Abstract:

Phytoplankton community composition can change in response to environmental variables, which in turn has effects on marine food webs and biogeochemical cycles. A mesocosm experiment was carried out to assess the effects of crude oil and dispersants on phytoplankton assemblages from the Gulf of Mexico. Photographs were taken in order to characterize how the microbial community changed after 72h of exposure.

Suggested Citation:

Laura Bretherton, Breanna Couffer, Antonietta Quigg. 2017. Photographs of marine phytoplankton exposed to crude oil and dispersants in mesocosm tanks after 72h. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N7DJ5CP2

Purpose:

These photographs were taken in order to assess the effects of oil and chemical dispersant exposure on community dynamics in phytoplankton found in the Gulf of Mexico.

Data Parameters and Units:

Control=control tanks; WAF=water accommodated fraction of oil; CEWAF=chemically enhanced water accommodated fraction of oil; DCEWAF=dilute chemically enhanced water accommodated fraction of oil; A, B, C=replicate tanks; scale bars represent 50 microns

Methods:

Natural seawater was collected from a coastal buoy in the Gulf of Mexico and brought back to Texas A&M University at Galveston for manipulation. Treatments were prepared in specialized glass tanks called WAF makers using the natural seawater. WAF treatments were prepared by adding Macondo crude oil to a target concentration of 1mg L-1, and CEWAF treatments were made with a stock solution containing a 20:1 ratio of oil:Corexit. One third of the CEWAF was then diluted until the crude oil concentration was consistent with the WAF to make the DCEWAF treatments. Control treatments were not exposed to either oil or Corexit. The experiments were then set up in 100L glass tanks staged in a room fitted with fluorescent bulbs. All treatments were grown in triplicate with true biological replication. A 100mL sample was taken from each tank after 72h and settled for 24h in an Utermohl chamber (Combined Plate Chamber, Hydro-Bios, Germany) fitted with a 100mL cylinder. The plate was then removed to look at the sample under an inverted light microscope (Motic AE31, BC, Canada). All phytoplankton observed on the plate were identified to genus level using Tomas (1997). Phytoplankton identification data can be found in GRIIDC dataset R4.x263.000:0015. Representative photographs were taken using the attached camera and processed using Leica Application Suite (LAS) EZ v1.6.0. To calibrate the measurements recorded by LAS EZ software, a photograph of a micrometer was taken with the microscope’s camera and a known distance of 200µm was measured to determine the number of pixels (px) within that set distance. The resulting ratio (1px = 0.32µm) was used to calibrate measurements taken with the microscope and camera.

Instruments:

Utermohl chamber - Combined Plate Chamber, Hydro-Bios, Germany inverted light microscope - AE31, Motic, BC, Canada Camera - Leica EC3, Leica Microsystems, IL, USA

Individual Files: