The invasion of zebra and quagga mussels in the Great Lakes is taking a toll on the ecosystem. To investigate these ecological changes, scientists from GLERL and the Cooperative Institute for Great Lakes Research (CIGLR) are doing experimentation on how quagga mussels affect the lower food web by filtering large amounts of phytoplankton out of the water. Scientists are also investigating how mussel feeding and excretion of nutrients drive harmful algal blooms (HABs) in growth stimulation, extent, location, and toxicity.
The following experimental activities are being conducted under controlled conditions to look for changes in living and nonliving things in the water before and after quagga mussel feeding.
Scientists are using quagga mussels captured from Lakes Michigan and Erie to understand how invasive mussels impact the lower food web. Prior to experimentation, the mussels are housed in cages where they graze on phytoplankton in water kept at the same temperature as the lakes. This helps acclimate them to natural lake conditions.
The research team, led GLERL’s Hank Vanderploeg (front right), coordinates the different phases of the experiment. By filtering water before and after quagga mussel feeding, team members learn about the effect of these mussels on levels of phytoplankton (as measured by chlorophyll), nutrients (phosphorus and nitrogen), particulate matter, carbon, bacteria, and genetic material.
CIGLR research associates, Glenn Carter and Paul Glyshaw, pour lake water into sample bottles for processing at different stages of the experiment.
GLERL’s, Joann Cavaletto, pours lake water from the graduated cylinder into the filter funnel. She is filtering for particulate phosphorus samples. She also measures total chlorophyll and fractionated chlorophyll based on 3 size fractions; >20 µm, between 20 µm and 2 µm, and between 2 µm and 0.7 µm.
GLERL’s Dave Fanslow, operates the FluoroProbe displaying the level of pigments from different phytoplankton throughout the feeding experiment: pre-feeding of quagga mussel, progression of feeding on an hourly basis, and final measurements at the end of the experiment. The FluoroProbe measurements determine the concentration of pigments, such as chlorophyll, that quagga mussels filter out of the water throughout the experiment.
The FluoroProbe emits highly specific wavelengths of light using an LED array, which then trigger a fluorescence response in algae pigments and allow the immediate classification of green and blue green algae, cryptomonads, and diatoms.
University of Michigan scientists, Vincent Denef (left and upper right, kneeling in bottom right) and Nikesh Dahal (standing in bottom right), filter water before and after quagga mussel feeding. They are looking at changes in the bacterial community based on the genetic composition of groups, focusing on the variability of toxic production in cyanobacteria in harmful algal blooms. Following the filtration phase of the experiment, they will conduct DNA and RNA sequencing for toxicity gene expression in the cyanobacteria.