It’s not all about temperature for corals

31 05 2017


Three of the coral species studied by Muir (2): (a) Acropora pichoni: Pohnpei Island, Pacific Ocean — deep-water species/IUCN ‘Near threatened’; (b) Acropora divaricate: Maldives, Indian ocean — mid-water species/IUCN ‘Near threatened’; and (c) Acropora gemmifera: Orpheus Island, Australia — shallow-water species/IUCN ‘Least Concern’. The IUCN states that the 3 species are vulnerable to climate change (acidification, temperature extremes) and demographic booms of the invading predator, the crown-of-thorns starfish Acanthaster planci. Photos courtesy of Paul Muir.

Global warming of the atmosphere and the oceans is modifying the distribution of many plants and animals. However, marine species are bound to face non-thermal barriers that might preclude their dispersal over wide stretches of the sea. Sunlight is one of those invisible obstacles for corals from the Indian and Pacific Oceans.

If we were offered a sumptuous job overseas, our professional success in an unknown place could be limited by factors like cultural or linguistic differences that have nothing to do with our work experience or expertise. If we translate this situation into biodiversity terms, one of the best-documented effects of global warming is the gradual dispersal of species tracking their native temperatures from the tropics to the poles (1). However, as dispersal progresses, many species encounter environmental barriers that are not physical (e.g., a high mountain or a wide river), and whose magnitude could be unrelated to ambient temperatures. Such invisible obstacles can prevent the establishment of pioneer populations away from the source.

Corals are ideal organisms to study this phenomenon because their life cycle is tightly geared to multiple environmental drivers (see ReefBase: Global Information System for Coral Reefs). Indeed, the growth of a coral’s exoskeleton relies on symbiotic zooxanthellae (see video and presentation), a kind of microscopic algae (Dinoflagellata) whose photosynthetic activity is regulated by sea temperature, photoperiod and dissolved calcium in the form of aragonite, among other factors.

Read the rest of this entry »

Western Australia’s moronic shark cull

4 07 2014

another stupid politicianA major media release today coordinated by Jessica Meeuwig in Western Australia makes the (obvious) point that there’s no biological justification to cull sharks.

301 Australian and International Scientists experts have today provided their submission to the Western Australia Environmental Protection Authority (EPA), rejecting the scientific grounds for the proposed three-year drum-line programme.

Coordinating scientist, Professor Jessica Meeuwig from the University of Western Australia said:

“To have over 300 researchers, including some of the world’s top shark specialists and marine ecologists, all strongly agreeing that there is no scientific basis for the lethal drum-line programme, tells you how unjustified the government’s proposal is. If the EPA and the Federal Minister for the Environment are using science for decisions, the drum-line proposal should not be approved.”

The experts agree that the proposal presents no evidence that the lethal drum-line programme, as implemented, will improve ocean safety. It ignores evidence from other hook-based programs in Hawaii and Queensland that have been shown to be ineffective in reducing shark attacks on humans.

Dr. Christopher Neff from the University of Sydney stated:

“There is no evidence that drum lines reduce shark bites. The Western Australia EPA now faces a question of science versus politics with global implications because it is considering establishing a new international norm that would allow for the killing of protected white sharks.”

The drum lines are ineffective and indiscriminate, with 78% of the sharks captured not considered ‘threatening’ to humans. Yet, scientifically supported, non-lethal alternatives such as the South African ‘Shark Spotter’ and Brazil’s ‘Tag and Remove’ programmes are not adequately assessed as viable options for Western Australia. Read the rest of this entry »

Biodiversity needs more than just unwanted leftovers

28 02 2014

calm oceanThe real measure of conservation progress, on land or in the sea, is how much biodiversity we save from threatening processes.

A new paper co-authored by Memorial University’s Dr Rodolphe Devillers and an international group of researchers argues that established global marine protected areas are too often a case of all show with no substance and do not adequately protect the most vulnerable areas of the world’s oceans.

“There is a big pressure internationally to expand global MPA coverage from around 3 % of the oceans to 10 %, resulting in a race from countries to protect large and often unused portions of their territorial waters for a minimal political cost,” said Mr. Devillers. “Marine protected areas are the cornerstone of marine conservation, but we are asking whether picking low-hanging fruit really makes a difference in the long-term, or if smaller areas currently under threat should be protected before, or at the same time as, those larger areas that are relatively inaccessible and therefore less used by people.

