Physiological and gene expression responses of the mussel Mytilus galloprovincialis to low pH and low dissolved oxygen

• The prevalence and frequency of hypoxia events have increased worldwide over the past decade as a conse-quence of global climate change and coastal biological oxygen depletions. On the other hand, anthropogenic emissions of CO2 and consequent accumulation in the sea surface result in a perturbation of the seawater car-bonate system, including a decrease in pH, known as ocean acidification. While the effect of decreases in pH and dissolved oxygen (DO) concentration is better understood, their combined effects are still poorly resolved. Here, we exposed adult mussels (Mytilus galloprovincialis) to two pHs (8.27 and 7.63) and DO concentrations (7.65 and 2.75 mg L- 1) over 17 days in a full-factorial design. These levels correspond to extremes of the present natural variability and are relevant in the context of ocean acidification and hypoxia. No mortality was observed during the experiment. However, sublethal effects were observed for clearance and oxygen consumption rates, as well as total haemocytes count and haemocytes viability and gene expression in mussels exposed to the combination of low pH and low DO. Respiration and excretion rates were not significantly impacted by low pH and DO, alone or in combination. Overall, low pH alone led to a decrease in all tested physiological parameters while low DO alone led to a decline in clearance rate, haemocyte parameters and an increase in carbohydrate content. Both pa-rameters led to up-or down-regulation of most of the selected genes. Not surprisingly, the combined effect of low pH and low DO could not be predicted by a simple arithmetic additive response at the effect level, highlighting more complex and non-linear effects.

Subject headings

NATURVETENSKAP  -- Biologi -- Ekologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Ecology (hsv//eng)

Keyword

Hypoxia

Acidification

Multiple stressors

Physiology

Gene expression

Bivalves

ocean acidification

oxidative stress

crassostrea-gigas

seawater

acidification

pacific oyster

perna-viridis

hypoxia

exposure

respiration

metabolism

Environmental Sciences & Ecology

Marine & Freshwater Biology

Publication and Content Type

ref (subject category)

art (subject category)