Comparison of spectral and broad-band models for computing photosynthetically absorbed radiation in turbid waters

• Published in: Boreal environment research 2006, Vol.11 (1), p.55-65
• Main Authors: ARST, Helgi, ERM, Ants, KANGRO, Kersti, NOGES, Tiina, NOGES, Peeler
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Earth sciences; Earth, ocean, space; Exact sciences and technology; Freshwater; Fundamental and applied biological sciences. Psychology; General aspects; Marine and continental quaternary; Surficial geology; Synecology
• ISSN: 1239-6095; 1797-2469

A comparison of values of photosynthetically absorbed radiation calculated with spectral and broad-band models was performed. Special attention was paid to turbid lake waters (Secchi depth ranging from 0.3 to 3 m). Ten measurement series of bio-optical characteristics were carried out in June and August 2003 at three Estonian lakes, Peipsi, Võrtsjärv and Harku. Photosynthetically absorbed radiation was calculated from measured quantum irradiance and a radiation model. The results obtained showed that in case of moderately clear waters (Secchi depth about 3 m) it is especially important to use a correct spectral model, as the errors of the broad-band model can be more than 40%–50%. For very turbid waters these errors usually do not exceed 20%. In our measurement results there was a rather remarkable variability of the bio-optical characteristics of the lakes. The relationships between depth-averaged assimilation number and primary production and between depth-integrated primary production and chlorophyll concentration could be described by polynomial functions with intercept = 0.