Strength in Numbers – The Mussels of The Prins Willem IV Shipwreck

Population parameters of the invasive voracious filter-feeder Dreissena rostriformis bugensis (quagga mussel, QM) on different surfaces of the Prins Willem V shipwreck in Lake Michigan were analyzed from two separate years (2018 & 2019). We collected samples with a remotely operated vehicle, launched from the RV Neeskay, from specific areas of the Prins Willem IV, enabling analysis of growth patterns of mussels based on the surface that they grow upon. Samples were collected from a wood deck, metal hatch, suspended wire, steel hull, railing, and open clay surrounding the wreck. Each sample of mussels was measured to form morphometric profiles and identify size-frequency-based community structure. These measurements indicate that quagga mussel size distribution was highly dependent on their location and surface structure of growth. 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, there was a large proportion of quagga mussels that were smaller than 4 mm; indicating recent spawning. Furthermore, excretion of ammonium and phosphate in particle free water was analyzed via colorimetric spectrophotometry. Excretion rates exhibited a cubic function of length (i.e., volumetric) of the quagga mussels and differed with location on the shipwreck. The body tissue of the mussels was prepared for CHN analysis to obtain carbon and nitrogen ratios. Phosphorous content was determined by spectrophotometry in order to determine the full C:N:P ratio of the tissue as compared to the Redfield ratio to help determine food web interactions