A bacterial bioassay for measuring the copper‐chelation capacity of seawater 1

A relatively simple 14C tracer bioassay technique is described which uses a copper sensitive bacterium to measure the copper chelation capacity of seawater. Known increments of ethylenediaminetetraacetic acid are used to evaluate decreased bacterial inhibition accompanying reduced cupric ion activity. Ultraviolet irradiation and selective filtration of natural seawaters indicate that organic assemblages having molecular weights <10,000 are principally responsible for copper chelation. Copper chelation capacities ranged from 3 µg·liter−1 of copper for oligotrophic to 40 µg liter−1 of copper for eutrophic marine waters.