Global warming isn’t increasing algal blooms … or is it?
One of the things I’m trying to do each week with this column is to show not just articles in science journals, but how science works. It’s not a story of constant agreement. It’s not a place where anyone gets awards for delivering a pat on the back to the last guy. It’s about progress through disagreement, about jumping ahead by not just standing on the shoulder of giants, but giving them a giant kick in the head. Understanding that these arguments take place, and that they’re not an example of “science was wrong” but genuine progress, is important to many, if not all, the arguments that touch on science.
So … algal blooms. Algal blooms are sudden, explosive growths of one or more kinds of algae. These algae can be toxic, like the blue green algae that have exploded to become threats in many lakes. They can be damaging to fisheries, like the red tides that are especially prominent along southern coasts. Often they’re damaging because they can lower the level of oxygen and nutrients in the water and, because the blooms are often just one type of algae, they can limit the amount of other plant life that can be vital to food chains.
Some months ago, a team from the School of Marine and Atmospheric Sciences at Stony Brook University in New York put out a model that suggested that as the oceans warmed, we should expect to see more of these algal blooms. This fits with previous research that suggests that warmer oceans represent an expanded opportunity for the kind of algae usually involved in these blooms.
But this week a team from the UK published results looking at some specific types of algae. And the result of studying records of samples taken since 1958, and Continuous Plankton Recorder data from the North Eastern Atlantic and North Sea over the last 30 years, didn’t show a strong relationship between temperature and the abundance of the algae they examined. Further, the Stony Brook team had predicted some algal “hot spots” which the UK team failed to find.
First of all … who knew there was Continuous Plankton Recorder data? Or that such instruments had been floating in the sea since 1982? Spiffy.
Secondly, the team from Stony Brook was also back this week, with a response on how the results from the UK team actually do fit with the model they predicted, arguing that the simple relationship between temperature and abundance of a specific species was not what their model called for, and that the UK team was undervaluing blooms that have appeared in the predicted regions.
And the winner is? Everybody. Will increasing temperatures really increase the number and range of algal blooms that generally occur in warmer water? It seems logical, but that’s not good enough. Models are going to made, tested, adjusted, knocked down, rebuilt, and tested all over again. Because … science.
Come on in. Let’s look at some more.
Infected elk race to out-evolve a killer disease
I’m pulling no punches: This is my favorite article of the week.
Chronic Wasting Disease is an infection that affects elk, deer, moose and reindeer. Basically, if it’s in the deer family, it can catch CWD. It’s invariably fatal. Infected animals first begin to move with an odd stiffness or trembling. They may begin to move slowly with their heads lowered, in a near fugue state, walking round and round along the same path. Elk with the disease slobber. A lot. That slobbering may be how the disease passes between animals. Eventually the disease matches its name. Infected animals cease to eat, waste away, and die.
If you’re not scared yet, try this name: Mad cow disease. Or this one: Kuru. Or this one: Alzheimer’s disease.
The cause of CWD is a prion. Prions, if you haven’t run into them before, are essentially The World’s Scariest Thing. They’re not bacteria. They’re not viruses. They’re not alive at all in any conventional sense. A prion is simply a protein—one that’s slightly twisted when compared to the normal proteins found in an animal. Once this twisted protein enters a system, it can cause generation of more of the malformed version. This bad prion can’t be broken down by the enzymes that normally clip proteins up to use in the body. So it accumulates.
In particular, the malformed prions accumulate in the brain, where they block small blood vessels. And cause the wonderfully awful term “spongiform encephalopathy”—lots and lots of holes in the brain. In the case of mad cow and (yuk) kuru, consuming prions can cause the prion disease to appear, but often symptoms don’t appear for years. In the case of Alzheimer’s, the appearance of malformed prions may be spontaneous, and possibly genetic. Does eating meat from an elk or deer infected with CDW cause a prion disease in humans? We don’t know. The long period between infection and onset means that the relationship between CDW in the deer family and disease in humans remains decidedly in the “we don’t know, consume at your own risk” category.
Now back to the elk and the subject of this week’s paper from the Proceedings of the National Academy of Science.
Elk infected with CWD are, not surprisingly, generally not winners in the rough-and-tumble sexual selection that goes on during elk mating season. But it turns out, there are some elk which have a genetic variation in their own not-a-disease prion protein. Elk that carry this genetic variant are more resistant to infection by CWD. They can carry the disease for longer without obvious symptoms, and they can go on to breed successfully.
In uninfected regions, this variation is rare. But for herds infected over a long period of time, evolutionary theory suggests that individuals who carry the variant—called the leucine allele—should have an selective advantage over individuals who go downhill fast when infected. And when a team from the Biological Resources Division of the National Park Service, working with the Wyoming Game and Fish Department went out to check, that’s exactly what they found.
