Humans adding less nitrogen to oceans than models predict

January 6, 2016 by Kevin Stacey
A new study suggests that most of the nitrogen deposited from the atmosphere into the open ocean comes from natural sources, not humans. The findings suggest humans aren't disrupting ocean biogeochemistry as much as some models might predict. Credit: Hastings lab / Brown University

A new study finds that human activities are likely contributing far less nitrogen to the open ocean than many atmospheric models suggest. That's generally good news, but it also nullifies a potential side benefit to additional nitrogen, says Meredith Hastings, associate professor of Earth, environmental and planetary sciences at Brown University and one of the study's co-authors.

"People may not be polluting the ocean as much as we thought, which is a good thing," said Hastings, who is also a fellow at the Institute at Brown for Environment and Society. "However, additional could potentially stimulate the ocean's ability to draw down carbon dioxide out the atmosphere, which might counteract carbon emissions to some extent. But if we're not adding as much nitrogen, we're not getting that potential side benefit in the carbon cycle."

The research is published online in Proceedings of the National Academy of Sciences.

Nitrogen is the most abundant gas in the atmosphere and a key ecological nutrient, supporting the growth of plants and providing a food source for microorganisms. But in aquatic environments can cause overgrowth of algae and other aquatic plants, which can throw ecosystems out of balance. Large algal blooms, for example, can deplete waterways of oxygen, leading to mass fish kills and other problems.

But along with the problems, there's a potential upside to excess nitrogen. An influx of nitrogen into the oceans could stimulate the growth of phytoplankton and other photosynthetic organisms. Photosynthesis consumes carbon dioxide, so an increase in biological activity could increase the oceans' ability to draw down atmospheric CO2.

Humans pour tons of additional nitrogen into the atmosphere through the burning of fossil fuels and biomass. Some of that nitrogen is carried by the wind and deposited in the oceans, but just how much of it reaches the vast far from coastlines isn't clear. Some atmospheric models estimate that 80 percent of to the ocean can be traced to humans, which would represent a huge influx of new nitrogen.

"The models generally assume that the ocean is a passive receptor of nitrogen," Hastings said. "We wanted to find out if that's true or if the ocean itself might play a substantial role in emitting nitrogen. If the ocean is playing a role, then this nitrogen deposition isn't all new nitrogen, from the ocean's perspective. It's recycled."

For their study, Hastings and her colleagues looked at the concentration and composition of organic nitrogen in samples of air and rainwater taken on Bermuda over the course of a year. Bermuda, about 600 miles off the eastern U.S. coast, offers scientists a natural test bed for studying the origin of atmospheric pollutants. The weather over the island is dominated by different at different times of year. For much of the year, tropical air blowing northward from the open ocean dominates. But in the winter, a shift in atmospheric pressure pulls in air masses from the continental United States. Those continental air masses bring a host of industrial and agricultural pollutants with them.

"We have these distinct air masses coming in at different times," Hastings said. "So we're able to separate what's coming from anthropogenic sources and what's coming from marine sources."

The study showed that rather than being correlated with the source of air masses, the concentration of aerosol nitrogen is much more tightly correlated to measures of biological activity in the surrounding ocean. As biological activity (measured by a metric called gross primary productivity) increases, so does the concentration of organic nitrogen found in air samples. The molecular makeup of those nitrogen aerosols is also consistent with a marine origin, the researchers found.

"These marine biological processes appear to be producing compounds that are reacting in the atmosphere to create this organic nitrogen," Hastings said.

Organic nitrogen in rainwater samples appeared to contain somewhat more of a human signature, but was still dominated by marine sources, the study showed. Taken together, the results suggest that the ocean plays a much more substantial role in recycling organic nitrogen than was previously thought and that the role of human-derived sources is overestimated in atmospheric models.

