We participated in the U.S. GEOTRACES cruise to the Arctic Ocean with the goal of studying the distribution and chemical forms of mercury (Hg), a toxic metal present at low but concerning concentrations in ocean water. Of importance on this cruise was the investigation of the various chemical forms of Hg that are present in seawater. It is important to study these forms of Hg separately because their fate and behavior in the ocean are quite different. For example, elemental Hg is a dissolved gas that is produced in high enough concentrations to de-gas from the ocean and enter the atmosphere, representing a natural process of detoxification of Hg from the ocean. In contrast, monomethylmercury is produced within the ocean, possibly in association with sea ice, and is the form of Hg that accumulates in seafood and poses a risk to human and environmental health. Thus, in order to understand the potential health risks in seafood, we must gain an understanding of the chemical forms of Hg in seawater.

We measured concentrations of the different Hg forms in both filtered water and suspended particles and along a cruise track that extended from the Bering Sea, to the North Pole and back (see figure).

Some highlights from our findings include: 

• Arctic Ocean water contains Hg from human sources such as fossil fuel use and gold mining. This was to be expected, but had not been documented before. Our measurements suggest that the water masses sampled have somewhere between 39 and 71% pollution mercury, with "younger" waters more recently in contact with the atmosphere displaying higher levels of human impact.
• The ratio of monomethylmercury to total Hg in the Arctic Ocean is not greater than in other ocean basins. Finding relatively low methylated mercury continues to puzzle us since animals that are part of the Arctic Ocean foodweb exhibit anomalously high mercury concentrations in their tissues. Thus, we've made progress but still do not understand why animals in the Arctic, and the people that depend on them for sustenance, are exposed to so much mercury. 
• Mercury inputs to the Arctic Ocean from Pacific Ocean water inflow is relatively low compared to other sources. Our work in the western Arctic was part of a historic season of chemical oceanography in region as the US effort was complemented by cruises staged by Europeans and Canadians as well, working in the eastern Arctic and Canadian Archipelago, respectively. Collectively, we will be able to describe where the mercury comes from, and where it goes. The US work in the western Arctic provides essential information on the Pacific side of this ocean.

Broader Impacts. This project supported dissertation research of a Ph.D. student at Wright State University, research of three Wright State undergraduate students, and a postdoctoral researcher at UC Santa Cruz. This research also promoted science education at the grade-school level. We engaged a class of seventh-graders at a Dayton-area middle school with our oceanographic research.  This was done through classroom visits by Dr. Hammerschmidt and his Ph.D. student, Alison Agather, who talked with middle school students about oceanography and living at sea.

Katlin Bowman, the postdoctoral researcher, was invited to blog for the Huffington Post during the expedition, to chronicle her research, the investigations and activities of other scientists aboard, life on a ship, and oceanography (https://www.huffingtonpost.com/author/katlin-bowman). This assignment stemmed from her personal blog (www.hginthesea.wordpress.com), which she started in 2011 as a Ph.D. student to document her work with the U.S. GEOTRACES program. To date, Bowman's blog has had over 30,000 views. Bowman also contributed an article, "Journey to the North Pole," to the Times Publishing Group (http://www.tpgonlinedaily.com/journey-to-the-north-pole/). In addition to Bowman's blog, Agather chronicled her experience as a first time sea-goer and GEOTRACES participant. Covering similar topics to a different audience, Agather's blog had over 800 visitors with 2,700 views.

While at sea, the Hg team participated in Coast Guard sponsored programs. We gave one of the weekly science lectures for the crew and scientists aboard. The lecture focused on Hg pollution and toxicity. Additionally, we guest-lectured in the Coast Guard's on-board oceanography course, teaching two lectures on pollution and climate change.

Katlin Bowman co-authored a children's book about her experience. To the Top of the World: One Scientist's Expedition to the North Pole is narrated from her perspective as a young female scientist on an expedition to the North Pole, and explains the basics of oceanography and Hg pollution with graphics, photos, and simple text for kids to easily understand. A total of 600 copies were sold and 64 copies donated to public libraries across the country. All proceeds from the book sales have been donated to nonprofits. Various public lectures and readings were organized to promote the book and Arctic GEOTRACES research.

Last Modified: 06/01/2019
Modified by: Carl H Lamborg