Confidence votes 4.8K. The base meanining of un pigeonnier is a dovecote (a structure where doves, or similar birds, are bred or housed). But you will also find un pigeonnier used to mean a garret-flat, or any small flat near the top of a building (especially if it is a low-rent sort of place).
Duckweed creates an anaerobic environment. When it comes to wastewater lagoons, the lack of dissolved oxygen is bad. (Read our previous article, Troubleshooting Low Lagoon Dissolved Oxygen, for an in-depth look.) Duckweed is a DO killer, blocking the oxygen-transferring interface between the surface of the lagoon and the atmosphere.
Overgrowth (Blooms) As with many other aquatic plants, duckweeds grow best in water with high levels of nitrogen and phosphate. Eutrophication of a body of water can produce these conditions and encourages the growth of duckweeds. As they grow, duckweed plants absorb these nutrients from the water.