SINKING RATE OF LORICAE OF SOME COMMON TINTINNID CILIATES

Sinking rate of empty loricae of seven tintinnid species was measured in settling chambers. The sinking rates normalized for 3% NaCl solution at 20 degrees C are 0.25-2.08 m day(-1) for five hyaline loricae and 1.90 and 15.9 m day(-1) for two agglutinated loricae. Positive relationships between sinking rate and size of hyaline loricae such as volume, surface area and nominal diameter were established, which favour the practical estimation of sinking rate of empty loricae discarded by natural tintinnid populations by measuring size composition. The slower sinking rate of hyaline loricae, compared with that of diatoms, indicates their availability as indicators of particular water masses in the ocean. Loricae incorporated into faecal pellets of zooplankton and marine snow also indicate the origin of these sinking particles.