DOI: 10.6084/m9.figshare.21430194.v1
title: Oxygen profiles in estuarine sediments exposed to acidification

description: We collected twelve sediment cores from two sites in Waquoit Bay (Massachusetts, USA): Metoxit Point (MP) in September 2021 and from Sage Lot Pond (SLP) in October of 2021. We collected the cores using a pull corer which maintains the vertical structure of the sediment cores and preserves the delicate sediment-water interface (Foster and Fulweiler 2019). We transported the cores back to Boston University within 7 hours of collection and placed them in an environmental chamber set to 29 (±1) °C. To better understand the impact of pH of sediment biogeochemical cycling we conducted continuous flow through incubations with treatments representing control (pH 8.0), moderate (pH 7.3) and extreme pH conditions (pH 6.3). Site water was treated with ambient air and CO2 to reach appropriate pH conditions. We conducted triplicate sediment O2 profiles within each core before and after incubations to measure the treatment effects of pH on O2 conditions within sediments. Using a standard 100-µm O2 microelectrode (100 µm diameter) mounted on a motorized micromanipulator profiler and the Sensor Trace Pro v. 3.0.6 control software (Unisense, Aarhus, Denmark) we measured O2 concentrations at 250 µm increments down to 1 cm. All calibrations and measurements were done in the lab at ambient air temperature. Email questions and comments to cmazur@bu.edu <strong>Sampling Sites:</strong> Metoxit Point = 41° 34’ 8.04” N 70° 31’ 17.76” W Sage Lot Pond = 41° 34’ 8.04” N 70° 30’ 30.20” W <strong>Profiling Information:</strong> Experiment Type = For each station we conducted two incubations. The first incubation conducted was the Extreme treatment (pH 6.3) which included 3 control cores and 3 cores acidified to a pH of 6.3. The second experiment conducted was the moderate treatment (pH 7.3). Treatment = The treatment each cores were exposed to: Control = pH 8.0 pH 6.3 = Extreme pH 7.3 = Moderate Incubation_Time = When profiles was collected either before incubation (Pre-Incubation) or after incubations (Post-Incubation). Depth_mm = sampling depth in millimeters Oxygen = oxygen concentration (µmol L-1) SE = standard error of triplicate oxygen measurements Group = detailed descritpion of oxygen profile <strong>Acknowledgements:</strong> We would like to thank the Waquoit Bay National Estuarine Research Reserve (WBNERR) for their support of our research. Sediment cores for this study were collected using WBNERR boats. We are particularly grateful for Dr. Megan Tyrrell and Tonna-Marie Rogers who were instrumental in helping us carry out fieldwork and for making sure we had all the resources necessary for a successful field day. We would also like to thank members of the Fulweiler Lab, Alia Al-Haj, Amanda Vieillard, Catherine Mahoney, Kwetzpallin Mexika, Melissa Ederington Hagy, Nia Bartolucci, Paulina Azzu, and Ryan Shipley for their help with sample prep, field work and experiments. <strong>References</strong> Foster SQ, Fulweiler RW (2019) Estuarine Sediments Exhibit Dynamic and Variable Biogeochemical Responses to Hypoxia. J Geophys Res Biogeosciences 124:737–758. https://doi.org/10.1029/2018JG004663 <strong>Funding</strong> This work was funded by MIT SeaGrant through grants to RWF and by the NOAA Margaret A. Davidson Graduate Fellowship awarded to CIM. CIM received additional support from the Mount Holyoke Alumnae Fellowship, the Warren-McLeod Graduate Fellowship from the Boston University Marine Program, and from Boston University’s Department of Earth & Environment.