Areas of high ocean productivity tend to be coastal, suggesting that ocean and terrestrial ecosystems may be closely coupled. A geophysiological model proposes that coastal marine and peatland ecosystems are tightly coupled primarily via atmospheric pathways of sulfur from oceans to peatlands, which are mainly sulfur limited, and via the riverine and groundwater transport of soluble organic iron from peatlands to oceans, which are mainly iron limited. Findings from the literature, along with precipitation pH data from southeast Alaska, are presented in support of the proposed pathways. Nutrient limitation studies show increases in primary productivity of marine and peatland ecosystems associated with additions of iron and sulfur, respectively. Mechanisms of nutrient transport commonly invoked to explain ocean productivity are not sufficient in accounting for regional and global patterns of chlorophyll concentration. Regional and global distributions of peatland cover shows remarkable correspondence with chlorophyll concentration data, consistent with model predictions. ¿ 1997 American Geophysical Union