Chl a fluorescence is a proxy for concentration of the
pigment; excitation was at 470 nm with emission measured
at 682 nm. Optical backscatter of particles (a proxy for
particle concentration), determined from total backscatter
minus the contribution from water, was measured at two
wavelengths and is reported as bbp(470) and bbp(700); as the
patterns are similar in this paper we report only bbp(700)
and refer to it as particulate backscatter. At recovery the
optical face of the fluorescence–backscatter sensor appeared
clean, with little to no fouling, most likely because
the glider is deployed seaward of the biologically rich shelf,
spent little time in the euphotic zone (,5%), and most time
at low temperatures and high pressures. Instrument
performance was consistent and stable across deployments
with ,2% change in light-emitting diode (LED) intensity at
a given temperature (assessed using internal LED reference
detectors); deep-water counts were also stable over each
mission. The average clearest deep-water value at 150 m
measured for an individual sensor was subtracted as