These folks at WHOI and USC ran their bacteria life cycles for the cyanobacteria known as Trichodesmium ahead to predicted ocean conditions (based on climate models) to 2100, and predict that this particular bacteria, important in the ocean food web will go into “overdrive” and won’t be able to turn off like having a “car with the gas pedal stuck to the floor, heading toward a cliff’s edge” (their words).
Looking back in time though via Sánchez-Baracaldo et al (2014) , this type of bacteria seems to be 600-800 million years old.
From the UNIVERSITY OF SOUTHERN CALIFORNIA
Climate change will irreversibly force key ocean bacteria into overdrive
Scientists demonstrate that a key organism in the ocean’s foodweb will start reproducing at high speed as carbon dioxide levels rise, with no way to stop when nutrients become scarce
Imagine being in a car with the gas pedal stuck to the floor, heading toward a cliff’s edge. Metaphorically speaking, that’s what climate change will do to the key group of ocean bacteria known as Trichodesmium, scientists have discovered.
Trichodesmium (called “Tricho” for short by researchers) is one of the few organisms in the ocean that can “fix” atmospheric nitrogen gas, making it available to other organisms. It is crucial because all life — from algae to whales — needs nitrogen to grow.
A new study from USC and the Massachusetts-based Woods Hole Oceanographic Institution (WHOI) shows that changing conditions due to climate change could send Tricho into overdrive with no way to stop — reproducing faster and generating lots more nitrogen. Without the ability to slow down, however, Tricho has the potential to gobble up all its available resources, which could trigger die-offs of the microorganism and the higher organisms that depend on it.
By breeding hundreds of generations of the bacteria over the course of nearly five years in high-carbon dioxide ocean conditions predicted for the year 2100, researchers found that increased ocean acidification evolved Tricho to work harder, producing 50 percent more nitrogen, and grow faster.
The problem is that these amped-up bacteria can’t turn it off even when they are placed in conditions with less carbon dioxide. Further, the adaptation can’t be reversed over time — something not seen before by evolutionary biologists, and worrisome to marine biologists, according to David Hutchins, lead author of the study.
“Losing the ability to regulate your growth rate is not a healthy thing,” said Hutchins, professor at the USC Dornsife College of Letters, Arts and Sciences. “The last thing you want is to be stuck with these high growth rates when there aren’t enough nutrients to go around. It’s a losing strategy in the struggle to survive.”
Tricho needs phosphorous and iron, which also exist in the ocean in limited supply. With no way to regulate its growth, the turbo-boosted Tricho could burn through all of its available nutrients too quickly and abruptly die off, which would be catastrophic for all other life forms in the ocean that need the nitrogen it would have produced to survive.
Some models predict that increasing ocean acidification will exacerbate the problem of nutrient scarcity by increasing stratification of the ocean — locking key nutrients away from the organisms that need them to survive.
Hutchins is collaborating with Eric Webb of USC Dornsife and Mak Saito of WHOI to gain a better understanding of what the future ocean will look like, as it continues to be shaped by climate change. They were shocked by the discovery of an evolutionary change that appears to be permanent — something Hutchins described as “unprecedented.”
“Tricho has been studied for ages. Nobody expected that it could do something so bizarre,” he said. “The evolutionary biologists are interested in it just to study this as a basic evolutionary principle.”
The team is now studying the DNA of Tricho to try to find out how and why the irreversible evolution occurs. Earlier this year, research led by Webb found that Tricho’s DNA inexplicably contains elements that are usually only seen in higher life forms.
“Our results in this and the aforementioned study are truly surprising. Furthermore, they are giving us an improved, view of how global climate change will impact Trichodesmium and the vital supplies of new nitrogen it provides to the rest of the marine food web in the future.” Webb said.
