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 Cu effects on various physiological parameters. •  Chlorophyll fluorescence, oxygen evolution, copper content, and relative growth rate of embryos and adults were measured on Cu -exposed material. •  Algae naturally exposed to elevated total Cu concentration (Cu ), were more Cu resistant than those from clean sites, as indicated by higher embryo and adult growth rates and lower copper contents. The Cu tolerance of F. serratus is at least partly inherited and relies partly on metal exclusion. •  There were inhibitory effects of Cu on oxygen exchange rates in both tolerant and non-tolerant algae. By contrast to sensitive algae, the maximum efficiency of photosystem II (F /F ), maximum fluorescence (F ) and zero fluorescence (F ) of resistant algae were unaffected by Cu , whereas decreased quantum yield (ΦPSII) and increased nonphotochemical quenching (NPQ) were most pronounced in resistant algae. Inhibitory effects of Cu 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.