Tag Archives: Coral Reefs

What the GBRMPA chair DID NOT say about my coral bleaching article

In April 2016 I submitted an article to The Marine Professional – a publication of the Institute of Marine Engineering, Science & Technology (IMarEST) focusing on the mass bleaching event that had hit the Great Barrier Reef at the time.  In their September 2016 issue, The Marine Professional featured a comment from a reader, in which he stated that he shared the article with Dr. Russell Reichelt – chair of the Great Barrier Reef Marine Park Authority.  The reader alleged that  Dr Reichlet told him that the article “contains some accurate things mixed with half truths and alarmism”.

A number of  coral reef, marine biology, and climate scientists have been in touch to express their concern about Dr Reichelt’s alleged comments on my article.  After liaising with Dr Reichelt’s office*, I am pleased to be able to set the record straight on what he did – or rather did not say.

*I did contact Dr Reichelt directly, but he replied via his office not directly.

After corresponding with Dr Reichelt’s office to determine where the “half truths and alarmism” were in the article, I have been informed that, whilst Dr Reichelt recalls the article being brought to his attention, he never made any such comments about the article.  In fact, he hadn’t even seen the article to comment on in the first place.  He has since read the piece and agrees that it is factual.

I have not attempted to contact the reader to find outwhere his comment came from.

Below is a copy of the article I submitted to The Marine Professional.   For those who want to see the article after it has been through their editorial process, please see the June 2016 edition of The Marine Professional.

Continue reading What the GBRMPA chair DID NOT say about my coral bleaching article

Just keep swimming

This little critter is a limpet.  From the photo they may not look like the most exciting of creatures.  If you’ve ever been down to the coast and taken a look at them yourself… your opinion may not have changed.  They don’t seem to move around a lot, or do a lot.  Of course looks can be deceiving.  Under that shell is the limpet’s squishy body – and their big, muscular foot which, alongside a pretty amazing adhesive secretion, they use to cling onto rocks and other hard surfaces.  Anyone who has ever had a go at trying to get a limpet off a rock knows how good a grip they can have.  This fabulous foot isn’t just used to stop them from drying out when the tide leaves them exposed to the air, or keep pesky predators (or nosy humans) at bay.  Limpets are grazers, feeding on tiny algae on the surface of rocks with their raspy “tongue” (called a radula).  See that empty space behind the limpet in the photo?  That’s where it’s been grazing.  Once they have grazed an area they need to find more food.  That foot gets to work, and along moves the limpet, munching up all the algae in its path.  Some limpet species even appear to have a home – a particular crevice that they return to just before the tide will expose them to the air.

But this isn’t a post about how amazing limpets are.  This is a post about animal movements in the ocean.. Or at least 3 different types of animal movement.  Some of them move a lot further than you think.  Yes, even limpets.

Continue reading Just keep swimming

No fishing zones for conservation look good on paper, but the reality can be very different

The global implementation of no-take zones, areas in which fishing (both commercial and recreational) is banned, has been a slow process despite scientific recommendations that they are a valuable tool for conservation – and even support fisheries.  The thinking behind no-take zones is simple.  Prevent extraction from a population and that population will increase over time.  There is plenty of evidence showing that no-take zones have higher fish abundance, biomass, and species richness than comparable fished areas, and that the fish inside no-take zones are larger too.  But there is a catch… designating an area ‘no-take’ is, in itself, not enough to ensure protection.  There are all sorts of factors that can influence the ‘success’ of no-take zones, such as placing the area where it they most needed, reducing pollution from external sources, and the level of compliance and/or enforcement.  After all, if people keep fishing inside the no-take zone, it doesn’t really meet the criteria of being no-take.  Inevitably a fished zone will fail to meet expected successes of a no-take. Continue reading No fishing zones for conservation look good on paper, but the reality can be very different

Climate Change Impacts on Kenya’s Fishery-dependent communities

 We now have a number of scientific studies that tell us how climate change is altering coral reef ecosystems, but how will these changes impact on communities that depend on them for their livelihood?  According to Joshua Cinner of James Cook University in Australia and colleagues from around the world, that answer depends more on the  community capacity for adaptation than its location.

Fishery-dependent communities in Kenya are not in a great situation.  Their reefs were heavily affected by a massive bleaching event in 1998 that has been linked to an extreme El Niño event and have not necessarily recovered as well as we might hope, and Kenyan reefs are likely to face increasing amounts of climate-related stress into the future.  Across three years, Cinner and co surveyed 15 ecological sites associated with 10 coastal communities along the Kenyan coast.  Using a range of ecological indicators of vulnerability of these reefs, they linked up the ‘health’ of the ecosystems with the vulnerability of the human communities that depend on them. Continue reading Climate Change Impacts on Kenya’s Fishery-dependent communities

Shark fishing, bleaching, & cyclones….

