es5b04369_si_001.pdf (1.17 MB)
Cable Bacteria Control Iron–Phosphorus Dynamics in Sediments of a Coastal Hypoxic Basin
journal contribution
posted on 2016-02-10, 18:58 authored by Fatimah Sulu-Gambari, Dorina Seitaj, Filip
J. R. Meysman, Regina Schauer, Lubos Polerecky, Caroline P. SlompPhosphorus is an essential nutrient
for life. The release of phosphorus
from sediments is critical in sustaining phytoplankton growth in many
aquatic systems and is pivotal to eutrophication and the development
of bottom water hypoxia. Conventionally, sediment phosphorus release
is thought to be controlled by changes in iron oxide reduction driven
by variations in external environmental factors, such as organic matter
input and bottom water oxygen. Here, we show that internal shifts
in microbial communities, and specifically the population dynamics
of cable bacteria, can also induce strong seasonality in sedimentary
iron–phosphorus dynamics. Field observations in a seasonally
hypoxic coastal basin demonstrate that the long-range electrogenic
metabolism of cable bacteria leads to a dissolution of iron sulfides
in winter and spring. Subsequent oxidation of the mobilized ferrous
iron with manganese oxides results in a large stock of iron-oxide-bound
phosphorus below the oxic zone. In summer, when bottom water hypoxia
develops and cable bacteria are undetectable, the phosphorus associated
with these iron oxides is released, strongly increasing phosphorus
availability in the water column. Future research should elucidate
whether formation of iron-oxide-bound phosphorus driven by cable bacteria,
as observed in this study, contributes to the seasonality in iron–phosphorus
cycling in aquatic sediments worldwide.