Year: 1993
Type: article
Abstract: 2 3 4 ~h was determined in the dssolved (< 0.1 pm), bacterial (0.1 to 1.0 pm) and 2 larger particulate pools (1 to 5 pm and >5 um) at 5 or 6 depths in the upper 120 m of the water column at a station (31'51.6'N, 119"31.9'W) in the Southern California Bight during October 1989 and July 1990.Depth profiles of bactenal abundance and chlorophyll a were also measured.The bactenal fraction had high volume concentrahon factor (VCF: 1 to 4 X 106) and the highest estimated *"Th/C ratio of all size fractions (5.1 and 5.5 nCl gC-l).The VCF for 234Th scavenging by bacteria determned in a microcosm experiment (containing a 2 pm filtrate of seawater from Scripps pier and spiked with 2 3 4 ~h ) was on the order of 7 X 106 Both the bacteria fraction and > 5 pm fraction had 2 3 4 ~h / C ratios comparable to that computed for the colloidal fraction.Sequential transfer of 2 3 4 ~h (truly dissolved 234Th 4 disperse colloids + suspended particles + sinking particles) alone does not explain the observed high 234Th/C ratio in the bacterial and the large particulate fractions.We propose that the abundant and highly 234Th-reactive colloids (which occur bound to the surfaces of free and particle-bound bacteria in addition to their occurrence in the disperse phase) contribute substantially to efficient scavenging of 2 3 4 ~h by bacteria as well as colonized particles of all sizes.The contribution by bound colloids may vary with the physiological states of bacteria and phytoplankton and their state of aggregation.This unstructured flow model has implications for models which use 234Th/238U disequilibriurn as an indicator for downward flux of particles in the ocean.
Source: Marine Ecology Progress Series
DOI: 10.3354/meps096109
Language: English
Subfield: Oceanography
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: bronze
Funder: National Science Foundation
OpenAlex ID: W2017566712