Navigation
Twitter and News feeds
Search this site
Networked Blogs
Tuesday
Apr062010

Explosive radiation (in) rocks!

ResearchBlogging.org

Much like internal waves, I always loved the idea of explosive radiation.  Not the nasty, pernicious Chernobyl kind; I mean the rapid evolution of a whole bunch of species from a common ancestor, over a relatively short period of time.   There's a few textbook examples of explosive radiations, but none so well-worn (possibly even hackneyed) as that of the cichlid fishes in the rift lakes of eastern Africa.  The startling diversity of these little fishes in lakes Tanganyika, Malawi and Victoria has kept evolutionary biologists busy (and Africans fed) for years.  See for example, the paper by Elmer and colleagues cited below, which points out that due to the drying-out of Lake Victoria 15-18,000 years ago, either all the cichlids there evolved since then based on stock that re-colonised from Lake Tanganyika, or they sought refuge elsewhere during the dry spell and returned when the lake refilled.

Cichlids are nice and all, but if you look around, you start to see radiations all over the place.  Turtles, bivalves and salamanders in the US south-east; tetras in the Amazon, eleotrid gudgeons in Australia, and gobies on coral reefs are just a handful of aquatic examples that are still with us, but there are many others in the fossil record too (hence my title) including trilobites and ammonoids and lots more.  Presumably these are the sorts of patterns that led Stephen Jay Gould and Niles Eldredge to develop the concept of punctuated equilibrium back in the 70's: theirs was the idea that evolution proceeds not gradually, but in fits and starts, in response to dramatic environmental changes and chance events.  The way I see this idea, most of the species we observe around us are the dregs of explosive radiations past, whittled away by extinctions to just the most successful few, either gradually or equally punctuated.  Cases like the rift-lake cichlids are just ones in which relatively few have gone extinct yet (but see the effects of the introduced Nile perch!)

All of this was just a preamble for what I really wanted to post about, which was about a radiation I only heard about recently.  Late last year I was at a scientific exchange  of US and Russian fish health researchers organised by the National Fish Health Research Laboratories and sponsored by the Living Oceans Foundation, at which one of the Russian speakers  Maxim Timofeev introduced us the radiation of several groups, including amphipods, in Russia.  Amphipods are (usually) tiny shrimp-like animals that live on the bottom or among dense plants or algae; read more about them in the Väinölä paper cited below.  Well, in Siberia's Lake Baikal, the worlds oldest, largest and deepest freshwater lake, they underwent a remarkable radiation, to produce over 300 species (a third of the worlds entire fauna), including spectacular beasts such as the fish predator (!) shown here. I mean, HOW AWESOME IS THAT THING?  Freaks me almost as much as giant wetas used to do, when I was younger (if you don't dig on bugs, I recommend not clicking that link...).  Anyway, I had no idea these things existed until Maxim gave his talk.  Don't you just love discovering new critters you never knew about before?  And not just one, but hundreds.

(Check out this link about Baikal fauna too; the language is just terrific.  Try this turn of phrase on for size: "When it comes to tenderness and gustatory qualities of meat, the omul knows no rivals")

Elmer, K., Reggio, C., Wirth, T., Verheyen, E., Salzburger, W., & Meyer, A. (2009). Pleistocene desiccation in East Africa bottlenecked but did not extirpate the adaptive radiation of Lake Victoria haplochromine cichlid fishes Proceedings of the National Academy of Sciences, 106 (32), 13404-13409 DOI: 10.1073/pnas.0902299106

Väinölä, R., Witt, J., Grabowski, M., Bradbury, J., Jazdzewski, K., & Sket, B. (2007). Global diversity of amphipods (Amphipoda; Crustacea) in freshwater Hydrobiologia, 595 (1), 241-255 DOI: 10.1007/s10750-007-9020-6

