how fast do zebra mussels colonize submerged rocks? like if the lake champlain basin gets less rain next year, are all the rocks on the shore going to emerge from the receding water encrusted with nature's blademasters?
Pretty quickly! Immature zebra mussels attach and grow rapidly when given the opportunity. We observed this on Lake Champlain this summer--after spending more than two full months with the Lake's surface elevation comfortably above 97', in September the receding waters revealed that zebra mussels had colonized the bedrock shoreline in our park, positioned largely in thick, messy lines following cracks in the rock. Most of the ones I could see had already exceeded a millimeter in length, with some having reached 5mm! Not bad for a species that first attaches to a substrate at a length of around a tenth of a millimeter, and more than sufficient to injure a person (or unfortunate snail).
Lake Champlain's lowest post-July-9th elevation was 96.1'. If the Lake remains at an elevated level for the duration of the winter (which seems likely) and then returns to historically average behavior (totally up in the air), we can expect to see new zebra mussel populations exposed to the air through October, meaning shoreline-walkers may well be contemning with centimeter-plus mussels underfoot next year! The shells do crumble over time, though, once placed in air--before the water levels rose back up this fall, a lot of cracks in the shore-rocks were full of pulverized shell fragments. You would hear them crunching underfoot as you walked.