Growth potential, production efficiency and annual production of marine benthic naked amoebae (gymnamoebae) inhabiting sediments of the Clyde Sea area, Scotland

A substantial population oi naked amoebae is present in marine sediments, but little is known about their role in benthic microbial food webs. Central to elucidating this role is an understanding of their growth potential, and the present study measures growth rates of 10 species of naked amoebae isolated from benthic sediments in the Clyde Sea area, Scotland, UK. Across the range of species and temperatures examined (5 to 20 degrees C), generation times varied from 11 to 130 h. Temperature had a marked effect on growth rate, with the slowest rates al the lowest temperature. Temperature also generally influenced the mean cell volume of cells, with many species showing increased cell size at lower temperatures. Consequently, it was possible to compute a significant regression of log(1.0) generation time (G, h) against log(10) cell volume (V, mu m(3)) using the combined data regardless of temperatures [log G = 0.231 logV + 1.010 (p = 0.004)]. This relationship may have application in the estimation of generation times oi naked amoebae with 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 fine 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).