Effects of Various Physical and Chemical Factors on the Death of Trouble Seaweed Ulva australis

Jin-Seog  Kim1,*   Hwa Sook  Kwak1   Bo Gwan  Kim1   

1EResearch Center for Eco-Friendly New Materials, Bio & Drug Discovery Division, Korea Research Institute of Chemical Technology,

Abstract

Green tides, which was mainly caused by Ulva spp., have been increasing in severity and frequency globally, and have negatively affected on marine ecosystems. This study was conducted to investigate effects of various physical and chemical factors on the death of Ulva australis (ULAUS) and to consider a practical measures useful for alleviating Ulva bloom. Soaking of ULAUS thalli in pure water for 8 hr didn’t induce a death, but incubation in 1.0-1.5% salinity for 7 d inhibited sporulation by about 70%. Desiccation gave rise to a serious damage when more than 40-50% of initial fresh weight was lost. ULAUS growth was sensitive to temperature and seriously inhibited from more than 30°C. At 35°C, 40°C, 45°C and 50°C, treatment time required for 90-95% death of ULAUS thalli was 1 d, 10 min, 30 sec, and 1 sec, repectively. ULAUS growth was seriously inhibited at lower than pH 6.0 and completely dead at pH 4.0. Several compounds for ULAUS control was selected and the chemcals causing a rapid death were oxidants such as hydrogen peroxide and sodium percarbonate. Taken together, our results suggest that low salinities, dryness, pH, high temp. and compounds could be selected for Ulva bloom control, and high temperature and compounds seems to be useful for a development of practical control methods.

Acknowledgements

This research has been performed as a project No SKO1707C31 (Eco-friendly control methods for preventing the algal bloom of Ulva spp. in the seashore) and supported by the Korea Research Institute of Chemical Technology (KRICT).

Figures & Tables

Effect of dryness in growth room (20°C) on the death of thallus disc excised from Ulva australis. A: Fresh weight decrease by dryness time, B: Death % vs fresh weight decrease, C: Death % vs decreased % of moisture contents in disc.