This is a little late in posting, but here is a video from a few weeks ago on Australia’s Channel 7 national news interviewing Alicia Crawley, a PhD student from my lab on the impacts of CO2 and ocean acidification on photosynthesis in corals. In a nutshell, Alicia’s research indicates that under higher CO2 scenarios, the symbiotic algae in corals are unable to protect themselves from the high light levels found on coral reefs, leading to starvation of the coral itself (click here to read the full journal article in Global Change Biology, “The effect of ocean acidification on symbiont photorespiration and productivity in Acropora formosa”). Click here for a transcript of a radio interview on ABC national news interviewing Alicia and a host of Australian marine scientists on the very real impacts of ocean acidification.

Great effort Alicia!

http://vimeo.com/moogaloop.swf?clip_id=7461976&server=vimeo.com&show_title=1&show_byline=1&show_portrait=0&color=00ADEF&fullscreen=1

In the second part of a series of videos and lectures on coral reefs and climate change (Online Reefs) is Dr Roberto Iglesias Prieto. Roberto is a lead research scientist at the Unidad Academia Puerto Morelos in Mexico, who has a long and distinguished career investigating the symbiont responses to coral stress. Roberto is a charismatic and captivating speaker, and his presentation is well worth watching for both scientists and anyone with an interest in coral reefs. Click here to see the first seminar in the series (Online Reefs (Part I): Climate change and ‘Survival of the Fittest’ among coral-algal symbiosis) by Todd LaJeunesse.

http://vimeo.com/moogaloop.swf?clip_id=7462072&server=vimeo.com&show_title=1&show_byline=1&show_portrait=0&color=00ADEF&fullscreen=1

I must admit I hadn’t thought of this one -apparently the Zoological Society of London is proposing the world’s first ‘cryobank’ for corals (similar to the Millenium Seed Bank project). According to news reports, the proposal is to preserve samples of coral in liquid nitrogen, allowing them to be ‘reintroduced’ at some point in the future:

”Well it’s the last ditch effort to save biodiversity from the reefs which are extremely diverse systems,” said Simon Harding from the Zoological Society of London (ZSL).

“It would take other work to try and reconstruct the reef so that you can start the process of building up a reef again,” he said.

“That is something that needs to be looked at in detail, but we can definitely store the species and save them in that way.” (Read More)

Interesting proposal, but whilst others might see this as a ‘necassary option’, it fails to get to the root cause of the issue: climate change.

Charlie Veron, former chief scientist of the Australian Institute of Marine Science, said he supported the effort but warned it was no consolation for the eradication of reefs.

Creating coral-style aquariums, similar to the zoos of today, or preserving the genetic make-up of coral samples to “resurrect” reef systems in the future, were not meaningful options, according to Dr Veron.

“These are not solutions,” he said. “Because Australia is home to the biggest coral reef in the world, it should concentrate all its efforts into helping the Great Barrier Reef survive.

“Personally, I feel it’s no compensation to know that the genetic information of corals is kept in machines.” (Read More)

UBC climate scientist Simon Donner published a gloomy paper a few months ago in PLoS One titled “Coping with Commitment: Projected Thermal Stress on Coral Reefs under Different Future Scenarios” link to the paper

The paper is the most sophisticated analysis to date of how climate change will increase the frequency of mass coral bleaching.  It is a step forward from Ove’s pioneering work on the same topic in his classic paper “Climate Change, coral bleaching and the future of the world’s coral reefs” (see two of the key figures from Ove’s review below).  In it, Ove reviewed the history and mechanisms of coral bleaching and made predictions about how the frequency of bleaching will increase as the oceans warm and high temperature anomalies become more and more frequent.

Simon took the next step by modeling the future frequency of bleaching under different IPCC scenarios (Fig 4 below). The depressing thing is how little difference there is among them, including between the very optimistic B1 scenario and the pessimistic (if more realistic in my view) A1b scenario.  [ I find the naming and assumptions of these scenarios somewhat confusing and I plan to post a guide to them in the near future.  For now consult the wikipedia article about them here or look at the draft notes I made based on that article below].

Methodology/Principal Findings/Conclusions: This study uses observed sea surface temperatures and the results of global climate model forced with five different future emissions scenarios to evaluate the “committed warming” for coral reefs worldwide. The results show that the physical warming commitment from current accumulation of greenhouse gases in the atmosphere could cause over half of the world’s coral reefs to experience harmfully frequent (p≥0.2 year−1) thermal stress by 2080. An additional “societal” warming commitment, caused by the time required to shift from a business-as-usual emissions trajectory to a 550 ppm CO2 stabilization trajectory, may cause over 80% of the world’s coral reefs to experience harmfully frequent events by 2030. Thermal adaptation of 1.5°C would delay the thermal stress forecast by 50–80 years…Without any thermal adaptation, atmospheric CO2 concentrations may need to be stabilized below current levels to avoid the degradation of coral reef ecosystems from frequent thermal stress events.

