Fig. 3. Modeled depth of a constant light level (isolume) set to be the depth limit of copepod light-mediated behavior in Kongsfjorden.

Underwater spectral scalar irradiance [E_o(λ), μmol photons m⁻² s⁻¹] was weighted by the spectral response of C. finmarchicus to yield a photometric quantity of Calanus-utilized light that is shown in colored contours as a function of depth at 30-min intervals on the 23 January Jetyak deployment. White horizontal lines show the depth of an isolume at 5 × 10⁻⁸ μmol photons m⁻² s⁻¹ of Calanus-utilized light. UTC, coordinated universal time.