Ciliate growth rates from Plymouth Sound: comparison of direct and indirect estimates

Abstract

Thein situgrowth rates of marine planktonic ciliates from Plymouth Sound were determined after fractionating the natural community into several size categories to remove predators of different sizes. Total communityin situgrowth rates varied from 0·01 to 0·57 d−1according to fractionation treatment, with the four most abundant taxa, comprising three species ofStrombidium, andMesodinium rubrum, achieving maximumin situgrowth rates of between 0·41 and 0·68 d−1. These values are approximately half the maximum theoretical rates calculated indirectly using an equation which relates ciliate growth to cell size and temperature. Given the conservative nature ofin situgrowth rate measurements, the growth rates reported here appear appropriate for a natural ciliate community growing within a nutritionally favourable environment.