The herbivorous fish, Aplodactylus punctatus, as a potential facilitator of dispersal of kelp, Lessonia trabeculata, in Chile

Abstract

Kelp forests are productive marine habitats known to facilitate many trophic and non-trophic interactions. While much of our understanding comes from positive effects of kelp on associated fauna, few studies focus on potential feedbacks that such fauna may provide to benefit kelp. This study aims to analyze the positive interactions between two closely associated fish and kelp species. Lessonia trabeculata, the bottom kelp, and the herbivorous fish, Aplodactylus punctatus, were sampled at four sites off northern-central Chile to evaluate the following: interactions during the ontogeny of the fish, the availability of reproductive tissue of the kelp blades, the effects of digestion by A. punctatus on L. trabeculata reproductive tissue, and the viability of zoospores after digestion. Our results show a network of direct and indirect positive interactions between these species. There was a positive correlation in their densities, possibly due to kelp functioning as a refuge and indirect food source. Juvenile A. punctatus feed on epifaunal species within the kelp, reducing grazer load and in turn generating a potential positive indirect effect on the kelp. Adult herbivorous fish consume kelp tissue as sustenance; when this kelp tissue is reproductive, digestion reduces epiphytic algal densities on the sori. Zoospores were found to remain viable after digestion, and microscopic sporophytes were produced at rates similar to those of undigested reproductive tissue. We conclude that positive links between A. punctatus and L. trabeculata occur along the geographic range distribution of both species and that this herbivorous fish could serve as a dispersal mechanism for L. trabeculata. To our knowledge, this is the first study that suggests that an herbivorous fish may have the potential to be a facilitator of kelp zoospore transport, and this may contribute positively to the recovery of natural kelp populations that are being intensively harvested in the region.