Analyzing the Effects of Coccolithophore Concentration on the Relationship Between Vertical Absorption Coefficient and Secchi Disk Depth

• Main Authors: Steinmetz, Halley, Staudinger, Michelle, Balch, William M
• Format: Text
• Language: unknown
• Published: ScholarWorks@UMass Amherst 2019
• Subjects: Northwest Atlantic; Ocean acidification
• Online Access: https://scholarworks.umass.edu/sustainableumass_studentshowcase/26; https://scholarworks.umass.edu/cgi/viewcontent.cgi?article=1027&context=sustainableumass_studentshowcase

The study of how light passes through water, known as ocean optics, is useful in determining the constituents suspended at the surface of a water body. Understanding the composition of the water over time can answer questions about how the oceans have changed with global climate change and ocean acidification. The vertical absorption coefficient in ocean waters is an indicator characterizing how deeply light penetrates the water column. Using this information, scientists can better understand and predict the amount of primary productivity occurring in the area. Here we examine the relationship between vertical absorption coefficient and Secchi disk depth to determine if the concentration of a type of calcifying phytoplankton, coccolithophores, causes the relationship to deviate from the findings of a pivotal historical study conducted in 1929 by Poole and Atkins. Data was collected during July 2018 aboard the R/V Endeavor on the EN616 “Cocco-Mix” cruise in the Northwest Atlantic Ocean. Diffuse attenuation was determined using downwelling irradiance measurements gathered from a HyperPro that measures electromagnetic energy through the water column. Diffuse attenuation values were compared with Secchi disk depth measurements taken at the same time and location as the HyperPro casts. Results will contribute to our understanding of how the relationship between light extinction and Secchi disk depth changes between water bodies. This knowledge can be used to relate light extinction and Secchi disk depth in historical studies in the Northwest Atlantic that did not have access to more modern equipment to measure light extinction.