19 July finds me sitting among rocks and drifts of zebra mussel shells near an old stone bridge footing in the Rideau River at Andrewsville, 4 km n of Merrickville, Ontario. An alien Honeysuckle bush, bright-berried, overhangs the waters edge where part of the river finds its way around a little island and I am shaded by one of the large invasive alien Cathartic Buckthorns that have filled all the spaces of the river edge forest so that the only place to walk along shore is in the water. We have waded here from the footpath that comes down to the river from the mowed bank of the canal. Three plants of the native Joe Pye Weed, not blooming yet, keep me company.
The river has been sorting shells here, large native mussels that were killed by the Zebra Mussels a few years ago, and lots of remnants of Zebra Mussels too - the gravel between rocks is more than half Zebra Mussel shells. It is sad, now that there are relatively few live Zebras to be found, that the native unionid mussels, some of them perhaps 100 years old or more, are still all dead. They were smothered by the Zebra Mussel boom here in 2005, when every rock was crusted with them and the mussels couldn't close their shells for the very multitude of little invasives with their strong holdfast byssus threads, and the Zebras, filtering the water, starved the unionids.