Coccolithophore growth and calcification -- a possible role for iron

Jun 30, 2010
Emiliania huxleyi is a globally important species of phytoplankton. Credit: Alex Poulton/NOC

Lack of sufficient iron may be a significant factor in controlling massive blooms of Emiliania huxleyi, a globally important species of marine algae or phytoplankton, according to research led by researchers at the National Oceanography Centre (NOC) in Southampton.

Emiliania huxleyi is a species of coccolithophore found in oceans all around the world, from the tropics to the . Coccolithophore blooms often develop during the summer when a blanket of water called the thermocline develops between the upper mixed layer above and the deep water below.

These blooms can be seen from space as large areas of highly reflective water. This increased reflectivity is caused by shedding of coccoliths, the calcite plates that form the external skeleton or 'shell' of the organism, when nutrients are becoming depleted and the bloom is in decline.

The new research took place during a cruise to the central Iceland basin aboard the Royal Research Ship Discovery during the late summer of 2007, after the main bloom had ended. Measurements of phytoplankton growth, calcification (calcite plate formation), and coccolithophore abundance were made during the trip.

"Our study had two main aims - firstly to measure cell calcification and its variability, and secondly to make comparison between these and environmental conditions so as to help identify those factors that control coccolithophore growth and calcite production during non-bloom conditions," said Dr Alex Poulton of NOC.

The researchers also assessed the dynamics of the coccolithophore community in the central Iceland Basin, in terms of its production, composition, and contribution to the total phytoplankton community.

The researchers found relatively low numbers of coccolithophores and that most of the calcite in the was in the form of detached coccoliths rather than whole cells.

From their observations and measurements, along with on and calcite concentration, they estimated that coccolithophores accounted for around 10-20 per cent of biological production and phytoplankton biomass in sunlit surface waters. Emiliania huxleyi was the dominant coccolithophore present, and both productivity and calcification decreased with depth.

Experiments aboard the ship revealed that both the total number of coccolithophore cells and the variation of calcification rates by individual cells controlled the total amount of calcification by the coccolithophore community. But what factors control this production?

Comparison of cellular calcification rates with the environmental factors currently associated with coccolithophore blooms gave no clear pattern, including sunlight, mixed layer depth, and the availability of nutrients such as nitrate and phosphate.

Instead, the researchers suspect that micronutrients such as iron play an important role in controlling coccolithophore growth and calcification.

This is supported by independent iron enrichment experiments performed by researchers led by Dr Maria Nielsdottir of the University of Southampton's School of Ocean and Earth Science (SOES), based at NOC. Their results, which were published in 2009, indicate that iron availability may exert a strong control on coccolithophore growth and calcification.

Furthermore, Poulton is joining a research cruise this summer (led by Prof. Eric Acterberg of SOES with colleagues from NOC and Portsmouth University) to the North Atlantic, again to examine in greater detail the conclusions of the first two studies - specifically the role of iron in calcification, and the role of zooplankton grazing in controlling coccolithophore numbers.

Finally, by coccolithophores is likely to be affected by ocean acidification caused by increased levels of atmospheric carbon dioxide and its absorption by the oceans.

"Understanding the ecology and production of coccolithophores under both bloom and non-bloom conditions is crucial for assessing how climate change and ocean acidification will affect coccolithophore communities and the important biogeochemical cycles that they contribute to," said Poulton.

Explore further: Magnitude-7.2 earthquake shakes Mexican capital

More information: Alex J. Poulton, A. J., Charalampopoulou, A., Young, J. R., Tarran, G. A., Lucas, M. I. & Quartly, G. D. Coccolithophore dynamics in non-bloom conditions during late summer in the central Iceland Basin (July-August 2007). Limnol. Oceanogr., 55(4), 1601-1613 (2010).

Provided by National Oceanography Centre, Southampton

5 /5 (1 vote)

Related Stories

Image: Phytoplankton Bloom in the North Atlantic

May 26, 2010

(PhysOrg.com) -- Late May 2010 brought peacock-hued swirls of blue and green to the North Atlantic. The iridescent waters formed a giant arc hundreds of kilometers across, extending from west of Ireland to ...

Ocean iron and CO2 interaction studied

Apr 26, 2007

A French study suggested that iron supply changes from deep water to the ocean's surface might have a greater effect on atmospheric CO2 than thought.

Summer Storms Could Mean More Dead Zones

Jul 11, 2008

(PhysOrg.com) -- It's summertime and people are flocking to the coasts around the country. But when summer storms arrive, it's not only beach-goers who are affected; the rains can also have an impact on living ...

Recommended for you

Magnitude-7.2 earthquake shakes Mexican capital

Apr 18, 2014

A powerful magnitude-7.2 earthquake shook central and southern Mexico on Friday, sending panicked people into the streets. Some walls cracked and fell, but there were no reports of major damage or casualties.

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

TegiriNenashi
not rated yet Jun 30, 2010
A rare article that is coherent, more that 3 paragraph long, and not PC skewed by rules of the game at this Physorg section.

More news stories

China says massive area of its soil polluted

A huge area of China's soil covering more than twice the size of Spain is estimated to be polluted, the government said Thursday, announcing findings of a survey previously kept secret.

UN weather agency warns of 'El Nino' this year

The UN weather agency Tuesday warned there was a good chance of an "El Nino" climate phenomenon in the Pacific Ocean this year, bringing droughts and heavy rainfall to the rest of the world.

Airbnb rental site raises $450 mn

Online lodging listings website Airbnb inked a $450 million funding deal with investors led by TPG, a source close to the matter said Friday.

Health care site flagged in Heartbleed review

People with accounts on the enrollment website for President Barack Obama's signature health care law are being told to change their passwords following an administration-wide review of the government's vulnerability to the ...