Ladd Johnson's lab is at Laval University in Quebec, QC, Canada. There he supervises students in their study of the ecology of benthic communities. His primary research interests are in marine invertebrates, seaweeds and invasive species.

His main research programs are as follows:

Marine ecology: Intertidal and shallow subtidal communities are important components of coastal ecosystems and also serve as models for the studies of the structure and function of ecological communities in general. In particular, they permit the experimental investigation of the interplay between physical and biological factors in controling intra-specific and inter-specific interactions. Research in my laboratory focuses primarily on the ecology of algae and the herbivores that eat them. Current projects include (1) the development of microclimate models for predicting the stresses experienced by intertidal plants and animals during low tide and how variation in these stress may affect the establishment of individual macroalgae and the development of algal turfs, and (2) the establishment and persistence of small kelp beds in shallow subtidal communities dominated by urchins. In both these system, we are examining the effects of variation in the physical environment (e.g., desiccation, wave exposure) on the extent and intensity of herbivory. We are particularly concerned with the effects of small-scale surface topography on the recruitment of algae, especially the small post-settlement stages.

Biological invasions: The natural communities of our world are being degraded by the introduction of non-indigenous species. Modern methods of transportation and increasing global trade have greatly accelerated this process in aquatic communities. My laboratory's research in this area concerns the post-introduction dispersal and spread of exotic species as well as their impact on native species and the ecosystems in which they are found. Again, our emphasis is on the factors that control species establishment including propagule production, dispersal, and recruitment. Past work has been primarily on the zebra mussel invasion of inland lakes but I hope to expand this area of research into other exotic species and environments.