The Effect of Flow on Filtering and Gaping Behavior in Mytilus galloprovinicalis

As ecosystem engineers, mussels create habitat for many species by ameliorating harsh environments, like extreme wave forces and temperatures. In low flow conditions, however, mussel aggregations may alter their local chemical environment via respiration and calcification, creating hypoxic conditions within the interstitial gaps between mussels. Thus, the local flow regime may play a large part in whether mussel aggregations are beneficial or detrimental to other species. However, the extent to which mussel filtering and gaping behavior may prevent the development of harsh chemical conditions by increasing mixing in the intertidal zones and the surrounding water is still unknown. We quantified the effects of flow on mussel filtering behavior to better understand how they interact to influence local water chemistry. We used Hall effect sensors to quantify mussel gaping and found a positive linear relationship with filtering speed. Flow (up to 20 cm/s) had no significant effect on gaping, although mussels positioned further downstream within an aggregation tended to gape wider. Our results indicate that individual variation in behavior due to spatial position maybe be more important than flow in determining gaping activity, thus having consequences for how mussel behavior influences change in chemistry within the interstitial zone.