IMPACT OF COMPOUNDED GLOBAL CHANGE SINCE INDUSTRIALIZATION: CHANGES IN BENTHIC FORAMINIFERAL ASSEMBLAGES ON THE CONTINENTAL SHELF OFF SOUTHERN NEW ENGLAND

The rise in atmospheric CO₂ since the start of global industrialization has caused average sea surface temperature (SST) to increase over the last 100 years, lowered the pH of the oceans, and extended and intensified the impact of low-oxygen bottom waters, at least in certain oceanic regions. The biological and ecological impacts of these ongoing changes – warming, acidification, and hypoxia – have each been studied independently, but few studies have explored the possible interactions among these stressors. An ongoing project is using culturing approaches to determine the compounded impacts of predicted acidification, oxygen depletion, and warming on the benthic foraminiferal assemblage from a continental shelf site south of Massachusetts. The employed experimental design will also allow us to differentiate between these stressors. As part of this project, it is important to establish the benthic foraminiferal assemblage composition during pre-industrial times to serve for comparison with our experimental results as well as present-day assemblages. Industrialization is generally agreed to be the time when anthropogenic carbon dioxide began to accumulate in the atmosphere, thereby beginning the cascade of climate-change events manifest as warming, acidification, and hypoxia. Thus, suites of MC800 multicores were collected in May 2013 from the southern shelf of Massachusetts in ~80-m water depth. The surface cm of triplicate cores was each incubated in the viability indicator CellTracker Green CMFDA (Life Technologies) to document the living benthic foraminiferal assemblage. Other multicores were sliced in 1-cm intervals to their maximum depth (~30 cm). To determine down-core age estimates, aliquots of selected intervals of one core were analyzed for ²¹⁰Pb. Aliquots of subsurface intervals dated at approximately 1850 CE were picked for benthic foraminifera. Analysis comparing present day living (CellTracker Green labeled) and total surface (0-1 cm) assemblages to down-core (pre-industrial) assemblages will be presented along with initial culturing results obtained from the pre-industrial treatment (275 ppm CO₂, 21% O₂). Supported by NSF OCE-1219948 to JMB.