Interactive Effects of Increased Temperature and pCO₂ Concentration on the Growth of a Brown Algae Ecklonia cava in the Sporophyte and Gametophyte Stages

Abstract

To examine the effects of increased CO 2 concentration and seawater temperature on the photosynthesis and growth of forest forming Ecklonia cava (Laminariales, Phaeophyta), sporophytic discs and gametophytes were cultured under three pCO 2 concentrations (380, 750, 1000 ppm), four temperatures (5, 10, 15, 20 o C for sporophytes; 10, 15, 20, 25 o C for gametophytes), and two irradiance levels (40, 80 µmol photons m −2 s −1) for 5 days. Photosynthetic parameter values (ETR max , E k , and α) were generally higher as sporophytic discs were grown under low temperature and increased CO 2 concentration at 750 ppm. However, photosynthesis of Ecklonia sporophytes was severely inhibited under a combination of high temperature (20 o C) and 1000 ppm CO 2 concentration at the two photon irradiance levels. The growth of gametophytes was maximal at the combination of 380 ppm (present seawater CO 2 concentration) and 25 o C. Minimal growth of gametophytes occurred at enriched pCO 2 concentration levels (750, 1000 ppm) and high temperature of 25 o C. The present results imply that climate change which is increasing seawater temperature and pCO 2 concentration might diminish Ecklonia cava kelp beds because of a reduction in recruitments caused by the growth inhibition of gametophytes at high pCO 2 concentration. In addition, the effects of increased temperature and pCO 2 concentration were different between generations-revealing an enhancement in the photosynthesis of sporophytes and a reduction in the growth of gametophytes.

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

“…Efforts to develop strains with high temperature tolerance have been conducted in some kelps (Gao et al, ; Pang, Jin, Sun, & Gao, ). As another limited factor, OA could suppress early development of kelp species (Gaitán‐Espitia et al, ; Oh et al, ; this study). As a result, the acidic and warmer seawater in the future years may prolong seedling production process before outplanting to the sea and even result in its failure.…”

“…Additionally, compared to the positive effect on E. stolonifera photosynthesis at 720 ppmv, negative effect was detected at higher 980 ppmv. Reversal of positive effects from increased pCO 2 was also detected in E. cava , which responded with enhanced photosynthesis with increased pCO 2 from 380 to 750 ppmv but exhibited negative impacts when pCO 2 further increased to 1,000 ppmv (Oh et al, ). These indicate that beneficial effect of elevated pCO 2 may be reduced if values are more than twice the present level, supported by a previous finding for Lobophora papenfussii (Diaz‐Pulido, Gouezo, Tillbrook, Dove, & Anthony, ).…”

“…Detrimental effects of high temperatures have been also documented in other kelps with narrow distribution range in polar and temperate zones. Oh et al () revealed that photosynthetic parameters of E. cava sporophytes were significantly lower at 15°C than at 10°C. Zoospores of L. digitata and Laminaria hyperborea from the Arctic and North Sea showed inhibition or decreased germination at 18°C than at lower temperatures (Müller, Wiencke, & Bischof, ).…”

“…Positive and/or negative effects of OA and OW on the ecophysiological performance of kelp species were recorded for sporophyte growth (Brown, Edwards, & Kim, ; Iñiguez et al, ) and recruitment (Gaitán‐Espitia et al, ; Leal, Hurd, Fernández, & Roleda, ). Sporophytic photosynthesis of Macrocystis pyrifera was stimulated with increased temperature (from 12 to 15°C) and pCO 2 (from 500 to 1,500 ppmv) together (Brown et al, ), whereas photosynthesis of Ecklonia cava sporophytes was different: declined with increased temperature from 15 to 20°C and stimulated with increased pCO 2 concentration from 380 to 750 ppmv (Oh, Yu, & Choi, ). In microscopic stage, germination rates and survival rates of M. pyrifera spores revealed remarkable decrease under combined culture conditions of increased pCO 2 and temperature (Gaitán‐Espitia et al, ).…”

Crossed Effects of Light and Temperature on the Growth and Maturation of Gametophytes in Costaria costata and Undaria pinnatifida

“…( 고 찰 , , (Choi et al, 2008;Oh et al, 2015). , ( , ) Kim et al, 2007a;Choi et al, 2008), ( ) (Saito, 1975).…”