TRIPLE STRESS: RESULTS OF A LONG-TERM EXPERIMENT TO ASSESS IMPACT OF OCEAN ACIDIFICATION, DEOXYGENATION, AND WARMING ON BENTHIC FORAMINIFERAL COMMUNITY COMPOSITION AND GROWTH

Rising atmospheric carbon dioxide (CO₂) concentrations since the onset of industrialization have caused an increase in oceanic CO₂, leading to decreases in seawater pH (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 (deoxygenation or hypoxia). Numerous studies have investigated the impact of one or two of these environmental stressors, but few experimental studies focus on the simultaneous effects of these three stressors. Here we will describe a 10.5-month experiment in which pCO₂, O₂, and temperature were manipulated to evaluate the sole or combined influence of these stressors on the survival of a benthic foraminiferal propagule community. The community was collected from a ~75-m deep continental-shelf site south of Woods Hole, MA (i.e., the Mudpatch). One agglutinated morphospecies, Bathysiphon cf. B. minuta, grew in each treatment. Occurrence of individual calcareous species was more restricted. Multidimensional scaling analysis indicates that pCO₂ was not the most influential factor and that a compounded effect occurred in the triple-stressor treatment. Additional results on assemblage composition, survivorship and growth will be presented. Supported by NSF OCE-1219948.