07 May 2004

Doing Science in Brazil, Part 3: Robber monkeys and black river piranhas

Forrest M. Mims III

This is the last of three columns about research for NASA in Brazil's Amazon basin. A future series will describe smoke research in the heart of Brazil.

In last week's column my student partner, Damian Kilday, and I arrived in Manaus, Brazil, after two weeks of making numerous atmospheric measurements in Cuiaba.

After catching up on lost sleep, Damian and I made plans to take a river boat to the Ariau Amazon Towers Hotel some 56 kilometers (35 miles) away near the confluence of the Ariau with the Rio Negro. We were short on money, so we stocked up on bottled water before boarding our boat. Considering the price of drinking water at the hotel, that was a wise move.

Manaus is located just above the confluence of the Rio Negro with with the muddy Rio Solimoes, where the two rivers merge to form the mighty Amazon. The Rio Negro alone is huge! As our boat chugged against the current, I wondered how many thousands of Geronimo Creeks back in Texas it would hold. The river lives up to its name, for its water resembles very dark tea, a byproduct of tannin from decayed vegetation.

The sky was smoke free, and the huge expanse of the river provided a wide open sky perfect for making ultraviolet measurements. I was surprised that the ultraviolet level so near the Equator was much less than in Hawaii and no higher than on a typical summer day back in Texas. The reason is that the high humidity formed a hazy sky that blocked up to 20% of the sun's ultraviolet.

After a few hours, our boat turned south into the Ariau, a tributary of the Rio Negro. Soon we spotted one of the hotel's tall observation towers emerging from the bright green forest.

The Ariau hotel is constructed almost entirely in the trees. Clusters of tiny rooms are connected by catwalks to a multi-storied complex containing a registration area, restaurant and conference room. Wire window screens and double doors keep the monkeys out.

My original plan was to mount ultraviolet instruments high atop the tall tower, which my student assistant Damian and I promptly climbed. But it didn't take long for the monkeys to convince us to change plans and study the ultraviolet down in the rain forest.

Experiencing the Amazon rain forest up close was an adventure of its own. The humidity was so high that our shirts and my notebook were quickly soaked with perspiration.

One day we joined the hotel's river boat on a short cruise down the Ariau and across the Rio Negro. On the way we watched smiling women washing the hotel's white sheets and towels in the black river. As we reached the opposite side of the giant Rio Negro, we saw a motorized canoe with six European passengers. It was the first boat we had seen since leaving Manaus. The passengers had looks of determined terror on their faces as they furiously bailed water from their tiny vessel. They had good reason to be working so hard, for their overloaded boat was within a few inches of sinking. Their carefree pilot was providing them an Amazon experience they would never forget.

Back at the hotel, three terrified women from Spain couldn't enter their room since a long green and yellow snake was emerging from under their door. Sensing a great photo opportunity, I told Damian the real fun would begin when the hotel staff arrived to remove the visitor. We were soon treated to pandemonium and ear-piercing screams as a porter tried to catch the snake while the women tried to climb the walls. Later we took pictures of the smiling porter holding the snake and thanked him for the unexpected entertainment.

That evening a guide took us piranha fishing in a small boat. He passed around chunks of chopped chicken, which we speared on our hooks and dropped over the side.

After a few minutes with no nibbles, I began thinking that going for a swim in the black water might be more fun. Suddenly there was a loud "whack-whack-whack," and I looked back to see the guide slapping the water with his fishing pole. Within seconds he had hooked a glistening piranha nearly a foot long. He set the hook by slinging the fish clear out of the water and into the boat. Those protruding, triangular teeth killed any desire for a swim. Instead, we began whacking the water with our poles.

Back at the hotel, the cook prepared our piranhas for supper while we watched the monkeys and macaws. One of the monkeys took a liking to Damian and jumped into his arms. I quickly left, for we had been warned that the monkeys enjoyed emptying visitor's pockets and tossing their loot into the river far below.

Damian was more fortunate. Instead of stealing from him, his new friend gave him special monkey gifts. As we prepared to eat supper, Damian discovered those gifts as they began jumping from his shirt to the white plate before him. "Fleas!" he shouted. "Fleas!" And flee we did as all of us at Damian's table raced to another table on the opposite side of the dining room.

After three days at the jungle hotel, we left the sweltering Amazon and returned to smoky Cuiaba for a few more days of observations. Soon we were flying north from Sao Paulo with thousands of measurements stored in three miniature computers.

It was night, and a look out the window revealed familiar orange and yellow patterns scintillating in the blackness far below. South of the Amazon, Brazil was still burning. As our plane rose higher, hundreds of illegal fires reduced rain forest spires to blackened pyres

Back at Geronimo Creek it would take six long weeks to condense all the data into several scientific publications, including F. M. Mims III, Significant Reduction in UV-B Caused by Smoke from Biomass Burning in Brazil, Photochemistry and Photobiology 64, 123-125, 1996. The most important finding was that the smoke on some days was so thick that UV-B levels were reduced to almost nothing.

Viruses and airborne bacteria without protective pigments are quickly killed by natural levels of UV-B. Could the sharply reduced levels of UV-B in places like Cuiaba explain some of the increase in respiratory disease that accompanies the burning season?

At the time, I had no idea that this hypothesis would eventually lead to a return trip to Brazil, where I would make UV-B measurements and sample airborne bacteria on nutrient media films in a region where the smoke was so thick airplanes were sometimes unable to land at rain forest airports.

Forrest M. Mims III and his science are featured online at http://www.forrestmims.org/.

This feature was originally published in Forrest Mims's weekly science column in the Seguin Gazette-Enterprise, Seguin, Texas. The column is written for a general audience.