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Monday
May102010

Play Bit-o-critter, round 15

The second to last one stumped you all, while Akira got the last one in about 2 seconds.  Lets hope this one is in the middle somewhere.  This has enough detail for a scientific name, but a common name for the species will do.

Monday
May102010

Mountains of Pelagic Diversity

ResearchBlogging.org

If you ever saw the dramatic seamount scene in Blue Planet (and if you haven’t, where ya been??), then you are probably familiar with the idea that submarine mountains can attract lots of animals; as Attenborough puts it, they “create oases where life can flourish in the comparatively empty expanses of the open ocean”.  In that spectacular BBC sequence, jacks and tuna swarm an Eastern Pacific seamount peppered with colourful schools of barberfish, Anthias and goatfish.  Then the sharks cruise in, including silkys and hammerheads, there for a clean from the faithful barberfish.
There’s a paper in the latest issue of PNAS that quantifies the richness of seamounts, so beautifully depicted by those geniuses at the BBC Documentary department.  The authors, led by Telmo Morato from the Secretariat of the Pacific Community in New Caledonia, analysed data gathered by longline fisheries in the western and central Pacific, close to and remote from seamounts .  In a sense, a longline is a standardized sort of sampling unit like a quadrat, so they can be analysed across locations to measure differences in diversity.  They accounted for differences between total catch per longline using the statistical process called rarefaction which is a practical application of one of my favourite fundamental biological patterns – the species accumulation curve - which I’ve discussed before (here and here).  It looks like a great dataset with great spatial resolution and pretty good coverage in the tropics, though the equatorial zones are less well-represented.
I don’t think anyone would be surprised by their result that, yes, seamounts are diverse places.  When they broke it down by species, about 2/5 (15 species) showed positive association with seamounts; this group included both sharks and fish.  Interestingly, 3 species (pelagic stingrays, albacore and shortbilled spearfish) showed negative associations with seamounts, while 19 showed no measurable association.  So, the net effect is positive, but there's clearly some structure in the data, depending on what species you look at.  Nor, I think , would most people be surprised by the distance effect they found, wherein sample diversity decreased with distance moved away from the peak of a seamount, and most sharply in the first 10 or so kilometers.  What was surprising, to me at least, was that both the absolute diversity and the distance effect they found were greater on seamounts (left) than they were for coastal zones (center). 
I would have thought that coastal zones, with their larger area, more complex topography and currents, coastal upwelling and inputs from the land, should have had higher diversity.  Indeed, it kind of goes against the island biogeography ideas, that as we go away from the largest habitat towards smaller more distant patches, diversity drops; if you think of seamounts as underwater islands and continental shelves as underwater mainlands, perhaps you’ll see what I mean.
There’s a couple of reasons I can think of to explain the observed difference.  Perhaps there is something intrinsic to seamounts, some feature of topography or productivity that makes them real magnets for diversity.  Under this scenario, they are true biodiversity hotspots.  Alternatively, perhaps coastal zones once were more diverse than seamounts but have been denuded by our actions, so that only the remote and submarine mountains remain as examples of what once was.  Perhaps it’s a bit of both, or some other concept (that you should propose in the comments).  Either way, Morato et al. show us that we may be successful at protecting widely roaming pelagic species by strategically preserving relatively tiny specks of submarine oases.  Since reading their paper, I have enjoyed thinking of schools of pelagics, hopping from mountaintop to mountaintop, skipping across vast plains of abyssal ocean, and as usual dreaming about diversity and all the fantastic forms of life in the 3D wonderland of the open ocean.  It just makes you want to down tools and grab the next slow boat bound for Cocos, doesn't it?

