Diatoms

The hard cell wall, or "frustule", of a diatom

© St. Croix Watershed Research Station / Mark Edlund

Diatoms are a type of algae that have cell walls made of silica. When they die, portions of the cell walls called frustules settle into the bottom sediments and are preserved like tiny bits of glass. Different species of diatoms can be identified by the unique patterns of their frustules.

In life, diatoms are sensitive to environmental changes, and the composition of diatom communities (presence and abundance of different species) will shift in response to such changes. In death, then, the layers of frustules contained in bottom sediments provide a history of water quality going back hundreds of years.

Long-term Monitoring

We work with the St. Croix Watershed Research Station to collect and identify diatom frustules from the same places where we monitor water quality. We collect diatom samples from each lake on a 3- to 5-year rotation.

Our partner:

St. Croix Watershed Research Station

Monitored at:

• Apostle Islands National Lakeshore
• Indiana Dunes National Park
• Isle Royale National Park
• Mississippi National River and Recreation Area
• Pictured Rocks National Lakeshore
• Saint Croix National Scenic Riverway
• Sleeping Bear Dunes National Lakeshore
• Voyageurs National Park

Learn More

Resource briefs provide a one- or two-page overview of the latest findings and what they mean. Monitoring reports are in-depth technical reports that include data analyses and possibly management recommendations.

Resource Briefs

Source: Data Store Saved Search 5003. To search for additional information, visit the Data Store.

Monitoring Reports

Source: Data Store Saved Search 408. To search for additional information, visit the Data Store.

Journal Articles

Source: Data Store Saved Search 5002 (results presented are a subset). To search for additional information, visit the Data Store.

Monitoring Protocol and Standard Operating Procedures

Protocol documents detail precisely how monitoring is carried out.

Ramstack-Hobbs, J. M., M. B. Edlund, D. R. Engstrom, B. M. Lafrancois, and D. D. VanderMeulen. 2019. Diatom monitoring protocol for the Great Lakes Network: Version 1.1. Natural Resource Report NPS/GLKN/NRR—2019/1910. National Park Service, Fort Collins, Colorado.