Rockweed is a large-celled, photosynthetic alga, historically harvested for agricultural purposes in Europe and Canada. It grows on the rocky shores of Maine, and harvesting here has recently been on the rise. Rockweed can be made into fertilizer, animal feed supplements, food and other products, and has a very high commercial value.

However rockweed also provides shelter and forage for many marine species, both those who stay in the intertidal and those who use the intertidal during high tide.  Because of the increase in harvesting pressure, there is concern about the ecological impacts this harvesting might have on the rocky intertidal community.

Aimee Phillippi and her students in Marine Biology recently completed a study examining impacts of rockweed harvesting on invertebrate intertidal residents. They worked to establish harvested and un-harvested plots of rockweed and then sampled the plots monthly for mobile invertebrates (snails and green crabs) as well as smaller, less mobile invertebrates. Removal of the rockweed canopy resulted a greater abundance of snails and fewer crabs, but had virtually no impact on the quantity of other invertebrates. Pam MacRae, another professor in the Center for Biodiversity, is working with Phillippi and the students, continuing to look at their rockweed beds and how larger species might be transient users, coming into the beds at high tide for foraging, and if rockweed harvesting alters that use.