| dc.description.abstract | Past ocean acidification recorded in the geological record facilitates the
understanding of rates and influences of contemporary pCO2 enrichment. High
resolution proxies of pCO2 and pH can be used to reconstruct components of the
palaeocarbonate system. At present, most pH reconstructions are made using
boron isotopes, however, there is some uncertainty associated with vital effects and
isotopic fractionation. In addition to contemporary ocean acidification, marine
organisms currently experience thermal stress associated with increasing
atmospheric temperatures. Here we present a study of the influences of multiple
stressors on the growth and structure of a marine carbonate, predicted to occur
within this century, and a novel structural proxy for carbonate chemistry; Mg-O
bond strength in coralline algae. Free living Lithothamnion glaciale algae were
incubated in control (380ppm pCO2), moderate acidification (750ppm pCO2) and
high acidification (1000ppm pCO2) at ambient and enhanced (+2°C) temperature
conditions for 24 months. Coralline algae growth (linear extension) was highly
dependent on temperature, with +2°C samples experiencing significantly reduced
growth. No significant correlation was found between pCO2 and growth, indicating
L. glaciale’s ability to acclimatize. Relative magnesium concentration and Mg-O
bond strength within the high-Mg skeleton cyclically over an annual cycle. For all
seasons there was a positive linear relationship between pCO2 concentration and
bond strength mediated by positional disorder of the calcite lattice. Structural
preservation of the carbonate chemistry system in coralline algal high Mg calcite
represents an alternative approach to reconstructing marine carbonate chemistry
parameters based on skeletal structure rather than chemistry. | en |
