Impact of ocean acidification and warming on the Mediterranean mussel (Mytilus galloprovincialis)

Abstract

In order to assess the effects of ocean acidification and warming on the Mediterranean mussel (Mytilus galloprovincialis), specimens were reared in aquarium tanks and exposed to elevated conditions of temperature (+3 • C) and acidity (−0.3 pH units) for a period of 10 months. The whole system comprised a factorial experimental design with 4 treatments (3 aquaria per treatment): control, lowered pH, elevated temperature, and lowered pH/elevated temperature. Mortality was estimated on a weekly basis and every 2 months, various biometrical parameters and physiological processes were measured: somatic and shell growth, metabolic rates and body fluid acid-base parameters. Mussels were highly sensitive to warming, with 100% mortality observed under elevated temperature at the end of our experiment in October. Mortality rates increased drastically in summer, when water temperature exceeded 25 • C. In contrast, our results suggest that survival of this species will not be affected by a pH decrease of ∼0.3 in the Mediterranean Sea. Somatic and shell growth did not appear very sensitive to ocean acidification and warming during most of the experiment, but were reduced, after summer, in the lowered pH treatment. This was consistent with measured shell net dissolution and observed loss of periostracum, as well as uncompensated extracellular acidosis in the lowered pH treatment indicating a progressive insufficiency in acid-base regulation capacity. However, based on the present dataset, we cannot elucidate if these decreases in growth and regulation capacities after summer are a consequence of lower pH levels during that period or a consequence of a combined effect of acidification and warming. To summarize, while ocean acidification will potentially contribute to lower growth rates, especially in summer when mussels are exposed to sub-optimal conditions, ocean warming will likely pose more serious threats to Mediterranean mussels in this region in the coming decades.

Impact of ocean acidification on thermal tolerance and acid–base regulation of Mytilus edulis (L.) from the North Sea

“…This supports the observations by that both fluids are characterized by a similar carbonate system, also recently described in M. galloprovincialis (Gazeau et al, 2014). Therefore, only haemolymph data are discussed here.…”

Comparison of the alkalinity and calcium anomaly techniques to estimate rates of net calcification

“…Previous experiments that focused on the effect of ocean acidification on bivalve calcification assumed that NH 4 + excretion is negligible (Gazeau et al 2007, Mingliang et al 2011, Waldbusser et al 2011. Recently, however, Gazeau et al (2014) reported NH 4 + excretion rates being responsible for 60% (on average) of ΔA T in the Mediterranean mussel Mytilus galloprovincialis kept in the laboratory for ~1 yr. This contribution is much higher than that reported in the present study, suggesting that correction of ΔA T could vary significantly depending on the physiological state of the organism.…”

“…It is nondestructive and offers the possibility of studying the same organism and following its calcification over time (e.g. Martin & Gattuso 2009, Bramanti et al 2013, Gazeau et al 2014). Another option is to estimate the linear extension (growth) of an organism, assuming the density of its calcifying structures is known.…”

Interactive effects of seawater acidification and elevated temperature on biomineralization and amino acid metabolism in the musselMytilus edulis

“…Seawater warming may ameliorate the negative impact of seawater acidification on corals (Kleypas and Yates, 2009;McNeil et al, 2004). Whether the combination of seawater acidification and elevated temperature affects shell growth, metabolic rate and periostracum production in the Mediterranean mussel, Mytilus galloprovincialis, is unclear (Gazeau et al, 2014). These results suggest that there are complex responses within different calcifiers to the combined climate stressors.…”