Potential impacts of ocean acidification on diatom aggregation when exposed to crude oil and chemical dispersants

Ocean acidification (OA) and its effects on seawater carbonate chemistry affect all marine organisms, especially those that utilize inorganic carbon for photosynthesis. The effects of oil compounds on phytoplankton in future OA conditions has not been well studied. Roller table experiments with Thalassiosira pseudonana, a small centric diatom, were conducted to produce marine snow aggregates in six treatments: Control (pCO2 = 400 ppm), OA (pCO2 = 750 ppm), water accommodated fraction of oil (WAF), OAWAF, diluted chemically enhanced WAF (DCEWAF), and OADCEWAF. Measurements included intracellular photophysiological responses, oil concentrations and polycyclic aromatic hydrocarbons (PAHs), aggregate morphology, transparent exopolymeric particles (TEP), and extracellular polymeric substances (EPS) to investigate if OA will affect the response to oil spill conditions. The experiments were conducted in the dark to eliminate cell replication and photosynthesis and used both stationary and exponential growth phases.