The international research program GEOTRACES aims to close this gap of knowledge, under the leadership of Prof. Martin Frank from the Leibniz Institute of Marine Sciences in Kiel, Germany.

For decades there has been interest in near and deep shore nodules yielding up mined minerals. Work on deep sea manganese nodules from Southern Ocean for example in the 1970's studied using chemical analysis, X-ray diffraction, optical mineragraphic and electron probe microanalysis, found these lower in manganese, iron and associated elements than the average grade of manganese nodules from other localities. A number of chemical relationships were observed, namely that nickel, copper, cobalt, barium, zinc, molybdenum, strontium, sulphur and phosphorus are associated with manganese rich phases, and titanium with the iron rich phases.

Tracking trace metals is even more needle in haystack work, with only 300 trillionth of a gram (0,0000000003g) of dissolved cadmium per litre found on average in ocean surface waters. But recent research has proved that many species of phytoplankton need cadmium for their metabolism. Plankton in turn are the basis of the food chain in the oceans and stores huge amounts of carbon dioxide.

Besides cadmium other trace metals of similar importance: aluminium, manganese, copper, zinc, or iron. Where they come from and how they are distributed in the oceans is not well known. Globally standardised measurement procedures were also lacking until recently.

“It’s extremely difficult to make a reliable statement about changes in iron concentrations on the order of some billionth of a gram if you take the water samples with metal wires just a few metres away from 4,500 tons ship-steel,” wryly explains Professor Martin Frank, (right) geologist at Leibniz Institute of Marine Sciences (IFM-GEOMAR) in Kiel, Germany.



For seven years scientists from more than 30 nations have successfully been working together within the Geotraces programme to find solutions for this problem. Now they are ready for the first measurements. In February 2010 an event will take place during the Ocean Sciences Meeting in Portland, Oregon, USA.

While Martin Frank leads the Geotraces expeditions leave the harbour of Las Palmas Gran Canaria, Spain with 24 scientists from Kiel, Bremen, Rostock, Cologne, Barcelona and Norfolk (Virginia, US).

During the 9000km cruise along the West-African coast, across the Atlantic and back north along the Brazilian coast the scientists will measure trace metal concentrations up to a water depth of 5000 metres. It is planned to collect about 12,000 litres of water.

“To avoid contamination we use purpose-built sample bottles made of plastic, which are fixed in a specially coated device. Instead of a steel wire we use a Kevlaer-cable to lower this frame to the sampling depths,” Professor Frank explains.

RV Meteor is not equipped with such a cable, so a mobile winch and cable owned by the U.S. Geotraces programme is being used. Two containers with clean room laboratories are included in the equipment where scientists will prepare the samples according to the Geotraces programme guidelines, to enable high precision measurements in the on shore home laboratories after the cruise.

“This way we will get data that we can compare with the results of other measurement campaigns around the globe in the future”, says Professor Frank. More than 50 expeditions are planned by the Geotraces programme in the coming years.

The expedition results will be used by scientists from many research directions.

Biologists want to know how, where, when and in which quantities micro-nutrients are for example supplied into the oceans by dust. Oceanographers want to use the trace metals to track ocean currents.

“Some of the trace metals do not only vary in their concentration but also in their isotopic composition, which provides precise information about the origins of the respective metals,” says Professor Frank.

Climate researchers use the isotope compositions for precise reconstructions of past climate conditions. And a better understanding of the nutrient cycle in the oceans is fundamental to understanding consequences of environmental pollution. “This programme and our expedition are truly fundamental marine research, the results of which will be important for many different subjects,” Professor Frank concludes.