One of the building blocks of the Great Barrier Reef could be in danger

By PhD Candidate Tessa Page,

Read Time: 404 words about 3 minutes.

Our new research has revealed adults from one species of reef building coralline algae may be somewhat resilient to the degree of change oceans are predicted to endure by year 2100.  

As humans continue to emit CO2 into the atmosphere at an unprecedented rate, major changes are occurring in our oceans, such as an increase in average ocean temperature and a decrease in average ocean pH, also known as ocean acidification. These major changes are impacting marine ecosystems and organisms worldwide. Coral reefs and their multiplicity of inhabitants are thought to be amongst the most threatened by these global changes. Therefore, it is essential we continue to study and understand the effects of global change on coral reefs as a whole and the responses of organisms living within them.  

Great Barrier Reef. Photo: Guillermo Diaz-Pulido.

Coral reefs are cemented together by a group of algae called crustose coralline algae (CCA). CCA are calcifying, red macroalgae that contribute significantly to reef growth and cementation. CCA also play an extremely important role of inducing the settlement and metamorphosis of coral larvae and other benthic organisms.  

Coral reefs are cemented together by a group of algae called crustose coralline algae (CCA). CCA are calcifying, red macroalgae that contribute significantly to reef growth and cementation.

Past studies have shown CCA to be variably affected by changes in their environment, such as elevated temperature and reduced pH levels, with decreases, increases, or no changes in aspects such as, but not limited to, survival, abundance, calcification, photosynthesis, and growth. However, most of this work has been primarily done on the adult stages of CCA and not for extended periods of time.  

A close up shot of the alga, Sporolithon. Photo: Tessa Page.

In our recent research in the Great Barrier Reef, Australia, we compared two different life stages, adults and germlings (babies), of the CCA species Sporolithon durum, to elevated temperature and reduced pH for 3 – 5 months. We found that the adult stages of this reef-building CCA are robust to elevated temperature and declining pH, but the germlings of the first generation are sensitive to ocean acidification and warming. Our study suggests life history stage plays an important role in resilience to global change variables and although there may be a positive outlook for adult S. durum to acclimate to future ocean conditions, the sensitivity of S. durum germlings to environmental stressors complicates this species persistence in future oceans.   

Author’s Twitter:

@tessmpage

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