Tag Archives: Resilience

Coral almost as genetically complex as humans’

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corals

CNN News, May 29th 2009:

Advances in the study of coral in the last few years has led a group of scientists to conclude that corals almost rival humans in their genetic complexity and their relationship to algae is key to their survival.

“We’ve known for some time the general functioning of corals and the problems they are facing from climate change,” said Virginia Weis, a professor of zoology at Oregon State University and an author of a report published in the journal Science.

“But until just recently, much less has been known about their fundamental biology, genome structure and internal communication. Only when we really understand how their physiology works will we know if they can adapt to climate changes, or ways that we might help.”

The study found that corals have sophisticated systems of biological communication that are being stressed by global change. Disruptions to these communication systems, particularly between coral and the algae that live within their bodies are the underlying cause of the coral bleaching and collapse of coral reef ecosystems around the world, say the report’s authors. (Read the full story at CNN News)

Caribbean fish decline in the wake of coral collapse?

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A new study in Current Biology (some really interesting coral related stuff being published there lately) by Michelle Paddack and colleagues (Paddack et al 2009) documents a region-wide decline in reef associated fish in the Caribbean. The authors conducted a meta-analysis on a substantial amount of fisheries-independent, time-series data on Caribbean fish densities. Fish densities seem to have been pretty stable from the mid-50s until the mid-90s, to then exhibit significant negative rates of change during the past 10 years. What is striking is the generality of the decline that has occured the past decade, across the whole region (see figure below)

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Recorded declines in fish densities across five Caribbean sub-regions 1996-2007

Differences in fished and non-fished species were non-significant. This leads the authors to speculate that fishing is not the main driver of these changes (although certainly it plays a part). Rather, as has been documented in the western Indian Ocean, these changes in fish communities could be a response to the substantial losses of coral cover which have occurred in the Caribbean the past decades. A wicked problem, primarily for managers and communities dependent on fisheries, is that changes in fish communities seem to manifest themselves as a form of “degradation debt” – that is, there is a substantial time-lag between changes in the underlying benthic community and the response of fish communities.

Resilient ‘super reefs’ a priority for conservation efforts

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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.

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Parrotfish in Swedish fishmarkets

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Svenska Dagbladet, Swedens second largest daily newspaper, recently ran a story on the appearance of parrotfish in Swedish fishmarkets. Parrotfish can be likened to lawnmowers of the reef, and keep algae from smothering coral reefs.

Parrotfish sold for 269 SEK/kg at a Swedish fishmarket. Photo courtesy of Jerker Lokrantz/Azote

Parrotfish sold for 269 SEK/kg at a Swedish fishmarket. Photo courtesy of Jerker Lokrantz/Azote

Parrotfish are not known to be an essential part of the Scandinavian kitchen, so one wonders what they are doing being flown halfway across the world to a country that has enough tasty seafood to satisfy its needs? When contacted by reporters store managers claimed that distributors would recomend parrotfish as a colourful species that would certainly attract buyers. They also explained that they did have policies regarding the sale of red-listed species, but that parrotfish do not appear on any such lists (WWF and IUCN). This is problematic, as models and observation suggest that the levels of parrotfish biomass required to safeguard reefs against algal domination, are probably much higher than those that would classify them as being red-listed.

And this doesn’t seem to be a one-off incident. Two PhD-students from Stockholm University, Jerker Lokrantz and Matilda Thyresson, are currently following up reports of large (several tons) shipments of parrotfish from Vietnam arriving to Sweden via the Netherlands. This whole story really illustrates the challenges facing marine resource management in the face of rapid exploitation driven by a globalized market, as highlighted by Berkes et al in the 2006 Science article “Globalization, Roving Bandits, and Marine Resources“.

Using the internet as an early warning of ecological change

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A recent paper out in Frontiers in Ecology and the Environment  (Galaz et al 2009) identifies novel and fascinating ways on how to capture looming ecological crises.

The basic problem addressed by the authors is this: The six billion people on Earth are changing the biosphere at unprecedented rates. Ecosystems tend to respond to such change in unpredictable ways; collapsing fisheries and sudden phase shifts observed in freshwater ecosystems and coral reefs are good examples of such phenomena. The challenge is that existing ecological monitoring systems are not in tune with the speed of social, economical and ecological change and early warnings of pending ecological crisis are to a large extent limited by insufficient data, and geographical gaps in official monitoring systems.

So how do we deal with this situation? Look to the internet for guidance! Not quite so simple, but the researchers from the Stockholm Resilience Centre and the University of east Anglia, explore the possibilities of using information posted on the Internet to detect ecosystems on the brink of change.

