Diatoms: the jewels of palaeoclimatology

Jack Wilkin (UK) My PhD at the University of Exeter focuses on using micropalaeontology and various geochemical methods from Holocene marine sediment cores, to try to find out how the climate of South Georgia has changed over the past 15,000 years. One of the microfossil groups I’m using to achieve this is diatoms (Fig. 1). Fig. 1. Some of the different diatoms I’m working on from the Southern Ocean:(a) Actinocyclus actinochilus; (b) Thalassiosira lentiginosa (the thick hexagonal microfossil is a silicoflagellate) (c) Eucampia antarctica; (d) Navicula sp.; e). Fragilariopsis kerguelensis; (f) Rhizosolenia antennata f. antennata.(Photographs courtesy of Dr Claire Allen (British Antarctic Survey). (a)-(c), (f) = centrics, (d)-(e) = pennates (only raphed forms are pictured here).) Diatoms are microscopic algae that play a vital role in marine ecosystems. They have circular or elliptical to rod-like shapes and are perforated by minute apertures called areola. They are divided into two orders: the Pennales and the Centrales. Diatoms can reproduce both sexually and asexually, using a unique “shrinking division” form of a sexual reproduction called binary fission. They are photosynthetic and form the basis of food chains in many aquatic ecosystems. Diatoms also have a wide range of geological applications, especially in palaeoclimate studies. What do diatoms look like? Diatoms are usually colonial, photosynthetic, single-celled algae, made of biogenic silica, with an estimated 20,000 to two million species. One could imagine them as microscopic plants that live inside tiny glass greenhouses, stacked on top of each other. They form as iliceous shell, … Read More