If your pond or lake is more than a few years old, you have likely experienced a spring algae bloom that occurs FAR earlier than you would think possible. In northern climates, this algae bloom may even occur before the ice has melted! These early season blooms can be particularly troublesome and may contribute to early Spring fish kills. This post unlocks (literally) the cause of this bloom, AND gives you 2 simple solutions to the problem!
If you have ever noticed algae growth early in spring, it is likely a result of phosphorus that has released into the water column. Algae needs nutrients like phosphorus in order to grow.
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.
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 Bacteria Booster to the bottom sediments.
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.
Adding aluminum to the sediments is a viable solution but requires professional water quality analysis and application to treat properly and prevent pH imbalances in the water body. If you are interested in utilizing aluminum compounds to bind phosphorus we suggest that you contact us to discuss the options.
In addition, 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.