Investigating the Role of H2S Stress on the Photochemical Efficiency of Phytoplankton Found in the Delaware Inland Bays: A Field and Laboratory Study

By combining laboratory and field studies we investigated how increased concentrations of dissolved sulfide in the Delaware inland bays affect the photochemical efficiency of several species of phytoplankton found locally. During the summer months some sites in the Delaware inland bays reach over one millimolar H2S. A Satlantic in situ FIRe (fluorescence induction and relaxation) sensor was used to monitor the changes in the photochemical efficiency, Fv/Fm, of PSII. An in situ voltammetry system was also deployed and used to monitor spatial and temporal changes in O2 and H2S using Au/AuHg microelectrodes. Data will be presented correlating seasonal changes in redox chemistry to in situ values of Fv/Fm, with decreases in Fv/Fm signifying organism stress. Laboratory studies will also be shown that specifically investigate the tolerance of several local phytoplankton species to varying sulfide concentrations and exposure time. Initial field data indicate significant stress in the presence of sulfide with large decreases in Fv/Fm observed. Laboratory data show the negative photochemical response of several local phytoplankton species to H2S concentrations similar to those observed in the Delaware inland bays. These data aim to help improve our understanding on how increasing sulfide concentrations effect photosynthetic processes in the Delaware inland bays, but can also have implications for other ecosystems that undergo seasonal stratification and sulfidic condtions.