Deepwater Horizon Oil Spill Impacts on Salt Marsh Fiddler Crabs (Uca spp.)

Abstract

The Deepwater Horizon oil spill was the largest marine oil spill in US waters to date and one of the largest worldwide. Impacts of this spill on salt marsh vegetation have been well documented, although impacts on marsh macroinvertebrates have received less attention. To examine impacts of the oil spill on an important marsh invertebrate and ecosystem engineer, we conducted a meta-analysis on fiddler crabs (Uca spp.) using published sources and newly available Natural Resources Damage Assessment (NRDA) and Gulf of Mexico Research Initiative (GoMRI) data. Fiddler crabs influence marsh ecosystem structure and function through their burrowing and feeding activities and are key prey for a number of marsh and estuarine predators. We tested the hypothesis that the spill affected fiddler crab burrow density (crab abundance), burrow diameter (crab size), and crab species composition. Averaged across multiple studies, sites, and years, our synthesis revealed a negative effect of oiling on all three metrics. Burrow densities were reduced by 39 % in oiled sites, with impacts and incomplete recovery observed over 2010-2014. Burrow diameters were reduced from 2010 to 2011, but appeared to have recovered by 2012. Fiddler crab species composition was altered through at least 2013 and only returned to reference conditions where marsh vegetation recovered, via restoration planting in one case. Given the spatial and temporal extent of data analyzed, this synthesis provides compelling evidence that the Deepwater Horizon spill suppressed populations of fiddler crabs in oiled marshes, likely affecting other ecosystem attributes, including marsh productivity, marsh soil characteristics, and associated predators.

Five years of Deepwater Horizon oil spill effects on marsh periwinkles Littoraria irrorata

“…We also analyzed the untransformed data using a nonparametric Mann-Whitney U-test (MWU test). Second, we estimated the overall effect of the oil spill using natural log (ln; hereafter, simply 'log') response ratios, using the natural log of the ratio of mean periwinkle density at oiled sites to mean periwinkle density at reference sites for each study-zone-by-year combination (ln[mean density oiled/mean density reference]) (after Hedges et al 1999, Zengel et al 2016b. The log response ratio is zero if oiled and reference sites are identical, and negative if periwinkle den sities are lower at oiled sites.…”

“…The impacts of this oil spill on salt marsh vegetation have been well documented (Lin & Mendels -sohn 2012, Silliman et al 2012, 2016a, Lin et al 2016, Hester et al 2016. In comparison, the impacts of this spill on salt marsh macroinvertebrates have received less attention (although see Zengel et al 2016a, a single-year Natural Resources Damage Assessment [NRDA] study on marsh periwinkles; and Zengel et al 2016b on fiddler crabs [Uca spp.]). As a further step in understanding the effects of this oil spill on salt marsh macroinvertebrates, we assessed multi-year effects of the Deepwater Horizon oil spill on marsh periwinkles Littoraria irrorata, the dominant gastropod (snail) species in salt marshes in the Gulf region, and an important secondary consumer and prey species.…”

Crude oil toxicity to fiddler crabs (Uca longisignalis and Uca panacea) from the northern Gulf of Mexico: Impacts on bioturbation, oxidative stress, and histology of the hepatopancreas

“…However, these activities have had ecological consequences. Incidents such as the Deepwater Horizon oil spill in 2010 have severely disrupted Gulf of Mexico ecosystems as a consequence of impacts on vegetation (Hester et al ; Lin et al ), invertebrates (McCall and Pennings ; Zengel et al , ), and many vertebrate species (Wallace et al ). Such large spills are rare, but smaller‐scale spills are relatively common, and there is also a continuous input from natural oil seeps in the Gulf of Mexico (Kvenvolden and Cooper ).…”

“…The classification of bioturbation mechanisms established by Kristensen et al () places fiddler crabs under the “biodiffusors” and “regenerators.” Their burrowing and feeding activities not only result in short‐distance redistribution of sediment particles near the surface but also redistribute sediment within their burrows to strengthen the burrow walls (Atkinson and Eastman ; Kristensen et al ). The combination of this active bioturbation and a high abundance of crabs, at times at densities of 50 to 100 individuals/m 2 (Mouton and Felder ; Zeil and Hemmi ; Zengel et al ), means that as a group they process large amounts of sediment (Crane ). This bioturbation has many ecological consequences, including increased oxygenation and drainage of sediments, enhanced organic matter decomposition, and increased oxidation of toxic compounds (Bertness ; Gribsholt et al ; Mouton and Felder ).…”

Integrated effects of the Deepwater Horizon oil spill on nearshore ecosystems

“…); reductions in growth (and resulting reduced survival) of shrimp (Farfantepenaeus aztecus, Litopenaeus seti ferus), juvenile southern flounder Paralichthys lethostigma, and red drum Sciaenops ocellatus (Powers & Scyphers 2016); reduced amphipod survival (Powers & Scyphers 2016); reduced hatching success of Gulf killifish Fundulus grandis (Powers & Scyphers 2016); reduced fiddler crab (Uca spp.) abundance (as measured by burrow density, Zengel et al 2016b); and decreased cover of nearshore oysters Crassostrea virginica (Powers et al 2017) (Table 1). Abundance and cover of nearshore oysters did not appear to be affected by the release of river water during response actions (Powers et al 2017).…”