Concentration of nutrients in selected lakes in the High Tatra Mountains, Slovakia: effect of season and watershed

Abstract

Concentrations of total phosphorus (TP), inorganic and organic nitrogen, organic matter, and chlorophyll-a were studied in ten mountain lakes at various stages of acidification, trophy, and type of watershed during each July and October from 1987 to 1990. Concentrations of TP and total organic matter were higher in July than in October . Concentrations of NH4 -N decreased and NO 3 --N increased from July to October . The relative composition of total nitrogen (TN) and its concentration were strongly dependent on the type of watershed : the lowest TN concentrations were observed in lakes with forested watersheds, increasing above the timberline and reaching maximum values in acidified lakes with rocky watersheds . In the pool of TN, nitrate was most important in lakes above the timberline (70-86% of TN), and organic nitrogen in forest lakes (> 90% of TN) . Lakes with rocky watersheds were characterized by high ratios of TN :TP (> 250 by mass) . The concentration of chlorophyll-a varied widely, from 0 .01 to 22 .6 µg 1 -1 , without any consistent change between July and October, and were P limited .

Chemical composition of the Tatra Mountain lakes: Response to acidification

“…This pattern is changed after snowmelt or heavy rains, when the lake water is diluted by large water input from the catchment area, which lowers in-lake TP concentrations. Consequently, spring TP concentrations in Popradské pleso are lower than the autumn ones, while the opposite situation (higher spring than autumn TP concentrations) is common in the other Tatra lakes (Kopáček et al, 1996).…”

“…Evidence of zooplankton presence was used as another important site selection criterion, to exclude lakes with water residence times that were too short to allow zooplankton presence . The autumn sampling period was chosen because of more stable and representative lake water chemistry compared to the spring-summer data (KOPÁČEK et al, 1996).…”

“…Forest lakes were frequently coloured and had higher concentrations of TP (8-52 µg L −1 ), COD (4-33 mg L −1 ), and TON (179-825 µg L −1 ). Because primary production and bacterial numbers of the Tatra lakes is tightly (P < 0.001) correlated with TP concentrations (Kopáček et al, 1996(Kopáček et al, , 2000, the forest lakes were more productive, with higher concentrations of chlorophyll-a (Appendix 2; 11 µg L −1 on average) and higher bacterial numbers (Kopáček et al, 2000) than the other lakes. The 1993-1994 survey confirmed our previous observations (Stuchlík, unpublished data), that the highest chlorophyll-a concentrations (> 30 µg L −1 ) were typical for Vyšné Rakytovské pleso and Čierne pleso at Vyšné Hágy with high concentrations of TP (∼50 µg L −1 ).…”

Modelling reversibility of central European mountain lakes from acidification: Part II – the Tatra Mountains

“…The low NO 3 leaching suggests steady-state conditions in DIN dose and loss (nearly complete immobilisation of DIN deposition) within catchment-lake ecosystems. In the 1980s, the highest in-lake NO 3 concentrations were as high as 56 µeq l -1 in some alpine lakes and were only slightly less than DIN concentrations in precipitation (Kopácek et al, 1996). This pattern suggested a very low ability of catchments to immobilise N. Most of the deposited NH 4 + was probably only nitrified and leached, or alternatively, an equivalent amount of NO 3 originated from the internal soil sources (mineralisation of organic N, followed by nitrification).…”

“…Such an approach can be justified by the fact that NH 4 + concentrations < 3µeq l 1 were usually found in the alpine lakes. The exceptions were rocky lakes during snowmelt, when NH 4 + concentrations up to 9 µeq l 1 were observed (Kopácek et al, 1996).…”