Element fluxes in watershed-lake ecosystems recovering from acidification: Čertovo Lake, the Bohemian Forest, 2001–2005

Abstract

Fluxes of major ions and nutrients were measured in the watershed-lake ecosystem of a strongly acidified lake, Čertovo jezero (Čertovo Lake), in the 2001 through 2005 hydrological years. Water balance was estimated from precipitation and throughfall amounts, and measured outflow from the lake. The average water input into and outflow from the watershedlake ecosystem was 1461 mm and 1271 mm (40 L km −2 s −1 ), respectively, and the water residence time in the lake averaged 662 days. The ecosystem has been recovering from acidification since the late 1980s. Still, however, Čertovo watershed was an average net source of 23 mmol m reduction, and photochemical and microbial decomposition of allochthonous organic matter were the most important in-lake H + consuming processes (215, 85, and 122 mmol H + m −2 yr −1 , respectively), while hydrolysis of Ali was the dominant H + generating process (96 mmol H + m −2 yr −1 ) in Čertovo Lake. Photochemical liberation from organic complexes was an additional in-lake source of Ali. The net in-lake retention or removal of nutrients (carbon, phosphorus, nitrogen, and silica) varied between 18% and 34% of their inputs.

Element fluxes in watershed-lake ecosystems recovering from acidification: Plešné Lake, the Bohemian Forest, 2001–2005

“…The difference in bedrock composition between the watersheds was also the most probable reason for ∼2 times higher Ca 2+ , F − , and Si concentrations, 40% higher Na + concentrations, but 50% lower Mg 2+ concentrations in the inlets of Plešné Lake in comparison with the inlets of Čertovo Lake (Tab. 2 vs. Kopáček et al, 2006).…”

“…In contrast, the watershed export of K + was lower than its deposition on the forest floor (Tab. 4), as is typical for other forest ecosystems (Johnson, 1992); a more detailed discussion is done by Kopáček et al (2006). Based on throughfall deposition, the net proton neutralization due to weathering and exchange reactions of base cations (Ca H + 18 ± 5 2 7 ± 9 5 1 ± 9 24.5 ± 3 Ca 2+…”

“…Fractionation of aluminum and iron, i.e., total (AlT, FeT), organically bound (Alo, Feo), ionic (Ali, Fei), and particulate (Alp, Fep) were obtained as described by KOPÁČEK et al (2006) Alo, Feo, and pH (KOPÁČEK et al, 2000b).…”

“…Net terrestrial and aquatic production (or consumption) of protons and the contributions of individual constituents to these processes were estimated from budgets for ions, using the equation of electroneutrality; changes in concentrations of ionic P and Si forms were neglected (for details see KOPÁČEK et al, 2006).…”

“…Since 2000, regular research on the lake has been further intensified, focusing on fluxes of major ions within the watershed and lake, water-sediment interactions, and in-lake nutrients cycles (Kopáček et al, 2000a(Kopáček et al, , 2001a. The aim of this paper is to evaluate major fluxes of ions and nutrients within the Plešné watershed-lake ecosystem in five hydrological years from 2001 through 2005, and compare them with analogous fluxes observed in the most acidified ecosystem in the Bohemian Forest, Čertovo jezero (Čertovo Lake; Kopáček et al, 2006). …”