After a long slog exploring the quirks of cyanobacteria gluing themselves to an invasive water weed, a research team has found a toxin that could be the culprit. Researchers discovered that the invasive Hydrilla builds up extreme concentrations of bromine compounds, 20 times greater than the concentrations in the lake bottom mud and 500 to 1,000 times greater than in lake water. An aggressively invasive water weed, Hydrilla verticillata, grows in thick masses that dangerous cyanobacteria love to colonize and hungry birds love to eat.