Using genetic and disease samples from different populations, we found that elk herds infected with CWD for 30–50 y exhibited leucine allele frequencies that were twice as great as those in unexposed populations. Our results are consistent with the hypothesis that genetic selection has occurred due to CWD, but it remains unknown if this will allow elk to mitigate the negative population impacts of CWD.
Why is this my favorite story of the week? When we think about evolutionary pressure, we usually look at the effect of predators or the availability of prey. We think about the effects of a changing climate. But we rarely think about the way diseases alter populations. That genetic variant that makes elk more resistant to the disease? It may come paired with other genetic alterations. Even if it doesn’t, the deer population in areas with CDW may end up with a large population of animals who survive for years, maybe even their normal lifespans, without showing signs that they’re carrying the infectious prion.
And all of that leads to a possibility that’s both hopeful and terrifying. The deer population—elk, moose, white-tailed, mule deer, caribou—may ultimately survive the devastation of CWD by evolving to survive infection. But they will still be infected. Just asymptomatic. Raising the question of whether humans should eat any deer of any species, whether or not it shows signs of CWD.
If humans do get spongiform encephalopathy from CWD, there could even be a bigger long term evolutionary effect—one that could see the size of deer herds significantly expanded, or significantly reduced, depending on how humans react to that news.
Also of note: Look! Real scientists are still around at your National Park System. For now.
Very good dogs, 6000 BC edition
The archaeology column in Science features a fantastic image that was carved into a sandstone bluff in Saudi Arabia. Possibly dating back 8,000 years, the image shows a hunter equipped with a bow and arrow—and a nice pack of dogs. Whoever did the carving took the time to show different coat markings on many of the dogs. The body shape and markings on the dogs are suggestive of Canaan dogs.
They also show something that might seem odd in such an ancient image—a pair of leashes leading from two of the dogs to the hunter. The researchers indicate that the lines might actually be symbolic … but they certainly look like leashes.
There are 13 dogs in the picture. Which I’m interpreting as symbolic of the robust nature of the dogwalking economy in ancient Arabia.
Reducing gun violence in America
This one requires no translation—that’s the actual title of this paper in the Proceedings of the National Academy of Science. The author, from the Harris School of Public Policy, University of Chicago, looks at how one aspect of gun safety regulations shows what may seem like a small effect is really anything but.
In their new paper, Luca et al. argue that the adoption of mandatory waiting periods for handgun purchases reduces gun homicides by about 17%. These estimated effects are enormous. Most remarkable of all is that the policy intervention that leads to these reductions in gun violence would seem to impose so few costs on society. In what follows, I first try to put the magnitude of Luca et al.’s estimates into context to help readers appreciate how large they actually are.
The analysis suggests something that may seem both right and also hard to accept—almost all gun violence comes from people with “only transitory motivation.” That is violence like that we see like the shooting in Las Vegas is a rare exception. Most gun violence is of the “hell, he / she can’t do that to me, I’ll show him / her. Bang.” variety. In which case, programs aimed at making it harder to obtain a gun during the period of anger / fear could be highly effective.
Their analysis also raises a natural follow-up question: If these laws are so helpful, why do only 16 states have such policies currently in place? The answer seems due in part to what has been called the “collective action problem” that leads a small but highly motivated minority of the population to dominate the legislative process.
If you read this as meaning “We could really make some advances if the NRA didn’t f#$k everything up” then yeah, you got that right.
Cold fish are being done in by hot seas
Measurements show that, while the whole world is warming, some places are definitely warming faster. At the top of the charts: The Arctic. The rapidly melting ice in the far north has made the polar bear symbolic of ecosystems threatened by climate change, but another threatened system is right under those bears’ paws.
Arctic marine ecosystems are experiencing a rapid biogeographic change following the highest warming rates observed around the globe in recent decades. …
We find that large body-sized piscivorous and semipelagic boreal species are replacing small-bodied benthivorous Arctic species, likely affecting biomass production in the benthic and pelagic compartments and their coupling.
The not-a-fisheries-guy version of the above is that Arctic seas are warming quickly, and their populations are also making rapid changes. Small bottom-feeding fish that eat a mix of tiny sea-floor animals and marine snow are being replaced by larger, fish-eating species that tend to feed at other points in the water column. Which may not sound like a bad thing … except for that “likely affecting biomass” piece. The fish may be bigger, but the total biomass available is declining. So … more cod for your fish and chips for now, but ultimately less of everything because the base of the food chain is disrupted.
Plants plus fungus equals atmosphere
Most of the time I don’t mention the authors of these articles. That’s because scientific articles often involve a team of researchers and while someone may get top billing, that person is often there because of academic standing, not contribution to the specific work. But this time I’m putting the author in there, both because she’s a science writer rather than a researcher, and because she has a great name …
Amber Dance addresses a field that’s really exploded over the last few years—the interaction between plants and fungus.
