With help from TRIUMF's Positron Emission Tomography (PET) Group, Dr. Maria Maldonado of the University of British Columbia (UBC) is conducting research that may provide a scientific basis for emerging strategies aimed at controlling global warming. Dr. Maldonado holds a Canada Research Chair in Phytoplankton Trace Metal Physiology, and is an Assistant Professor in UBC's Earth and Ocean Sciences department. She is studying how copper (Cu) affects carbon dioxide (CO₂) uptake in phytoplankton. Phytoplankton are microscopic 'aquatic plants'. Like plants, phytoplankton take in CO₂ and through photosynthesis, convert it into sugars that they can consume as food. It is through photosynthesis that phytoplankton play an integral role in regulating atmospheric CO₂ levels. Without phytoplankton, the Earth's atmospheric CO₂ level would be significantly higher than the 360 parts per million we observe today.
   Dr. Maldonado warns that despite CO₂ uptake by phytoplankton, global CO₂ levels are rising. "Over the past century, industrial emissions of CO₂ have resulted in an exponential increase in atmospheric CO₂ to values not seen on earth in at least the last approximately 400,000 years", she explains.
   When fossil fuels are consumed in cars and industrial processes, CO₂ and other greenhouse gases that contribute to global warming are produced. Some believe that climate change can be mitigated by actively stimulating greater CO₂ uptake in phytoplankton by adding specific nutrients, such as iron (Fe), to ocean waters.

   Scientific research has indicated that Fe supports phytoplankton growth and efficient CO₂ uptake. However, Dr. Maldonado's preliminary research suggests that in waters with very low concentrations of Fe, such as in parts of the Subarctic Pacific and Southern Oceans, Cu may act as a substitute for Fe. Furthermore, Cu appears to facilitate Fe uptake and influence photosynthesis in these conditions. Dr. Maldonado, along with UBC students Shannon Harris and Amber Annett, are one of only a handful of teams studying this phenomenon, and are the first to demonstrate the important physiological role of Cu in Fe uptake in these tiny aquatic marine organisms.

   TRIUMF has thus far been providing the copper radioisotope ⁶⁴Cu for this study; however, with cooperation from MDS Nordion, TRIUMF will soon provide ⁶⁷Cu, as it has a much longer half-life than ⁶⁴Cu (2.58 days versus 12.4 hours). The longer half-life will enable the UBC researchers to take the tracer to sea for studies with on-site ocean water. Suzy Lapi, an SFU Ph.D. student working at TRIUMF, and Dr. Tom Ruth, Director of the TRIUMF-UBC PET Program, produce the copper isotopes. Over the course of the year, Dr. Maldonado's team will use these isotopes to investigate the distribution of Cu in the various cellular compartments of the phytoplankton to determine possible biochemical substitutions of Fe by Cu. Following this, the actual mechanisms of Cu uptake and kinetics of Cu transport in phytoplankton will be examined. The group plans to publish its findings by the end of this year. •