SURFACE COAGULATION AND MICROBIAL RESPIRATION IN RESPONSE TO LOCAL ADVECTION AND SEA STATE IN THE NORTH-ATLANTIC

Microbial respiration in the upper ocean is enhanced by the coagulation of colloidal dissolved organic carbon on bubble surfaces. This large and transient enhancement of respiration by surface coagulation is typical of both coastal and oceanic waters, but is also affected by smaller-scale factors such as sea state and the local advection of water masses. These 2 factors were in evidence during bubbling experiments carried out at 40 and 44-degrees-N in the western North Atlantic. At the beginning of a time series of experiments, natural bubbling associated with relatively high sea states (2 to 4.5 m swells under winds of 12 to 22 m s-1) allowed only a limited potential for the enhancement of respiration by bubbling in a glass column, At lower sea states later in the time series, the advection of water with different biological characteristics produced results that were similar to those from earlier studies in bubbling columns, i.e. the induction of strong and transient peak of microbial respiration. When rebubbling experiments were carried out after the initial time series, there appeared to be no further enhancement of respiration by bubbling once the initial, transient peak of respiration was generated. Together, the times series and rebubbling experiments suggest that sea state and local advection may be closely linked in their regulation of microbial respiration in the upper ocean.