Effects of lead (PaCl2) on photosynthesis and respiration of the bladder wrack, Fucus vesiculosus, in relation to different salinities

The photosynthetic and respiratoric capacity of Fucus vesiculosus grown at three different levels of salinity (4.5, 8 and 20 parts per thousand) was studied in the presence of different concentrations of lead (5, 10, 15, 20, 25, and 30 mg PbCl2 L-1). The studies were performed by using a light-pipette, which has a precisely defined light source of photosynthetic active radiation (PAR, 400-700 nm). The photosynthetic and respiratoric capacity of the algae were measured when exposed to light pulses with increasing irradiance and after 24 hr in seawater with the addition of lead. The results indicate that the photosynthetic capacity of F. visiculosus from 20 parts per thousand is more sensitive to lead compared to those from 8 and 4.5 parts per thousand. The photosynthetic capacity was reduced by 69% at 30 mg PbCl2 L-1 compared to the control alga. The photosynthetic capacity of F. vesiculosus from 8 and 4.5 parts per thousand was reduced by 38 and 15%. The respiratoric capacity of F. vesiculosus from 20 parts per thousand was reduced by 41% at 30 mg PbCl2 L-1. However, the respiratoric capacity of the algae from 4.5 parts per thousand increased by 55% at the same concentration of PbCl2. The results indicate that lead showed inhibitory effects on photosynthesis but a stimulatory effect on respiration of F. versiculosus grown at low levels of salinity.