An autonomous bottom-transecting instrument for making long time-series measurements of phytopigment fluorescence and acoustically detectable sediment structure to abyssal depths

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The PI proposes to develop an autonomous bottom-transecting instrument, ROVER II capable of making long time-series estimates of fresh phytodetritus arriving on the sea floor. In addition, this instrument will concurrently monitor the structural features of the sediment that influence spatial and temporal heterogeneity in sediment community activity, ultimately affecting the signal to noise ratio and resolution of measurements on biogeochemical processes in the sediments. ROVER II will be capable of conducting non-invasive time-series measurements of phytopigment fluorescence as an indicator of fresh phytodetritus on the sediment surface, while imaging the same sediments acoustically to provide 3-dimensional profiles of structural features (e.g. burrows and animals). Sediment community metabolism measurements (e.g. sediment community oxygen consumption) coupled with 2-dimensional oxygen imaging studies, will be conducted on the same sediments along transects including up to 50 sites without docking, recharging, and data download. The critical questions that will be addressed with this instrument will help answer significant questions regarding pelagic-benthic coupling in the context of biogeochemical cycling. These questions include: 1) what is the quality and quantity of phytodetritus reaching the sea floor, 2) how important is irrigation (nondiffusive transport) in measuring mineralization in sediments and 3) what responses are elicited in the sediment community by the arrival of fresh detritus on the sea floor?