Abstract
Plastic has emerged as an abundant, stable substratum for oceanic dispersal of organisms via rafting. However, the ecological mechanisms underlying community diversity on plastic debris remain poorly understood. On a cruise from California to Hawai’i, we surveyed plastic debris, some likely originating from the 2011 Tōhoku tsunami, to examine the relationship between rafting community diversity and both habitat area and stalked barnacle (Lepas spp.) abundance. For sessile taxa richness, we observed an interaction in which the positive effect of debris area weakened the negative effect of barnacle cover. In contrast, for mobile taxa richness, including cohabiting species from opposite sides of the Pacific Ocean, barnacle abundance had a positive effect that was strongest at smaller debris sizes. These findings suggest that barnacles, through interactions with habitat area, have trait-dependent effects on other species, serving as both foundation species and competitors, mediating the diversity and dispersal potential of marine organisms on plastic debris.
Highlights
IntroductionThe exposed environment of smooth plastic surfaces in the ocean may be analogous to natural environments, in which harsh conditions (e.g., high physical stress, nutrient limitation or predator pressure) promote positive species interactions (e.g., mutualism, facilitation) that, in turn, allow for a greater variety of organisms to persist[12,13]
The exposed environment of smooth plastic surfaces in the ocean may be analogous to natural environments, in which harsh conditions promote positive species interactions that, in turn, allow for a greater variety of organisms to persist[12,13]
The plastic items collected in this study may have originated from an estimated 1.5 million tons of floating debris deposited into the Pacific Ocean during the Tōhoku tsunami, which took place in Japan on March 11, 2011
Summary
The exposed environment of smooth plastic surfaces in the ocean may be analogous to natural environments, in which harsh conditions (e.g., high physical stress, nutrient limitation or predator pressure) promote positive species interactions (e.g., mutualism, facilitation) that, in turn, allow for a greater variety of organisms to persist[12,13]. It has been speculated that certain rafting organisms (e.g., stalked barnacles of the genus Lepas) promote colonization and persistence of other rafting taxa on natural debris, by providing additional structural complexity[14]. In this way, Lepas barnacles may serve as foundation species (sensu Dayton 1972)[15], structuring the greater community by decreasing the severity of local conditions. Lepas barnacles may serve as foundation species (sensu Dayton 1972)[15], structuring the greater community by decreasing the severity of local conditions Such foundation species on plastic debris could alter these artificial rafts by increasing their habitability to a more diverse assemblage of rafting organisms, www.nature.com/scientificreports/. We examined the effects and interactions of habitat area and Lepas barnacle abundance on rafting community diversity on structurally-limited plastic debris to better understand the role these different mechanisms may play in plastic-mediated dispersal of marine organisms
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