“We need to stop measuring conservation success in terms of square kilometres,” he added. “The real measure of conservation progress, on land or in the sea, is how much biodiversity we save from threatening processes. Metrics such as square kilometres or percentages of jurisdictions are notoriously unreliable in telling us about the true purpose of protected areas.” Read the rest of this entry »

Where are they? Finding (and conserving) the biggest fish in the sea

16 11 2011

A post from my PhD student, Ana Sequeira, on her latest paper just out in Diversity and DistributionsOcean-scale prediction of whale shark distribution.

© W Osborn (AIMS)

The ocean is our major source of water, it stabilises our breathable atmosphere and provides many supplies such as medicines (e.g., anti-cancer therapy drugs1) and food. Despite its the importance for human life, many marine species are now at a high risk of extinction owing to human changes to the oceans.

The whale shark (Rhincodon typus, Smith 1828) – an icon of the oceans of a spectacularly huge size and docile character – is just one of those species.

Despite being a fish that many people (mainly in Southeast Asia) are happy to have on their plate, whale sharks are worth millions of dollars every year in the ecotourism industry worldwide. One would then expect that being such a profitable species, their ecology would be well known and thoroughly studied.

The reality is quite different.

Basic information on whale sharks such as the whereabouts of their breeding areas, the average number of offspring per female, or even how many individuals still exist, is not currently known. Moreover, despite the genetic evidence that whale sharks worldwide are connected among different oceans, it is unclear if they move from places where they are protected to places where they are still illegally fished.

Information on distribution and patterns of occurrence in space and time is essential for conservation, and can help to save entire ecosystems if used correctly, for example: to isolate important mating and breeding areas.

To identify the whale shark’s seasonal distribution patterns in the Indian Ocean, to test if records follow a decreasing trend over time, and if occurrence is related to variation in climatic signals, we used multivariate distribution models of seasonal and inter-annual whale shark sightings opportunistically collected over 17 years by the tuna purse-seine fishery. Read the rest of this entry »

Follow the TREND

24 10 2011

A little clichéd, I know, but that’s what it says on the T-shirt.

It’s been an interesting week. Not only did I return to some much-needed field work (even if it was diving in the muck of Adelaide’s Outer Harbour with 40-cm visability), but it was also the week when the TREND project became ‘official’ with the launching of its website and its public début at the Earth Station festival in Belair National Park over the weekend.

I can see the thought bubbles already – what the hell is ‘TREND‘ (apart from the obvious)?

Admittedly a somewhat contrived acronym, TREND stands for TRends in ENvironmental monitoring and Decision making – a multi-million dollar project financed mainly by the state government of South Australia and the Terrestrial Ecosystem Research Network (TERN – I know, another bloody acronym that is weirdly similar to TREND; oh how we Aussies love our acronyms and initialisms!). Here’s the official summary:

“TREND provides a system of data collection across native ecosystems, primary production regions and marine environments. By assessing the impacts of various potential climatic and environmental shifts, TREND will provide an early warning system for changes in South Australia’s diverse environments and a lasting legacy of long-term monitoring, informed policy and proactive response to environmental change. Read the rest of this entry »

Rise of the phycologists

22 09 2011

Dead man's fingers (Codium fragile) - © CJA Bradshaw

I’ve had an interesting week. First, it’s been about 6 years since I was last in Japan, and I love coming here; the food is exquisite, the people are fantastic (polite, happy, accommodating), everything works (trains, buses, etc.) and most importantly, it has an almost incredible proportion of its native forests intact.

But it wasn’t for forests that I travelled to Japan (nor the sumo currently showing on the guest-room telly where I’m staying – love the sumo): I was here for a calcareous macroalgae workshop.


First, what are ‘macroalgae’, and why are some ‘calcareous’? And why should anyone in their right mind care?

Good questions. Answers: 1. Seaweeds; 2. Many incorporate calcium carbonate into their structures as added structural support; 3. Read on.

Now, I’m no phycologist (seaweed scientist), but I’m fascinated by this particular taxon. I’ve written a few posts about their vital ecological roles (see here and here), but let me regale you with some other important facts about these amazing species.

