June 2, 2006 – Spotlight On: Marj Brooks, Filter Feeder Options

[Patricia_Janes]

June 2, 2006 – Aboard the Healy
Longitude: 177 26.261 W, Latitude: 61 26.606 N

Marj Brooks has been my roommate onboard the Healy for the past 30 days, but I hardly ever see her. That’s because she works the midnight to noon shift. So while I am asleep, she is downstairs in the science lab analyzing water samples.

But I finally had a chance to catch up with Marj and learn more about her and her studies. Marj is an assistant research professor at the University of Wyoming. She is also a postdoctoral associate at the National Center for Ecological Analysis and Synthesis at the University of California, Santa Barbara. The big questions Marj is trying to answer while on the Healy are: How does selenium, a naturally occurring element, enter and spread through the food web? And what is the role of bacteria in the northern Bering Sea’s food web?


Early on in the expedition, Marj and Beth Cassie went on a quest to gather ice that had algae clinging to it. Ice algae acts as the starter culture for the spring algal bloom. That algae is the base of the entire food web.


Marj and I sat down in the science lab to chat about her research. I quizzed her endlessly about her work, and she kindly answered all of my questions in great detail.

Marj is interested in selenium because marine life—from seabirds and marine mammals to fungi and invertebrates—can safely accumulate high levels of the element, whereas it can cause birth defects in land animals. Take the eider, a marine duck: Eiders can have extremely high levels of selenium and the eggs that they lay will be just fine. But if a land duck that lives in freshwater lakes and streams—and cannot tolerate living in seawater—accumulates similarly high levels of selenium, it will lay deformed eggs.

Marj’s lab work begins with the CTD. The CTD is a large device that contains sensors that measure the temperature, conductivity (a measure of how much salt is in the water), and depth of seawater. Members of the Coast Guard lower the CTD into the water and then lift it back up. As they raise it, 12 empty canisters, called Niskin bottles, collect water from the bottom, middle, and top layers of the water column. Marj takes a portion of this water while other scientists gather the rest. Then, she runs her share of the water through a filtering system.


A Coast Guard MST (Marine Science Technician) is in charge of lowering and raising the CTD using a winch and pulley system. When empty, the CTD weighs roughly 1,200 pounds.


Marj fills these jugs with water from the CTD and then hauls them over to her station in the science lab.

Her station has 12 filterers, making for a jumble of plastic hoses and neatly arranged hourglass-shape cups. There are three rows of filters. Each row filters water either from the top, middle, or bottom of the sea. And in each of those three rows, she filters for the following: 1) Carbon 13 and Nitrogen 15, 2) fatty acids, 3) particulate organic matter, and 4) selenium. The first three—C13, N15, and the fatty acids—are called “biomarkers.” Biomarkers are essentially biological chemicals that are specific to a particular animal. By studying these biomarkers back at her university’s lab, Marj will be able to tell who is eating whom in the food chain. That, in turn, will help her determine a species’ habitat requirements.


Marj fills each 500-milliliter cup with water. Depending on the water sample, it may take anywhere from 3 to 10 liters of water to clog a filter with enough matter for analysis.

By comparing her results with Jackie and Lee’s long-term studies of, say, clams, she can better understand what is going on over time in one part of the food chain. Then, scientists can come up with much better estimates of how the food chain as a whole is changing.