Evidence for Ecosystem-Level Trophic Cascade Effects Involving Gulf Menhaden (Brevoortia patronus) Triggered by the Deepwater Horizon Blowout

Unprecedented recruitment of Gulf menhaden (Brevoortia patronus) followed the 2010 Deepwater Horizon blowout (DWH). The foregone consumption menhaden, after their many predator species were killed by oiling, increased competition among for food, resulting in poor physiological conditions and low lipid content during 2011 2012. Menhaden sampled length weight measurements, beginning 2011, exhibited poorest condition around Barataria Bay, west Mississippi River, where year class was highest. Trophodynamic comparisons indicate that ~20% net primary production flowed through prior to DWH, increasing ~38% ~27% 2012, confirming dominant role food web. Hyperabundant likely suppressed populations zooplankton prey, suggesting a trophic cascade triggered recruitment. Additionally, low-lipid became “junk food” predators, further propagating adverse effects. We posit web analyses based on inappropriate spatial scales species, or solely biomass, provide insufficient indication ecosystem consequences oiling injury. Including such cascading associated indirect effects damage assessment models will enhance ability anticipate estimate from, recovery guidance for, major oil spills.