Hypoxia alters the iron biogeochemical cycle in bioturbated coastal sediments

Coastal sediments are important sources of bioavailable dissolved iron driving primary production in surface waters. The widespread presence of low oxygen regions in coastal areas can affect the iron biogeochemical cycle either by enhancing or inhibiting key macrobiota-microbiota relationships that form labile pools of bioavailable. We used controlled sediment aquarium mesoocosms under varying bottom water oxygen concentrations (48, 106, and 280 µmol L-1) to test the effects of predicted declines in dissolved oxygen on the sedimentary iron biogeochemical cycle. Our results suggest that hypoxia affects the sedimentary iron biogeochemical cycle by shifting macrofaunal bioturbation behavior, which in turn results in an altered microbial community structure.