ibclogo XVI International Botanical Congess

Abstract Number: 4388
Poster No. = 2037


EFFECT OF LIGHT AND NITRATE CONCENTRATION ON DISSOLVED ORGANIC MATTER RELEASE BY Cryptomonas obovata (CRYPTOPHYCEAE)


Giroldo, D. and Vieira, A. A.H. (Dept. of Botany, Federal University of São Carlos, Brazil, 13565-905)


Carbon loss and dissolved organic matter (DOM) release by a tropical strain of Cryptomonas obovata (Cryptophyceae) under various PFD values and two nitrate concentrations (O ?M and 100 ?M) were evaluated by experiments carried out using axenic batch cultures. Particulate organic 14C loss previously assimilated at Ik (180 ?mols. m-2 . s-1) was statistically significant only at 2000 ?mols. m-2 . s -1 . Also, release of DOM was low at this PFD value and no photoinhibition of carbon assimilation was detected at 2000 ?mols. m-2 . s -1 . Nitrate depletion increased the relative excretion of DOM from 6% to 20%. Starved cells assimilated less 14C than replete cells. The results are in agreement with environmental conditions of a flood plain oxbow lagoon from which the C. obovata was isolated.

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