Nitrogen Deposition Effects on Diatom Communities in Lakes from Three National Parks in Washington State

Researchers found that nitrogen (N) deposition at Hoh Lake in Olympic National Park has surpassed a critical threshold of 1.0 to 1.2 kg N ha−1 year−1, triggering shifts in diatom communities indicative of N enrichment, particularly increases in Asterionella formosa and Fragilaria tenera. However, nine other lakes across three Washington State parks remain below this critical load, suggesting regional variability in N deposition effects. The study combined atmospheric N deposition measurements, lake water quality analysis, and sediment diatom assemblages to assess impacts. While Hoh Lake showed clear signs of N enrichment, Milk Lake exhibited potential climate-driven changes, though further research is needed to confirm this.

Sheibley, R. W., Enache, M., Swarzenski, P. W., Moran, P. W., & Foreman, J. R. (2014). Nitrogen Deposition Effects on Diatom Communities in Lakes from Three National Parks in Washington State. Water, Air, & Soil Pollution, 225(2). https://doi.org/10.1007/s11270-013-1857-x