California Sea Grant College Program

This dissertation provided novel insights on the dynamics and consequences of harmful algal blooms (HABs) in the California Current System (CCS). Parasitism is described as a biological control agent of harmful dinoflagellate blooms and referred to as a novel factor influencing HAB dynamics in coastal upwelling environments. Chapter 1 documented, for the first time, the presence of Amoebophrya, an endoparasitic dinoflagellate that infects and kills 7 bloom-forming dinoflagellate host species that occur throughout the CCS. Chapter 1 also discussed parasitism effects on (1) host population dynamics, (2) dinoflagellate species diversity, (3) net phytoplankton community composition and (4) trophic web structure within the planktonic community of an upwelling environment. Chapter 2 specifically verified the role of such a parasite in controlling harmful dinoflagellate blooms caused by one of its hosts in Monterey Bay. Findings of Chapter 2 suggested that blooms might develop when the host ‘escapes’ parasitism by Amoebophrya. In contrast, epidemic parasitic outbreaks may contribute to stoping or preventing the occurrence of dinoflagellate harmful blooms. Chapter 3 and 4 focused on the consequences of HABs caused by diatoms of the genus Pseudo-nitzschia, which cannot be parastitized by Amoebophrya and produces the neurotoxin domoic acid (DA). Chapter 3 verified that human consumers of recreationally-caught fishes can be exposed to asymptomatic doses of domoic acid. Lastly, Chapter 4 dealt with the hypothesis that the pelagic predator Humboldt squid (Dosidicus gigas), which recently invaded the domains of CCS, is exposed to domoic acid. However, beach strandings of this species in Southern California could not be linked to domoic acid exposure and was likely related to other unknown causes.