Sondergaard, M. University of Copenhagen,

Bacterial utilization of DOC from meso-eutrophic Lake Esrum was measured as oxygen demand in long term (longer than 100 days) batch cultures in darkness and constant temperature and as the decrease of DOC in a plug-flow bioreactor. Samples were collected seasonally and at different depths. The utilization was characterized by initial fast respiration rates ranging from 2.3 to 6.6 uM oxygen/day followed by continously declining rates. Endpoints in respiration were in most cases only achieved after more than 150 days of incubation. A comparison between DOC consumption in the bioreactor and oxygen demand in batch cultures showed respiratory quotients between 0.6 and 0.8 and a general agreement of the two methods. If the respiration is recalculated to carbon equivalents the pool size of biodegradable DOC during the initial phase ranged from 14 to 70 uM. The higher values were found in the hypolimnion during stratification and decomposed over 40 days at a constant rate. The total biodegradable organic pool ranged from 60 to 110 uM, which is from 16 to 30% of the DOC present in the lake. The prolonged and slow respiration of a large biodegradable DOC pool indicated that DOC can act as a bacterial substrate reservoir for long periods without organic input from autochthonous or allochthonous sources.
Day: Thursday, Feb. 4
Time: 10:45 - 11:00am
Location: Sweeney Center
Code: SS33TH1045S