Abstract:

The Deepwater Horizon oil spill spilled 130 million gallons of oil into the Gulf of Mexico. This was followed by an application of 1.4 million gallons of chemical dispersants in an effort to disperse the oil into the water column and promote the biodegradation of oil. Photooxidation of oil is a natural process that causes oxygenation of an oil slick. Although the toxicity of oil on phytoplankton has been extensively studied, the effects of photo-oxidized oil, especially in combination with dispersants is virtually unknown. Phytoplankton vary in their sensitivities to oil and dispersant exposure. Here, we study the effects of photo-oxidized oil in the presence of dispersants on the growth and photo-physiology of oil and dispersant resistant pennate diatom Phaeodactylum tricornutum. We exposed P. tricornutum to two different dilutions of dispersed oil and dispersed photo-oxidized oil and monitored their growth rates and photo-physiological parameters such as photosynthetic efficiency (Fv/Fm), electron transport rates between photosystem II and I (rETRmax), and light harvesting ability (α). Growth rates were unaffected when exposed to dispersed oil and dispersed photo-oxidized oil. Analysis of various photo-physiological parameters revealed no significant differences between any treatments, except for lower rETRmax values in photo-oxidized dispersed oil treatment on the very first day of exposure. Further research are underway to determine the mechanisms behind the resistant nature of P. tricornutum.

Suggested Citation:

Manoj Kamalanathan, Julissa Freund, Jessica Hillhouse, Noah Claflin, Antonietta Quigg. 2019. Impacts of photo-oxidized dispersed oil on Phaeodactylum tricornutum. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/QN937KJ1

Purpose:

To gain a mechanistic understanding behind how oil affects resistant diatoms species Phaeodactylum tricornutum.

Data Parameters and Units:

The dataset consists of several excel files showing measurements of the parameters described below: Alpha: micromol e-.micromol-1 photons ETRmax: micromol.electrons m2.s-1 Cell counts: cells per ml Fv/Fm: relative fluorescence Sigma PSII: Å2 (quanta)-1 ROS: Relative ROS per cell

Methods:

The dispersed oil was prepared by adding 400 μL of oil to 100 ml of filtered seawater from the Gulf of Mexico (obtained from NOAA) in a quartz round bottom flask, which was then incubated out in natural sunlight for 48 hrs – Photo-oxidation. 900 mL of F/2 media was then added to this photo-oxidized oil-water solution and mixed overnight in dark, followed by filtration with 20-micron sieve to obtain photo-oxidized water accommodated fraction (WAF). Dispersed photo-oxidized WAF was prepared using the same method as described above with the addition of 400 μL of oil and 10 μL of dispersant. The eventual dispersed photo-oxidized WAF was then diluted 1:10 with f/2 media to obtain a diluted version of dispersed photo-oxidized WAF. The initial phytoplankton cell count was 100.000 cells per mL and the medium used was f/2 prepared using natural seawater from the Gulf of Mexico using recipe described in National Center for Marine Algae and Microbiota (NCMA) website (https://ncma.bigelow.org/media/wysiwyg/Algal_recipes/NCMA_algal_medium_f_2_1.pdf).

Individual Files: