Quéric, N. V. University of Vienna, a8902172@unet.univie.ac.at
Mueller-Niklas, G. V. University of Vienna, gerald.mueller-niklas@univie.ac.at

 
OXYGEN DEPLETION IN FLOATING MARINE SNOW AGGREGATES AS A POTENTIAL SOURCE FOR LARGE SCALE MORTALITY IN THE SHALLOW ECOSYSTEM OF THE NORTHERN ADRIATIC SEA
 
Development of distinct zones in large floating aggregates characterized by different rates of oxygen depletion and divergent microbial activities was investigated in the northern Adriatic Sea in summer 1997. In the aggregates outer zones O2 concentration remained constant (mean=5.2mlO2l-1) close to ambient water values while in the inner zones O2 decreased significantly (mean=3.1mlO2l-1) resulting in hypoxic or anoxic conditions. Reduction of O2 was correlated with increasing dry weight values. In both zones bacterial abundance increased exponentially though mean bacterial cell density (1167x10E5cellsml-1) in the inner zone was 3 times higher than outside. Abundance of cyanobacteria increased only in the inner zone (range=38.4-170.1x10E5cellsml-1). Bacterial production increased in the outer zone significantly (mean=531.9µgCl-1d-1) but remained stable inside (mean=552.1µgCl-1d-1). DOC concentration increased in the inner zone while no tendency was found for the outer zone. There is evidence that reduced diffusion rates through the gel-matrix of the aggregates and microbial oxygen consumption lead to the development of hypoxic and anoxic zones in floating aggregates. This might have an impact on the fate of benthic organisms getting covered by sedimenting aggregates.
 
Day: Monday, Feb. 1
Time: 02:30 - 02:45pm
Location: Sweeney Center
 
Code: SS17MO0230S