Date

Spring 2019

Document Type

Master's Thesis (Open Access)

Degree Name

Master of Science (M.S.)

Department

Moss Landing Marine Laboratories

Abstract

Accurate measurements of phytoplankton biomass can help provide information to oceanographers necessary to understanding the foundations of various marine food webs. In addition, such measurements can offer further insight into their life cycles and their impact on the global biogeochemical carbon cycle. For several decades, the activity or concentration of ATP has been used as a proxy of biomass in oceanography of micro-organisms, however, little is known about the lower limits of ATP signals, their interpretation, and the processes that drive this signal down to zero. Thus, the primary goal of this study was to determine the time scale of ATP depletion under various disinfecting treatments. The secondary goal was to determine the validity of ATP as a phytoplankton biomass indicator in natural systems. ATP measurements were made on a transect line across the Northern Pacific Ocean in order to determine if diel variability could be detected and separated from the influence of zooplankton vertical migration. Four species of phytoplankton; Thalassiosira weissflogii, Amphidinium carterae, Dunaliella salina and Isochrysis galbana in addition to a natural community sampled from Moss Landing harbor, were treated with heat, chlorination or glutaraldehyde, and ATP measurements were analyzed overtime. Heat was the most effective treatment followed by chlorination and then glutaraldehyde. In the field, APT concentrations were higher at midnight and lower at noon in oligotrophic regions on the Pacific Ocean, suggesting a net accumulation from photoautotrophic processes and degradation by grazing and/or viral lysis. This study elucidates the beneficial use of ATP and its role as a proxy of biomass in the fields of ballast water testing and oceanography in general.

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