Monday, May 31, 2010

Take a Levy walk on the wild side

ResearchBlogging.orgI've mentioned before that this summer I’ll be part of some whale shark field work studies in Mexico. Some of it will focus on how these amazing animals find patches of their planktonic food in the ocean. There’s a pretty good likelihood that they have an incredibly sensitive sense of smell and can detect food from miles away. They’re a bit different than toothy sharks though, because they aren’t detecting “blood in the water” as such; rather, they need to be able to distinguish patches of ocean where plankton is denser from places where its less dense. How do they do that, and what chemicals are they smelling exactly? These are among the questions we will be trying to answer.

In reading up for this work, I came across the idea of Levy Walks. This is not a walk in the sense of your evening constitutional down to the Piggly Wiggly for a 6-pack and some Slim Jims. No, it really is just the name for a certain pattern of animal movement (shown at the right), one in which animals make several short “legs” of directed motion, usually in bunches, separated by longer legs with major reorientations. Its not random motion, but neither is it all that predictable, except that the pattern exists at all scales: its fractal. In other words, if we sketched the motion of an animal on paper, and drew it to scale, it would look similar if we zoomed out to the range of kilometers instead of meters and drew the pattern again. It turns out that moving by way of Levy walks increases your chances of running into patches of food, or the trails of scent they leave behind. At that point, more directed motion takes over and the animal zig zags towards the source of that delicious scent (whereupon it becomes not too different from homing in on the Slim Jims at the Piggly Wiggly after all). Sims et al. show that Levy walks are almost ubiquitous among animals that seek mobile prey; they conclude that its a sort of biological rule for finding food that has a patchy distribution.

It’s a fascinating idea; I wonder if you could apply a deliberate Levy walk pattern if you were looking for your sunglasses, trying to find Waldo, or trying to find an empty patch of beach to put your towel on. People might look at you a bit funny, but who’d have the last laugh?

Sims, D., Southall, E., Humphries, N., Hays, G., Bradshaw, C., Pitchford, J., James, A., Ahmed, M., Brierley, A., Hindell, M., Morritt, D., Musyl, M., Righton, D., Shepard, E., Wearmouth, V., Wilson, R., Witt, M., & Metcalfe, J. (2008). Scaling laws of marine predator search behaviour Nature, 451 (7182), 1098-1102 DOI: 10.1038/nature06518

Sunday, May 30, 2010

Play Bit-o-critter, round 19

See if you can identify this critter, based on the bit given below.  The winner gets bragging rights and a warm inner glow.

No rest for the wicked

Returned from the Eastern Fish Health Workshop in the DC area yesterday, after our flight got canceled on Friday.  It was a fantastic meeting, for all the reasons I cited in my previous post. 

I've got one day at work today and then off to Mexico for field research with Mexican government colleagues this week (more about that later), but not for long, because teaching duties in NY on Friday and Saturday call.  While I am in NY, I'll be giving a public lecture about whale sharks at Stony Brook Southampton on the 4th at 1930hrs.  Its part of the SoMAS Spring lecture series; I'd love to see you there!

The solution to Bit-o-Critter round 18

Nobody guessed at BoC round 18 on the blog, although one colleague got it right on Friend Feed.  It was the eye and proboscis of a stromb, which is a big family of marine gastropod snails.  They are related to cone snails, but can always be distinguished by a ntoch on the margin of their shell that allows them to poke out the eyes and look around.  They have very engaging, almost comical eyes, but they probably don't see the world as we do.  The particular one I chose was a spider shell, which you often see for sale in tourist shops (and shouldn't buy, naturally)

Tuesday, May 25, 2010

EFHW the first day

They don't muck around at this meeting. Registration is from 5-8 on Monday, then talks from 8-11. Thankfully first night is mostly short talks and you can bring beers into the lecture hall - that's my kinda conference!

This morning has been all immunology. That's not normally my bag, but talented speakers can make the most arcane topics engaging. Steve Kaattari spoke about how antibodies can me made more or less specific through sulfide cross-linking, without changing their actual amino acid sequence. Erin Bromage also gave a great talk about how the immune systems of fish are concentrated in the kidney, and how the immune system can lose its memory of previous antigens in the face of new challenges. The upshot of all the talks is that fish immune systems are different from mammals and in many ways more complex, which may be unexpected given our usual biased view of "mammals do it BEST".

More to come...

