ALGAE

MAIN INDEX | Types of algae |
Algae blooms | Control of algae |

ALGAE ARE IN THE PLANT KINGDOM, BUT MAYBE THEY'RE NOT REALLY PLANTS! In Florida's freshwaters, algae are what make the water green, or even "slimy". However, green water is not necessarily undesirable, and neither are algae. In fact, algae are essential to the ecosystem and to life as we know it, and must be treated with respect. Algae are a diverse group of organisms which survive in all different types of habitats. From the dry desert, to the Arctic Circle, to boiling springs these organisms have found a way to extract enough from their environment to live in even the harshest surroundings. They range in size from microscopic to meters in length and in complexity from single-celled to complex organisms that would rival even large plants. Though these organisms may look like the true, "higher", plants, they are anything but, since they do not have roots or true stems and leaves.

Algae (AL-jee) is the plural form of alga (AL-gah) and most algae are primarily photosynthetic (make their own food). They are divided into two main groups:

1. Prokaryotes - are cells that do not have a nucleus or many other types of organelles found in eukaryotes. This group contains the blue-green algae (Cyanobacteria) and other bacteria in Kingdom Bacteria.
2. Eukaryotes - In essence, the cells of all other organisms contain nuclei and other organelles. All other Kingdoms are placed within this group (Protists, Fungi, Plants, and Animals).

Algae are one of the first steps of the food web. There are microscopic algae, like phytoplankton, and there are macroalgae, algae that can be seen by the naked eye. Algae occur naturally in all types of systems and may be considered indicators of ecosystem condition. Even the mere presence of a species can give an indication of the amount and type of nutrients that run through the system. Algae provide food for all types of animals, including fish, insects, mollusks, zooplankton (microscopic animals), and humans.

Lyngbya

Lyngbya is one of the groups of cyanobacteria that are of special concern. This long, hair-like organism is a filamentous alga that can form large benthic (on the bottom) and surface mats (blooms). Lyngbya normally grows in dense mats at the bottoms of nutrient enriched lakes and spring fed systems. These mats produce gasses during photosynthesis that often causes the mats to rise to the surface. At the surface, winds pile the algal mats against shorelines or in navigation channels; these mats can be several acres in size. Studies continue on what influences the cause and duration of lyngbya blooms. In some areas, the blooms cover so much of the pre-existing vegetation that it can cause serious damage and wipe out other species. In some places in Florida, lyngbya smothers eelgrass, a food of the endangered West Indian manatee. Some species in this genus have been linked to the production of a skin irritant leading to "swimmers' itch".

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Microcystis

This spherical, unicellular alga can form a colony (group of cells). A microscopic alga, when in bloom proportions it will turn the water a blue-green color. Some strains of Microcystis have the ability to produce a toxin known as microsystin. In abundance, this toxin is potentially harmful to animals.

Chlorophyta
Chlorophyta is a large and varied group, commonly referred to as green algae. The group includes unicellular, colonial and filamentous varieties of algae.

Spirogyra

Spirogyra are mostly freshwater species and are commonly found in shallow waters, around the edges of lakes and in ditches. This bright green, mat forming filamentous alga is slimy and has no branching. It is called Spirogyra because of the way the chloroplasts wind around the cell.

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Cladophora

Cladophora species are also bright green. It is a branching species and feels coarse when touched.

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Hydrodictyon

Hydrodictyon, also called water net, forms a net by joining five or six cylindrical cells. It can grow so large that the net can be seen by the naked eye. The best habitat is clear, eutrophic waters, but it is also seen in irrigation ditches and even rice fields.

Bacillariophyta

Diatoms

Diatoms are a group of algae often considered the most beautiful group due to the silica shell (glass) that houses them. These "shells" come in a wide variety of shapes and sizes and some species can form long chains when linked together.

Xanthophyta
Commonly called the yellow-green algae, many species belonging to this group were once placed within Chlorophyta. However, close observation of the placement and type of chlorophyll present changed scientific thinking.

Vaucheria

Vaucheria are filamentous algae with branched cells; they grow in dense mats that look like carpets of green felt.

Charophyta
This phyla is commonly called the stoneworts and is believed to be an evolutionary link to higher plants. They occur in lakes, ponds and streams attached to the bottom by rhizoids. This group is often mistaken for true plants due to the whorls of filaments that occur at nodes along the shoot of the organism. This group can grow to form relatively large areas of dense underwater monocultures .

