RESEARCH
Cross-habitat subsidies in high Sierra lakes
Fish predation effects on insects are well documented in Sierra lakes. No fish are endemic to lakes above 8,000 feet, but over the past hundred years many lakes have been stocked with trout species. These lakes with fish support less emerging insect biomass, leaving less food for frogs and birds and altering soil nutrient availability on the shore. However, previous studies have not investigated the potential interacting effects of climate change on insect emergence and the food chains that depend on it.
By surveying lakes with and without fish across a climate gradient in Humphreys Basin, our UCSB Young Lab team determined that trout are not the only stressor impacting insect populations. Warmer temperatures also lead to lower emergence, and may blunt the impact of predation.
Presented at the 2021 Grad Student Symposium, UCSB EEMB
Trout and climate impacts on mosquito populations
At the same study sites with and without fish across a climate gradient in Humphreys Basin, we used carbon dioxide traps to survey mosquito communities around each lake. Fish dramatically reduce the number of mosquitoes emerging from these lakes.
We are continuing to identify the mosquito species that were collected to determine whether fish predation or climate may impact mosquito community composition, and whether this may have implications for disease transmission.
Novel algal blooms in oligotrophic lakes: where and why?
Lakes in the high Sierra are classified as oligotrophic - extremely low in nutrients and organic matter. However, in recent years many of these lakes have begun experiencing blooms of stringy green algae. Interestingly, this algae shows up much more often in lakes with fish than those without.
What is driving these blooms? How might trout presence support eutrophication?
In the face of COVID research restrictions, we have begun leveraging remote sensing techniques to predict where these algal blooms might occur based on elevation, catchment size, and fish status. We look forward to ground-truthing our models in Summer 2021.
Impacts of fish barrier removal on cross-habitat subsidies
Even small dams can be a big obstacle for steelhead and other fish that travel upstream to spawn. As shown by Young Lab research in lake systems and by the literature on salmon streams, the presence or absence of these fish drives trophic interactions - both in the water and on the land around it.
At Hastings Reserve near Carmel, CA, the upcoming removal of a barrier to fish migration gives us a chance to study what happens to stream and riparian systems after the reintroduction of fish. Young Lab colleagues Michelle Lee, Kate Culhane and I are developing monitoring protocols in collaboration with Reserve Director Jen Hunter for use by courses visiting the reserve.
Students following these protocols will gain confidence in a variety of ecological research skills, deepen their connections with this sensitive California environment, and gather valuable information to improve our understanding of cross-habitat subsidies.