While there is a general sense that lakes can act as sentinels of climate change, their efficacy has not been thoroughly analyzed. We identified the key response variables within a lake that act as indicators of the effects of climate change on both the lake and the catchment. These variables reflect a wide range of physical, chemical, and biological responses to climate. However, the efficacy of the different indicators is affected by regional response to climate change, characteristics of the catchment, and lake mixing regimes. Thus, particular indicators or combinations of indicators are more effective for different lake types and geographic regions. The extraction of climate signals can be further complicated by the influence of other environmental changes, such as eutrophication or acidification, and the equivalent reverse phenomena, in addition to other land-use influences. In many cases, however, confounding factors can be addressed through analytical tools such as detrending or filtering. Lakes are effective sentinels for climate change because they are sensitive to climate, respond rapidly to change, and integrate information about changes in the catchment.

https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.4319/lo.2009.54.6_part_2.2283

Lakes as sentinels of climate change

[1] Many lakes show vertical stratification of their water masses, at least for some extended time periods. Density differences in water bodies facilitate an evolution of chemical differences with many consequences for living organisms in lakes. Temperature and dissolved substances contribute to density differences in water. The atmosphere imposes a temperature signal on the lake surface. As a result, thermal stratification can be established during the warm season if a lake is sufficiently deep. On the contrary, during the cold period, surface cooling forces vertical circulation of water masses and removal of gradients of water properties. However, gradients of dissolved substances may be sustained for periods much longer than one annual cycle. Such lakes do not experience full overturns. Gradients may be a consequence of external inflows or groundwater seepage. In addition, photosynthesis at the lake surface and subsequent decomposition of organic material in the deeper layers of a lake can sustain a gradient of dissolved substances. Three more geochemical cycles, namely, calcite precipitation, iron cycle, and manganese cycle, are known for sustaining meromixis. A limited number of lakes do not experience a complete overturn because of pressure dependence of temperature of maximum density. Such lakes must be sufficiently deep and lie in the appropriate climate zone. Although these lakes are permanently stratified, deep waters are well ventilated, and chemical differences are small. Turbulent mixing and convective deep water renewal must be very effective. As a consequence, these lakes usually are not termed meromictic. Permanent stratification may also be created by episodic partial recharging of the deep water layer. This mechanism resembles the cycling of the ocean: horizontal gradients result from gradients at the surface, such as differential cooling or enhanced evaporation in adjacent shallow side bays. Dense water parcels can be formed which intrude the deep water layer. In the final section, stratification relevant physical properties, such as sound speed, hydrostatic pressure, electrical conductivity, and density, are discussed. The assumptions behind salinity, electrical conductance, potential density, and potential temperature are introduced. Finally, empirical and theoretical approaches for quantitative evaluation from easy to measure properties conclude this contribution.

https://www.eoas.ubc.ca/~mjelline/453website/eosc453/E_prints/newfer09/boehrer_stratlakeRG08.pdf

Stratification of lakes

Anaerobic ammonium-oxidizing (anammox) bacteria primarily grow by the oxidation of ammonium coupled to nitrite reduction, using CO2 as the sole carbon source. Although they were neglected for a long time, anammox bacteria are encountered in an enormous species (micro)diversity in virtually any anoxic environment that contains fixed nitrogen. It has even been estimated that about 50% of all nitrogen gas released into the atmosphere is made by these ‘impossible’ bacteria. Anammox catabolism most likely resides in a special cell organelle, the anammoxosome, which is surrounded by highly unusual ladder-like (ladderane) lipids. Ammonium oxidation and nitrite reduction proceed in a cyclic electron flow through two intermediates, hydrazine and nitric oxide, resulting in the generation of proton-motive force for ATP synthesis. Reduction reactions associated with CO2 fixation drain lectrons from this cycle, and they are replenished by the oxidation of nitrite to nitrate. Besides ammonium or nitrite, anammox bacteria use a broad range of organic and inorganic compounds as electron donors. An analysis of the metabolic opportunities even suggests alternative chemolithotrophic lifestyles that are independent of these compounds. We note that current concepts are still largely hypothetical and put forward the most intriguing questions that need experimental answers.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/1574-6976.12014

How to make a living from anaerobic ammonium oxidation.

A global rarity rank of G4 means: Apparently secure globally, though it may be quite rare in parts of its range, especially at the periphery. A state rarity rank of S2S3 means: Imperiled or Vulnerable in New York Very vulnerable to disappearing from New York, or vulnerable to becoming imperiled in New York, due to rarity or other factors; typically 6 to 80 populations or locations in New York, few individuals, restricted range, few remaining acres (or miles of stream), and/or recent and widespread declines. More information is needed to assign a single conservation status.

Long-Term Trends

Formation and stability of schwertmannite in acidic mining lakes

Water column anammox and denitrification in a temperate permanently stratified lake (Lake Rassnitzer, Germany)

Pit lakes of the Central German lignite mining district: Creation, morphometry and water quality aspects

Since the early 1960s, acid rain has affected surface waters in regions with soils low in carbonates. The acidification of whole lake districts resulted from industrial emissions distributed through the atmosphere on a regional scale. A large body of literature exists about this acidification of surface waters by acid rain, its ecological consequences, and countermeasures to restore landscape and waters (e.g., Drablos and Tollan 1980; Fleischer 1993; Steinberg and Wright 1994; Stumm 1995). The hydrochemistry and the ecological consequences were extensively described (e.g., Dillon et al. 1984), leaving the impression that all acidic lakes are anthropogenic and artificial waters that principally need to be restored, for instance by liming measures (Henrikson and Brodin 1995).

Natural and Anthropogenic Sulfuric Acidification of Lakes

Pyrite and marcasite oxidation in the consequence of lignite surface mining creates lakes with pH as low as 2 to 3, buffered by high contents of iron and aluminium. Living conditions in this extreme habitat for plants and animals are described as well as the characteristics of the pioneer settlement. The utilization of these fish-free lakes is very limited. As possibilities for a water quality improvement special recultivation methods of overburden, chemical neutralization and biological ecotechnologies are recommended.

Martin Schultze

Papers

Stratification of lakes

Water column anammox and denitrification in a temperate permanently stratified lake (Lake Rassnitzer, Germany)

Pit lakes of the Central German lignite mining district: Creation, morphometry and water quality aspects

Natural and Anthropogenic Sulfuric Acidification of Lakes

Geogenically Acidified Mining Lakes — Living Conditions and Possibilities of Restoration