GROWTH-POTENTIAL, PRODUCTION EFFICIENCY AND ANNUAL PRODUCTION OF MARINE BENTHIC NAKED AMEBAS (GYMNAMOEBAE) INHABITING SEDIMENTS OF THE CLYDE-SEA AREA, SCOTLAND

A substantial population oi naked amoebae is present in marine sedimen ts, but little is known about their role in benthic microbial food web s. Central to elucidating this role is an understanding of their growt h potential, and the present study measures growth rates of 10 species of naked amoebae isolated from benthic sediments in the Clyde Sea are a, Scotland, UK. Across the range of species and temperatures examined (5 to 20 degrees C), generation times varied from 11 to 130 h. Temper ature had a marked effect on growth rate, with the slowest rates al th e lowest temperature. Temperature also generally influenced the mean c ell volume of cells, with many species showing increased cell size at lower temperatures. Consequently, it was possible to compute a signifi cant regression of log(1.0) generation time (G, h) against log(10) cel l volume (V, mu m(3)) using the combined data regardless of temperatur es [log G = 0.231 logV + 1.010 (p = 0.004)]. This relationship may hav e application in the estimation of generation times oi naked amoebae w ith known cell volumes. Gross growth efficiencies ranged between 11.7 and 79.7% with an overall mean of 36.1%. The growth data were combined with published information on the abundance of marine benthic amoebae to provide a first estimate of annual production by this group in fin e marine sediments. Annual production estimates were between 7.60 and 15.8 kJ m(-2) yr(-1), implying that annual consumption of bacteria by naked amoebae is of the order 21.1 to 43.8 kJ m(-2) yr(-1).