Green Algae Blooms in Ponds
Algae is a group of microorganisms that make their way into water bodies of all sizes. Algae cells can be carried to water by bird, land animal, boat, fishing gear, and even the air! The proliferation of algae depends on nutrients and sunlight to grow.
Types of pond algae
- Filamentous Algae
- Planktonic Algae
- Macroalgae (Chara)
Filamentous algae is commonly called string algae, hair algae, or pond scum. String algae begins growth at the bottom of the pond. There are many species of filamentous algae so not all algae blooms will look the same.
String algae can look like green mossy mats, slime or long hair-like strands. The color of filamentous algae is normally bright green to dark green.
Pithophora is a type of filamentous algae that has a cotton-like consistency. Spirogyra feels like wet silky hair.
As string algae matures it eventually releases to the surface of the pond. It becomes buoyant from the oxygen it is producing.
Is string algae bad for a pond?
While filamentous algae may not be visibly appealing it can provide some benefit to the pond. Algae is an essential part of a pond's ecosystem. It is a food source for invertebrates, protozoans, and fish.
If algae is covering the majority of the surface, this is a natural indicator that there are excess nutrients within the water. Steps should be taken to reduce nutrients to healthy levels within the pond or lake.
Planktonic algae is commonly referred to as green water algae or pea soup algae. This single celled algae particles float freely throughout the pond causing water to appear discolored. Coloration of planktonic algae forms can be green, yellow, blue-green or brown.
Planktonic algae blooms can be a sign of a serious imbalance in a pond which can cause harm to fish. If visibility of pond measures less than 18 inches from the surface, steps should be taken to improve water conditions.
Algae Blooms can lead to fish kills
Like all forms of algae, planktonic blooms produce oxygen during the day. Algae consumes oxygen at night. A heavy planktonic bloom can result in a fish kill from oxygen uptake at night. These kills can also occur when there are consecutive overcast days. When sunlight is blocked, the planktonic algae consumes oxygen during the day instead of producing it.
Green Water Algae
Chara and nitella are types of macro-algae. They commonly misclassified as submerged weeds but are actually forms of algae. Chara is also known as muskgrass.
Chara algae produces stems with leaves growing in whorls around the stems. There is a gritty calcified outer coating. Chara has a skunk-like odor. It is typically found in hard water.
Nitella has similar looking growth to chara but lacks the gritty calcified coating and has no odor. Nitella algae is more delicate than chara. Nitella is typically found in acidic or soft water.
There is no root system with these macroalgae forms. Just like string algae, growth begins at the bottom of the pond and then releases to the surface in mats.
Algae Control Treatments
The knowledge Base for Pond and Lake Management