Much of the pioneering work in this type of Internet surveillance has come in the public health field, where software programs that search the Internet in methodical and automated manners, web crawlers, are used to track disease.

The potential of web crawlers is illustrated by the success of the Global Public Health Intelligence Network (GPHIN), an early disease detection system developed by Health Canada for the World Health Organization (WHO). GPHIN gathers information about unusual disease events by monitoring internet-based global media sources, such as news wires, web sites, local online newspapers, and public health e-mail information services, in eight languages, with non-English articles filtered through a translation engine. The system retrieves approximately 2000–3000 news items per day; roughly 30% are rejected as duplicative or irrelevant, but the remainder are sorted by GPHIN analysts and posted on GPHIN’s secure website.  

Web crawlers could be designed to complement conventional ecological monitoring. The authors use coral reef ecosystems to illustrate how such a process could progress. Data-mining the internet for information on potential drivers of coral ecosystem change (e.g. heavy investment in fish gear that can precede heavy exploitation of key reef organisms) and ecosystem responses (changes in coral cover, fish community composition) can be the basis for early warning assessments of ecological change.

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Fig. 1 Examples of drivers and impact signals regarding a coral reef social-ecological system, that in principle could be detected by a web-crawler

Addtionally, by searching the internet for reports of local scale coral reef degradation can provide early indicators of large scale systemic collapses of reef systems. The success of such web-crawlers will be highly dependent on information becoming rapidly accessible online via”web 2.o” applications such as blogs, wikis and other networking tools such as electronic mailing lists (Coral-List is highlighted as an example).

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Fig. 2 Ecological shifts at smaller scales can provide warnings of impending changes to large-scale systems

I guess that a problem, and one highlighted by the authors, is that fragmented and insufficient data from several sources, could lead to information junkyards instead of robust ecological monitoring systems. Any web crawler based monitoring system would therefore need to be plugged into a coupled knowledge management and expert judgement system. Would that slow the process down to the extent of nullyfying any gains made through the rapid information sweeps generated by the web crawler?  In any case, its a refreshing approach and a fascinating read.

“Macro-algal dominated coral reefs: shake that ASS”

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In recent years, coral reefs have been hit hard by an array of anthropogenic impacts – coral bleaching, coral disease, overfishing and eutrophication to mention but a few – resulting in significant declines in coral cover and species diversity. One of the classic examples of coral reef decline was discussed by Terry Hughes in a 1994 article in the journal Nature, entitled “Catastrophes, Phase Shifts and Large-Scale Degradation of a Caribbean Coral Reef”. Hughes concluded that the synergistic impacts of overfishing, hurricane damage and disease resulted in a ‘phase shift’ from a coral dominated ecosystem (52% coral cover, 4% algal cover) to a macro-algal dominated ecosystem (2% coral cover, 92% algal cover). Similar examples of phase-shifts from coral to macroalgal dominated ecosystems have been observed across the Caribbean region, throughout the Eastern-Pacific, Indian Ocean and on the Great Barrier Reef.

asdasdWhilst macro-algal dominated reefs and phase shifts have recieved considerable attention in the scientific literature, a recent paper questions the role and driving factors of such ‘alternative stable states’ (ASS), and implicates the dominance of several other organisms that take rise following the loss of coral cover.

First establishing that a ‘phase shift’ must result from a decline of coral and subsequent increases in an other ‘alternative’ organism that must last for a significant period of time (in this case >5yrs), Norström et al conducted a survey of the literature to determine exactly what alternative organisms were dominant on reefs following a phase shift.

The authors argue a timely point that phase shifts associated with coral reefs are not exclusively coral – macroalgal shifts, and often result in shifts to ‘other’ states, including ‘soft coral’  dominance (corallimorphs and octocorals), sponges and urchin dominated states.

One of the key findings of the research suggests that whilst these different alternative states are common, the factors driving the shift may be considerably different. Whilst macro-algal states are driven by ‘top down’ factors (a loss of herbivorous fish or urchins through overfishing or disease), soft coral and sponge states are more closely associated with ‘bottom up’ factors (declining water quality).

Site specific examples of phase shifts in coral reefs: a) Israel, b) Seychelles, c) Belize

Site specific examples of phase shifts and the persistence of alternative stable states in coral reefs: a) Israel, b) Seychelles, c) Belize

So what does it take to ‘shake that ASS’? (Alternative Stable State, of course). Once a coral reef has shifted to an alternative stable state, simply removing the stressor that triggered the shift might not be sufficient to produce recovery back to a coral dominated state – partly due to feedback mechanisms, or a longer-term decline in environmental conditions.

