In year one, the researchers finalized the experiment design, established the analytical protocols, cultured Tubifex tubifex, and conducted preliminary experiments. To keep the worms alive and active for weeks, the researchers redesigned the experiments for year two by reducing the amount of contamination in the sediments and increasing the water flow rate over the sediments to eliminate water-side resistances. Two complete experiments were conducted to evaluate the bioturbation potential of the worms in the absence of mucus. In the first experiment, the worms were added to microcosms almost immediately after the start of the water flow. Probably because of the presence of the dissolved organic carbon, the contaminant transport decreased for the first seven to ten days.
Researchers believe that the oxygen level changed the behavior of the worms.
Although the worms stayed submerged in the sediment when oxygen concentrations were high, they defecated on the sediment surface when oxygen concentrations were low. Therefore, a second experiment was designed to study the influence of the worms on the transport of pollutants specifically when oxygen concentrations were low. In the second experiment, worms were added about ten days after the start of the water flow. The influence of the animals on the transport was obvious. During this experiment, researchers also looked at the defecation rates of the worms.