Ora Johannsson

Background
As an ecologist, I have studied a range of questions regarding species distribution, co-existence, ecosystem structure and productivity, and invasive species impact and risk assessment. My career was with the Department of Fisheries and Oceans, at the Great Lakes Laboratory for Fisheries and Aquatic Sciences in Burlington, Ontario. I ran a large program assessing the response of Lake Ontario to changes in nutrient loading and fisheries impacts.  We were not allowed to study the fish directly but collaborated with the fisheries agencies to develop holistic understanding of the lake ecosystem.  As dreissenids (zebra and quagga mussels) started to invade Lake Erie, we also explored the present and changing ecosystem of that lake, which helped us to understand the implications for change in other systems. As part of my responsibilities at DFO, I was involved with developing remedial action plans for the St. Claire and Detroit Rivers, Beneficial Use Assessment for several Areas of Concern under the Great Lakes Water Quality Agreement, and the Lakewide Management Plans for Lake Erie. I also represented DFO on the Science Advisory Board of the Great Lakes Fishery Commission.

After leaving DFO, I have completed a number of studies on the response of Mysis relicta to invasive species started during my time at DFO.  As well, I have studied air breathing in the Lake Magadi tilapia, the oxidative stress response of Pacu, a native fish of the Rio Negro, and the dynamics of reactive oxygen species (ROS) production and photo-oxidation of dissolved organic carbon (DOC) in the Rio Negro, a branch of the Amazon River.

Present Studies
At present, my work continues to address questions on the control of photo-oxidation of dissolved organic carbon. My study site remains the Rio Negro, although some experiments are conducted at UBC.   The return of carbon dioxide to the atmosphere through photo-oxidation of dissolved organic carbon is a globally important pathway.  Although we know the importance of light to this process, we cannot yet make predictions for specific sites or larger entities (lakes, rivers).  We need quantitative relationships linking temperature, oxygen, pH and water transparency profiles to the rates of photo-oxidation.  In addition, we need to be able to predict how susceptible a particular DOC is to photo-oxidation.  These are the types of questions I am asking.  The other side of the coin, is to predict the susceptibility of DOC to biodegradation as dissolved organic carbon is considered an important source of energy for these black water systems.