Eight-year-old Nicole Popp and other third-graders at Lanikai Elementary Charter School recently had an unusual guest speaker — her father, Brian, underwater in the Florida Keys.

The University of Hawaii geology-geophysics professor was on his third 10-day mission in the habitat Aquarius anchored 60 feet below the ocean surface in a coral reef. UH oceanography student Christina Bradley also was on the mission topside in a support role.

The kids asked the undersea scientist a lot of questions with the help of his wife, Jan Reichelderfer. She said the school had some technical difficulties with the video feed from the habitat's webcam “;but we had pictures of him and used a cell phone on a speakerphone for him to talk to the kids.”;

They asked questions about what the scientists eat in the habitat, how he comes out of it, what a hyperbaric chamber is and “;what being 'bent' means,”; she said.

He also told the students about his work on how global warming is affecting coral reefs.

Popp was one of four scientists and two technicians who began conducting the first “;saturation”; mission on the Aquarius Oct. 14 to study the effects of ocean acidification.

The Aquarius is owned by the National Oceanic and Atmospheric Administration and operated by the University of North Carolina. Scientists in the habitat are able to “;saturate”; or stay undersea for an extended time for diving and research by going through 17 hours of decompression at the end of a mission instead of going to the surface each day.

Describing the mission in an e-mail, Popp said the effects of ocean acidification on marine organisms have been studied mostly in the laboratory. For the first time, he said, “;We are using the unique capabilities of the Aquarius underwater habitat to study these effects on a natural coral reef.”;

Popp said they were focusing on the impact of ocean-bottom organisms on the acidity level of the water around the reef. The organisms release carbon dioxide when they breath “;and thus contribute to lower oceanic pH locally,”; he said. “;We want to be able to separate this local effect from the global effects of the increase in atmospheric CO2.”;

The Aquarius scientists used advanced new instruments and technologies for continuous measurements of changes in water chemistry from the surface to the sea floor. They measured the acidity level, water velocity and nutrient concentrations on the ocean bottom in what's called the “;benthic boundary layer,”; as well as in water above the reef, Popp said.

Hawaii's reef environment is very different from that in Florida but the general process of acidification is the same, Popp pointed out. The same techniques would have to be applied to Hawaiian waters to learn the effects of the changing chemistry on the coral reefs and organisms here, he said.