Abstract
Macrocystis pyrifera (Giant Kelp), a dominant macroalgal species in southern California, produced 171 ng per g fresh wt (gfwt) per day of CHBr 3 and 48 ng gfwt −1 d −1 of CH 2 Br 2 during laboratory incubations of whole blades. Comparable rates were measured during in situ incubations of intact fronds. Release of CHBr 3 and CH 2 Br 2 by M. pyrifera was affected by light and algal photosynthetic activity, suggesting that environmental factors influencing kelp physiology can affect halomethane release to the atmosphere. Data from H 2 O 2 additions suggest that brominated methane production during darkness is limited by bromide oxidant supply. A bromine budget constructed for a region of southern California indicated that bromine emitted from the use of CH 3 Br as a fumigant (1 × 10 8 g Br yr −1 ) dominates macroalgal sources (3 × 10 6 g Br yr −1 ). Global projections, however, suggest that combined emissions of marine algae (including microalgae) contribute substantial amounts of bromine to the global cycle, perhaps on the same order of magnitude as anthropogenic sources.