LAUSR

Dreissenid mussels can alter nutrient cycling and algal productivity in many freshwater ecosystems. But their effects on sedimentary phosphorus dynamics remain largely undefined. Here, we report evidence that dreissenids affect the concentrations of five sedimentary phosphorus fractions and total phosphorus. During our study, zebra mussels were still common and coexisted with quagga mussels in many parts of the basin. The relative abundances varied across the basin, which we characterized as five west-to-east alternating zones where zebra mussels dominated zones I (coastal) and III, quagga mussels dominated zones II and IV, and few dreissenids were present in zone V. The phosphorus fractions exhibited variation concordant with and therefore potentially influenced by dreissenids. Concentrations of all fractions and TP were consistently greater in sediments where quagga mussels dominated than in sediments where zebra mussels dominated. The responses to the absence versus presence of dreissenids were mixed, with Res-P being significantly affected, NaCl-Pi and HCl-Pi being moderately affected, and NaOH-Pi being least affected. Although such dreissenid effects were somewhat altered by in-lake biogeochemical cycling and transfer, we found that elevated levels of NaCl-Pi in dreissenid-present sediments, especially in quagga-dominated sediments, could be linked to recent eutrophication and harmful algal blooms in the basin.