Lake heatwaves under climate change Woolway, R Iestyn; Jennings, Eleanor; Shatwell, Tom ...
Nature,
01/2021, Letnik:
589, Številka:
7842
Journal Article
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Lake ecosystems, and the organisms that live within them, are vulnerable to temperature change
, including the increased occurrence of thermal extremes
. However, very little is known about lake ...heatwaves-periods of extreme warm lake surface water temperature-and how they may change under global warming. Here we use satellite observations and a numerical model to investigate changes in lake heatwaves for hundreds of lakes worldwide from 1901 to 2099. We show that lake heatwaves will become hotter and longer by the end of the twenty-first century. For the high-greenhouse-gas-emission scenario (Representative Concentration Pathway (RCP) 8.5), the average intensity of lake heatwaves, defined relative to the historical period (1970 to 1999), will increase from 3.7 ± 0.1 to 5.4 ± 0.8 degrees Celsius and their average duration will increase dramatically from 7.7 ± 0.4 to 95.5 ± 35.3 days. In the low-greenhouse-gas-emission RCP 2.6 scenario, heatwave intensity and duration will increase to 4.0 ± 0.2 degrees Celsius and 27.0 ± 7.6 days, respectively. Surface heatwaves are longer-lasting but less intense in deeper lakes (up to 60 metres deep) than in shallower lakes during both historic and future periods. As lakes warm during the twenty-first century
, their heatwaves will begin to extend across multiple seasons, with some lakes reaching a permanent heatwave state. Lake heatwaves are likely to exacerbate the adverse effects of long-term warming in lakes and exert widespread influence on their physical structure and chemical properties. Lake heatwaves could alter species composition by pushing aquatic species and ecosystems to the limits of their resilience. This in turn could threaten lake biodiversity
and the key ecological and economic benefits that lakes provide to society.
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.
Historical lake water temperature records are a valuable source of
information to assess the influence of climate change on lake thermal
structure. However, in most cases such records span a short ...period of time
and/or are incomplete, providing a less credible assessment of change. In
this study, the hydrodynamic GOTM (General Ocean Turbulence Model, a
hydrodynamic model configured in lake mode) was used to reconstruct daily
profiles of water temperature in Lake Erken (Sweden) over the period
1961–2017 using seven climatic parameters as forcing data: wind speed (WS),
air temperature (Air T), atmospheric pressure (Air P), relative humidity
(RH), cloud cover (CC), precipitation (DP), and shortwave radiation (SWR).
The model was calibrated against observed water temperature data collected
during the study interval, and the calibrated model revealed a good match
between modelled and observed temperature (RMSE =1.089 ∘C). From
the long-term simulations of water temperature, this study focused on
detecting possible trends in water temperature over the entire study
interval 1961–2017 and in the sub-intervals 1961–1988 and 1989–2017, since
an abrupt change in air temperature was detected in 1988. The analysis of
the simulated temperature showed that epilimnetic temperature increased
on average by 0.444 and 0.792 ∘C per decade in
spring and autumn in the sub-interval 1989–2017. Summer epilimnetic
temperature increased by 0.351 ∘C per decade over the entire
interval 1961–2017. Hypolimnetic temperature increased significantly in
spring over the entire interval 1961–2017, by 0.148 and
by 0.816 ∘C per decade in autumn in the sub-interval 1989–2016.
Whole-lake temperature showed a significant increasing trend in the
sub-interval 1989–2017 during spring (0.404 ∘C per decade) and
autumn (0.789 ∘C per decade, interval 1989–2016), while a significant
trend was detected in summer over the entire study interval 1961–2017 (0.239 ∘C per decade). Moreover, this study showed that changes in the
phenology of thermal stratification have occurred over the 57-year period
of study. Since 1961, the stability of stratification (Schmidt stability)
has increased by 5.365 J m−2 per decade. The duration of thermal
stratification has increased by 7.297 d per decade, corresponding to an
earlier onset of stratification of ∼16 d and to a delay of
stratification termination of ∼26 d. The average
thermocline depth during stratification became shallower by ∼1.345 m, and surface-bottom temperature difference increased over time by
0.249 ∘C per decade. The creation of a daily time step water
temperature dataset not only provided evidence of changes in Erken thermal
structure over the last decades, but is also a valuable resource of
information that can help in future research on the ecology of Lake Erken.
