An evaluation of methods for measuring phytoplankton and ecosystem status in the Chukchi Sea

• Main Author: Neeley, Aimee Renee
• Other Authors: Harris, Lora A, Digital Repository at the University of Maryland, University of Maryland (College Park, Md.), Marine-Estuarine-Environmental Sciences
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2020
• Subjects: Biological oceanography; Arctic; Chukchi Sea; ecology; ocean color; phytoplankton; remote sensing; Chukchi; Phytoplankton; Sea ice
• Online Access: http://hdl.handle.net/1903/26250; https://doi.org/10.13016/cew0-krao

This dissertation represents a three-pronged approach for evaluating ecosystem-level changes in the Chukchi Sea: 1) evaluation of uncertainties in field measurements of absorption 2) direct measurements of phytoplankton taxonomy and the community’s interaction with the environment and 3) apply existing and new remote sensing tools to measure ecosystem-level changes over large spatio-temporal scales. The first and final chapters provide context for the dissertation and conclusions. The second chapter quantifies the magnitude of uncertainty within multiple methods for measuring particle absorption. The light field exiting the surface ocean is measured by satellite instruments as ocean color and is impacted by water column absorption. Biogeochemically-relevant products, such as phytoplankton and particle absorption are derived from the light field using algorithms. Therefore, accurate measurements of absorption are critical to algorithm development and validation. I employed a multi-method approach to estimate the precision of measuring optical density of particles on a filter pad using two common spectrophotometric methods, and assessed the uncertainty of the computational techniques for estimating ap. The uncertainty ranged from 7.48%-119%. Values of ap at 555 nm and 670 nm exhibited the highest values of uncertainty. Poor performance of modeled ap compared to measured ap suggests the uncertainties are propagated into bio-optical algorithms. The third chapter investigates the consequences of earlier seasonal sea ice retreat and a longer sea-ice-free season on phytoplankton community composition. The timing of sea ice retreat, light availability and sea surface stratification largely control the phytoplankton community composition in the Chukchi Sea. This region is experiencing a significant warming trend, decrease in sea ice cover, and a documented decline in annual sea ice persistence and thickness over the past several decades. I applied multivariate statistical techniques to elucidate the mechanisms that ...