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Algal density alleviates the elevated CO 2 ‐caused reduction on growth of Porphyra haitanensis (Bangiales, Rhodophyta), a species farmed in China
Author(s) -
Li Gang,
Mai Guangming,
Zhang Jiejun,
Lin Qiang,
Ni Guangyan,
Tan Yehui,
Huang Liangmin,
Zou Dinghui
Publication year - 2020
Publication title -
aquaculture research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.646
H-Index - 89
eISSN - 1365-2109
pISSN - 1355-557X
DOI - 10.1111/are.14735
Subject(s) - biology , photosynthesis , phycocyanin , relative growth rate , chlorophyll a , algae , botany , photosystem ii , thallus , photosystem , gracilaria , photosynthetic efficiency , phycoerythrin , growth rate , cyanobacteria , flow cytometry , genetics , geometry , mathematics , bacteria
Growing of Pyropia haitanensis, a commercially farmed macroalga, usually increases their densities greatly during cultivation in natural habitats. To explore how the increased algal densities affect their photosynthetic responses to rising CO 2 , we compared the growth, cell components and photosynthesis of the thalli of P. haitanensis under a matrix of pCO 2 levels (ambient CO 2 , 400 ppm; elevated CO 2 , 1,000 ppm) and biomass densities [low, 1.0 g fresh weight (FW) L −1 ; medium, 2.0 g FW L −1 ; high, 4.0 g FW L −1 ]. Under ambient CO 2 , the relative growth rate (RGR) was 5.87% d −1 , 2.32% d −1 and 1.51% d −1 in low, medium and high densities, and elevated CO 2 reduced the RGR by 27%, 25% and 12% respectively. Maximal photochemical quantum yield of photosystem II (F V /F M ) was higher in low than in high densities, so were the light‐utilized efficiency ( α ), saturation irradiance (E K ) and maximum relative electron transfer rate (rETR max ). Elevated CO 2 enhanced the F V /F M in low density but not in higher densities, as well as the α, E K and rETR max . In addition, elevated CO 2 reduced the content of chlorophyll a and enhanced that of carotenoids, but unaffected phycoerythrin, phycocyanin and soluble proteins. Our results indicate that the increased algal densities reduced both the growth and the photosynthesis of P. haitanensis and alleviated the elevated CO 2 ‐induced negative impact on growth and positive impact on photosynthesis. Moreover, the elevated CO 2 ‐induced reduction on growth and promotion on photosynthesis indicates that rising CO 2 may enhance the loss of photosynthetic products of P. haitanensis through releasing organic matters.