Groundbreaking Research

Microbes and Molecules

Since the period of the Rockefeller grant, studies at Stroud Water Research Center have pioneered the investigation of energy flow in streams. As many as a billion bacteria, plus millions of protozoa and hundreds of thousands of diatoms, occupy a square centimeter of a streambed, and the collective efforts of such microorganisms provide or process most of the energy that supports the visible life of the stream. By teasing apart and reassembling a stream’s web of microscopic components, the Center’s scientists have sought to describe its unseen life.

Tom Bott, Lou Kaplan and chemist Rick Larson explored the linkages among watershed processes, dissolved organic matter and bacterial production. In the course of that work, they applied to freshwater systems a concept known as the “microbial loop”, which had been developed in marine studies. It suggested that bacteria play a vital role in the food web by using organic matter excreted by algae and becoming a direct food resource for more complex organisms. These investigations have advanced in two directions:

  1. What happens to the bacteria and how important is the transfer of energy through microscopic animals to higher organisms, such as insects and fish? And
  2. what is the chemical structure of dissolved organic matter and how does it influence the availability of food to groups of decomposers?

Later, Laurel Standley contributed to both efforts, following the transfer of toxins through the food web and using organic molecules to trace the movement of dissolved organic matter from the watershed to the stream.

Both strands build on the insights gained from the Rockefeller studies and the River Continuum Concept. Their goal is to understand the critical relationship between land and water in stream ecology and to describe the interconnectedness of microorganisms with the visible members of aquatic communities in our streams and rivers.