||A dual-optical-sensor that carries a single-wavelength chlorophyll fluorometer (470nm ex/695nm em) and backscattering sensor (700 nm) designed to measure chlorophyll and particle concentration. The instrument is capable of various combinations of backscatter, turbidity and fluorescence measurements. These include blue, green or red scattering, Chlorophyll-a, FDOM, Phycocyanin, Phycoerythrin, or Rhodamine fluorescence. It operates by using blue (470nm) and red (700 nm) LEDs that alternately flash. The blue LED stimulates chlorophyll fluorescence in plants while the red light illuminates the total particle field. It features active anti-fouling due to its copper faceplate and wiper, plus internal batteries, enabling long-term deployments. It also produces real-time data outputs. The fluorometer can typically measure phytoplankton concentrations in the range 0-30 ug/l, with a sensitivity of 0.025 ug/l. The backscattering sensor can measure within the range 0-3 m-1, with a sensitivity of 0.002 m-1. It is rated to 6000m depth.