Velocity and turbulence measurements around a dense aggregation of mussels from a flume experiment conducted July 2023

The project investigates how the metabolic activity of dense aggregations of marine organisms alter the water chemistry of their interstitial spaces, and how these microscale alterations feedback to affect the organisms’ interactions in coastal ecosystems. The research evaluates whether corrosive chemical microclimates (such as low oxygen or low pH) are most extreme in low flow, high temperature conditions, especially for dense aggregations of mussels with large biomass and/or high respiration rates, and if they negatively impact mussel beds and the diverse biological communities they support. In order to address these questions, a flume experiment was conducted at Friday Harbor Laboratories where flow and chemical gradients were measured within and above a dense aggregation of mussels (Mytilus trossolus). Twenty profiles were taken over 5 days with 5 profiles taken for each of the four experimental flume speeds (0.6, 1.3, 2.5, 3.6 cm/s). Approximately 3-minute-long measurements were taken of velocity, dissolved oxygen, temperature, and pH every centimeter within the bed and two measurements were taken above the bed. Ambient conditions (dissolved oxygen, temperature, pH and conductivity) were also measured continuously using an array of HOBO loggers.