These data include the measurements of oxygen, temperature, and salinity from incubations to measure rates of oxygen production in the light by primary production and oxygen consumption in the dark by community respiration. Data were collected during four cruises in 2017 during April, July, September and October. The September and October cruises followed the landfall of Hurricane Harvey. Cruises were conducted aboard the R/V Pelican in April (PE17-18), July (PE18-02), and October (PE18-11) and aboard the R/V Acadiana (AC18-12) in September. The study domain included the Louisiana and Texas continental shelf from the Mississippi River Bird's Foot delta to south of Galveston Bay. The objective of this work was to quantify how hurricanes and tropical storms affect metabolic rates and the concentrations of oxygen and DIC/pH. These data assess the water column response in metabolism before and after Hurricane Harvey and were collected by Dr. John Lehrter of the University of South Alabama.

Table of Contents

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

Samples for plankton community respiration (WR) measurements were collected from several depths in the water column including the surface layer, the bottom layer, the layer at depth of chlorophyll maximum, midwater oxygen maximum, and midwater oxygen minimum. For each sample collected, three transparent (light) glass bottles and three dark glass bottles were filled directly from the ship's Niskin bottle array (Murrell and Lehrter, 2011). Aliquots were put into acid-cleaned 300 milliliter BOD (biochemical oxygen demand) bottles for light-dark incubation experiments. After initial O₂ measurements were taken (T0), samples were placed in a darkened incubator that maintained surface water temperatures using water supplied continuously from the ship’s hull pump. Light bottle treatments were incubated in an outdoor incubator with screening that reduced ambient light by 50%. Dark bottle treatments were also placed in the outdoor incubator but were kept dark by their black liners and caps. 

For more detailed methods see Murrell et al. (2013) and Murrell and Lehrter (2011).

Concentrations of O₂ were measured initially and after 24 hours using a Hach or YSI oxygen sensor and temperature probe. Salinity values for each sample were obtained from the ship's CTD (SeaBird 911). Net primary production rates were calculated as the change in O₂ over time in light bottles screened at 50% of ambient sunlight and incubated for 24 hours, expressed in units of millimoles oxygen per cubic meter per day (mmol O₂ m^-3 d^-1). Respiration rates were calculated as the change in O₂ over time in dark bottles incubated for 24 hours, expressed in units of millimoles oxygen per cubic meter per day (mmol O₂ m^-3 d^-1).

Problem report: Some of the incubation bottles had their caps come off during incubations. These values are labeled as NAN (not a number) in the dataset.

Note: Dissolved oxygen data were recorded in mg/L for the April 2017 cruise and in percent saturation for the July and September cruises.

Please see the Supplemental Files section for equations in more easily readable format, along with a brief summary of the method for light and dark bottle oxygen assay to measure primary production and respiration

Net primary production, respiration, and gross primary production calculations
Rates were adjusted to initial temperatures using the Arrhenius equation and initial and final temperatures.

Variables:

• NPP is Net Primary Production 
• R is Respiration
• GPP is Gross Primary Production
• NPP_T is Temperature adjusted net primary production
• R_T is Temperature adjusted respiration
• GPP_T is Temperature adjusted gross primary production 
• DO_Light is the dissolved oxygen concentration in the light bottles
• DO_Dark is the dissolved oxygen concentration in the dark bottles
• TF = time final
• T0 = time initial

Equations:  (see Supplemental Files section)
NPP = (DO_Light_TF - DO_Light_T0)/(TF - T0)
R = (DO_Dark_TF - DO_Dark_T0)/(TF - T0)
GPP = NPP - R
NPP_T = NPP*2^((T_T0 - T_TF)./10)
R_T = R*2^((T_T0 - T_TF)./10)
GPP_T = GPP*2^((T_T0 - T_TF)./10)
 

Coverage: Northwestern Gulf of Mexico

NSF Award Abstract:
Understanding how extreme events, like hurricanes, impact coastal ecosystems and the cycling of elements like carbon and oxygen, is important for improving our ability to predict how the global carbon cycle will respond to climate. This team of investigators, who have already been working together on understanding the carbon cycle in the Gulf of Mexico continental shelves, have important recent data against which to measure the effects of the passage of Hurricane Harvey in August, 2017. They will sample the waters and sediments of the northwestern Gulf of Mexico in September, October, and January to assess Harvey's impacts on a timescale of weeks to months.

The researchers pose three specific questions: 1. Will the region become a major source of carbon dioxide to the atmosphere, releasing carbon accumulated in the bottom water and sediments, and will this potential impact be faster and greater than during normal fall and winter mixing events? Will this process acidify the surface water and for how long? 2. Will the metabolic balance be substantially pushed toward net heterotrophy as a result of the storm in comparison to other years? 3. Can the amount of material delivered or redeposited across the continental shelf by a tropical cyclone be considerably larger than that related to winter storm systems? The PIs will measure water column nutrients, oxygen, organic carbon, and inorganic carbon system parameters; determine water column and benthic metabolic and nutrient flux rates; and sediment organic matter deposition rates. They will also collect end member river samples. They will compare the immediate (mid-Sept) but limited post-hurricane data and one-month post-hurricane, more detailed data with those collected in July and April to study the impacts of the storms. they will also compare 2017-2018 seasonal data to seasonal data over the same region collected in the past (2006-2008 and 2009-2010). They will also compare the impacts of Hurricane Harvey to those of Hurricanes Katrina and Rita (2005) and Tropical Storm Cindy (June 2017). The project will involve graduate and postdoctoral research and work to communicate results to the public.