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The research appears in Nature Communications on September 1. It can be found online at:http://www.nature.com/ncomms/2015/150901/ncomms9155/full/ncomms9155.html
Hutchins, Webb and Saito collaborated with Nathan Walworth, Jasmine Gale and Fei-Xue Fu of USC; and Dawn Moran and Matthew McIlvin of Woods Hole. Their work was funded by the National Science Foundation, grants OCE 1260490, OCE 1143760, OCE 1260233 and OCE OA 1220484; and the G.B. Moore Foundation, grants 3782 and 3934.
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The environmental factors controlling marine nitrogen fixation are hotly debated topics. The contribution of fixed N to the marine nitrogen cycle is also not well understood. A fuller understanding will be a long and arduous task given the inherent biogeochemical complexity, the magnitude of the unknowns and the variability of the ocean basins in both time and space.
An interesting 2013 paper found that nitrogen fixation in the North Atlantic responded to the earth’s orbital cycles and associated ocean circulation patterns finding a roughly 26,000 year cycle over the last 160,000 years. The changes in isotopic N (shells) could not be explained by temperature.
http://www.mathis-hain.net/resources/Straub_et_al_2013_Nature.pdf
The “threat” from cyanobacteria is simply bogus. There are typically 3 potentially limiting nutrients, C, N, and P. Since the ocean is alkaline, C is not limiting. And because alkalinity is decreasing, very likely N is not limiting either. Cyanobacteria have a growth advantage under N-limited conditions, and when N is not limiting, other organisms out-compete can cyanobacteria for resources. Let’s say cyanobacteria did have the chance to outgrow the other organisms, well, then P would become limiting. And that’s likely what conditions were during most of the last century. And if P were also not limiting, then S, Fe, Mg, or some other nutrient would be.
Cyanobacteria never had runaway growth in any significant part of the ocean. What has changed more recently? Very likely there is more agricultural runoff making its way into the ocean now. When N is not limiting, then other organisms can grow and use the available nutrients. And as a result, cyanobacteria do not need to fix nitrogen from the atmosphere. The process of nitrogen fixation results in increased alkalinity. When nitrogen fixation is reduced from levels it had in the past, then alkalinity would be expected to fall in the ocean. That is what we have observed.
Ocean “acidification” almost certainly has nothing to do with increased atmospheric CO2 levels, but everything to do with a reduction in nitrogen fixation. If you want to restore the ocean, control ag runoff.
Oops. A Yoda moment. I very sorry am.
If there is going to be explosive growth of photosynthetic cyanobacteria, then ocean acidification and the accumulation of carbon dioxide will slow. Sounds great to me.
An explosion of cyanobacteria apparently was responsible for poisoning the atmosphere about 2.5 billion years ago. And the greens think humans are destructive.
http://www.scientificamerican.com/article/origin-of-oxygen-in-atmosphere/
okay, here’s the f’n truth.
CO2, and dissolved organic carbon are at a diluted equilibrium in the oceans and the atmosphere. Both have been below a threshold value for biologic rapid consumption. As pCO2 has rapidly increased the sinks (biologic rapid response) kick in and are at the cusp of removing (kinetics) CO2 elevated levels. The boyz at MaunaLoa are now desparately trying to rectify their daily measurements to prevent this record CO2 drop. Biologic sinks of CO2 are kicking and NOAA does not want folks to see it.
There’s an article in Wikipedia (my favorite source of science humor) on “Ocean Fertilization”. A guy named John Martin discovered that iron was the rate-limiting factor in cyanobacteria growth in parts of the ocean. Experiments followed with deliberate seeding of iron-poor waters with iron which resulted in blooms. This was posited as a way to sequester that noted air pollutant, CO2. Unfortunately, an over-expensive climate change-mitigating procedure, with unknown secondary effects if done on a large scale.
Article also commented that Sperm Whale defecation releases iron gained from food they ingest at the ocean depths.
Great article. Shows we are not doomed. We can either dump iron by the boatload or breed Sperm whales in large numbers and save the Earth.