Diatom monitoring protocol for the Great Lakes Network: Version 1.1

Ramstack-Hobbs, Joy M.; Edlund, Mark B.; Engstrom, Daniel R.; Lafrancois, Brenda Moraska; VanderMeulen, David D.

The National Park Service’s (NPS) Great Lakes Inventory and Monitoring Network (GLKN) has developed a prioritized list of indicators, termed “Vital Signs”, for monitoring long-term ecosystem health in NPS units in the Great Lakes ecoregion. Diatoms, a group of algae with cell walls made of silica, are one of several Vital Sign monitored by GLKN. Diatom cells walls preserve well in lake and river sediment, and different species can be identified by unique patterns in their cell walls. Diatoms sensitively register environmental changes at the base of the food chain and are thus critical to all ‘bottom-up’ ecological processes. As primary producers, their relationship to environmental stressors is more direct and traceable than those at higher trophic levels (e.g., invertebrates, fish, and amphibians). Therefore, diatoms are useful bioindicators of lake and river ecological health and can be used to track changes in ecological health over time. The nine national parks in GLKN encompass a variety of aquatic habitats and biota, including 129 named lakes, totaling nearly 41,000 ha. Diatom monitoring will occur at approximately 30-25 lake and 5-8 river sites that are co-located with sites monitored by GLKN for water quality through separate protocols. The lakes selected for monitoring span gradients of surface area, depth, visitor use, water chemistry, and spatial distribution within each park. The few river sites selected for diatom monitoring will be lake-like, where sediment deposition occurs. Diatom monitoring will be rotated across parks on an approximate 5 year cycle, with about ten sites monitored annually, typically in the fall. Through analysis of diatoms in surficial sediment we will address the following questions: 1. What is the current ecosystem status of a particular lake in relation to other regional lakes? 2. Are similar ecological trends occurring across regional lakes (e.g., related to climate change or atmospheric deposition)? 3. What is the ecosystem status of this lake in relation to historical environmental change noted in regional sediment cores? 4. Has this lake changed since the last time it was sampled? If so, what are the magnitude and direction of that change?

Diatom monitoring protocol for the Great Lakes Network: Version 1.1

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