Historical abundance and morphology of Didymosphenia species in Naknek Lake, Alaska

• Main Authors: Pite, Danielle P, INSTAAR Campus Box 450, University of Colorado, 1560 30th Street, Boulder CO 80309, USA, Smith College, Northampton MA01063, USA, Lane, Kelly A, Hermann, Anna K, Tulane University, New Orleans LA 70118, USA, Spaulding, Sarah A, U.S. Geological Survey, Fort Collins Science Center, Fort Collins, CO 80526-8118, USA, sarah.spaulding@usgs.gov, Finney, Bruce P, Idaho State University, Department of Biological Sciences, Pocatello ID 83209, USA
• Format: Publication
• Language: English
• Published: Division of Biology, Faculty of Science, University of Zagreb 15.10.2009
• Subjects: Alaska; bloom; counting; diatom; Didymosphenia clavaherculis; Didymosphenia geminata; history; invasion; lake; morphology; stream

Since the 1980s, nuisance blooms of Didymosphenia geminata (Lyngbye) M. Schmidt have been documented in sites that are warmer and more mesotrophic than historical records indicate. While the invasion of D. geminata in New Zealand is well documented, it is less clear whether nuisance blooms in North America are a new phenomenon. In order to test the hypothesis that D. geminata blooms have increased in recent years, we examined the historical record of this species in sediments of Naknek Lake, in Katmai National Park, Alaska. Chronological control was established by relating the presence of two ash layers to known volcanic eruptions. We identified two species of Didymosphenia within the sediment record: D. geminata and D. clavaherculis (Ehrenberg) Metzeltin et Lange- -Bertalot. This is the first published record of D. clavaherculis in North America. We found no statistically significant change in the numerical presence of D. geminata or D. clavaherculis, as a group, in Naknek Lake between the years 1218 and 2003. While there has been no sudden, or recent, increase in abundance of Didymosphenia in Naknek Lake, morphological features of D. geminata populations in Naknek Lake are distinct compared to morphological features of D. geminata in streams containing nuisance blooms from sites in North America and New Zealand. Variance in the morphology of Didymosphenia cells may help determine relationships between distinct sub-populations and establish the history of habitat invasion.