Xuifeng Zhang, Xueying Mei, Lars Rudstam (Chinese National Science Foundation visiting scholar support).
Being “ecosystem engineers”, the invasion of zebra (Dreissena polymorpha) and quagga (D. rostriformis bugensis) mussels has been an area of intensive research in North American lakes as these species cause substantial ecological impacts and dramatically alter both the structure and function of invaded systems. Quagga mussels invaded Oneida Lake around 2006 and are displacing zebra mussels, a pattern also seen in many other lakes in both North America and Eurasia. Though the two mussel species have similar ecological impacts in freshwater ecosystems, they are not identical. Differences between the two congeners may have large consequences for the ecosystem they invade and quagga mussels may have greater system-wide effects than zebra mussels. However, little information is available on the ecological impacts of the replacement of zebra mussel by quagga mussel on shallow lakes. In 2015, we conducted an eight-week mesocosm experiments with zebra mussel, quagga mussel or both species as mussel treatments compared with no-mussel controls. The experiments were run in plastic tanks containing sediment and water collected from Oneida Lake to investigate the effects of replacement of zebra mussel by quagga mussel on water quality in shallow lakes. We hypothesized that replacement of zebra mussel by quagga mussel may improve water clarity further which would promote benthic algae. Contrary to our hypothesis, we found that the replacement of zebra mussel by quagga mussel did not improve water clarity further when at the same density; however highest water clarity was found with both mussel species present.