The use of readily available meteorological data to reconstruct Lake Erken's
past water temperature is shown to be a useful method to evaluate long-term
changes in lake thermal structure, and it is a method that can be extended
to other lakes.
Lakes experience shifts in the timing of physical and biogeochemical events as a result of climate warming, and relative changes in the timing of events may have important ecological consequences. ...Spring, in particular, is a period in which many key processes that regulate the ecology and biogeochemistry of lakes occur and also a time that may experience significant changes under the influence of global warming. In this study, we used a coupled catchment–lake model forced by future climate projections to evaluate changes in the timing of spring discharge, ice-off, the spring phytoplankton peak, and the onset of stratification in a temperate mesotrophic lake. Although the model explained only part of the variation in these events, the overall patterns were simulated with little bias. All four events showed a clear trend towards earlier occurrence under climate warming, with ice cover tending to disappear at the end of the century in the most extreme climate scenario. Moreover, relative shifts in the timing of these springtime events also occurred, with the onset of stratification tending to advance more slowly than the other events and the spring phytoplankton peak and ice-off advancing faster in the most extreme climate scenario. The outcomes of this study stress the impact of climate change on the phenology of events in lakes and especially the relative shifts in timing during spring. This can have profound effects on food web dynamics as well as other regulatory processes and influence the lake for the remainder of the growing season.
Ecology under lake ice Hampton, Stephanie E.; Galloway, Aaron W. E.; Powers, Stephen M. ...
Ecology letters,
January 2017, Letnik:
20, Številka:
1
Journal Article
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Winter conditions are rapidly changing in temperate ecosystems, particularly for those that experience periods of snow and ice cover. Relatively little is known of winter ecology in these systems, ...due to a historical research focus on summer ‘growing seasons’. We executed the first global quantitative synthesis on under‐ice lake ecology, including 36 abiotic and biotic variables from 42 research groups and 101 lakes, examining seasonal differences and connections as well as how seasonal differences vary with geophysical factors. Plankton were more abundant under ice than expected; mean winter values were 43.2% of summer values for chlorophyll a, 15.8% of summer phytoplankton biovolume and 25.3% of summer zooplankton density. Dissolved nitrogen concentrations were typically higher during winter, and these differences were exaggerated in smaller lakes. Lake size also influenced winter‐summer patterns for dissolved organic carbon (DOC), with higher winter DOC in smaller lakes. At coarse levels of taxonomic aggregation, phytoplankton and zooplankton community composition showed few systematic differences between seasons, although literature suggests that seasonal differences are frequently lake‐specific, species‐specific, or occur at the level of functional group. Within the subset of lakes that had longer time series, winter influenced the subsequent summer for some nutrient variables and zooplankton biomass.
Damming alters carbon processing along river continua. Estimating carbon transport along rivers intersected by multiple dams requires an understanding of the effects of cascading impoundments on the ...riverine metabolism. We analyzed patterns of riverine metabolism and phytoplankton biomass (chlorophyll a; Chla) along a 74.4-km river reach intersected by six low-head navigation dams. Calculating gross primary production (GPP) from continuous measurements of dissolved oxygen concentration, we found a maximum increase in the mean GPP by a factor of 3.5 (absolute difference of 0.45 g C m
d
) along the first 26.5 km of the study reach, while Chla increased over the entire reach by a factor of 2.9 (8.7 µg l
). In the intermittently stratified section of the deepest impoundment the mean GPP between the 1 and 4 m water layer differed by a factor of 1.4 (0.31 g C m
d
). Due to the strong increase in GPP, the river featured a wide range of conditions characteristic of low- to medium-production rivers. We suggest that cascading impoundments have the potential to stimulate riverine GPP, and conclude that phytoplankton CO
uptake is an important carbon flux in the river Saar, where a considerable amount of organic matter is of autochthonous origin.
Lakes are significant emitters of methane to the atmosphere, and thus are important components of the global methane budget. Methane is typically produced in lake sediments, with the rate of methane ...production being strongly temperature dependent. Local and regional studies highlight the risk of increasing methane production under future climate change, but a global estimate is not currently available. Here, we project changes in global lake bottom temperatures and sediment methane production rates from 1901 to 2099. By the end of the 21st century, lake bottom temperatures are projected to increase globally, by an average of 0.86–2.60°C under Representative Concentration Pathways (RCPs) 2.6–8.5, with greater warming projected at lower latitudes. This future warming of bottom waters will likely result in an increase in methane production rates of 13%–40% by the end of the century, with many low‐latitude lakes experiencing an increase of up to 17 times the historical (1970–1999) global average under RCP 8.5. The projected increase in methane production will likely lead to higher emissions from lakes, although the exact magnitude of the emission increase requires more detailed regional studies.
