From York University – quite possibly the most poorly written science by press release I’ve seen this year. The leaps of “may” are profound, and the footbal team analogy is designed to elicit sympathy. I suppose if Daphnia populations were collapsing in lakes due to lack of helmets and shoulder pads, we’d see a collapse in the lake food chain too, but that doesn’t seem to be happening that I can find. And, as is typical with such alarmist press releases, they don’t name the paper, making anyone reading the press release have to go hunting for it.
Changes in water chemistry leave lake critters defenseless
TORONTO, Sept. 6, 2012 – Imagine that the players on your favourite football team were smaller than their opponents, and had to play without helmets or pads. Left defenseless, they would become easy prey for other teams. Similarly, changes in Canadian lake water chemistry have left small water organisms vulnerable to their predators, which may pose a serious environmental threat, according to a new study.
“At low calcium levels the organisms grow slower and cannot build their armour,” says study lead author Howard Riessen, professor of biology, SUNY College at Buffalo. “Without suitable armour, they are vulnerable to ambush by predators,” he says.
Riessen and colleagues, including York University biology Professor Norman Yan, studied the effect of changes in water chemistry on plankton prey defenses. Specifically, they examined how lower calcium concentrations affect
(water flea) exoskeleton development. These low calcium levels are caused by loss of calcium from forest soils, a consequence of decades of acid rain and multiple cycles of logging and forest growth. The results are published this week in the Proceedings of the National Academy of Sciences.
“Calcium is a critical element for Daphnia and many other crustaceans,” Riessen says. “Daphnia build their exoskeletons, which include some defensive spines, with calcium to protect themselves from predators. Where calcium levels are low, the Daphnia have softer, smaller, exoskeletons with fewer defensive spines, making them an easy snack.”
Why do plankton matter? Yan, the study’s senior author and a Fellow of the Royal Society of Canada, emphasizes that the tiny creatures are critical to our survival. “Without plankton, humans would be quite hungry, and perhaps even dead. Much of the world’s photosynthesis, the basis of all of our food, comes from the ocean’s plankton. The oxygen in every other breath we take is a product of phytoplankton photosynthesis,” says Yan.
This phenomenon of reduced calcium is also playing out on a much larger scale in the world’s oceans, he notes. “Increases in ocean acidity are complicating calcium acquisition by marine life, which is an under-reported effect of global carbon dioxide emissions. Thus marine plankton may also find themselves more vulnerable to predators,” he says.
The public is used to stories about changes in water chemistry that lead to large-scale fish kills, says Riessen. “These changes are more insidious. Daphnia might not be a household name, but they are food for fish, and they help keep our lakes clean. Changing the balance between Daphnia and their predators marks a major change in lake systems.”
So I found the paper, and sure enough, they don’t mention the oceans (in the abstract). Seems like they went a bit overboard with that press release.
Changes in water chemistry can disable plankton prey defenses
- Howard P. Riessena,1,
- Robert Dallas Linleyb,c,
- Ianina Altshulerd,
- Max Rabuse,
- Thomas Söllradlf,
- Hauke Clausen-Schaumannf,g,
- Christian Laforsche,h,2, and
- Norman D. Yanb,c
+ Author Affiliations
aDepartment of Biology, State University of New York (SUNY) College at Buffalo, Buffalo, NY 14222;
bDepartment of Biology, York University, Toronto, ON, Canada M3J 1P3;
cDorset Environmental Science Centre, Dorset, ON, Canada P0A 1E0;
dDepartment of Biological Sciences, University of Windsor, Windsor, ON, Canada N9B 3P4;
eDepartment Biologie II, Ludwig Maximilians Universität München, 82152 Planegg-Martinsried, Germany;
fDepartment of Precision- and Micro-Engineering, Engineering Physics, Munich University of Applied Sciences, 80335 Munich, Germany;
gCenter for NanoScience, Ludwig Maximilians Universität München, 80539 Munich, Germany; and
hGeoBio Center, Ludwig Maximilians Universität München, 80333 Munich, Germany
-
Edited by Michael Lynch, Indiana University, Bloomington, IN, and approved August 9, 2012 (received for review June 11, 2012)
Abstract
The effectiveness of antipredator defenses is greatly influenced by the environment in which an organism lives. In aquatic ecosystems, the chemical composition of the water itself may play an important role in the outcome of predator–prey interactions by altering the ability of prey to detect predators or to implement defensive responses once the predator’s presence is perceived. Here, we demonstrate that low calcium concentrations (<1.5 mg/L) that are found in many softwater lakes and ponds disable the ability of the water flea, Daphnia pulex to respond effectively to its predator, larvae of the phantom midge, Chaoborus americanus. This low-calcium environment prevents development of the prey’s normal array of induced defenses, which include an increase in body size, formation of neck spines, and strengthening of the carapace. We estimate that this inability to access these otherwise effective defenses results in a 50–186% increase in the vulnerability of the smaller juvenile instars of Daphnia, the stages most susceptible to Chaoborus predation. Such a change likely contributes to the observed lack of success of daphniids in most low-calcium freshwater environments, and will speed the loss of these important zooplankton in lakes where calcium levels are in decline.
