Southern Ocean represents a key ecosystem to understand the variability of Earth's climate as it acts as "cold sink" and "engine" of the worldwide oceanic currents. As the microbial contribution is crucial for maintaining the biogeochemical equilibrium in all ecosystems, experimental research results particularly urgent in the Antarctic Ocean where there is still few and conflicting knowledge on the interrelationships between climate variability and marine microbial biocenoses. Here, an overview on the variability of microbial biomass and activities, obtained in the Ross Sea in spring-summer periods, is reported. Coastal and pelagic areas, as well as marginal-ice-zones and/or pack-ice-zones were investigated from 1990 to 2005. Bacterioplankton biomass (imaging analysis), total microbial biomass (fractionated ATP), hydrolithic activities (LAP, b-GLU and AP estimates), bacterial production (3H-leucine uptake) and respiratory rates (ETS activity) were studied. The aims of the study are: 1) to merge the data set on microbial biomass and activities obtained in the frame of several projects performed over different time and spatial scales; 2) to define whether microbial patterns can be used as index of ecosystemic trends in relations with seasonal and/or annual variability. The main results are: o Marginal ice zones show higher respiratory levels than pack ice zones, reflecting the variability of standing stock and phytoplankton productivity. The metabolic ratios Primary Production to Respiration (PP/R) convey the ice free zones as productive systems (PP/R >1) whereas the ice covered zones appear heterotrophic systems. Extending on annual scale the above referred findings, we may assume that microbes act as sink of CO2 in spring-summer or as source of CO2 in autumn-winter, respectively; o The microbial biomass shows an increasing trend over 11 years in the study coastal area, whereas scarce variability occurred in the pelagic ones. Sporadic peaks seem to be related with peculiar microscale conditions; o A comparison between microbiological, biochemical and sedimentological data shows that the organic matter is mainly recycled within the Ross Sea continental shelf rather than exchanged with the ocean.
AN OVERVIEW ON THE VARIABILITY OF MICROBIAL BIOMASS AND ACTIVITIES IN THE ROSS SEA (ANTARCTICA) FROM 1990 TO 2005
La Ferla R;Azzaro F;Azzaro M;Maimone G;Monticelli LS;
2012
Abstract
Southern Ocean represents a key ecosystem to understand the variability of Earth's climate as it acts as "cold sink" and "engine" of the worldwide oceanic currents. As the microbial contribution is crucial for maintaining the biogeochemical equilibrium in all ecosystems, experimental research results particularly urgent in the Antarctic Ocean where there is still few and conflicting knowledge on the interrelationships between climate variability and marine microbial biocenoses. Here, an overview on the variability of microbial biomass and activities, obtained in the Ross Sea in spring-summer periods, is reported. Coastal and pelagic areas, as well as marginal-ice-zones and/or pack-ice-zones were investigated from 1990 to 2005. Bacterioplankton biomass (imaging analysis), total microbial biomass (fractionated ATP), hydrolithic activities (LAP, b-GLU and AP estimates), bacterial production (3H-leucine uptake) and respiratory rates (ETS activity) were studied. The aims of the study are: 1) to merge the data set on microbial biomass and activities obtained in the frame of several projects performed over different time and spatial scales; 2) to define whether microbial patterns can be used as index of ecosystemic trends in relations with seasonal and/or annual variability. The main results are: o Marginal ice zones show higher respiratory levels than pack ice zones, reflecting the variability of standing stock and phytoplankton productivity. The metabolic ratios Primary Production to Respiration (PP/R) convey the ice free zones as productive systems (PP/R >1) whereas the ice covered zones appear heterotrophic systems. Extending on annual scale the above referred findings, we may assume that microbes act as sink of CO2 in spring-summer or as source of CO2 in autumn-winter, respectively; o The microbial biomass shows an increasing trend over 11 years in the study coastal area, whereas scarce variability occurred in the pelagic ones. Sporadic peaks seem to be related with peculiar microscale conditions; o A comparison between microbiological, biochemical and sedimentological data shows that the organic matter is mainly recycled within the Ross Sea continental shelf rather than exchanged with the ocean.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
