1. Earth & Planetary Sciences Division; Department of Physical Sciences; MacEwan University; Edmonton AB Canada T5J 4S2
2. School of Ocean Sciences; College of Natural Sciences; Bangor University; Menai Bridge LL59 5AB UK
3. School of Environmental Sciences; University of Liverpool; Liverpool L69 7ZT UK
4. St. Croix Watershed Research Station; Science Museum of Minnesota; 16910 152nd Street North Marine St. Croix MN 55047 USA