A method for the production of large volumes of WAF and CEWAF for dosing mesocosms to understand marine oil snow formation

Abstract

Marine oil snow (MOS) formation is a mechanism to transport oil from the ocean surface to sediments. We describe here the use of 110L mesocosms designed to mimic oceanic parameters during an oil spill including the use of chemical dispersants in order to understand the processes controlling MOS formation. These experiments were not designed to be toxicity tests but rather to illustrate mechanisms. This paper focuses on the development of protocols needed to conduct experiments under environmentally relevant conditions to examine marine snow and MOS. The experiments required the production of over 500 liters of water accommodated fraction (WAF), chemically enhanced water accommodated fraction of oil (CEWAF) as well as diluted CEWAF (DCEWAF). A redesigned baffled (170 L) recirculating tank (BRT) system was used. Two mesocosm experiments (M1 and M2) were run for several days each. In both M1 and M2, marine snow and MOS was formed in controls and all treatments respectively. Estimated oil equivalent (EOE) concentrations of CEWAF were in the high range of concentrations reported during spills and field tests, while WAF and DCEWAF concentrations were within the range of concentrations reported during oil spills. EOE decreased rapidly within days in agreement with historic data and experiments.

Role of Polysaccharides in Diatom Thalassiosira pseudonana and its Associated Bacteria in Hydrocarbon Presence

“…The exact nature and extent of this damage remains unknown and the critical nature of this response deserves further study. The recovery of growth after 4 d may be due to the development of more favorable growth conditions, with the disappearance of certain toxic components of oil due to natural volatilization and/or biodegradation (Wade et al, 2017), but the mechanism remains unknown and this warrants further investigation.…”

“…EOE values were analyzed according to Wade et al (2017). Briefly, 5-to 10-mL samples were extracted with dichloromethane and the fluorescence of the extracted fraction was then measured at 260/358 nm excitation/emission using a spectrofluorometer (model no.…”

Mesocosm experiments to better understand hydrocarbon half-lives for oil and oil dispersant mixtures

“…Oil from the Marlin platform nearby to the Macondo well, is similar to MC252 having a specific gravity of 0.86, and similar chemical composition (e.g. n-alkane and polycyclic aromatic hydrocarbon distribution) and aquatic toxicity [24,25,7]. A detailed comparison between the Macondo source oil and Marlin Platform oil is found in Worton et al [24].…”

“…The Chemical Response to Oil Spills: Ecological Effects Research Forum (CROSERF) method for the generation of relatively small volumes (up to a few liters) of a water-accommodated fraction (WAF) of oil [26] has been used for many studies. The larger volume needed for the studies described here required the development of baffled recirculation tanks (BRT) to prepare these bigger volumes (100's of L) for these mesocosm studies [27,7]. These BRTs were used to prepare WAF, a chemically enhanced water accommodated fraction (CEWAF) of oil and a diluted (10-fold) CEWAF (DCEWAF).…”

“…These BRTs were used to prepare WAF, a chemically enhanced water accommodated fraction (CEWAF) of oil and a diluted (10-fold) CEWAF (DCEWAF). Flow was generated by a PTFE-diaphragm pump that re-circulated the seawater at 350 ml min -1 [7]. Additionally, an electric stirrer was used at rates no higher than 200 rpm to avoid creating a vortex using low energy mixing [26].…”