Some Japanese macroalgae - © CJA Bradshaw

There are about 12,000 known species of macroalgae described by phycologists, but as I’ve learnt this week, this is obviously a vast underestimate. For most taxa that people are investigating now using molecular techniques, the genetic diversity is so high and so geographically structured that there are obviously a huge number of ‘cryptic’ species within our current taxonomic divisions. This could mean that we’re out by up to a factor of 2 in the number of species in the world.

Another amazing fact – about 50 % of all known seaweed species are found in just two countries – Japan and Australia (hence the workshop between Japanese and Australian phycologists). Southern Australia in particular is an endemism hotspot.

Ok. Cool. So far so good. But so what? Read the rest of this entry »

Susceptibility of sharks, rays and chimaeras to global extinction

10 11 2009
tiger shark

© R. Harcourt

Quite some time ago my colleague and (now former) postdoctoral fellow, Iain Field, and I sat down to examine in gory detail the extent of the threat to global populations of sharks, rays and chimaeras (chondrichthyans). I don’t think we quite realised the mammoth task we had set ourselves. Several years and nearly a hundred pages later, we have finally achieved our goal.

Introducing the new paper in Advances in Marine Biology entitled Susceptibility of sharks, rays and chimaeras to global extinction by Iain Field, Mark Meekan, Rik Buckworth and Corey Bradshaw.

The paper covers the following topics:

  • Chondrichthyan Life Historyangel shark
  • Niche breadth
  • Age and growth
  • Reproduction and survival
  • Past and Present Threats
  • Fishing
  • Beach meshing
  • Habitat loss
  • Pollution and non-indigenous species
  • Chondrichthyan Extinction Risk
  • Drivers of threat risk in chondrichthyans and teleosts
  • Global distribution of threatened chondrichthyan taxa
  • Ecological, life history and human-relationship attributes
  • Threat risk analysis
  • Relative threat risk of chondrichthyans and teleosts
  • Implications of Chondrichthyan Species Loss on Ecosystem Structure, Function and Stability
  • Ecosystem roles of predators
  • Predator loss in the marine realm
  • Ecosystem roles of chondrichthyans
  • Synthesis and Knowledge Gaps
  • Role of fisheries in future chondrichthyan extinctions
  • Climate change
  • Extinction synergies
  • Research needs

common skateAs mentioned, quite a long analysis of the state of sharks worldwide. Bottom line? Well, as most of you might already know sharks aren’t doing too well worldwide, with around 52 % listed on the IUCN’s Red List of Threatened Species. This compares interestingly to bony fishes (teleosts) that, although having only 8 % of all species Red-Listed, are generally in higher-threat Red List categories. We found that body size (positively) and geographic range (negatively) correlated with threat risk in both groups, but Red-Listed bony fishes were still more likely to be categorised as threatened after controlling for these effects.

blue sharkIn some ways this sort of goes against the notion that sharks are inherently more extinction-prone than other fish – a common motherhood statement seen at the beginning of almost all papers dealing with shark threats. What it does say though is that because sharks are on average larger and less fecund than your average fish, they tend to bounce back from declines more slowly, so they are more susceptible to rapid environmental change than your average fish. Guess what? We’re changing the environment pretty rapidly.

We also determined the spatial distribution of threat, and found that Red-Listed species are clustered mainly in (1) south-eastern South America; (2) western Europe and the Mediterranean; (3) western Africa; (4) South China Sea and South East Asia and (5) south-eastern Australia.

shark market, Indonesia

© W. White

Now, what are the implications for the loss of these species? As I’ve blogged recently, the reduction in predators in general can be a bad thing for ecosystems, and sharks are probably some of the best examples of ecosystem structural engineers we know (i.e., eating herbivores; ‘controlling’ prey densities, etc.). So, we should be worried when sharks start to disappear. One thing we also discovered is that we still have a rudimentary understanding of how climate change will affect sharks, the ways in which they structure ecosystems, and how they respond to coastal development. Suffice it to say though that generally speaking, things are not rosy if you’re a shark.

We end off with a recommendation we’ve been promoting elsewhere – we should be managing populations using the minimum viable population (MVP) size concept. Making sure that there are a lot of large, well-connected populations around will be the best insurance against extinction.

CJA Bradshaw

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ResearchBlogging.orgI.C. Field, M.G. Meekan, R.C. Buckworth, & C.J.A. Bradshaw (2009). Susceptibility of Sharks, Rays and Chimaeras to Global Extinction Advances in Marine Biology, 56, 275-363 : 10.1016/S0065-2881(09)56004-X