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.
Highlights
The Deepwater Horizon oil spill was the largest marine oil spill in US waters to date and one of the largest worldwide: over 3 million barrels of crude oil were released into the Gulf of Mexico (U.S District Court 2015), and over 1700 km of coastal shorelines were oiled (Michel et al 2013)
As part of the Natural Resources Damage Assessment (NRDA) process, we addressed the impact of the Deepwater Horizon oil spill on fiddler crabs (Uca spp.), Estuaries and Coasts (2016) 39:1154–1163 the dominant crab species in salt marshes in the Gulf region and an important ecosystem engineer and prey species
All three metrics indicated that the Deepwater Horizon oil spill negatively affected fiddler crab populations
Summary
The Deepwater Horizon oil spill was the largest marine oil spill in US waters to date and one of the largest worldwide: over 3 million barrels of crude oil were released into the Gulf of Mexico (U.S District Court 2015), and over 1700 km of coastal shorelines were oiled (Michel et al 2013). Previous studies have reported negative effects of prior oil spills on fiddler crabs, including increased mortality, reduced burrow density, impaired locomotion and behavior, abnormal burrow construction, changes in sex ratio, and reduced juvenile settlement (Rützler and Sterrer 1970; Krebs and Burns 1977; Burns and Teal 1979; Teal and Howarth 1984; Burger et al 1991, 1992; Teal et al 1992; Culbertson et al 2007; Melville et al 2009) Many of these studies were associated with a single prior oil spill in New England, USA, affecting a relatively small area of marsh compared to the Deepwater Horizon spill. We tested the hypothesis that the oil spill reduced fiddler crab burrow density (crab abundance), reduced burrow diameter (crab size), and altered fiddler crab species composition in salt marshes that were heavily to moderately oiled
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