Book Description

Phytoplankton are a sentinel class of organisms in the marine environment. Through their photosynthetic activity in sunlit waters worldwide, phytoplankton shape the health and productivity of marine ecosystems and impact the global climate. In this work a range of ocean sensing technologies (via ships, surf zone sampling, moorings, gliders, and satellites) are applied to investigate phytoplankton bloom dynamics from event to regional and climate scales along the Oregon coastal region, a productive eastern boundary upwelling regime. Chapters 2 and 3 investigate patterns in, and mechanisms behind, Oregon coastal harmful algal blooms (HABs). Chapter 2 presents the temporal and spatial occurrence of HAB events in this region and investigates ecological conditions associated with them. Elevated HAB activity was observed in 2009-2010 and coincided with anomalously warm ocean conditions, specifically a brief change in the Pacific Decadal Oscillation (PDO) to a warm phase and a coincident El Nino event. Through these analyses, key parameters came to the forefront as informative to future monitoring efforts such as wind stress, a metric for when putative blooms may move on/off shore, particulate dissolved domoic acid in surface waters, and the abundance of Alexandrium spp. which appear to be strongly predictive of potential saxitoxin contamination of shellfish. Chapter 3 provides the first evidence of climatic regulation of domoic acid in shellfish over the past 20 years in the Northern California Current regime. The timing of elevated domoic acid and changes in plankton communities are found to be strongly related to warm phases of the PDO and the Oceanic Nino Index, an indicator of El Nino events. Based on these findings, a risk assessment model is developed to forecast bloom events. Chapter 4 explores patterns in the surface (horizontal) and depth (vertical) distribution of phytoplankton based on the universal autotrophic pigment chl-a. Results were considered with respect to season (upwelling or downwelling) and region (high chl-a nearshore to low chl-a offshore). Applications of glider-based primary productivity models to evaluating satellite-based estimates of ocean primary productivity are discussed. The research presented in this dissertation shows the power of long-term ocean observations from a variety of vantage points to describe the patterns and processes in the vast ocean that affect the tiniest of Earth's photosynthetic life.