Navigation Links
Nutrient pollution drives frog deformities by ramping up infections, says CU-Boulder study
Date:9/24/2007

High levels of nutrients used in farming and ranching activities fuel parasite infections that have caused highly publicized frog deformities in ponds and lakes across North America, according to a new study led by the University of Colorado at Boulder.

The study showed increased levels of nitrogen and phosphorus cause sharp hikes in the abundance and reproduction of a snail species that hosts microscopic parasites known as trematodes, said Assistant Professor Pieter Johnson of CU-Boulder's ecology and evolutionary biology department. The nutrients stimulate algae growth, increasing snail populations and the number of infectious parasites released by snails into ponds and lakes. The parasites subsequently form cysts in the developing limbs of tadpoles causing missing limbs, extra limbs and other severe malformations, Johnson said.

"This is the first study to show that nutrient enrichment drives the abundance of these parasites, increasing levels of amphibian infection and subsequent malformations," said Johnson. "The research has implications for both worldwide amphibian declines and for a wide array of diseases potentially linked to nutrient pollution, including cholera, malaria, West Nile virus and diseases affecting coral reefs."

Johnson is the lead author of a study on the subject published online the week of Sept. 24 in the Proceedings of the National Academy of Sciences. Co-authors include Jonathan Chase from Washington University, Katherine Dosch, Richard Hartson, Daniel Sutherland and Stephen Carpenter from the University of Wisconsin, Jackson Gross from the Southern California Coastal Water Research Project and Don Larson from University of Alaska. The National Science Foundation funded the work.

Deformed frogs first gained international attention in the mid-1990s when a group of Minnesota schoolchildren discovered a pond where more than half of the leopard frogs had missing or extra limbs, he said. Since then, reports of deformed amphibians have become widespread in the United States, leading to speculation they were being caused by factors like pesticides, increased ultraviolet radiation or parasitic infection.

While parasite infection is now recognized as a major cause of such deformities, the environmental factors responsible for increases in parasite abundance had largely remained a mystery until the study was undertaken, Johnson said.

"One of our main goals was to understand how parasites are going to respond to land-use changes and ecosystem alterations," he said. "What we found is that nitrogen and phosphorus pollution from agriculture, cattle grazing and domestic runoff have the potential to significantly promote parasitic infection and deformities in frogs."

The trematode has a complex life cycle that involves three host species, he said. In addition to the infectious stage in snails and the cyst stage in frogs, the parasites rely on predators including wading birds to complete their life cycle by consuming infected frogs and spreading the parasite back into the ecosystem through defecation.

The research team built 36 artificial ponds in central Wisconsin similar to farm stock tanks -- a common breeding site of frogs and salamanders -- and stocked each with selected numbers of snails and tadpoles of the green frog. In addition to adding nutrients, the researchers took on the role of birds in the trematode life cycle by adding parasite eggs to the tanks, then measuring the subsequent ecological responses.

In ponds with added nutrients, snail biomass increased by 50 percent and the snails increased parasite egg production by up to eight-fold, he said. The infection rate in frogs rose by two- to five-times in those tanks, Johnson said.

As few as 12 trematode larvae, known as cercariae, can kill or deform a single tadpole by burrowing into their limb regions and disrupting normal leg development, he said. A single infected snail can produce more than 1,000 cercariae in one night. Frogs that become deformed rarely survive long in the wild, he said.

"We were able to watch nutrient pollution move through the life cycle of the parasite as it cascaded through the food web," he said. "Since most human diseases involve multiple hosts, understanding how increased nutrient pollution affects freshwater and marine food webs to influence disease is an emerging frontier in ecological research."

A recent study of more than 6,000 species of amphibians worldwide concluded that 32 percent were threatened and 43 percent were declining in population. While the causes range from habitat loss to emerging disease, the researchers are now exploring how nutrient pollution and limb malformations contribute to the pattern, Johnson said.


'/>"/>

Contact: Pieter Johnson
Pieter.Johnson@colorado.edu
303-492-5623
University of Colorado at Boulder
Source:Eurekalert

Related biology news :

1. Mechanism for the captation of nutrients in plants- unknown to date
2. Hidden sponges determine coral reefs nutrient cycle
3. Tropical forest CO2 emissions tied to nutrient increases
4. Metal homeostasis research in plants will lead to nutrient-rich food and higher yielding crops
5. Wheat gene may boost foods nutrient content
6. Too much of a good thing? Excess nutrients or water limit biodiversity
7. New mechanism for nutrient uptake discovered
8. Fish extinctions alter critical nutrients in water, study shows
9. Solution to Pollution: New Bacteria Eats Toxic Waste
10. UN environmental agency steps up battle against marine pollution
11. Pollution-eating bacteria produce electricity
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:3/31/2016)... March 31, 2016  Genomics firm Nabsys has completed ... Barrett Bready , M.D., who returned to the ... original technical leadership team, including Chief Technology Officer, ... Development, Steve Nurnberg and Vice President of Software and ... company. Dr. Bready served as CEO of ...
(Date:3/22/2016)... PUNE, India , March 22, 2016 ... new market research report "Electronic Sensors Market for ... Fingerprint, Proximity, & Others), Application (Communication & ... and Geography - Global Forecast to 2022", ... consumer industry is expected to reach USD ...
(Date:3/18/2016)... --> --> Competitive Landscape Analysis ... Physical infrastructure and Perimeter Surveillance & Detection Systems ... and the continuing migration crisis in the Middle ... led visiongain to publish this unique report, which is crucial ... & security companies in the border security market and the ...
Breaking Biology News(10 mins):
(Date:5/23/2016)... England , May 23, 2016 ... May 25 th at 10:15 a.m. ET before the ... the role genetically engineered mosquitos can play in controlling the ... carrier of the Zika virus.      (Logo: ... engineered male mosquito with a self-limiting gene. Trials in ...
(Date:5/23/2016)... ... May 23, 2016 , ... RoviSys, a leading independent provider ... Ohio, has broken ground on a new building in Holly Springs, NC. With ... new location solidifies a commitment to business in the region. The new facility ...
(Date:5/22/2016)... , ... May 22, 2016 , ... Doctors in Rome ... combating the asbestos cancer, malignant mesothelioma. Surviving Mesothelioma has just posted an article on ... the University of Rome’s Department of Clinical Sciences and Translational Medicine evaluated more than ...
(Date:5/20/2016)... ... May 20, 2016 , ... Kablooe Design, a leading provider ... announced its official 25th anniversary of the business. “We have worked hard to build ... our customers for the privilege and honor of serving their product design and development ...
Breaking Biology Technology: