The Production of Volatile Iodocarbons by Biogenic Marine Aggregates

We present the first reported measurements of volatile iodocarbon production by biogenic marine aggregates. Iodomethane (CH₃I), iodoethane (C₂H₅I), 2- iodopropane (CH₃CHICH₃), and 1-iodopropane (CH₃CH₂CH₂I) concentrations were determined in incubations of aggregates formed by concentrating the >53 µm fraction of the plankton during a field campaign in the Celtic Sea. All four iodocarbons increased significantly in concentration in the aggregate incubations relative to filtered seawater controls. Maximum production rates ranged from 0.01 pmol L¯1 h¯1 for CH₃CHICH₃ to 0.31 pmol L¯¹h¯¹ for C₂H₅I. Accompanying pheopigment and bacterial heterotrophic production suggest that the processes taking place on the aggregates studied were a good representation of those known to occur on natural marine particles. We also report iodocarbon production rates observed in natural marine aggregates, including a diatom mucilage collected in the Celtic Sea and phytodetritus sampled from Kongsfjord in the Arctic. Detrital particles could be hotspots of iodocarbon production in the marine environment.