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Visiting Scientists Study Benthic Micro-algae

Visiting Scientists Study Benthic Micro-algae

July 16, 2007

LUMCON often hosts visiting scientists, and this June it hosted a couple crates of benthic micro-algae, brought to LUMCON’s dock by two visitors — Louisiana State University Coastal Ecology Professor Brian Fry and LSU doctoral student Melissa M. Baustian.

Both scientists are researching how benthic photosynthesis — or, photosynthesis that occurs on the sea floor — might alleviate the low-oxygen (i.e. hypoxia or Dead Zone) problem plaguing the Gulf of Mexico. Here’s how it might work:

  • Organic materials settle on the ocean floor;
  • As they decompose, they suck up a lot of oxygen;
  • With little oxygen, the area at the sea flood becomes hypoxic (has too little oxygen for most organisms to survive);
  • If sunlight can reach the sea floor, however, it will cause photosynthesis to occur;
  • The photosynthesis reaction releases new oxygen;
  • Hypoxia is lessened.

Fry and Baustian are both trying to determine whether this chain reaction actually occurs. One reason for Baustian’s hypothesis that benthic photosynthesis is occurring and increasing oxygen levels at the sea floor is based on the fact that there is always some oxygen left on the ocean floor.

“Scientists are curious because the oxygen in the lower levels never reaches anoxia – which is zero oxygen. Why is that?” Baustian says. “Maybe benthic photosynthesis creates that little bit of oxygen, maybe it’s something else. But our research is just looking to determine whether benthic photosynthesis is part of the reason.”

To conduct her research, Baustian collects sediment samples from all over the Louisiana continental shelf and parts of the Texas coast. When she collects the sample, she measures the amount of light in the water at the time. Then she replicates those light conditions in a laboratory setting on LUMCON’s dock, where she studies just how photosynthesis does or does not occur and how hypoxia is affected.

But in order for any benthic photosynthesis to occur, sunlight has to actually reach the bottom of the sea. Murky water, which occurs naturally due to storms and slow-settling clay, often prevents that from happening. Still, if Baustian can help prove that benthic photosynthesis is beneficial – especially to the hypoxia issue – then others can research ways to increase the frequency of benthic photosynthesis.

Fry’s research focuses on how the benthic photosynthesis process might affect oxygen isotopes. Isotopes with greater mass require more energy to go through photosynthesis, and, according to Fry, if the oxygen isotopes found on the ocean floor are of the heavier variety that could be a roadblock to stimulating benthic photosynthesis.

“Isotopes are to oxygen like flavors are to ice cream,” Fry says. “There’s strawberry ice cream and chocolate ice cream, but in the end it’s all ice cream, it’s all the same substance. It’s the same thing with oxygen – it’s all the same substance, but there are different flavors of oxygen out there. And those subtle differences can change the way reactions might occur.”

Despite the potential roadblocks caused by turbid water and heavy isotopes, both Fry and Baustian are enthusiastic about the possibilities presented by benthic photosynthesis. As Baustian says, “If light can get to the bottom, benthic micro-algae can be the heroes of the Dead Zone.”


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