Sunday, May 23, 2010

This week: Eastern Fish Health Workshop

There's a special conference every year that's one of the best kept secrets in the fish world; its the Eastern Fish Health Workshop and this year its in sunny Shepherdstown WV, home of the National Fish Health Research Laboratories, which (as a quirk of history) are part of the USGS's Leetown Science Center.  I've been going ever since I came to America in 2000 and I just love it.  Why?  Well, its a combination of things.  Its small, usually around 100 people, which means you can spend some quality time with your colleagues. There's no concurrent sessions, so you aren't forced to miss anything, and there's also no poster sessions, which I consider to be largely a waste of time.  It covers a great diversity of topics - fish health in aquaculture, wild fisheries, coral health on reefs, aquarium animal health, crustacean health and mollusc sessions, as well as thematic sessions like immunology and chemotherapy.  There's no more diverse such conference annually, probably because its not affiliated with a scientific society that would limit scope.  The only meeting that comes close is the ISAAH, in Tampa later this year, and that only runs every 4th year.  But the best thing about the meeting is the people.  Perhaps as a result of its breadth of subject, it attracts folks of broad vision and diverse interests and I just love that.  I always leave energised by the people I meet and topics we discuss.  Indeed, one of my biggest current projects - metabolomics of whale sharks (more on that in future posts) - was inspired by an EFHW talk by Andrew Dacanay a few years back.

This year's conference is especially important because its the 35th anniversary!

So, I'll be in WV this week and will try to blog some about the talks as they happen.  This will mean writing from the Droid, so forgive me if things come across a little stilted.  Its an a amazing device, but its no substitute for a real computer.  It also means I might not do any blogging on peer reviewed research this week.  I'd like to think I'll be studious and go back to my room for that stuff, but there's more to be gained by picking someone elses brain.  Perhaps I'll post some interviews instead.

Friday, May 21, 2010

The Travel Bug bites hard, but it hurts so good

Just once in life I did the totally reckless thing of looking at a photo (in a Lonely Planet guide, if I remember) and saying "Thats it, I am going there, now" and then doing exactly that.  The place was Leh, which is in region called Ladakh, in the province of Jammu & Kashmir in Northern India.  Not once did I ever regret that decision; Leh was one of the most magical places I ever visited, probably made moreso because of the liberating decision to go half way round the world to see it and the good buddies I shared the experience with.

Well, I feel the same bite about Saba in the Netherlands Antilles.  Every time I look at a photo of that little volcanic speck and imagine the hair-raising landing at the airport, followed by the equally follicle-lifting drive through a myriad switchbacks clinging to the side of that impossibly steep volcanic plug, I can barely resist the urge to just walk out the door, head for Hartsfield-Jackson and jump on a plane.  I have assiduously suppressed these feelings for years in favour of pedestrian realism, but now PLoS One has published a series of papers about the diversity of critters on the bank reef adjacent to Saba.  How am I supposed to resist that?  Thanks a lot PLoS...

Somebody help a travel junkie out; either convince me to go, or talk me down!  Ever been there?  Whats it like?
Picture from Throwingpoo.com (I kid you not)

Thursday, May 20, 2010

12,081ft - The oceans, by the numbers

I was inspired by recent articles highlighting a revised calculation of the ocean’s average depth as 12,081ft, to consider the seas in a numerical light today. To that end, here’s a few random, sourced numbers and back-of-the-envelope calculations that might be food for thought:

0.87% = Amount we can see by diving from the surface (about 100ft) over the average depth
0.28% = Amount we can see by diving over the deepest part (Challenger Deep, Marianas Trench off the Philippines)
2.9 = Number of times deeper the deepest part is, compared to the average.
5,400 = Number of mammal species in the world
25,000 = Number of fish species in the world
Millions? = Number of marine invertebrates species in the world (no-one really knows)
2.3 Million = The number of US citizens directly dependent on ocean industries (source: NOAA)
$117 Billion = Value of ocean products and services to the US economy (yr 2000, source: NOAA)
50% = US population living in coastal zones
48% = The proportion of all human-produced CO2 absorbed by the oceans in the Industrial era (NatGeo)
0.1 = The pH drop in the surface oceans since 1900
0.35 = Expected pH drop by 2100 (source)
18 = The number of times more heat absorbed by the oceans than the atmosphere since 1950 (source - TAMU). Global warming is an ocean process far more than an atmospheric one.
3.5 Million = Estimated tons of plastic pollution circling in the Great Pacific Garbage Patch, and growing.