Over the years shark fishing – and particularly the practice of finning* – has garnered increasing attention from the public.  It seems that these predatory fish that were once feared and even hated are slowly being seen in a better light, the impetus for their conservation beginning to make ground.  Many shark populations have – and still continue to – experience high levels of overfishing.  The problem with overfishing top predators is that they tend to be slow-growing, long-lived, and don’t produce lots of offspring to allow populations to rebuild quickly.  Their removal can also cause what is known as a tropic cascade – when the removal of predators results in their prey becoming more abundant, which means that the critters they eat become less abundant….and so forth.  However, removal of top predators isn’t the only possible cause for changes in marine ecosystems.  There are a whole host of human stressors that can impact on the marine environment, and there are also natural stressors.  Take coral reefs for example we may add too many nutrients to the water, causing an increase in algae which can dominate corals, we may overfish a whole host of other coral reef species to name a few.  But these reefs may also be impacted by storm damage, flooding, and even ‘natural bleaching’, causing alterations in the benthic habitat (the reef itself).  If we want to understand how overfishing of sharks on reefs has altered the coral ecosystem, we need to do our best to take these other stressors into account.

About 300 km off the northwest coast of Australia lay two groups of uninhabited atoll-like coral reefs – the Rowley Shoals and Scott Reefs.  Scott reef has been, and continues to be, a top location for Indonesian fishers for centuries – including reef sharks.  Rowley Shoals on the other hand lies in what is now a marine protected area, and compliance is thought to be pretty good there, giving us a now unfished reef system.  Using long-term datasets,   Jonathan Ruppert from  the University of Toronto in Canada and fellow researchers took the opportunity to understand the effects of shark fishing, bleaching, and cyclones on changes in fish and habitat on these two reef systems.  As with many field-based studies, they could not pin down any definitive ‘cause and effect’, but they did uncover a number of interesting correlations.

The abundance of corallivores (coral eating) and planktivores (plankton eating) fish species appeared to decline in line with loss of live coral (this is called negatively correlated).  For these critters, their abundance didn’t significantly differ between the fished and unfished reefs.  It seemed that they are more affected by changes in habitat as a result of the natural disturbances then the abundance of sharks.  This makes a sense – they have just lost their food source and shelter.  Herbivorous fish – like parrotfish – on the other hand seemed to fair much better after a these natural disturbance.  When a cyclone or bleaching destroys coral, algae can (but not always) increase in its place.  This is because algae grow much quicker than the corals, resulting in an increase in food for the herbivores.  This is likely the reason why herbivores showed a positive correlation (an increasing trend) with increasing algal cover.  But there were also less herbivores on fished reefs compared to unfished reefs.  The loss of these guys is a particular problem because herbivores are vital for keeping algae in check to stop it completely dominating a coral reef.  If you lose herbivores, you can lose much if not all of a coral reef.  Given that bleaching and cyclones are thought to increase in frequency and intensity as our climate is changes, the role of herbivores may become even more important to reef survival.

As we move up the food chain, we reach the mesopredators – the mid-level predators, which on coral reefs means families like snapper and emperors.  The abundance of these critters didn’t show any significant relationship with benthic habitat, but were much more abundant on fished reefs than unfished reefs.  In a nutshell, the less sharks the more mesopredators, and the less herbivores.  Sounds like a trophic cascade?  Perhaps, but the authors are also quick to note that these differences on fished and unfished reefs could be down to other reasons – remember, their study found relationships (correlations) – not cause and effect.  For example, the authors found some differences in the habitat between the Rowley Shoals and Scott Reefs that they could cause the differences in the fish communities between the two systems.  They also note that variation in larval supply may be a significant factor in the differences seen.

Despite these issues, and the lack of definitive ‘the loss of sharks has directly caused x’, the authors suggest we don’t sit back on our laurels.  We may not be able to make any appreciable difference to the frequency and intensity of bleaching or cyclone events in the short-term, we can reduce the pressure on sharks.  For a marine ecosystem that is widely regarded as at risk on a global scale, it may be that every little bit helps.

The paper is published in the open access journal  PLoS ONE – you can have a read of it here dx.doi.org/10.1371/journal.pone.0074648

Image:  Black tip reef shark (Carcharhinus melanopterus).  Credit Jim H./Flickr (CC BY-SA 2.0)

To find out more about the Black tip reef shark, head over here.
*Shark finning is the practice of removing a sharks fin whilst on board a fishing boat, and then throwing the remainder of the shark back into the sea.  See this excellent blog entry by David Shiffman  on what shark finning actually is.

In the face of changing coral reefs, how will dependent communities react?

We now have a number of scientific studies that tell us how climate change is altering coral reef ecosystems, but how will these changes impact on communities that depend on them for their livelihood?  According to Joshua Cinner of James Cook University in Australia and colleagues from around the world, that answer depends more on the  community capacity for adaptation than its location.

Fishery-dependent communities in Kenya are not in a great situation.  Their reefs were heavily impacted by a massive bleaching event in 1998 that has been linked to an extreme El Nino event and have not necessarily recovered as well as we might hope, and Kenyan reefs are likely to face increasing amounts of climate-related stress into the future.  Across three years, Cinner and co surveyed 15 ecological sites associated with 10 coastal communities along the Kenyan coast.  Using a range of ecological indicators of vulnerability of these reefs, they linked up the ‘health’ of the ecosystems with the vulnerability of the human communities that depend on them.

