Faculty and graduate students associated with the Rubenstein Ecosystem Laboratory conduct research in disciplines ranging from ecological stoichiometry to apex predator ecology, in ecosystems ranging from Lake Champlain to Alaska. Below is a sampling of current faculty research programs.
Carbon Concentrating Mechanisms & Harmful Blooms
Faculty: Morales-Williams Limnology Lab
Harmful blooms are increasing in frequency and intensity worldwide. These trends are attributable to a perfect storm of climate change processes, land use alteration, and nutrient inputs. Clear links exist between ambient nutrient concentrations and bloom occurrence, but drivers of the specific timing and duration of these events remain unresolved. Several groups of phytoplankton including cyanobacteria are able to actively transport bicarbonate across their cell membrane when CO2 concentrations are limiting. This may provide a competitive advantage maintaining bloom biomass when CO2 is depleted. Using stable carbon isotope analysis in 16 agriculturally eutrophic lakes, we found that CCMs appear to be triggered when water column CO2 drops below atmospheric equilibrium. This mechanism not only maintains bloom biomass, but appears to sustain an influx of atmospheric CO2 to lake surface waters.
Cyanobacteria & Food Webs
Faculty: Jason Stockwell
Cyanobacteria blooms have negative impacts on humans, and climate change is expected to exacerbate blooms. For instance, cyanobacteria are the aquatic equivalent of junk food, and are hypothesized to short circuit ecosystems by interfering with energy transfer from primary producers to upper levels of food webs. They can also produce toxins linked to liver cancer and are hypothesized to be associated with neurodegenerative diseases such as ALS. Our research examines the extent to which cyanobacteria blooms can be detrimental to the health of food webs, in particular fish, and ultimately to humans who eat the fish.
Effects of Eutrophication on Lake Carbon Cycling
Faculty: Morales-Williams Limnology Lab
Lakes are generally considered net sources of carbon dioxide to the atmosphere, but only a handful of studies have investigated CO2 flux in eutrophic and hypereutrophic lakes with autochthonous organic carbon pools. Using a combination of high frequency sensor measurements and optical organic matter characterization, we investigate the source and magnitude of inorganic carbon flux across trophic gradients. As more lakes become impacted by expanding agriculture and urbanization, understanding how eutrophic systems process, store, and export carbon will be critical to evaluating the role of lakes in global carbon cycles.
Implications of Climate Change on Large Lakes
Faculty: Jason Stockwell
A growing body of evidence suggests that the Earth’s climate is changing in a significant way. How large-lake ecosystems respond to climate change is a growing area of concern because of the many services these systems provide. We are using a combination of lab experiments, field sampling, and modeling to explore how environmental variability and climate change are likely to influence recruitment bottlenecks within cold-water fish populations, such as cisco, in the Great Lakes. Cisco and other related Coregonid species worldwide have experienced population declines due to fishing pressure and environmental changes that appear to have reduced recruitment. Understanding how organisms will adapt to climate change is critical for management agencies to maintain diverse, abundant, and healthy populations of native species.
Lake Trout Restoration & Thiamine Deficiency
Faculty: Ellen Marsden
The invasion of alewife in 2003 poses a new threat to lake trout and Atlantic salmon in Lake Champlain: alewife contain thiaminase, an enzyme that breaks down thiamine in their predators. Severe thiamine deficiency in hatchery fry causes physical and behavioral symptoms, and high mortality. We are examining whether early foraging in wild lake trout fry could restore thiamine.
Lake Trout Spawning Behavior
Faculty: Ellen Marsden
Working with Great Lakes colleagues, we are studying lake trout spawning: how they select mates, how behavior changes from daytime to nighttime, when spawning occurs, and whether sexes differ in their movement among spawning sites within and between years. We have established an acoustic telemetry array throughout Lake Champlain, and tagged 30 lake trout in 2013 to follow their movements year-round. We are also observing behavior on a single reef using a home-built remotely-operated vehicle.
Linking Biodiversity Across Ecosystem Boundaries
Faculty: Morales-Williams Limnology Lab
Terrestrial ecosystems are rapidly changing to meet the food and energy demands of a large and growing human population. Nearly half of the global terrestrial landscape is dedicated to agriculture and urban areas, contributing to biodiversity loss and alterations to global biogeochemical cycles. This simplification of our landscapes alters the quality and quantity of exported carbon and nutrients. Resultant shifts in the composition of these subsidies can affect community structure and the functional diversity of downstream aquatic ecosystems. In collaboration with Jim Cotner and Cody Sheik at the University of Minnesota, we investigate the effects of terrestrial biodiversity loss and chemical diversity of exported subsidies on downstream biodiversity and function of microbial communities.
Mysis Ecology
Faculty: Jason Stockwell
Mysids are a group of omnivorous “shrimp-like” invertebrates found in freshwater and marine environments. They exhibit diel vertical migration and play a critical role in food webs because they link benthic and pelagic habitats and communities. We study the behavior, ecology, and population structure of this important species using traditional and cutting-edge techniques including an autonomous video camera system, fatty acids, and stable isotopes. A central focus of our research is to evaluate individual variability in migration, or in other words – why do some migrate vertically while others do not.
Storm Impacts on Lakes
Faculty: Jason Stockwell
Storms can physically alter lake environments and thus are capable of altering primary producers, including the development of toxic cyanobacterial blooms and other lake processes that depend upon phytoplankton communities. The effects of storms, however, may be dependent on local features such as lake size and morphometry, productivity and watershed area. Because storm intensities and frequencies are expected to increase under climate change, how lakes respond to such disturbances is a growing area of concern - aquatic ecosystems are increasingly recognized for the services they provide, such as public and environmental health, recreation, and industry. We are working with an international team to examine the potential for storms to alter phytoplankton diversity and composition across a gradient of lake types and to explore the potential impact of these changes on ecosystem functions.
Winter Limnology
Faculty: Jason Stockwell
As precipitation patterns are altered and temperatures increase with climate change, temperate lakes may experience decreased snow cover and subsequent increased light penetration, as well as decreased ice cover. These changes may lead to higher inoculum concentrations of some phytoplankton groups (e.g. cyanobacteria) as they emerge from winter, potentially leading to higher magnitude or frequency of harmful algal blooms later in the year. We use a combination of lab work, field experiments, and quantitative methods to explore these hypotheses related to how winter severity influences plankton communities throughout the year.