AMT19, the second in the series of cruises funded by the Oceans 2025 programme set sail from the UK on 13 October 2009 and arrived in Chile on 1 December 2009.  The principal scientist was Andy Rees from the Plymouth Marine Laboratory.

This was the longest voyage to date covering an immense 8500 miles continuing the long-term collection of biological and chemical observations of the remote Atlantic ecosystem. This included research examining the impact of ocean acidification on the activity of specific marine bacteria that are an important part of the global nitrogen cycle. New techniques were developed to determine concentration levels and microbial turnover of compounds that are important in atmospheric chemistry and provide a carbon source for marine bacteria and phytoplankton. Results from this research will increase our understanding of the processes that occur in the Atlantic Ocean and will eventually feed into ecosystem models to help forecast global change.