Does different versus equal daytime and night-time respiration matter for quantification of lake metabolism using diel dissolved oxygen cycles?

Abstract

Diel dissolved oxygen (DO) measurements can be used to estimate water metabolism of aquatic systems, in particular, lakes, lagoons and streams in terms of gross primary production (GPP), ecosystem respiration (R eco) and net ecosystem production (NEP). One of the main assumptions in the calculation of lake metabolism is that R eco is the same for daytime (R daytime) and nighttime (R darkhr). This study aimed at testing the equal R daytime and R darkhr assumption to estimate GPP, R eco and NEP in a littoral zone of a temperate shallow lake (Lake Yeniçaǧa) in northwestern Turkey with and without the assumption. Based on the equal R darkhr and R daytime assumption, values calculated for GPP and R daytime were different than those based on the different R darkhr and R daytime assumption (P<0.001). GPP was lower by 7.5% in July, 49.6% in September and 14.9% in October, while R eco was lower by 5.9% in July and 55.8% in September. GPP was higher by 8.9% in August and 55% in November, while R eco was higher by 7.8% in August and 23.9% in November. © EDP Sciences, 2011.