Effects of varying CO₂, Nutrient and Light Irradiance Levels on the Growth of Ulva australis at Germling, Juvenile, and Adult Stages

Abstract

The effects of CO 2 concentration, nutrient levels, and irradiance on the growth of germlings and juveniles, and on the photosynthesis of adults were examined in a green tide alga, Ulva australis. We used a factorial experimental design with two CO 2 concentrations (380 and 750 ppm), two nutrient levels (control and PES medium), and two irradiance levels (50 and 100 μmol photons m -2 s -1 ). Germlings grew best (664.15±61.45 μm in length) under conditions of 750 ppm, PES, and 100 μmol photons m -2 s -1 after 10 days in culture. Relative growth rates (RGR) of the juveniles were greatest (4.41% day -1 ) under conditions of 750 ppm, PES, and 50 μmol photons m -2 s -1 after 5 days in culture. Photosynthetic efficiency (F v /F m ) of the adult discs was 0.73 ± 0.05 before the experiment and reached a maximum (0.83±0.01) under conditions of 750 ppm, control, and 50 μmol photons m -2 s -1 after 5 days in culture. Growth (germlings and juveniles) and photosynthesis (adult discs) of Ulva australis increased when CO 2 levels were 750 ppm. Additionally, the optimal irradiance for growth and photosynthesis differed among stages, wherein germlings grew best at 100 μmol photons m -2 s -1 , juveniles grew best at 50 μmol photons m -2 s -1 , and adults photosynthesized most at 50 μmol photons m -2 s -1 . The performance of Ulva australis at all examined life stages was enhanced under the PES nutrient treatment. In conclusion, the physiological responses of U. australis to varying CO 2 , nutrient, and irradiance levels differed slightly among life stages. However, growth and photosynthesis always increased with elevated CO 2 and nutrient concentrations. These results indicate that U. australis green tide blooms might occur more frequently in coastal areas if CO 2 and nutrient concentrations increase.

Effects of Environmental Factors on the Zoospore Release and Germling Growth of the Green Macroalga Chaetomorpha linum

“…해조류는 전 세계적 분포를 보이며, 배우체와 포자체가 세대교번하 는 생활사를 가진다. 염주말류에서 대발생을 일으키는 몇 종은 매트 형성으로 대기와 해양 사이에 생물학적 장벽을 형성하여 광투과 억제, 저산소증(혹은 산소 결핍)으로 해 조류의 군집구조 단순화와 종다양성 감소를 초래하고 다 른 해양생물의 생장, 생식 및 종다양성 감소를 가져온다고 하였다 (Xu and Lin 2008;Nelson et al 2010;Deng et al 2011a;Renjun et al 2013;Gavio and Mancera-Pineda 2015;Jeon et al 2015). 한 예로, 호주와 뉴질랜드가 원산 지인 Chaetomorpha valida는 중국의 Dalian 해안에 유입 되어 봄·여름에 대발생을 일으켰고 산동성의 Rongchent에 서는 2008년에 대량으로 번무하여 전복과 해삼의 성장을 억제하고 수질을 악화시켜 막대한 경제적 손실을 가져온 유해종이 되었다 (Chi et al 2009;Deng et al 2011aDeng et al , 2011bDeng et al , 2012Deng et al , 2013.…”