ABUNDANCE OF THE GIANT DIATOM ETHMODISCUS IN THE SOUTHWEST ATLANTIC OCEAN AND CENTRAL PACIFIC GYRE

Abstract

Abundance of the giant diatom Ethmodiscus was determined in samples from the central Pacific gyre and southwest Atlantic Ocean/Caribbean Sea. Pacific Ocean abundance averaged 0.08 cells m⁻³ at the surface. Atlantic Ocean/Caribbean Sea abundance ranged from 0.03–4.7 cells m⁻³ with extensive (150-fold) spatial and temporal variability. Average abundances for three cruises over 2 yr were 0.14, 0.77, and 1.85 cells m⁻³. Ethmodiscus rex (Rattray) Wiseman & Hendey was the dominant Ethmodiscus species in all samples from the Bahamas to Carrie Bow Cay, Belize. Apparently viable cells were noted in both upward and downward facing sediment traps at 5400 m in the Pacific Ocean. The origin of Ethmodiscus oozes in deep-sea sediments is briefly discussed in relation to these new data.