|The Walter J. McCarthy Jr. came under the Lift Bridge on Tuesday afternoon around 5 pm, back from sea trials watched over by the Coast Guard. Right behind the 1,000-footer was the 119-foot Blue Heron, above, coming in after a successful day at school on the Lake. Owned and operated by the University of Minnesota Duluth, the research vessel is used by a wide variety of groups that study the Great Lakes. Today, the Blue Heron hosted a calculus class from UMD, specifically “Calculus for the Natural Sciences.” Today was the natural sciences part. Students took samples of sediment from the bottom of the lake and also did some biological sampling using plankton nets. The class was split into 2 groups; there were about 8 students in both a morning and an afternoon group. The boat carries a crew of 5.