Morato, T., Hoyle, S., Allain, V., & Nicol, S. (2010). Seamounts are hotspots of pelagic biodiversity in the open ocean Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.0910290107

Sunday
May092010

Oill spills and Tar balls – know thine enemy

One of the more intriguing aspects of oil spills, including the DeepWater Horizon spill currently unfolding in the Gulf of Mexico (DeepSeaNews has covered it well), is the formation of tar balls.  These are globby blobs of bitumen-like material that are found on the sea floor or washed up on beaches after a spill. There's a few theories about how they form, but the general concept is that as the more volatile parts of the oil mixture evapourate, the mixture becomes thicker, heavier and stickier, until eventually the blob becomes heavier than seawater and sinks. On the bottom, the sticky blob incorporates sediment and its ball-like shape is reinforced by the rolling actions of currents or surf, in much the same way as you roll cookie dough into balls before putting them on the baking tray (mmmmmm….cookies….ahem). Sometimes this process makes for a grainy crust on the outside and a soft center, a bit like a Ferrero Rocher (mmmmm....chocolate....why do my analogies always involve food?).  There’s some other theories of formation that concern flocculation (oil sticking to clay) and emulsion (oil and water making a mousse of sorts - again with the food), but the prevailing idea seems to be that of smaller blobs of weathered oil coalescing and incorporating sediment. The net results is a gooey mess that is characteristically hard to remove if it sticks to you (or an animal), pongs of petroleum and is generally unpleasant.  The photo at left from NOAA's image library shows a tarball on a beach in California

Other than their B-grade horror movie nature (The Blob – aiieeeeee!) and the formation process above, I confess not knowing much about tar balls, so I went to the literature to see what’s out there. The answer: not much. A Web of Science search for “(tar ball) or tarball” 1945-2010 gets you precisely 26 hits. Now that is interesting! I would have thought that there would be far more, given the attention that is focused on oil spills when they happen. Much of the research has focused on chemical fingerprinting to identify where a given tar ball originated. In other words, the presence and absence of certain chemicals in a tar ball can tell you what sort of oil the ball formed from, and pretty accurately too. This has allowed some other studies that have shown that you have to be careful about blaming all the tar balls on a beach on one spill; there’s often a pretty good background level of tar balls from previous spills and even natural sources of oily substances. This is especially so for really small tar balls in the mm size range.

So what’s the long-term prognosis on tar balls in the environment? It doesn’t look like that question has been thoroughly answered yet.  Clearly they persist long after many more obvious signs of oil are gone.  Its tempting to think that they may be largely inert, especially those that form a good crust on the outside that reduces stickiness and prevents chemical interactions with the outside. But really, it seems like there’s a lot more work that needs to be done to understand these curious byproducts of oil spill accidents.

Friday
May072010

Play Bit-o-critter, round 14

Easy enough that I need the proper scientific name...

Thursday
May062010

Something eerie is happening, down Mexico way...

After a youth spent on the dry side of the water (another post for another day), I have come to love SCUBA diving with a passion. I also love art and photography projects that explore the way nature reclaims all things, in time. (My wife dubbed this obsession “elegant decay” – stuff that’s falling apart and looks good doing it.) Soon there’s going to be an opportunity to combine those passions in one of my favourite places – the Yucatan Peninsula of Mexico. Artist Jason de Caires Taylor is installing the largest underwater sculpture garden in the world, in the waters adjacent to Isla Mujeres, not too far from Cancun. I find this idea captivating. Normally the human world and the underwater world are so forcibly separated by medium, light and a host of other factors, and this project will bring them into eerie juxtaposition. The proposed 200 human figures reclining, working, or even riding a bicycle, contrasting with the reef, fishes and rippling filtered sunlight is just great. How do I know, if it hasn’t been built yet? Because he’s already done similar work on a much smaller scale in the Keys and Grenada.

Some might argue that this stuff is visual pollution of a reef that should just be appreciated for the biological wonder that it is, but I couldn’t disagree more. Especially when the reef begins to claim the sculptures as its own, in time incorporating their forms into its structure and adding its own patina of life, like a painter stepping back from the canvas and daubing the final blobs of color here and there. By then, we and the reef will be one and the same, and that idea really resonates with me. Installation begins in June. I can’t wait to see it when I am down in Mexico this summer.

What do you think – art or pollution?

Wednesday
May052010

The solution to Bit-o-critter round 13

Twas the torpedo ray, Torpedo panthera

Tuesday
May042010

Carnival of the Blue 36

Carnival of the Blue is a collection of marine science blog posts from all over the web, hosted every month at a different blogger's page.  This month its at Christie Wilcox's blog "Observations of a Nerd".  Check it out!

