Are pelagic mussel stages chemically attracted to barnacle stands for settlement?

Abstract

These photographs show dense aggregations of juvenile mussels (Mytilus spp) growing on intertidal barnacle stands (Semibalanus balanoides) on the Atlantic coast of Nova Scotia, Canada. In wave-exposed habitats on this coast, extreme environmental events can lead to widespread mortality of intertidal organisms, resulting in large clearings on the rocky substrate. Typically, barnacles are the first macroscopic organisms that recolonize such areas. Once those barnacles attain a certain size, pelagic mussel stages settle upon them and become benthic recruits. These new additions to mussel populations occur substantially more often on barnacle patches than on bare rock. In the complex microtopography of barnacle beds, mussel recruits benefit from increased moisture during low tides and greater protection from waves during high tides. As mussel recruitment progresses, with later recruits concentrating around the first recruits, mussels achieve high densities and outcompete barnacles as they grow, ultimately becoming the dominant species.