INSSECT—an instrumented platform for investigating floc properties close to the seabed

A new type of tripod, INSSECT (IN situ Size and SEttling Column Tripod), designed for floc measurements in the shallow parts of the continental shelf, is described. INSSECT orientates itself into the current so that instrumentation on it faces upstream, thereby minimizing flow disturbance. The instrumentation includes a digital floc camera, a video settling column, a unique sediment trap designed for capturing flocs intact, a laser sizer, an optical backscatterance sensor, a compass and tilt meter, and a current meter. It is designed for relatively short deployments of up to 2 weeks and can be recovered, turned around, and redeployed rapidly. It was designed for use in semi-synoptic surveys of the spatial variation in floc properties such as size and settling velocity and the factors that influence them. The paper describes the various components of the INSSECT and presents selected results from the first deployments, demonstrating its ability to turn in the current and capture single flocs intact. Contrary to recent findings on the influence on settling columns on floc size, intercomparison between the video settling column and the digital floc camera reveals that the sizes are similar.

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