Thursday
Apr012010

I'm surfing on the inside

I've always loved the idea of internal waves; the idea that gentle, rolling, and sometimes very large waves roll along, not on the surface of the sea, but deep below it.  How is that possible?  The best explanation is by analogy:  If you've ever swum in a lake in early summer, where your body was bathed in warm still surface waters but your legs were down in the icy deeper layer, then you've crossed the boundary that internal waves call home.  They travel along "density boundaries" and the most common of those is the bit where water goes from warm at the surface to cold at depths, called the thermocline; there are other types of density boundaries too, such as where fresh water overlies denser briny water.  Sometimes you can even see density boundaries near the surface; the change in density affects the way light passes through the water so you can sometime see a shimmery sort of distortion, even though the water is clear.  There's a good one shown here. The picture at right from the Institute of Hydromechanics at the University of Stuttgart shows an artificial internal wave produced as part of an experiment; they dyed the different densities of water to show it better.

The bigger the change from warm to cold in a thermocline, the bigger the density difference, with the colder water being more dense.  Really sharp thermoclines like this have some interesting properties, such as the ability to reflect some types of sonar.  In fact, Navy submarines have been known to "hide" below a good thermocline, and then be revealed for all to "see", by a passing internal wave.  The sub is below the thermocline one minute, then above it the next, exposed and vulnerable to the next sonar ping - oops. 

Internal waves can even "break", like a surf wave on a beach.  This image from Memorial University in Canada shows a model of how this happens, with the wave coming in from the left and breaking on the bottom as it gets shallower; all the while the water's surface is calm.  The internal wave doesn't look quite the same as a regular beach wave because the density difference isn't nearly as much as when you go from water to air and the internal wave pushes up against the heavy, viscous overlying water, but the principle is the same.

I don't know if its possible to somehow surf on an internal wave.  I doubt it, because the drag of the overlying water would be much more than you would experience in air, but its pretty cool to think about.  Its probably a good thing if you can't do it, because Al surfing is about the only thing scarier than Al dancing...

Wednesday
Mar312010

When can we stop sampling and have a beer?

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

Yesterday I got a very kind email from a fellow scientist, Eric Seabloom at Oregon State University, letting me know that a paper I wrote with my PhD advisor Tom Cribb (University of Queensland) a few years ago had influenced a recent publication of his.  My paper was about one of those patterns in nature that just seem to be universal.  They're called species accumulation curves and, at the heart of it, they represent the "law of diminishing returns"* as it applies to sampling animals in nature. Basically, they show that when you first start looking for animals - maybe in a net, a trap or a quadrat - pretty much everything you find is new to you, but as you go along, you find fewer and fewer new species, until eventually you don't find any more new species.  Simple, maybe even obvious, right?  Well it turns out that that simple observation has embedded within it all sorts of useful information about the way animal diversity is spread around, and even about how animals interact with each other in nature.  Consider the figure on the above right, which represents two sets of 5 samples (the tall boxes), containing different animal species (the smaller coloured boxes).  The first thing to note is that both set (a) and set (b) consist of 5 samples, and both have a total diversity of 5 species (i.e. 5 different colours).  In set (a), all the diversity is present in every sample, but in set (b) there's only one species per sample, so you have to look at all 5 samples before you find all 5 species.  If you were to plot a graph of these findings, you'd get very different species accumulation curves; they would both end at 5 species, but they would be shaped differently.  They'd look much like what you see below:

 Set (a) would be more like the curve on the left (in fact, it would be a perfect right angle), while set (b) would be more like the curve on the right (in fact, it would be a straight diagonal line).  You can see some other properties on the two types of curves above also, for the more ecologically inclined, but the gist is, the shape of the curves means something about the communities they describe.

Tom and I wrote our paper after many nights in the field spent dissecting coral reef fishes to recover new species of parasitic worms - a time consuming and sometimes tedious process (sometimes thrilling too, depending on what you do or don't find).  We were often motivated by another far more important factor too - when can we stop all this bloody sampling so that we can go and have a beer on the beach?!?   Species accumulation curves therefore have a very practical aspect to them - they tell you when its OK to stop sampling because you've either sampled all the available species, OR, you've sampled enough to extrapolate a good estimate of how many species there might be.

