When students collected samples from one of the buoys in Little Miller’s Bay, West Lake Okoboji, they found the attached diatoms Cymbella affinis and Gomphoneis olivaceum. That was not a surprise, but both species were producing gametangia and forming auxospores - diatom sex! Diatoms have an unusual life cycle, in which the very youngest cells are the biggest. Over their lifespan, diatom cells get smaller and smaller through vegetative cell division. The class was able to observe the different elements of the lifecycle, and found that these two species have a coordinated, synchronous life cycle. Students also measured sizes of the gametangial and initial cells to determine the minimum and maximum cell sizes.


The class cored the lake to obtain sediment and examine the paleolimnological record. The sediments had abundant Chironomus larvae living in fine organic material. The students were curious about the Chironomus diet, so they carefully dissected and examined the guts of Chironomus larvae for diatoms. They found that the species in the guts differed from species in the remainder of the sediments. As a result, the students propose that Chironomus sp. is a selective feeder, favoring small centric species.

Students contributed to the global citizen science database iNaturalist.org, in the project Ecology and Systematics of Diatoms. Students made 172 observations and identified 96 species from Iowa, Minnesota, Nebraska, Maryland, Florida, and Melbourne, Australia. Check out the links!

As a final project, each student prepared a species page for the Diatoms of the United States project. Look for the student pages to be coming online soon.

Funding

  • J.C. Kingston Fellowship

    Teaching Fellowship - Shelly Wu

  • E.F. Stoermer Scholarship

    Merit Scholarship - David Burge

  • C.W. Reimer Scholarship

    Merit Scholarship - Eric Massa

  • Okoboji Foundation

    Educational Support

  • Roy J. Carver Charitable Trust

    Student Microscopes and Imaging Systems

  • Messengers of Healing Winds

    Student Microscopes and Imaging Systems

Participants

Sylvia Lee

Biologist U.S. Environmental Protection Agency

Mark Edlund

Senior Scientist Science Museum of Minnesota

Shelly Wu

Diatom Enthusiast

David R.L. Burge

Lab Technician St. Croix Watershed Research Station, Science Museum of Minnesota

Eric Massa

M.S. Student Florida International University

Anna Drahos

Undergraduate student Iowa State University

Jaclyn Rarick

Undergraduate student University of Iowa

Stephanie Robson

Ph.D. Student Monash University, Australia

Lynn Brant

Emeritus Professor of Geology University of Northern Iowa

Steve Main

Professor Retired, Wartburg College

Iowastudent 017
Image Credit: Shelly Wu
How to collect from the epipelon.
Image0052
Image Credit: Stephanie Robson
Exploring sexual reproduction in Cymbella
Students 2017 1
Image Credit: Sylvia Lee
Exploring the Freda Haffner Kettlehole
Students 2017 2
Image Credit: Sylvia Lee
Exploring the Freda Haffner Kettlehole
Chironomidinsediments
Image Credit: Mark Edlund
Eric, David, and Annie separating chironomid larvae from sediment