A SURE (Summer Undergraduate Research Experience) Program Feature

“The effect of carbon dioxide concentration on the invasive species of crayfish faxonius rusticus and procambarus clarkii in relation to the degree of dependence on length of exposure and size of crayfish”

As part of USF’s SURE program, junior biology major Emily Siegler, under the guidance of Bill Bromer, Ph.D., is studying the effects of varying carbon dioxide concentrations on the movement of invasive species of crayfish.

Invasive Species of Crayfish

Though crayfish are native to many areas, oftentimes they enter an environment as an invasive species. An invasive species is a non-native species of plants or animals introduced to a new ecosystem where it has significant negative economic or ecological impacts on the new environments. Both P. clarkii and F. rusticus are considered invasive species in Illinois and Michigan due to their disruption of ecosystems in the states’ waterways. In addition, due to their abundance, they have begun to displace and reduce the native populations of crayfish and game fish, and their feeding habits reduce available habitats for amphibians.

Siegler’s research projects is centered upon the hypothesis that increasing the levels of dissolved CO2 in a body of water will induce movement in F. rusticus (rusty crayfish) and P. clarkii away from the source of CO2. The amount of movement will in turn be dependent on the volume of water present and the size and overall weight of the species tested.

Explaining why she chose this experiment for the SURE  program, Siegler said, “I was interested in this project because in past semesters I have done crayfish research for class assignments and I really enjoyed it! I especially liked being able to go out into the field and conduct hands-on research.”

Emily Siegler - Summer Undergraduate Research Experience at USF

Carrying Out the Experiment


F. rusticus and P. clarkii are kept in separate tanks, and each tank contains roughly the same size crayfish. In the holding tanks, there is no excess CO introduced into the water. Along with weekly water quality measurements, weekly CO2 readings are conducted. In addition, the CO2 level of the holding tank are taken before each testing period.

For testing, the crayfish are moved to a trough that allows a gradient effect to be seen in the concentration of carbon dioxide, if a gradient effect does occur. The gradient will be measured by pH, which corresponds to a carbon dioxide level. For each trial, one crayfish is placed into the testing trough and allowed to acclimate for one minute before CO2 is introduced. After the acclimation period has passed, CO2 is introduced via the airstone at increasing levels until the crayfish begins to move away from the airstone.

A Possible Solution to Combating Invasive Species of Crayfish

From the data collected from this research, a better understanding of crayfish CO2 tolerance will be understood. This knowledge can be implemented in order to help reduce and remove invasive species without invasive or harmful measures. In effect, native species can begin to flourish again. It is not a small task, but one that Siegler’s summer research will be instrumental in helping accomplish.

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