Abstract
Large-scale anthropogenic disturbances can have direct and indirect effects on marine communities, with direct effects often taking the form of widespread injury or mortality and indirect effects manifesting as changes in food web structure. Here, we report a time series that captures both direct and indirect effects of the Deepwater Horizon Oil Spill (DWH) on northern Gulf of Mexico (nGoM) reef fish communities. We observed significant changes in community structure immediately following the DWH, with a 38% decline in species richness and 26% decline in Shannon-Weiner diversity. Initial shifts were driven by widespread declines across a range of trophic guilds, with subsequent recovery unevenly distributed among guilds and taxa. For example, densities of small demersal invertivores, small demersal browsers, generalist carnivores, and piscivores remained persistently low with little indication of recovery seven years after the DWH. Initial declines among these guilds occurred prior to the arrival of the now-widespread, invasive lionfish (Pterois spp.), but their lack of recovery suggests lionfish predation may be affecting recovery. Factors affecting persistently low densities of generalist carnivores and piscivores are not well understood but warrant further study given the myriad ecosystem services provided by nGoM reef fishes.
Highlights
Large-scale anthropogenic disturbances can have direct and indirect effects on marine communities, with direct effects often taking the form of widespread injury or mortality and indirect effects manifesting as changes in food web structure
Much of the effort to document the community-level responses to the Deepwater Horizon Oil Spill (DWH) was focused on monitoring coastal habitats that provide critical nurseries for several marine taxa[41], are widely studied by community ecologists[42], and whose proximity favored the rapid collection of critical baseline data[43]
43% percent of reef fish species were distributed among five other families: Serranidae (15.2%), Carangidae (7.2%), Sciaenidae (5.8%), Sparidae (5.8%), and Pomacentridae (5.1%)
Summary
Large-scale anthropogenic disturbances can have direct and indirect effects on marine communities, with direct effects often taking the form of widespread injury or mortality and indirect effects manifesting as changes in food web structure. Densities of small demersal invertivores, small demersal browsers, generalist carnivores, and piscivores remained persistently low with little indication of recovery seven years after the DWH Initial declines among these guilds occurred prior to the arrival of the now-widespread, invasive lionfish (Pterois spp.), but their lack of recovery suggests lionfish predation may be affecting recovery. Between 4 and 14% of the total discharge was transported to the benthos by contaminated marine snow[21,22,23,24], exposing numerous pelagic and benthic communities to toxic polycyclic aromatic hydrocarbons (PAHs)[25] as well as emulsifying dispersants[26] Both lethal and sublethal effects (e.g., compromised immune[27] and endocrine function[28], developmental abnormalities[29], reduced growth[30], and impaired olfaction[31] and predator avoidance32,33) of oil exposure have been well documented for numerous taxa[34,35,36,37], and negative effects at the organismal level had the clear potential to elicit effects on community structure through bottom-up[38] or top-down mechanisms[39,40]. Compensatory population increases following DWH-induced mortality would likely be slow
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