Population Characteristics of Quagga Mussels on Different Locations of a Shipwreck

Matthew Ryther, Carmen Aguilar and Russell Lee Cuhel, University of Wisconsin Milwaukee, Milwaukee, WI, United States
Over the course three years (2017-2019), we analyzed population parameters of the invasive Dreissena rostriformis bugensis (quagga mussel) on different surfaces of the Prins Willem shipwreck in Lake Michigan. By collecting samples with a remotely operated vehicle from specific areas of the sunken vessel, we were able to analyze growth patterns of mussels based on the surface that they grow upon. The samples were collected from wood, metal, wire, and nearby clay surfaces. Each sample of mussels was measured to form morphometric profiles and identify community structure. These measurements indicate that quagga mussel size distribution was highly dependent on their location of growth. The size frequency distribution of quagga mussel communities varied greatly among different surfaces. Morphometric characteristics of individual quagga mussels were similar and showed little variance among all surface types. In locations with high levels of particles due to constant current flow, we discovered that there was a large proportion of quagga mussels that are smaller than 4 mm; indicating the development of new generations. Furthermore, increases in ammonium and phosphates in particle free water were analyzed via colorimetric spectrophotometry in order to determine excretion rates of quagga mussels. They were incubated at 8°C and at 25°C. The levels of ammonium increased exponentially as the size of mussels increased. In addition, the metabolism of quagga mussels was directly correlated to the temperature of the water; excretion rates in 25°C water were nearly double that of the 8°C water.