Particulate accumulations in the vital organs of wild Brevoortia patronus from the northern Gulf of Mexico after the Deepwater Horizon oil spill

Abstract

Histopathologic lesions were observed in the commercially important filter-feeding fish, Brevoortia patronus (Gulf menhaden), along the Louisiana Gulf Coast. Menhaden collected from Louisiana waters in 2011 and 2012, 1 and 2 years following the Deepwater Horizon oil spill, showed varying severities of gill lesions as well as an unusual accumulation of black particulates visible at necropsy in the heart and stomach vasculature. The PAH derived particulates were typically 1-4 µm in diameter, but larger aggregates were observed in the coronary vessels on the ventricle surfaces and their location and size was confirmed by light microscopy. Composited particulate composition was consistent with weathered petrogenic polycyclic aromatic hydrocarbon (PAH) mixtures based on GC-MS analysis. Particulates were present in 63 and 80% of fish hearts and 70 and 89% of stomach muscularis collected in 2011 and 2012, respectively. Tissue embedded particulates can lead to localized cellular damage from bioavailable compounds, as well as chronic effects from occlusion of sensitive tissues' blood flow. The PAH derived particulates appeared to act as emboli in small capillaries, and could associated with localized inflammation, focal necrosis and inappropriate collagen and fibroblast tissue repair. We believe large volume filter feeding teleosts, such as menhaden (up to 3 million gallons per year/fish) with high lipid content, have a higher exposure risk and greater potential for toxicity from toxic particulates than other higher trophic level finfish. Suspended PAH derived particulates following an oil spill therefore, should be considered when assessing long-term ecological impacts and not be limited to physical contact (coating) or water soluble fractions for assessing toxicity (gill and neurologic).

A three year study of metal levels in skin biopsies of whales in the Gulf of Mexico after the Deepwater Horizon oil crisis

“…In the wake of this crisis, most toxicological studies have focused on the effects of PAHs in the oil organics and dispersants. While these aspects are indeed important to understand, few health effects have been linked to PAH levels from this crisis (Carmichael et al, 2012; Fitzgerald and Gohlke, 2014; Schwacke et al, 2014; Lane et al, 2015; Millemann et al, 2015; Sammarco et al, 2015). This outcome may reflect the unique ecosystem of the Gulf of Mexico as one with some resilience to oil, due to the large amounts of oil that naturally seeps from the sea floor.…”

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

“…Similarly, Carroll et al [32] found relatively minor adverse effects on an Arctic cod fishery in simulated oil spills in their spawning grounds. Milliman et al [33] suggested the DWH blowout as a possible source of black particulates on the gills, in the stomachs and in the heart tissue of Gulf menhaden they sampled from oiled Barataria Bay and presumably un-oiled Vermillion Bay from 2010 through 2012, but the supporting evidence they present is inconclusive. The total polycyclic aromatic hydrocarbon (PAH) concentrations in whole-body homogenates [34], and the detection frequencies of black particulates and of most histopathological lesions, were not significantly different between the oiled and un-oiled locations from 2010 through 2012.…”

“…The total polycyclic aromatic hydrocarbon (PAH) concentrations in whole-body homogenates [34], and the detection frequencies of black particulates and of most histopathological lesions, were not significantly different between the oiled and un-oiled locations from 2010 through 2012. Milliman et al [33] suggest that the general absence of statistically significant differences between the oiled and reference locations may have resulted from the intermixing of fish, but extensive tagging conducted during the early 1970s [7] indicates this is unlikely. Instead, local or regional combustion sources seem a more plausible source of the black particulates detected by Milliman et al [33], and if so, the statistically significant interannual variation in total fish PAH concentrations they report may reflect variation in winds and other factors affecting particulate deposition patterns.…”