the National Science Foundation (NSF) : Boom times for fish populations in Wisconsin lakes .- Los tiempos de auge de las poblaciones de peces en los lagos de Wisconsin......

https://www.nsf.gov/discoveries/disc_summ.jsp?cntn_id=191382&WT.mc_id=USNSF_1


Research shows surprising conclusions about fish numbers

Bluegill in Wisconsin's Sparkling Lake show astonishing variability in numbers from year to year. Credit and Larger Version

March 30, 2017

Related stories on NSF's Long-Term Ecological Research Program are available online.

We're all familiar with the idea of extreme events. Meteorologists keep us up to date on hurricanes, floods and high temperatures. Economists watch the stock market for signs of crashes or rallies. Researchers spend a lot of time trying to better predict these events, yet are often surprised by the outcomes.

According to a new study in the journal Limnology & Oceanography Letters, when it comes to nature's extremes, nothing seems to beat what happens underwater.

Scientists at the National Science Foundation (NSF) North Temperate Lakes Long-Term Ecological Research (LTER) site -- one of 28 NSF LTER sites -- are routinely measuring everything from water temperature to nutrient concentrations to fish populations in Wisconsin lakes.

Taking advantage of several decades' worth of data, Ryan Batt, the paper's lead author, and a team of researchers compared data on various physical, chemical and biological variables -- 595 variables in total. They found that as the lakes' temperatures rose and their nutrient concentrations increased, so did the number of organisms living there.

The findings challenge preconceptions about what a "normal" distribution of averages and extremes looks like for the plants and animals in an ecosystem.

"Think of human height," says Batt, who is now at Rutgers University but conducted the study while at the University of Wisconsin-Madison's Center for Limnology. "If you saw someone walking around who was 14 feet tall, that would be insane. Even a single foot in height makes a huge difference in terms of being an outlier for what we would consider 'normal.'"

But, in the case of the populations of plants, fish and plankton living in lakes, that kind of outlier may not be unusual, according to Batt.

For example, in the three decades researchers have been tracking fish populations in Wisconsin's Lake Mendota, an average catch rate for bluegill, a popular and tasty fish, has been about five per hour of fishing.

But in 1983 and 2004, that catch rate was more than 30 per hour.

Research on nearby Lake Monona revealed similar extremes in the bluegill population. From 1995 to the early 2000s, bluegill numbers fluctuated between about 200,000 and 300,000. Then, in 2002, that estimate spiked to 500,000, nearly doubling the previous high mark. Three years after that, it topped out at around 800,000.

"We tend to look at extreme events in the environment in a negative way," Batt says. "Like there's a heat wave and a bunch of fish die. Or there's a cold snap and a bunch of fish die. People usually think of the environment as having extremes that are lethal."

Steve Carpenter, director of the UW-Madison Center for Limnology and a co-author of the study, at one time thought that biology would produce fewer extremes. But through long-term research, he learned otherwise.

"There are new records being set all the time," he says. "For physical and chemical variables, you may have to wait a long time to see a new record, then the new record isn't all that shocking. But often you don't have to wait all that long for a biological variable to set a record, and that new record can be, 'Wow, that's more yellow perch than we ever saw before. By a lot.'"

Data collected over long periods of time help researchers identify extremes that are less obvious, says NSF LTER program director John Schade.

"Extreme increases in populations of organisms are hard to predict, and can have significant consequences for human well-being and for the ecosystem services we all depend on," Schade says. "This work demonstrates just how fast, big, and common these increases can be. Without long-term research, we could not understand the causes and consequences of these extreme events."

In their paper, the authors propose one mechanism driving the increase in fish populations. Organisms may be primed to take advantage of good conditions. Years that saw unprecedented booms in fish or algae populations could signify a corresponding bump in environmental conditions like water temperatures and the availability of nutrients.

Since human activity affects climate change, habitat loss, nutrient pollution and other environmental variables, says Carpenter, society should prepare, seeking to better understand what those changes mean for different ecosystems.

With the variability this study uncovered, Carpenter says, it's challenging to determine what "normal" population levels might be. "We need to be prepared to see new records," he says.

It's not enough to just expect the unexpected, says Carpenter. "We also need to be ready for the unprecedented."

--	Cheryl Dybas, NSF (703) 292-7734   cdybas@nsf.gov
--	Adam Hinterthuer, University of Wisconsin-Madison (608) 890-2137   hinterthuer@wisc.edu

Investigators Adena Rissman
Corinna Gries
Emily Stanley
Monica Turner
Timothy Kratz
Steven Loheide
Stephen Carpenter
Jake Vander Zanden
Christopher Kucharik

Related Institutions/Organizations University of Wisconsin-Madison
Related Awards #1440297 LTER: Comparative Study of a Suite of Lakes in Wisconsin
#1038759 WSC Category-2: Climate Change, Shifting Land Use, and Urbanization in a Midwestern Agricultural Landscape: Challenges for Water Quality and Quantity
Total Grants $8,924,612
Related WebsitesNSF LTER Network:
 https://lternet.edu/
NSF North Temperate Lakes LTER Site:
 https://lter.limnology.wisc.edu/
NSF LTER Discovery Articles:
 https://www.nsf.gov/news/newsmedia/ENV-discoveries/LTER-discovery-series.jsp
 
