Abstract
Primary production data measured by in situ (IS) and ‘simulated’ in situ (SIS) incubations were compared. To minimize differences between the two types of incubations, SIS experiments were conducted in temperature-controlled incubators in which the spectral distribution and irradiance were adjusted to approximate IS conditions. IS available irradiance (IIs) was computed from vertical attenuation of integrated surface irradiance. Vertical attenuation was estimated using a spectral irradiance model, validated by measured profiles of the vertical attenuation coefficient. IS incubations were carried out using two methods. The first involved deployment of bottles on a drifting array for whole-day (dawn to dusk) incubations. The second method employed an autonomous submersible incubation device that performed short term (<1 h) incubations at multiple depths. Differences between whole-day IS and SIS incubation estimates were attributed partially to differences between IIS and SIS-available irradiance (ISIS). Photosynthesis-irradiance (P-I) properties of IS and SIS populations from the whole-day incubations were not significantly different. P-I properties of the short-term IS and SIS populations were significantly different, although estimates of PB (mg C mg Chl−1 h−1) from contemporaneous IS and SIS incubations did not differ by >40%. Integrated water-column primary production (IPP) estimated using P-I models derived from SIS data were within 15% of IS estimates of IPP.