MICROBIAL ECOLOGY: APPROACH AND PROBLEMS

The first observations of bacterial populations in the deep sea were made in 1882 and 1883 during the cruises of the ‘Travailleur’ and ‘Talisman’ (Certes, 1884). Although observations continued to be made, no data became available on rates of deep-sea bacterial metabolism until the early 1950s. Morita & Zobell (1955) and Zobell and Morita (1957) demonstrated that bacterial activity in deep-sea sediments was very low. This was not thought surprising as the low temperature, high pressure and low nutrient levels known to occur in the deep sea did not present a particularly favourable milieu for bacterial growth. All bacterial activity in the deep sea (with the exception of chemosynthesis which is limited to hydrothermal vents and sulphide-rich cold seeps – see Chapter 15) is heterotrophic, requiring an energy source in the form of organic matter ultimately derived from surface production.

In the last 20 years there has been a great effort in understanding the bacterial ecology of the deep sea. This effort was stimulated by two unrelated events. The first was the accidental sinking of the submersible ‘Alvin’. The submersible was swamped by a wave on launching. The crew escaped but left behind their lunch which consisted of bouillon, bologna sandwiches and apples. When ‘Alvin’ was recovered one year later, the scientists were amazed to find the food was still in good condition (see photograph in Jannasch, 1978) within the flooded pressure sphere, but it soon rotted even in a refrigerator at atmospheric pressure (Jannasch et al., 1970).