Developing a climate change resilience index for the Great Barrier Reef: Part 1

Bill Dennison ·
18 February 2014
Science Communication | 

Heath Kelsey and I traveled to Townsville, Australia to facilitate a workshop to develop a climate change resilience index for the Great Barrier Reef. The workshop, sponsored by the Great Barrier Reef Foundation, was at James Cook University on 10-11 Feb 2014. On the first day, we had a series of presentations by scientists developing various indicators and then on the second day we designed and drafted a trifold publication for internal use by the Great Barrier Reef Foundation. Eva Abal and Emily Saeck from the Great Barrier Reef Foundation organized the workshop.

Climate change resilience index workshop at James Cook University.

Volcanic seeps: Katharina Fabricius from the Australian Institute of Marine Science presented her exciting research from some natural volcanic seeps off the coast of Papua New Guinea. These seeps elevate the dissolved carbon dioxide concentrations which offer a glimpse into the future climate scenarios where elevated atmospheric carbon dioxide concentrations will result in higher dissolved carbon dioxide in surface waters of the ocean. Katharina has observed the decline in sensitive tabular and plate corals, with lush seagrasses and one type of coral (Porites) remaining at the highest carbon dioxide concentrations. She uses three seep sites and appropriate controls sites. The dissolved carbon dioxide concentrations regulate pH, and when seawater pH values, normally around 8.2, go below 8.1, major changes are observed until 7.8, which appears to be the lower limit for corals.

Coral health: Bill Leggat from James Cook University presented an interesting approach of using mass spectroscopy to determine the concentrations of a large suite of metabolites, bioactive compounds, in coral samples. By determining a suite of metabolites, a series of biomarkers for climate resilience could be identified. The entire coral colony is used, including the cnidarian animal, the symbiotic dinoflagellate, endolithic algae and the associated microbial community, which makes sampling fairly easy. This method could be very sensitive and signs of stress or recovery from disturbance could be discerned using biomarkers even if there are no morphological or physiological manifestations evident.

Calcareous coralline algae: Guillermo Diaz-Pulido from Griffith University studies the growth of the 'crusts' of red algae that photosynthesize and calcify on hard substrates. These calcareous coralline algae (CCA) are also sensitive to ocean acidification and their rate of growth can be measured as a climate change indicator. CCA are particularly sensitive to ocean acidification due to their high magnesium calcite form of calcium carbonate. Colonies can be 800 years old and thicken over a millimeter per year. CCA also respond to temperature with a mid range optimum.

Habitat complexity: Tom Bridge from James Cook University is using an autonomous underwater vehicle (AUV) to survey coral reefs using three dimensional photography. These images can be analyzed for structural complexity and community composition. The stereoscopic images of the reef generated from this technique is quite impressive visually. Tom can discern communities of tabular and plate corals, branching and boulder corals, macroalgae, and other features to detect phase shifts in coral reef communities. I was glad to learn that he plans to compare the current AUV data with historical MUV data (Manual Underwater Vehicle = Terry Done).

Foraminifera: Maria Byrne from the University of Sydney opened our eyes to minute but very important components of the coral reef ecosystem, the single celled protists known as foraminifera. These beautiful little animals (solar-powered protists) have a variety of different symbiotic algae living with them. While they are alive, they can photosynthesize and deposit calcium carbonate just like corals, and after they die, they produce sand, which becomes important habitat for benthic microalgae (= microphytobenthos). Forams are quite sensitive to ocean acidification, thus they are good candidates for climate change indicators.

Seagrasses: Catherine Collier from James Cook University is a former University of Queensland Marine Botany group member who studies seagrasses. Seagrasses are flowering plants that are found from the intertidal to the deep inter-reefal areas can actually thrive in more acidic seawater. They evolved from land plants tens of millions of years ago when global carbon dioxide concentrations were much higher than today. Seagrasses can actually photosynthesize faster in a more acid ocean. The Great Barrier Reef contains both tropical and warm temperate seagrass species and a warmer ocean will select for the tropical species.

Carbon dioxide concentrations: Dan Alongi from the Australian Institute of Marine Science (AIMS) presented some 'hot off the machine' measurements of the partial pressure of dissolved carbon dioxide (pCO2) that were taken aboard the AIMS research vessel R/V Cape Ferguson, which was recently outfitted with an underway sampling unit. There were inshore - offshore gradients in pCO2, with higher concentrations inshore. Dan was also able to detect depressions in pCO2 associated with an algal bloom. This underway sampling will, over time, accumulate a good map of pCO2 in the waters of the Great Barrier Reef.

Eva Abal, Emily Saeck, Anthony Kung, Heath Kelsey, Cath Collier and Bill Dennison (left to right) following climate change resilience index workshop.

This diversity of indicators was quite refreshing. There is some good science using state-of-the-art techniques like bioinformatics, molecular biology, autonomous vehicles, image recognition software, and mass spectrometry. Taken as a whole, this science of resilience is a fresh new approach on coral reef dynamics which I found stimulating.

About the author

Bill Dennison

Dr. Bill Dennison is a Professor of Marine Science and Vice President for Science Application at the University of Maryland Center for Environmental Science (UMCES). Dr. Dennison’s primary mission within UMCES is to coordinate the Integration and Application Network.

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