Algae Blooms

Algae Bloom on MDI High School Evaporation Pond

Algae Blooms occur on ponds and lakes when certain forms of algae form colonies that float on the water. They float on water but lack leaves. Never-the-less, Algae Blooms are included in the category "Floating-leaved Plants" for the purpose of this website. Algae can form colonies in many thousands of structures, some leaf-like. The species of algae number in the hundreds of thousands. Algae structures, whether single cell or multi-cell, are called "thalli" (singular: "thallus"). All algae are eukaryotic organisms. Planktonic algae are  thalli that float freely in water. Benthic algae are thalli attached to something causing them to be stationary relative to planktonic algae. Neustonic algae are thalli that thrive at the interface between water and the atmosphere. A neuston is an organism (not necessarily algae) that floats on the surface of water. Algae Blooms can consist of any of these thalli. Benthic algae, like Filamentous Algae, may become detached and float to the surface of the water body, Complex thalli can create thick mats floating on the water. However, Algae Blooms usually consist of simpler thalli that float on the water's surface producing a substance commonly called "pond scum." The photograph above shows an Algae Bloom on one of the evaporation ponds at the Mount Desert Island High School. Serious Algae Blooms like the one shown above, requires low oxygen and productive (Eutrophic) ponds. The high school ponds are generated by sewerage water from the high school guaranteeing a very high level of nutrients and living organisms in the water as well as low oxygen because as the sewerage decays, it consumes oxygen. High levels of oxygen in a body of water may discourage Algae Blooms or be an indicator that Algae Blooms are absent. The way Algae Blooms develop has not been definitively determined.

French Hill Pond is a mesotrophic pond, that is, a pond with moderate levels of vegetation and oxygen. Although Algae Blooms can occur in French Hill Pond, they will generally be small and short lived. Some Algae Blooms can make the water murky. A Secchi disk is used to determine the extent of such blooms. The following photograph shows some algae floating on the surface of a very shallow part of French Hill Pond. The environment in this small area includes a great number of decaying organisms and has little dissolved oxygen encouraging the development of neustonic algae. The turbidity (cloudiness) of French Hill Pond is very high but most of the material causing this high turbidity appears to be from sources producing tannin and similar chemicals. Such sources include trees surrounding the pond and plants like Sphagnum Moss (spp.). Microscopic examination and chemical analysis of the surface water at the deepest part of the pond has shown no significant algae contribution to the turbidity of the water for most of the year.

Small Algae Bloom on French Hill Pond

Algae are normally associated with photosynthesis and the algae cells may contain chloroplasts producing greenish Algae Blooms. Plastids (singular plastid) are organelles, that is, functioning subunits of a cell. They are parts of a cell enclosed in their own membrane or wall. Subcategories of  plastids will usually end in the letters "plasts." Green algae containing chloroplasts are in the division called "Chlorophyta." However, some algae lack chloroplasts but perform photosynthesis with rhydoplasts producing reddish Algae Blooms. Red algae are in the division called "Rhodophyta."

Algae colonies can be contaminated by chemicals or contain algae cells that produce colors of Algae Blooms other than green and red. Kelp, for example, is brownish. The scientific division name for kelp is "Phaeophyta." Algae encapsulated in a silica shell have the scientific division name, "Chrysophyta." Silica encrusted algae are called "diatoms." Some algae are capable of propelling themselves with flagella, tail-like appendages. These self-propelling algae are called "dinoflagellates" and have the scientific division name, "Pyrrhophyta." These Pyrrhophyta are often responsible for poisonous Algae Blooms, like red tide, and some ocean-based Pyrrhophyta are bioluminescent causing ocean water to glow at night. Therefore, Algae Blooms can have a variety of colors and textures. Note that the Algae Bloom in the high school ponds is yellowish green probably caused by the presence of extraneous chemicals, dead and decaying algae and various species of algae from the Cyanophyta (blue-green algae),  Xanthophyta (yellow-green algae) and Chlorophyta divisions. Note that the French Hill Pond Algae Bloom has both bright green and yellowish green algae. Many algae associated with Algae Blooms in fresh or salt water can be divided into classes/divisions as shown in the following table. This table is not exhaustive but represents what is most likely to be found in common Algae Blooms. Taxonomists may classify some of these algae differently. For example, Xanthophyceae is often listed in a large division/phylum called "Heterokontophyta" along with Chrysophyceae.


TYPE (Class/Division) COMMON NAME Medium
Bacillariophyceae/Chrysophyta Diatoms Fresh and salt water
Various classes/Chlorophyta Green Algae Fresh and salt water
Chrysophyceae/Chrysophyta Golden-brown Algae Fresh water
Cryptophyceae/Cryptophyta Cryptomonads Fresh and salt water
Myxophyceae/Cyanophyta Blue-green Algae Fresh and salt water
Dinophyceae/Pyrrhophyta (Dinophyta) Dinoflagellates Mostly salt water
Euglenophyceae/Euglenophyta Euglenoids Mostly fresh water
Phaeophyceae /Phaeophyta Brown Algae Salt water
Classifications in dispute/Rhodophyta Red Algae Mostly salt water
Xanthophyceae/Xanthophyta Yellow-green Algae Mostly fresh water and land



Floating-leaved Plants Technical Data and Information French Hill Pond Home