Nav: Home

Forget 'needle in a haystack'; try finding an invasive species in a lake

December 04, 2018

MADISON, Wis. -- When the tiny and invasive spiny water flea began appearing in University of Wisconsin-Madison researchers' nets in 2009, scientists began to wonder how Lake Mendota, one of the most-studied lakes in the world, went from flea-free to infested seemingly overnight. Subsequent studies found the invader had persisted for years at low population densities that went undetected even as the lake was routinely sampled by trained technicians.

Now a new report published in the journal Ecosphere says Lake Mendota's story may be the rule, rather than an exception.

"Our original idea was (to ask): 'How is this possible? In what scenario would we miss spiny water flea for 10 years, even after so much effort?'" says Jake Walsh, lead author of the study and a postdoctoral researcher at the UW-Madison Center for Limnology.

The answer is that completely missing a species "is not only possible, it's likely," says Walsh, noting that the study can help inform invasive species ecology and is a "way of using math and computer modeling to fill in the blanks of what we see."

With Center for Limnology director Jake Vander Zanden and Eric Pedersen, a colleague from Fisheries and Oceans Canada, Walsh developed a theory of the probability of detecting a species as its population densities change.

Their modeling shows that when species are in low abundance in a given habitat, the ability for scientists to detect them drops off precipitously.

This may explain why spiny water fleas passed undetected in Lake Mendota for a decade. Early on, researchers would have needed to dip their nets into the lake "hundreds or even thousands" of times, Walsh says. Once the invaders became more abundant, detection became much easier: "You can go out sampling three times and likely detect spiny water fleas."

Part of the problem is size. Even if there was one spiny water flea for every cubic meter of water in Lake Mendota, catching one in a net would be like finding a sesame seed in roughly 250 gallons of water.

One of the solutions, the study shows, may be for scientists to increase the size of the funnel-shaped plankton nets they drag through the water when looking for the small creature. Standard nets are roughly a foot in diameter, but by upgrading to a one-meter-wide net (about three feet in diameter), "your detection increases by quite a bit," Walsh says.

Being more deliberate about sampling for spiny water fleas and other invasives at the right places and times may also improve scientists' chance for detection, Walsh says. Spiny water fleas are a type of zooplankton (small, free-floating crustaceans) that travel in groups called swarms and are pushed around by wind and currents. A swarm may move at any time out of any given sampling site. And their abundances vary throughout the year. For instance, spiny water fleas are present in the greatest numbers in Lake Mendota in the fall.

"If you were to double your effort at sampling for spinies in the fall," Walsh says, "you get the same advantage as if you were to double your effort across the entire year."

The study offers some "basic rules of thumb" for designing species surveillance programs of any kind -- from likely invasives to rare or endangered natives, Walsh says.

"It has to do with targeting our efforts better and finding times of the year where things are more abundant or areas where they're more abundant because that dramatically increases your detection rate," he says. "If you take a little extra time to get to know the species you're looking for, it can really pay off."
-end-
--Adam Hinterthuer, hinterthuer@wisc.edu, 608-630-5737

DOWNLOAD PHOTOS: https://uwmadison.box.com/v/spiny

University of Wisconsin-Madison

Related Water Articles:

Source water key to bacterial water safety in remote Northern Australia
In the wet-dry topics of Australia, drinking water in remote communities is often sourced from groundwater bores.
Our water cycle diagrams give a false sense of water security
Pictures of the earth's water cycle used in education and research throughout the world are in urgent need of updating to show the effects of human interference, according to new analysis by an international team of hydrology experts.
Water management helped by mathematical model of fresh water lenses
In this paper, the homeostasis of water lenses was explained as an intricate interaction of the following physical factors: infiltration to the lens from occasional (sporadic) rains, permanent evaporation from the water table, buoyancy due to a density contrast of the fresh and saline water, and the force of resistance to water motion from the dune sand.
The age of water
Groundwater in Egypt's aquifers may be as much as 200,000 years old and that's important to know as officials in that country seek to increasing the use of groundwater, especially in the Eastern Desert, to mitigate growing water stress and allow for agricultural projects.
Water that never freezes
Can water reach minus 263 degrees Celsius without turning into ice?
Peanuts that do more with less water
Researchers are studying peanut varieties to find a 'water conservation' trait.
Molecular adlayer produced by dissolving water-insoluble nanographene in water
Even though nanographene is insoluble in water and organic solvents, Kumamoto University and Tokyo Institute of Technology researchers have found a way to dissolve it in water.
Water-worlds are common: Exoplanets may contain vast amounts of water
Scientists have shown that water is likely to be a major component of those exoplanets (planets orbiting other stars) which are between two to four times the size of Earth.
Artificial intelligence saves water for water users associations
A research group at the University of Cordoba has developed a model based on artificial intelligence techniques that can predict how much water each water user will use.
In desert trials, next-generation water harvester delivers fresh water from air
UC Berkeley scientists who last year built a prototype harvester to extract water from the air using only the power of the sun have scaled up the device to see how much water they can capture in arid conditions in Arizona.
More Water News and Water Current Events

Top Science Podcasts

We have hand picked the top science podcasts of 2019.
Now Playing: TED Radio Hour

Accessing Better Health
Essential health care is a right, not a privilege ... or is it? This hour, TED speakers explore how we can give everyone access to a healthier way of life, despite who you are or where you live. Guests include physician Raj Panjabi, former NYC health commissioner Mary Bassett, researcher Michael Hendryx, and neuroscientist Rachel Wurzman.
Now Playing: Science for the People

#543 Give a Nerd a Gift
Yup, you guessed it... it's Science for the People's annual holiday episode that helps you figure out what sciency books and gifts to get that special nerd on your list. Or maybe you're looking to build up your reading list for the holiday break and a geeky Christmas sweater to wear to an upcoming party. Returning are pop-science power-readers John Dupuis and Joanne Manaster to dish on the best science books they read this past year. And Rachelle Saunders and Bethany Brookshire squee in delight over some truly delightful science-themed non-book objects for those whose bookshelves are already full. Since...
Now Playing: Radiolab

An Announcement from Radiolab