As part of the bio-optics portion of the PhilEx RIOP08 efforts during the Feb 6-28 cruise, a variety of in-line instrumentation was used to continuously analyze surface waters from the R/V Melville's uncontaminated seawater supply. These instruments monitored particle near-forward volume scattering function, particle beam attenuation and absorption spectra, particle backscattering, as well as chlorophyll and CDOM fluorescence. The specific instruments used were:
• | LISST-100X Type-B (Laser In-Situ Scattering and Transmissometer, Sequoia Scientific) - Measures laser scattering as a function of forward angle (~0.1-32°) by detection from 32 concentric light detectors. Near-forward scattering is strongly related to particle size. |
• | AC-S (absorption and attenuation meter, Wetlabs, Inc.) - Measures absorption ("a") and attenuation ("c") of light at hyperspectrally within the visible spectrum (400-750nm). |
• | BB-3 (three wavelength backscattering meter, Wetlabs, Inc.) - Measures backscattered light at three visible wavelengths. |
• | WetStar CDOM fluorometer (WET Labs, Inc.) - Uses UV excitation and measures blue emission to estimate concentration of dissolved organic material. |
• | WetStar Chlorophyll-a fluorometer (WET Labs, Inc.) - Uses blue excitation and measures red stimulated fluorescence for estimating chlorophyll biomass. |
All instruments were operated with continuous flow. A custom chamber to house the BB-3 was designed and built by Giorgio Dall'Olmo (Oregon State University) and is described in Slade et al. (in prep). Sample seawater was also diverted for ten minutes per hour through a filter (GE Osmonics Memtrex, 0.2 micron) in order to provide filtered seawater blanks. For example, these blanks can be used to estimate calibration independent particle optical properties with the AC-S, and to compensate for drift in the chlorophyll fluorometer due to fouling between cleanings (Slade et al. in prep).
An ocean color Hyperspectral Surface Acquisition System (HyperSAS, Satlantic) was also used during this cruise. The system consists of two hyperspectral radiance sensor and one hyperspectral irradiance sensor. The radiance sensors were mounted on a frame on the bow to allow simultaneous viewing of sky and sea surface. The irradiance sensor was mounted on the 03 level to capture sky irradiance. The output product of the HyperSAS system is hyperspectral remote-sensing reflectance from 400 to 800 nm.