The effect of
copper enrichment and salinity on growth, photosynthesis and
copper accumulation of two temperate brown seaweeds, Ascophyllum nodosum and Fucus vesiculosus, was investigated in laboratory experiments. A significant negative impact of reduced salinity on photosynthetic activity and growth was observed for both species. After 15 days at a salinity of 5, photosynthesis of A. nodosum was entirely inhibited and growth ceased at a salinity of 15. Increased
copper concentration negatively affected photosynthetic activity of A. nodosum and F. vesiculosus resulting in
chlorosis and reduced seaweed growth; 5 mg L⁻¹
copper caused an inhibition of the photosynthesis and the degradation of seaweed
tips. Under reduced salinity,
copper toxicity was enhanced and caused an earlier impact on the physiology of seaweed
tips. After exposure to
copper and different salinities for 15 days,
copper contents of seaweeds were closely related to
copper concentration in the water; seaweed
copper contents reached their maximum after 1 day of exposure; contents only increased again when additional, free
copper was added to the water. At high water
copper concentrations or low salinity, or a combination of both,
copper content of A. nodosum decreased. By contrast,
copper content of F. vesiculosus increased, suggesting that different binding sites or uptake mechanisms exist in the two species. The results suggest that when using brown seaweeds in biomonitoring in situ, any change in the environment will directly and significantly affect algal physiology and thus their
metal binding capacity; the assessment of the physiological status of the algae in combination with the analysis of thallus
metal content will enhance the reliability of the biomonitoring process.