Shoreline oiling effects and recovery of salt marsh macroinvertebrates from the Deepwater Horizon Oil Spill.

Donald R. Deis,Qianxin Lin,Irving A. Mendelssohn,John W. Fleeger,Aixin Hou,Stefan M. Bourgoin

doi:10.7717/peerj.3680

Abstract

Salt marshes in northern Barataria Bay, Louisiana, USA were oiled, sometimes heavily, in the aftermath of the Deepwater Horizon oil spill. Previous studies indicate that fiddler crabs (in the genus Uca) and the salt marsh periwinkle (Littoraria irrorata) were negatively impacted in the short term by the spill. Here, we detail longer-term effects and recovery from moderate and heavy oiling over a 3-year span, beginning 30 months after the spill. Although neither fiddler crab burrow density nor diameter differed between oiled and reference sites when combined across all sampling events, these traits differed among some individual sampling periods consistent with a pattern of lingering oiling impacts. Periwinkle density, however, increased in all oiling categories and shell-length groups during our sampling period, and periwinkle densities were consistently highest at moderately oiled sites where Spartina alterniflora aboveground biomass was highest. Periwinkle shell length linearly increased from a mean of 16.5 to 19.2 mm over the study period at reference sites. In contrast, shell lengths at moderately oiled and heavily oiled sites increased through month 48 after the spill, but then decreased. This decrease was associated with a decline in the relative abundance of large adults (shell length 21–26 mm) at oiled sites which was likely caused by chronic hydrocarbon toxicity or oil-induced effects on habitat quality or food resources. Overall, the recovery of S. alterniflora facilitated the recovery of fiddler crabs and periwinkles. However, our long-term record not only indicates that variation in periwinkle mean shell length and length-frequency distributions are sensitive indicators of the health and recovery of the marsh, but agrees with synoptic studies of vegetation and infaunal communities that full recovery of heavily oiled sites will take longer than 66 months.

Highlights

The release of over three million barrels of oil from the Deepwater Horizon (DWH ) oil spill (U.S District Court, 2015) in April, 2010, exposed the Mississippi River delta complex, the nation’s largest and most productive wetland-estuarine environment, to an unprecedentedHow to cite this article Deis et al (2017), Shoreline oiling effects and recovery of salt marsh macroinvertebrates from the Deepwater Horizon Oil Spill
95% of the oiled wetlands occurred in Louisiana, and the heaviest oiling was most widespread in northern Barataria Bay where salt marshes are dominated by Spartina alterniflora and, to a lesser extent, Juncus roemerianus (Michel et al, 2013; Zengel et al, 2014)
Our research focused on two conspicuous marsh macroinvertebrates, Uca spp., fiddler crabs, and Littoraria irrorata, salt marsh periwinkle

Summary

Introduction

How to cite this article Deis et al (2017), Shoreline oiling effects and recovery of salt marsh macroinvertebrates from the Deepwater Horizon Oil Spill. 95% of the oiled wetlands occurred in Louisiana, and the heaviest oiling was most widespread in northern Barataria Bay where salt marshes are dominated by Spartina alterniflora and, to a lesser extent, Juncus roemerianus (Michel et al, 2013; Zengel et al, 2014). The plant community in northern Barataria Bay experienced strong responses to oiling, including heavy mortality that frequently denuded shorelines (Lin & Mendelssohn, 2012; Silliman et al, 2012; Zengel & Michel, 2013; Zengel et al, 2014; Zengel et al, 2015)

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Results

Conclusion