Hypo-osmotic soaking shows potential as a selective method of removing Ceramium filicula, the dominant epiphyte causing serious damage to Gracilariopsis lemaneiformis cultivation in China

Abstract

A massive outbreak of epiphytes has caused serious damage to Chinese G. lemaneiformis cultivation during the past two years. The dominant species of the epiphytes from Dongshan and Rongcheng, two main cultivation districts, were identified from their molecular and morphological profiles. An effective method for removing the epiphyte from the infected G. lemaneiformis has been developed. Based on our results, the dominant epiphyte on cultivated G. lemaneiformis is a red filamentous alga, Ceramium filicula. Fifteen hours of freshwater soaking at a temperature of 20 °C–30 °C not only reduced the vitality of the C. filicula, but also caused no obvious damage to the G. lemaneiformis cuttings. The daily GR of freshwater-soaked G. lemaneiformis was 4.01%, which was significantly higher than that of the untreated group (1.26%) and manually cleaned group (2.1%). Freshwater immersion appears to be an economical and environmentally friendly method for removing C. filicula from G. lemaneiformis.