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Dystrophic Lakes
Dystrophic lakes, also known as humic lakes, are lakes that contain high amounts of
Classification of Dystrophic Lakes
The main
Chemical Properties
Dystrophic lakes have a high level of dissolved organic carbon (DOC). DOC contains organic carboxylic and phenolic acids, which keeps water pH levels relatively stable by acting as a natural buffer. Therefore, the lake’s naturally acidic pH is largely unaffected by industrial emissions. DOC also reduces the entry of UV radiation and can reduce the bioavailability of heavy metals by binding them.[5] There is a significantly lowered calcium content in the water and sediment of a dystrophic lake when compared with a regular lake.[1] Essential fatty acids like EPA and DHA are still present in the organisms in humic lakes, but are downgraded in nutritional quality by this acidic system due to the high numbers of low quality producers such as phytoplankton.[6] HDI (Hydrochemical Dystrophy Index) is a scale used to evaluate the dystrophy level of lakes. In 2016, Gorniak proposed a new set of rules for evaluating the HDI of a lake, using properties such as the surface water pH, electric conductivity, level of dissolved inorganic carbon (DIC), and level of dissolved organic carbon (DOC).[7] As dystrophia is a descriptor attributed to other trophic levels, differences in chemical composition can be expected when comparing different types of dystrophically labelled lakes. [4] Studies of the chemical composition of dystrophic lakes have shown heightened levels of dissolved inorganic nitrogen and higher activities of lipase and glucosidase in polyhummic lakes when compared with oligohumic lakes. In the surface microlayers of the lake waters, there are higher levels of phosphatase activity than in the subsurface microlayers when the lake is oligohumic. The opposite is true when the lake is polyhumic. Both oligohumic and polyhumic lakes show higher aminopeptidase activity in the subsurface microlayers than in the surface microlayers.[3]
Life in Dystrophic Lakes
The
Dystrophic Lakes and Climate Change
Lakes are commonly known to be important sinks in the carbon cycle. Due to their high levels of dissolved organic carbon, dystrophic lakes are significantly larger carbon sinks than clear lakes.[11] The heightened levels of carbon concentrations in humic lakes can partially be explained by vegetation patterns in the catchment area, whose runoff greatly impacts the composition of the lakes because it is the main source of organic material. However, changes in these levels can also be attributed to shifts in precipitation, modifications of soil mineralization rates, reduced sulphate deposition, and changes in temperature. Changes in these factors can all be attributed to climate change. The creation of a humic lake via organic runoff has dire consequences for the ecosystem as a whole. Chemical composition changes that increase the lake’s acidity make it difficult for fish and other organisms to proliferate. The quality of the lake for use as drinking water also decreases as the carbon concentration and acidity increase. The fish that do adapt to the increased acidity may also not be fit for human consumption, as the organic pollutants and mediation of heavy metal concentrations is also impacted by the changes in chemical composition of a humic lake.[12]
Examples of Dystrophic Lakes
Examples of dystrophic lakes that have been studied by scientists include Lake Suchar II in Poland, and lakes Allgjuttern, Fiolen, and Brunnsjön in Sweden.[1][7]
References
- ^ a b c d e f Drzymulska, D., Fiłoc, M., Kupryjanowicz, M., Szeroczyńska, K., & Zieliński, P. 2015. Postglacial shifts in lake trophic status based on a multiproxy study of a humic lake. Holocene, 25(3), 495-507
- ^ a b Jasser, I. 1997. The dynamics and importance of picoplankton in shallow, dystrophic lake in comparison with surface waters of two deep lakes with contrasting trophic status. Hydrobiologia, 342/343(1), 87-93
- ^ a b Kostrzewska-Szlakowska, I. 2017. Microbial Biomass and Enzymatic Activity of the Surface Microlayer and Subsurface Water in Two Dystrophic Lakes. Polish Journal of Microbiology, 66(1), 75-84
- ^ a b Kostrzewska-Szlakowska, I, Jasser, I. 2011. Black box: what do we know about humic lakes? Polish Journal of Ecology, 59(4), 647-664
- ^ Korosi, J. B. and Smol, J. P. 2012. Contrasts between dystrophic and clearwater lakes in the long-term effects of acidification on cladoceran assemblages. Freshwater Biology, 57(1), 2449–2464
- ^ Taipale, S.J, Vuorio, K, Strandberg, U, et al. 2016. Lake eutrophication and brownification downgrade availability and transfer of essential fatty acids for human consumption. Environment International, 96(1), 156-166
- ^ a b Górniak, A. 2016. A new version of the Hydrochemical Dystrophy Index to evaluate dystrophy in lakes. Ecological Indicators, 78(1), 566-573
- ^ Drakare, S, Blomqvist, P, Bergstro, A, et al. 2003. Relationships between picophytoplankton and environmental variables in lakes along a gradient of water colour and nutrient content. Freshwater Biology, 48(1), 729-740
- ^ a b Newton, R.J. et al. 2006. Microbial community dynamics in a humic lake: differential persistence of common freshwater phylotypes. Environmental Microbiology, 8(6), 956-970
- ^ Salonen, K, and Jokinen, S. 1988. Flagellate grazing on bacteria in a small dystrophic lake. Hydrobiologia, 161(1), 203-209
- ^ Sobek, S. et al. 2006. A Carbon Budget of a Small Humic Lake: An Example of the Importance of Lakes for Organic Matter Cycling in Boreal Catchments. Ambio, 35(8), 469-475
- ^ Larsen, S., Andersen, T., and Hessen, D. O. 2010. Climate change predicted to cause severe increase of organic carbon in lakes. Global Change Biology, 17(2), 1186-1192
Category:Lakes by type Category:Aquatic ecology Category:Limnology