Mesoscale Eddies Influence Coral Reef Environments in the Northwest Gulf of Mexico
Creators: name: McWhorter
name: Cornec
name: Frenzel
Publisher: name: Zenodo
Year: 2024

description: Download the entire zip folder and then run the main scripts with your respective file paths in R. The file paths throughout the temperature and salinity main scripts will need to be changed to your local path. Do not alter the structure of the zip folder (i.e. move functions in different paths). Please contact Jennifer McWhorter for further questions. 

 

Data & Methods

Study Area

FGBNMS is the only national marine sanctuary in the Gulf of Mexico, located 50 to 77 miles (80 to 123 km) off the coasts of Texas and Louisiana and ranging in depth from 16 to 220 m. FGBNMS consists of a combination of 17 reefs and banks perched atop underlying salt domes along the continental shelf forming a chain of protected habitats including thriving shallow water coral reefs, algal-sponge communities, and mesophotic reefs comprised of black coral, octocoral, and algal nodule habitats (Etnoyer et al., 2021; Rezak et al., 1985). The original three banks of FGBNMS included East Flower Garden Bank, West Flower Garden Bank, and Stetson Bank, and 14 more banks were added in 2021, including Horseshoe, MacNeil, Rankin, 28 Fathom, Bright, Geyer, Elvers, McGrail, Bouma, Sonnier, Rezak, Sidner, Parker, and Alderdice Banks (86 Fed. Reg. 4937 [Jan 19, 2021]). The study area for this paper includes all 17 reefs and banks of FGBNMS. The depth range of 0 to 150 m was selected for analysis as East and West Flower Garden Banks span from 14 to 150 m containing the most well-studied and most dense coral cover in the sanctuary (Johnston et al., 2016; Johnston, Hickerson, et al., 2019; Johnston, Nuttall, et al., 2019).

Core Argo Array

 Core Argo floats, which are autonomous open ocean profiling floats (collecting data from 0-2000 m), were first deployed to collect data in the Gulf of Mexico in 2003 but the array expanded largely in 2010 (Supplementary Figure 1). These Lagrangian open ocean profiling floats measure temperature, salinity, and depth. Generally, Argo floats collect a 2,000 m profile once every 10 days. Data from the international Argo program can be accessed from one of two identical global data assembly centers and are available in near-real time (see data availability section (Argo, 2020)) (A. P. Wong et al., 2020). 

The OneArgo-R toolbox (Cornec et al., 2022) and the ‘argodata’ package in R (Kelley et al., 2021) were used for the Core Argo float selection process. Core Argo floats were selected based on location in the western Gulf of Mexico (28.5-25.5oN, 95.8-89.3oW) and filtered to select delayed mode (D mode) temperature and salinity data with a quality control flag of 1 (n=1710, 2003-2022) (A. Wong et al., 2022; A. P. Wong et al., 2020). Salinity values were also filtered to select the salinity values within 33-38 PSU as even with quality control flags some data appeared to be unrealistic. The Mixed Layer Depth (MLD) was calculated using a density threshold method (de Boyer Montégut et al., 2004; Holte & Talley, 2009) that used float temperature and salinity data in the OneArgo-R toolbox (Cornec et al., 2022). This method examines deeper levels of density until a depth level is found that is 0.03 kg m-3 greater than the 10 m reference depth value (de Boyer Montégut et al., 2004). 

Argo float measurements are not taken at fixed depths; therefore, a depth interpolation was used to create a standardized grid using 0.2 m intervals from 0-2000 m with a linear interpolation across variables (See data availability section for code details). A linear interpolation was then used between observed temperature levels (Suga et al., 2004) to extract the depth that best falls under the difference criteria (de Boyer Montégut et al., 2004; Cornec et al., 2022; Frenzel et al., 2022). The means and standard deviations were then taken within each depth for temperature and salinity by month and eddy type (anticyclonic eddy, cyclonic eddy, and no eddy) across the timeseries.

The Core Argo float hydrographic profiles and associated mixed layer were then associated with an eddy type; anticyclonic eddy, cyclonic eddy, or no eddy using the adapted multiparameter mesoscale eddy tracking method discussed in sections 2.3 and 2.4 (Roman‐Stork et al., 2023). Across the entire Gulf of Mexico domain, on average there were 42 (+-11) anticyclonic eddy profiles, 43 (+-9) cyclonic eddy profiles, and 57 (+-14) no eddy profiles for each month from 2003-2022 within 28.5-25.5oN, 95.8-89.3oW (Supplementary Figure 1). 

Data from 0-150 m were prioritized for analysis to emphasize the hydrographic data directly associated with ‘shallow’ corals (14-30 m) and mesophotic (30-150 m) coral reef communities found on FGBNMS.