Go check out these incredible photographs by National Geographic photographer Thomas Peschak of mantaray feeding frenzies in the Maldives. Apparently this swirling ‘cyclone‘ feeding behavior is rarely seen outside of the Maldives. Click here for a previous post on Climate Shifts for more details and video footage of Mantaray feeding behaviors.
The Algalita Marine Research Foundation is on a 2 month voyage across the Pacific to study the concentration of plastics in the North Subtropical Gyre. This area has been known as the “Pacific Garbage Patch” due to the convergence of several ocean currents that drag garbage from all corners of the globe. Not only is there large floating debris (bottle caps, toothbrushes, plastic bags, etc.) but half of the debris found is small chips of unidentifiable plastics.
Charles Moore, who discovered this garbage patch, found plastic flakes floating 10 meters below the surface like “snowflakes or fish food”. The more disturbing fact is the weight of plastic far outweighed the plankton in the water. Consequently there are increasing accumulations of plastic on beaches in the Pacific. UNEP estimates that plastic is killing a million sea birds and 100,000 marine mammals and turtles every year.
Chrisitana and Jeff each reeled in a mahi mahi today, one right after the other. The fish served a double purpose, science and sustenance. Before we filleted the fish, Christiana took muscle and liver samples of each of the fish and looked in their stomachs. Fish number 3, the mahi mahi that Jeff reeled in, contained what the Captain confirmed via microscope as none other than a piece of plastic film. This now makes 8 species of fish in which we have identified with plastic in their gut.
The paradigm of ‘coral vs algae’ has become entrenched in coral reef science over the last few decades. The classic example of this paradigm in the Caribbean was from a paper published byTerry Hughes in a 1994 article in the journal Nature, entitled “Catastrophes, Phase Shifts and Large-Scale Degradation of a Caribbean Coral Reef”. The paper documented a series of disturbances in the late 1970’s and early 1980’s, including two major hurricanes, a disease outbreak and the loss of a seaweed-grazing urchin, after which coral cover declined dramatically from ~70 percent cover to less than 10%, and macroalgal cover to rose to almost complete dominance >90% .
Since then, reefs throughout the Caribbean have undergone dramatic declines in coral cover, leading to the regionwide collapse of the two dominant reef building corals, Acropora cervicornis and Acropora palmata. One ‘good news’ story did come out from a neighbouring reef in Jamaica called ‘Dairy Bull’ reef, where Joshua Idjadi and a team reported a doubling of live coral cover over the last decade, resetting the balance from a macroalgal dominated reef to a coral reef.
Since this iconic case study, a considerable quantity of scientific literature has been devoted to management principles, herbivorous grazing pressure and the reversal of macro-algal dominated reefs. However, documented examples of regional ‘phase shifts’ between coral and algae in the literature are surprisingly few and far between (asides from a few notable exceptions). John Bruno & Elizabeth Selig, two coral reef researchers who have developed a considerable dataset on coral reefs throughout the world, decided to test this assumption by randomly samply for regional trends and patterns in algal cover – much the same as an epidimiologist would determine the generality of case reports in the medical literature.
John and his team trawled through an immense number of reef surveys (3,500 to be exact) from over 1,800 reefs across the globe between 1996 and 2006, and developed a ‘phase shift index’ based upon corals and macroalgae. They then tested this index in four geographic regions (Greater Caribbean, Florida Keys, Indo-Pacific and the Great Barrier Reef) to see if the severity of phase shifts altered over the decade between 1996 – 2006. Their findings were surprising, and might prove to be somewhat controversial…
Whilst phase shifts were indeed more common in the Caribbean than elsewhere, very few of the worlds reefs fell into either a stable ‘coral reef dominated’ or a ‘macroalgal dominated’ category. Furthermore, the ‘severity’ of phase shifts at a regional level was much less severe than the classic examples of macroalgal dominance, such as the Jamaican coral decline story. The data also suggested that there was no trend (>1995) towards macroalgal dominance in the Florida Keys or Indo-Pacific. Coral cover during this period (1996 – 2006) did decline (primarily due to crown of thorns starfish plagues), but their was no corresponding increase in macroalgal cover at all during this time.
Bruno et al argue that the apparent mismatch between the local scale descriptions of macroalgal dominance and regional scale patterns was caused by a gross generalisation of a relatively small number of ‘atypical’ case studies. This in itself is no small finding, and may go along way to altering the way we manage coral reefs. These findings may be somewhat controversial, it’s hard to disagree with the data. In what’s bound to throw the proverbial cat amongst the pigeons, the authors conclude:
“Since the Jamaica story was an anomaly, it makes a poor foundation for general models of reef ecology (e.g., Knowlton 1992, Bellwood et al. 2004 ). The current paradigm of reef management and ‘‘resilience’’ is based in large part on the perception that most of the world’s reefs are being overrun by seaweed (Szmant 2001, Precht and Aronson 2006, Knowlton 2008). This belief led to the argument that reef managers should focus primarily on conserving herbivores or water quality (Szmant 2002, Pandolﬁ et al. 2003, Bellwood et al. 2004 ). While these are clearly important objectives of management, our analysis suggests that the macroalgae problem has been exaggerated.
