A bio-optical model for the estimation of chlorophyll a using animal-borne instruments in an optically complex ecosystem

Abstract

Studies using marine animals instrumented with biologging devices to estimate phytoplankton biomass have typically omitted continental shelf regions due to the confounding effects of optically active constituents other than phytoplankton present. The lack of algorithms for these regions is problematic, as they are some of the most biologically productive in the world and are often inhabited by the species of interest. We developed a bio-optical model to estimate chlorophyll a concentration (chl a) using light attenuation (LA) measured using a standard oceanographic instrument in an optically complex water body that is applicable to data collected by animal-borne devices. To achieve this, we conducted a replicated experiment to compare measurements made using time-depth-light recorders (TDLRs) to those of a standard oceanographic instrument (the HyperPro) in an adjacent water body, the Bedford Basin, Nova Scotia, Canada. Measurements of LA made by TDLRs were comparable to those of the HyperPro atdepth. The best supported bio-optical model for the estimation of chl a included both LA measured by the HyperPro and season as a fixed effect. The use of animal-borne devices to collect subsurface chl a data not only provides an opportunity to collect valuable oceanographic data but also allows for the exploration of broader ecological questions relating to the influence of primary productivity on the movement patterns of wide-ranging marine species.