Responses of sympatric Karenia brevis, Prorocentrum minimum, and Heterosigma akashiwo to the exposure of crude oil

Abstract

Impacts of the Deepwater Horizon oil spill on phytoplankton, particularly, the tolerability and changes to the toxin profiles of harmful toxic algal species remain unknown. The degree to which oil-affected sympatric Karenia brevis, Prorocentrum minimum, and Heterosigma akashiwo, all of which are ecologically important species in the Gulf of Mexico, was investigated. Comparison of their tolerability to that of non-toxic species showed that the toxin-production potential of harmful species does not provide a selective advantage. Investigated toxin profiles for K. brevis and P. minimum demonstrated an increase in toxin productivity at the lowest crude oil concentration (0.66 mg L(-1)) tested in this study. Higher crude oil concentrations led to significant growth inhibition and a decrease in toxin production. Findings from this study could assist in the assessment of shellfish bed closures due to high risk of increased toxin potential of these phytoplankton species, especially during times of stressed conditions.

Enhanced crude oil biodegradative potential of natural phytoplankton‐associated hydrocarbonoclastic bacteria

“…However, the extent to which phytoplankton are impacted by crude oil can largely depend on the toxicological potency and concentration of the oil (Dunstan et al ., ; Vargo et al ., ; Bate and Crafford, ; Huang et al ., ). Different phytoplankton species can have varying tolerances to oil (Ozhan and Bargu, ), and some may even be stimulated by it (Prouse et al ., ; Jung et al ., ; Parsons et al ., ). The most toxigenic hydrocarbons in crude oils are those comprising the aromatic fraction – i.e., mono‐aromatics and PAHs – which are recognized as high‐priority pollutants to the environment (Agency for Toxic Substances and Disease Registry, ; Boehm and Page, ).…”

“…In general, field and laboratory studies have shown that crude oil concentrations up to 1.0 mg/l can stimulate phytoplankton growth – a phenomenon that may have an origin in ocean systems distinguished by the occurrence of natural hydrocarbon seeps on the sea floor where elevated surface chlorophyll concentrations have been reported (D'souza et al ., ). Higher crude oil concentrations, however, can cause anywhere from slight, severe to complete growth inhibition of phytoplankton (Nomura et al ., ; Adekunle et al ., ; Gilde and Pinckney, ; González et al ., ; Paul et al ., ; Ozhan and Bargu, ; Ozhan et al ., ). The consequences of crude oil pollution at sea to phytoplankton must also take into account the associated bacterial community.…”

“…Quite often, however, attention has focused to study one or the other of these organisms. To take the Deepwater Horizon (DWH) oil spill as a recent example, the various reports that had investigated the effects of the Macondo oil to phytoplankton populations in the Gulf of Mexico during the spill did not focus on the associated bacterial community (Ozhan and Bargu, ; Ozhan et al ., ; Parsons et al ., ), whereas the bacterial response had been independently investigated in other studies (e.g., Bælum et al ., ; Hazen et al ., ; Gutierrez et al ., ; Yang et al ., ). These and a plethora of other studies that have used seawater sampling programs to study microbial population diversity and dynamics do not often use operational fractionation to tease apart the various microbial populations (based on size) that constitute the water sample, hence leading to the misconception that HCB identified in any given water column sample may have existed in a free‐living state.…”

Oil pipelines and food sovereignty: threat to health equity for Indigenous communities

“…Observational studies also suggest that levels of potentially harmful algae can increase from oil spills, as reported with reference to the presence of Itxoc I in the Gulf of Mexico in 1979 [56], the Deepwater Horizon oil spill in Offshore Florida, Gulf of Mexico in 2010 [57] and by the Bohai Sea spill in China in 2011) [58]. The effects vary based on oil concentrations [59,60], use of dispersants [61], nutrientlimited circumstances [62], and types of oil [63,64]. Ozhan and Bargu [59] showed increased levels of okadaic acid with increased levels of crude oil, which can further contaminate shellfish and threaten the health of shellfish consumers.…”

Effects of Macondo Oil on Phytoplankton from Grand Isle, Louisiana

“…Several previous studies have examined the effects on individual phytoplankton species of crude oil [11][12][13][14][15][16][17], various components of crude oil [18][19][20][21][22][23], and refined oil products [23][24][25][26][27]. The general implication of these studies has been that low concentrations of crude oil or components thereof stimulate photosynthesis by some species [13,19,23] but have no positive effect on other species.…”