Blue Heron Green

I call this color Blue Heron Green because its development in the water garden is always preceded by the visit of a Great Blue Heron. This is only the third time in the history of the water garden that this phenomenon has manifested itself. It’s nothing to get concerned about, but it is rather startling to have the tiny pond flare up into a fluorescent pool.

The green color is the result of a bloom of planktonic algae. The development of this condition usually signifies a change in the ecological balance in the aquatic system. In this case, the change was the addition of one Great Blue Heron to the water garden ecosystem.

The water in the small overflow pool still exhibits the water quality that was found in the water garden three days ago. Algae eating tadpoles keep the water in the overflow clear. The same was happening in the big pool until the heron came by and effectively eliminated all tadpoles from the pool. I happened to come around the house and scare him off, but by that time he had already finished his meal.

Tadpoles are very adept at filtering floating material out of the water. The waste generated by the tadpoles acts as fertilizer that spurs the growth of more algae which is then eaten by the tadpoles. It’s like a self perpetuating system.

With the tadpoles gone, the algae is free to expand to the limits of its food supply. It won’t take long for another aquatic algae consumer to take advantage of this bounty. Last time this happened it was the daphnia that cleaned up the algae. By the time the weather turned cold, daphnia clouds filled the pool. They remained through the winter, but rapidly disappeared in the spring as predator populations expanded to consume the tiny crustaceans. I’m sure something has already begun to eat the algae and will soon emerge as the new master of the water garden.