Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Model shows long-held constant in ocean nutrient ratio may vary as ecological conditions change

13.05.2004


New research shows that what was once considered a universal constant in oceanography could actually vary in the future – depending on the ecological scenarios that affect competition for resources among microscopic marine plants, which play a role in global climate.


Microscopic image shows clumped cells of blue-green algae, a type of phytoplankton that lives in marine and freshwater environments. Phytoplankton are a rich food source for fish, and they affect global climate by using atmospheric carbon dioxide, a greenhouse gas.
Photo by Hans Paerl, Courtesy University of North Carolina’s Endeavors Magazine.



The future of these plants, called phytoplankton, is important because they exist at the base of the marine food web and represent a large source of food for fish. Also, they affect global climate by using atmospheric carbon dioxide, a greenhouse gas.

Phytoplankton depend upon nitrogen and phosphorus to grow and, ultimately, replenish the supply of these nutrients in the ocean. Since the 1930s, scientists have known that the average nitrogen-to-phosphorus (N:P) nutrient ratio of phytoplankton closely mirrors the N:P ratio in the ocean – 15:1 for the plants and 16:1 for the water. Scientists accepted this as a constant called the Redfield ratio, named after the late Harvard University scientist Alfred Redfield.


But researchers at the Georgia Institute of Technology and Princeton University designed a mathematical model based on phytoplankton physiology. It shows a broad range of N:P ratios are possible depending on the conditions under which species grow and compete. This research – part of a larger biocomplexity research project led by Professor Simon A. Levin at Princeton -- is published in the May 13 edition of the journal Nature.

"The take-home message is that this finding reinforces what some researchers have been saying lately – that N:P is not so fixed," said lead author Christopher Klausmeier, a Georgia Tech assistant professor of biology and former postdoctoral fellow at Princeton. Other authors are Elena Litchman, also of Georgia Tech, and Tanguy Daufresne and Levin of Princeton.

"This shows the range of ratios within which we could expect the ocean to change in the future," Klausmeier said. "Right now we have 16:1, but 500 years from now, if we have a different mix of growth conditions, then it might change the overall N:P needs of the phytoplankton community and the ocean."

Under two extreme conditions – one with few resources because of increased competition and the other with abundant nutrients – researchers determined the optimal strategies that phytoplankton use to allocate the cellular machinery – namely ribosomes and chloroplasts -- for nutrient uptake. Ribosomes assemble two proteins that take up nitrogen and phosphorus. Chloroplasts gather energy from the sun.

"When competing to the very end, then the optimal strategy has a lot of resource acquisition machinery, but not much assembly machinery," Klausmeier explained. "In that case, there aren’t many ribosomes, and therefore not much phosphorus. So if you have a small amount of phosphorus, you have a high N:P ratio. This strategy is best for competition to equilibrium.

"In the other scenario, where nutrients are very available, you have a lot of ribosomes. Then you have a lot of phosphorus and therefore, a low N:P ratio. This is optimal under exponential growth conditions," Klausmeier added.

Given these optimal strategies, researchers were able to determine the N:P needs of species competing at the extremes. "These two scenarios set the endpoints of what happens in reality," Klausmeier explained. "In the real world, it’s a mix of conditions."

From a literature review earlier in the study, they found that N:P ratios among different species vary from 7:1 to 43:1 – with one oddity requiring a 133:1 ratio. Results from modeling the optimal strategies mirror this range of ratios, Klausmeier said, in contrast with the long-accepted constant ratio of N:P in the ocean.

"The 16:1 Redfield ratio has been used too dogmatically by some scientists," Klausmeier said. "It has been treated as an optimum ratio, but that’s not what Redfield intended. He has been misunderstood and oversimplified. This ratio is an average that is subject to change."

As is the case in many other ecological studies, researchers in this study had to confront the natural variability found in nature.

"This is a very ecological story," Klausmeier noted. "One thing that frustrates ecology and makes it tough is that there’s a lot of natural variability. We want to explain the variability, not just the average number. So this problem turned out to be more complicated because of the variability."

