The Mysterious Spring Algae Bloom...SOLVED
Water quality begins to change as life becomes more active in the pond. Here are examples of whats happening beneath the surface:
- Rising water temperature causes mixing to occur (called turnover)
- During turnover nutrients are stirred up in the pond
- Fish and other aquatic life are becoming more active
- Algae begins growing at the bottom of the pond
- All of the dead vegetation from last year is breaking down
Natural changes occur each year in ponds as the seasons change. Ponds experience turnover in the spring. This is when waters that are warm and oxygen-rich move to the upper layer of the pond, and cold, oxygen poor water moves to the bottom of the pond (the opposite occurs each fall). Ponds/lakes with heavy ice cover often experience low oxygen levels throughout the water column particularly in late winter/early spring. This stresses fish and triggers chemical changes in the water and sediments.
As a pond or lake ages, bottom sediment accumulates phosphorus. Older water bodies often have very substantial accumulations of phosphorus in the bottom sediments.
This phosphorus takes on many chemical forms which bind to components of the sediment. The chemical bonds take on several forms. Phosphorus that binds to Aluminum in the sediment is PERMANENTLY locked to the sediment and will not be available in the water column to feed that nasty algae bloom.
Stick with me.... this is the important part!
Phosphorus that binds to Iron particles is bound only as long as oxygen is present. As soon as oxygen is depleted from the bottom water, BOOM, a chemical reaction releases the phosphorus connected to the iron particles into the water column. The phosphorus concentration immediately increases and algae blooms begin.
Because algae is a plant, it produces oxygen during daylight hours - BUT - also uses oxygen 24 hours-a-day. This night-time use of oxygen can starve the water column of oxygen and release more phosphorus. Even worse, if the pond/lake is still under ice, the depleted oxygen can cause a significant fish kill.
So, how do we fix the problem? There are two pretty obvious solutions.
- Utilize a bottom aeration system to ensure that oxygen concentrations at the bottom stay high and prevent the iron-bound phosphorus from releasing.
- Add aluminum compounds or other phosphorus binders such as Phosphate Eliminator to the bottom sediments.
- Routine beneficial bacteria treatments to break down muck and nutrients
The best style of aeration to eliminate stratification (the layering of oxygen rich and oxygen poor water layers) is a bottom plate aeration system. These systems operate all year long to keep water circulated.
We always recommend regular treatments with beneficial pond bacteria to prevent excess ammonia and nitrogen which can impact fish health and contribute to algae blooms. Reducing the muck layer decreases the nutrients releasing into the water as well.