Chara

Chara is commonly called muskgrass because of its distinctive odor. This submersed (totally underwater) alga grows in slow moving rivers and lakes, and can overtake other natural vegetation. Chara has a strong garlic-y odor when broken. There are leaf-like structures whorled at uniform intervals that have tiny thorn-like projections that make muskgrass coarse to the touch.

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Nitella - This is another submersed algae that grows in slow moving rivers and lakes. It looks a lot like Chara sp., but its leaf-like projections are smooth so Nitella does not feel rough when pulled through the hand. It is gray-green or yellow in color and grows in shallow and deep water attached to the substrate (the bottom). Some species are a few inches tall; others are as long as three feet or more.

Blooms can have far reaching effects on the environment. Some can become so dense they can ultimately cause a problem with low oxygen levels. A decrease in oxygen causes hypoxia (low oxygen) or anoxia (no oxygen) and the other organisms in the water that need oxygen to survive, such as fish, become stressed and may die. Other blooms may release toxins that can be harmful to animals.

There is a general consensus that rapidly growing human development, and increased human use and disposal of nutrients over the past few centuries, has increased the frequency and intensity of algal blooms in many regions of the world. This has created a global effort to control harmful blooms.

The most direct way to control blooms is to reduce the availability of nutrients. Most water management organizations throughout the world are actively pursuing a variety of nutrient control strategies. However, for some aquatic ecosystems nutrient control is impractical, ineffective or simply too costly. For some cases chemical or biological treatments can be helpful alternatives when administered properly.

Chemical Treatments
Copper sulfate (bluestone) and chelated copper compounds such as Cutrine-Plus, Algae Pro, and K-TEA, as well as Endothall are common chemical treatments used to kill algae. Chemical compounds that shade out the light for algae growth, e.g. Aquashade, are also used to control blooms. Each chemical has its own restrictions and toxicity to animals. Read the directions carefully before application and consult a professional before starting your own treatment program.

Municipal water authorities often treat potable (drinking) water reservoirs when the algal count exceeds a certain number of cells per mililiter of water. Blue-green algae numbers usually increase late in the summer, often imparting a foul taste and odor to the water, and people find it unacceptable. Although used only temporarily, copper herbicides are applied to the water to lower the algal count, thus making the water more acceptable to drink.

Biological Treatments
The main biological treatment that is employed today is the use of various carp fish species to control submersed and floating algae. Grass carp (Ctenopharyngodon idella) is mainly used for aquatic weeds and attached submersed algae, such as Nitella sp., and Chara sp. Where they do not prefer filamentous algae to eat, grass carp will eat Lyngbya. The silver carp (Hypophthalmichthys molitrix) has been shown to be an effective treatment for controlling filamentous algae, including blue-green algae.

Both species are non-native species and there are many restrictions to employing them as a means of weed control; some states prohibit their use altogether. When they are allowed, the use is restricted to triploid carp. Triploid carp have an extra set of chromosomes that render the fish sterile, therefore prohibiting a population explosion if the fish escapes into an uncontrolled area.

These fish are an economical choice and have proven their effectiveness in controlling the growth and spread of algae in some circumstances. However, there also has been a mixed outcome when using carp as a means to control aquatic blooms. For example, the grass carp may consume the non-nuisance vegetation and leave the noxious algae as a second choice. Research is still being conducted on why preferences change between lakes and over time.

Physical Treatments
Physical treatments for algae in ponds include aeration and airlifts. While aeration does not kill or remove algae from the water, it oxygenates and stirs the water column, and can create conditions to shift from toxic and smelly blue-green algae to preferred green algae species. The resultant algal population is usually not as dense or as toxic to other organisms in the ponds.

Mechanical Treatments
Harvesters are sometimes used to skim dense mats of blue-green lyngbya alga from the surface of lakes and rivers. Lyngbya normally grows in dense mats at the bottoms of nutrient enriched lakes and spring fed systems. These mats produce gasses during photosynthesis that often causes the mats to rise to the surface. At the surface, winds pile the algal mats against shorelines or in navigation channels; these mats can be several acres in size. Managers have developed a process called "grubbing" whereby harvesting machines lift the mats off of submersed plants such as native eelgrass, without cutting the eelgrass. By removing the blanket of lyngbya from the eelgrass, the plants grow and expand. Eelgrass is an important food source for manatees in the Crystal and Homossassa Rivers.