Back to Eric Seabloom.  He and his colleagues wrote a paper about the diversity of aphid-borne viruses infecting grasses of the US Pacific northwest and Canada.  While the environment that they sampled was about as far away as its possible to be from the coral reefs that Tom and I looked at, the patterns of saturated and unsaturated communities they observed were the same. I get a huge buzz out of that, and that out of the morass of published science out there, Dr. Seabloom found a scientific kindred spirit who had had the same thoughts and ideas about nature, however different the specific areas of study.  While Tom and I sipped beers on the beach and watched the sunset over the reef, I wonder if Eric and his colleagues blew the froth off a few while they watched the wind waves spread across the grasslands.  There's something so unifying about science; it can give you common ground with someone you never would have otherwise known, and that's just one reason why I love it so much.

*The tendency for a continuing application of effort or skill toward a particular project or goal to decline in effectiveness after a certain level of result has been achieved. Answers.com 

DOVE, A., & CRIBB, T. (2006). Species accumulation curves and their applications in parasite ecology Trends in Parasitology, 22 (12), 568-574 DOI: 10.1016/j.pt.2006.09.008

ERIC W. SEABLOOM, ELIZABETH T. BORER, CHARLES E. MITCHELL, & ALISON G. POWER (2010). Viral diversity and prevalence gradients in North American Pacific Coast grasslands Ecology, 91 (3), 721-732 (doi:10.1890/08-2170.1)

Wednesday
Mar312010

Not the Dry Tortugas, as such...

ResearchBlogging.org
...more like the Floating Tortugas.  An article in Science Now and The Journal of Experimental Biology reports on mysterious gatherings of loggerhead turtles in the Mediterranean, resembling an island made out of turtles.  It seems the critters gather to soak up the midday sun.  We probably should be surprised given how common basking is among reptiles, but loggerheads are known to spend most of their time on the bottom, so its a bit unusual.  What I find even more cool about this story is that its only now just being described, even though its in the middle of one of the busiest bits of sea in the world; how did no-one ever report on this before?  I love that there's still new stuff to discover everyday, and 90% of it is in the ocean, even the most familiar stretches.  A virtual island raft composed entirely of turtles - can you just imagine?

Knight, K. (2010). LOGGERHEADS STAY AT SURFACE TO SOAK UP SUN Journal of Experimental Biology, 213 (8) DOI: 10.1242/jeb.043901

Tuesday
Mar302010

Ocean Conveyor running AMOC

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

If you’ve ever seen the disaster movie “The Day After Tomorrow”, then you’ve been introduced to the idea that one day the global ocean conveyor might stop.  Its a pity (or perhaps not) that the movie was such a sensational introduction to the concept, because its a pretty serious possibility.  By way of short explanation: one of the things that makes life possible on this rock is that the ocean redistributes heat that arrives on the earth’s surface between the tropics, sending it to the higher latitudes by way of warm surface currents.  There, the waters are cooled and made more dense (both colder and saltier) by the polar ice caps; they then sink and begin a slow meander back to the tropics, eventually returning to the surface to complete the cycle.  Without effective redistribution of this sort, the tropics would bake and the polar zones would sink into a deep hard freeze (in both cases much more so than “normal”).  The climate in the UK, for example, would be much more like Siberia were it not of the tempering effects of the Gulf Stream continually bringing heat from the Caribbean to the North Sea.  An important point about the conveyor is that it is driven from both ends: by the suns heat near the equator and by the cooling effect of all that ice at the poles.

