Sporophytic photosynthesis and gametophytic growth of the kelp Ecklonia stolonifera affected by ocean acidification and warming

Abstract

Juvenile sporophytes and gametophytes of Ecklonia stolonifera were incubated in combinations of three pCO(2) levels (360, 720 and 980 ppmv) and two temperatures (10 and 15 degrees C for sporophytes; 15 and 20 degrees C for gametophytes) to examine potential effects of climate change on photosynthesis and growth. Sporophytes had significantly higher maximum quantum yields (F-v/F-m) and maximum relative electron transport rates (rETR(max)) at 720 ppmv than 360 and 980 ppmv. Also, these parameters were significantly lower at higher temperature of 15 degrees C than at 10 degrees C. Growth of female gametophytes was maximal at 360 ppmv rather than enriched pCO(2) levels. Female gametophytes had significantly lower growth at higher temperature of 20 degrees C than at 15 degrees C. These results indicate effects of elevated pCO(2) varied between generations: stimulating sporophytic photosynthesis and inhibiting gametophytic growth. Ocean acidification and warming would constitute a grave threat to seedling cultivation of E. stolonifera caused by growth inhibition of gametophytes at high pCO(2) levels and temperatures.