Saturday, February 24 , 2018, 3:56 am | Fair 35º

 
 
 
 

Parasites Outweigh Predators, Pacific Coast Estuary Study Finds

Findings by the team, including UCSB researchers, show for the first time that parasites might drive the flow of energy in ecosystems.

In a study of free-living and parasitic species in three estuaries on the Pacific coast of California and Baja California, a team of researchers from UCSB, the U.S. Geological Survey and Princeton University has determined that parasite biomass in those habitats exceeds that of top predators, in some cases by a factor of 20.

Their findings, which could have significant biomedical and ecological implications, will appear in Thursday’s issue of the science journal Nature.

Armand Kuris, a professor of zoology in UCSB’s Department of Ecology, Evolution and Marine Biology and a lead author of the paper, says the study’s findings have a potential effect on the perceived role of parasites in an ecosystem. From an ecological perspective, parasites serve both as regulators to prevent species from becoming numerically dominant and as indicators of the health of a particular ecosystem. The study shows for the first time that parasites might drive the flow of energy in ecosystems.

“The total amount of energy flow in ecosystems due to infectious processes must be enormous — even greater than we’d expect given the large parasite biomass,” Kuris said. “I expect the amount of energy going into host tissue repair and replenishment is also huge. An implication of our study is that we should pay more attention to the energetics of disease.”

Biomass is the amount of living matter that exists in a given habitat. It is expressed either as the weight of organisms per unit area or as the volume of organisms per unit volume of habitat. Until now, scientists have believed that because parasites are microscopic in size that they make up a small fraction of biomass in a habitat while free-living organisms such as fish, birds and other predators make up the vast majority.

The researchers quantified the biomass of free-living and parasitic species in the three estuaries and demonstrated that parasites have substantial biomass in these ecosystems. “Parasites have as much, or even more, biomass than other important groups of animals — like birds, fishes and crabs,” said Ryan Hechinger, a researcher at UCSB’s Marine Science Institute and co-lead author of the paper.

The article grew out of a five-year study supported by a $2.2 million grant from the National Science Foundation and the National Institutes of Health through the agencies’ joint Ecology of Infectious Diseases Program.

In addition to Kuris, principal investigators include Kevin Lafferty, a marine ecologist with the U.S. Geological Survey; and Andrew Dobson, a professor of ecology and evolutionary biology at Princeton University. Other important collaborators included Leopoldina Aguirre-Macedo, of the Centro de Investigación y Estudios Avanzados Unidad Mérida, and Mark Torchin, a staff scientist with the Smithsonian Tropical Research Institute.

The researchers quantified parasites and free-living organisms in the Carpinteria Salt Marsh and in the Bahia San Quintín and Estero de Punta Banda estuaries in Baja California. Their study included 199 species of free-living animals, 15 species of free-living vascular plants and 138 species of parasites.

“The reason we wanted to complete this study is because a lot of work we’ve done has suggested that parasites are important in ecosystems. But no one’s actually looked at them as a group throughout an ecosystem,” Lafferty said. “Also, no one’s considered parasites from the perspective of how much they weigh because it’s always been assumed they weigh almost nothing. Now we know that’s not true. For example, in an estuary there are more kilograms of trematode worms — parasites — than kilograms of birds. If you could see the trematodes with binoculars, you might not bother bird watching.”

Hechinger said, “No one debates whether it’s important for ensuring human welfare to understand how ecosystems work. How can we possibly understand something without accounting for its major parts? Because our findings indicate that parasites control a massive amount of biomass, it would seem future research can’t ignore them.”

According to Kuris, understanding the enormity of parasite biomass and the burden it places on available hosts could lead to new strategies in the management of infectious diseases. Treatment protocols might put greater emphasis on enhancing the host’s ability to defend itself against parasitic disease and slow the rate of energy uptake by the parasites and pathogens.

Andrea Estrada represents UCSB Internal Affairs.

  • Ask
  • Vote
  • Investigate
  • Answer

Noozhawk Asks: What’s Your Question?

Welcome to Noozhawk Asks, a new feature in which you ask the questions, you help decide what Noozhawk investigates, and you work with us to find the answers.

Here’s how it works: You share your questions with us in the nearby box. In some cases, we may work with you to find the answers. In others, we may ask you to vote on your top choices to help us narrow the scope. And we’ll be regularly asking you for your feedback on a specific issue or topic.

We also expect to work together with the reader who asked the winning questions to find the answer together. Noozhawk’s objective is to come at questions from a place of curiosity and openness, and we believe a transparent collaboration is the key to achieve it.

The results of our investigation will be published here in this Noozhawk Asks section. Once or twice a month, we plan to do a review of what was asked and answered.

Thanks for asking!

Click here to get started >

Support Noozhawk Today

You are an important ally in our mission to deliver clear, objective, high-quality professional news reporting for Santa Barbara, Goleta and the rest of Santa Barbara County. Join the Hawks Club today to help keep Noozhawk soaring.

We offer four membership levels: $5 a month, $10 a month, $25 a month or $1 a week. Payments can be made through PayPal below, or click here for information on recurring credit-card payments.

Thank you for your vital support.



Reader Comments

Noozhawk is no longer accepting reader comments on our articles. Click here for the announcement. Readers are instead invited to submit letters to the editor by emailing them to [email protected]. Please provide your full name and community, as well as contact information for verification purposes only.

Daily Noozhawk

Subscribe to Noozhawk's A.M. Report, our free e-Bulletin sent out every day at 4:15 a.m. with Noozhawk's top stories, hand-picked by the editors.

Sign Up Now >