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Comparison of stream periphyton assemblages as indicators of nutrient conditions
Citation:
Pilgrim, E., N. Smucker, C. Nietch, J. Darling, H. Wu, AND M. Molina. Comparison of stream periphyton assemblages as indicators of nutrient conditions. Joint Aquatic Sciences Meeting 2022, Grand Rapids, MI, May 14 - 20, 2022.
Impact/Purpose:
This work is a comparison of DNA metabarcoding results across diatom, bacteria, and fungi from stream periphyton and how this information allows us to find indicators of nutrient change within each group.
Description:
Nitrogen and phosphorus continue to be major stressors of aquatic ecosystems, but the transient nature of these nutrients often makes measuring their impacts challenging. Periphyton communities from stream beds include a suite of organisms with the potential to be valuable indicators of changing nutrient conditions, but identification of periphyton constituents such as diatoms, bacteria, and fungi can be difficult. Here we apply DNA metabarcoding techniques to each of these three groups to analyze their potential as indicators of nutrient condition. Samples were taken weekly during July to October at 25 stream sites (second and third order) within a temperate watershed with a mix of agricultural, industrial, and urban land cover. Diatom, bacterial, and fungal taxa were each targeted for DNA metabarcoding analysis with loci specific to each group (rbcL, 16S, and ITS, respectively). The relative abundances of taxa found in each group were compared to contemporaneous total phosphorus (TP) and total nitrogen (TN) concentrations and then analyzed with threshold indicator taxa analysis (TITAN), boosted regression trees, and gradient forest analysis. These analyses identified indicator taxa typical of low or high TP and low or high TN, along with concentrations at which the greatest changes occurred within these assemblages. We also compare the responses of diatom, bacterial, and fungal assemblages to TP and TN conditions. This work highlights how DNA metabarcoding of difficult to identify organisms can be used to develop indicators of environmental change that can also be used to inform nutrient threshold criteria.
