News

An old species blossoms anew to pollute water

9/21/12

Cyanobac­teria are among the oldest organ­isms on earth — they were the orig­inal oxygen-​​producing species and are thought to be respon­sible for the direc­tion life has taken on earth. Nonethe­less, they aren’t the friend­liest of species. Cyanobac­teria pro­duce neu­ro­toxins, which can kill mam­mals in a matter of hours if ingested.

With today’s changing envi­ron­ment, cyanobac­teria are becoming more pro­lific in water­ways as dis­parate as the Charles River in Boston and Lake Taihu in China, said Fer­di­nand Hell­weger, pro­fessor of civil and envi­ron­mental engi­neering.

Hell­weger, along with three other prin­cipal inves­ti­ga­tors from the Uni­ver­sity of North Car­olina, the Uni­ver­sity of Ten­nessee Knoxville and the Uni­ver­sity of Texas Austin, have col­lec­tively received $2 mil­lion in funding from the National Sci­ence Foun­da­tion to under­stand the fac­tors behind cyanobacteria’s increasing presence.

“We know there are links with tem­per­a­ture and nutri­ents,” Hell­weger said. “But exactly how those things work together to cause this trend is still a mystery.”

Lake Taihu is the third largest lake in China, span­ning more than 2,000 square kilo­me­ters. In recent years, cyanobac­teria have plagued the waterway, which serves as the fresh­water drinking supply for sev­eral mil­lion people. From both a health and an eco­nomic per­spec­tive, this pol­lu­tion has the poten­tial to cause sig­nif­i­cant damage to the society, Hell­weger said.

Hellweger’s col­lab­o­ra­tors, Hans Paerl (UNC) and Steven Wil­helm (UT Knoxville), have been working on Taihu for a long time, col­lecting data on nitrogen and phos­pho­rous levels, nutrient set­tling, and cyanobac­te­rial growth rates, for example. “Now it is time develop a model to put all the data together,” said Hell­weger, whose exper­tise is in mod­eling com­plex water sys­tems for pre­dic­tion purposes.

“We want to be able to make pre­dic­tions for nutrient reduc­tion sce­narios,” he con­tinued. For example, if new policy is geared toward spending mil­lions of dol­lars to cut nitrogen levels in half, you’d want to know for sure that the approach would have a sig­nif­i­cant ben­e­fi­cial impact. “But it’s very non­linear,” said Hell­weger, explaining that even small changes in nitrogen or phos­pho­rous levels could impact the species that call Taihu home, including cyanobacteria.

Much like the cli­mate system, he said, there is so much going on that simple rea­soning is not suf­fi­cient for deter­mining out­comes. One needs to model many com­plex mech­a­nisms and sys­tems. But, “a model is always a sim­pli­fi­ca­tion,” he noted. “So we put in what we think is important.”

The team will start work by devel­oping a gene expres­sion pro­file of all the organ­isms in the lake. “This will tell us who’s there and what they’re doing. It’s up to us here at North­eastern to put it all together in a model, and to try to make sense of it,” Hell­weger said.

If suc­cessful, the model of Lake Taihu could set a prece­dent for under­standing the cyanobac­teria infes­ta­tions of water­ways across the globe, including the Charles River in the Boston area. His­tor­i­cally, sewage runoff has been the main pol­lu­tant in the Charles; today, cyanobac­teria now shares equal blame in making the Charles River unswim­mable, according to research at Hellweger’s lab. “If cyanobac­teria are increasing in the Charles,” he said, “it would not be sur­prising to find other local water­ways next on the list.”