On the Respiratory Metabolism of Marine Plankton: A Time-Course Study in Bacteria and Medusa

Abstract

Respiration is an ancient process, and a ubiquitous component of contemporary biospheric metabolism. The respiratory rate, represents the activity of catabolic biochemical pathways. It is the process by which energy is transformed within an organism and, on much a larger scale, within the biosphere, itself. Stressors, such as those associated with anthropogenic climate change can impact the physiology of an organism. Bacterioplankton and gelatinous zooplankton are a conspicuous component of marine ecosystems. However, their respiratory metabolism is widely approached by allometric scaling, and CO2 production is estimated by using a constant, the respiratory quotient (RQ). These practices present restrictions. In this thesis, we use physiological respiration rates (O2 consumption and CO2 production) in addition to respiratory enzymatic rates, to study the physiology of marine bacteria and the medusozoan jellyfish, A. aurita. In addition, we explore the respiratory metabolic response of these organisms under stress conditions. In Chapter 2, two marine bacterial species were cultured from nutrient-sufficiency to nutrient-limitation under two different carbon sources (food type). In Chapter 3, A. aurita polyps were exposed to a simulated marine heatwave and their changes in respiratory enzymology and physiology documented. In Chapter 4, the metamorphosis of A. aurita was monitored from polyp to the medusa life-stage. The studies here elucidate the metabolic response of marine bacteria in post-bloom conditions as one finds in an oligotrophic ocean. In parallel, these studies document the performance of the jellyfish A. aurita and their potential proliferation in conditions predicted for our changing oceans.