EFFECTS OF SALINITY AND BROMINE ON ZYGOTES AND EMBRYOS OF FUCUS-VESICULOSUS FROM THE BALTIC SEA

Zygotes and young embryos derived from Fucus vesiculosus collected in the archipelgo of Stockholm in 1990, growing at a salinity of 6 to 7 parts per thousand S. were cultured under different salinity conditions and in media of different bromine concentrations. Optimum salinity was 10 to 12 parts per thousand S for germination (rhizoid initiation) while apical hair formation showed a broader tolerance curve with an optimum at 8 to 14 parts per thousand S. Bromine caused inhibition of early development of F. vesiculosus. At 6 parts per thousand salinity a 50% reduction in germination took place at 10.0 mM Br and at 1.25 mM Br only 4.7% of the embryos developed apical hairs, as compared to 32.7% in the control. Bromine toxicity decreased at higher salinities. The results indicate that F. vesiculosus in the Baltic Sea has diverged from its Atlantic progenitors and to some extent acclimated to low salinity. Still, the salinity in the normal environment of the tested population is lower than optimum, leading to a lower degree of germination of zygotes, a lower growth rate of young embryos and probably also a higher sensitivity to additional stress factors such as chemical pollution.