I'm on the docket to host CotB in December.  In the meantime, you can visit its perpetual home here, and marvel at the munificent magnanimity of its creators, Jason Robertshaw and Mark Powell.

Tuesday
May042010

A Parasite a Day, keeps the Doctor in pay

My colleague Susan Perkins at AMNH has a most excellent blog that features a different parasite every day for a year.  Since the oceans have more parasites than anywhere else by far, many of her feature critters are marine.  Check out some of these marine beasties, then enjoy the rest of the collection.  There's a new one every day.

Crepidostomum cooperi - a digenean (fluke) parasite of fish
Nasitrema globicephalae - a digenean parasite of the sinuses of whales
Cyamus ovalis - isopod parasites often called "whale lice"
Maritrema novaezealandensis - an important model digenean from New Zealand mudflat animals
Polypodium hydriforme - a weird parasitic jellyfish relative that lives on sturgeon eggs, and:
Dolops sp., -  a type of Branchiuran (related to crustaceans) parasitic on piranha

Monday
May032010

Solution to Bit-o-critter round 12

OK, at long last, here's the solution for Bit-o-Critter round 12, the 6 pack of butterflyfish:

A. Chaetodon plebeius - blue-spot butterfly


B - Chaetodon ornatissimus - ornate butterfly

C - Chaetodon meyeri - Meyer's butterfly

D - Chaetodon lunula - Raccoon butterfly

E - Chaetodon austriacus - Blacktail butterfly

F - Parachaetodon ocellatus - Kite or six-spined butterfly

Now get on over to Round 13 and help Julie figure out what it is...

Sunday
May022010

A whaling conundrum

With tip of the cap to jfang at The Great Beyond

A recent proposal to limit whaling has been rejected by Japan and Australia, for opposite reasons. Japan, which takes almost a thousand whales a year, mostly Minke, objects to the 400 annual quota, which steps down after 5 years to 200 for another 5 years. Australia, which has a long history of opposing whaling, says the proposal doesn't go far enough; they're basically looking for a zero tolerance whaling policy.

Honestly, much as I hate the idea of even a single whale dying in the name of the imaginary research that Japan uses to defend commercial whaling, I think the Aussies might be being a little hard nosed in this case. Lets say the proposal is rejected, then the Japanese continue to take a thousand whales a year - how is that better? The art of negotiation is compromise, and in my view its always better to accept steps in the right direction, even if you don't get everything you want. Its like selling a car: you advertise for 10 grand, hope for 9, expect 8 and accept 7. If you hold out for 10, you're going to be disappointed most of the time.  Obstinacy doesn't help the cause.

In his vision for whaling, Peter Garret (Australia's environment minister) states that the right solution is to restructure the International Whaling Commission.  That may be so, but in the 2 years that it might take to do that, you could have saved 1,200 whales if you accept the current proposal first, and then go after the recalcitrant nations through a restructured IWC with more teeth.

There's a key line in the Great Beyond post linked above, from IWC chair Cristian Maquieira: “I don't think anybody will be happy with the numbers."  I often recognise that as the sign of a successful negotitation: a good outcome is not when everyone is happy, but when everyone is equally unhappy.

Sunday
May022010

Post your eyewitness accounts of the Gulf oil spill here

I think we'd all love to hear from people who live on or near the gulf coast and may have observations or stories to tell about their experiences of the oil spill.

Sunday
May022010

Leaked government report about the Gulf oil spill

I haven't posted anything about the Gulf oil leak because others have covered it so well (see Dr. M.'s excellent timeline at DSN), but this story about a leaked coast guard report caught my eye

Concern is that the leak rate could get ten times worse; if the wellhead goes then the job of fixing it also gets an order of magnitude harder.  The story sounds as though this is a distinct possibility.  I don't know enough to judge, but it certainly sounds like bad ju-ju.

Thursday
Apr292010

Sardine recipes

I was recently told that I ought to try sardines, but I have no idea how to prepare them. Does anyone have ideas for canned sardines that I could try?