Overﬁshing and poor land use practices may trigger widespread coral to macroalgal phase shifts in the future, but to date, the principal form of coral reef degradation has been the loss of reef-building corals, with only limited and localized increases in macroalgae. Therefore, the primary goal for reef managers and policy makers should be the conservation of coral populations, without which the entire system would collapse.”
A recent study published by Tom Oliver and Stephen Palumbi from Stanford University in the journal ‘Marine Ecology Progress Series‘ seems to suggest yet another miraculous and novel mechanism by which corals will ‘escape’ the pressures of global warming. In a nutshell, the researchers found that corals from ‘warm pools’ at Ofu Island (American Samoa) hosted ‘heat tolerant’ types of symbiotic algae, whereas corals from cooler lagoons hosted more ‘heat sensitive’ types of algae. When combined with regional data, Oliver & Palumbi suggest that in regions where annual maximum temperatures reached 29 – 31C, coral ‘avoided bleaching’ by hosting higher proportions of ‘heat tolerant’ algal symbionts. Whilst these findings are interesting, the study is a long way from the suggestion in the paper and accompanying press release that coral reefs are ‘adapting’ and ‘may survive global warming’, and relies mainly on over interpreting their results. There are several issues at hand:
- Whilst these results highlight both the diversity of bleaching responses at a community level and the array of algal symbionts, the finding of heat tolerant corals has been shown throughout the Indo-Pacific and Great Barrier Reef on a number of previous occasions. The suggestion that this pattern results from a correlation in local scale heating based upon a limited sampling regime is far from proving causality
- The identification of a few remnant tough (‘heat resistant’) corals does not equate to these corals spreading out and maintaining coral reef ecosystems under rapid climate change. Such coral types are rare, and are likely to have minimal impacts in sustaining reef populations under future climate change scenarios. In making this argument, the authors are leaping across a myriad of issues that would need to be proven before we could pin our hopes on a few odd-ball corals for building and maintaining functional reef ecosystems into the future.
- Although corals have been shown to be able to ‘shuffle’ symbionts (change the proportion of ‘heat sensitive’ to ‘heat tolerant’ types), to date it has never been shown that corals can uptake ‘novel’ symbiont types from external sources. So, corals that are ‘heat sensitive’ can’t acquire ‘heat tolerant’ types from the environment. In light of rapid increases in sea surface temperatures under future climate scenarios, these ‘heat sensitive’ corals will undergo mass mortality, as they are unable to simply ‘adapt’ or switch to more resistant types.
- Any successful proliferation of these heat resistant genotypes will depend on a stabilised climate. Continual increases in temperatures means that these genotypes will have a harder time proliferating and stabilising, given that selection pressures will continue to intensify. This is akin to the bar in a high jump competition being placed ever higher. As time goes on, fewer and fewer ecotypes from the population will be able to pass beyond the barrier.
- The authors seem to imply that functional reef ecosystems (and countless ecosystem services) will be ‘saved’, based upon a specific niche of ‘heat resistant’ corals. The issue here is not the survival of corals species – many of whom will be resistant to extinction under global climate change (albeit as rare organisms) – but the destruction of functional coral reef ecosystems that millions of people depend on. Unfortunately, a few corals in a warm rock pool in Samoa will not save the day or the planet.
- These results do not address ocean acidification – the ‘other CO2’ issue along with temperature that threatens all calcifying organisms. To somehow imply that coral reefs are not facing problems from climate change because Oliver and Palumbi found a few tough coral genotypes in a rock pool, verges on the incredible.
These points aside, the study is an interesting one in terms of exploring heat stress in corals. My main issue is that Oliver & Palumbi have massively overextended their conclusions, which is particularly apparent in the associated press release. Needless to say, these sorts of overblown claims are less than useful in the lead-up to the critically important COP15 negotiations in Copenhagen at the end of year.
Update, 25th May
And here is a classic example of why such media releases are less than useful, courtesy of the detractor Andrew Bolt:
The megamouth shark (Megachasma pelagios) is one of the worlds rarest sharks – spotted only 43 times since its discovery back in 1976 off Oahu, Hawaii. These sharks are huge and bizzare creatures, capable of growing upwards of 5m in length, with luminescent light organs surrounding the mouth to attract plankton and small fish. So rare is the megamouth shark, that apparently scientists were surprised to find the 44th megamouth shark (caught by mackeral fishers in the Phillipines) had been cooked and eaten by local villagers before anyone could take a closer look. I wonder which part of the 500 kilogram shark was considered the delicacy? Read more at the National Geographic – thanks to Brian for the tip!
