Duck weed in Langmuir cells, Puno Bay, Lake Titicaca
Duck weed, Lemna sp., concentrated at the edges of Langmuir circulation cells in Puno Bay, Lake Titicaca, Peru. When moderate winds blow over a lake, circulation cells are set in motion. Buoyant organisms, like duck weed, concentrate where the water currents downwell. Parallel rows of floating organisms or foam can sometimes cover a lake. In this photo, parallel rows are just beginning to form near a sunken ship.