Methyl iodide in the NW Atlantic; spatial and seasonal variation

Abstract

While the global ocean is an important source of atmospheric methyl iodide (CH (sub 3) I), the major producers of CH (sub 3) I within the ocean remain unclear. During a seasonal study in the NW Atlantic, the relationship between CH (sub 3) I and some characteristic phytoplankton pigments was examined in order to identify possible phytoplankton producers of CH (sub 3) I. Although no characteristic pigments exhibited a strong positive correlation with CH (sub 3) I, in the surface mixed layer, there was a weak correlation (R=0.35, n=70, p=0.003) between the concentrations of CH (sub 3) I and zeaxanthin, a pigment characteristic of cyanobacteria in the open ocean. In this study, a moderate correlation was observed between the surface mixed layer CH (sub 3) I concentration and depth-averaged daily radiant exposure (R=0.61, n=15, p=0.02), which indicates a positive influence of solar radiation on CH (sub 3) I production. However, the results from this study do not conclusively show whether the influence was exerted through photochemistry or other pathways. A positive correlation between the CH (sub 3) I concentration and sea surface temperature was also observed (R=0.61, n=79, p<<0.001).