Researchers sample fish in lakes by dark of night; the results help with population estimates.
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Even in winter, scientists are out taking samples at the NSF LTER site on Wisconsin lakes.
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Scientist Ryan Batt obtains readings of oxygen levels in a lake in northern Wisconsin.
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Researchers census fish populations in lakes in Wisconsin. Seen here, a common carp.
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Ryan Batt rows out to collect minnow traps in a northern Wisconsin lake.
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the National Science Foundation (NSF)
Guillermo Gonzalo Sánchez Achutegui
ayabaca@gmail.com
ayabaca@hotmail.com
ayabaca@yahoo.com
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nsf.gov - Discovery - Clarity for lake researchers' water quality questions

Studies of trends in Midwestern lakes benefit from help of local residents

The discovery is the first report of a virus carrying genes for sulfur oxidation. Credit and Larger Version

May 1, 2014

Scientists engaged in a study of long-term water quality trends in Midwestern lakes found some good news: little change in water clarity in more than 3,000 lakes.

Look deeper, and the research becomes something more: a chronicle of a new source of data for scientists, data from residents of towns and villages surrounding the lakes.

The results are published this week in a paper in the journal PLOS ONE.

The paper co-authors analyzed almost a quarter of a million observations taken over seven decades on 3,251 lakes in eight Midwestern states.

 

Enter local residents

But the researchers didn't collect those data. The observations came from lakefront homeowners, boaters, anglers and other interested members of the public wanting to know more about what's going on in "their" lakes.

Noah Lottig, a co-author of the paper and a scientist at the University of Wisconsin-Madison's Center for Limnology, says that ecologists are looking at big-picture issues--such as how changes in land use or climate affect ecosystems--at state, national and continental scales.

This time, the help of local residents was key to the findings.

"This study highlights research opportunities using data collected by citizens making important environmental measurements," says Elizabeth Blood, program director in the National Science Foundation's (NSF) Directorate for Biological Sciences, which funded the work through its MacroSystems Biology Program. "Their efforts provide scientists with data at space and time scales often not available by other means."

 

Water clarity from a Secchi disk reading--or tens of thousands of them

Lottig and freshwater scientists from across the United States combed through state agency records and online databases. The water clarity measurements they sought were taken by non-scientists using a circular, plate-sized instrument called a Secchi disk.

Used in the aquatic sciences since the mid-1800s, Secchi disks hang from a rope and are lowered into the water until their distinct black-and-white pattern disappears from view, a distance that marks the "Secchi depth."

Lake associations and other groups have used the disks for decades to document conditions in their respective waters.

Previous studies have shown that local residents' Secchi readings are nearly as accurate as scientists' measurements, says Lottig.

With a dataset covering more than 3,000 lakes and stretching back to the late 1930s, the team decided to ask questions about long-term change.

 

Before and after the Clean Water Act

The Clean Water Act provided a useful frame of reference. Signed into law in 1972, the act set water quality goals for all U.S. waters.

Thanks to the data collected by residents, Lottig's team had access to water clarity measurements for decades before and after the act came into effect.

Somewhere in that data, the researchers reasoned, they might detect a landscape-scale shift over time to clearer (often an indicator of cleaner) water.

While there was a slight one percent yearly increase in water clarity for the lakes, Lottig says, "most of the lakes are just chugging along, not changing much through time."

While some lakes improved, others did not. Taken as a whole, there was no major change in clarity at the landscape scale.

Lottig is part of the "Cross-Scale Interaction" or "CSI Limnology" project, an effort to collect global data on water chemistry and aquatic biology that will add needed context.

 

Townspeople weigh in

For Ken Fiske, collecting data has been well worth the effort.

In 1985, Fiske saw an announcement for volunteers for a new Wisconsin lake monitoring program. Fiske had been coming to northern Wisconsin from his home in Illinois for years and had recently bought property on the shoreline of Lake Adelaide.

"My interest was in finding out what the quality of water in Lake Adelaide was and seeing what we could do to maintain it," he says.

For the next several years, Fiske went on a monthly five-hour drive to Lake Adelaide to take measurements. Eventually, he found some neighbors to help. Some 30 years later, the group is still going strong.

"We've been doing it long enough that it makes the results meaningful," Fiske says.

Scientists are harnessing efforts like Fiske's to try to answer questions about not just one lake, but 3,251--or more--of them.

--	Cheryl Dybas, NSF (703) 292-7734   cdybas@nsf.gov
--	Adam Hinterthuer, University of Wisconsin - Madison (608) 890-2187   hinterthuer@wisc.edu

Investigators Noah Lottig
Emily Stanley

Related Institutions/Organizations University of Wisconsin-Madison

Related Awards#1065818 Collaborative Research: The Effects of Cross-Scale Interactions on Freshwater Ecosystem State Across Space and Time

Total Grants $591,461

Scientists measure the water's transparency in Lake Mendota, Wisc.
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Underwater view of a Secchi disk, used to measure water clarity, dropping through the water column.
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Scientist teaching area residents the best ways to monitor water quality in lakes.
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Children learn how to measure water quality with a Secchi disk.
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Algae blooms in Wisconsin's Lake Mendota are being monitored from the air and from the ground.
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The National Science Foundation (NSF)

Guillermo Gonzalo Sánchez Achutegui

ayabaca@gmail.com

ayabaca@hotmail.com

ayabaca@yahoo.com

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