Donner used existing SST anomaly forecasts (coupled atmosphere-ocean CGMs) to model the future frequency of bleaching under different IPCC emissions scenarios (Fig 4 below).  SST anomalies and the probability of coral bleaching were estimated in each of 1687 0.5° x 0.5° grid cells.  Coral reef scientists use “Degree Heating Months” (DHMs), among other metrics, as an indication of accumulated thermal stress experienced by a coral colony or population. The metric is based on both magnitude and duration of a temperature anomaly. See the NOAA tutorial on the related Degree Heating Weeks metric here and on coral bleaching thresholds here. DHWs are measured and reported in real time by the NOAA Coral Reef Watch Program.  These bleaching thresholds are based on the well-documented fact that tropical corals are highly sensitive to anomalously high temperatures and live within ~ 1° C of their upper thermal tolerance.

DHW figure from the SW Pacific from the NOAA coral reef watch program.

Satellites only measure the temperature of the “skin” of the ocean, yet provide a surprisingly good estimate of the temperature of the bottom, where the corals are, at least in shallow depths, i.e., < 8 m. For example, we compared satellite-based SST measurements with data from temperature loggers on the ocean floor on nine reefs on the GBR and found a good match, with R² values ranging from 0.90 to 0.96 (Selig et al. 2006 – if you are interested, this paper can be download here).

The results are presented in terms of probabilities or frequencies of DHM values in excess of the upper bleaching threshold. GCMs are best suited to describe the evolution of the statistical properties of the climate system over time (e.g. bleaching events per decade), rather than the specific state of the climate at a particular moment in the future (e.g., bleaching event occurs on Jan 31, 2036). Therefore, studies of the effect of climate change on discrete events like mass coral bleaching or heat waves typically translate the time series of occurrences of the events into a time series of frequencies or probabilities.

Figure 4. Frequency distribution of the year in which the probability of severe mass bleaching events (DHM≥2°C-month) exceeds 20% for each the 1687 coral reef cells.

Figure 4 basically suggests that reefs are doomed, at least if any of the currently realistic scenarios come to pass.  But in a sense, that isn’t really news – people have been arguing for years that regulatory frameworks like Kyoto are not nearly enough and just a starting point.  The reality is that we need to quickly reverse CO2 accumulation and stay well below > 500 ppm.  (Or as Ove suggests in a recent post, get back to 350 ppm).

But one neat thing Simon did in his paper is compare the projected effects on bleaching frequency of different scenarios with and without a modest degree (1.5 C) of adaptation.  The differences between A1b and B1 are striking:

Figure 6. Frequency distribution of the year in which the probability of severe mass bleaching events (DHM≥2°C-month) exceeds 20% for each the 1687 coral reef cells.

With adaptation (which in this case includes acclimation, natural selection, shifts in species composition and local management actions) there is very little bleaching, at least in this century, under B1.  Is this a realistic degree of adaptation?  Maybe.  But this is being debated pretty intensively in the coral reef world.

Another question is how realistic the model assumption of coral recovery five years after a mass bleaching event is.  I think this is pretty optimistic.  But as Simon points out, that doesn’t affect the value of the scenario comparisons.

Billy Causey is the Southeast Regional Director for the National Marine Sanctuary Program of the National Oceanic and Atmospheric Administration.

Billy managed National Marine Sanctuaries in the Florida Keys since 1983, when he became the Manager of the Looe Key National Marine Sanctuary. As the manager of this marine protected area he developed the education, science and enforcement programs and sustained an interagency partnership between the state and federal governments. He served as the Superintendent of the 2900 square nautical mile Florida Keys National Marine Sanctuary from August 1991 to September 2, 2006, when he assumed his current position. Billy has been the lead National Oceanic and Atmospheric Administration (NOAA) official in the development of the management plan for the Keys Sanctuary, including development of this nation’s first comprehensive marine zoning plan. He led efforts to establish the largest network of fully protected areas in the continental US.

In the interview below from the Yale Forum on Climate Change, Billy discusses the impacts of climate change on reefs in the Fl Keys and elsewhere.

[youtube=http://www.youtube.com/watch?v=ifX2nCU625E&w=560&h=340]

Also see the article in the Yale Forum on the new US Federal research program (or at least plans for one) on ocean acidification, by Mark Schrope, a freelance science writer who frequently covers coral reefs, global change and related environmental issues.  Mark also wrote another recent article for the Yale Forum on reefs here.