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Bottled Water

May 13, 2016

Water-collecting cylinders known as Niskin bottles stand ready, their spring-loaded caps open at both ends. Niskin bottles are most often attached to a CTD rosette sampler—a frame holding a circle of 20 or more bottles around a central core of instruments that measure conductivity (which is used to determine salinity), temperature, and depth. Oceanographers lower CTDs at multiple locations along a ship’s cruise track to measure those properties at various depths along their course. They can also signal the CTD to close bottles at selected depths, trapping water from select depths for later chemical or biological analysis. (Photo by Ellen Roosen, Woods Hole Oceanographic Institution)