MEPS 565:67-77 (2017)  -  DOI: https://doi.org/10.3354/meps11992

ABSTRACT: Ocean acidification (OA) is a term describing the uptake of CO₂ from the atmosphere, decreasing seawater pH and altering carbonate chemistry. Mussels are an ecologically and economically important taxon that attach to solid surfaces via the byssus. To date, little is known about the effects of OA on mussel byssal attachment and the underlying molecular byssal responses. This study demonstrated that after 1 wk of exposure to acidified seawater, both mechanical properties (such as strength and extensibility) and the numbers of byssal threads produced by Mytilus coruscus were significantly reduced, leading to a 60 to 65% decrease in mussel byssal attachment strength. Real-time PCR results suggested that OA also altered the expression of genes encoding the proximal thread matrix protein (PTMP), precursor collagen proteins (preCOL-P, -NG and -D) and mussel foot proteins (mfp-1, -2, -3, -4, -5 and -6). The down-regulation of some specific byssal proteins may be one of the reasons for the weakened mechanical properties of individual byssal threads under OA conditions. In contrast, the up-regulation of some other specific byssal proteins may be adaptive responses to minimize the adverse effect of OA on byssal attachment. OA may weaken mussel byssal attachment by reducing the production and mechanical properties of byssal threads and by inducing byssal molecular responses. The weakened byssal attachment induced by OA therefore could pose a substantial threat to both mussel aquaculture and mussel-bed ecosystems.

KEY WORDS: Elevated pCO₂ · Mytilus coruscus · Byssal thread · Gene expression · Mechanical properties