IMIS

Important anomalies in suspended particulate matter concentrations in the water column suggested dredging-induced overflow of sediments in the near field (i.e., dynamic plume), and settling of finer-grained material in the far field (i.e., passive plume). Capturing the latter is a successful outcome to this experiment, since the location of dispersion and settling of a passive plume is highly dependent on the ruling hydro-meteorological conditions and thus difficult to predict. Deposition of the observed sediment plumes may cause habitat changes in the long-term.

The Wave Glider (www.liquidr.com) was equipped with a fluorometer (Turner Designs, C3 submersible fluorometer), with sensors for measuring a.o. colour dissolved organic matter (CDOM) and crude and refined (poly- and mono-aromatic hydrocarbons) oil fluorescence, and for turbidity and water temperature just below the float of the Wave Glider. The fluorometer featured three optical sensors covering the spectrum from the deep ultraviolet to the infrared. The light-emitting diode for measuring turbidity from the scattering of light operated at a wavelength of 850 nm. Measured values were expressed in relative fluorescence units (RFU). Only, the turbidity data were so far further investigated. Datasets include the C3 turbidity data in RFU and converted to suspended particulate matter concentration (mgl-1) [WG-C3]

Current and acoustic backscatter data were acquired in three parts: part 1 with a vertical bin or cell size of 1 m, and glider motion removed, part 2 with a cell size of 2 m, because of an additional bottom track, and part 3 with similar settings as part 1. The primary datasets are the ADCP current data (ms-1) and error velocities, the ADCP backscatter data in counts for the three parts. And the ADCP backscatter data converted in suspended particulate matter concentration (mgl-1) [WG_ADCP_Part1; WG_ADCP_Part2; WG_ADCP_Part3]; [WG_ADCP_Part1_BS; WG_ADCP_Part2_BS; WG_ADCP_Part3_BS]; [WG_ADCP_SPM_MATRIX_ALLDATA].

Liquid Robotics (www.liquidr.com) provided the platform and sensors to conduct the experiment. The study design relates to the project MOZ4 (Flemish Authorities, Agency Maritime Services and Coast, Coast, contract 211.177). Data collection and analysis were supported by the ZAGRI contract, a continuous monitoring programme, paid from the revenues of marine aggregate extraction activities. The paper contributes also to the Brain-be project TILES (Transnational and Integrated Long-term marine Exploitation Strategies), subsidised by Belgian Science Policy under contract BR/121/A2/TILES ( www.odnature.be/tiles).