Nutrients, viruses, and the biological carbon pump

Southampton, UK (SPX) Jul 02, 2010 - Adding nutrients to the sea could decrease viral infection rates among phytoplankton and enhance the efficiency of the biological pump, a means by which carbon is transferred from the atmosphere to the deep ocean, according to a new mathematical modelling study.

The findings, published in the Journal of Theoretical Biology, have implications for ocean geo-engineering schemes proposed for tackling global warming.

Tiny free-floating algae called phytoplankton dominate biological production in the world's oceans and sit at the base of the marine food web. Their population dynamics are controlled by sunlight, nutrient availability, grazing by tiny planktonic animals (zooplankton) and mortality caused by viral infection.

"Viruses are the most abundant organism in the world's oceans, and it is thought that all phytoplankton species are susceptible to infection. Our aim was to model the interaction between viruses, phytoplankton, zooplankton grazing and nutrient levels," said Dr Adrian Martin of the National oceanography Centre (NOC), who collaborated in the project with Dr Christopher Rhodes, a bio-mathematician at Imperial College London.

The researchers took an 'eco-epidemic' modelling approach, taking into account the mutual interaction between the effects of ecology and disease epidemiology. This approach has been used previously to model the effects of infection by pathogens on the population dynamics of mammals and invertebrate animals. …

The models predict that decreased nutrient levels correspond to high viral infection rates among phytoplankton.

On the other hand, increased nutrient levels are predicted to decrease viral infection rates. This means that more of the carbon contained in phytoplankton would be available to zooplankton and other creatures higher up the food chain.

When these organisms die, a proportion of the associated carbon would sink down to the deep ocean, where it could be locked away for centuries, rather than being released back to the atmosphere as carbon dioxide. This mechanism for exporting carbon to the deep ocean is called the biological carbon pump. …

Nutrients, Viruses And The Biological Carbon Pump

Technorati Tags: carbon dioxide,carbon,carbon sequestration,geoengineering,geo-engineering,global warming,climate change

Stanford: Geoengineering will not help oceans

“Geoengineering” experiments proposed to reduce global warming by blocking sunlight with atmosphere-injected particles may cool the world but still leave carbon dioxide levels dangerously high, Stanford scientists say.

Sunlight-blocking particles would fail to solve the problems of ocean acidification and dying corals, two significant repercussions of climate change, according to a study by Ken Caldeira of Stanford University and the Carnegie Institution, Damon Matthews of Concordia University, and Long Cao of the Carnegie Institution. Atmospheric carbon dioxide dissolves in ocean water, making it more acidic and difficult for animals to build their shells or skeletons, especially corals.

Proponents of geoengineering have called for injecting small, reflective particles into the atmosphere to partially block sunlight and cool the earth, just as ash from an erupting volcano does. The resulting carbon-dioxide-rich climate would cause land plants to grow more vigorously, hold onto more carbon and release less to the ocean. But the difference would not be enough to fundamentally alter the plight of coral reefs, Caldeira said.

The researchers used computer models of the Earth’s climate system and biosphere to simulate the effect of sunlight-reflecting particles on climate and ocean chemistry. Such geoengineering methods “might be able to address some of the climate effects of carbon dioxide but they don’t fundamentally address the chemical effects posed by carbon dioxide,” Caldeira said.

“Instead of taking till 2050 until there’s no place left in the ocean where corals can survive, it might be 2053. The carbon cycle effects of the geoengineering might delay that outcome in the ocean by a few years but wouldn’t prevent those outcomes from occurring,” he said. The scientists’ work was published in Geophysical Research Letters. …

Global warming tactic cools climate but won’t help corals, say Stanford researchers

Technorati Tags: ocean acidification,geoengineering

Scientists rank global cooling hacks

Not all climate hacks are created equal.

The dozens of ways that scientists, as well as crackpots, have proposed to geoengineer the world's climate won't all be equally effective. In fact, some of them, particularly the ones that rely on sucking up carbon dioxide instead of blocking out solar radiation, will hardly have any impact at all, a new study in the journal Atmospheric Chemistry and Physics found.

"By 2050, only stratospheric aerosol injections or sunshades in space have the potential to cool the climate back toward its pre-industrial state," earth scientists Tim Lenton and Naomi Vaughan of East Anglia University in England write.

Many global cooling approaches have been floated. The broad range of the proposals — from injecting the upper atmosphere with sun-blocking particles to creating plankton blooms by feeding them extra iron to burying carbon-filled "biochar" in soil — has made comparing them very difficult. The new study provides the first useful comparisons of a wide variety of geoengineering ideas.

The study did not calculate the costs or environmental impacts of any of the techniques, but for most of the climate hacks, they could be large. For those reasons, the authors of the paper recommend reducing the amount of our emissions, not just banking on geoengineering to bail us out.

"Climate geoengineering is best considered as a potential complement to the mitigation of CO2 emissions, rather than as an alternative to it," they write.

Scientists Rank Global Cooling Hacks

Technorati Tags: global warming,geoengineering