Three dimensional micrographs of microbe-oil microaggregates from the TeCOAST and COAST mesocosms

Two mesocosm experiments were carried out in August (TeCOAST) and October of 2015 (COAST) using coastal water collected near Galveston Bay, Texas. Four mesocosm treatments were prepared for this study: (1) Control (seawater only); (2) WAF (oil + seawater); (3) Chemically-enhanced WAF (CE-WAF; oil + Corexit + seawater); (4) Diluted CE-WAF (1:10 dilution). Initial mesocosm volumes were 79L. Prior to experiment initiation, phytoplankton were collected from coastal Galveston, TX waters and added to each tank to stimulate interactions between phytoplankton, oil, and Corexit. Starting at time-point zero and every 12 hours thereafter, water samples were collected from each mesocosm in clean, opaque, Nalgene bottles. Water samples were fixed with formalin (2% v/v final concentration), stained with DAPI (45μM final concentration), and visualized on a Zeiss Axio Imager 2 microscope. DAPI-stained cells appear blue while autofluorescent oil/Corexit appears orange. Images are constructed from a z-stack of 51 micrographs, deconvoluted using Apotome structured illumination.