Stroud Scientists at Work Stroud Research Sheds New Light on the Impact of Temperature Change in Large Rivers PPL Corporation, an energy company that operates power plants in the Northeast and Northwest, recently funded a first-of-its-kind, site-specific research study to simulate the effects — and understand the impact — of rapid daily changes of temperature in the Susquehanna River on its fish and macroinvertebrate populations. The study, which was conducted by the Stroud™ Water Research Center, fills a void of empirical data on the impact of rapid changes of temperature on river ecosystems. PPL Corporation hopes the research will also underscore its desire for science-based regulations that are protective of aquatic life.

Investments in environmental controls by the company over the last four years at its Brunner Island power plant in York County, Pa., have totaled $800 million. Brunner Island is a three-unit, coal-fired generating plant on the Susquehanna River that was built in the 1960s. The plant generates enough electricity each year to power about 1 million typical homes. The recent environmental upgrades at the Brunner Island plant include the installation of mechanical-draft cooling towers. Work on the $125 million cooling tower project began last year and will be completed in 2010. This overall investment, says PPL, demonstrates PPL’s commitment to the environment while better serving its customers and shareholders by providing the most cost-efficient generation of power.

FILLING THE EMPIRICAL VOID
To better understand the extent of environmental controls needed to protect a river’s macroinvertebrate and fish populations from undue stress related to temperature changes associated with warm water discharges from power plant operations, PPL Corporation asked the Stroud Water Research Center to conduct a site-specific study on a representative set of aquatic organisms that live in the Susquehanna River and its tributaries in the vicinity of the Brunner Island power plant.  

Chapter 93.7 of the Pennsylvania Code sets forth specific water-quality criteria for the state, including the permissible rate of temperature change per hour that can be caused by human activity on state surface waters. Pennsylvania law currently limits the rate of hourly change to 2 degrees Fahrenheit or less. Because power plants regularly discharge artificially heated and cooled water as a byproduct of electricity generation, it’s not surprising that a power company would be interested in the scientific basis for this regulation.  

“Essentially PPL rolled the dice,” said Bern Sweeney, director of the Stroud Water Research Center and principal investigator for the study. “Our reputation for science without bias required that we enter into this relationship only if we could publish the results — regardless of outcome.” 

PPL didn’t hesitate. “The Stroud Water Research Center’s scientific credentials, independent status, and impeccable reputation for detail were key factors in our company’s choice of the Center to conduct this much-needed study,” said Nancy Evans, senior environmental professional and coordinator of the project for PPL. Tinku Khanwalkar, PPL’s Senior Director of Environmental Management, concurred adding, “We’re not aware of a more detailed study anywhere, by any industry and we think the data have broad-based applicability.”

OVERCOMING CHALLENGES IN THE PURSUIT OF SCIENCE
The complex study took six months to design. The first challenge for Stroud scientists was to come up with a theoretical construct that would allow them to isolate the rate of temperature change from all other thermal effects — no small task.

“We had to distinguish the effects of rate of change from everything else related to temperature, including duration, magnitude, and temperature thresholds,” said Sweeney, “and that was just the first of our hurdles.” 

The research team then had to design and build the systems that could reliably produce rapid (up to 8 degrees Fahrenheit per hour) temperature changes with the precision of one tenth of a degree Fahrenheit — a challenge that required extensive mechanical engineering and software development and a feat that, to their knowledge, had never been done before for a river study.
 
The final challenge was the sheer magnitude of the effort required to rear the species needed for the study. Stroud scientists raised more than 4,000 fish, hatched and reared 10,000 or more aquatic insect eggs and larvae, and had to feed all of them each day with carefully measured amounts of home grown algae, disease free fish, or a special mix of dry food depending on the insect or fish.   “This is the first time anyone has applied whole life-cycle testing to twelve different species of stream insects in one study,” said Sweeney. “The husbandry effort alone was huge.  Moreover, every fish had to be individually tracked, measured, and evaluated for primary, secondary, and tertiary stress responses throughout the study.”

UNDERSTANDING SUBLETHAL STRESS TOLERANCES OF FISHES
Seven species of fish were involved in the study, which evaluated rates of temperature change between 1.5 and 8 degrees Fahrenheit per hour day after day under both summer and winter conditions. The study focused on fishes common to the Susquehanna River — including predators (Smallmouth Bass and Walleye), bottom feeders (Channel Catfish and White Suckers), and foragers (Bluntnose Minnow, Spotfin Shiner and Rosyside Dace).

“Not much is known about how short term rates of temperature change affects fish, so we designed our experiment to look at as many responses as possible — from blood-based changes to changes affecting individual organs to overall survivorship,” said Willy Eldridge, who heads the Center’s Fish Molecular Ecology department.  “We looked at muscles, skin, brain — every individual organ from the gills and heart to the liver, kidney and spleen.…We even studied the bones and cartilage.”

A key element of the study focused on growth and survivorship of each species to determine any long-term effects. The research also looked at immediate and short-term indicators of stress, including glucose and cortisol levels. Finally, to validate the results, Stroud scientists relied on histopathology (the microscopic examination of tissue), which was conducted by Dr. Mac Law, an American College of Veterinary Pathology (ACVP) board certified veterinary pathologist at the North Carolina State University College of Veterinary Medicine.  

“We had no preconceived notions about the outcome,” Eldridge said. “What we found was encouraging, as we saw few signs of stress even at the extreme daily temperature changes. Because of our intense evaluation of a broad suite of study parameters, we’re confident in the results.”

ASSESSING THE IMPACT ON AQUATIC INSECT COMMUNITIES
In addition to the fish studies, Stroud scientists tested for thermal impacts over the full life cycle of twelve mayfly species. Mayflies are an important indicator of water quality due to their sensitivity to environmental disturbance, and the scientists looked at everything from embryonic development to larval survivorship, from larval metabolism and growth rates to adult size and egg production. They even studied “larval drift” — a behavioral tactic to avoid predators, which could also indicate thermal stress.

“The bottom line was the same for the insects as for the fish,” said Stroud entomologist John Jackson.

Because of the ground-breaking work achieved by the Stroud scientists, a scientific void has been filled, allowing the State and the private sector to work together  to apply resources where they benefit the environment the most.

Links:
About PPL Corporation
http://www.pplweb.com/about/

To learn more about the scientists involved in the study go to:
About Willy Eldridge
http://www.stroudcenter.org/about/eldridge.htm

About John Jackson
http://www.stroudcenter.org/about/johnjackson.htm

About Bern Sweeney
http://www.stroudcenter.org/about/bernardsweeney.htm

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