Inter-population differences in inherited copper tolerance involve photosynthetic adaptation and exclusion mechanisms in Fucus serratus.

•  A comparative study of copper (Cu) toxicity and tolerance in three populations of Fucus serratus was conducted by examining Cu2+ effects on various physiological parameters. •  Chlorophyll fluorescence, oxygen evolution, copper content, and relative growth rate of embryos and adults were measured on Cu2+ -exposed material. •  Algae naturally exposed to elevated total Cu concentration (CuT ), were more Cu2+ resistant than those from clean sites, as indicated by higher embryo and adult growth rates and lower copper contents. The Cu2+ tolerance of F. serratus is at least partly inherited and relies partly on metal exclusion. •  There were inhibitory effects of Cu2+ on oxygen exchange rates in both tolerant and non-tolerant algae. By contrast to sensitive algae, the maximum efficiency of photosystem II (Fv /Fm ), maximum fluorescence (Fm ) and zero fluorescence (Fo ) of resistant algae were unaffected by Cu2+ , whereas decreased quantum yield (ΦPSII) and increased nonphotochemical quenching (NPQ) were most pronounced in resistant algae. Inhibitory effects of Cu2+ on ΦPSII may result in the excitation energy being dissipated through xanthophyll-dependent quenching mechanisms in tolerant algae. In nontolerant algae, lower energy dissipation may result in chlorophyll degradation.