Figure 3.

(a) The effects of extracellular extracts of K. brevis cultures exposed to seawater or competitor culture on the growth of nine competitor species. Each bar represents the maximum cell density of a phytoplankton species normalized to the growth of the same species exposed to a seawater control. White bars, extracellular extract of K. brevis; grey bars, extracellular extract of K. brevis and competitor. (b) Six independent tests of the growth of S. costatum exposed to the same treatments as (a). Asterisks indicate a significant allelopathic effect relative to seawater control, and plus signs indicate a significant difference between treatments for a given species (n=5–8).