Knowledge of carbon degradation in the mesopelagic zone is necessary to better understand the marine carbon cycle and specifically processes in the biological pump. Organic particles sink from the surface ocean into the mesopelagic layer, where most of them are microbially degraded. The behavior and speed of this degradation is dependent on both the nature of the sinking substrate and the microbial community itself. In this experiment, particulate organic carbon (POC) from three carbon-14-labeled algae cultures, i.e., Thalassiosira weissflogii, Emiliania huxleyi and Tetraselmis sp., were added to mesopelagic water in triplicate carboys and observed over a period of 87 days in sampling intervals ranging from daily to weekly. Samples were taken for POC, total dissolved carbon (TDC), dissolved organic carbon (DOC), adenosine triphosphate (ATP) and bacterial abundance. Generally, at least two phases of decay were observed: an initial faster rate in the first 10 days which was followed by a period of slower decay for the remainder of the experiment. There was a significant difference in the decay rates among algal species. However, a similar amount of POC, between 7 and 12% of the initial amount, remained undecayed after three months. Our results support the notion that the initial particle composition matters in the rate of decay and determines how far particulate carbon can sink through the water column before it is remineralized.

Primary Presenter: Noah Craft, Old Dominion University (ncraf001@odu.edu)

Authors:

Noah Craft, Old Dominion University  (ncraf001@odu.edu)

Alexander Bochdansky, Old Dominion University  (ABochdan@odu.edu)