This new finding completes a nitrogen puzzle that Hastings and her colleagues have been trying to piece together over the last few years. Organic nitrogen is not the only source of nitrogen deposition to the oceans. In previous work, Hastings and her team studied oceanic deposition of two inorganic nitrogen-based compounds: nitrate and ammonium. Those studies suggested that while a significant portion of nitrate can be traced to human sources, most ammonium deposited in the ocean is, like , largely recycled from marine sources.

Combining results from this new work and their previous work on inorganic nitrogen sources, Hastings and her colleagues estimate that about 27 percent of total nitrogen deposition in the open ocean is derived from human sources—much less than the 80 percent suggested by atmospheric models. That has implications for the idea that nitrogen pollution might help to counteract carbon emissions.

"If we're not putting as much new nitrogen into the open ocean, then we're not stimulating carbon drawdown," Hastings said. "So the impact on the carbon cycle is diminished."

The findings also suggest that more work needs to be done to better represent nitrogen deposition in .

"The models are clearly not getting this right," Hastings said. "We're lacking some understanding here, and that's really interesting to explore."

Explore further: Researchers track ammonium source in open ocean

More information: Marine biogenic source of atmospheric organic nitrogen in the subtropical North Atlantic Katye E. Altieri, DOI: 10.1073/pnas.1516847113 , http://www.pnas.org/content/early/2016/01/05/1516847113.abstract

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16 comments

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Dug
2 / 5 (8) Jan 06, 2016
"The models are clearly not getting this right," Hastings said. "We're lacking some understanding here, and that's really interesting to explore."

What happened to all that "settled science" used in climate models? What happened with the "broad agreement among climate models"? This is like the fifth paper in the last two months I've read that is questioning current climate model results regarding major anthropogenic impacts and their metrology.
Whydening Gyre
3.7 / 5 (3) Jan 07, 2016
If only we had a means to distribute that runoff nitrogen into the deep ocean environment faster...
nilbud
2.3 / 5 (3) Jan 07, 2016
Poor Dug his stupid never ends.
AGreatWhopper
3 / 5 (4) Jan 07, 2016
This indicates good times ahead for PO. http://www.thegua...dy-finds

Of course that doesn't work if no one engages in "debate". Looks like they've no worries there. No one on here has heard of "you're a part of the solution or a part of the problem".

The zealots in here love to bleat about how stupid it is to "leave them unchallenged". Why? Can you point to ANYTHING that has ever accomplished on this site? People know what a rubbish troll looks like. If they see a bunch of idiot trolls in a circle jerk they totally dismiss it. If you're arguing with them, they figure that it's up for debate. The aforereferenced conservative payola will stop flowing to the site.

You're a part of the problem when you do anything but ignore the cranks. If you really think otherwise, then you need to re-read all your posts about "deluded", "mentally ill", cut-and-paste to annoy, etc.
jljenkins
1 / 5 (5) Jan 07, 2016
Whydening Gyre 1 / 5 (1) 7 hours ago
If only we had a means to distribute that runoff nitrogen into the deep ocean environment faster...


Can you imagine a pigeon arguing that it's not fouling your patio, the environment just isn't processing things fast enough? It's the vermin mindset. Yeah, we're in great shape. PO's "progressives" are totally against using the atmosphere as a toilette...that's what the oceans are for!

Vermin. You're all vermin.
ThomasQuinn
3.7 / 5 (6) Jan 07, 2016
I'm going to resort to an analogy for the negationists:

Imagine we were to find a manuscript copy of Beethoven's Ninth Symphony, in which it turns out one note we always assumed was a B flat was, in fact, a C. In an entire 90+ minute symphony, one note turns out to have been misinterpreted. If the climate negationists were to be spewing their propaganda at classical music instead, the remarks of people like Dug would be along the lines of "oh my GOD, we've never really heard any of Beethoven's music, it's all been a forgery!!! Those conductors and orchestras have been SCAMMING us for grant money all these years! Beethoven doesn't exist!"
EnricM
3 / 5 (2) Jan 07, 2016

What happened to all that "settled science" used in climate models? What happened with the "broad agreement among climate models"? This is like the fifth paper in the last two months I've read that is questioning current climate model results regarding major anthropogenic impacts and their metrology.