Klausmeier’s findings have broader implications, as well, because of the roles phytoplankton play in the ocean ecosystem and across the globe.

"Phytoplankton do half of the planet’s primary production," Klausmeier explained. "They capture energy from the sun and have a big role in biogeochemical cycles -- how elements cycle through the biosphere. Phytoplankton have a main role in the carbon cycle. They need carbon dioxide to grow, so they suck it out of the atmosphere, controlling its presence there. And that ties into global climate."

Klausmeier believes his study contributes to a better understanding of global biogeochemical cycles. "It’s important for us to understand global climate and how it might change in the future," he added. "And ocean life, such as phytoplankton, is a big player in climate."


###
This study was funded by grants from the National Science Foundation and the Andrew Mellon Foundation for Levin’s biocomplexity project. Biocomplexity refers to studies of ecological and evolutionary systems as a whole.

Georgia Tech Research News and Research Horizons magazine, along with high-resolution JPEG images, can be found on the Web at http://www.gtresearchnews.gatech.edu.

Media Contacts:
1. Jane M. Sanders, 404-894-2214, or E-mail: jane.sanders@edi.gatech.edu.
2. John Toon, 404-894-6986, or E-mail: john.toon@edi.gatech.edu.

For technical information, contact:
1. Christopher Klausmeier, Georgia Tech, 404-385-4241 or E-mail: Christopher.klausmeier@biology.gatech.edu.
2. Simon A. Levin, Princeton University, 609-258-6880 or E-mail: slevin@eno.princeton.edu.

Jane Sanders | Georgia Tech
Further information:
http://www.gtresearchnews.gatech.edu/newsrelease/nutrient.htm

More articles from Ecology, The Environment and Conservation:

nachricht When corals eat plastics
24.05.2018 | Justus-Liebig-Universität Gießen

nachricht Dispersal of Fish Eggs by Water Birds – Just a Myth?
19.02.2018 | Universität Basel

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Molecular switch will facilitate the development of pioneering electro-optical devices

A research team led by physicists at the Technical University of Munich (TUM) has developed molecular nanoswitches that can be toggled between two structurally different states using an applied voltage. They can serve as the basis for a pioneering class of devices that could replace silicon-based components with organic molecules.

The development of new electronic technologies drives the incessant reduction of functional component sizes. In the context of an international collaborative...

Im Focus: LZH showcases laser material processing of tomorrow at the LASYS 2018

At the LASYS 2018, from June 5th to 7th, the Laser Zentrum Hannover e.V. (LZH) will be showcasing processes for the laser material processing of tomorrow in hall 4 at stand 4E75. With blown bomb shells the LZH will present first results of a research project on civil security.

At this year's LASYS, the LZH will exhibit light-based processes such as cutting, welding, ablation and structuring as well as additive manufacturing for...

Im Focus: Self-illuminating pixels for a new display generation

There are videos on the internet that can make one marvel at technology. For example, a smartphone is casually bent around the arm or a thin-film display is rolled in all directions and with almost every diameter. From the user's point of view, this looks fantastic. From a professional point of view, however, the question arises: Is that already possible?

At Display Week 2018, scientists from the Fraunhofer Institute for Applied Polymer Research IAP will be demonstrating today’s technological possibilities and...

Im Focus: Explanation for puzzling quantum oscillations has been found

So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics

Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...

Im Focus: Dozens of binaries from Milky Way's globular clusters could be detectable by LISA

Next-generation gravitational wave detector in space will complement LIGO on Earth

The historic first detection of gravitational waves from colliding black holes far outside our galaxy opened a new window to understanding the universe. A...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Save the date: Forum European Neuroscience – 07-11 July 2018 in Berlin, Germany

02.05.2018 | Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

 
Latest News

Surgery involving ultrasound energy found to treat high blood pressure

24.05.2018 | Medical Engineering

First chip-scale broadband optical system that can sense molecules in the mid-IR

24.05.2018 | Physics and Astronomy

Beyond the limits of conventional electronics: stable organic molecular nanowires

24.05.2018 | Power and Electrical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>