Projected changes in global lake bottom water temperatures (top) drive future increases in methanogenesis rates (bottom) under different climate warming scenarios (RCPs) by the end of the 21st century. Global lake temperature simulations of the ISIMIP2b Lake Sector (1901 to 2099), were combined with an Arrhenius‐type temperature function of methanogenesis derived from lake sediment incubations. While bottom water warming in northern lakes is muted by increased water column stratification, greater warming of lake bottom waters in the tropics, combined with increased temperature sensitivity of methanogenesis at higher temperatures suggest that tropical lakes will experience the largest increases in methane production.
The intensity and frequency of storms are projected to increase in many regions of the world because of climate change. Storms can alter environmental conditions in many ecosystems. In lakes and ...reservoirs, storms can reduce epilimnetic temperatures from wind‐induced mixing with colder hypolimnetic waters, direct precipitation to the lake's surface, and watershed runoff. We analyzed 18 long‐term and high‐frequency lake datasets from 11 countries to assess the magnitude of wind‐ vs. rainstorm‐induced changes in epilimnetic temperature. We found small day‐to‐day epilimnetic temperature decreases in response to strong wind and heavy rain during stratified conditions. Day‐to‐day epilimnetic temperature decreased, on average, by 0.28°C during the strongest windstorms (storm mean daily wind speed among lakes: 6.7 ± 2.7 m s−1, 1 SD) and by 0.15°C after the heaviest rainstorms (storm mean daily rainfall: 21.3 ± 9.0 mm). The largest decreases in epilimnetic temperature were observed ≥2 d after sustained strong wind or heavy rain (top 5th percentile of wind and rain events for each lake) in shallow and medium‐depth lakes. The smallest decreases occurred in deep lakes. Epilimnetic temperature change from windstorms, but not rainstorms, was negatively correlated with maximum lake depth. However, even the largest storm‐induced mean epilimnetic temperature decreases were typically <2°C. Day‐to‐day temperature change, in the absence of storms, often exceeded storm‐induced temperature changes. Because storm‐induced temperature changes to lake surface waters were minimal, changes in other limnological variables (e.g., nutrient concentrations or light) from storms may have larger impacts on biological communities than temperature changes.
Zebra chip disease of potato is caused by the bacterial pathogen 'Candidatus Liberibacter solanacearum' and is a growing concern for commercial potato production in several countries in North and ...Central America and New Zealand. 'Ca. L. solanacearum' is vectored by the potato psyllid Bactericera cockerelli, which transmits the pathogen to several cultivated and wild solanaceaous host plants. Silverleaf nightshade (SLN), Solanum elaeagnifolium, is a common weed in the Lower Rio Grande Valley of Texas and a host for both the potato psyllid and 'Ca. L. solanacearum'. SLN plants were successfully inoculated with 'Ca. L. solanacearum' under laboratory conditions. Retention studies demonstrated that 'Ca. L. solanacearum'-infected SLN planted in the field in January 2013, concurrent with commercial potato planting, retained the pathogen under field conditions throughout the year despite extensive dieback during summer. The presence of 'Ca. L. solanacearum' was confirmed in leaves, roots, and stolons of SLN plants collected the following year using polymerase chain reaction. Acquisition assays using B. cockerelli adults also revealed that SLN retained the pathogen. Transmission studies determined that B. cockerelli can acquire 'Ca. L. solanacearum' within a 2-week acquisition access period on 'Ca. L. solanacearum'-infected SLN and subsequently transmit the pathogen to potato. These results demonstrate that SLN plants can serve as a reservoir for 'Ca. L. solanacearum', providing a source of inoculum for B. cockerelli adults colonizing potato the next season. The presence of SLN plants all year round in the LRGV makes the weed an epidemiologically important host. These findings underscore the importance of eradicating or managing SLN plants growing in the vicinity of potato fields to prevent spread of 'Ca. L. solanacearum' and damage caused by zebra chip.
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