
of bacteria were substantially higher in the presence of DOM than in
cultures without DOM. At the stationary phase of growth, 3.4-5.9% of t
he initial dissolved organic carbon (DOC) pool was consumed, and the g
rowth efficiency of bacteria varied between 18-56% depending on nutrie
nt and DOM concentration in the cultures. The addition of phosphate an
d other extra nutrients resulted in substantially higher growth of bac
teria and algae than without extra phosphate. In the presence of algae
and protozoa, the cell numbers ail bacteria declined, demonstrating b
acterial grazing by protists. Allochthonous DOM generally also enhance
d the growth of algae. In particular, two chlorophyceans (Dictyosphaer
ium and Chlamydomonas) and a diatom (Synedra berolinensis) grew better
when DOM concentration increased. However, DOM had no detectable effe
ct on the growth of Cryptomonas (Cryptophyceae). The results of this s
tudy support the hypothesis that allochthonous DOM may strongly influe
nce the structure and functioning of plankton food chains in humic lak
es. (C) 1998 Elsevier Science Ltd.