Early benthic phase mortality of the barnacle Balanus glandula is influenced by Fucus spp. cover but not by weather-related abiotic conditions

Abstract

This study aimed to improve our understanding of the factors that influence mortality of the acorn barnacle, Balanus glandula, during the first days after the transition from pelagic to benthic environments. This was accomplished by examining the mortality of barnacle cyprids from settlement to metamorphosis, as well as mortality of early juveniles up to the age of 10 d after metamorphosis. A field survey of B. glandula recruitment was conducted from 1 to 23 June 2011 at Wizard Islet in Barkley Sound, British Columbia, Canada. We also documented the range of weather-related abiotic conditions that occurred in the intertidal zone during the recruitment survey. These weather-related abiotic conditions were highly variable during the survey, indicating that each daily cohort of barnacle settlers experienced conditions after settlement that differed from those experienced by the other daily cohorts. Cyprid cohort mortality was high, averaging 52.7±22.7% (SD), and differed greatly among the daily cohorts. Contrary to expectations, cyprid mortality was not significantly influenced by weather-related abiotic conditions. This was likely due to the study being conducted during a La Niña cycle that may have had lower temperature and desiccation levels than are typical for Barkley Sound. Overall, an average of 70.6±16.3% (SD) of all metamorphosed individuals were alive 10d after metamorphosis. Although the direct cause of high mortality could not be determined, Fucus spp. cover negatively influenced the survival of both newly-settled cyprids and juveniles. A decline of fucoid algae populations due to changing climate may therefore result in an increase in barnacle survival through the early benthic phase and may subsequently affect annual variation in barnacle population abundance.