Physiological responses and scope for growth of Ruditapes decussatus from Ria Formosa, southern Portugal, exposed to increased ambient ammonia
P. Sobral, S. Fernandes

In this study we investigate the effects of exposure to increased ambient ammonia-N concentrations as a cause of decreased scope for growth and mortality of R.decussatus during the summer months in Ria Formosa, southern Portugal. The physiological measurements were performed at 20°C and average total ammonia-N concentrations (TA-N) were 9, 48, 85, 134 and 260 µmol l-1 (corresponding to 0.2, 1.1, 2.0, 3.2 and 6.2 µmol l-1 NH3). No mortality was observed. Our results show that during short term exposure to TA-N concentrations >48 µmol l-1 (1.1 µmolNH3), R.decussautus survives at the expense of energy reserves. No energy is available for growth and reproduction. Though it is uncertain how intermittent exposures during tidal cycles will affect the long-term survival of R.decussatus in the Ria Formosa, high ammonia concentrations together with unfavourable physical and chemical summer gradients in the sediment can clearly contribute to the high mortality that has been registered in recent years (Ferreira et al. 1989). The sensitivity of the physiological energetics approach and the need to assess tolerance of infaunal bivalves addressing endpoints that can provide insight into the condition for growth and reproduction of the population is stressed.

Keywords: ambient ammonia, physiological energetics, scope for growth, Ruditapes decussatus.
Contents of this volume Sci. Mar. 68(2) : 219-225 Back PDF
Please, send comments to
ICM (CSIC) - Passeig Marítim de la Barceloneta, 37-49. E-08003 Barcelona (Spain)