A short-term survival experiment assessing impacts of ocean acidification and hypoxia on the benthic foraminifer Globobulimina turgida

Abstract

The oceans are absorbing increasing amounts of carbon dioxide (CO2) as a result of rising anthropogenic atmospheric CO2 emissions. This increase in oceanic CO2 leads to the lowering of seawater pH, which is known as ocean acidification (OA). Simultaneously, rising global temperatures, also linked to higher atmospheric CO2 concentrations, result in a more stratified surface ocean, reducing exchange between surface and deeper waters, leading to expansion of oxygen-limited zones (hypoxia). Numerous studies have investigated the impact of one or the other of these environmental changes (OA, hypoxia) on a wide variety of marine organisms, but few experimental studies focus on the simultaneous effects of these two stressors. Foraminifera are unicellular eukaryotes (protists) that live in virtually every marine environment and form an important link in the benthic food web. Here we present results of a short-term (3.5 week) study in which both CO2 (OA) and O2 (hypoxia) were manipulated to evaluate the influence of these parameters on the survival of the benthic foraminifer Globobulimina turgida. Elevated CO2 concentrations did not impact short-term survivorship of this species, and furthermore, G. turgida had higher survival percentages under hypoxic conditions (0.7 ml/l) than in well-aerated water, regardless of CO2 concentration.