The RV Investigator is currently undertaking oceanographic research along the 110°E meridian off Western Australia as part of the second International Indian Ocean Expedition. The voyage is led by Professor Lynnath Beckley of Murdoch University and the research is supported by a grant of sea time on RV Investigator from the CSIRO Marine National Facility.

Date: May 19, 2019	Time: 1200 AWST
Latitude: 36.5°S	Longitude: 110°E
Wind direction: NNW	Wind speed: 27 knots
Swell direction: SW	Depth: 5365 m
Air temperature: 16°C	Sea temperature: 15.3°C
Notes: It's a bit rainy and soggy today but this is not dampening the spirits of the scientists aboard RV Investigator! This morning we completed our deepest CTD to date, at over 5 km depth.

Phytoplankton-the microscopic plants inhabiting the surface lit layers of the ocean are among the most diverse group of micro-organisms inhabiting the planet. They comprise eight main groups, have individual cell sizes from less than a micron to about one millimeter (see Figure below) and play various roles in the ecosystem. As they photosynthesize, they collectively represent the first link of the marine food web. All phytoplankton contain the pigment chlorophyll-a, which is measured to ascertain phytoplankton biomass. As well as chlorophyll-a, each phytoplankton group has other accessory pigments, which can be used to determine phytoplankton groups or size classes. Phytoplankton are also responsible for the transfer of carbon dioxide from the atmosphere to the deep layers of the ocean and ultimately the sediments of the sea floor.

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