06 April: A window into the future reveals a grim reality for crustose coralline algae

AIMS scientists, in collaboration with external researchers, provide conclusive evidence of the vulnerability of crustose coralline algae (CCA) to ocean acidification. CCA play an important role in many marine ecosystems, for example, by providing the building blocks for coral reef development.

Field observations made over a period of 13 months indicate that a pH decline (a median pH <7.7) coupled with low light conditions reduce CCA cover close to zero, highlighting the vulnerability of CCA to environmental changes. The data show that individuals are most sensitive in their early life history stages. At the very least, it seems that low pH can interfere with growth and development, at the very worst – it can diminish survival rates.

The findings of this study also suggest that an understanding of what happens during the early life stages is crucial for making more accurate conclusions about the vulnerability of CCA crusts. Most concerning is that without consideration of the early life vulnerabilities, researchers may be severely underestimating the effects of CO₂ on future CCA populations.

Shallow volcanic CO₂ seeps found in eastern Papua New Guinea have provided scientists a unique natural laboratory to undertake this goundbreaking research, under real-world conditions of temperature, light, currents, and grazing. The study published in the Nature journal ‘Scientific Reports’ this month is part of a suite of experiments that seeks to improve knowledge about the impacts of ocean acidification on marine ecosystems.

The research was supported by a grant from the National Geographic Society Committee for Research and Exploration.

*ocean acidification is defined here as “the rapid global decline in surface seawater pH (normally ~pH 8) and associated changes in the seawater carbonate chemistry from rising atmospheric CO₂”.