The eruption of Mount St. Helens was a massive landscape-scale disturbance. One of the little known consequences of the eruption was the creation of >100 new ponds. These ponds are one of the few examples of primary succession of aquatic ecosystems, and as such, present a novel opportunity to study community assembly and the factors that influence it. Here we report on: 1) a long-term study of the colonization dynamics of ponds; and 2) a synoptic survey of contemporary conditions. Macroinvertebrate communities were sampled in ponds periodically between 2003-2015. An additional 23 ponds were sampled in 2015 for macroinvertebrates, zooplankton community composition, and physicochemical variables. Beta diversity was examined using a null model approach that controls for differences in alpha diversity, and allows the relative influence of stochastic and deterministic mechanisms to be evaluated.
Colonization and contemporary distribution dynamics appear to be related to a complex mixture of terrestrial succession, pond hydroperiod, spatial patterns of pond distribution, and variations in physical and chemical conditions. Zooplankton communities were more similar than expected despite the presence of strong environmental gradients. Our study may fill a significant gap in our understanding of the dynamics of primary succession in freshwater ecosystems using a unique natural experiment.