BBC News, 13th May 2009: The world’s most important coral region is in danger of being wiped out by the end of this century unless fast action is taken, says a new report.
The international conservation group WWF warns that 40% of reefs in the Coral Triangle have already been lost. The area is shared between Indonesia and five other south-east Asian nations and is thought to contain 75% of the world’s coral species. It is likened to the Amazon rainforest in terms of its biodiversity.
It’s 2099, and across south-east Asia, a hundred million people are on the march, looking for food. The fish they once relied on is gone. Communities are breaking down; economies destroyed. That is what we can expect, says the new WWF report, if the world’s richest coral reef is destroyed. And that, it says, could happen this century.
It’s billed as a worst-case scenario, but the report’s chief author, Professor Ove Hoegh-Guldberg, says it is not as bad as the future we’re currently headed towards.
“Up until now we haven’t realized how quickly this system is changing,” says Professtor Hoegh-Guldberg.
“In the last 40 years in the Coral Triangle, we’ve lost 40% of coral reefs and mangroves – and that’s probably an underestimate. We’ve fundamentally changed the way the planet works in terms of currents and this is only with a 0.7 degree change in terms of temperature.
“What’s going to happen when we exceed two or four or six?”
Avoiding a worst-case scenario would need significant reductions in greenhouse gas emissions and better controls on fishing and coastal areas, says the report. The Coral Triangle covers 1% of the earth’s surface but contains a third of all the world’s coral, and three-quarters of its coral reef species. If it goes, an entire eco-system goes with it – and that, says Prof Hoegh-Gudberg, has serious consequences for its ability to tackle climate change.
“Pollution, the inappropriate use of coastal areas, these are destroying the productivity of ocean which is plummeting right now. That is the system that traps CO2 – 40% of CO2 goes into the ocean.
“Now if we interrupt that, the problems on planet earth become even greater,” says Prof Hoegh-Gudberg.
Indonesia is hosting the World Ocean Conference this week because, it says, oceans have been neglected so far in global discussions on climate change.
It wants the issue to have a bigger profile at UN climate talks later this year.
ScienceDaily, 23rd April 2009
The Wildlife Conservation Society announced today a study showing that some coral reefs off East Africa are unusually resilient to climate change due to improved fisheries management and a combination of geophysical factors. WCS announced the results of the study at the International Coral Reef Initiative (ICRI), which is meeting this week in Phuket, Thailand.
The study, published in the online journal Aquatic Conservation: Marine and Freshwater Ecosystems, provides additional evidence that globally important “super reefs” exist in the triangle from Northern Madagascar across to northern Mozambique to southern Kenya and, thus, should be a high priority for future conservation action.
Authors of the study include Tim McClanahan and Nyawira Muthiga of the Wildlife Conservation Society, Joseph Maina of the Coral Reef Conservation Project, Albogast Kamukuru of the University of Dar es Salaam’s Department of Fisheries Science and Aquaculture, and Saleh A.S. Yahna of the University of Dar es Salaam’s Institute of Marine Sciences and Stockholm University’s Department of Zoology.
The study found that Tanzania’s corals recovered rapidly from the 1998 bleaching event that had wiped out up to 45 percent of the region’s corals. Along with monitoring Tanzania’s reefs, WCS helps coral conservation in this region through training of park staff in protected areas.
The authors attribute the recovery of Tanzania’s coral reefs due in part to direct management measures, including closures to commercial fishing. Areas with fishery closures contained an abundance of fish that feed on algae that can otherwise smother corals, while the few sites without any specific management measures remain degraded; one site had experienced a population explosion of sea urchins—pests that feeds on corals.
I remember seeing a fascinating presentation by Mahmood Riyaz on the reef slope failure of this coral reef at the ICRS conference in Florida last year – how the atoll rim was cracking due to the sheer amount of construction and concrete. Welcome to Male, the capital of the Maldives, where >100,000 people are crammed ontop of a coral reef atoll only 1.7km in length. The Maldives have been hit hard in recent years, collectively lost over 2/3 of it’s coral following the 1998 bleaching event. In addition, being such a low lying country is likely to be problematic given the projected sea level rises, so the Maldivian government is proposes a carbon neutral approach by 2020, and is even considering diverting some of the billion dollar tourism profits to purchase a new homeland. The photo above doesn’t do justice to the population density on such a tiny atoll – check the satellite images on google earth.
One of my PhD Students, Siham Afatta, has started a new science blog called ‘Laut & Kita’ (Sea & Us). Siham (a seasoned blogger) is targeting this as one of very few scientific blogs written in Bahasa (the official language of Indonesia), which focuses primarily on marine conservation in Indonesia. I think this is a great effort and great example of the power of blogging – check out the link below.