Dynamics ofHeterocapsasp. and the associated attached and free-living bacteria under the influence of dispersed and undispersed crude oil

Abstract

In the environment, oil spills have the capacity to modify phytoplankton communities, with important consequences on the food web and the carbon cycle. We are just beginning to understand the oil resistance of phytoplankton species, making it difficult to predict community response. In this study we highlighted the strong resistance of Heterocapsa sp. to oil, which could be associated with its resilient attached bacteria and oil degradation by the free-living bacteria. This finding suggests new directions to explore in the understanding of oil impacts and interactions between eukaryotic and prokaryotic microbes.

The Phytoplankton Taxon-Dependent Oil Response and Its Microbiome: Correlation but Not Causation

“…These observations are in accordance with previous studies showing a higher oil sensitivity of small centric diatoms compared to flagellates or pennate diatoms (Echeveste et al, 2010; Fiori et al, 2016). None of the phytoplankton were impacted by crude oil alone, which agrees with previous studies showing that phytoplankton are more sensitive to dispersed oil than to crude oil alone (Hsiao et al, 1978; Jung et al, 2012; Severin et al, 2016), because dispersant promotes greater release of water-soluble hydrocarbon compounds (Fiocco and Lewis, 1999). Dispersed oil also resulted in a significant increase in PSII cross-section in xenic Skeletonema sp.…”

“…The similar phytoplankton oil response in the presence and absence of the phycosphere was not expected. The strong phytoplankton-bacteria interactions highlighted in numerous studies (Cole, 1982; Amin et al, 2012; Durham et al, 2017), and the detection of oil-degrading bacteria in phytoplankton phycospheres (Severin et al, 2016; Thompson et al, 2017) suggests that dispersed and undispersed oil would be more deleterious to axenic phytoplankton. Here, growth rate and photosynthetic efficiency of axenic cultures of P. sociale and Skeletonema sp.…”

“…Most studies noted a decline in diatom biomass and an increase in phytoflagellates after exposure to oil in both environmental (Fiori et al, 2016) and laboratory settings (Harrison et al, 1986; Mishamandani et al, 2015), but some observed the opposite (González et al, 2009; Gilde and Pinckney, 2012; Parsons et al, 2015). These equivocal results highlight that the taxon-specific phytoplankton oil response is complex and depends on several factors: oil type and concentration (Dunstan et al, 1975; Huang et al, 2011; Ozhan et al, 2014a), nutrient concentrations (Ozhan and Bargu, 2014), initial phytoplankton community structure (Prouse et al, 1976), zooplankton oil tolerance (González et al, 2009), and phytoplankton-associated bacteria (Mishamandani et al, 2015; Severin et al, 2016; Thompson et al, 2017).…”

“…In turn, phytoplankton release strain-dependent organic compounds (Becker et al, 2014) utilized by specific bacteria, leading to host-specific bacterial community structures (Bagatini et al, 2014). Recent studies have shown the presence of oil-degrading bacteria in some phycospheres (Mishamandani et al, 2015; Severin et al, 2016; Thompson et al, 2017) that can enhance hydrocarbon degradation (Abed, 2010).…”

Role of Polysaccharides in Diatom Thalassiosira pseudonana and its Associated Bacteria in Hydrocarbon Presence

“…Green et al (2015) isolated members of Alcanivorax from coccolithophores, and Alcanivorax was an important component of free-living and attached bacterial communities when Heterocapsa sp. was exposed to oil (Severin et al, 2016). Diatoms have previously shown to secrete C8 and C11 hydrocarbons as pheromones (Amin et al, 2012), which might explain the presence of Alcanivorax members in both the Control and Con-trol1DCB treatments.…”