MEPS 487:89-100 (2013)  -  DOI: https://doi.org/10.3354/meps10317

ABSTRACT: The blue mussel Mytilus edulis is widely distributed and acknowledged for its ecological importance in the intertidal zone in northern temperate areas. However, detailed studies of the structure and dynamics of intertidal M. edulis populations are lacking in its northern distribution area. This study provides baseline information on the population structure of M. edulis in the mid-intertidal zone of the sub-arctic Godthåbsfjord in West Greenland (64°N). Abundance was very patchy (average 18.6 ind. 0.049 m^-2; range 0 to 312) and concentrated around crevices, boulders and macroalgae beds. Average biomass was 7.78 g wet mass 0.049 m^-2. Young specimens <3 yr old (or <15 mm shell length) made up 82% of the population. Maximum age was estimated at 19 yr. The age structure suggested that the annual instantaneous mortality rate, Z, gradually decreased with age from 0.82 to 0.12. Growth functions obtained from size-at-age data showed significant differences between sampling sites in the Godthåbsfjord, overall covering much of the geographical variation found in the North Atlantic. The absence of invertebrate predators in the intertidal in this sub-Arctic habitat suggests that physical drivers are important for structuring the M. edulis community. Winter temperatures below -15°C combined with ice scouring are suggested to be the key drivers. Crevices, boulders and macroalgae beds are important refuges during detrimental extreme events but also provide variable growth conditions.

KEY WORDS: Bivalve · Growth · Mortality · Ice scouring · Climate · Temperature · Epifauna · Predator regulation · Environmental drivers