My car didn't start this morning... what happened to all the automobile factories in the world ?
What happend to the highways? And the asphalt?
What happened to Opel ?

:_(
antigoracle
2.1 / 5 (7) Jan 07, 2016
Imagine we were to find a.....

Imagine you were to find a brain.... and use it.
You'll realize for the climate cultist there's no end to the things we are doing and not doing that's destroying the world.
ThomasQuinn
3 / 5 (4) Jan 07, 2016
Imagine we were to find a.....

Imagine you were to find a brain.... and use it.
You'll realize for the climate cultist there's no end to the things we are doing and not doing that's destroying the world.


A post entirely devoid of substance yet remarkably full of abuse for a text of such short length. You are putting the "I am a troll" on a little thick.
antigoracle
1.7 / 5 (6) Jan 07, 2016
A post entirely devoid of substance yet remarkably full of....

Yep, and your original post was full of substance, but of course being devoid of a brain, you are incapable of grasping the hint as to what that substance is. You are putting the "I am stupid" on a little thick.
thefurlong
5 / 5 (2) Jan 07, 2016
Interesting. So, I might be wrong, but it seems like the process this article refers to is the Carbon Sequestration through photosynthesis, AKA, the "biological pump". See:
http://science.na...n-cycle/

Basically, some phytoplankton use nitrates (among other things) in conjunction with CO2 to form organic carbon, thereby releasing oxygen into the air.

Read more at: http://phys.org/n...html#jCp

It would be great if we could figure out how to geoengineer a solution to all the excess carbon in the atmosphere (assuming the solution didn't create comparable environmental issues, which, from what I have been reading, might happen if we go with the nitrogen pollution route).
thefurlong
5 / 5 (3) Jan 07, 2016
Read more at: http://phys.org/n...html#jCp

Dammit, physorg. Stop injecting your hyperlink when I copy comment text.
Eikka
3.4 / 5 (5) Jan 09, 2016
Humans pour tons of additional nitrogen into the atmosphere through the burning of fossil fuels and biomass. Some of that nitrogen is carried by the wind and deposited in the oceans


That's really confusing, considering the atmosphere is 80% nitrogen already. What they're talking about is nitrates and possibly nitrogen oxides and other nitrogen compounds, not nitrogen itself which is an inert gas that is generally not useful to biological life in its plain form.

Imagine we were to find a manuscript copy of Beethoven's Ninth Symphony, in which it turns out one note we always assumed was a B flat was, in fact, a C.


We could, but then again there are far more disrepancies in the models than just "one note". The current climate models are much more like playing Chopin and calling it Beethoven. Anyone trying to guess the next note based on the assumed style of the author will probably get it wrong.

thefurlong
2.3 / 5 (3) Jan 09, 2016
That's really confusing, considering the atmosphere is 80% nitrogen already.

You are making the mistake of thinking that just because a system has a lot of something, it's ok for it to have more of it, which is simply not true.

Infant bodies are 78% water, but if you give them too much water, they can die from water intoxication.
See https://en.wikipe...xication

What they're talking about is nitrates and possibly nitrogen oxides and other nitrogen compounds

What's your point? Nitrates are partly composed of nitrogen. Presumably biological or other physical processes take the nitrogen, and convert it into nitrate.

We could, but then again there are far more disrepancies in the models than just "one note"...

This is just propaganda. There is no rational basis for you to say this. Neither you, nor your ilk, have ever demonstrated you understand enough of their models OR their predictions to assess their competence.
antigoracle
2.5 / 5 (8) Jan 10, 2016
You are making the mistake of thinking that just because a system has a lot of something, it's ok for it to have more of it, which is simply not true.

You are full of a lot of stupid, yet you persist in acquiring more.
ncdave4life
5 / 5 (1) Jan 12, 2016
Thefurlong wrote,
Read more at...

Dammit, physorg. Stop injecting your hyperlink when I copy comment text.


Amen!

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