Response of stable isotopes (δ

Area of Science:

• Environmental Science
• Ecology
• Biogeochemistry

Background:

• Lake ecosystems function as critical bioreactors in the global carbon cycle.
• Climate change is increasing the frequency of extreme precipitation events, impacting nutrient and organic matter transport to aquatic systems.
• Understanding the effects of these events on lake food webs is crucial.

Purpose of the Study:

• To investigate the short-term impacts of an extreme precipitation event on stable isotope signatures in a subalpine lake.
• To analyze changes in water, dissolved organic matter (DOM), seston, and zooplankton following heavy rainfall.
• To assess the effects on carbon and nitrogen cycling within the aquatic food web.

Main Methods:

• Stable isotope analysis (δ2H, δ13C, δ15N, δ18O) of water, DOM, seston, and zooplankton.
• Short-term, high-resolution sampling in a subalpine lake.
• Integration of isotope hydrology, ecosystem ecology, and organic geochemistry.

Main Results:

• Excess precipitation and runoff influenced the lake's epilimnion, increasing seston δ13C values due to terrestrial organic matter and carbonate inputs.
• Settling particles after two days indicated a decoupling of carbon and nitrogen cycling.
• Zooplankton δ13C values increased post-event, while DOM δ13C remained stable, but DOM δ2H and δ18O showed significant fluctuations.

Conclusions:

• Extreme precipitation events rapidly alter subalpine lake ecosystems and food webs.
• Isotope signatures provide valuable insights into the sources and cycling of organic matter.
• This integrated approach enhances understanding of freshwater ecosystem responses to climate change impacts.