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Spatial variation in propagule pressure and establishment of zebra mussels (Dreissena polymorpha) within a subtropical reservoir

Zebra mussels (Dreissena polymorpha) are one of the most economically and ecologically disruptive aquatic invasive species in North America, where they damage infrastructure and alter ecological processes. Understanding zebra mussel propagule pressure and establishment is essential for predicting expansion into subtropical lakes and reservoirs. Key water quality parameters, such as temperature, water clarity, dissolved oxygen, and primary productivity have been found to play major roles in these processes. To test if environmental variation affected zebra mussel propagule pressure and establishment within a large, subtropical lake, we measured zebra mussel larval (veliger) abundances in the water column and post-veliger abundances on hard surfaces and quantified water quality during 2011–2015 at six sites spanning 32.8 km in Lake Texoma, OK-TX which differed markedly in salinity, water clarity, and algal abundances. We found that densities of both life stages were lower at western sites with lower water clarity, higher salinity, and higher productivity. Additionally, higher numbers of zebra mussel post-veligers accrued on the undersides of deeper surfaces, suggesting preference for lower temperatures and refuge from predators. Our results suggest that in habitats that are particularly stressful for zebra mussels, water quality predicts propagule pressure and establishment of zebra mussels across a lake, emphasizing the need to consider environmental heterogeneity within large lakes when predicting the potential range and impact of this cosmopolitan invader.