Spatiotemporal Impact of the Deepwater Horizon Oil Spill on Benthic Meiofauna Communities

Abstract

In April 2010, the catastrophic Deepwater Horizon (DWH) oil spill began in the northern Gulf of Mexico. Millions of barrels of oil contaminants were expelled from the wellhead at a water depth of 1525 meters, in what would be one of the largest oil spills in history. A large portion of these contaminants remained in the deep-sea and severely impacted the benthic ecosystem, especially meiofaunal organisms. The initial impact of the DWH oil spill on these organisms, along with their subsequent recovery, were studied in 2010, 2011, 2014, and 2022. Thirty-four stations, consisting of eight highly impacted stations, eleven moderately impacted stations, six low impacted stations, and nine non-impacted stations, were consistently sampled to observe the effects of the spill on the benthic meiofauna community. Meiofaunal abundance was impressively high (i.e., disproportionately high nematode abundance reported from impacted stations) following the oil spill. From 2010 to 2022, abundance declined by approximately 80%, demonstrating a consistent decreasing trend, while meiofaunal diversity, as measured by Hill's N1, increased over time. These trends suggest a gradual return toward pre-spill conditions. Furthermore, convergence of variables such as abundance, diversity, and the nematode to copepod ratio across impact levels over time provides preliminary evidence of recovery. Meiofaunal community composition showed distinct differences between stations impacted by oil and those without impact in 2010, 2011, and 2014, but showed no such variation in 2022. Principal Component Analysis (PCA) showed that oil spill impact and meiofaunal community structure were no longer directly related, suggesting that the spill is no longer the primary driver of community composition. These notable changes in meiofaunal abundance, diversity, community composition may indicate preliminary signs of recovery from the DWH oil spill.