Multi-scale temporal variability in biological-physical associations in the NE Chukchi Sea

Abstract

In high-latitude marine ecosystems, traditional net sampling is constrained to the ice-free season, resulting in an incomplete understanding of ecosystem structure and dynamics. Using 4 years of continuous acoustic and environmental measurements from a NE Chukchi Sea subsurface mooring, we assessed fish and zooplankton abundance and behavior relative to environmental factors over a wide range of temporal scales. We applied wavelet analysis to these high-resolution, multi-year, concurrent, and co-located datasets to identify temporal scales of variability in environmental conditions and density and vertical distribution metrics for pelagic fish and zooplankton. Biological variability occurs mainly at distinct diel (24-h), seasonal (3–6-month), and annual (9–12-month) scales. Diel patterns are present throughout the year but are strongest in autumn when day-night cycles are pronounced. Seasonal variability in zooplankton metrics (3–4 months) is mainly associated with sea ice patterns that may also regulate the onset of primary production. Seasonal variations in fish metrics are associated most closely with salinity patterns (~ 3 months) and slower changes in water temperature (~ 6 months). Annual cycles in biological characteristics are influenced by year-round variations in water temperature, sea ice concentration, light irradiance, and wind. Wind and salinity-associated variability in biological metrics was observed at scales of 6–28 days. Scale-dependent biological and environmental associations vary through time and emphasize the importance of high-resolution long-term studies for comprehensive ecosystem characterizations. Our results identify necessary scales of observation in Arctic monitoring programs for improved prediction and detection of biological responses to rapidly changing environments.