White Paper: Paradigm Shift For Blue-Green Algae Control Through Long-Distance Circulation (LDC): Empirical Experience With SolarBee Circulation Since 2000

Eutrophication refers to the enrichment of available food in aquatic systems, with algal productivity (i.e., the rate of algal production) representing the cornerstone of the aquatic food web. Algae will grow as long as they have sufficient dissolved inorganic phosphorus (DIP; e.g.,phosphates), dissolved inorganic nitrogen (DIN; e.g., nitrate and ammonia), light energy for photosynthesis, and suitable temperatures. The availability of dissolved inorganic carbon (DIC; e.g., carbon dioxide, bicarbonate) and micronutrients (e.g., silica, iron) can limit algal productivity, but DIP and/or DIN are typically the limiting nutrient(s) in freshwater lakes and reservoirs. So, algal productivity typically increases as more DIP and DIN enter a lake.

However, all algae are not functionally or ecologically equal. Blue-green algae (cyanobacteria) are both morphologically and functionally different from non-blue-greens, such as diatoms, greens, and flagellates. Blue-green algae are one of the few organisms on the planet that have adapted to stagnant conditions, and have evolved internal gas vesicles that allow them to regulate their buoyancy in the water column. During the day in calm waters, blue-green algae can come near the surface in order to give them a competitive advantage over non-blue-greens for light, atmospheric carbon dioxide, and atmospheric nitrogen (N2, for those blue-greens capable of incorporating or "fixing" N2 directly). At night they can settle down into deeper, more nutrientrich waters. Many species of blue-green algae also contain a variety of cyanotoxins. One significant ecological implication of these cyanotoxins is that zooplankton, macroinvertebrates, and fish do not like to eat them. So when blue-greens die, they tend to sink to the bottom of the lake where their decomposition can deplete bottom waters of dissolved oxygen (DO). Anoxic bottom waters are not only detrimental to fish, but these conditions have other undesirable consequences characteristic of eutrophication (described below).