And yet:

30 = Number of times thicker the atmosphere is (out to the “edge of space” about 60 miles) than the average ocean. That would be the atmosphere that astronauts describe as a “thin veneer” on the planet…
0.06% = Thickness of the average ocean, compared to the radius of the earth. I think we can argue that the water is the veneer, not the air
$4.48 Billion = NOAA’s 2010 budget, including the National Ocean Service, Weather Service and Fisheries Services. (source NOAA)
$18.7 Billion = NASA’s 2010 budget, i.e. 4 times the size of the agency that looks after our own planet (source NASA)
$664 Billion = Department of Defense base budget 2010, not counting special allocations (source DoD)
0.6% = The amount you would need to cut Defense in order to double the NOAA budget

Some sources:
http://www.corporateservices.noaa.gov/~nbo/FY10_BlueBook/NOAAwide_One_Pager051109.pdf
http://www.corporateservices.noaa.gov/~nbo/10bluebook_highlights.html http://news.nationalgeographic.com/news/2004/07/0715_040715_oceancarbon_2.html  
http://oceanworld.tamu.edu/resources/oceanography-book/oceansandclimate.htm
http://web.archive.org/web/20080625100559/http://www.ipsl.jussieu.fr/~jomce/acidification/paper/Orr_OnlineNature04095.pdf  

Wednesday, May 19, 2010

Play Bit-o-critter, round 18

This one's a little harder; but I think you guys are up to the challenge...

The solution to Bit-o-Critter round 17

Juliebug nutted out that the critter in round 17 was a hyperiid amphipod.  Hyperiids are freaky looking things, like the sort of thing H.R. Giger might have used for inspiration for the creature from Alien.  Julie also uncovered some stories about swarming hyperiids, predatory hyperiids and parasitic hyperiids.  Check it out

Tuesday, May 18, 2010

Just like cows, fish chew their cod

ResearchBlogging.orgBaddum-tish!  OK, they don't chew their cud, but I can never resist a good pun (although I was seriously considering "Ruminations on the way fish eat" - better?).  I just love this new paper by Gintof et al. about how fish chew, mostly because its an idea that I never would have ever considered.  Basically, they explored whether fish just bolt their food, like lizards and snakes, or whether they engage in "intra-oral prey processing" (= chewing, sometimes sicnetific jargon cracks me up).  After looking at several model fish species, they conclude that yes, fish chew, and they chew about as many times as mammals do.  Its not like mammal chewing (especially herbivores) in that there is little side-to-side motion, but its rhythmic, and thats the most important thing.  This means that the bolting of food by lizards and snakes represents evolutionary loss of chewing, or that the model fish and all mammals both evolved chewing separately (they call this convergent evolution). 

They looked mostly at "basal" fishes like pikes, salmons and arowanas, that is, fish that show the most in common with the ancestors of all fish - I hate to use the term "primitive".  Its significant because it shows that chewing showed up early on in fish evolution.  One theory they put forth for the early appearance of chewing is that the rhythmic pumping of the jaws was necessary to keep fluid moving through the mouth and gills while eating.  Under that view, breathing water through the mouth and gills preadapted all who came after for processing food in their mouth, as opposed to, say, lobsters, whose teeth are in their stomachs.  I would dearly have loved it if they had included a more derived fish like a perch, pufferfish, or the sheepshead (with creepy human-like teeth, shown hereabouts) to show that chewing persisted in other branches of fish evolution, but you can't have everything.

Its a fun paper, you can read it here:

Gintof C, Konow N, Ross CF, and Sanford CP (2010). Rhythmic chewing with oral jaws in teleost fishes: a comparison with amniotes. The Journal of experimental biology, 213 (Pt 11), 1868-75 PMID: 20472774

Monday, May 17, 2010

Q: What do Sam Waterston and Sigourney Weaver have in common?

A: They are both actively drawing public and legislative attention to the issue of ocean acidification.   That is, the decrease in the pH of the sea as a result of its absorbing increasing amounts of atmospheric CO2, that most pernicious of greenhouse gases.  Waterston, who is on the board of Oceana, was just testifying in DC about it, as Weaver was recently.

Oh, and if you thought this post was going another direction, here you go:

Sam Waterston was in 1976's Sweet Revenge with Norman Matlock who was in 1984's Ghostbusters with Sigourney Weaver.

There you go Kevin Bacon, you're not so special after all, anyone can do it...

