Widespread deoxygenation of temperate lakes

Abstract

The concentration of dissolved oxygen in aquatic systems helps regulate biodiveristy 1, 2 , nutrient biogeochemistry 3 , greenhouse gas emissions 4 , and drinking water quality 5 . The long-term declines in dissolved oxygen concentrations in coastal and ocean waters have been linked to climate warming and human activity 6, 7 , but little is known about changes in dissolved oxygen concentrations in lakes. While dissolved oxygen solubility decreases with increasing water temperatures, long-term lake trajectories are not necessarily predictable. Oxygen losses in warming lakes may be amplified by enhanced decomposition and stronger thermal stratification 8, 9 or they may increase as a result of enhanced primary production 10 . Here we analyse 45,148 dissolved oxygen and temperature profiles from 393 temperate lakes spanning 1941-2017. We find that a decline in dissolved oxygen is widespread in surface and deep-water habitats. The decline in surface waters is primarily associated with reduced solubility under warmer water temperatures, although surface dissolved oxygen increased in a subset of highly-productive warming lakes, likely due to increasing phytoplankton production. In contrast, the decline in deep waters is associated with stronger thermal stratification and water clarity losses, but not with changes in gas solubility. Our results suggest that climate change and declining water clarity have altered the physical and chemical environment of lakes. Freshwater dissolved oxygen losses are 2.5-10 times greater than observed in the world's oceans 6, 7 and could threaten essential lake ecosystem services 2,3,5,11 .

Evidence of Climate Change Based on Lake Surface Temperature Trends in South Central Chile

“…Using a different approach [4,68,69] reported warming at similar rates using in situ LSWT data for European lakes and the Great Lakes of North America. A more recent study by Jane et al [9] achieved similar results, estimating rates of 0.036 • C/year using in situ data on surface temperatures of lakes worldwide.…”

“…Nevertheless, it is interesting that around that time, much attention was given to the lake due to an increased frequency of algal blooms [63,64], the main causes of which were attributed to anthropogenic factors that influenced the water quality of the lake, which resulted in Decree 19 (2013) to protect the environmental quality of the lakes waters [65]. Recent studies indicate that warming trends in lakes, due to global warming, result in increasing oxygen loss that lead to higher phosphorous release from sediments; increasing oxygen depletion in deeper zones of lakes with thermal stratification patters [9]. The same article reported that some lakes present rising oxygen concentration near the surface with increased temperatures, particularly in lakes that have undergone nutrient enrichment from agriculture and urbanization, resulting in algal growth.…”

“…In many cases, these changes have been attributed to global warming and increases in air temperatures [4][5][6][7][8]. Recently, Jane et al [9], studied the deoxygenation of temperate lakes, using more than 45,000 oxygen and temperature profiles collected from nearly 400 lakes. The main results indicated that oxygen levels declined by 5.5% at the surface and that surface temperatures increased by 0.38 • C/decade [9].…”

“…Recently, Jane et al [9], studied the deoxygenation of temperate lakes, using more than 45,000 oxygen and temperature profiles collected from nearly 400 lakes. The main results indicated that oxygen levels declined by 5.5% at the surface and that surface temperatures increased by 0.38 • C/decade [9]. These studies have mainly used data records from the Northern Hemisphere; there are fewer observational records or satellite-based studies related to LSWT trends in the Southern Hemisphere, such that they are less well understood than LSWT trends in Northern Hemisphere lakes.…”

Long-term trend of heat waves and potential effects on phytoplankton blooms in Lake Qiandaohu, a key drinking water reservoir

“…In addition to boost phytoplankton blooms, heat waves have many adverse effects on lake ecosystem. First, enhanced stratification associated with climate warming and heat waves resulted in the deoxygenation of bottom waters and oxygen losses (Bartosiewicz et al 2019 ; Jane et al 2021 ; Zhang et al 2015 ). Thermal stratification affected the vertical distribution of dissolved oxygen and expanded the area of the hypoxic-anoxic zone.…”