Consequences of the 2003 European heat wave for lake temperature profiles, thermal stability, and hypolimnetic oxygen depletion: Implications for a warmer world

184

202

The current prevailing theory of diel vertical migration (DVM) of zooplankton is focused largely on two biotic drivers: food and predation. Yet recent evidence suggests that abiotic drivers such as damaging ultraviolet (UV) radiation and temperature are also important. Here we integrate current knowledge on the effects of abiotic factors on DVM with the current biologically based paradigm to develop a more comprehensive framework for understanding DVM in zooplankton. We focus on ''normal'' (down during the day, up at night) DVM of holoplanktonic, primarily herbivorous zooplankton. This new transparency-regulator hypothesis differentiates between structural drivers, such as temperature and food, that vary little over a 24-h period and dynamic drivers, such as damaging UV radiation and visual predation, that show strong variation over a 24-h period. This hypothesis emphasizes the central role of water transparency in regulating these major drivers of DVM. In less transparent systems, temperature and food are often optimal in the surface waters, visual predators are abundant, and UV radiation levels are low. In contrast, in more transparent systems, vertical thermal gradients tend to be more gradual, food quality and quantity are higher in deeper waters, and visual predator abundance is often lower and damaging UV radiation higher in the surface waters. This transparency-regulator hypothesis provides a more versatile theoretical framework to explain variation in DVM across waters of differing transparency. This hypothesis also enables clearer predictions of how the wide range of ongoing transparency-altering local, regional, and global environmental changes can be expected to influence DVM patterns in both inland and oceanic waters of the world.Diel vertical migrations (DVM) of zooplankton in the world's lakes and oceans comprise some of the most widespread and massive migrations of animals on Earth. These striking migrations across strong vertical habitat gradients have inspired numerous ecological and evolutionary studies addressing mechanisms of habitat selection and consequences for species interactions. These migrations also have important implications for water quality and fisheries production as well as biogeochemical cycling. Natural and anthropogenic environmental changes, such as shifting local land use patterns and regional to global climate change, are altering water transparency and have the potential to affect DVM in lakes and oceans worldwide. The purpose of this article is to provide a common theoretical framework for understanding variation in the drivers of DVM across transparency gradients with a particular emphasis on recent advances in our understanding of the role of ultraviolet radiation (UV).Many environmental factors are recognized as providing both important proximate cues as well as ultimate consequences of adaptive significance for DVM, including light, temperature, food availability, and predation pressures (Table 1; Lampert 1989;Ringelberg 1993;Hays 2003). In spite of the wides...

Section: Discussionmentioning

confidence: 99%

Toward a more comprehensive theory of zooplankton diel vertical migration: Integrating ultraviolet radiation and water transparency into the biotic paradigm

Williamson

Fischer

Bollens

et al. 2011

184

202

“…Climate change is likely to affect the mixing conditions of lakes (King et al 1997). Longer and stronger stratification periods will result in decreased hypolimnetic oxygen concentrations (Jankowski et al 2006), thereby shortening the oxygen exposure time of sediment OC. Given the strong dependence of OC burial efficiency on oxygen exposure time, it is likely that climate change will enhance OC sequestration and hamper OC mineralization in sediments.…”

Section: Current Role Of Lakes In the Global C Cyclementioning

confidence: 99%

Lakes and reservoirs as regulators of carbon cycling and climate

Tranvik

Downing

Cotner

et al. 2009

2,123

1,765

We explore the role of lakes in carbon cycling and global climate, examine the mechanisms influencing carbon pools and transformations in lakes, and discuss how the metabolism of carbon in the inland waters is likely to change in response to climate. Furthermore, we project changes as global climate change in the abundance and spatial distribution of lakes in the biosphere, and we revise the estimate for the global extent of carbon transformation in inland waters. This synthesis demonstrates that the global annual emissions of carbon dioxide from inland waters to the atmosphere are similar in magnitude to the carbon dioxide uptake by the oceans and that the global burial of organic carbon in inland water sediments exceeds organic carbon sequestration on the ocean floor. The role of inland waters in global carbon cycling and climate forcing may be changed by human activities, including construction of impoundments, which accumulate large amounts of carbon in sediments and emit large amounts of methane to the atmosphere. Methane emissions are also expected from lakes on melting permafrost. The synthesis presented here indicates that (1) inland waters constitute a significant component of the global carbon cycle, (2) their contribution to this cycle has significantly changed as a result of human activities, and (3) they will continue to change in response to future climate change causing decreased as well as increased abundance of lakes as well as increases in the number of aquatic impoundments.

“…Such extreme weather events have occurred recently across North America and Europe and are expected to increase in frequency and severity (Hurrell 1995). In particular, simulation models from the Canadian Centre for Climate Modeling and Analysis Centre show that climatic variation will become pronounced over boreal regions (Jankowski et al 2006). Lakes may warm or cool depending on the magnitude and direction of change in air temperatures coupled with thermal absorption and retention properties (Tanentzap et al 2008).…”

mentioning

confidence: 99%

Extreme weather events alter planktonic communities in boreal lakes

Graham

Vinebrooke

2009

Climate warming has been shown to increase the frequency of extreme weather effects on small lakes by increasing the variability of terrigenic inputs and surface water temperatures. We hypothesized that the effect of thermal variability on boreal plankton depends on dissolved terrigenic matter (i.e., temperature-terrigenic interaction). A two-factor mesocosm (1500-L capacity) experiment consisting of three terrigenic treatment levels (control, [2] runoff, [+] runoff) and three temperature treatment levels (control, warm, and cold) was conducted in triplicate for a total of 27 mesocosms deployed in Lake 302S of the Experimental Lakes Area in Canada. The warming treatment amplified the positive effect of terrigenic amendment on total phytoplankton biomass by stimulating large (.35-mm Greatest Axial Linear Dimension; GALD) taxa during the 50-d experiment. In comparison, removal of terrigenic matter increased the abundance of smaller (,35-mm GALD) phytoplankton along with copepods and cladocerans under cold and warm conditions, respectively. We also attempted to corroborate our experimental findings by comparing planktonic communities collected from reference Lake 239 during climatically contrasting summers between 1970 and 2001. Although planktonic communities in Lake 239 also differed significantly between years characterized by cold, wet vs. warm, dry ice-free conditions, their responses ran opposite to those detected during the experiment, highlighting the potential overriding importance of other scale-dependent factors (e.g., fish predation, vertical migration) mediating the effects of climate on lake communities.