 Why would the conveyor grind to a halt?  The equatorial heat doesn’t show any sign of stopping; if anything its getting hotter.  No, the biggest fear is for the other driver: if the polar ice caps melt too much, there will no longer be a big enough reservoir to chill and brine the surface waters and they will cease to sink.  Some data from recent years suggested that this was happening, and happening fast.  Well, it seems as though Armageddon isn’t here just yet.  A new paper by CalTech/NASA’s Josh Willis in the journal Geophysical Research Letters uses a more complete data set than ever before to conclude that the conveyor, or more specifically a major section of it called the Atlantic Meridional Overturning Circulation (AMOC - hence the corny title of my post) measured at 41°N (near where it says “Atlantic” on the figure above), is not slowing.  In fact, there is some evidence that it may have sped up marginally in recent years, perhaps in response to warming and expansion of Atlantic waters.  The data were consistent across both satellite sources and sensor arrays deployed in the oceans, so it would seem like a pretty robust study (though I am no physical oceanographer).

I am sure I speak for everyone on the bonnie British Isles when I heave a sigh of relief.

But wait?  What light through yonder ice-shelf breaks?  Tis Greenland, and its seeing more of the sun!  In the very same issue of Geophysical Research Letters, a different group of authors report that ice loss is increasing from the Greenland ice sheet.  This is one of the major impacts of recent climate warming and the greatest contributor to increases in sea level globally.  It would also freshen the north polar waters, further reducing the driving force behind the global ocean conveyor.


My response to this news is to marvel at - and grapple with - the complexity and dynamics of the earth and its climate system.  Scientific results with seemingly opposite implications can come out (in this case in the same journal issue), but without threatening the major underlying pattern; I doubt, for example, that Dr. Willis would disagree with the concept of man-made climate change.  Faced with this seeming contradiction, its perhaps no wonder that many folks grapple with the Big Ideas at the heart of global climate change, and even doubt that it exists at all.  I for one have no doubt  that things are changing, and changing fast.  It may just be that some of the really big features of the climate system (including ocean currents) are slower to respond than others.  Its a bit like turning an oil tanker, which may be an unfortunately apt analogy…

Willis, J. (2010). Can in situ floats and satellite altimeters detect long-term changes in Atlantic Ocean overturning? Geophysical Research Letters, 37 (6) DOI: 10.1029/2010GL042372

Khan, S., Wahr, J., Bevis, M., Velicogna, I., & Kendrick, E. (2010). Spread of ice mass loss into northwest Greenland observed by GRACE and GPS Geophysical Research Letters, 37 (6) DOI: 10.1029/2010GL042460

Tuesday
Mar302010

CITES epic fail?

David Helvarg has a scathing OpEd piece in the Huffington Post yesterday, and rightfully so.  CITES, the Council for International Trade in Endangered Species recently failed to give proposed protections to the northern bluefin tuna and several species of threatened sharks, apparently caving to the desires of Japan and other nations with similar pro-harvest agendas.  I dont know how much data you need to be convinced that these populations are threatened to the point of collapse, but even if if there were equivocation on the science (and there's not), why not err on the side of safety?  Just as line calls in baseball go to the batter, decisions regarding endangerment should always go to the organism.

The way I see it, bluefin are stuck in a positive feedback loop of ever increasing commodity value, feeding more intense searching/fishing efforts, further reducing the population and thereby driving the value yet higher.  Its a trajectory that only ends one way, and it ain't a good one.

Oh, and if what Helvarg says is true about the Japanese embassy serving bluefin sashimi at a reception for the CITES delegates, then wow. Just, wow.  I sincerely hope those were artificially reared and not ranched or wild-caught...

Tuesday
Mar302010

More on the geo-hacking idea

Not so long ago I posted about the idea of capturing all the extra atmospheric CO2 into the worlds oceans by fertilising them and thereby creating enormous plantkon blooms that would convert all the CO2 to plant tissues, which would then sink to the bottom and be buried in the ocean depths.  This new scientist article probes a different angle that I didn't think of, which is Who decides what we will or won't do to change these things?  The author Jim Giles refers not just to ocean fertilising, but engineering the whole planet to combat climate change - what has become popularly known as "geo-hacking" - including sensible concepts like reforestation and cloud seeding, as well as the more absurd notions such as building giant reflectors to bounce the sunlight away.  Its a thought provoking question, so who do you think should decide these issues?  The US? UN? UNESCO?  Perhaps we need a new body with that as its sole charter?

