Abstract
This work investigated the effect of carbon dioxide-induced decreased water pH (8.1 – control, 7.5 and 7.0), oxygen saturation (~100% and ~20%) and the combination of both factors on the behaviour (gaping activity) and the total metabolic rate of blue mussel Mytilus edulis trossulus from the southern Baltic Sea. Heat dissipation measurements were carried out in a Calvet-type isothermal twin calorimeter equipped with a flow-through system. The resting metabolic rate was not significantly (p > 0.05) affected by pH or oxygen saturation. Neither was there significant (p > 0.05) effect of the interaction of both factors on this process. The high inter-individual variability in behaviour affected the value of maximal recorded activity and duration of activity peaks connected with shell gaping behaviour. In some mussels, they were short and appeared periodically, and other individuals were inactive or exhibited temporal activity terms of different duration. The lowered oxygen saturation significantly (p < 0.05) affected the time spent on activity. However, there was no effect (p > 0.05) of lowered pH on this parameter, which indicates that oxygen deficiency may affect the Baltic population of M. edulis trossulus more seriously than acidification.
Acknowledgements
We wish to thank Mr Jerzy Drzazgowski from the University of Gdańsk for technical assistance during performance of the calorimetric measurements and Mr Timothy Alexander for help in linguistic improvement of the manuscript.