Because of the importance of plankton to the food web, CONCORDE researchers seek a better understanding of how these tiny marine organisms choose to live in the complex environment of the river-dominated areas of the northern Gulf of Mexico. A clear picture of where they reside at different times of the year will help scientists know better how to protect their habitats should another oil spill occur.

Frank Hernandez, an Assistant Professor in the Department of Coastal Sciences at USM’s Gulf Coast Research Laboratory (GCRL), explains that one way to understand how oil could impact the ecosystem of an area is to go straight to the bottom. In this case, he is referring to various species of microscopic floating animals called zooplankton—“food for baby fish,” according to Hernandez—that make up the base of the marine food web.

“They are often the first responders to an environmental impact,” says Hernandez of zooplankton. “And so they are a good target for looking at impacts to marine productivity cycles.”

Hernandez, along with Monty Graham, Chair of USM’s Department of Marine Sciences and GCRL Interim Director, and Robert Cowen, Director of Oregon State’s Hatfield Marine Science Center, are leading a team to investigate how a marine environment dominated by freshwater flow from nearby rivers, combined with plankton behaviors, determine the number and distribution of plankton in the water column.

The team is looking at smaller scenarios to help them determine the big picture. For example, do the plankton stay in the same place at night as they do during the day? What about periods when the rivers are releasing more freshwater due to heavy rains? Do they behave the same way in shallow water as in deep?

cedric, adam, christian (3)
University of Southern Mississippi Department of Marine Science post doctoral research associate, Adam Greer (left), and Oregon State University post doctoral research associate, Christian Briseno- Avena(right) standing next to the ISIIS prior to a deployment during the fall research campaign. 

Thanks to CONCORDE, the researchers have a new weapon in their arsenal of scientific instruments that will help them get a level of detail not possible in past studies. The In Situ Ichtyoplankton Imaging System (ISIIS) tows behind a research vessel, taking high resolution images at a rate of seven per second. A typical plankton net collects samples with no way of telling how the individual animals were grouped before they were caught. The ISIIS shows scientists exactly where they came from and where each was in relation to the other.

Once the images are collected, image recognition software helps the scientists identify the individual plankton. Hernandez says traditional plankton net tows are also being collected to help “build an image library of who’s who in the water.”

The larger part of the mission is to combine what the plankton team learns about plankton behavior with what other CONCORDE scientists are learning about the physical processes in a river-dominated marine ecosystem to determine what the intrusion of oil or other contaminants would do to the plankton and their world.