Impact of volcanic ash on anammox communities in deep sea sediments

Subaerial explosive volcanism contributes substantial amounts of material to the oceans, but little is known about the impact of volcanic ash on sedimentary microbial activity. We have studied anammox communities in deep sea sediments near the volcanically active island of Montserrat, Lesser Antilles. The rates of anammox and denitrification in the sediments were measured using (15)N isotope pairing incubation experiments, while 16S rRNA genes were used to examine anammox community structures. The higher anammox rates were measured in sediment containing the lower accumulation of volcanic ash in the surface sediments, while the lowest activities were found in sediments with the highest ash deposit. 16S rRNA gene analysis revealed the presence of 'Candidatus Scalindua spp.' in the sediments. The lowest diversity of anammox bacteria was observed in the sediments with the highest ash deposit. Overall, this study demonstrates that the deposition of volcanic material in deep sea sediments has negative impacts on activity and diversity of the anammox community. Since anammox may account for up to 79% of N2 production in marine ecosystems, periods of extensive explosive volcanism in Earth history may have had a hitherto unrecognized negative impact on the sedimentary nitrogen removal processes.

The Montserrat Volcano Observatory: its evolution, organization, role and activities

The Montserrat Volcano Observatory (MVO) is a statutory body of the Government of Montserrat and is the organization responsible for volcano monitoring operations on the island. It was formed shortly after the first phreatic explosions from Soufrière Hills Volcano occurred on 18 July 1995, and evolved from a hastily created, interim entity to a fully established volcano monitoring operation. Participating scientific teams have been drawn mainly from the Seismic Research Unit of the University of the West Indies, the US Geological Survey, the British Geological Survey and universities from various countries including the USA, UK, France and Puerto Rico. Despite its hurried inception, the MVO has been able to provide timely, high quality hazard advice to the civil authorities and has maintained an exceptional documentary record of all scientific aspects of the eruption. Its public education and information efforts have been extensive and there have been unusually high levels of interaction between scientists and the civil authorities, and between scientists and the public, both within Montserrat and outside in the wider world. The experience of setting up and running the MVO, under difficult and stressful conditions, has exemplified the advantages of teamwork and flexibility within monitoring operations and the benefits of openness and clarity in public interactions. Novel techniques have been applied to the appraisal of hazards and advances in scientific understanding have proved invaluable for risk assessment and management.