Dopamine release by the green alga <Emphasis Type="Italic">Ulvaria obscura</Emphasis> after simulated immersion by incoming tides

Ulvaria obscura, a prominent component of green tide blooms in Washington, is unique among macroalgae because it contains dopamine. To examine dopamine release by U. obscura following simulated low tides, we conducted 6 field experiments in which algae were emersed for 75 min and then immersed in filtered seawater (FSW). Dopamine was measured in algal tissues prior to emersion and 3 h after immersion and in seawater for 3 h following immersion. In our experiments, algae released 7–100% of their tissue dopamine, resulting in average seawater concentrations of 3–563 μM. In 5 of 6 experiments, seawater dopamine concentrations were highest immediately after immersion, and then decreased over time. The percentages of dopamine released were not correlated with tissue dopamine concentrations, but were positively correlated with solar radiation during emersion. The release of dopamine, which is both cytotoxic and genotoxic, may explain the negative effects of U. obscura exudates on marine organisms.