Reproductive performance and growth response of the red alga Ceramium strictum under the impact of phenol

The toxic effect of phenol on 3 stages in the reproduction of the red alga Ceramium strictum was studied, i.e. the formation of reproductive organs, fertilisation capacity and maturation of cystocarps. Male and female gametophytes were exposed separately to different concentrations of phenol for 3 d. Thereafter, experiments were conducted in which fertilisation and maturation of cystocarps were studied either with or without phenol present. The reproductive capacity was examined for all possible crossings of exposed and unexposed male and female gametophytes and the results were measured as the number of cystocarps produced. The development of reproductive organs on both female and male gametophytes was affected by phenol. The formation of female reproductive organs was about 20 times more sensitive than the reproductive functioning of the male spermatangium. Thus, a 50 % reduction in reproductive capacity was estimated at around 5 to 7 and 100 mg phenol l(-1), respectively. The effect of phenol on the female gametophyte during fertilisation was decisive for the outcome of reproduction. The maturation of cystocarps was affected to a lesser extent. After fertilisation had taken place in phenol, a 20 % decrease in reproductive capacity was observed when the maturation of cystocarps had taken place in phenol rather than in clean water. Thus, all 3 investigated phases were inhibited by phenol. The strongest and most permanent negative effect was seen on the reproductive organs of the female gametophyte. Marked changes in the morphological appearance of the female plants were noted when exposed for 3 different time periods, i.e. i, 3 and 10 d. At a concentration of 10 mg phenol l(-1) a loss of apical dominance was observed and instead of the normal dichotomous growth with very few branches, most cells initiated an extra lateral branch. This response was more pronounced at increasing phenol concentrations. A 24 h pulse exposure to phenol of more than 60 mg l(-1) influenced the growth pattern by as much as a week.