===============================================================
In comments, Rat boy (who apparently has paid access) points out this last paragraph of the paper where they DO mention the oceans in passing, with more “may” caveats:
Marine plankton also face the prospect of reduced calcification,
in this case as an indirect consequence of ever increasing
concentrations of CO2 in the oceans (37, 38). Much like their
freshwater counterparts, many marine plankton also may find
themselves increasingly vulnerable to a variety of predators.
Thus, the indirect effect of changes in water chemistry on
predator–prey interactions in both freshwater and marine communities may play an important role in determining the ultimate success of species in these environments.
The point stands, they use “may” in the broadest sense in that paragraph to make that leap of logic, without any supporting science to back it up. If they had any supporting science, they wouldn’t use the word “may”.
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Where I grew up we had very large puddles after the standard rainfall in summer. Of course we tons of those water fleas, and also mosquito larva. However, we also had some toads living in the bushes and they always laid their eggs in the same massive puddles. So the tadpoles ate all the water fleas and larva.
Using the logic from this paper I must say that the tadpoles eating all the water fleas back then was certainly a result of global warming.
Something tells me we have more of a louse problem.
just as ridiculous, given the fantastic snow season Australians are enjoying this year:
8 Sept: Sydney Morning Herald: Jacqueline Maley: Great season but climate change brings snow blindness
THE ski bunnies, the electro-engineers and the resort operators all agree on one thing: 2012 is the best season in the Snowy Mountains for a long time.
According to the levels measured by Snowy Hydro, the snow was 204 centimetres deep on August 30, which is as deep as it has been since 2004.
Some say the quality and consistency of the snow is as good as it was in the famous 2000 season. Others mutter about 1990. Thredbo resort is so excited it has extended its season until next month.
What they can’t agree on is how long it will last.
Advertisement While climate scientists predict Australian ski seasons in future will have scantily clad slopes, the ski resorts prefer to focus on the here and now, while hedging their bets with technology that maximises the snow they have, for however long they have it….
But nature will have its way, at least according to climate scientists.
The CSIRO predicts that compared with 1990 levels, there will be 60 per cent less snow on the slopes by 2020, under a high emissions scenario, which is what we’re tracking towards.
”Resorts, national parks and local government researchers have all moved on from ‘Is it happening?’ to ‘How do we deal with it?’,” says Catherine Pickering, a climate scientist and associate professor at Griffith University.
When asked about Thredbo resort’s contingency plans for climate change, the communications manager, Susie Diver, says that snow, just like rainfall, ”goes up and down”…
Elliss says the business operators and resort personnel in the area err on the conservative side when it comes to climate change thinking.
”I think they would like to believe the sceptics, but it’s pretty bloody obvious to me,” he says. ”It’s real. You can be in denial about it all you want.”
http://www.smh.com.au/environment/weather/great-season-but-climate-change-brings-snow-blindness-20120907-25jno.html
So they are worried about oceanic phytoplankton, but Daphnia are freshwater zooplankton. The predator mentioned in the abstract (phantom midge) lives almost exclusivley in fishless lakes, but they point out that Daphnia are important because they are fish food. So, basically they are worried because they forgot what their study actually covered.
I think the casual reader might wonder, “If these organisms are supposed to be food for predators, then why is it bad that they’re more vulnerable to predators?”
Umm, last paragraph of the paper:
REPLY: Umm, the public can’t read the paper without paying for it. That’s part of the issue. I tried to read the full paper and was faced with paying for it:
http://www.pnas.org/content/early/2012/08/29/1209938109.full.pdf+html
I take it you, as one of the anointed academics, didn’t have to pay to read the paper due to your university affiliation?
The point stands, they use “may” in the broadest sense in that paragraph to make that leap of logic, without any supporting science to back it up. If they had any supporting science, they wouldn’t use the word “may”. If the situation were reversed, you’d be all over it. – Anthony
“York University” in downtown Toronto – the centre of the Universe. Click on the link Anthony gave you in the first line and see if you think you want to take what they say seriously. If it came from McGill, or Waterloo, or Dartmouth or U of S or U of C or U of A…. But York? Nothing new. Move along. Check out the University News: http://www.yorku.ca/web/index.htm
Daphnia are a rather interesting creature in that they clone themselves. The egg sacks, which are located on the right of the picture are exact genetic duplicates of the mother. After the first instar the new Daphnia can squirt out more clones. This allows rapid response to incoming nutrient load. Sex takes too much time and energy.
One of the main predators of Daphnia is fish. Fish don’t care about the size of the hood or any other body part. They process Dphnia by filter feeding. Sockeye are especially efficient at filter feeding because of the close proximity of their gill rackers.
York U is not downtown but out in the NW part of the city. But their leftist thinking infests most of the politics in this province. Feel free to substitute a “D” for “Y” and you’ll get what many people call the U.
The Daphnia are the extreme “canary in a coal mine” and will die if you blink at them. The Antismokers have been using them for years with a cute little experiment involving a cigarette butt in a liter of water. OMG! It kills HALF the Daphnia! Smokers are POISONING THE WORLD’S WATER ‘n WE”RE ALL GONNA DIIIIEEEEEEEEE!!!!!!
Eventually I got tired of the nonsense so I divided the 5 trillion possible butts a year ALL being thrown into the world’s water into the 1.3 SEXTILLION liters of water and determined that the smokers could smoke their hearts out and litter at will for the next 80 million years… even assuming zero biodegradability.
Take their figures and claims and compare it to the world’s water supply and for this stuff and you might be able to give them a black eye or two.
– MJM
Daphnia are a very important food source for freshly hatched fish and are the main source of food throughout the winter for many fish species. Examination of stomach content of rainbow trout during the winter shows 100% of the food is Dahnia. This has been observed in some of our Western lakes that have very large population of Daphnia pulex.
It seems we need to put Daphnia on the threatened species list, just like their brother polar bears. (sarc)
One technical point. Wouldn’t acid rain actually increase the calcium in the lakes due to runoff as the rain weathers surrounding limestone and other calcium bearing formations? Just asking.
When you use “may” at the end of a scientific paper it’s because you are suggesting possibilities that ought to be followed up. Do you think scientists should never be allowed to conjecture?
You know, the scientists don’t like that you can’t read the article either. PNAS charges authors $1350 to make the article open access. That’s cheap compared to Nature ($5000). If you email a study author they will be happy to send you a free copy.
I also think it makes sense to think about the “may” scenarios BEFORE there is a collapse in lake food chains… “We’re not all dead yet, so this is uninteresting” is a fairly extreme definition of what’s worth studying/reading about.
I’ve read about daphnia being “farmed” in tanks paired with heavily planted aquariums. The water is shared, so the daphnia farm gets the algae from the other tank. Heavily planted tanks are often supplemented with CO2 — sometimes to the level that the CO2 injection has to be shut off overnight or it would kill the fish — yet daphnia thrive in this environment.
At least until they’re scooped out of their isolated tank and put in the main tank with the fish. Then they become fish food.
