Project: GEOTRACES Pacific Section: Mercury Speciation Along a Zonal Section in the Eastern Tropical South Pacific

Scientists from Wright State University and Woods Hole Oceanographic Institution will participate in the 2013 GEOTRACES cruise to the Eastern Tropical South Pacific (ETSP). Seawater samples collected during this transect from Peru to Tahiti will be analyzed for total mercury (Hg), monomethylmercury (CH3Hg+), dimethylmercury ((CH3)2Hg), and elemental Hg (Hg0) to construct high-resolution vertical and horizontal sections. In addition to filtered seawater samples, the scientists will also analyze suspended particles for total Hg and CH3Hg+, as well as rain and aerosol samples for Hg species and dissolved and particulate thiols, such as cysteine and glutathione.

The cruise track extends from the upwelling region off Peru, to an expansive oxygen minimum zone (OMZ), followed by the hydrothermal vent fields of the East Pacific Rise, and finally into the highly oligotrophic waters near Tahiti. These different oceanographic features will allow the researchers to determine their influence on the inputs and cycling of Hg in the ocean. Specifically, they plan to assess whether (1) continental margins off Peru are a significant source of Hg, CH3Hg+, and (CH3)2Hg; (2) the OMZ sustains the highest levels of methylated Hg in the ocean; (3) hydrothermal systems are important sources of total and methylated Hg; and (4) the large gradient in productivity along this track impact the vertical distribution of this element, its bioavailability, and its speciation.