Saturday
Mar272010

The ghost of fishers past

The folks you see out on their boats on the bay are not the only ones fishing; those who came before them still get a slice of the action, as this recent article about the retrieval of "ghost gear" from the Chesapeake Bay illustrates.  In many trap-based fishing industries, like lobsters and crabs, a significant number of traps are lost during the course of regular fishing efforts.  In addition, when a fishery turns bad, as happened in the Long Island Sound lobster fishery in 1999, some fishers cut their losses, and their marker floats, quit the fishery and just leave their gear where it is on the bottom of the bay.

The problem is, ghost gear like this keeps on fishing, long after the fisher has moved on to other endeavours.  The design of the trap continues to attract animals, even without bait, because the trap is basically a refuge or cave.  Those that enter are unable to leave and as they die they may act as bait to attract yet more animals to feed on their body.  In this way, the trap becomes a sort of "biomass black hole", sucking in animals from all around, for as long as the trap holds together.  Nets can ghost fish too, especially gillnets or any kind of trawl that can trap fish or strangle a reef

We used to trawl up ghost lobster gear all the time when I was working in Long Island Sound.  Indeed, few days on the water went by without snagging someone's old gear at some point, which speaks to the density of gear that's out there in some inshore waters.  I'm glad the fishers and the resource management agencies are working together to address the problem, because its one of those awful chronic out-of-sight, out-of-mind issues that can erode a fishery despite everyone's best efforts to manage things properly.  If you find ghost gear, call your local DEP or DEC, even the EPA, and let them know so they can come and retrieve it.

Picture of ghost gear on a coral reef from NOAA

Friday
Mar262010

Funny scientific names - Abra cadabra

I started my career in taxonomy.  Its a serious business, the naming of new species, and you're not supposed to make light or fun out of an animal (or plant) name.  After all, they are stuck with it for all time.  Nonetheless, people can't help themselves and from time to time, you get some real crackers!  A fella by the name of Arnold Menke at USDA put together a list of them, so did Doug Yanega.  Here's some of my favourites.  Which do you like best?

Agra vation (a beetle)
Colon rectum (another beetle)
Ba humbugi (a snail)
Aha ha ( a wasp)
Lalapa lusa (a wasp)
Leonardo davinci (a moth)
Abra cadabra (a clam)
Gelae baen, Gelae belae, Gelae donut, Gelae fish, and Gelae rol (all types of fungus beetles)
Villa manillae, Pieza kake and Reissa roni  (bee flies)
Ytu brutus (a beetle)

and my personal favourite (whenever possible):
La cerveza (a moth)

I'll drink to that - here's cheers to creative taxonomists!

Friday
Mar262010

Lionfish - more spectacular than your average invasive, but still a right pest.

When we think of invasive species, flamboyant fish from coral reefs are not usually the first thing that comes to mind.  Indeed, if you put together a list of characteristics of successful invasive species (like this one), "boring" would probably be close to the top, along with being quick to reproduce, not fussy about what you eat, having a large natural range, a great tolerance for extremes in the environment, and lacking natural enemies such as predators or parasites.  Think of some of the most successful invaders and decide for yourself if these predictions hold true: carp, starlings, mosquitofish, rats, sparrows, mice, rabbits, dogs, cane toads, cats, foxes, kudzu, chickweed... 

All this makes the invasion of the Atlantic seaboard by the Pacific lionfish, Pterois volitans, all the more remarkable.  Lionfish are flat-out spectacular!  Long prized as an aquarium specimen, they have bold stripes that spill over onto their fantastically long and showy fins; their scientific name even means "fluttering wings".  The sheer beauty of lionfish doubtless plays a role in how they came to invade the Atlantic in the first place; most likely they were an escaped or released aquarium species that found itself able to survive quite nicely in the conditions of the coastal Atlantic.  The beauty of lionfish conceals a dangerous secret - venomous spines on their dorsal (back) and pelvic (bottom) fins.  While they won't kill a person; they cause excruciating pain.  I've never been stung by one, but I have been stung by related scorpionfish (most recently the short-spined wasp fish) and the feeling is not one I'd care to go through again!

