Relationships between lorica volume, carbon, nitrogen, and ATP content of tintinnids In Narragansett Bay

Abstract

Lorica volume, carbon, nitrogen, and ATP content were measured in nine species of tintinnid ciliates spanning a size range of two orders of magnitude. Tintinnid carbon was linearly related to both lorica volume and ATP content. The mean C:ATP ratio was 65. Tintinnid ATP as a percentage of total ATP in the <153 μm fraction averaged 7% over an annual cycle in Narragansett Bay. It is concluded that ATP is a useful indicator of living phytoplankton carbon in pre-screened, small-volume samples during periods of moderate to high phytoplankton biomass, but that protozoan microzooplankton interference is significant when phytoplankton standing stocks are low.