Changes in microbial communities, photosynthesis and calcification of the coral Acropora gemmifera in response to ocean acidification

Abstract

With the increasing anthropogenic CO2 concentration, ocean acidification (OA) can have dramatic effects on coral reefs. However, the effects of OA on coral physiology and the associated microbes remain largely unknown. In the present study, reef-building coral Acropora gemmifera collected from a reef flat with highly fluctuating environmental condition in the South China Sea were exposed to three levels of partial pressure of carbon dioxide (pCO2) (i.e., 421, 923, and 2070 μatm) for four weeks. The microbial community structures associated with A. gemmifera under these treatments were analyzed using 16S rRNA gene barcode sequencing. The results revealed that the microbial community associated with A. gemmifera was highly diverse at the genus level and dominated by Alphaproteobacteria. More importantly, the microbial community structure remained rather stable under different pCO2 treatments. Photosynthesis and calcification in A. gemmifera, as indicated by enrichment of δ18O and increased depletion of δ13C in the coral skeleton, were significantly impaired only at the high pCO2 (2070 μatm). These results suggest that A. gemmifera can maintain a high degree of stable microbial communities despite of significant physiological changes in response to extremely high pCO2.

Diversity and stability of coral endolithic microbial communities at a naturally high pCO2 reef

“…Because the ocean pH naturally changes throughout seasons, along depth gradients, with productivity and other biological factors, marine micro‐organisms may have the physiological plasticity required to cope with the predicted levels of OA over the next 100 years (Joint, Doney, & Karl, ). This notion is supported by several studies showing stable coral prokaryotic community when shifted from ambient to high CO 2 partial pressure ( p CO 2 ) and therefore reduced sea water pH conditions (Meron et al., ; Webster, Negri, Botte, Laffy, & Flores, ; Zhou, Yuan, Cai, Zhang, & Tian, ). However, other studies have demonstrated that a reduced sea water pH can lead to the loss of Symbiodinium (coral bleaching) and trigger shifts from a healthy microbiome composition to a microbial community typically associated with diseased corals (Anthony, Kline, Diaz‐Pulido, Dove, & Hoegh‐Guldberg, ; Vega Thurber, Willner‐Hall, Rodriguez‐Mueller, Desnues, & Edwards, ; Meron et al., ; Webster, Negri, Flores, Humphrey, & Soo, ; Morrow, Bourne, Humphrey, Botte, & Laffy, ).…”

Coral Bacterial-Core Abundance and Network Complexity as Proxies for Anthropogenic Pollution

“…This genus has been described as being vertically transmitted from parent to offspring in M. hispida ( Leite et al, 2017 ), which suggests a potential key role of this group for the holobiont. On the other hand, the genus Acinetobacter has been detected in a wide range of hosts ( Wegley et al, 2007 ; Shnit-Orland and Kushmaro, 2009 ; Sweet et al, 2013 ; Li Y. et al, 2014 ; Badhai et al, 2016 ; Meyer et al, 2016 ; Zhou et al, 2016 ; Leite et al, 2017 ), including many tropical corals ( Wegley et al, 2007 ; Sweet et al, 2013 ; Leite et al, 2017 ), where this genus has been considered as an effective first line of defense ( Santos et al, 2015 ; Leite et al, 2017 ) and also as potential pathogens ( Shnit-Orland and Kushmaro, 2009 ; Sweet et al, 2013 ; Li J. et al, 2014 ; Meyer et al, 2016 ).…”

Symbiodinium Functional Diversity in the Coral Siderastrea siderea Is Influenced by Thermal Stress and Reef Environment, but Not Ocean Acidification

“…Some studies report that elevated pCO 2 enhances Symbiodinium primary production, suggesting that the concentration of dissolved inorganic carbon in seawater-elevated under high pCO 2 -is the limiting substrate for photosynthesis (Crawley et al, 2010;Brading et al, 2011). In contrast, others have observed negative effects of increased pCO 2 on Symbiodinium physiology, including reduced productivity, photochemical efficiency, and calcification (Anthony et al, 2008;Zhou et al, 2016). Here, we observed minimal effects of elevated pCO 2 on Symbiodinium photochemical efficiencies across a wide range of pCO 2 conditions ( Figure 1A).…”