The influence of carbon dioxide-induced water acidification on the osmotic and metabolic responses of the Baltic amphipod Gammarus oceanicus

Abstract

The aim of this study was to investigate the effect of CO₂-induced water acidification (pH values: 8.1 − control, 7.5 and 7.0) on the hemolymph osmolality and total metabolic rate of amphipod Gammarus oceanicus under short-term exposure. The hemolymph osmolality was measured using a vapor pressure osmometer. The metabolic rate was determined based on the heat dissipation measurements using a Calvet-type isothermal twin calorimeter. The hemolymph osmolality remained unchanged after exposure to pH 7.5 and it increased in the lowest treatment. Acidification did not significantly affect the resting or active metabolic rate. The observed results indicate that high osmolality maintained during hypercapnia did not generate additional physiological costs. It may therefore be concluded that the studied species is preadapted for this factor. The long-term adaptation to hypoosmotic conditions in the brackish Baltic Sea might also have preadapted it to hypercapnia because similar physiological mechanisms are responsible for the resistance to both factors.

Keywords:

• Acidification
• Gammarus oceanicus
• heat production
• total metabolic rate
• osmoregulation
• hemolymph osmolality

Acknowledgements

We wish to thank Mr Jerzy Drzazgowski from the University of Gdańsk for technical assistance during performance of the calorimetric measurements and Dr Ewa Kaźmierczak for help in linguistic improvement of the manuscript. We would also like to thank two anonymous reviewers for valuable suggestions to improve the manuscript.