Cell wall organic matrix composition and biomineralization across reef‐building coralline algae under global change

Abstract

Crustose coralline algae (CCA) are one of the most important benthic substrate consolidators on coral reefs through their ability to deposit calcium carbonate on an organic matrix in their cell walls. Discrete polysaccharides have been recognized for their role in biomineralization, yet little is known about the carbohydrate composition of organic matrices across CCA taxa and whether they have the capacity to modulate their organic matrix constituents amidst environmental change, particularly the threats of ocean acidification (OA) and warming. We simulated elevated pCO2 and temperature (IPCC RCP 8.5) and subjected four mid‐shelf Great Barrier Reef species of CCA to 2 months of experimentation. To assess the variability in surficial monosaccharide composition and biomineralization across species and treatments, we determined the monosaccharide composition of the polysaccharides present in the cell walls of surficial algal tissue and quantified calcification. Our results revealed dissimilarity among species' monosaccharide constituents, which suggests that organic matrices are composed of different polysaccharides across CCA taxa. We also observed that species differentially modulate composition in response to ocean acidification and warming. Our findings suggest that both variability in composition and ability to modulate monosaccharide abundance may play a crucial role in surficial biomineralization dynamics under the stress of OA and global warming.

Hierarchical settlement behaviours of coral larvae to common coralline algae

“…Alternatively, microbially derived cues have also been identified as important inducers of coral larval settlement and these vary amongst CCA taxa 15 , 31 . It is also possible that cues from both the algal and microbial components interact to modulate coral settlement, as shown for Acropora on the GBR 30 , and it is also plausible that the nature of these cues is species-specific, given the large variability in surficial microbiome composition across CCA taxa 22 , 31 , 34 , 35 and chemical constituents of the alga thallus 36 . Detailed microbiome and metabolomic studies across a range of coral and algal taxa (e.g.…”

New branched Porolithon species (Corallinales, Rhodophyta) from the Great Barrier Reef, Coral Sea, and Lord Howe Island

“…This is particularly important when considering the several synonymies previously suggested. Furthermore, species of Porolithon are one of the most sensitive to the impacts of ocean acidification (Anthony et al, 2008; Bergstrom et al, 2023; Diaz‐Pulido et al, 2012; Johnson & Carpenter, 2012; Page et al, 2022). An accurate delimitation of the species and a better understanding of their diversity and phylogenetic relationships will help elucidate their biogeographical and ecological roles, and their vulnerabilities to environmental change and potential to adapt to a rapidly changing climate.…”