Revisiting carbon cycling in the Laurentian Great Lakes following dreissenid mussel invasion

Abstract Since the active role of inland waters in cycling carbon (C) has been revealed, there has been a renewed interest in calculating C budgets for inland waters to understand their role with respect to global climate change. There is a lack of knowledge regarding C cycling in the Laurentian Great Lakes, the worlds largest freshwater reservoir, with current estimates neglecting the role of invasive species. For one of the most pervasive invaders, dreissenid (zebra and quagga) mussels, research has focused on filter feeding impacts on phosphorus dynamics, but there is a lack of knowledge regarding their role in C cycling, specifically, the impact of the C stored in their slowly degrading shells. As such, we set out to estimate the mass of empty shells and C stored in those shells. We calculated an estimated 1.19 E10 tonnes of empty shell mass currently sitting at the bottom of these lakes, which store approximately 1.43 E9 tonnes of C. This scale of inorganic C storage is comparable to rates of organic C storage in nature-based climate solutions. This work demonstrates the importance of a previously unexplored pathway that dreissenid mussels are altering C cycling in the Laurentian Great Lakes and the thousands of other invaded lakes and rivers.