Lake Characteristics, Population Properties and Invasion History Determine Impact of Invasive Bivalves on Lake Nutrient Dynamics

Abstract

Invasive species can have large impacts on ecosystems, including the cycling and distribution of nutrients. To determine the whole-ecosystem effects of invasive zebra mussels on lake nutrient dynamics, we sampled 10 invaded Minnesota lakes spanning a broad trophic status gradient. We conducted N and P excretion and biodeposition rate measurements and determined the C, N and P composition of dreissenid soft tissues and shell material in the study lakes. We also estimated the whole-lake biomass of live dreissenid mussels and their dead shell material, constructing comprehensive nutrient budgets for dreissenid populations in the study lakes. We used the results of our measurements and published data to estimate the contribution of dreissenids to P budgets in 24 additional lakes in Europe and North America. Results show that nutrient cycling rates and composition of soft tissues and shells vary with mussel size and lake trophic status. Zebra mussels made variable, but often large, contributions to cycling and storage of water column standing stocks of POC, PON and TP in the study and literature lakes. In some lakes, the effects of zebra mussels on P dynamics were also considerable in the context of estimated P external and internal loading, sediment sequestration and effects of other biota. We show that the impact of zebra mussels on whole-lake nutrient budgets depends on lake properties, dreissenid population characteristics and invasion history. This information can be used by ecosystem managers to prioritize invasion prevention efforts toward lakes likely to be most strongly impacted by zebra mussel invasions.