Inexpensive flow microcalorimeter for measuring heat production of attached and sedimentary aquatic microorganisms.

A relatively inexpensive flow microcalorimeter is described which is capable of detecting heat outputs as low as 3 muW (precision, +/-2%). Its use is illustrated on river epilithon (0.8 to 6.8 muW cm), river sand (9.8 muW cm), and marine sand (15.3 muW cm); however, it could be used to detect the heat output from any biotic material over which a flow of water can be passed, provided that such an action would not be disruptive to chemical and biological equilibria.