Fig. 6

Level of oxygen production (a), carotenoids (b), chlorophyll a (c) and chlorophyll b (d) in the marine alga Ulva compressa cultivated in seawater without copper addition (open circles) and with 10 μM copper (black circles) for 0 to 24 h. The level of oxygen is expressed as nanomoles per microliter per minute, the level of carotenoids is expressed in micrograms per milligram of fresh tissue (FT) and time is expressed in hours. Symbols represent mean values of three independent experiments ± SD. Different letters indicate significant differences (P < 0.05)