Rock snot now reaches far beyond the waters of the Delaware River and into the halls of Washington, D.C.
More than a month after mats of woolly didymo blanketed the river from its upper branches in New York through to Trenton, U.S. Sen. Bob Casey has asked the Department of the Interior to help Pennsylvania combat the single-cell algae.
Mr. Casey said didymo could wreck the state's $1.6 billion fishing industry, and that populations of the algae also were spotted in the Youghiogheny River in Western Pennsylvania. Mr. Casey asked the Department of the Interior to support Pennsylvania's efforts to block the spread of didymo and strengthen the department's own work against rock snot.
Though the Delaware bloom was unprecedented, and scientists are unsure why rock snot infested the river in such abundance, it has begun to recede.
Eric Silldorff, a Delaware River Basin Commission biologist, said warmer weather and higher flows knocked down the didymo, or washed it away.
Mr. Silldorff discovered the blankets of rock snot in the Delaware River Water Gap in April and led scouting trips to other sections of the river to determine the range of the didymo invasion. He concluded in May that the algae was strongest north of Easton, but still present throughout the river all the way to Trenton.
The outbreak caught scientists off guard since rock snot prefers cold, nutrient-poor water. The stretches of the Delaware River south of the Water Gap are considered too warm and rich for the algae. Mr. Silldorff said no one knows why didymo was so abundant this year, but pointed to a warm winter and dry spring.
Mt. Silldorff added that scientists are concerned that once didymo is so widespread, it'll be with us for the long haul.
"We are worried that we could see blooms every year throughout the Delaware now, but since our winter and spring were so unusual, there is also a chance that this might be the worst we will ever see," Mr. Silldorff said. "We're developing plans now to monitor conditions next spring, and in subsequent springs to determine the future status."
No one is sure yet the impact didymo may have on the river. Scientists warned the algae blankets might crowd out beneficial plants that provide food and shelter for both fish and aquatic insects.
Rock snot spreads by hitchhiking on fishing gear, waders, boats, and anything else it attaches to in the water that can be carried out and to another body of water. The algae can live outside of water for a month or more.