Metabolism in blue mussel: intertidal and subtidal beds compared

Abstract

Mytilids occur worldwide, and mussel beds are a prominent intertidal and subtidal system feature. Brittany (France) has a complex population structure in which pure genotypes alternate with hybrids of Mytilus edulis and M. galloprovincialis, referred to here as 'mussels'. Mussels live attached to the substrate in subtidal and intertidal areas and are regularly exposed to strong environmental variations (e.g. desiccation, light, and temperature). The resistance of mussels to emersion is based on a combination of different strategies, such as metabolic rate depression , anaerobic metabolism and air breathing. In the present study, we have evaluated the differences in aerial and underwater mussel metabolism between an intertidal mussel bed and a subtidal one. Metabolism was measured seasonally for small (shell length 24 to 26 mm) and large (43 to 66 mm) individuals. Mussel aerial respiration fluxes were directly correlated with air temperature. In contrast, underwater carbon (DIC) fluxes seemed to be influenced by additional factors such as food availability and/or reproduction period. Underwater metabolism was higher in small mussels (intertidal: 35.9 μmol DIC g AFDW −1 h −1 ; subtidal: 51.4 μmol DIC g AFDW −1 h −1) than in large mussels (intertidal: 26.4 μmol DIC g AFDW −1 h −1 ; subtidal: 21.3 μmol DIC g AFDW −1 h −1). In contrast, aerial respiration showed different adaptations: small intertidal and subtidal mussels had similar respiration under emerged conditions, while large intertidal individuals showed higher carbon fluxes during emersion compared to subtidal individuals. These data suggest that while underwater fluxes were similar for the 2 mussel beds, all small and large intertidal mussels are far better able to tolerate emersion than large subtidal animals. Subtidal mussels seem thus to lose their ability to respire in air after becoming adult.

Regional scale estimation of carbon fluxes from long-term monitoring of intertidal exposed rocky shore communities

“…At the low-shore level, the carbon originating from calcification corresponds to 12% of the total carbon emission. This estimation for the entire community is in accordance with the data for each individual species used in this study (11% for limpets, 25% for oyster, 3% for barnacles, between 7 and 14% for mussels, and between 13 to 23% for the other gastropods) (Clavier et al, 2009;Lejart et al, 2012;Tagliarolo et al, 2012Tagliarolo et al, , 2013aTagliarolo et al, , 2013b. Previous studies performed in the same area however, provided substantially higher estimates of the contribution of the calcification process to total carbon emission (between 47 and 82%) (Golléty et al, 2008a;Hily et al, 2013).…”

“…Respiration was estimated for each site as a function of temperature and annual average biomass using the Arrhenius equation (Table 2). Data were provided by previous studies conducted within the same geographical area from direct measurements in the laboratory using closed chambers in immersion (dissolved inorganic carbon fluxes) and emersion (CO 2 fluxes) ( Table 2) (Clavier et al, 2009;Lejart et al, 2012;Tagliarolo et al, 2012Tagliarolo et al, , 2013aTagliarolo et al, , 2013b. Because mussel underwater respiration is not significantly influenced by temperature (Tagliarolo et al, 2012), average fluxes were used in the calculations.…”

“…Mussel carbon fluxes are known to differ between large and small individuals. Respiration and calcification parameters were then chosen for each year and site, as a function of the predominant mussel size, according to the results given in Tagliarolo et al (2012). Because no accurate data were available for L. obtusata, parameters measured for G. pennanti, which has a similar size and distribution, were used (Tagliarolo et al, 2013a).…”

Life in the intertidal: Cellular responses, methylation and epigenetics

“…These data on limpets are validated by physiological differences found between intertidal and subtidal populations of other species. For example, evaluations of clam and mussel species show that intertidal animals exhibit metabolic rate depression, higher rates of anaerobic metabolism, ability for air breathing and greater hypoxia tolerance compared with their subtidal cohorts (Altieri, ; Tagliarolo, Clavier, Chauvaud, Koken, & Grall, ). There are also differences between animals in the two habitats with regard to shell morphology, physiological energetics and fatty acid profiles (Freites, Labarta, & Fernández‐Reiríz, ; Hinch, Bailey, & Green, ; Labarta, Fernández‐Reiríz, & Babarro, ).…”

“…Thermal tolerance can be related to the different thermal histories of the two zones, with intertidal animals regularly exposed to air temperatures in excess of the shallow subtidal waters (Clark, Geissler, et al, 2008). for air breathing and greater hypoxia tolerance compared with their subtidal cohorts (Altieri, 2006;Tagliarolo, Clavier, Chauvaud, Koken, & Grall, 2012). There are also differences between animals in the two habitats with regard to shell morphology, physiological energetics and fatty acid profiles (Freites, Labarta, & Fernández-Reiríz, 2002;Hinch, Bailey, & Green, 1986;Labarta, Fernández-Reiríz, & Babarro, 1997).…”