Macrophytic marine red algae are a unique source of novel and bioactive terpenoids, including halogenated monoterpenes. Biomass and halogenated monoterpene production by regenerated microplantlet suspension cultures derived from the red alga Ochtodes secundiramea were studied within a perfusion airlift photobioreactor. Photobioreactor cultivations were carried out at 26degreesC, 140 muE m(-2)s(-1) light intensity, 0.3 air L-1 culture min(-1) aeration (3500 PPM CO2), and ESS/seawater medium perfusion rate of 0.2 L medium L-1 culture d(-1). Macronutrient concentrations in the perfusion medium were adjusted to provide nitrate delivery rates of 0.0063, 0.077, and 0.74 mmol L-1 d(-1) at a fixed N:P ratio of 19:1. Growth was maximized at the highest nutrient delivery rate, where 10 g dry biomass L-1 culture was achieved after 30 days of cultivation. GC-MS analysis of dichloromethane extracts from cell biomass revealed that O. secundiramea microplantlets produced myrcene, three acyclic halogenated monoterpenes (10-bromomyrcene, 10-bromo-7-chloromyrcene, 3,10-dibromomyrcene), and one cyclic halogenated monoterpene (6-bromo-1,2,8-trichloro-3,4-ochtodene). 10E-bromomyrcene levels were much higher than those of its isomer 10Z-bromomyrcene, demonstrating stereoselective-halogenation. Maximum yields of 10E-bromomyrcene and 6-bromo-1,2,8-trichloro-3,4-ochtodene were 15 and 13 mumol/g dry cell mass, respectively. Increasing the rate of nutrient delivery increased the accumulation of myrcene and 10-bromomyrcene during the first 14 days in culture. Furthermore, the yield selectivity toward higher halogenated monoterpenes increased as the rate of nutrient delivery decreased. From this data, a biogenic scheme was proposed where cyclic and acyclic halogenated monoterpenes are derived from sequential halogenation of myrcene, their common precursor. (C) 2003 Wiley Periodicals, Inc.