Managing the Red Lake Nation’s and Minnesota’s largest lake: monitoring and paleolimnology support a site-specific standard for Upper and Lower Red Lakes (Red Lake Nation and Minnesota, United States)

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Burge DRL, Edlund MB, Bowe S, Bowe K, Anderson JP, Bouchard RW, Heathcote AJ, Leavitt PR, Engstrom DR. 2023. Managing the Red Lake Nation’s and Minnesota’s largest lake: monitoring and paleolimnology support a site-specific standard for Upper and Lower Red Lakes (Red Lake Nation and Minnesota, United States). Lake Reserv Manage. XX:XXX–XXX.Water quality and the ability of lakes to provide benefits such as recreation and aquatic life are negatively impacted by climate change, aquatic invasive species, and nutrient enrichment. To address these lake-management challenges, regionally tailored water quality criteria need to assign achievable and protective goals while minimizing assessment errors. In Minnesota, when lakes exceed state water-quality standards, restoration plans are developed and implemented based on eco-regional standards, or in cases where it is determined that the regional standard is not appropriate, a site-specific standard may be developed. Upper Red Lake and Lower Red Lake, located within the boundaries of the Red Lake Indian Reservation (the Red Lake Nation) in northwestern Minnesota (United States), have been recently experiencing cyanobacteria blooms, as well as routinely exceeding the regional water quality criteria for total phosphorus and chlorophyll a. The last 20 yr of water quality monitoring suggest a stable recent history with no significant trends. To extend this time perspective, biogeochemical evidence from paleolimnology was used to reconstruct a 150 yr history for these 2 large, shallow lakes to determine whether site-specific water quality standards might be recommended. Biogeochemical evidence (e.g., sedimentation rates, phosphorus fractions, biogenic silica, diatom community composition, and fossil algal pigments) from 10 sediment cores revealed complex sedimentary dynamics together with a small gradual increase in limnological productivity over the last 2 centuries. Despite the implied productivity change, diatom-inferred phosphorus showed no significant increase among the sediment cores. Furthermore, the reconstructed total phosphorus values were within the range of modern monitored values. Because the paleolimnological evidence suggests little change to the aquatic ecology of the Red Lakes over the last 150 yr, and monitoring data show regular exceedance of regional TP standards with no trend in the last 20 yr, site-specific water quality standards are deemed appropriate for this large, shallow lake system.

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