Biodiversity and biogeography of the atmosphere

Abstract

The variation of life has predominantly been studied on land and in water, but this focus is changing. There is a resurging interest in the distribution of life in the atmosphere and the processes that underlie patterns in this distribution. Here, we review our current state of knowledge about the biodiversity and biogeography of the atmosphere, with an emphasis on micro-organisms, the numerically dominant forms of aerial life. We present evidence to suggest that the atmosphere is a habitat for micro-organisms, and not purely a conduit for terrestrial and aquatic life. Building on a rich history of research in terrestrial and aquatic systems, we explore biodiversity patterns that are likely to play an important role in the emerging field of air biogeography. We discuss the possibility of a more unified understanding of the biosphere, one that links knowledge about biodiversity and biogeography in the lithosphere, hydrosphere and atmosphere.

Figure 1.

Simulated concentration (10³ m ⁻³) of 1 µm bacteria in near-surface air based on an adjusted general circulation model (Burrows et al. 2009a).

Figure 2.

Isolation of microbes from the atmosphere. Shaded portions of the columns correspond to the altitude from which the organisms were sampled by a meteorological rocket and isolated in the laboratory. The first column depicts the altitude at which dust particles were sampled and detected (adapted from Imshenetsky et al. (1978)).

Figure 3.

The six major air cells of the Earth's atmosphere (source: NASA).