Abstract
For estimations of the ecological state of a lake and its future trends, data on seasonal and long-term variations of primary production are most necessary. The methods of in situ measurements of production are time consuming, rather complicated, and very expensive. Bio-optical model calculations provide a good alternative here. A semi-empirical model for estimating phytoplankton primary production (Arst et al., 2008, Aquatic Biology, Vol. 3, No. 1, pp. 19-30) allows calculating the vertical profiles and areal (integrated over water column) values of primary production using chlorophyll a concentration, incident irradiance, and light attenuation coefficient in the water. In the present study this model was developed further by elaborating its automated version. It enables performing rapid and greatly replicated estimations of the circumstantial variability of phytoplankton primary production at hourly intervals from morning to evening and as daily and monthly sums based on a table of initial parameters and depths. For demonstrating the practical application of the model we calculated primary production in two large eutrophic North-European lakes (Vortsjarv and Peipsi), using a database collected during four warm months in 2009 (123 days in both lakes).
Highlights
The productivity of lakes is of great importance in the estimation of their ecological state and for predicting its development in the future
These models are suitable for calculating the primary production for well-mixed lakes, where chlorophyll a (Chl a) concentration (Cchl ) and the diffuse attenuation coefficient of light do not change with depth
Quantification and verification of these models was performed using in situ measurements of primary production profiles and simultaneously measured biooptical parameters (Cchl, diffuse attenuation coefficient, incident solar irradiance, and downwelling irradiance in the wavelength range of 400–700 nm) in three turbid well-mixed Estonian lakes (Peipsi (Estonian part), Võrtsjärv, and Harku) in 2003–2005 (Arst et al, 2008a)
Summary
The productivity of lakes is of great importance in the estimation of their ecological state and for predicting its development in the future. Two versions (spectral and integral) of a semiempirical model were elaborated in Arst et al (2008a) for the calculation of the vertical profiles of primary production, P(z), in lakes These models are suitable for calculating the primary production for well-mixed lakes, where chlorophyll a (Chl a) concentration (Cchl ) and the diffuse attenuation coefficient of light do not change (or change only slightly) with depth. The data obtained proved that our models gave rather reliable estimations of primary production in the turbid, well-mixed lakes Both models allow estimation of the instantaneous primary production profiles, P(z), and the areal (water-column-integrated) production, Pint , and, their daily dynamics and daily and monthly totals. We present here quantitative estimates of the daily variability of phytoplankton primary production profiles as well as areal values (daily and monthly sums) of the production in the observed lakes as the results of the application of the automated model
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