Detection of new hydrothermal sources using an in situ integrated analyzer for manganese (IISA-Mn)

Hydrothermal anomalies found in the deep sea are a place where unique ecosystems exist, and may become a possible new resource for metallic ore mining. Elements such as iron and manganese are found in high concentration in hydrothermal vents. Therefore it is possible to use such metal ions as a tracer to detect and evaluate new hydrothermal sources. Here we present a miniaturized and integrated microfluidic system for the detection of manganese in deep-sea environment, called IISA-Mn (In Situ Integrated Analyzer for Mn²⁺). The detection system is based on the chemiluminescence reaction of manganese contained in the seawater sample with a luminol-based reagent, which offers a high sensitivity. This system is composed of a microdevice for mixing and reaction, a pumping unit, several valving units, and a PMT (photomultiplier) detector. The system is able to detect manganese concentration above 100 nM in seawater, and gives a linear response until 1 μM. It is also proven to be able to work continuously during the 8 hours of an actual dive. This system has lead to the discovery of a previously unknown hydrothermal site near Okinawa Islands.