Mussel Growth under Ocean Acidification

Mussels (M. edulis) were obtained from the Loch Fyne, Argyll, Scotland (Loch Fyne Oysters Ltd) during October 2012. Mussels were placed into experimental tanks (six L) supplied with natural filtered (1 µm and UV) seawater at Loch Fyne temperatures (7°C) and ambient pCO₂ (~380 µatm). Mussels were fed 10 ml of cultured microalgae (five species of zooplankton, Nannochloropsis sp., Tetraselmis sp., Isochrysis sp., Pavlova sp., Thalassiosira weissflogii (stock from Reefphtyo, UK,) ~2.8 million cellml⁻¹) per six L tank every other day. The feeding regime was conducted throughout the two week acclimation and experimental period. This was sufficient to allow for growth under ocean acidification at 4666 cells ml⁻¹ during culture16 . To mark the start of the experimental period, mussels were placed into seawater containing the fluorescent dye calcein (150 µgL⁻¹ Calcein C0875-25g Sigma-Aldrich) for six hours. Mussels were rinsed thoroughly in seawater, and placed back in experimental tanks. Each experimental tank contained 30 mussels; this was the appropriate number of mussels per six L experimental tank to maintain sufficient dissolved oxygen levels (tested prior to experiment).