Biogeochemical properties of sinking particles intercepted at three depths on the NW Atlantic margin

Three conical sediment were deployed at three depths 968 m (top trap), 1976 m (middletrap), and 2938 m (50mabove the bottom, bottom trap) - from June 27, 2004 to April 27, 2005 on the NW Atlantic margin at a water depth of 2988 m. The sediment trap carousels were programmed to open each collection cup for 23.4 days for the top trap and 14.5 days for the other two traps, resulting in total 13 samples from the top trap and 21 samples each from the middle and bottom traps. The samples were analyzed for the biogeochemical properties with various methods. Frequent occurrences of higher fluxes in deep relative to shallower sediment traps and low delta 14C values of sinking POC together provide strong evidence for significant lateral transport of aged organic matter over the margin. Comparison of biogeochemical properties such as aluminum concentration and flux, and iron concentration between samples intercepted at different depths shows that particles collected by the deepest trap had more complex sources than the shallower ones. These data also suggest that at least two modes of lateral transport exist over the New England margin. Based on radio carbon mass balance, about 30% (± 10%) of sinking POC in all sediment traps is estimated to be derived from lateral transport of re-suspended sediment. A strong correlation between delta 14C values and aluminum concentrations suggests that the aged organic matter is associated with lithogenic particles.