Phenological shifts in lake stratification under climate change

Abstract

One of the most important physical characteristics driving lifecycle events in lakes is stratification. Already subtle variations in the timing of stratification onset and break-up (phenology) are known to have major ecological effects, mainly by determining the availability of light, nutrients, carbon and oxygen to organisms. Despite its ecological importance, historic and future global changes in stratification phenology are unknown. Here, we used a lake-climate model ensemble and long-term observational data, to investigate changes in lake stratification phenology across the Northern Hemisphere from 1901 to 2099. Under the high-greenhouse-gas-emission scenario, stratification will begin 22.0 ± 7.0 days earlier and end 11.3 ± 4.7 days later by the end of this century. It is very likely that this 33.3 ± 11.7 day prolongation in stratification will accelerate lake deoxygenation with subsequent effects on nutrient mineralization and phosphorus release from lake sediments. Further misalignment of lifecycle events, with possible irreversible changes for lake ecosystems, is also likely.

Four Decades of Surface Temperature, Precipitation, and Wind Speed Trends over Lakes of Greece

“…Lakes in particular are susceptible to various climate change impacts including lake warming and water level fluctuations [2,3]. Not surprisingly, scientists have provided multiple evidence of significant changes of climatedriven limnological variables that have occurred during the past few decades [4][5][6][7][8] from lakes worldwide. Apart from a significant rise of water temperature, changes in precipitation patterns and wind speed are expected to influence lake processes such as stratification, lake mixing, and eutrophication [8][9][10][11].…”

Drivers of phytoplankton responses to summer storms in a stratified lake: a modelling study

“…Trends in nutrient loading are mostly controlled by human activities, and developing countries especially may experience increasing trends (Fink et al 2018). Earlier onset of stratification with climate warming (Woolway et al 2021) causes more nutrient build-up in the hypolimnion, so if nutrients are limiting in the epilimnion, phytoplankton increase after storms may become more prominent, although this was not observed in our second numerical experiment. In lakes where nutrients are high in the epilimnion throughout the year, a wind episode that deepens the mixed layer is likely to decrease phytoplankton concentration due to dilution and reduced light availability.…”

“…Kraemer et al 2015;Pilla et al 2020) and it is likely that local trends in transparency or wind speed are at least equally important as trends in warming to determine changes in MLD (Persson and Jones 2008;Woolway et al 2019). Lastly, stratification is expected to occur earlier in the year as the climate warms (Woolway et al 2021), and this will lead to a longer separation of epilimnion and hypolimnion. Therefore, there will be a greater build-up of nutrients in the hypolimnion during the stratified period (Pettersson et al 2003;Nowlin et al 2005), which could be entrained into the mixed layer during a storm and become available for phytoplankton growth.…”

Evaluation of Macrophyte Community Dynamics (2015–2020) in Southern Lake Garda (Italy) from Sentinel-2 Data

“…The issue of the dynamics of primary producers of lake ecosystems is acquiring more and more relevance because of increasingly marked effects of climate change on the functioning of these systems [1,2]. Indeed, the progressive reduction in the availability of water resources sharpens conflicting interests on the water uses, imposing increasingly robust assessments of macroclimatic, biological, and human drivers of lacustrine biota and functions [3].…”

“…Area (km2 ) and percentage coverage of the three classes of bottom cover for each seasonal map (2015-2020): bare sediment (BS), sparse macrophytes (S RM ), and dense macrophytes (D RM ).…”