Seminar: Hans Paerl – UNC IMS

UNC-CH’s Department of Marine Sciences is proud to host a guest seminar by Hans Paerl. This event is scheduled for Wednesday, February 3rd, at 12:30 pm. This seminar is remote only and will be broadcast live online via Zoom (Meeting ID: 934-0604-8353).

Presenter Affiliation: Kenan Distinguished Professor, Institute of Marine Sciences, University of North Carolina at Chapel Hill

Title: The ‘new normal’ of catastrophic tropical cyclone flooding in Coastal North Carolina: Biogeochemical and water quality implications

Abstract: North Carolina’s (USA) semi-lagoonal Pamlico Sound (PS) and its sub-estuaries have witnessed 25+ years of elevated tropical cyclone activity, including recent record rainfalls associated with three major hurricanes; Floyd (1999), Matthew (2016) and Florence (2018). Using the long-term UNC-Ch/NC-DEQ collaborative water quality monitoring programs ModMon and FerryMon, we examined freshwater and nutrient impacts of these events on the productivity, biomass and composition of dominant primary producers, phytoplankton, in order to address a key question: “Are these events ushering in a state change at the base of the food web or does the system exhibit resiliency by being able to return to pre-cyclone conditions on annual scales?” The lagoonal nature of PS may promote a legacy of nutrient and organic matter enrichment, leading to longer-term trophic changes, with subtle, yet significant increases in the frequency of harmful algal blooms (cyanobacteria and dinoflagellates) and changes in habitat conditions, including vertical salinity stratification and bottom water hypoxia and altered nutrient and carbon cycling. Therefore, a critical secondary question is whether these legacy effects cause the time scale of recovery for trophic conditions to lag behind recovery of normal hydrological conditions as determined by salinity. Our analyses indicate large-scale changes in associated with carbon and nutrient inputs from major hurricanes, including elevated nutrients, dissolved organic matter, and low salinity-preferring phytoplankton taxa. Recovery times to “baseline” water quality and habitat were compared across events. Results indicate that legacy effects of the storms varied substantially, but overall, the estuary shows resilience in its biological and biogeochemical processes. However, the projected increase in frequency of these events may lead to unstable conditions as the system is recovering from one event only to be impacted by the next. The ramifications of the “new normal” of an increased frequency of high rainfall and flooding events on long-term sustainability of of the PS and its tributaries will be discussed.

Hans Paerl, Nathan Hall, Karen Rossignol, Jeremy Braddy, Randy Sloup, Amy Bartenfelder, Betsy Abare, Rick Luettich, UNC-Chapel Hill Instit. Marine Sciences, collaborators at UNC-Chapel Hill, NC State University, Virginia Tech, CSIRO-Brisbane, Australia, NC Depts. of Environmental Quality and Marine Fisheries, Neuse and Pamlico River Keepers, and others!

Water Quality Monitoring Websites: ModMon, http://paerllab.web.unc.edu/projects/modmon/
FerryMon, http://paerllab.web.unc.edu/projects/ferrymon/