Ecosystem impacts of variable recruitment in Antarctic krill investigated with long-term monitoring and archived ADCP backscatter data

• Main Author: Lohmann, Amanda
• Other Authors: Nowacek, Douglas P
• Format: Doctoral or Postdoctoral Thesis
• Language: unknown
• Published: 2023
• Subjects: Ecology; Antarctic; Antarctic Peninsula; Anvers; Anvers Island; Antarc*; Antarctic Krill; Antarctica
• Online Access: https://hdl.handle.net/10161/29135

Dissertation In this work, I explore the impacts of anthropogenic climate change on the krill-reliant marine ecosystem of the western Antarctic Peninsula. I use long-term ecological monitoring data to examine the impact of highly variable krill recruitment on a krill predator population, and I use archived backscatter data from an Acoustic Doppler Current Profiler (ADCP) to investigate biotic and abiotic drivers of summer krill distribution along the mid-to-coastal shelf region of the western Antarctic Peninsula.In Chapter 1, my coauthors and I examine the impact of cyclical krill recruitment on Adélie penguins. Between 1992 and 2018, the breeding population of Adélie penguins around Anvers Island, Antarctica declined by 98%. In this region, natural climate variability drives five-year cycling in marine phytoplankton productivity, leading to phase-offset five-year cycling in the size of the krill population. We demonstrate that the rate of change of the Adélie breeding population also shows five-year cycling. We link this population response to cyclical krill scarcity, a phenomenon which appears to have arisen from the interaction between climate variability and climate change trends. Modeling suggests that, since at least 1980, natural climate variability has driven cycling in this marine system. However, anthropogenic climate change has shifted conditions so that fewer years in each cycle now prompt strong krill recruitment, triggering intervals of krill scarcity that result in drastic declines in Adélie penguins. Our results imply that climate change can amplify the impacts of natural climate oscillations across trophic levels, driving cycling across species and disrupting food webs. The findings indicate that climate variability plays an integral role in driving ecosystem dynamics under climate change. In Chapter 2, I explore the viability of using archived Acoustic Doppler Current Profiler (ADCP) backscatter data to examine krill distribution on the WAP. During the Palmer LTER’s oceanographic cruises, the ...