Reche, Isabel听1听;听Mladenov, Natalie听2听;听Ortega, Eva听3
2听Presenting Author
1听Universidad de Granada
2听INSTAAR, University of Colorado
3听Laboratoire d鈥橭ceanographie Microbienne de Banyuls
The conversion of labile dissolved organic matter (DOM) into refractory DOM has consequences for the maintenance of DOM in the water column and represents DOM that cannot be channeled to the microbial loop. Bacteria release about 15-30% of the DOM the take up as refractory DOM. Virus lytic cycles also contribute to the release DOM during bacterial lysis. Also, dust deposition may influence bacterial production and CDOM and FDOM generation in oligotrophic alpine lakes via dust inputs of nutrients and DOM to the water column. To explore the generation of colored DOM (CDOM) and fluorescent DOM (FDOM) by bacteria in an oligotrophic alpine lake of southern Spain, we analyzed the optical spectroscopic properties, UV-vis absorbance and fluorescence, of viral-sterilized and unsterilized lake water amended with a) dust and b) a cocktail of glucose, N, and P. Interestingly, bacteria, in the absence of viruses, processed more organic carbon and released greater amounts of both amino acid-like and humic like compounds. Without viruses present, the quality of organic matter with dust and glucose+N+P addition was more amino acid-like, suggesting that more labile DOM was released. The addition of dust in the absence of viruses greatly stimulated bacterial production. Given that the dust loading to alpine lakes in southern Spain is expected to increase with climate change and that alpine lakes contain low virus:bacteria ratios, the generation of more bioavailable DOM may have ecosystem-wide implications, including effects on lake productivity.