Over the course of just a few years, mostly since 2000, lionfish have spread dramatically along the coast of the Atlantic, from North Carolina down to the southern Caribbean and Mexico's beautiful Yucatan peninsula.  Typically considered to be a rocky or coral reef species, they've now been found swimming in the intracoastal waterway; that labyrinth of salt-marshes, channels and estuaries, engineered to allow safe passage of boats along the US coast in wartime.  This is sort of an unusual location, but it speaks to the adaptability of this remarkable fish.

So, what to do about such an animal??  Well, that's a tough one.  Invasive species (or more accurately, moving species around) are one of the greatest impacts humanity has had on natural environments, and there are very few cases where we have successfully eradicated or controlled an invasive (but see prickly pear in Australia), more often they just become part of the furniture and we get used to their impacts on the local ecosystem.  Introducing natural enemies (diseases, predators) like they did for prickly pear is a dangerous game; if you tried to get the Cactoblastus moth introduced to Australia in these days of stricter biosecurity, you'd almost certainly be denied.  You can easily get into a "spider to catch the fly" situation too; in fact that's how cane toads were introduced to many places - to control sugar cane beetles (which they suck at).  Perhaps the best approach is to do what we do best - create a market that will promote human efforts to exploit them, and then rely on the Tragedy of the Commons to do the work for you.  This has already been proposed with Asian carp.  Fortunately, it turns out that lionfish are not only spectacular aquarium fish, but also delicious in a white wine sauce.  I am sure that if we set our minds to it, we could do as good a job wiping out this species as we have with so many others.  So c'mon everyone and grab a fork; Save a reef - eat a lionfish, today!

(Photo and graphic from NOAA)

Thursday
Mar252010

Your calamari wants a flat screen

ResearchBlogging.orgOctopuses and their relatives are just incredible animals.  Not only do they manage to coordinate hundreds of suckers on 8 arms simultaneously without tripping over themselves (I can't even remember what I ate for breakfast) and have the most advanced eyes in the invertebrate world, but they can do other cool stuff like eat sharks,  fit through holes much smaller than themselves, use tools and learn from each other.  Now a new study has shown that they can tell the difference between regular TV and HD.  How did they determine this?  Simply, as it turns out.  The octopus show no reaction to footage of other octopus or crabs shown to them on regular TV screens.  When shown real crabs or crab footage in hi-def, however, the octopus lunged as if to attack the hapless decapod (video link).  In other words, octopus can tell the difference between real and imagery, if the image is not of high enough quality.
The explanation appears to lie not in the resolution of the screen (how small the pixels are) so much as how fast the picture can be draw and redrawn on the screen.  The picture on a TV screen is constantly being created line-by-line from the top of the screen in a process called rastering.  We don't perceive this rastering because it happens faster than we can see; faster than our "critical flicker frequency".  Well, not everyone has the same critical flicker frequency, and nor do all televisions have the same rastering rate.  Most hi-def TV's have a higher frequency (120 or even 240Hz, or times-per-second).  It may be that low-def TV is below the octopus critical flicker, but hi-def is above it.  In this way, they would see a sort of strobing effect in normal footage, but the hi-def stuff would look like, well, a crab.
The authors also noticed that the octopus showed "episodic personality", which is to say they were interested in the crab (or footage of another octopus) some times but not others.  I'm not sure I would class that as evidence of personality, just a less-than-100%-predictable response to a stimulus.  Having said that, ocotpus do have obvious personalities, which is one reason people are so drawn to them.  That, and sweet chilli sauce...

