Pressure, Temperature, Salinity, Density and Chemistry of the Oceans
Water is always incompressible, and this is important to microbes. It will not expand very much inside them if they are brought to the surface from deep waters, so they tend not to burst from a slow release of pressure, though a sudden change of pressure may cause rupture. Further, the likelihood of rupture depends very much on the size and complexity of the organism, and on the presence or absence of gases in the cells or organs. The smaller the organism, the easier it is for equilibrium to be adjusted between the interior of the cell or cells and the external world; in addition, the ratio of surface to volume is important since the larger the surface, the more room there is for things to get in and out. This is especially true of gases. We should expect what we find, that single-celled microbes are least affected by sudden pressure change. The hydrostatic pressure in the seas (or elsewhere for that matter) increases about 1 atmosphere (15 1bs per square inch) for every 30 feet of depth. Thus, in the deepest oceans, the pressure will be 1,000 atmospheres or 15,000 pounds per square inch (p.s.i.). It was long thought that nothing could live at such pressures. But by 1820 living creatures had been brought up from a depth of 100 fathoms, and by 1912 a rich fauna of abyssal fishes called invertebrates was known. The Danish research-ship Galathea specialised in the abyssal fauna and added much new information.
KeywordsHydrostatic Pressure Gulf Stream Isopycnal Surface Rich Fauna Giant Squid
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