The overall aim of the Atlantic Meridional Transect programme is to quantify key biogeochemical and ecosystem processes and their inherent variability over extended temporal and spatial scales in the Atlantic Ocean. This is achieved by executing an annually repeated meridional transect through
contrasting oceanic provinces, ranging from oligotrophic deep blue waters, to highly productive shelf seas. The AMT is funded as part of the Natural Environmental Research Council’s National Capability. Its specific objectives are:

• To quantify the nature and causes of ecological and biogeochemical variability in planktonic ecosystems.
• To quantify the effects of this variability on nutrient cycling, on the export of organic matter and on the air-sea exchange of climate active gases.
• To construct multi-decadal, multidisciplinary ocean time-series which are integrated within a wider ―Pole-to-pole observatory.
• To provide essential sea-truth validation for current and next generation satellite missions.
• To provide essential data for global ecosystem model development and validation; which in turn provides the world with its climate-change forecasting capability.
• To provide a valuable, highly sought-after and unique training arena for the next generation of UK and international oceanographers

AMT29 research cruise (DY110)

The AMT29 research cruise (DY110) set sail from Southampton on October 13th, 2019 aboard the Royal Research Ship Discovery and arrived in Punta Arenas, Chile, on November 25th, 2019. The figure below presents the final cruise track overlaid on the climatological chlorophyll concentration
estimate by the OC-CCI product for November. The highlights of AMT29 were as follows:

• 55 CTD profiles measuring key physical and biogeochemical parameters including: temperature, salinity, chlorophyll, oxygen, nutrients, pH, alkalinity, plankton abundance, respiration, genetics and microbial dynamics.
• Daily sampling down to 2000 m in an attempt to resolve the Antarctic Intermediate Waters (AAIW). AAIW is an important water mass is thought to sustain primary production in a large fraction of the ocean. Sampling included measurements of oxygen, nutrients, pH, DIC/TA, REEs, PFAAs, Cr isotopes, flow cytometry and tintinnids.
• Continuous underway temperature, bio-optical and biogeochemical measurements covering an almost 100° range in latitude and vastly contrasting ocean biomes.
• Vertical net hauls to determine the abundance of different species of zooplankton and larger phytoplankton.
• Optics rig deployments to measure optical properties of the upper 500 m of the water column.
• Weather balloon launches.
• Test of two new instruments (new FFRF and new chlorophyll-a meter). AMT as an ideal platform to test instrumentation over a wide range of environments.
• First measurements of depth profiles and sea-spray aerosol enrichment of perfluoroalkyl acids (important to predict environmental transport of contaminants and to understanding the chemical composition of sea-spray aerosol)
• Continuous underway measurements of optical properties, sea-surface temperature, radar backscatter and gas fluxes to validate products from satellite sensors (ESA, JAXA and NASA).
• Collected samples for single-cell phytoplankton stoichiometry at the Atlantic basin scale.
  Incubator experiments to better understand the interactive effect of temperature and nutrients availability in different phytoplankton and bacteria communities along the transect.
• Wide suite of complementary measurements to determine the carbon fluxes (net and gross primary production, net community production, size-fractionated photosynthesis irradiance curves, pigments, etc.) due to phytoplankton and bacteria in the surface sunlit layer.
• New high-resolution meridional cross section of Rare Earth Elements (REE) specifically targeting the water masses of the upper water column to investigate the role of biological features and processes, if any, on the REE distribution. This is important because RREs can be used to investigate processes such as particle scavenging, dust dissolution, river input, pore-water diffusion, etc.
• Flow-cytometry and Coulter-counter measurements as well and sample collection to characterize the distribution and abundance of Archea, bacteria, pico- and nano-eukaryotic phytoplankton, and to investigate the contribution of phytoplankton to the particle size distribution.
  Deployment of six NOAA-PMEL Deep-Argo floats contributing to the regional pilot array in the Brazilian Basin and several additional core Argo floats for the UKMO.
• Recovery of a deep (5000 m) sediment trap mooring in the South Atlantic oligotrophic gyre for the National Oceanography Centre, UK, which had previously been deployed in October 2018, and the construction and deployment of a new sediment trap mooring at the same location.
• Participation of 20 research scientists from 10 institutes and of 12 different nationalities (Austria, China, France, Germany, India, Italy, Portugal, Russia, Spain, Sweden, UK, Venezuela)

Link to full study: The AMT29 research cruise (DY110)

Phytoplankton monitoring

AMT29 was used to develop LabSTAF, now the world’s leading portable instrumentation option for Phytoplankton primary productivity.

• Benchtop instrument to measure primary productivity using fluorescence, giving data for over 50 useful parameters within 15 minutes
• LabSTAF includes a peristaltic pump, solenoid unit and flow-through stirrer unit to provide for mixing, sample exchange and a periodic cleaning cycle.
• Data from LabSTAF is interpreted and analysed internally in the included Surface Go