PhD in progress

I am in my 4th year of the PhD program in Biological Sciences at University of Notre Dame. My interests span the gamut of understanding the role of abiotic and biotic factors in driving phytoplankton and benthic algae dynamics to integrating molecular and isotope data to describe energy flow in aquatic food webs. At the basis of my interests is the fundamental tenet that primary production fuels lake food webs. Changes occurring at the microbial level, the level which we can’t see with the naked eye, can cascade up the food web and alter abundance and survival of invertebrates, as well as organisms that feed upon them. Also intertwined in my work is understanding the importance of linkages among food chains and habitats. Linked ecosystems are an emerging topic in ecology, and it is important to recognize linkages, because processes occurring in one habitat may be driven by outside influences, and not entirely dependent on internal dynamics. For example, leaf litter produced by forests can end up in streams, where they become processed by microbes and are consumed by benthic invertebrates.

Right now, I am studying food webs and linkages among the various organisms in inland saline lakes. To many people, saline lakes may seem uninteresting or unimportant because they are too salty for fish to thrive, they tend to stink (thanks to tons of bacteria!), and the water is not drinkable. However, on a global scale, saline lakes contain nearly as much water by volume as their freshwater counterparts! Furthermore, saline lakes tend to occur in arid landscapes, making them attractive “oases” for a variety of migratory birds. Saline lakes are shallow, and have no outlet, and given that they are located in arid zones, this means that these ecosystems are very sensitive to changes in climatic patterns and human influences.

I am exploring the benthic ecology of the Great Salt Lake, Utah. In many shallow lakes, benthic surfaces are often covered by green mats or reef-like structures, which provide a bounty of food to resident invertebrates. Several studies in freshwater systems have shown that benthic primary production can be an important food source for pelagic zooplankton. This is especially true in clear, oligotrophic lakes that support high abundances of zooplankton. Through the use of stable isotopes of carbon and nitrogen, researchers have shown that zooplankton can feed on benthic resources, thereby “crossing” habitat boundaries.

The Great Salt Lake is the fourth largest hypersaline lake in the world, and averages 3 times saltier than the ocean. While fish cannot survive at such high salinities, the lake is home to a thriving ecosystem composed of benthic and pelagic food chains. Perhaps the organism that most typifies Great Salt Lake is the cute sea monkey, a type of crustacean called brine shrimp that inhabits the pelagic waters of the lake. Brine shrimp thrive in the lake, where they feed upon a rich algae soup. In the benthic habitat, one can find high numbers of brine fly larvae and pupae, which live on microbialites, which are like coral reefs of the Great Salt Lake. While brine shrimp and brine fly larvae are small in comparison to fish, they reach such high densities that support massive populations of migratory and resident birds that flock to the Great Salt Lake’s waters to forage. Because the lake supports such high densities of invertebrates that are an important food source for birds, the Great Salt Lake is a vital link in the Pacific Fly Way and is a designated site on the Western Hemisphere Shorebird Reserve Network.

At the basis of the GSL’s food web is the complex, diverse microbial community-the bacteria, archaea, and eukaryotic algae.

Their primary food source comes from pelagic phytoplankton. After brine shrimp hatch in March and grow and reproduce to increase their population, they overgraze their primary food source. As a result, phytoplankton levels drop to very low levels during the mid-summer months. How do brine shrimp survive after they have depleted this important resource?

The answer may lie in the benthos. Great Salt Lake contains the world’s largest known distribution of microbialites, carbonate rock structures formed by algae and bacteria, which produce high levels of primary production. While microbialites around the globe are receiving increasing attention for their high levels of microbial diversity and biogeochemical processes, I am interested in quantifying the contribution of microbialite biofilm as an alternate food source of brine shrimp.

So, to summarize, I am chasing the benthos, the unseen power horses of aquatic ecosystems. Combine the benthos with saline lakes, and we have a dynamic study system that relies on me convincing people why this stuff matters. “What even lives in saline (let alone hypersaline) lakes?” We tend to assign more value to freshwater systems; after all, they have fish, potable water, and you can recreate in them. Sure, I’ll let you have the “saline lakes have no fish and no potable water,” BUT, saline lakes contain nearly the same amount of water by volume as freshwater lakes! Furthermore, where saline lakes occur, they tend to be the dominant feature on the landscape, and they are true oases for migratory birds seeking resting and foraging habitat.

Diving down into the benthos

Great Salt Lake is my study site for my PhD research. To the naked eye, the lake may not have fish, but it contains abundant brine shrimp that swim in the water column. And, on the bottom of the lake is a vast expanse of microbialites, carbonate rock structures formed by algae and bacteria.

Microbialite and attached brine fly pupae
The research vessel that takes me on the Great Salt Lake to collect my samples
Microbialites at Bridger Bay, Antelope Island State Park, Utah
Aerial view of assisting undergraduate and myself near the railroad causeway in Great Salt Lake