Marine Aggregates – Natural and Oiled Material Transport in the Deep Gulf of Mexico

The formation of marine aggregates, a known pathway for the transport of material from the surface ocean to the deep sea, has become the focus of recent studies that address the fate of the missing oil in the oil budget of the 2010 BP oil spill. High Resolution digital images taken by deep sea camera systems that capture time series pictures of known volumes of water, either moored at a specific depth in the water column or lowered at a constant rate through the water column, reveal the complex structure of this material delivery process to the deep sea. This study, a part of the ECOGIG consortium, funded by the Gulf of Mexico Research Initiative, reports on the data collected by these cameras near a natural hydrocarbon seep in the Gulf of Mexico. Point source vertical profiles consisting of images of aggregate abundance and year-long time series measurements of accumulation and settling speeds of marine aggregates were collected. Combined with current data from ADCPs and time series data from sediment traps deployed in the same mooring, these data reveal a high resolution record of the vertical transfer of material to the sea floor. Resuspension events, evident as increased lithogenic material flux collected in the sediment traps, are documented as “snow storms” of material arriving in the settling chamber of the moored camera. Time series images of the material settling through the water column, taken by the moored camera, provide size specific settling speeds, which allow the calculation of material densities, based on size and settling speed. Combining these settling speeds with the material compositionderived from the samples of the time series sediment traps, allow first insights in the delivery process and the dynamic behavior of the transport of oiled and natural aggregates near the seafloor in the deep Gulf of Mexico.