Community-Level Biotic Response to Increasing Climate Variability During the Last 150 Years: Steady and Warming Conditions on the Continental Shelf of the Pacific Arctic

• Main Author: Meadows, Caitlin Ana
• Format: Text
• Language: English
• Published: The University of Chicago 2020
• Subjects: Chukchi; Climate change; Pacific Arctic; Subarctic
• Online Access: https://doi.org/10.6082/uchicago.2760; http://knowledge.uchicago.edu/record/2760

Ecosystem monitoring since 1980 has established that the boundary between the Arctic and the Subarctic has shifted northward on the Bering continental shelf between 1998 and 2001. However, such quantitative benthic data have been collected consistently only since the 1980’s, whereas additional long term data are available from natural history collections (NHCs) since 1865 and from locally accumulating dead-shell assemblages. By extracting and integrating insights from these diverse sources, I address the following questions: (1) Do dead-shell assemblages capture the shifting Subarctic-Arctic boundary in the Pacific Arctic ecosystem? (2) How long does biogenic carbon persist on the Pacific Arctic continental shelf? (3) What is history of bivalve family geographic distributions in the N Bering and Chukchi Seas over the last 150 years? In habitats where either Subarctic or Arctic conditions have persisted over the last 40 years, bivalve death assemblages agree closely with counterpart living communities in taxon and guild composition and are not subject to significant post-mortem bias. Significant live-dead discordance occurs only in areas with documented changes in community composition; there, dead assemblages are mixtures of shells from pre- and post-transition communities. This spatial pattern is robust in both numerical abundance- and biomass-based measures of community composition. Live-dead discordance can thus reliably differentiate between stable and rapidly changing habitats in cold, high-latitude settings, relevant to evaluating climate change. Overall, shells from Arctic death assemblages are young: all specimens of Nuculana are < 1600 years old with a median age of 50 years, and all Macoma shells are < 850 years old with a median age of about 30 years. These maximum shell ages are an order of magnitude lower than encountered at lower latitudes, while median shell ages are similar to those at lower latitudes. The lowest median shell ages and highest rates of shell loss are in the northern Bering ...