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.

What?

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





Sleuthing the Chinese green slime monster

21 10 2009

greenslimemonsterI just returned from a week-long scientific mission in China sponsored by the Australian Academy of Science, the Australian Academy of Technological Sciences and Engineering and the Chinese Academy of Sciences. I was invited to attend a special symposium on Marine and Deltaic Systems where research synergies between Australian and Chinese scientists were to be explored. The respective academies really rolled out the red carpet for the 30 or so Australian scientists on board, so I feel very honoured to have been invited.

During our marine workshop, one of my Chinese counterparts, Dongyan Liu from the Yantai Institute for Coastal Zone Research, presented a brilliant piece of ecological sleuthing that I must share with readers of ConservationBytes.com.

The first time you go to China the thing that strikes you is that everything is big – big population, big cities, big buildings, big projects, big budgets and big, big, big environmental problems. After many years of overt environmental destruction in the name of development, the Chinese government (aided by some very capable scientists) is now starting to address the sins of the past.

Liu and colleagues published their work earlier this year in Marine Pollution Bulletin in a paper entitled World’s largest macroalgal bloom caused by expansion of seaweed aquaculture in China, which describes a bloody massive outbreak of a particularly nasty ‘green tide’.

What’s a ‘green tide’? In late June 2008 in the coastal city of Qingdao not far from Beijing (and just before the 2008 Olympics), a whopping 1 million tonnes of green muck washed up along approximately 400 km2 of coastline. It took 10,000 volunteers 2 weeks to clean up the mess. At the time, many blamed the rising eutrophication of coastal China as the root cause, and a lot of people got their arse kicked over it. However, the reality was that it wasn’t so simple.

The Yellow Sea abutting this part of the Chinese coast is so named because of its relatively high productivity. Warm waters combined with good mixing mean that there are plenty of essential nutrients for green things to grow. So, adding thousands of tonnes of fertilisers from Chinese agricultural run-off seems like a logical explanation for the bloom.

Qingdoa green tide 2008 © Elsevier

Qingdao green tide 2008 © Elsevier

However, it turns out that the bulk of the green slime was comprised of a species called Enteromorpha prolifera, and it just so happens that this particularly unsavoury seaweed loves to grow on the infrastructure used for the aquaculture of nori (a.k.a. amanori or zicai) seaweed (mainly, Porphyra yezoensis). Problem is, P. yezoensis is grown mainly on the coast hundreds of kilometres to the south.

Liu and colleagues examined both satellite imagery and detailed oceanographic data from the period prior to the green tide and not only spotted green splotches many kilometres long, they also determined that the current flow and wind direction placed the trajectory of any green slime mats straight for Qingdao.

So, how does it happen? Biofouling by E. prolifera on P. yezoensis aquaculture frames is dealt with mainly by manual cleaning and then dumping the unwanted muck on the tidal flats. When the tide comes back in, it washes many thousands of kilos of this stuff back out to sea, which then accumulates in rafts and continues to grow in the warm, rich seas. Subsequent genetic work also confirmed that the muck at sea was the same stock as the stuff growing on the aquaculture frames.

Apart from some lovely sleuthing work, the implications are pretty important from a biodiversity perspective. Massive eutrophication coupled with aquaculture that inadvertently spawns a particularly nasty biofouling species is a good recipe for oxygen depletion in areas where the eventual slime monster starts to decay. This can lead to so-called ‘dead’ zones that can kill off huge numbers of marine species. So, the proper management of aquaculture in the hungry Goliath that is China becomes essential to reduce the incidence of dead zones.

Fortunately, it looks like Liu and colleagues’ work is being taken seriously by the Chinese government who is now contemplating financial support for aquaculturists to clean their infrastructure properly without dumping the sludge to sea. A simple policy shift could save a lot of species, a lot of money, and a lot of embarrassment (not to mention prevent a lot of bad smells).

CJA Bradshaw

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This post was chosen as an Editor's Selection for ResearchBlogging.org

ResearchBlogging.orgLiu, D., Keesing, J., Xing, Q., & Shi, P. (2009). World’s largest macroalgal bloom caused by expansion of seaweed aquaculture in China Marine Pollution Bulletin, 58 (6), 888-895 DOI: 10.1016/j.marpolbul.2009.01.013





Eastern Seaboard Climate Change Initiative

30 04 2009
© A. Perkins
© A. Perkins

I’ve just spent the last few days in Sydney attending a workshop on the Eastern Seaboard Climate Change Initiative which is trying to come to grips with assessing the rising impact of climate change in the marine environment (both from biodiversity and coastal geomorphology perspectives).

