Current status of the microbiology of the deep-sea

An explanation, which includes the depth of the water, sample site, sample material, energy availability, incuba tion conditions, and the age of the water mass, is given for the apparent discrepancy in the data obtained on the microbiology of the deep-sea. The rate of microbial activity is related to the availability of energy in the sys tem. Low rates of microbial activity in environments lacking sufficient energy helps prevent the depletion of the energy supply needed for all organisms in the deep-sea especially when the age of the water mass is taken into consideration. Background literature Low bacterial populations were demonstrated to be present in the red clay and globerigerina ooze during the Mid-Pacific Expedition of 1950 (1). Based on the deposi tion rate of red clay it appears that bacteria in the deeper varves of the cores of red clay were very old which implies that the bacteria in the cores had the ability to survive long period of time by one mechanism or another. Higher populations of bacteria were observed in samples taken from the various Deeps and Trenches during the Galathea Deep Sea Expedition (2). In both cases slow bacterial growth rates were observed. For example, an enrichment culture of sulfate reducing bacteria from the Weber Trench took approximately one year to show positive signs of sulfate reduction at 715 atm and 5 C; the controls at 1 atm and 5 C remained negative for an incubation period of three years. Bottom water and sediment containing a mixed bacterial population from the Japan Trench (9,500 m) was examined by Seki and ZoBell (3) for 14C-carbon dioxide uptake. Bacterial carbon dioxide uptake in sediment and bottom water was found to range from 0.70 to 9.4 /xg C/kg/day and 0.22 to 0.59 fxg C/liter/day respectively. The amount of carbon dioxide in the samples were also measured. However, it should be noted that these experiments were conducted at 1 atm. The values, if performed in situ, would probably be much lower. Jannasch et al. (4) examined food materials from the sunken and recovered submersible Alvin. The food mate