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MEPS prepress abstract   -  DOI:

Byssal thread attachment and growth are not correlated across gradients of temperature and food availability for two congeneric mussel species

Emily A. Roberts*, Emily Carrington

*Corresponding author:

ABSTRACT: Anthropogenic warming and natural climate variability affect global patterns of seawater temperature and marine primary productivity and affect organism survival, growth, and physiology. Mussels are ecosystem engineers that utilize byssal thread structures to attach to hard substrate, a strategy key to survival in wave-swept rocky shore environments. Byssal thread production varies according to season and environmental conditions, and temperature and food availability may influence the production of these structures by affecting energy limitation. Mytilus trossulus and M. galloprovincialis are congeneric mussel species in the Northeast Pacific with cold- and warm-adapted thermal tolerances, respectively. We hypothesized that temperature has opposing effects on growth rates of the 2 species, and that either (A) byssal thread production is positively correlated with mussel growth rate, or (B) byssal threads are produced constitutively regardless of growth rate. We manipulated seawater temperature and food availability and quantified mussel performance in terms of survival, growth, and byssus attachment. We found that overall, M. galloprovincialis had positive shell and tissue growth and M. trossulus had minimal shell growth and a loss in tissue mass. Temperature had opposing effects on each species; temperature increased shell growth of M. galloprovincialis but increased tissue loss of M. trossulus. Temperature did not affect byssal thread production, and there was no significant relationship between byssal thread quality or quantity and shell or tissue growth across the temperature and food gradient for either species. Our results suggest that energy allocation is prioritized towards byssal thread production over growth.