Look at a plant, and you’re probably also looking at a fungus. More than 80% of land plants partner with fungi to help those plants extract nutrients—nitrogen and phosphorus—from the ground. The plants return the favor with carbon from their photosynthesis. Biologists suspect that this partnership was a major factor in allowing plants to move from water to land about 470 million years ago. But exactly how the partnership arose remains a mystery.
Dance goes on to explain how many different fungi can pair up with the same plant to help it tackle different conditions. And how the presence of land plants has been affected by and has affected the atmosphere—suggesting that if we screw up the CO2 content, some of the fungi will be very happy.
Immune boosting drugs don’t come without a cost
Drugs that boost some specific aspect of the immune system have become a key component of cancer treatments. Compared to the “nuke it all, let the strongest survive” approach of traditional chemotherapy and radiation, the more specific approach of drugs that entice some portion of the immune system into tracking down cancer cells can be—and is—enticing. On a personal note, my wife went through treatment for a non-Hodgkin’s lymphoma five years ago, and the availability of one such drug not only allowed her to skip radiation treatments, but raised the long-term survival rate on her particular form of cancer from 43 percent to over 90 percent. That’s a huge deal.
But such a big effect can’t always be purchased without risk. This week’s issue of Science includes information from Yale on how one class of drugs is apparently triggering autoimmune diseases in some cases.
Known as checkpoint inhibitors, these medicines rev up the immune system and are rescuing people from deadly cancers. Physicians such as Herold, are now seeing a nasty, if treatable, side effect: the rapid onset of conditions such as thyroid disease, colitis, and type 1 diabetes, which all result from the immune system’s attack on the body’s own tissues.
Axolotl on the brink
Though pronouncing its name may represent a significant challenge, the axolotl has long been a biological favorite. These large Mexican salamanders have a unique feature. Not only do they live their entire lives—including breeding and aging—while staying in what for most salamanders is the ‘immature’ form with big, feathery gills, they’re also subject to a startling transformation—give one an injection of iodine, and it turns into something that otherwise never exists: an “adult” axolotl … which looks remarkably like a tiger salamander.
Axolotls have been studied not just because they seem to live their lives as eternal infants, but because this extended preservation of immature features—known as neoteny—makes them aces as a very big trick. Axolotls can grow back entire severed limbs. Biologists have long recognized that a specific protein that the axolotls carry is part of that trick, but the rest of it … is hard to discover since axolotls have a genome that’s 10 times the size of the human genome. If that sounds strange, remember that the program for making potatoes is also significantly larger than the instructions for making humans. There’s a flower in Japan with a genome fully 50 times better than that of humans.
Big genomes don’t always signal either super complexity or super robustness. In fact, there appears to be some relationship between large genomes and species that have a hard time managing environmental changes. In the case of the axolotl, they turn out to be pretty robust—so robust, in fact, that odds are there are some to be found within a few miles of you. Not because they’re abundant in the wild. They’re just popular at aquarium shops.
But the native environment of the axolotl is restricted to a small area in Mexico, and there it’s not doing so well. There are only a few hundred animals in the wild, and they’re so genetically similar due to inbreeding that they may not make it even if everything goes perfect.
So there’s this weird conflict—axolotls are spectacularly common in pet shops and labs around the world—but the last ones living in their home waters are on the brink of extinction.
The Constitution as Societal DNA
While jurists debate whether or not the Constitution is a “living document,” in some sense it has to be. Constitutions set the design for societies, just as DNA defines an organism. And, as Amy Maxmen describes in Nature, both cases have mechanisms that allow for … evolution.
Amendments are generally introduced into a country’s constitution in a certain sequence, the authors report in a paper on the preprint server arXiv, and now under review at a journal. In addition, their computer analyses corroborate previously proposed ideas that the addition of some provisions is heavily influenced by the zeitgeist — the dominant social mores of the time — whereas the adoption of others reflects a country’s colonial history.
Some of what these constitutional clauses “code for” seems to have effects as complex as those represented by a gene. And the lockstep between society and constitution can be fascinating.
Some of the sequences were less straightforward: the right to form trade unions preceded laws against child labour, for example. This progression probably reflects the identities of the people who have traditionally scripted constitutions, says Rutherford. Adult men, for instance, seem to have considered their own protections before thinking about others, including those who were unable to push for their own rights, he says. “I think we should protect the most vulnerable first, but this paper says this is not how laws have progressed historically.”
In some sense then, the amendment mechanism represents the ability of the society-organism to adapt to changing conditions. Either those changes are inserted into the code that drives the current society or … they inform the next generation.
The Abbreviated Science Round-up seemed like a great opportunity to bring back the much-beloved infographics from the folks at Compound Interest which used to decorate the Sunday Abbreviated Pundit-Round up.
A larger, more detailed view of the image can be found by following this link.