Response of a humic lake ecosystem to an extreme precipitation event: physical, chemical, and biological implications

Abstract

Climate projections indicate that the frequency and severity of extreme precipitation events will increase over the next century. Although a large number of lakes across the globe are systematically monitored, it is rare to have a wide range of ecological indices measured at high enough frequency and over a sufficient time scale to allow characterisation of the response of a lake ecosystem to such events. We present data from Lough Feeagh, a relatively large oligotrophic lake in Ireland, which was at the epicentre of a once in 250-year precipitation event in July 2009 when 50 mm of rain fell in less than 2 hours. The effects of the resulting flood on the water column stability, chemistry, biology, and metabolism were examined, and data from multiple years before and after the event were used to ascertain the significance and longevity of any observed changes. The flood caused the water column to destabilise prematurely and depressed primary production. Bacterial biomass was high in the month after the flood, and zooplankton assemblages in late 2009 were significantly different from those of other years. Changes in all these variables combined to produce lower rates of gross primary production and higher rates of respiration than those measured between 2010 and 2014, resulting in more pronounced negative net ecosystem production than in the other years. Despite all these changes, the normal seasonal cycles resumed in 2010, and it appears that this rare but significant event did not have a long-term impact on the ecosystem functioning of the lake.

Storm impacts on alpine lakes: Antecedent weather conditions matter more than the event intensity

“…Overall, the effects of rainstorms and windstorms on lakes are detected through partial to total mixing of the water mass (Jennings et al, ; Klug et al, ; Tsai et al, ). Usually, the disruption of thermal stratification comes with a decrease in water transparency that is due to major inputs of terrestrial dissolved or particulate matter (de Eyto et al, ; Sadro & Melack, ; Vidon et al, ), sediment resuspension (Jennings et al, ) or lacustrine algal growth (Kasprzak et al, ). Biogeochemical effects of storms usually converge towards larger O 2 uptake or the release of CO 2 to the atmosphere; however, these effects are due to different pathways.…”

“…increase in lake surface water temperature (Austin & Colman, 2007;O'reilly, et al, 2015;Woolway et al, 2017), shorter ice cover (Magnuson et al, 2000), longer stratification length (Kraemer et al, 2015), warming-induced shift in biological assemblages (Yvon-Durocher, Montoya, Trimmer, & Woodward, 2011) or abundances (Kraemer, Mehner, & Adrian, 2017). The contribution of extreme events to the realized and projected modifications to lakes under climate change are still poorly considered (Jones, Kratz, Chiu, & Mcmahon, 2009) despite a growing body of evidence of the disproportional role of episodic meteorological disturbances and fluctuations on the physics, biogeochemistry and ecology of lakes (de Eyto et al, 2016;Giling, Nejstgaard, et al, 2017;Jennings et al, 2012;Kasprzak et al, 2017;Klug et al, 2012).…”

“…Besides, the physical and biological disturbances induced by storms can largely differ among systems (de Eyto et al, 2016;Jennings et al, 2012). Overall, the effects of rainstorms and windstorms on lakes are detected through partial to total mixing of the water mass (Jennings et al, 2012;Klug et al, 2012;Tsai et al, 2008).…”

“…Biogeochemical effects of storms usually converge towards larger O 2 uptake or the release of CO 2 to the atmosphere; however, these effects are due to different pathways. Decreased O 2 concentrations have been attributed to increasing respiration (de Eyto et al, 2016;Tsai et al, 2008) or light limitation to primary production (Sadro & Melack, 2012), while increased CO 2 could result from increased respiration of allochthonous inputs (Weyhenmeyer, Willen, & Sonesten, 2004), remobilization of hypolimnetic stores (Huotari et al, 2011;Jones et al, 2009) or direct CO 2 inputs from the watershed (Jones et al, 2009;Vachon & del Giorgio, 2014). As a counterexample, the consequences of the exceptional storm over Lake Stechlin in 2011 resulted in a net positive effect on primary production, as upwelling reinjected nutrients into the euphotic zone (Kasprzak et al, 2017).…”

13 Years of Storms: An Analysis of the Effects of Storms on Lake Physics on the Atlantic Fringe of Europe

“…It requires a long time series of high frequency data on water column temperature profiles, data archives that are scarce in Europe and globally [18]. Single storm events have been investigated before [6,13,15,16,19], some studies have investigated several storms occurring over months or few years [5,17,20,21], but to our knowledge no studies to date have looked at large numbers of storm events over many years in one lake.In the present study, we investigated the effect of storms on physical conditions in Lough Feeagh, Co. Mayo, Ireland (Figure 1), during fully mixed conditions in winter and in the stratified period in summer. We quantified the changes in a range of lake physical parameters including energy flow (heat fluxes), temperature change, water column stability and thermocline depth.…”