Often these sorts of get-togethers end up doing little more than identifying what we don’t know, but in this case, the ESCCI (love that acronym) participants identified some very good and necessary ways forward in terms of marine research. Being a biologist, and given this is a conservation blog, I’ll focus here on the biological aspects I found interesting.

The first part of the workshop was devoted to kelp. Kelp? Why is this important?

As it turns out, kelp forests (e.g., species such as Ecklonia, Macrocystis, Durvillaea and Phyllospora) are possibly THE most important habitat-forming group of species in temperate Australia (corals and calcareous macroalgae being more important in the tropics). Without kelp, there are a whole host of species (invertebrates and fish) that cannot persist. The Australian marine environment is worth something in the vicinity of $26.8 billion to our economy each year, so it’s pretty important we maintain our major habitats. Unfortunately, kelp is starting to disappear around the country, with southern contractions of Durvillaea, Ecklonia and Hormosira on the east coast linked to the increasing southward penetration of the East Australia Current (i.e., the big current that brings warm tropical water south from Queensland to NSW, Victoria and now, Tasmania). Pollution around the country at major urban centres is also causing the loss or degradation of Phyllospora and Ecklonia (e.g., see recent paper by Connell et al. in Marine Ecology Progress Series). There is even some evidence that disease causing bleaching in some species is exacerbated by rising temperatures.

Some of the key kelp research recommendations coming out of the workshop were:

  1. Estimating the value of kelp to Australians (direct harvesting; fishing; diving)
  2. Physical drivers of change: understanding how variation in the East Australian Current (temperature, nutrients) affects kelp distribution; understanding how urban and agricultural run-off (nutrients, pollutants, sedimentation) affects distribution and health; understanding how major storm events (e.g., East Coast Lows and El Niño-Southern Oscillation) affects long-term persistence
  3. Monitoring: what is the distribution and physical limits of kelp species?; how do we detect declines in ‘health’?; what is the associated biodiversity in kelp forests?
  4. Experimental: manipulations of temperature/nutrients/pathogens in the lab and in situ to determine sensitivities; sensitivity of different life stages; latitudinal transplants to determine localised adaption
  5. Adaptation (management): reseeding; managing run-off; managing fisheries to maintain a good balance of grazers and predators; inform marine protected area zoning; understanding trophic cascades

The second part of the discussion centred on ocean acidification and increasing CO2 content in the marine environment. As you might know, increasing atmospheric CO2 is taken up partially by ocean water, which lowers the availability of carbonate and increases the concentration of hydrogen ions (thus lowering pH or ‘acidifying’). It’s a pretty worrying trend – we’ve seen a drop in pH already, with conservative predictions of another 0.3 pH drop by the end of this century (equating to a doubling of hydrogen ions in the water). What does all this mean for marine biodiversity? Well, many species will simply not be able to maintain carbonate shells (e.g., coccolithophore phytoplankton, corals, echinoderms, etc.), many will suffer reproductive failure through physiological stress and embryological malfunction, and still many more will be physiologically stressed via hypercapnia (overdose of CO2, the waste product of animal respiration).

Many good studies have come out in the last few years demonstrating the sensitivity of certain species to reductions in pH (some simultaneous with increases in temperature), but some big gaps remain in our understanding of what higher CO2 content in the marine environment will mean for biota. Some of the key research questions in this area identified were therefore:

  1. What is the adaptation (evolutionary) potential of sensitive species? Will many (any) be able to evolve higher resistance quickly enough?
  2. In situ experiments outside the lab that mimic pH and pCO2 variation in space and time are needed to expose species to more realistic conditions.
  3. What are the population consequences (e.g., change in extinction risk) of higher individual susceptibility?
  4. Which species are most at risk, and what does this mean for ecosystem function (e.g., trophic cascades)?

As you can imagine, the conversation was complex, varied and stimulating. I thank the people at the Sydney Institute of Marine Science for hosting the fascinating discussion and I sincerely hope that even a fraction of the research identified gets realised. We need to know how our marine systems will respond – the possibilities are indeed frightening. Ignorance will leave us ill-prepared.

CJA Bradshaw

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