Date of Award

2016

Degree Type

Thesis

Degree Name

Master of Science in Oceanography

Department

Oceanography

First Advisor

Susanne Menden-Deuer

Abstract

We measured growth and grazing rates of three heterotrophic dinoflagellate species Oxyrrhis marina, Gyrodinium dominans and G. spirale exposed to starved versus continuously-fed prey conditions and assessed their starvation survival ability. All three dinoflagellate species survived long periods (>10 days) without prey, up to 118 days in the case of O. marina. After 1-3 weeks, starvation led to a 17-57% decrease in grazer cell volume and cells became more deformed and transparent over time. Starved grazers rapidly ingested new prey within 3 hours as evidenced by increased cell volumes of 4-17%. Grazer cultures that were starved had much lower maximum growth rates (-0.16-0.25 d-1) than continuously-fed cultures (0.18-0.55 d-1) at an equivalent prey concentration. This suggested a time lag >3 days for all heterotrophic dinoflagellate species to reach their maximum growth rate. Long survival ability coupled with immediate post-starvation ingestion may offer heterotrophic dinoflagellates an advantage over other grazers (e.g. ciliates) in the ability to exploit patchy prey. Delayed grazer population growth and ingestion after starvation has important implications on how we view predator dynamics in a prey-patchy ocean and especially at the onset of seasonal phytoplankton blooms.

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