Generating ecologically relevant oxygen fluctuations using marine primary producers under laboratory conditions

Abstract

Incorporating near-natural variation of marine environmental variables into experimental designs is becoming imperative to make ecologically relevant inferences about ecophysiological responses to climate global change. Dissolved Oxygen (DO) is among the most important environmental variable in marine ecosystems and fluctuates strongly in coastal habitats, due to physical and biological phenomena. However, many technical challenges are still imposing high-cost equipment to ensure a complete mimicry of DO fluctuations in manipulative experiments. Here, we propose a simple and cost-effective methodology to simulate the oxygen fluctuations in the laboratory through to marine primary producers as source of natural fluctuations. We tested the physiological status (Yield II and F_v/fm) as a proxy of oxygen evolution, and photoprotective responses (phenolic production), as metabolic stress indicator in five different biomasses (200–400–600-800-1000 g; that correspond to 6–12–18-24-30 g l⁻¹, respectively) of the macroalgae Lessonia spicata exposed to 7 days of artificial light (photoperiod of 12:12 h day: night) within replicated aquaria. We showed that each biomass exhibited a unique fully functional oxygen fluctuating profile with different average DO saturations, harmonic oscillations and rates of DO production/consumption. Biomasses <600 g showed no significant changes in the physiological status of macroalgae (Yield II and F_v/fm) and photoprotective responses (phenolic production) during the 7 days experiment, while effects of the environmental stress were found at greater biomasses (800 and 1000 g). We successfully tested a method that can produce daily cycles of DO fluctuations in seawater trough to marine primary producers under controlled environment conditions. Our quantitative method provides cost-effective control the DO fluctuations in experimental set-ups with the use of a primary producers that can be replicated at low cost in virtually any laboratory worldwide using other species of marine algae, representing a highly effective method to control experimental settings that involve testing of fluctuating and ecologically relevant levels of dissolved oxygen.