Castle Lake Projects

Investigating climate and fish stocking regime as drivers of food web interactions and ecosystem production.

Project summary:

Aquatic ecologists have long been interested in understanding the drivers of ecosystem production (i.e algae, fisheries etc.). Recently ecologists have started to quantify the contributions of intra aquatic habitat (benthic to pelagic) and interhabitat (terrestrial to aquatic habitat) drivers (nutrients and carbon) to production over time (Vadeboncouer et al. 2003, Power 2001, Nakano, 2001). Data from research programs with longer-term data sets may be used to quantify these interchanges if their sampling programs are designed to capture these dynamics. In 2007 the University of Nevada-Reno initiated a collaboration with the University of California-Davis to co-manage the Castle Lake Long-Term Research Program. The primary objective for this collaboration was to investigate these reciprocal carbon exchanges and their role in supporting lake, and specifically fisheries productivity through a) expanding the existing Castle Lake pelagic monitoring program to capture carbon exchange (primarily invertebrates) between aquatic and terrestrial habitats and b) creating an empirical model of the Castle Lake food web that would leverage the Castle Lake Long-term dataset to investigate productivity drivers. The first two years of this collaborative effort produced preliminary results suggesting that climate and stocked piscivorous fish population act as key drivers of annual primary productivity in Castle Lake. Additionally, annual stocking practices appear to be correlated with decreased density and altered species composition of emerging aquatic invertebrates subsidizing the riparian and terrestrial foodwebs.

This project continues this collaboration, building on the research and modeling work accomplished to date. In this phase, we expand long-term monitoring at Castle Lake, refine our research on cross-habitat subsidies and the recently developed empirical model that explores the influence of climate and fish stocking on lake productivity to determine future scenarios for climate change on subalpine lakes.

Specifically the goals of this second phase of the study are to determine 1) whether fish stocking affects shallow vs. deep water invertebrate production and biodiversity, 2) whether affects from fish stocking on shallow versus deep water benthic invertebrates affects emergence and thus transport of carbon to the terrestrial environment, and 3) how ecosystem productivity at Castle Lake would shift in response to climate change scenarios and altered stocking regimes. A secondary objective is to use this project as a template for collaborative research to understand the long-term drivers of watershed and climate affects on lake ecosystem production.

Project Hypotheses/ Objectives:

The primary goal of this second phase of our study is to refine an empirical model of the aquatic and riparian food-web for the Castle Lake basin that is sensitive to spatial (within lake) and temporal variation, spans trophic dynamics from nutrient input through upper level consumption, includes subsidies across aqua-terrestrial habitats, and captures the influence climate and stocking practices as drivers of productivity. An additional goal of this phase is to model changes to lake production under different climate scenarios and stocking regimes.

We hypothesize that

  1. terrestrial carbon provides a significant input to the benthic and pelagic food-web in Castle Lake from the detrital level through top level fish production:
  2. fish stocking significantly decreases total aquatic invertebrate production but has spatially (shallow vs. deep water) and temporally variable effects at the sub habitat level;
  3. aquatic carbon sources (primarily invertebrates) provide a significant, spatially and temporally variable contribution to terrestrial carbon;
  4. climate change and stocking practices act as dominant drivers of within lake ecosystem productivity