Wednesday
Apr282010

Tilting the three-way tango - disease as a loss of diversity

ResearchBlogging.orgDisease is a funny old thing.  We're taught from very early on that disease agents are "bad" and that, by contrast, the infected are somehow poor and unfortunate victims of nasty evil bugs.  This is clearly a cultural bias, wherein we project our own concerns about getting sick onto all other animals; there's no real reason to think that a bacterium or virus has any less right to be here or any less important role in the ecological processes of the world than does the dolphin it infects, or the fish or the lobster.  We have all survived eons while avoiding extinction, which makes us winners in the great game of evolution, the microbes every bit as much (or more) than their hosts.

Still, biases run deep.  This is important because sometimes they cloud our perceptions of whats really going on.  Consider coral diseases for a moment.  What, you didn't know that coals get diseases?  That's OK, neither did most folks, including many scientists, until fairly recently.  Lets picture a nice reef coral, maybe a handsome Porites, infected with one of the many "band"-causing agents (diseases that march across the surface of the coral, destroying tissue along a coloured front that gives the disease its name).  Most folks would perceive that the coral (good) was quietly minding its own business when it was "infected" by the microbe (bad), causing disease.  But actually it took at least three players to tango in this case; the coral had to be susceptible to the pathogen, the pathogen had to be infectious to the coral, and the environment had to set the scene that made the interaction swing in favour of the pathogen.  This simple "disease triad" is the most basic model of how infectious processes take place, but its just that: a basic model.

These days, disease studies are becoming a lot more nuanced, and its revealing a whole new world of how diseases start and stop.  Rocco Cipriano, a microbiologist colleague of mine at the National Fish Health Labs in Leetown WV, has been promoting a model lately where an infectious disease of fish (furunculosis) is caused by a disruption to the natural community of bacteria on the skin of fish; a community in which pathogens have no place normally.  The furunculosis agent (Aeromonas) is excluded from these communities by bacteria better adapted to living in normal fish skin and its associated mucus layer.  That is, until an environmental modulator, like a temperature spike or pollutant, shakes things up a bit; what ecologists would call disturbance.  And what is the first outcome of disturbance in most systems? Loss of diversity, in this case among the normal bacterial community.  Some bacteria disappear from the skin of the fish, freeing up resources (space, food) that are exploited by other bacteria - opportunists that can come in and pounce on the new space or food.  When that space and food consists of the fish itself, we call those bacteria pathogens.  This same process happens after any ecological disturbance, like a hurricane on a reef or a tree falling in a rainforest: opportunists come in and pounce on a newly-available resource; then as things settle down a succession takes place, until the early colonisers are displaced by more typical fauna.  In this view, disease is nothing more than a byproduct of disturbance and loss of diversity in the normal microbial community.

Which brings me back to corals and to the recent paper by Mao-Jones and colleagues in PLoS Biology.  These folks used a mathematical model to show that much the same holds true for the diseases of corals, which, like fish, rely heavily on a surface layer of mucus as their first line of defence.  It seems that in both corals and fish, the mucus is important, but even more important are the normal bacteria that live there, continually excluding pathogens and acting as a protective guard against disease.  In a very anthropomorphic sense, the corals (and fish) are using the surface bacteria as a biological weapon against the potential pathogens, at the expense of having to produce all that mucus for the bacteria to live and feed on.  Importantly, Mao-Jones and friends show us that the derangement of the mucus community can persist for a really long time after the initial disturbance.  This is important, because you often come along and see disease starting, but you may well have missed the initial insult that got the ball rolling, which may have occurred some time ago.

I really like this idea of infectious disease as an ecological disturbance and of many pathogens as simply early colonisers in the succession back towards health (or towards death, if the disturbance was too severe).  As a model, it doesn't work for everything, though.  There are many "primary pathogens" that are specifically adapted to invade healthy animals, but its not in the best interests of those organisms to invest so much energy in adaptations to invasion, only to kill the host, thus many of those are fairly benign.  For more "opportunistic" agents, however, I suspect it holds true much of the time, and that group includes many or most of the really virulent diseases.  I dare say many of the "emerging" diseases fall in this category, and we can expect to see more of this as the global climate continues to tilt the tango in favour of the pathogens.

Mao-Jones, J., Ritchie, K., Jones, L., & Ellner, S. (2010). How Microbial Community Composition Regulates Coral Disease Development PLoS Biology, 8 (3) DOI: 10.1371/journal.pbio.1000345