Spirogyra

Recently, the instructors at Brunswick took myself and another student to the ponds and showed us certain common elements that are important to proper pond management and care. One of the important things I learned was about filament algae, and the threat it poses to fish.
Algae Pond Scum
Pond with filamentous algae, at Brunswick Community College
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Filamentous Algae
Filamentous algae, at Brunswick Community College
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Filamentous algae are microscopic algae that form colonies of “filaments” — hence the name. These algae are notorious for forming the large, pillow-like mats of algae that float on the surface of ponds. Common types found in Ohio include Spirogyra and Pithophora.
Disadvantages
As in the case with planktonic algae, high levels of nutrients can cause filamentous algae abundance to explode, especially in ponds lacking other aquatic plants, becoming so abundant that severe oxygen problems can result in the pre-dawn hours during July and August. Treating a severe filamentous algae problem in summer will almost certainly cause a fish kill. Ohio State University Extension Fact Sheet A-8-01, Winter and Summer Fish Kills in Ponds, provides insight into how these types of summer kills occur.
From Benefits and Disadvantages of Aquatic Plants in Ponds, Ohio State University Extension
Filamentous Algae

Filamentous Algae

Algae are primitive aquatic plants that differ from other plants in that they have no true stems, leaves or roots. They have a place in the overall food chain as they convert the energy of the sun into forms that can be used as a food source for other aquatic life. Algae also help to increase dissolved oxygen in water. Algae grow in both fresh and salt water systems. There are said to be over 20,000 different named species of green algae. Algae occur in three different basic forms. These are categorised as planktonic, filamentous and macrophytic.
Worldwide, there are over 400 different species of the genus Spirogyra. Spirogyra tends to show in ponds as a tangled pond scum. It is also called “water silk”, “silk weed” and “mermaid tresses”. On sunny days, the mats of spirogyra filaments usually float on the surface of the water. They are kept afloat by tiny bubbles of oxygen arising from photosynthesis. These algal mats then sink when the sun goes down and the process reverses as photosynthesis is reduced. As a result, the strands of Spirogyra consume oxygen for cellular respiration. Carbon dioxide is then produced as a waste product. Where there are thick algal mats present, large fluctuations in the dissolved carbon dioxide and oxygen levels in the water can occur. This can lead to rapid changes in the pH of the water that in turn can cause stress and even death to other organisms, eg fish, living in the water.
Blanket Weed and other Pond Algae


Spirogyra
Spirogyra - A Filament Algae, magnified at +/- 40x
Spirogyra

Spirogyra

Spirogyra

Spirogyra

Spirogyra

Spirogyra
A Desmid and Spirogyra algae found in the pond sample.

Cladoceran
A Cladoceran found among the algae sample.

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