Impact of dispersant on early life stages of the water flea Daphnia magna and the eastern oyster Crassostrea virginica

Abstract

In response to the 2010 Deepwater Horizon oil spill, over 1 million gallons of dispersant were applied in Gulf of Mexico offshore waters; Corexit 9500 was the most applied dispersant. The impact on organisms in nearshore and freshwaters has received little scrutiny. Acute 48 h toxicity of Corexit 9500 and a new hyperbranched polyethylenimine (HPEI) dispersant-like compound were evaluated for the freshwater indicator organism, Daphnia magna and for larval and early spat stages of the Eastern oyster, Crassostrea virginica. For D. magna, Corexit 9500 demonstrated toxicity (EC of 0.14 [0.13, 0.15] ppm) similar to the 10-kDa HPEI (EC of 0.16 [0.12, 0.19] ppm). HPEI toxicity increased as a function of molecular weight (1.2 to 750 kDa). The 10 kDa size HPEI was further investigated because it dispersed crude oil with equal effectiveness as Corexit. For Corexit, 100% oyster mortality was detected for the ≤0.2-mm size classes and mortality >50% for the 0.3- and 0.7-mm size classes at the two greatest concentrations (25 and 50 ppm). HPEI (10 kDa) exhibited low mortality rates (<30%) for all concentrations for all oyster size classes except the 0.1-mm class. Although mortality rates for this size class were up to 60%, mortality was still less than the mortality caused by Corexit 9500. The low toxicity of HPEI polymers for C. virginica in comparison with Corexit 9500 suggests that HPEI polymers warrant further study.

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

“…Oysters in low salinity water, however, had less than 10% mortality in oiled treatments and less than 50% mortality in oil+dispersant treatments ( Fig 5A ). Typically, toxicity is tested by measuring early larval growth, survival, and morphological abnormalities in marine organisms as early life stages are generally more sensitive than adult stages ([e.g., [ 24 – 26 ]). In this study, we document mortality of juvenile oysters, which have already surpassed the larval and settlement stages, indicating that later life stages are also susceptible to adverse effects in a closed system.…”

“…The use of dispersants can reduce toxicity concentrations below thresholds for many marine species [ 34 – 35 ] though, and make oil slicks more accessible to hydrocarbon-degrading bacteria [ 36 ]. Nonetheless, various dispersants have been shown to negatively affect eastern oyster gametes and larvae [ 26 – 28 ] both alone, and when added to oil. By mixing oil into the water via the use of dispersant in our experiment, the oysters could readily uptake both oil and dispersant, potentially causing the observed mortality (although oyster tissue analysis was not conducted so we cannot confirm significant uptake of hydrocarbon contaminants).…”

Chitosan/PEO nanofibers electrospun on metallized track-etched membranes: fabrication and characterization

“…Hyperbranched polymeric poly-amidoamine nanomaterials (Helux-3316) toxicity to D. magna was reported to be 16.8 ± 1 mg/L and 4.69 mg/L for 24 h and 48 h EC50 values respectively [66] and was considered toxic because of the primary amines present in the chemical structure. The immobilization of D. magna on hyperbranched poly(ethyleneimine) was estimated to have 48 h EC50 values of 0.16 mg/L [67] but the toxicity of the 10 kDa polymer increased with an increase in molecular weight.…”