Contribution of Microbial Activities To Carbon Cycle In A Deep Sea Ionian Area
Abstract
Main biological process which sustain life in deep environments is the microbial uti- lization of particulated matter. Despite the well known importance of bacterial role in biogeochemical cycles, the rates of microbial processes on organic matter in the Mediterranean Sea, and in particular in the Ionian Sea, are still poorly understood. During winter 1999, water samples were collected at different depths (0-3300m) from six stations along a costal-offshore transect located at 60 miles off Cape Passero (SE Sicily) in the Ionian Sea. Measurements of chlorophyll a, bacterial abundance, ATP and POC enabled the estimation of autotrophic and bacterial contribution to the pool of particulate organic matter. Estimates of microbial leucine-aminopeptidase (LAP) and respiration rates (ETSa) were compared with different water masses identified ac- cording to temperature, salinity and nutrients. Results showed that bacterial biomass contributed to particulated carbon in percentage ranging from 4.57% in surface waters (ISW) to 1.29% in EMDW. Microbial hydrolysis of POC showed higher percentage also in ISW reaching 1.81% and potentially liberating 0.73µg C/l/h (mean values), bioavailable for bacterial growth. The lowest rates of LAP mean values (0.06µg C/l/h) were observed in EMDW with 0.16% of POC potentially hydrolysed. These hydroly- sis rates confirm that during sinking a greater amount of organic matter can not be uti- lized by bacteria and may become refractory. Respiratory rates ranged from 0.118µg C/l/h in MAW to 0.003 µg C/l/h in CDW, with a decreasing trend with depth, indicat- ing low respiration rates with respect to precedent data recorded in deep Mediterranean zones. This research tried of evaluating the carbon flux through the microbial commu- nity and contributed to study some steps of degradative process of organic matter and mineralization to CO2 in relation to the different hydrological characteristics in the Mediterranean changing environment.
- Publication:
-
EGS General Assembly Conference Abstracts
- Pub Date:
- 2002
- Bibcode:
- 2002EGSGA..27.5828Z