Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
  • BCO-DMO Processing Description
  • Problem Description
• Related Publications
• Related Datasets
• Parameters
• Instruments
• Project Information
• Funding

Sampling Plan: Four sampling efforts were conducted (May 2023, August 2023, September 2023, October 2024; note CTD data are not reported from 2024), focusing on five stations located from Charlotte Harbor to the adjacent inner West Florida Shelf (WFS) system directly impacted by Hurricane Ian and the resulting plumes using Mote's R/V Mote (42 ft). At each station, water column CTD profiles of temperature, salinity, dissolved oxygen, and pH were made by lowering the CTD to 5 centimeters (cm) below the water surface and allowing to equilibrate for 2 minutes, then lowering the CTD to 0.5 meters (m) above the bottom. Discrete surface and bottom water samples were collected by Niskin bottles during each cast and analyzed for the biological and chemical parameters and rates listed in the accompanying dataset. CTD data were downloaded immediately upon return to the laboratory each day and data were processed within one week of collection (Seasoft V2 2018).

A Sea-Bird CTD unit was used for measurements of Conductivity, Temperature, and Depth. Specific instruments used were:
Seabird 19 plus v2;
43 oxygen sensor,
18 ph sensor;
Par sensor logic;
Eco flurnet puck;
55 controller.

CTD data were processed using SBEData Processing software (Seasoft V2, 2018), following the software recommendations for compensating for sensor thermal mass, sensor alignment, timing offset (the delay associated with pumped sensors, i.e., conductivity), and changes in instrument velocity (due to ship heave). Data were binned (~0.2 m increments) to smooth data variability and downloaded to Excel.

- Imported data from the original file "RAPID Cruise CTD data -all samples, all stations combined as CSV.csv" into the BCO-DMO processing system.
- Marked "-9.99E-29" as a missing data value (missing values are empty/blank in the final CSV file).
- Renamed columns to comply with BCO-DMO naming conventions.
- Converted local date/time columns into a UTC ISO 8601 datetime column "ISO_DateTime_UTC", applying a fixed US/Eastern (EDT) input timezone offset because all observed timezone labels were EDT.
- Converted the same local date/time columns into a local ISO 8601 datetime column "ISO_DateTime_Local" without timezone conversion.
- Removed the original separate date and time columns.
- Saved the final file as "1004016_v1_ctd.csv".

NSF Award Abstract:
Many coastal systems are facing the threats of continuing development and climate change, including an increased intensity of extreme weather events such as hurricanes. Such storms are now wetter than in prior years because warmer atmospheres hold more moisture. Thus, they release more rainfall and deliver more nutrients and organic matter to coastal areas. This, in turn, leads to phytoplankton blooms with potential for regional “dead zones” or areas with little or no dissolved oxygen. Hurricane Ian, a category 4 hurricane which hit southwest Florida in late September 2022, resulted in immense nutrient and organic carbon inputs to the coastal estuaries and southwest Florida shelf waters and presents an opportunity to examine the effects of a major storm disturbance on a coastal system that is under increasing coastal nutrient stress. The objective of this RAPID project is to examine carbon and nutrient cycling along a gradient of stations from the estuary to low-nutrient shelf waters to determine the rate of change and recovery in this system and the relationship of large hurricane inputs to hypoxia, anoxia, and ocean acidification. These data are being used to develop a regional model to predict the impact of future hurricanes on ocean acidification, phytoplankton blooms, and local hypoxia and anoxia. This study leverages ongoing monitoring programs funded by state and federal management agencies, as well as NSF-supported programs for undergraduate students. It provides partial support for training of postdoctoral investigators and a graduate student. Outreach will include presentations to elementary and high school students.

In September 2022, southwest Florida experienced a direct hit from category-4 Hurricane Ian, resulting in extensive watershed flooding and nutrient- and dissolved-organic-matter-laden estuarine plumes extending more than 50 miles onto the shallow oligotrophic west Florida shelf (WFS). The massive terrestrial organic carbon and nutrient inputs to the southwest Florida coastal and shelf region may be priming this oligotrophic system for extensive phytoplankton blooms, as well as significant changes in carbon chemistry and nutrient cycling that could lead to longer-term regional hypoxia and anoxia. In this RAPID project, the investigators are measuring a suite of carbon and nutrient parameters, as well as carbon and nutrient cycling, at stations in Charlotte Harbor and the adjacent inner WFS system in December 2022, February 2023, and September 2023. The objectives are to assess: 1) a timescale of system responses from shorter (weeks to months) to 1-year impacts post-hurricane; 2) how nutrient availability and forms influence hypoxia; and 3) how hurricane-driven inputs influence carbonate chemistry in this system, specifically the connection between acidification and hypoxia. The investigators are using new data collected in this study and monitoring data from regional state and federal programs in a coupled hydrodynamic-biogeochemical model to understand conditions on the WFS. Hindcast simulations and modeling experiments are assessing how large inputs of nutrients and organic matter affect phytoplankton, oxygen conditions, and carbon chemistry. Modeling experiments are exploring how storms of varying wind and precipitation intensity affect the WFS and estuaries, identifying the tipping point at which the WFS switches from episodic to persistent hypoxia.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.