Ecosystem services are lost when facilitation between two ecosystem engineers is compromised by oil

Abstract

Nearshore marine ecosystems are among the most productive areas in the world. Unfortunately, these areas also receive pollutants released into oceanic and riverine waters. Six years following the Deepwater Horizon oil spill, the largest in US history, the complexity of ecological injuries in this system is just now being elucidated. Here, we describe a novel pathway of injury from oil spills by documenting how the loss of oysters near marsh edge as a direct result of shoreline oiling and clean-up activities can double rates of coastal erosion. As part of the natural resource damage assessment, we examined the impact of shoreline oiling on eastern oysters Crassostrea virginica near the marsh edge at 187 sites in Louisiana and Mississippi Sound in 2013. For marshes that experienced heavy oiling, oyster habitat was 77% less abundant than in areas where no oil was observed. Areas near marshes characterized by more moderate levels of oiling had 33% less oyster habitat than areas where no oil was observed. Similarly, the number of sites without any oyster habitat was higher in heavily and persistently oiled areas compared to areas where no oil was observed (56 vs. 24%). The consequences of this loss are substantial and include loss of essential fish habitat, reduced nutrient cycling, and decreased erosion buffering. For a subset of the sites where erosion rate was also measured between 2010 and 2013 (n = 79), shoreline loss was more than twice as high (2.1 vs. 0.9 m yr −1 ) in areas lacking oyster cover. Our findings provide evidence that loss of nearshore oyster habitat can disrupt the strong facilitation between oysters and marsh vegetation.

A Synthesis of Deepwater Horizon Impacts on Coastal and Nearshore Living Marine Resources

“…Some impacts, however, were severe and obvious. For sedentary species including Eastern Oyster the combination of the toxicity of oil and the effects of freshening the marshes not only resulted in mass oyster mortalities (Powers et al, 2017a), but oiling of the marshes was also was associated with collapse of the marsh edges and the loss of oyster bars, which in turn resulted in increased soil erosion and other negative consequences for marsh ecosystems (Grabowski et al, 2012;Powers et al, 2017c;Hughes et al, 2018). Likewise, Bottlenose Dolphins' exposure to toxic oil concentrations presented a variety of negative health effects including reduced reproduction and associated morbidities and mortalities (Schwacke et al, 2014(Schwacke et al, , 2017.…”

“…Relative positions of different years are determined by Bray-Curtis similarities between all possible pairings of years, with 2D stress reflecting the extent of distortion (low distortion, in this case) created by representing these Bray-Curtis similarities in a two-dimensional Euclidean space. cover declined >99% at oiled sites as opposed to unoiled ones (Grabowski et al, 2017;Powers et al, 2017c), an effect that persisted for several years after the DWH event.…”

Short-term low salinity mitigates effects of oil and dispersant on juvenile eastern oysters: A laboratory experiment with implications for oil spill response activities

“…In contrast, Alabama filled a breach along a barrier island, elevating salinity in Mississippi Sound [ 7 – 8 ]. Mechanical methods were also used to remove visible oil from estuarine habitats [ 9 ]. Therefore, nearshore ecosystems were likely subjected to multiple stressors including oil, dispersants, and atypical salinity regimes during the response period.…”

Response of nearshore ecosystems to the Deepwater Horizon oil spill

“…Several papers in this Theme Section highlight the complexity of effects that occur when habitat-forming species are injured by oiling or associated response activities. For example, Powers et al (2017a) demonstrated how the loss of fringing oyster reef as a result of the oil spill can accelerate coastal erosion of marsh habitat. Changes in the quantity and quality of essential habitats will directly affect many ecosystem services (e.g.…”

“…Studies published in this Theme Section and elsewhere expand upon the paradigms already established based on the Exxon Valdez oil spill on nearshore communities and show that: (1) organismal effects of heavy oiling occur across the full range of trophic levels; (2) oiling of foundational species or 'ecosystem engineers' can result in complex and long-term direct and indirect negative effects on nearshore ecosystems (Peterson et al 2003); (3) ecological injury to biogenic habitats can result in loss of ecosystem services that cascade and affect other habitats and processes (Powers et al 2017a); and (4) shoreline response activities intended to remove or mitigate the effects of oil are also associated with negative impacts on habitat-forming species (Driskell et al 2001, Martínez et al 2012, Peterson et al 2012, Grabowski et al 2017, Michel et al 2017, this Theme Section, Powers et al 2017a.…”