Effects of Chemically Enhanced Water-Accommodated Fraction of Iranian Heavy Crude Oil on Periphytic Microbial Communities in Microcosm Experiment

Abstract

Exposure experiments were conducted to determine the effects of an oil spill on a periphytic microbial community with the chemically enhanced water-accommodated fraction (CEWAF) of Iranian Heavy Crude oil in a microcosm containing artificial benthic substrates. Bacteria and heterotrophic nano-flagellates (HNF) grew well in all the treatments, except for the 100% CEWAF exposure. However, periphyton did not adapt to concentrations of CEWAF ≥ 20%. Among the periphyton, Cylindrotheca spp. dominated under treatment conditions, and the response of Cylindrotheca spp. to CEWAF (i.e., particularly 10%) closely followed the changes in chlorophyll a concentration. The concentrations of petroleum hydrocarbons from 10% and 20% CEWAF seemed to have a negative effect on periphyton and a growth-promoting effect on bacteria and HNF, respectively.

Acute Toxicity of Water-Accommodated Fraction and Chemically Enhanced WAF of Bunker C Oil and Dispersant to a Microalga Tetraselmis tetrathele

“…The increase in the toxicity of oil due to the addition of dispersant has been reported in many past studies (Fabregas et al 1984;Koyama and Kakuno 2004;Ramachandran et al 2004;Baek et al 2013;Lee et al 2013;Cohen et al 2014Anderson et al 2014). However, the results of this study showed that CEWAF of bunker C oil and DISP were both highly toxic.…”

“…reported that the addition of Corexit EC9500 increased the total petroleum hydrocarbon concentration (TPH) by 50-fold, which in turn caused 100 % mortality to two medium-sized phytoplankton species, Ditylum brightwelli and Scrippsiella trochoidea. Added to this, exposure of periphyton to chemically dispersed oil led to reduced total abundance, with observations that algae exposed to higher concentrations could not become colonized (Baek et al 2013). The same increased toxicity was noted for zooplankton (Lee et al 2013;Cohen et al 2014), crustaceans (Anderson et al 2014) and fish (Koyama and Kakuno 2004;Ramachandran et al 2004) after exposure to chemically dispersed oil.…”

“…WAF is a laboratory-prepared medium derived from low energy mixing of oil and water, while CEWAF is derived from the standard 20 %-25 % vortex mixing of oil, dispersant and water. The use of this standard protocol merits easier comparison of toxicity results, and has been widely used by researchers (Ramachandran et al 2004;Lee et al 2013;Baek et al 2013). The toxicity test protocol for dispersant used in this study can also be a model in screening chemical dispersants.…”

Synergistic effect of crude oil plus dispersant on bacterial community in a louisiana salt marsh sediment

“…Various eukaryotes were used as model organisms to evaluate the synergistic effect of CEWAF, but study is still necessary to investigate the synergistic effect of CEWAF on microbial community. There are several reports to show the effect of CEWAF on microorganisms (Ortmann et al 2012;Baek, Son and Shim 2013), but they did not examine whether the synergistic effect exists. Considering the crucial role of bacteria in marine food webs (Ortmann et al 2012), it is important to investigate the existence of synergistic effect of dispersed oil on marine bacteria.…”