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Coral springs back from tsunami

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Coral transplantation in Indonesia after the impact of the boxing day 2004 tsunami.

Coral transplantation in Indonesia after the impact of the boxing day 2004 tsunami.

BBC News, 26th December

Scientists have reported a rapid recovery in some of the coral reefs that were damaged by the Indian Ocean tsunami four years ago.

It had been feared that some of the reefs off the coast of Indonesia could take a decade to recover.

The New York-based Wildlife Conservation Society (WCS) found evidence of rapid growth of young corals in badly-hit areas. A spokesman said reefs damaged before the tsunami were also recovering. Some communities were abandoning destructive fishing techniques and even transplanting corals into damaged areas, the WCS said.

“This is a great story of ecosystem resilience and recovery,” said Stuart Campbell, co-ordinator of the WCS’s Indonesia Marine Program.

“These findings provide new insights into coral recovery processes that can help us manage coral reefs in the face of climate change.”

Ove Hoegh-Guldberg, a reef expert from the University of Queensland in Australia who did not take part in the study, said the findings were not surprising since corals typically recovered if not affected by fishing and coastal development.

“We are seeing similar things around the southern Great Barrier Reef where reefs that experience major catastrophe can bounce back quite quickly,” the scientist told the Associated Press.

Countries across the Indian Ocean have been remembering the 2004 disaster, which claimed some 230,000 lives. Prayers were said in Indonesia, Thailand and India on Friday, while Sri Lanka declared a two-minute silence in memory of the dead.

MPAs and climate change II: study finds no-take reserves do not increase reef resilience

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PI Nick Graham surveying a high coral cover reef.

PI Nick Graham surveying a high coral cover reef.

Some coral reefs scientists have argued (and prayed) that marine reserves (no-take MPAs) could limit the impacts of climate change on populations of reef-building corals.  The idea is that by maintaining healthy food webs and herbivore populations, reef managers can prevent seaweed blooms that can kill juvenile corals.  Restricting fishing would thus increase reef resilience (which ecologists define as the return rate of an ecological system to its baseline state following a disturbance).  Unfortunately, a new study tempers such wishful thinking.

The study (Graham et al. 2008 published on August 27 in the open access journal PloS One) indicates that marine reserves have no effect on coral resilience to ocean warming.

Approximately 45% of coral cover in the Indian Ocean was lost in 1998 due to temperature-related coral bleaching.  To compare coral loss within and outside of reserves, the team resurveyed 66 reefs in the Indian Ocean that had originally been surveyed before the 1998 mass bleaching event.  The surveyed sites included reefs within nine reserves in four countries.

The results indicated that “A greater proportion of [marine reserves] (71%) than fished (42%) locations showed significant declines in coral cover over the study period. There was no evidence to suggest the percent change in coral cover differed between [marine reserves] and fished areas, and in some cases declines were significantly greater in [marine reserves]”

This is an important study in coral reef ecology.  As a believer in Macroecology and a long-time disciple of James Brown (the desert ecologist, not the King of Funk) I think such a regional-scale, carefully implemented approach could be used to answer many other key questions in reef ecology.  Having read hundreds of monitoring studies while building a database of >10,000 reef surveys, I can attest that there are few targeted macroecological reef studies of this scope.  There are some monitoring programs this large.  But few studies of this scale are designed and implemented to answer a specific question.  Although the macroecological approach is rarely employed (due to obvious financial and logistical constraints), it certainly isn’t new.  Terry Hughes (Hughes 1994 Science) applied it by resurveying nine reefs on the north coast of Jamaica after a variety of disturbances wiped out corals and enabled macroalgae to become the dominant benthic organism.  Even earlier, Endean and Stablum surveyed dozens of reefs across the GBR in the late 1960s and early 1970s to assess the impact of and recovery from a regional crown-of-thorns starfish outbreak.

I imagine critics of Graham et al. 2008 and it’s implications could argue that many or most tropical marine reserves are not well-managed and that they might increase resilience if enforced.  This would be a fair point, but given the political and socio-economic realities of the region, poaching might be difficult or impossible to eliminate.  So to paraphrase Donald Rumsfeld, we might just have to conserve reefs with the marine reserves we have, not the marine reserves we want.

Change in coral cover at sites across the western Indian Ocean

Change in coral cover at sites across the western Indian Ocean. Green and red symbols represent increases and decreases in coral cover respectively. Symbols with solid borders are sites in marine reserves. Data represent 66 sites across the region. Numbers in key (size of bubble) are percent changes between mid 1990s and 2005.