Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Related Publications
• Parameters
• Instruments
• Project Information
• Funding

Raw water surface samples were collected at sites along the Neuse River (NR), Neuse River Estuary (NRE), and Pamlico Sound (PS) in North Carolina over a period of three months, between October and December 2016, following the passage of Hurricane Matthew on October 9, 2016. Sampling was conducted approximately weekly across the NR, NRE, and PS sites. Riverine samples were collected, in 1 L brown HDPE bottles, from bridge overpasses along the main-stem of the NR at USGS gaged locations. Estuarine and sound samples were collected, in 1 L opaque HDPE bottles and frozen for shipment to NCSU, by the Neuse River Estuary Modeling and Monitoring Project ("ModMon") located at the University of North Carolina at Chapel Hill's Institute of Marine Science (UNC-IMS) in Morehead City, NC. Collection bottles were cleansed in a detergent bath, rinsed profusely with Milli-Q ultrapure water, and left to air dry before sampling. We conducted additional sampling in an area of freshwater riparian wetlands between the last riverine site on the NR near Fort Barnwell, NC and first estuarine site on the NRE at the Street's Ferry Bridge crossing near Vanceboro, NC in March and October 2017.

Raw water samples were thawed at room temperature, and a known volume of water was filtered through pre-combusted (at 45C for 5 hours) 0.7 m Whatman glass fiber filters (GF/F) via vacuum. Prior to sample filtration, 150 mL of Milli-Q water was used to rinse each filter. The filtrate was collected into 60 mL polycarbonate bottles (detergent-washed and rinsed thoroughly with Milli-Q water) for optical analyses and 40 mL amber-tinted borosilicate glass vials (detergent-washed, rinsed thoroughly with Milli-Q water, and combusted at 45C for 5 hours) for dissolved organic carbon (DOC) concentration and stable carbon isotope (13C-DOC) analyses. Filtrate was stored at 4C until optical measurements were made, generally within 48 hours. Filtrate for DOC analysis was acidified to a pH of 2 with 85% phosphoric acid (H3PO4), then stored at 4C until measurements were completed. GF/F filters were stored at -20C until particulate organic carbon (POC) concentration and stable carbon isotopes (13C-POC) could be measured.

Absorbance measurements were made with a Varian Cary 300UV spectrophotometer in 1 cm quartz cuvettes, over a range of wavelengths (200-800 nm), and then blank corrected using Milli-Q ultrapure water. (Osburn and Morris, 2003)

Fluorescence was measured on a Varian Eclipse spectrofluorometer under the following conditions: excitation (Ex) wavelengths from 240 to 450 nm at 5 nm intervals, emission (Em) wavelengths from 300 to 600 nm at 2 nm intervals. The fluorescence data was concatenated into excitation-emission matrices (EEMs), which display qualitative information about OM within a system, such as the sources of organic matter (Coble, 2007).

Samples for DOC were immediately filtered through 0.2 um polyethersulfone filters into glass vials, capped with Teflon-lined septa and stored without headspace at 4C until analysis. DIC concentration ([DIC]) and delta-13C-DIC value was measured on a OI Analytical TOC analyzer (Doctor et al., 2008)

To quantify DOC concentration, [DOC], samples were first sparged with ultrapure Argon gas for 20 minutes to remove dissolved inorganic carbon (DIC). Sparged samples were analyzed on an OI Analytical 1030D Aurora total organic carbon analyzer, using wet chemical oxidation, coupled to a Thermo Delta V Plus isotope ratio mass spectrometer (IRMS) to determine stable isotope values, expressed as the standard delta notation, 13C-DOC (Osburn and St. Jean, 2007). [DOC] were blank-corrected for ultra-pure Milli-Q water, then calculated using a linear regression curve of known caffeine standards with concentrations from 1 to 20 mg C per L. 13C-DOC values were blank corrected and referenced to the Vienna Pee Dee Belemnite (VPDB) scale via a linear regression of six caffeine (IAEA-600, -27.7 +/- 0.04‰) and two sucrose (IAEA-C6, -10.8 +/- 0.03‰) International Atomic Energy Agency (IAEA) standards. Precision for [DOC] and 13C-DOC values were +/- 0.4‰ based on reproducibility and calibration to sucrose standard. Milli-Q blanks were ran every 10 samples for quality control and confidence of instrument.

Frozen GF/F filters were thawed, then dried at 60C for at least 24 hours in an oven to prepare for measurement of particulate carbon and nitrogen concentrations ([POC] and [PN] respectively) and the stable isotope of [POC], 13C-POC. Analysis was conducted on a Thermo Finnigan Flash Series 1112 Elemental Analyzer (EA), coupled to a Delta V IRMS via a Conflo III interface. Calibration curves were made using acetanilide, L-glutamic acid (USGS-40), caffeine (IAEA-600), oxalic acid (NIST-4990C), and sucrose (IAEA-C6) standards. Weighed standards (0.200-0.600 mg) were placed in low blank tin capsules (4 x 6mm), while dried GF/F filters were folded then placed in larger low blank tin capsules (10 x 12mm). Carbon and nitrogen peak locations on the EA, [POC], and [PN] were determined using acetanilide standards with percent content values of 71.09% and 10.36% for carbon and nitrogen, respectively. 13C-POC for each sample was determined by converting the measured value to the VPDB scale using a linear fit regression of the L-glutamic acid (-26.39‰), caffeine (-27.77‰), oxalic acid (-17.8‰), and sucrose (-10.8‰) standards. Similar to the precision for [DOC] and 13C-DOC, 13C-POC values were +/- 0.4‰ based on reproducibility and calibration to known standards.

Synoptic measurements were collected using a handheld YSI probe and include salinity, pH, temperature, dissolved oxygen concentration (DO), DO saturation (%DO), Total Dissolved Solids (TDS), and Specific Conductivity (Spec. Cond.).

Data Processing: Excel used for spreadsheets; Matlab (v 2016 to 2018) is used to process absorbance and fluorescence results and data and to conduct statistical testing. SigmaPlot is used for data visualization. 

Problem Report: Some gaps in data occur when sample sites were inaccessible or when samples were lost during shipment or during analysis.

BCO-DMO Processing: modified parameter names (removed special characters; replaced spaces and hyphens with underscores; added "peak" to peak ratios for clarity).

NSF abstract:

This project constitutes a rapid-response effort to investigate the effects of the extreme flooding event of Hurricane Matthew on coastal cycling of carbon and nutrient elements. The investigators aim to improve our understanding of how estuaries and coastal systems respond to extreme events by measuring carbon, nitrogen, and phosphorus loading into the Neuse River Estuary-Pamlico Sound (NRE-PS) coastal ecosystem. The NRE-PS is the urgent study site to examine resulting effects of Hurricane Matthew on coastal environments because it is downstream of the most intense flooding that occurred, and it is located on the North Atlantic "hurricane track", likely to be impacted by future extreme events. Furthermore, it is the focus of a long-term monitoring program in that system, the Neuse River Estuary Modeling and Monitoring Program (ModMon), which was initiated in 1993. That date is significant because it preceded a recent rise in Atlantic tropical cyclone activity and has been able to capture the biogeochemical and ecological effects of major storms that have impacted the NC coast, including Hurricanes Fran (1996), Floyd (1999), Isabel (2003), and Irene (2011). Incorporating intensive sampling of the Hurricane Matthew flooding in the context of these ongoing observations will enable a comparison of the material fluxes into this coastal environment resulting from a major tropical storm and provide a comparison with other coastal environments. Outcomes of this work will be communicated widely via existing outreach efforts of each investigator's research programs to local and regional resource managers, regulators, and other stakeholders. Nutrient loading will be critical information for stakeholders because the Neuse Estuary is an EPA 303(d) listed waterway impaired for nitrogen. Project results can aid in understanding the effects of extreme weather events on ecosystem disturbances and inform coastal carbon flux estimates.

Specific questions to be addressed in the context of this project include: 1) How do coastal carbon and nitrogen budgets respond to floodwaters from tropical storms and hurricanes? 2) What is the biological and photochemical reactivity of this material? The first question can be answered via a relatively short, yet intense, period of observations, such as is proposed here. The second question, which has potential teleconnections to climate in terms of carbon fluxes, food web responses, and other ecosystems processes, requires a longer duration study. However, Question 2 could be answered by further study of samples collected during a short and intense period of sampling proposed to answer Question 1. Work proposed in this project will result in estimates of fluxes and reservoirs of key constituents such as dissolved inorganic carbon (DIC), dissolved and particulate organic carbon and nitrogen (DOC, POC, DON, PON), and N and P nutrients, as well as chlorophyll biomass and pigment analyses.