http://www.greentechmedia.com/articles/read/report-iron-fed-plankton-slow-to-remove-co2-4020 Report: Iron-Fed Plankton Slow to Remove CO2
Two Berkeley Lab researchers have analyzed data from sea-diving devices and found that seeding iron to boost plankton growth doesn’t lead to the quick scrubbing of carbon dioxide from the atmosphere. Can spreading iron in oceans reduce a lot of carbon dioxide in the atmosphere? Not as much or quickly as you'd think, said researchers at the Lawrence Berkeley National Laboratory. After analyzing data from ocean-diving devices that trawled for carbon dioxide in the deep sea for over a year, Jim Bishop and Todd Wood concluded that phytoplankton aren't the carbon-dioxide removal machines that some believe them to be. "Just adding iron to the ocean hasn't been demonstrated as a good plan for storing atmospheric carbon," says Bishop, who also is an earth sciences professor at UC Berkeley, in a statement. "What counts is the carbon that reaches the deep sea, and a lot of the carbon tied up in plankton blooms appears not to sink very fast or very far." An upcoming issue of the journal Global Biogeochemical Cycles will publish the researchers' results, the lab said Wednesday. There has been a long-held theory, called Iron Hypothesis, that stimulating plankton blooms could significantly remove carbon dioxide, a key greenhouse gas that contributes to global warming, from the atmosphere and deposit them in the ocean. Like plants on land, plankton would eat up carbon dioxide as part of its energy production process under the sun. There are two ways for carbon to sink and get buried in the deep sea. One is through the waste created by sea creatures that eat plankton. And the other is through the death of the plankton themselves. The earth's eco-system has its own, natural ways of producing and removing carbon dioxide from the atmosphere. But the system lacks the power to absorb the growing amount of carbon dioxide and other greenhouse gases produced by human activities such as generating electricity and driving cars. Iron proved to be the steroid that could boost plankton growth, according to research by John Martin at the Moss Landing Marine Laboratories. Martin then proposed that seeding iron in the ocean could turn plankton into weapons for fighting global climate change. Companies have emerged to try to make money from this carbon- sequestration idea. One of them, Planktos, gave up on the idea last year (see Planktos Seeks New Business Ideas). Climos, based in San Francisco, is still in business. CEO Dan Whaley said the Berkeley Lab researchers’ paper didn’t provide the necessary details, such as what types of plankton were observed, to show that phytoplankton aren’t good at burying carbon dioxide in the ocean. “I have the utmost respect for Jim Bishop. But this is clearly not an iron experiment,” Whaley said. “He seems to suggest that growing more plankton won’t store much more carbon – but I think that the geological record argues that it has.” Bishop and Wood said their research showed that the notion of global warming being halted or even reversed by boosting plankton growth is not as easily achieved as some have claimed. The researchers based their findings on data provided by devices called Carbon Explorers, which were first launched in 2002 as part of project by the Moss Landing Marine Lab and the Monterey Bay Aquarium Research Institute. The project set out to test Iron Hypothesis in the ocean between New Zealand and Antarctica during the summer. The Carbon Explorers not only collected data during the iron-seeding experiments, they also did so in the fall and winter for over a year, after evidence of the iron scattering had disappeared, the lab said. The devices were lowered into a depth of 800 meters and more. Results from initial studies showed that, indeed, an artificially induced plankton bloom could remove 10 percent to 20 percent of the carbon from the ocean surface and deposit them to below 100 meters. The research team published a paper in the journal Science in April 2004. Those results were based on data collected 60 days after the iron seeding. But data from the Carbon Explorers in the subsequent 16 months demonstrated that how much carbon can be sequestered by plankton blooms depended largely on the feeding and lifecycle of the zooplankton that eat phytoplankton. Zooplankton don't get easy access to phytoplankton throughout the year, however, because of seasonable weather patterns and how they've adopted to surviving in darkness when sun doesn't shine in Antarctica during winter. As a result, the amount of carbon that can be absorbed by plankton isn't as great as anticipated, the Berkeley Lab researchers said. -- On May 6, 2:17 pm, DW <[email protected]> wrote: > http://www.sciencedaily.com/releases/2009/05/090506131512.htm > Science News > Ocean Carbon: Dent In Iron Fertilization Hypothesis Previously > Proposed To Address Climate Change > > ScienceDaily (May 6, 2009) — Oceanographers Jim Bishop and Todd Wood > of the U.S. Department of Energy’s Lawrence Berkeley National > Laboratory have measured the fate of carbon particles originating in > plankton blooms in the Southern Ocean, using data that deep-diving > Carbon Explorer floats collected around the clock for well over a > year. Their study reveals that most of the carbon from lush plankton > blooms never reaches the deep ocean. > > The surprising discovery deals a blow to the simplest version of the > Iron Hypothesis, whose adherents believe global warming can be slowed > or even reversed by fertilizing plankton with iron in regions that are > iron-poor but rich in other nutrients like nitrogen, silicon, and > phosphorus. The Southern Ocean is one of the most important such > regions. > > “Just adding iron to the ocean hasn’t been demonstrated as a good plan > for storing atmospheric carbon,” says Bishop, a member of Berkeley > Lab’s Earth Sciences Division and a professor of Earth and planetary > sciences at the University of California at Berkeley. “What counts is > the carbon that reaches the deep sea, and a lot of the carbon tied up > in plankton blooms appears not to sink very fast or very far.” > > The reasons, while complex, are most likely due to the seasonal > feeding behavior of planktonic animal life, and specifically to the > effects of the dark Antarctic winter on plant and animal growth and > the mixing of surface and deep waters by winter storms. Phytoplankton > blooms in the spring may indicate that much of the zooplankton > (animal) population essential for carbon sedimentation has starved > during the winter. > > The Carbon Explorers involved in the study were launched in January, > 2002, as part of the Southern Ocean Iron Experiment (SOFeX), a > collaboration led by scientists from Moss Landing Marine Laboratory > and the Monterey Bay Aquarium Research Institute. SOFeX was meant to > test the Iron Hypothesis in waters between New Zealand and Antarctica > during the Antarctic summer. The Berkeley Lab Carbon Explorers were > originally intended to monitor the iron-fertilization experiment for > 60 days, but they continued to report by satellite throughout the > Antarctic fall and winter and on into the following year. > > “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 says. > > He explains that “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 Iron Hypothesis, science and speculation > > In the 1980s, oceanographer John Martin of the Moss Landing Marine > Laboratories, who died in 1993, proposed that iron added to regions of > the ocean that are otherwise rich in nutrients but poor in iron (so- > called high-nutrient, low-chlorophyl, or HNLC, regions) can stimulate > the growth of phytoplankton – a bold scientific hypothesis that has > since been proven correct. > > Martin went further, however, when he suggested that artificial iron > fertilization of the oceans could change the climate. “Give me half a > tankerful of iron and I’ll give you an Ice Age,” he boasted in 1988. > > In testing the Iron Hypothesis, SOFeX’s investigators acknowledged > that matters were not quite that simple, and that the crucial question > was not whether plankton blooms could be induced but whether the > carbon they captured was removed to the deep sea. > > The SOFeX research vessels fertilized and measured two regions of > ocean, one in an HNLC region at latitude 55 degrees south and another > at 66 degrees south. Carbon Explorers were launched at both these > sites; a third Carbon Explorer was launched well outside the iron- > fertilized region at 55°S as a control. Berkeley Lab scientists Todd > Wood, Christopher Guay, and Phoebe Lam were members of the expedition, > while Bishop monitored and communicated with the Carbon Explorers from > Berkeley over a computer link to communications satellites. > > One question was whether the relatively silicate-poor waters of the > more northerly 55° region would allow plankton known as diatoms to > form silicon skeletons. If large diatoms could not grow in this HNLC > region, the SOFeX researchers theorized, enhanced carbon sinking would > not occur. Partly for this reason, most of the effort by the ships was > at 66°S, where silicon wasn’t considered a limiting factor. > > To the researchers’ surprise, the iron-augmented region at 55°N did > form a vigorous plankton bloom. Dubbed the North Patch, Carbon > Explorers tracked this bloom throughout the Antarctic summer, > measuring carbon particles, including waste from grazing zooplankton > and other aggregates, sinking beneath the bloom and carrying 10 to 20 > percent