According to the simplest version of the so called Iron Hypothesis, plankton blooms move atmospheric carbon down to the deep sea and increased carbon dioxide levels in the atmosphere can therefore be counteracted by promoting plankton blooms. The Iron Hypothesis derives its names from the suggestion that global warming can be thwarted by fertilizing plankton with iron in regions that are iron-poor but rich in other nutrients like nitrogen, silicon, and phosphorus, such as the Southern Ocean.

New research from the U.S. Department of Energy’s Lawrence Berkeley National Laboratory is now dealing a powerful blow to this hypothesis by showing that most of the carbon used for plankton blooms never reaches to deep sea.

Using data collected around the clock for over a year by deep-diving Carbon Explorer floats, Oceanographers Jim Bishop* and Todd Wood** have revealed that a lot of the carbon tied up by plankton blooms never sink very far.

“Just adding iron to the ocean hasn’t been demonstrated as a good plan for storing atmospheric carbon,” says Bishop. “What counts is the carbon that reaches the deep sea, and a lot of the carbon tied up in plankton blooms appear not to sink very fast or very far.”

The reasons behind this behaviour are complex, but the seasonal feeding behaviour of planktonic animal life is believed to play major part.

Photoplankton

The Carbon Explorer floats used in the study were launched in January 2002, as a part of the Southern Ocean Iron Experiment (SOFeX)***, and experiment meant to test the Iron Hypothesis in the waters between New Zealand and Antarctica during the Antarctic summer.

SOFeX fertilized and measured two regions of ocean, one in an HNLC (high-nutrient, low-chlorophyl) region at latitude 55 degrees south and another at 66 degrees south. Carbon Explorers were launched at both these sites while a third Carbon Explorer was launched well outside the iron-fertilized region at 55 degrees south as a control.

Bishop and Wood were originally assigned to the project to monitor the iron-fertilization experiment for 60 days, but the Carbon Explorers continued to transmit data throughout the Antarctic fall and winter and on into the following spring.

“We would never have made these surprising observations if the autonomous Carbon Explorer floats hadn’t been recording data 24 hours a day, seven days a week, at depths down to 800 meters or more, for over a year after the experiment’s original iron signature had disappeared,” Bishop explains. “Assumptions about the biological pump – the way ocean life circulates carbon – are mostly based on averaging measurements that have been made from ships, at intervals widely separated in time. Cost, not to mention the environment, would have made continuous ship-based observations impossible in this case. Luckily one Carbon Explorer float costs only about as much as a single day of ship time.”

The scientific hypothesis that iron can be used to stimulate phytoplankton growth in regions low in iron but rich in other nutrients is still intact and experiments show that algal blooms do in fact occur if you add iron to such waters. The study by Bishop and Wood only shows that the carbon bound by the plankton do not end up far down in the depths of the sea.

Jim Bishop’s team. (From left) Christopher Guay,
Phoebe Lam, Jim Bishop, Todd Wood, and David Kaszuba.

During the early stages of the South Sea experiment, the Iron Hypothesis seemed to hold up to scrutiny as the Berkeley researchers could detect not only a vigorous plankton bloom in the fertilized region at 55°N, but also how carbon particles sank beneath the bloom carrying 10-20 percent of the fixed carbon away from the surface layer and down to a dept of at least 100 meters. These results were published in the 2004April issue of Science.

But since the Carbon Explorers continued to submit information even when the 3-month study was officially over, Bishop and Wood could continue their monitoring of South Sea carbon levels throughout fall and winter and well into the following spring; a continued monitoring that would prove invaluable.

The two Carbon Explorers released at 55 degrees south continued to report for over 14 months and almost reached South America before they turned silent. After this, the explorer launched at 66 degrees south continued to transmit for another four months, despite having spent much of the Arctic winter recording at a dept of 800 meters where the pressure is immense. This explorer also had several encounters with the underside of chunky sea ice as it tried to surface to report during the Arctic winter.

All this new data surprisingly showed that there seemed to be much less particulate matter reaching the depth where the biomass was highest, i.e. in plankton blooms. Reports from the 66°S explorer showed how particulate carbon levels decreased sharply as the perpetually dark Arctic winter commenced and ice began to cover previously open waters. As the sun returned in spring and melted the ice the levels made a modest increase, but no sinking (sedimentation) of large amounts of carbon to the deep ocean was observed.

Another even more surprising report came from the control float, dubbed 55 C, which reported higher sedimentation of carbon 800 meters under a region with no plankton bloom than what the other 55°S (dubbed 55A) reported from the fertilized, blooming region.

Researchers are currently pondering several ideas as to explain these unforeseen results but have not reached any conclusion. A higher biomass seems to be linked to a lower export of carbon, but one knows why. One of the most promising hypotheses takes into account how phytoplankton needs sufficient amounts of light to survive and grow. Latitude 55°S is located far enough from the Arctic for light to reach the ocean year round, even though the amount is severely reduced during the winter months. But the notorious winter storms occurring in these waters can cause mixing between near-surface water and underlying water layers all the way down to a dept of 400-500 meters. Phytoplankton are dragged down to depths where it is too dark for them to grow and where hungry zooplankton waits for them.

