Diatoms of North AmericaWhen 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.