The authors found only a marginal difference in the vulnerability of reefs that were heavily fished, under community co-managed fisheries closures, or no-take National Marine Parks, with heavily fished reefs looking like they may be most vulnerable.  How this impacted on their associated human-communities varied considerably, with some communities faring better than others.  Some of this variability depended on the type of species fishers were targeting, with fishers using traps and beach seine nets are expected to see a decline in their catch.  But we are an adaptable species, and some coral creatures – particularly herbivorous fish – may increase in abundance as a response to changes in the reef*.

But not every community is able to adapt to the changing conditions well.  There are a whole host of reasons why a community may not be able to adapt.  For the fishers themselves, switching gear to catch a different species isn’t necessarily that easy.  Fishing equipment isn’t cheap, and these guys aren’t exactly rolling in it.  Then we have whole communities that are almost solely dependent on reef fisheries.  For these guys, their adaptive capacity is even more limited, because there simply isn’t the option to switch to another source of livelihood.  In essence, communities that are more ‘generalist’ are better able to adapt to changing conditions than those which are ‘specialist’.

So where does this leave the Kenyan communities when having to deal with the changing conditions they are facing?  The authors maintain that “adaptive capacity is perhaps the component of vulnerability most amenable to influence, and may be a useful focus for adaptation planning”.  This is a good point.  We can’t necessarily halt the degradation that reefs have been experiencing on a time-scale that is meaningful to these communities, but we can work towards supporting communities increase their capacity to adapt to change.

Lumping ‘poor communities’ together when thinking about climate change impacts doesn’t really cut it – even within the same geographic area there is considerable variation with regards to the impacts of climate change and more importantly how those communities can respond to that change.

The paper is published in the open access journal PLoS ONE

Image: Small-scale fishers on the coral reef surrounding Siquijor island, Philippines.  Credit Rebecca Weeks/Marine Photobank

* Herbivorous fish may increase because algae often grow over dead coral.  So, as reefs become degraded and the coral dies off, there will be more food for herbivorous fish and we may very well see a shift in the state of the ecosystem in those areas.  Nothing is certain though, and we will have to wait to see how that scenario actually plays out.

Pacific Islanders to face climate change challenges

Ahh the Pacific Islands…white sand, warm water, sun shining down….it sounds wonderful (especially for me – I’m having a ‘year of winter’ with my moving about).

But things are changing, and perhaps nothing is quite changing on a global scale quite like the climate.  If your a Pacific Islander, climate change is likely to be a huge problem.  It all comes down to reliance on local resources, and in many cases these resources come from local marine waters.  From a food perspective, Dr Johann Bell of the Secretariat of the Pacific Community and colleagues from around the globe predict things are going to change a fair bit….here’s some highlights from the paper: Continue reading Pacific Islanders to face climate change challenges

Social-ecological vulnerability of coral reef fisheries to climatic shocks

Just as climate change is altering reef-associated species behaviour, ecology , and community structure below the water, so it too is impacting those on land.  That includes people.  The FAO have taken a look at the socio-ecological impacts of climate climate change and ocean acidification on a human community in Kenya that utilizes reefs for their livelihoods and survival.

Here’s the blurb from the FAO:

“This [FAO] circular examines the vulnerability of coral reef social-ecological communities to one effect of climate change, coral bleaching. The objective was to develop and test in Kenya a community-level vulnerability assessment approach that incorporated both ecological and socio-economic dimensions of vulnerability in order to target and guide interventions to reduce vulnerability.

In addition to a range of direct threats such as siltation, overfishing and coral disease, coral reefs are now threatened by climate change. Climate impacts on coral reefs and associated fisheries include:
increasing seawater temperatures;

  • changes in water chemistry (acidification);
  • changes in seasonality;
  • increased severity and frequency of storms, which affect coral reef ecosystems as well as fisheries activities and infrastructure.

Coral bleaching and associated coral mortality as a result of high seawater temperatures is one of the most striking impacts of climate change that has been observed to date. As warming trends continue, the frequency and severity of bleaching episodes are predicted to increase with potentially fundamental impacts on the world’s coral reefs and on the fisheries and livelihoods that depend on them.

The analysis presented in this circular combined ecological vulnerability (social exposure), social sensitivity and social adaptive capacity into an index of social-ecological vulnerability to coral bleaching. All three components of vulnerability varied across the sites and contributed to the variation in social-ecological vulnerability. Comparison over time showed that adaptive capacity and sensitivity indices increased from 2008 until 2012 owing to increases in community infrastructure and availability of credit. Disaggregated analysis of how adaptive capacity and sensitivity varied between different segments of society identified the young, migrants and those who do not participate in decision-making as having both higher sensitivity and lower adaptive capacity and, hence, as being the most vulnerable to changes in the productivity of reef fisheries.”

The full report is open access.

Image: Toka Panda spear fishes for reef fish, Santupaele village, Western Province, Solomon Islands. Taken by Filip Milovac.  WorldFish/Flickr (CC BY-NC-ND 2.0)