Bioavailable organic matter in seston modulating differential absorption rates by mussels

Our results showed a strong correlation between C-BPC and both the organic fraction (f) and the carbon equivalent of Chloropyll-a (C-Chl-a) in the seston. This fact points to variations in C-BPC (predominantly composed of proteins) are strongly linked with the phytoplankton fluctuations, which in turn are modulated by the seasonal upwelling regime. Maximum total energy absorbed by mussels (about 97%) occurred during the spring phytoplankton bloom, when high-quality organic carbon (high C-BPC) dominated the seston. Minimum energy absorbed (56%) occurred during winter, when continental runoff and local resuspension of surface sediments reintroduce into the water column more refractory organic compounds not favourable to the mussel diet. These results allowed us to establish that parameters such as f, C-Chl-a, and C-BPC have close correlations with physiological responses in mussels and could be used as proxies for food quality. Nonetheless, the use of these high-quality food estimations should be considered according to particularities of each ecosystem.