Seaweeds and corals go through the media meat-grinder

ResearchBlogging.org“If it bleeds it leads” is a common meme in the journalism field, but when it becomes the mantra of science reporting, sometimes the real message gets lost in translation. Unfortunately, so it is with a new paper from Doug Rasher and Mark Hay down the road at Georgia Tech. In their work, published in PNAS this week, they show that algae from coral reefs can have toxic effects on adjacent corals including bleaching (expulsion of the symbiotic algae that are responsible for much of the corals success) and even death. They provide evidence that these effects are mediated by lipid soluble compounds and that they are much reduced on reefs that have healthy herbivorous fish populations to keep the algae in check. There, I summarized their work in 2 sentences. It’s disappointing, then, that the NSF (NSF for goodness sake!) turned that into “Killer Seaweed: Scientists Find First Proof that Chemicals from Seaweeds Damage Coral on Contact”. Unfortunately, that kind of catch-phrase gets picked up all over, so that MSNBC ran with “Killer seaweed threatens corals: Innocent-looking species turns into an assassin of nearby reefs” (assassin? Really?!). The Georgia Tech website went with “Research shows that chemicals from seaweed kills corals on contact”. Not as dramatic perhaps, but more reasonable. Ed Yong at Discover Blogs chose to emphasise the fish side of the story: “Overfishing gives toxic seaweeds an edge in their competition with corals”; both these seem fine to me, but honestly, I don’t know what’s wrong with using the title of the paper “Chemically rich seaweeds poison corals when not controlled by herbivores”. I think Rasher and Hay did a good job distilling the essence of the paper into a punchy and information-dense title. In any case, its frustrating to see crux of a paper lost in attempts to sensationalise the story, as did all the outlets who went with the “killer seaweed” theme.

Putting aside the press treatment, I think there’s an important part of the story missing from this paper. In it, Rasher and Hay report that in the absence of herbivores, 40-70% of common seaweeds cause bleaching of a model coral species (Porites), depending on where you are. If you average that – 55% - then roughly half of seaweeds were toxic to their model coral. On this proportion and their comparison of overfished and non-overfished reefs, they base the conclusion that these algae are bad for corals, that herbivores suppress the algae and, therefore, that overfishing will increase coral declines by allowing toxic algae to proliferate. All of these seem reasonable ideas, but I kept asking myself: what about the reciprocal effect? What percentage of corals are antagonistic to algae? If, say, half of all corals can damage adjacent algae, then the net effect of all this antagonism at the largest scale is zero. If half of algae kill corals and half of corals kill algae, it could be zero sum. This seems important to me, because it would undermine the conclusion that overfishing of herbivores will necessarily lead to declines in reef corals. Indeed, I could make the reverse argument that overfishing of corallivores (fish that eat corals) might lead to proliferation of corals and therefore the decline of reef algae. We just don't know because that work hasnt been done. 

Of course, you can’t include everything in a single paper and I would expect the authors to respond to my point by saying that the experiments I describe were beyond the scope of their project. But I think it could have been a better paper if they acknowledged that there’s another possibility that cannot be excluded, based on work that’s yet to be done.

Rasher, D., & Hay, M. (2010). Chemically rich seaweeds poison corals when not controlled by herbivores Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.0912095107

Sunday, May 16, 2010

Play Bit-o-Critter round 17

A family will do fine today


Saturday, May 15, 2010

Calling the corals home

Ed Yong at Discover Blogs has a great post up about a PLoS One paper describing how coral larvae find their way back to the reef from the plankton, using sound.  This is a remarkable ability for a tiny ciliated ball of cells, demonstrated through a nifty experiment where the scientists played sound from different directions into a dish of tubes containing coral larvae and showed that they moved towards the speaker playing sounds from a reef.


Putting aside the remarkable little larvae, maybe we shouldn't be surprised. Anyone who has ever put their head underwater on a reef, especially a Pacific reef, can tell you they are noisy places.  I always thought it sounded like frying bacon - a sizzling crackle of clicks, pops, scrapes and cracks, courtesy of snapping shrimps, parrotfish and a myriad other beasts.  The first time I heard that sound I remember being startled, and then amazed.  Serene underwater scenes?  Serene, my butt!

The solution to Bit-o-Critter round 16

Miriam from DeepSeaNews correctly identified Glaucus atlanticus, a spectacular pelagic nudibranch.  Like a lot of neustonic animals, they are bright blue, which relates to the intense sunlight exposure they get in the top inches of the ocean.  The same blue coloration is seen in calanoid copepods, jellies and other things that live right at the surface. 
This pic of Glaucus from Wikimedia Commons.

