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Grad students and post-docs from the Quigg lab collect plankton samples from the docks near Texas A&M University at Galveston.

ADDOMEx recently had its second experimentation meeting on the campus of Texas A&M University at Galveston. This time experiments were conducted on a larger scale with twelve mesocosms. On the morning of the experiment, volunteers from the Quigg lab at A&M gathered at the docks to conduct lots of plankton tows to collect representative communities of the plankton in the Gulf.

Mesocosms

We’ve got more replicates this time! Here you see the control, dilute oil and Corexit mixture, and the full strength oil and Corexit mixture… all in triplicate.

Like the previous experiments that were conducted in August, mesocosms were filled with seawater, inoculated with plankton from the tows, and treated with oil and oil plus dispersant. Each treatment was done in triplicate in order to allow for statistical analysis of results that were recorded over the course of four days. Researchers collected daily samples to measure aggregate size, changes in the composition of the oil and dispersants over time, changes in community structure, and much more.

In addition to the mesocosm experiments, ADDOMEx also conducted a test drive on a different method of creating aggregates: the roller table. This method has been used for quite some time by Dr. Uta Passow, one of the principal investigators of ADDOMEX and another Gulf of Mexico Research Initiative consortium, ECOGIG. A roller table functions by slowly spinning circular tanks that have been completely filled with water.

Roller_Tables (2)

Roller tanks with treatments

The speed of the rolling tank (and the lack of air bubbles inside) is such that solid body rotation is established and the aggregates in the tank are moved up with the body of water while they sink, thus keeping them from falling out of suspension. Solid body rotation is an effective way to mimic a quiet water environment like that seen in the deep ocean through which aggregates travel as they sink to the ocean floor. Aggregates such as those pictured to the right are important for bringing nutrients from the surface of the ocean to its depths, and can also collect oil droplets from a spill as they sink. ADDOMEx will be using a rolling table like the one above to form aggregates and study how they grow over time in a variety of oil and dispersant treatments.

Check out our Facebook page for time lapse videos of the sampling and science fun!