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)
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”.