Leanne Armand (20 February 1968 – 4 January 2022) was an Australian professor of marine science. She was an expert in the identification of diatoms in the Southern Ocean. She was known for her contributions to the understanding of past Southern Ocean dynamics and sea ice as a result of her knowledge of diatom distributions and ecology. Her research focused on the distribution of diatoms, a single-cell microscopic phytoplankton, within the Southern Ocean. Different species of diatoms inhabit different regions of the ocean, depending on the physical characteristics (e.g. temperature, salinity and nutrients) of the water mass. Understanding diatom distributions and how their skeletons are preserved in the fossil record contained within sediment cores taken from the ocean floor can provide information about past climate regimes, including ocean temperatures and sea ice extent. Armand also studied diatoms in the Southern Ocean near Kerguelen and Heard Islands to examine their role in the transport of carbon to the ocean floor after their annual spring bloom. Armand was also a strong advocate for Women in Science and was a mentor and role model to many Australian women in marine and geo-science. Early life Armand was born in Adelaide, South Australia on 20 February 1968. She spent a lot of time as a child at the nearby beaches, collecting seashells and using them to set up 'museums' at home along with other bits and pieces. Armand's interest in biology was nurtured by excellent high school teachers at St Mary's College, Adelaide, where she won the Green Biology prize for best student. In Year 12 she was selected to participate in a Rotary exchange to a high school in Arkansas, U.S.A. Education and career Armand studied biology at Flinders University for her undergraduate degree and, after one false start on an Honours project in Alice Springs, finished an Honours degree at the Australian National University studying vertebrate fossils from Teapot Creek in the southern Monaro region of New South Wales, under the guidance of Australia's grandfather of vertebrate fossils, William David Ride. Specializing in micropalaeontology, the study of tiny fossils, for her PhD studies, Armand examined the fossilised remains of diatoms found in deep sea sediment cores. She used them to interpret past climate conditions by looking at which types were indicative of warmer or cooler temperatures, and how this represented the advance or retreat of sea ice. Armand's PhD project was a joint