Beautiful Diatoms: Pattern for stable construction

AWI publication in ‘Nature’
In February 2003, scientists from the Alfred Wegener Institute (AWI) published new results concerning the structure and material properties of diatoms in the journal "Nature". These single-celled marine algae are responsible for the majority of oxygen and biomass production in the oceans. Since their discovery around 170 years ago they have been admired for their beauty and diversity. It has now been shown that their fantastical shapes have an ecological purpose.
The outer ‘shells’ of the diatoms can withstand forces of several hundred micronewtons (equivalent to several hundred tonnes per square metre) and protect the algae against a broad spectrum of organisms (zooplankton) which try to break them up.Despite their high mechanical strength, they are exceptionally light and use their building element silicon, which is in short supply in the water, economically. A light construction is necessary since silicon is relatively heavy and means extra ballast for the algae (phytoplankton) which float in the water.

Material and structure
The new results at AWI followed from close collaboration with biophysicists at the Technical University of Munich and the Jülich Research Centre as well as naval architects at Bremen College. The scientists subjected individual algae to micro-mechanical strain tests. The loading applied by various clamps was simulated using modern calculation methods (finite element model) on a computer. It was found that the sturdiness of the shells results from the highly complex, flowing forms and the particular material properties of the vitreous silica. The bonding between silicon and carbon in the shell has enabled the diatoms to develop numerous different forms during the course of their evolution. Among them are some forms which bear remarkable similarity to our technical constructions and architecture.

Implications for research
“These experiments with diatom shells mark the beginning of a series of fundamental new discoveries about the evolution of marine communities”, says Dr Christian Hamm from AWI.
The diversity in shell architecture can be related to adaptation to the mechanical loading of various forms of clamps. The algae clearly defend themselves against grazing pressure from zooplankton. This development also has consequences for the nutrient budget in the oceans, particularly for the uptake and storage of carbon and silicon in the sediment. The shells of particularly robust species survive in the sediments and can be used in the reconstruction of past environmental conditions. These discoveries serve not only climate research but also supply information about biological inter-relationships and are useful for marine ecology.
“The AWI is earning a place at the forefront of international research of diatoms and their role in the global carbon cycle” explains Prof. Victor Smetacek, head of plankton research at AWI.

Model for technology
Applied to technical problems in which stability and lightness are particularly important, architecture based on diatom shells could allow exceptionally economical use of building materials and fuel. This is of interest, for example, in the aerospace and transport industries. The mechanically stable structures offer not only beauty but also the potential for useful applications in the coupling of design and functionality.

Bremerhaven, 19.2.2003