Seaweeds emit volatile halocarbons that contribute to the formation of reactive atmospheric radicals and marine aerosols. The presence of reactive atmospheric radicals drives the rapid cycling of tropospheric photo-oxidants with O₃, which negatively impacts coastal air quality, while those that reach the upper troposphere and lower stratosphere contribute to the loss of the stratospheric ozone layer. The emission of halocarbons by the seaweeds are associated with defence and stress systems and are influenced by environmental variables such as irradiance and temperature. Geographical and temporal differences in emission and biovariability commonly impede efforts to quantify these compounds from their biogenic sources. This study investigated the emissions of CHBr₃, CHBr₂Cl and CHBrCl₂ from two commercially important tropical seaweeds, Gracilaria manilaensis Yamamoto and Trono, and Kappaphycus alvarezii (Doty) L. M. Liao during cultivation at three cultivation systems, and how changes in environmental parameters such as irradiance, temperature, and seawater nutrients could affect the halocarbon emissions by the farmed seaweeds. Meanwhile, estimation from this study showed that the harvesting activity of K. alvarezii in the year 2020 in Malaysia could have released 63 – 322 mol Br hr^-1.