Investigating the Bioavailability of Nutrients and Metals From Hydrothermally Active Shallow Seamounts of the Mariana Arc

Abstract

Hydrothermal vents have recently been recognized to have an impact on the global inventory of essential trace nutrients due to the enhanced concentrations of metals like iron (Fe) and manganese (Mn) in hydrothermal fluids. Past studies have hypothesized that hydrothermal inputs could influence surface ocean productivity, yet limited studies have displayed a direct connection. In this study, we utilize the shallow seamounts of the Mariana Arc to investigate (a) how the abnormally shallow nature of these vent sites may facilitate the transport of metal-rich hydrothermal fluids to the euphotic zone and (b) the potential for these fluids to fuel phytoplankton productivity. In a set of incubation experiments, we added hydrothermal plume waters from the shallow seamounts of NW Rota-1 (470 m) and Esmeralda (225 m) to surface waters and incubated them for 60 hours. We found that the shallowest vent site, Esmeralda, had the greatest water column concentrations of dissolved Fe (15-30 nM), but that the average net growth rate of 0.825±0.042 day-1 was not statistically different from background stations. This work demonstrated that hydrothermal fluids from seamounts are bioavailable and that shallow seamount venting has the potential to promote surface primary production through chemical and physical nutrient supplementation.