Diatom aggregation when exposed to crude oil and chemical dispersant: Potential impacts of ocean acidification

• Published in: PloS one 2020-07, Vol.15 (7), p.e0235473
• Main Authors: Genzer, Jennifer L, Kamalanathan, Manoj, Bretherton, Laura, Hillhouse, Jessica, Xu, Chen, Santschi, Peter H, Quigg, Antonietta
• Format: Article
• Language: English
• Subjects: Acidification; Agglomeration; Aggregates; Aquatic Organisms - drug effects; Biology and Life Sciences; Carbohydrates; Carbon; Carbon cycle; Chemical properties; Chemical spills; Chemistry; Climate change; Contaminants; Crude oil; Diatoms; Diatoms - drug effects; Dispersants; Earth Sciences; Ecology and Environmental Sciences; Engineering and Technology; Environmental aspects; Experiments; Exudates; Exudation; Forecasts and trends; Growth; Humans; Inorganic carbon; Marine biology; Marine microorganisms; Marine organisms; Marine pollution; Marine snow; Ocean acidification; Ocean floor; Oceans; Oil spills; Petroleum - toxicity; Petroleum Pollution - adverse effects; Photosynthesis; Physical Sciences; Polycyclic aromatic hydrocarbons; Polycyclic Aromatic Hydrocarbons - adverse effects; Polycyclic Aromatic Hydrocarbons - chemistry; Pyrenes; Seawater; Seawater - chemistry; Snow; Snow formation; Surface-Active Agents - adverse effects; Surface-Active Agents - chemistry; Water Pollutants, Chemical - adverse effects; Water Pollutants, Chemical - chemistry
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0235473

Diatoms play a key role in the marine carbon cycle with their high primary productivity and release of exudates such as extracellular polymeric substances (EPS) and transparent exopolymeric particles (TEP). These exudates contribute to aggregates (marine snow) that rapidly transport organic material to the seafloor, potentially capturing contaminants like petroleum components. Ocean acidification (OA) impacts marine organisms, especially those that utilize inorganic carbon for photosynthesis and EPS production. Here we investigated the response of the diatom Thalassiosira pseudonana grown to present day and future ocean conditions in the presence of a water accommodated fraction (WAF and OAWAF) of oil and a diluted chemically enhanced WAF (DCEWAF and OADCEWAF). T. pseudonana responded to WAF/DCEWAF but not OA and no multiplicative effect of the two factors (i.e., OA and oil/dispersant) was observed. T. pseudonana released more colloidal EPS (< 0.7 μm to > 3 kDa) in the presence of WAF/DCEWAF/OAWAF/OADCEWAF than in the corresponding Controls. Colloidal EPS and particulate EPS in the oil/dispersant treatments have higher protein-to-carbohydrate ratios than those in the control treatments, and thus are likely stickier and have a greater potential to form aggregates of marine oil snow. More TEP was produced in response to WAF than in Controls; OA did not influence its production. Polyaromatic hydrocarbon (PAH) concentrations and distributions were significantly impacted by the presence of dispersants but not OA. PAHs especially Phenanthrenes, Anthracenes, Chrysenes, Fluorenes, Fluoranthenes, Pyrenes, Dibenzothiophenes and 1-Methylphenanthrene show major variations in the aggregate and surrounding seawater fraction of oil and oil plus dispersant treatments. Studies like this add to the current knowledge of the combined effects of aggregation, marine snow formation, and the potential impacts of oil spills under ocean acidification scenarios.