Magnetotactic Bacterial Activity in the North Pacific Ocean and Its Relationship to Asian Dust Inputs and Primary Productivity Since 8.0 Ma

Magnetotactic bacteria (MTB) require iron and organic carbon for biomineralization, which can be supplied by dust inputs that stimulate primary productivity in iron-limited oceans. However, MTB activity and its relationship to Asian dust inputs and primary productivity are not well known in the North Pacific Ocean. Here, we present an eight-million-year record of magnetofossil abundance, Asian dust flux, and primary productivity from North Pacific sediments (Ocean Drilling Program Hole 885A). Our results demonstrate that Asian dust delivered iron to stimulate primary productivity and then boost MTB biomineralization in the late Miocene. Since the late Pliocene, dust inputs and primary productivity appear to have been decoupled, with MTB activity controlled mainly by primary productivity rather than dust inputs. Equant magnetofossil abundances co-vary with eolian flux, and may provide here a proxy for dust inputs. This work provides perspectives on relationship between MTB activity, dust inputs, and primary productivity on million-year timescales.