Friday, May 14, 2010

The solution to Bit-o-critter round 15

As Akira so succinctly put it - Euthynnus alletteratus.  To the rest of us, that's the little tunny.  In his follow-up, Aki pointed out that the spots below the pectoral fin were the give away - no other tuna has them.

Play Bit-o-critter, round 16

The fish people have had it way too easy lately, so here's one of "the other 95%"


Remember - if you get it right, you have to follow up with some details so the rest of us learn something

Whale sharks start to give up their secrets

ResearchBlogging.orgWhale sharks are the largest fish in the oceans; they can grow to 20m in length and weigh many tons, although 7-9m is closer to the common average these days.  Despite their tremendous size, scientists don't know that much about them.  We know that they eat plankton and that they live in the tropical oceans throughout the world and there have been quite a few papers reporting their presence in different waters, but these represent only the most basic foray into the biology of a species.  More recently, there's been a few more including one that explores genetics (Castro et al., see below) and some that have started to explore behaviour (see Brunnschweiler et al.).  Up to this point, the focus has all been external; that is, only the biology that can be observed from the outside.  That's no surprise really; its a logical place to start and there are some huge logistic challenges to working with whale sharks, as you can probably imagine.

There are 4 whale sharks in the collection at Georgia Aquarium in Atlanta and I have been lucky enough to work with these amazing animals since 2006.  Part of that work has involved veterinary examinations, which has allowed us, for the first time, to look at aspects of the internal biology of whale sharks. The first part of that work is now in print: a paper I co-authored with the aquarium's principal clinical vet, Dr. Tonya Clauss, and a colleague from National Aquarium in Baltimore, Jill Arnold (Jill is an expert in medical techniques, especially blood work), which is in the latest issue of Aquatic Biology.  Our paper is a discovery-based one (i.e. not testing a specific hypothesis) about the nature of the blood of whale sharks, both the cells and the chemistry of the blood serum.  Its open access, so you can get it at the journal web page here

In it, we show that whale sharks have blood that is fundamentally similar to that of some other sharks, specifically the bottom dwelling ones like nurse sharks and wobbegongs, but pretty different from the toothy predatory sharks like great whites.  They have very large red cells, actually white cells too, but this is something they share with the bottom dwellers, so it appears to be a feature of the group rather than a function of the size of the whale shark as such.  Whale sharks are the only pelagic members of that group, the order Orectolobiformes.  Why such large cells, then?  Our study didn't answer that question, but my best guess is that they have relatively low metabolism compared to the carcharhinids, which may need the high relative surface area of smaller red cells to improve the movement of oxygen in and out of cells.  This is the first of several hypotheses that we can only begin to pose because of these first discovery-based efforts.

I can't tell you how excited I am that we can begin to share what we've been learning at the Aquarium.  The chance to work with whale sharks is a real gift for a fish nerd like me, and the opportunity afforded by having access to them in the more controlled environment of an aquarium makes it possible to do safely and effectively research that has been prohibitively difficult with free-ranging whale sharks up to this point.  Of course, the ultimate goal is to extend that work to compliment the field research, and I look forward to telling you more about that in future posts.

Brunnschweiler, J., Baensch, H., Pierce, S., & Sims, D. (2009). Deep-diving behaviour of a whale shark during long-distance movement in the western Indian Ocean. Journal of Fish Biology, 74 (3), 706-714 DOI: 10.1111/j.1095-8649.2008.02155.x 

Castro, A., et al. (2007). Population genetic structure of Earth's largest fish, the whale shark ( )
Molecular Ecology, 16 (24), 5183-5192 DOI: 10.1111/j.1365-294X.2007.03597.x
 

Dove, A., Arnold, J., & Clauss, T. (2010). Blood cells and serum chemistry in the world’s largest fish: the whale shark Rhincodon typus Aquatic Biology, 9 (2), 177-183 DOI: 10.3354/ab00252

Monday, May 10, 2010

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.

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, May 9, 2010

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, May 7, 2010

Play Bit-o-critter, round 14

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

Thursday, May 6, 2010

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, May 5, 2010

The solution to Bit-o-critter round 13

Twas the torpedo ray, Torpedo panthera

Tuesday, May 4, 2010

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.

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, May 3, 2010

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, May 2, 2010

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.

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.

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.

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