of the fixed carbon out of the surface layer – at least to > below 100 meters. The initial results of the SOFeX experiment, > published in Science in April, 2004, seemed to support the Iron > Hypothesis in an unexpected way. > > But the Carbon Explorers didn’t stop after 60 days. The two North > Patch floats operated for over 14 months, diving, recording, and > surfacing to report data in the world’s stormiest waters, traveling > almost to South America before falling silent. The Carbon Explorer > launched at 66° south lasted 18 months, spending much of its first > winter recording at 800 meters depth and surfacing at weekly intervals > to report, although occasionally prevented by bumping into the > underside of the sea ice. The Carbon Explorer data accumulated, > awaiting analysis. > > Return to the Southern Ocean > > In 2007 Bishop and Lam (who was now at the Woods Hole Oceanographic > Institution) published measurements from shipboard instruments > deployed during SOFeX which suggested that the rosy picture of > plankton blooms sending carbon to the deep ocean wasn’t so simple > after all. Carbon reaching the deep ocean depended partly on particle > size and weight; more important, there seemed to be much less > particulate matter reaching depth where the biomass was highest, e.g., > in plankton blooms. > > “This paper was criticized on the grounds that it was based on limited > shipboard observations,” says Bishop. “So Todd Wood and I turned to > the treasure-trove of virtually continuous observations in the records > of the Carbon Explorers.” > > The Carbon Explorers’ records through the Antarctic summer and fall of > 2002 and the winter and spring of 2003 (and in the case of the float > at 66° south, much longer) not only confirmed the limited shipboard > observations in greater detail but opened up a complex picture of life > in the Southern Ocean. > > The Carbon Explorer at 66°S recorded data never before observed or > reported. During the SOFeX experiment, the float had measured the > demise of a plankton bloom rich in particulate organic carbon. > Particulate carbon levels were severely reduced with the onset of > perpetual darkness and sea ice formation, then modestly increased > again with the return of light and the melting of the ice. Strong > sedimentation – the sinking of large numbers of carbon particles to > the deep ocean – was never observed. > > Data from the two floats deployed farther north at 55°S produced a > startling picture. As noted above, the Explorer launched inside the > original SOFeX iron-amended region, dubbed 55A, had recorded a long- > lasting bloom immediately following iron fertilization, with > sedimentation to 100 meters. Remarkably, 55A found an equally strong > bloom the next spring in the same region – long after the SOFeX iron > was gone – with equally strong sedimentation down to 100 meters. > > And while it was unsurprising that the original control float, dubbed > 55C, did not see a bloom, a bigger surprise came at depth: a rain of > particulate organic carbon at 800 meters down. Carbon Explorer 55C had > measured sedimentation beneath a region with no plankton bloom much > greater than the 55A float measured under the bloom itself. > > To explain this counterintuitive “High Biomass, Low Export” result the > researchers considered a number of ideas. Perhaps current shears had > separated the plankton blooms from their sedimentation; or perhaps > there were “large rare particles” of organic carbon that the Carbon > Explorers had failed to observe; or perhaps differences in mixing of > surface and deep waters during winter storms had brought sequestered > iron back to the surface. The first two hypotheses were rejected, and > the third, even if true, would imply that iron-stimulated blooms still > lead to reduced carbon sedimentation at kilometer depths. > > A fourth hypothesis, taking into account the lighting conditions that > encourage or limit the growth of microscopic plants and zooplankton, > emerged as the most convincing. Latitude 55°S is far enough north for > light to reach into the water year round (although in winter it is > much reduced). But mixing between near-surface and deeper waters can > carry phytoplankton too deep to grow – out of the light, beneath the > critical depth where growth is sufficient to meet the energy demands > of the whole plant and animal community. The latitudes where the > Explorers operated are infamously stormy; in wintertime the mixed > layer can reach 400 or 500 meters deep. > > To survive the winter, zooplankton have to stay deep, ... > > read more » --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "geoengineering" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/geoengineering?hl=en -~----------~----~----~----~------~----~------~--~---
