Published 01 April 2014
The latest IPCC report (working group II, AR5) released yesterday found with ‘high confidence’ that there will be ‘significant change in community composition and structure of coral reef systems in Australia…the ability of corals to adapt naturally to rising temperatures and acidification appears limited and insufficient to offset the detrimental effects’. These changes have been exacerbated by rising levels of atmospheric carbon dioxide (CO2). For a few days in May of last year, CO2 levels exceeded a crucial milestone of 400 parts per million (ppm). These conditions haven’t been seen for over 3 million years, since the last major climactic event that had significant repercussions for biodiversity worldwide. A few weeks ago, CO2 again reached above 400ppm, and for the first time is forecasted to remain at this level for the next few months. It’s important to understand where this data comes from, what it means for our reef and how microscopic organisms can help us.
The longest running monitoring program of atmospheric CO2 exists in Mauna Loa, Hawaii, where scientists have been monitoring daily changes in the atmosphere since March 1958. These data have formed one of the most convincing pieces of evidence of anthropogenic fossil fuel emission effects on the atmosphere, known as the Keeling Curve.
Within this increasing trend of CO2, there are natural fluctuations that occur in the atmosphere due to seasonal changes. The greater land mass in the northern hemisphere takes up more CO2 in the spring and summer months due to increased photosynthesis by terrestrial plants, causing an annual decrease in the June-August months.
Impact on the Great Barrier Reef
In 2009, a study published by the worlds leading coral reef experts highlighted the importance of keeping carbon emissions under 350ppm. The authors argued that this threshold allows for the preservation of biodiversity in marine ecosystems, whereas levels of >450ppm would lead to irreparable damage. Many organizations have echoed this benchmark, calling for decreases in carbon emissions worldwide.
In Australia, the Great Barrier Reef attracts upwards of A$6 billion a year in tourism, a figure that is nearly completely reliant on the health of the marine ecosystem. In addition, the Australasia chapter of the latest IPCC report points out that, ‘the net present value of the reef alone over the next 100 years has been estimated at A$51.4 billion’. Local issues, such as dredging at Abbott Point, have been discussed in a previous blog, but the reef is also facing global stressors from fossil fuel emissions such as ocean warming, acidification and sea level rise.
A readily observable effect of climate change has been a 30cm rise in sea level since pre-industrial times, with a forecast of another 70cm rise by the end of the century (IPCC 2014). While this sounds like a small increase, low-lying islands are already being affected, leading to beach erosion and loss of property. But as oceans are changing, how can we help solve these problems?
The Great Barrier Reef is threatened by climate change, but it is also producing organisms that could help to alleviate its impacts. One unique group of organisms that could aid in combatting changing climates are large benthic foraminifera (LBFs). These fascinating organisms are microscopic, single-celled and have calcium carbonate skeletons, similar to corals. Foraminifera come in an array of unique shapes, and are referred to in many Asian countries as “star sands,” due to their star shaped skeletons. LBFs live on the surface of algae and when they die their skeletons degrade, and add to beach sands. Although they are individually small, their large densities and fast reproductive rates mean that their ecosystem function drastically outweighs their individual size. In fact, some islands along the Great Barrier Reef, such as Green Island near Cairns, are reliant on the persistence of LBFs for the maintenance of beach sands. An innovative project initiated in Tuvalu is even attempting to determine optimal growing conditions for these organisms, to aid in sand production to potentially mitigate beach erosion caused by sea level rise.
Increasing CO2 emissions in the atmosphere are causing the earth to become an inadvertent experiment. Without understanding the key players and how they will respond it makes successful management of anthropogenic change nearly impossible. This means looking beyond the larger picture, in particular at microscopic organisms such as foraminifera, that have an exponentially greater environmental impact than their small size would suggest. It is vital that we find creative and innovate ways to mitigate the predicted negative impacts of climate change on our marine systems.
Steve Doo is a PhD candidate in the School of Biological Sciences at the University of Sydney. He focuses on Marine Biology and works on One Tree Island research station in the Great Barrier Reef.