Seawater carbonate chemistry and diatom aggregation when exposed to crude oil and chemical dispersant

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.