Comment: A reexamination of , bed-scale impact and recovery of a commercially important intertidal seaweed

Abstract

Johnston et al., 2023 (Bed-scale impact and recovery of a commercially important intertidal seaweed. J. Exp. Mar. Biol. Ecol. 561) report that rockweed biomass recovers to pre-harvest levels one year after commercial harvest. The Johnston et al. study has two major problems in design, execution, and interpretation of results: 1) industry partner conflict of interest and statistically undetectable impact of the harvest treatment on Ascophyllum nodosum (rockweed) beds, 2) incomplete statistical analysis with inappropriate inferential conclusions about biomass recovery of harvested rockweed beds. Our analysis of their data shows that the only regions of the coast where rockweed biomass recovered to pre-harvest levels are the three regions where the harvest treatment was never detectable. In the one region where the harvest treatment was detectable, rockweed biomass did not recover to pre-harvest levels in a year. Rockweed is a foundational species in the rocky intertidal food web as well as an ecosystem engineer. The improper interpretation by Johnston, et al. of the study data is misleading ecosystem managers and the public about the impacts of commercial rockweed harvests. Most concerning, this paper sets a false foundation for marine policy on commercial rockweed harvesting in Maine.