Subscribe to our free daily newsletters
. Earth Science News .

Subscribe to our free daily newsletters

'Resurrecting' tiny lake lifeforms to study evolutionary responses to pollution
by Staff Writers
Ann Arbor MI (SPX) Feb 17, 2017

Microscope image of a 4-day-old Daphnia ambigua crustacean, like those used in a new study of evolutionary responses to heavy-metal contamination in lakes. Image courtesy Eric Lazo-Wasem.

A University of Michigan biologist combined the techniques of "resurrection ecology" with the study of dated lake sediments to examine evolutionary responses to heavy-metal contamination over the past 75 years. To accomplish this, Mary Rogalski hatched long-dormant eggs of Daphnia, tiny freshwater crustaceans also known as water fleas, that accumulated in the lake sediments over time.

After rearing the critters in the lab, she exposed them to various levels of two heavy metals to see how their sensitivity to the environmental contaminants changed over time. Surprisingly, she found that sensitivity to copper and cadmium increased as the levels of those toxic metals rose in the lakes she studied.

"These findings are unexpected because evolutionary theory predicts that a population should adapt quickly to a stressor like this and become less sensitive to it, not more sensitive to it. It is difficult to explain the results of this study," said Rogalski, a postdoctoral researcher in the U-M Department of Ecology and Evolutionary Biology.

In one of the lakes, Daphnia hatched from sediments dating to around 1990 - when copper contamination was at its peak - were 46 percent more sensitive to copper exposure than individuals from the 1940s, a period with lower levels of copper contamination.

Rogalski reports her finding in a study published online Feb. 16 in the journal The American Naturalist. The study was part of her dissertation research at the Yale University School of Forestry and Environmental Studies and involved fieldwork at three Connecticut lakes.

Scuba divers collected 5-inch-diameter sediment cores from the lake bottoms. Rogalski then estimated sediment ages based on the presence of radioactive materials and measured concentrations of copper and cadmium in the layers back to the late 1800s.

Copper contamination in the lakes was largely due to yearly applications of copper sulfate to control nuisance algae. The cadmium likely came from industrial and agricultural development in the region over the past century.

In the lab, Rogalski isolated dormant or "diapausing" Daphnia ambigua eggs from various dated sediment layers, then hatched and raised them. She measured Daphnia's changing sensitivity to copper and cadmium by exposing them to various levels of the metals in glass flasks and determining the median lethal concentration.

In one Connecticut lake where copper contamination has declined recently, she found that Daphnia remain sensitive to the metal 30 years after peak exposure. An adult Daphnia is about the size of a very coarse grain of sand.

"It is difficult to know what mechanisms are driving this evolutionary pattern," Rogalski said. "Even so, this research suggests that we need to do more to uncover both the drivers and implications of maladaptation in nature."

Paleolimnology is the study of ancient lakes from their sediments and fossils. The branch of experimental paleolimnology that Rogalski used in this study has been dubbed "resurrection ecology" by its practitioners.

Human activities can drive strong and rapid evolutionary changes in wild animal populations. Those evolutionary responses often leave the population better able to cope with the new environmental conditions, a process called adaptation through natural selection.

For example, a newly introduced pesticide may kill the vast majority of the insects it targets. But the survivors can then give rise to a pest population that is resistant to the chemical.

But some populations fail to adapt to changing environments or can wind up worse off than they were beforehand, an occurrence known as maladaptation.

Maladaptive outcomes are less common than adaptive one and are less studied. In many cases, it is impossible to examine a population's response to a stressor over multigenerational timescales without conducting a long-term study that could take decades to complete.

The Daphnia crustacean, with its diapausing eggs, provides a time machine of sorts, allowing researchers to examine long-term evolutionary responses to environmental stressors by reviving and rearing dormant organisms trapped in lake bottoms.

"Daphnia offer a system where examining historic evolutionary trajectories is possible," Rogalski wrote in The American Naturalist. "Hatching diapausing eggs from dated lake sediments and culturing clonal lineages in the lab allows us to examine how populations change through time and the genetic basis underlying those changes."

Comment on this article using your Disqus, Facebook, Google or Twitter login.

Thanks for being here;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.

SpaceDaily Contributor
$5 Billed Once

credit card or paypal
SpaceDaily Monthly Supporter
$5 Billed Monthly

paypal only


Related Links
University of Michigan
Our Polluted World and Cleaning It Up

Share this article via these popular social media networks DiggDigg RedditReddit GoogleGoogle

Previous Report
Miners protest Philippine plan to cancel 75 contracts
Manila (AFP) Feb 15, 2017
Mining firms in the Philippines voiced outrage Wednesday over government plans to cancel nearly one quarter of the nation's contracts, plus a permit to exploit one of the world's largest known copper deposits. Environment Secretary Gina Lopez announced Tuesday she would cancel 75 of the nation's 311 mining contracts, as well as the environmental compliance certificate of the planned $5.9-bi ... read more

Bringing satellites to users can improve public health and safety

Free hairdos to boost confidence of displaced Iraqi women

'Scorpion' robot mission inside Fukushima reactor aborted

Myanmar jade mine landslide kills 9: official

Terahertz chips a new way of seeing through matter

Cooling roofs and other structures with no energy

Researchers engineer thubber a stretchable rubber that packs a thermal conductive punch

Penn researchers are among the first to grow a versatile 2-dimensional material

Ethiopia dam causes Kenya water shortage: rights group

10 Italian execs found guilty over polluted water supply

Seagrass on decline, jeopardizing human, coral health: study

El Nino resulted in unprecedented erosion of the Pacific coastline

How an Ice Age paradox could inform sea level rise predictions

Sentinels warn of dangerous ice crack

Sea ice at poles hit record low for January

Arctic cultures take climate fight to Berlin film fest

Nicaragua focuses on climate-change resistant coffee

Gluten-free diet may increase risk of arsenic, mercury exposure

Study rewrites the history of corn in corn country

Mongolia herders reel under dreaded 'dzud' weather

Italy asks EU aid as cost of quakes hits 23 bn euros

Cyclone bears down on Mozambique coast

Ventura fault could cause stronger shaking

Researchers catch extreme waves with higher-resolution modeling

Interim authorities to begin work in Mali's north

UN demands armed groups stop fighting in C. Africa

S. Sudan army says general who quit was 'deeply' corrupt

Ivory Coast arrests six journalists over mutiny 'false information'

Study links working remotely to more stress, insomnia

Study: The human brain always has a backup plan

Chimpanzee feet allow scientists a new grasp on human foot evolution

Humans subconsciously perceive words as 'round' or 'sharp'

Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News

The content herein, unless otherwise known to be public domain, are Copyright 1995-2017 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement