Wave action limits crowding in an intertidal mussel

GUTIÉRREZ, JORGE LUIS CEFERINO; PALOMO, MARIA GABRIELA; BAGUR, MARIA; ARRIBAS, LORENA PILAR; SORIA, SABRINA ANDREA

MARINE ECOLOGY PROGRESS SERIES

INTER-RESEARCH

Lugar: Oldendorf/Luhe; Año: 2015 vol. 518 p. 153 - 163

0171-8630

Intraspecific competition for space is generally 1 invoked as the chief process limiting crowding in sessile or little mobile marine invertebrates. However, it generally remains uninvestigated how high conspecific density induces individual removal or mortality in turn restraining crowding in these organisms. Here we illustrate that crowding in an intertidal mussel is limited by a combination of wave action and space limitation. Mussel beds at our study area occur primarily as a single-layer of individuals because wave forces remove multilayered mussel hummocks quickly after they develop. Mussels in hummocks show lower attachment strength than those in the single-layered matrix. Accordingly, wave conditions associated to the passage of cold fronts (7-day average recurrence time) cause detectable mussel dislodgement in a high proportion of hummocks but have virtually no impact on single-layered areas. Since it is wave action the proximate cause of mussel dislodgement, upper limits to crowding in this species would not be fixed to a particular level of space occupation (i.e., as predictable from interference competition for space alone) but variable in space and time depending on wave exposure. This example suggests a mechanism of population control where the impact of a physical factor on population size is larger at higher population density and supports early hypotheses about the occurrence of density-dependent population control by physical factors when the availability of safe sites is limiting.