“Mixing is the dumbwaiter that brings food down,” says Bishop. “The question is whether the dumbwaiter is empty or full.”

If mixing is consistently below the critical light level, phytoplankton can not grow, i.e. the dumbwaiter stays empty and the zooplankton gets no food. As the winter storms stop with the advent of spring, the phytoplankton can quickly rebound, aided by increased levels of sunlight. But since a lot of zooplankton starved to death during the winter, the zooplankton population is not large enough to keep steps with the phytoplankton bloom and intercept carbon loaded material as it sinks between 100 and 800 meters.

In the part of the South Sea where Carbon Explorer 55C spent the winter collecting data, storms where not continuous and the mixing was therefore halted now and then. More zooplankton survived, zooplankton which fed on the phytoplankton in spring, keeping their numbers down and increasing carbon sedimentation.

Bishop says these observations point to an important lesson: “Iron is not the only factor that

determines phytoplankton growth in HNLC regions. Light, mixing, and hungry zooplankton are fundamentally as important as iron.”

You can find more information about Bishop and Wood’s study in the journal Global Biogeochemical Cycles. Preprints of the issue are already available to subscribers at http://www.agu.org/journals/gb/papersinpress.shtml.

* Jim Bishop is a member of Berkeley Lab’s Earth Sciences Division and a professor of Earth and planetary sciences at the University of California at Berkeley.

** Todd Wood is a staff researcher with the U.S. Department of Energy’s Laurence Berkley National Laboratory.

*** The Southern Ocean Iron Experiment (SOFeX) is a collaboration led by scientists from Moss Landing Marine Laboratory and the Monterey Bay Aquarium Research Institute.

Cement is one of the largest sources of carbon dioxide emissions in the world. About 5% of all carbon dioxide (CO2) emitted into the atmosphere can be traced back to cement production. When 1 metric ton of cement is produced one ton carbon dioxide is emitted into the atmosphere: The carbon dioxid is emitted when the limestone used in the cemented is created. 2.5 billion tons of cement is manufactured each year.

Now Stanford Professor Brent Constantz have created a new type of cement that can be created without any carbon dioxide at all being emitted. If Constantz can get the product into the market quickly (he has one pilot factory now), on a big scale and at a decent price this might allow us to eliminate 5% of the worlds carbon dioxide emissions in one swift action taking an important step towards fighting global warming.

Sounds too good to be true? Then you in for a surprise, it gets better; the new type of cement is not only carbon emission neutral it will actually help reduce the amount of carbon dioxide released in the atmosphere. Regular cement emits carbon dioxide when it is created this new type binds carbon dioxide. When one ton of this new type of cemented is manufactured it binds 500 kg carbon dioxide that otherwise would end up in the atmosphere.

Early calculations show that this new type of cement can be provided about 10% cheaper than regular cement aka. Portland cement. Exactly how all this is achieved will remain a secret until the patent has been approved but in broad terms it is achieved by bubbling exhaust gas from power plants through sea water to create the ingredients for the new cement. It is when the exhaust gas is bubbled through the sea water the carbon dioxide that otherwise would get emitted into the atmosphere is bound in the new cement. Producing this type of cement will in other words reduce the CO2 emissions from power plants. The process was inspired by the way coral grow and form their exoskeletons.

The same process might also be used to create CO2 neutral concrete and asphalt further reducing global carbon dioxide emissions.

Stanford Professor Brent Constantz has had a distinguished career and this new cement is only his latest discovery. He has over 60 cement based patents and 22 years ago he revolutionized bone fracture repair when he created high-tech medical cement. When Constantz learned about the problems caused by the high CO2 emissions levels, he thought he could do better.

He says that: The reason no one invented it before now is that people didn’t truly understand the dangers of CO2 until less than a decade ago.

He has venture capital backing to bring this product to the marketing and a team is looking for U.S. locations where new production facility can be built in cooperation with power plants but no formal agreements have been reached yet. Professor Brent Constantz suggest that the new type of cement initially should be used in a mix with regular Portland cement to make contractors used to using it before switching over to using exclusively this new type of cement. He says that he thinks this is one of the most important discoveries he made and that “Climate change is the largest challenge of our generation,”

There is however skeptics that is not yet convinced by the product. They state that they hope the new cement will live up to the hype but that tests has to be done before they are going to feel that this new cement will be able to replace the over 100 year old Portland cement.

If this product will be a game changer dramatically reducing global carbon dioxide emissions remain to be seen but if this cement really turns out to be a good replacement that is both carbon dioxide neutral and cheaper than Portland cement it is great news. Great news indeed.