Phytoplankton bloom

According to research carried out, the impact of the 2010 eruption has had a significant but short-lived effect on the biology of the North Atlantic Ocean and the findings have been published in the journal Geophysical Research Letters.



In 2007 the team showed that following a large spring bloom, phytoplankton – microscopic plants that form the basis of the marine food chain in the Iceland Basin - became growth-limited because of a lack of dissolved iron, a vital component in their productivity. Understanding ocean productivity is essential as Phytoplankton blooms remove carbon dioxide, a greenhouse gas from the atmosphere.



The scientists – from University of Southampton, based at National Oceanography Centre, Southampton (NOCS) – together with colleagues from the University of Cape Town and the Norwegian Institute for Air Research conducted the three research voyages in 2010 to investigate ocean productivity and to find out if the volcanic ash inputs from Eyjafjallajökull had supplied sufficient iron to sustain the spring blooms longer than usual. The initial voyage led by NOCS’ Dr Mark Moore, allowed the team to observe and directly sample the large volcanic ash inputs to the Iceland Basin. In return voyages, the team assessed how phytoplankton blooms developed following the ash inputs looking at ash and dust in the atmosphere, and nutrients in the ocean.

Onboard RRS Discovery

Chief scientist for the summer research cruise and lead author of the paper, Professor Eric Achterberg from the University of Southampton, highlighted the significance of the process in this part of the world ocean saying: "The high latitude North Atlantic Ocean is a globally important ocean region, as it is a sink for atmospheric carbon dioxide, and an area where deep water formation takes place. A limit to the availability of iron in this region means that the ocean is less efficient in its uptake of atmospheric carbon dioxide."



Biological experiments performed by the team found that the five-week eruption supplied dissolved iron to an ocean region of the North Atlantic of up 570,000 square kilometres, increasing the number of phytoplankton cells stimulating phytoplankton growth. The effects of the volcanic ash inputs were nevertheless short-lived as the extra iron resulted in the rapid removal of biological nitrate, causing nitrogen limitation of the phytoplankton population.



Professor Achterberg, who is Head of Ocean Biochemistry and Ecosystems Research Group, says: "The additional removal of carbon by the ash-stimulated phytoplankton was therefore only 15 to 20 per cent higher than in other years making for a significant, but short-lived change to the biogeochemistry of the Iceland Basin."

Published in the journal Geophysical Research Letters.