Pronk, R., Wilson, D., & Harcourt, R. (2010). Video playback demonstrates episodic personality in the gloomy octopus Journal of Experimental Biology, 213 (7), 1035-1041 DOI: 10.1242/jeb.040675

Wednesday
Mar242010

2 of the 10 worst jobs in science

Popular Science has just published its annual "Ten worst jobs in science" issue, and two of them are in marine science!  How is this possible?  Marine science is clearly the best job since, well, ever.  Hmmmm, lets take a closer look.

1. Oceanic Snot Diver.  The name sounds gross enough, but what does it mean?  Well, it turns out that they are talking about collecting "sea snot" true enough, but to call it nasty is a bit of a beat-up, IMHO.  Scientists call this stuff "aggregates", and its an incredibly important part of the nutrient cycle in the ocean.  Really, sea snot is just the secreted mucus and fecal casts of hordes of plankton.  Wait a sec, when you write it like that, it does sound gross!  Its biggest role is in "exporting" nutrients from the surface layers of the ocean, where the sun sponsors all that plankton growth, to the dark depths, where sunlight never penetrates, but life nonetheless thrives.  Not only do some animals down there eat the stuff (ew), but at those crushing depths, some of the snot also dissolves under the immense pressure of all the water above it, much like snow melting before it reaches the ground.  In this way, the snot plays a very important part in taking nutrients produced at the surface, and dissolving them in the water at great depths.  Maybe not the most attractive concept, but pretty important in the grand scheme of things.  Like Tom Cruise says in The Firm: "Its not sexy, but its got teeth". 

2. Whale slasher.  OK, I have to concede that one.  I've seen a few stranded whales being cut up on the beach (this is called a necropsy, not an autopsy, which is reserved for people only), and it pongs.  I'm not talking sweat sock pong, or even doggy-breath-after-eating-goose-poo pong, but serious, invasive, gets-into-your-hair, throw-your-clothes-away stink.  While the cause of death is always interesting, wading through week-old whale giblets that have been baking on the beach?  Not so fresh...

Monday
Mar222010

Fish as filters?

ResearchBlogging.org There's been a bit of press lately (see for example) surrounding a new paper from VIMS that concludes that the Atlantic menhaden or Bunker (Brevoortia tyrannus) is not very good at cleaning the Chesapeake Bay.  This seems an odd sort of paper but its actually not that crazy an idea.  Its turns out that lots of bivalve species like hard clams and soft clams actually pump enough water through their gills, sifting food as they go, that they can actually have a significant impact on the water clarity and nutrient content of the water.  Indeed, the zebra and quagga mussels that have invaded the Great Lakes have changed the entire ecosystem by doing exactly that.  With clearer water, there's less plankton productivity in the water column and more macrophytic plants and algae growing on the bottom.  Menhaden are filter feeders too, and they can occur in large schools, so perhaps its logical to think that they might be able to do the same sort of thing as the clams.  Alas, based on the VIMS experiments, it seems that they can't.

This is an interesting example of a negative result publication.  Often times you'll hear folks say we shouldn't publish negative results because, technically, you failed to prove that they clean the water, which is not the same as proving that they don't.  Well, as long as everybody is aware of that distinction, I still think negative results like that are useful to know, for two reasons.  One, its likely that they don't; if they do, then the effect is so minor that it was difficult to detect.  And two, it might save someone else from having the same idea and trying the same futile experiment.

The Chesapeake has some sporadic problems with hypoxia, which is ultimately a nutrient pollution issue, so I applaud the researchers for looking at a biological solution for what is otherwise a pretty intractable problem.

Monday
Mar222010

Cyclone Ului hits the Queensland coast

Tropical cyclone Ului hit the Queensland coast near the Whitsunday Islands and the towns of Proserpine and Bowen.  Apparently 60,000 odd people were without power after the landfall.  Its not the most densely populated part of the Queensland coast, but apparently Ului was a very tightly wound storm with a lot of energy close to the center.  Today will reveal how much damage occured; cross fingers...