“…low calcium levels are caused by loss of calcium from forest soils…” & it should be noted that leaves on the ground are what adds calcium back into the equation. Temperate tree varieties deposit different levels of leaf calcium; some examples are of 22.4 mg Ca/gr leaf litter from hardwood Tilia cordata to just 3.7mg Ca/g from evergreen Pinus nigra. (for data comparing 14 tree leaf litter see http://mx1.boulderlake.org/worms/downloads/publications/Reich%20et%20al.%202005.PDF)
May is used correctly in the paper – as a potential extension of the paper’s freshwater findings that require validation. Since you aren’t attacking the freshwater conclusions do you believe that low calcium levels is salt water do not affect animals that build their shells from calcium?
The assumption that low calcium levels make it harder for animals to build shells out of calcium and that weaker shells leave the animals more vulnerable seems pretty reasonable to me whether or not NaCl is present.
oeman50 says:
September 7, 2012 at 8:55 am
Of course calcium increases as pH decreases. Freshman high school chemistry.
Another chuckle in this academic “puff-piece” (I would not elevate this to a “paper”), is the weakening of the “armor” of the Daphnia. Armor does not do that well when one is swallowed whole, as the overwhelming majority are. For evasion, then, evolution “science” predicts that, for survival, they should have lighter “armor” for faster speeds. This “paper” is a mish-mash of competing and contradictory ideas.
Oh, another thing: notice how these guys always pick an anthropomorphically “cute” organism? It sort of looks like a chicken peep with little tickley wings? Why not pick a Volvox which is just a big prickly ball, or one of the planckton species that look like silverfish or a cockroaches?
Rhetorical question—you know why…
I do research on freshwater food chains and know Harry Reissen and Norm Yan personally. I didn’t see the press release on the York U web site. Seems like a good piece of science and congrats to the authors for getting published in PNAS.. We know that Daphnia doesn’t do well in soft, low Ca++ water and that seems to be a direct results of water chemistry (low Ca++) and an indirect result of less ability to invest in physical defenses. These are interesting science results. If there is a problem, it’s the journalists at universities who interview the scientists and write the “press releases.” Phantom midge larvae (Chaoborus) are major plankton predators, especially in lakes with few fish, which is often the case in low pH or acid lakes. Reissen has spent much of his career studying the predator prey interactions between Daphnia and Chaoborus. It’s a great system for basic research on these interactions. Since one can do lab and field experiments with Daphnia and Chaoborus, scientists can develop mathematic models and test the predictions of the models with experiments.
@socialblunder – if they had observed it in the North Atlantic and said that it “may” be taking place worldwide the same objection, a “leap of logic” with “no scientific evidence to back it up” would probably be leveled…
Edohiguma says: September 7, 2012 at 7:43 am
… So the tadpoles ate all the water fleas and larva.
Using the logic from this paper I must say that the tadpoles eating all the water fleas back then was certainly a result of global warming.
I thought tadpoles were vegetarians?
Mmmmm, how can we include “CO2” in our paper to secure those grants…
More garbage science equals more garbage. Tiny amounts of CO2 only change the bicarbonate ion equation in a miniscule degree. Ocean life merely changes the equation back in the other direction in a much larger and faster degree. Life EATS C02 and eventually deposits excess CO2 on the ocean floor.
Problem solved as it always has been since ocean life evolved. More straining at gnats by those with an agenda.
There is virtually no calcium in the fresh water bodies of the entire country of Scotland (which makes it such a great place to live — you don’t need to buy bottled water there). Daphnia are doing just fine. Ten milligrams per litre seems to be more than enough.
PNAS is one of the hardest journals there is to get published in. But (presumably, I doubt there has been enough time since the post went up) without reading the article bubbagyro can tell it’s a “puff piece”.
I personally would generally assume that PNAS can probably find reviewers that could tell if the whole premise of the paper is wrong.
@gene selkov – that’s great, but what about at the concentrations listed in the abstract?
Here, we demonstrate that low calcium concentrations (<1.5 mg/L) that are found in many softwater lakes and ponds disable the ability of the water flea, Daphnia pulex to respond effectively to its predator, larvae of the phantom midge, Chaoborus americanus.
And for everyone that mentioned fish eating them whole, note what it says the main predator is…