The effect of the environmental factors on the growth of two epiphytic diatoms Licmophora abbreviata Agardh and L. paradoxa (Lyngbye) Agardh in vitro [harmful species attaching to edible laver Porphyra]

The study deals with the influence of temperature, pH, light intensity, chlorinity and nutrients on the growth of two epiphytic diatoms, Licmophora abbreviata and L. paradoxa in the laboratory culture. They are known to be the harmful species attaching to the edible laver, Porphyra and other algae. Theresults were as follos: 1) The range of the optimal temperature for good growth was 15-25°C in L. abbreviata and 20-25°C in L. paradoxa. 2) The optimal chlorinity was 15-16.5‰ in L. abbreviata and 14-16‰ in L. paradoxa. 3) The optimal pH was not different from each other, 7.8-8.5. 4) The relationship between light intensity and growth was found to vary with the temperature. At 15°C both species showed the optimal growth in the interval from 8, 000 to 20, 000 lx, while at 20°C the optimal growth was from 5, 000 to 20, 000 lx in L. abbreviata and from 5, 000 to 10, 000 lx in L. paradoxa. 5) The cultures in the standard artficial medium (ASP12) and its variations without each nutrient element showed that the growth of both species decreased with lack of inorganic N, inorganic P, Borate and Silicate. Especially lack of inorganic N and Borate caused serious damage to the growth of both species.