Algae and Friends

1. Why are algae important in nature? How are algae, fungi and lichens related and how is this relationship defined? Explain how the presence of algae can indicate either pollution or productivity of a body of water.

Algae are a very large and diverse group of eukaryotic organisms, ranging from unicellular genera such as Chlorella and the diatoms to multicellular forms such as the giant kelp. Most are autotrophic and lack many of the distinct cell and tissue types found in land plants such as stomata, xylem and phloem. The largest and most complex marine algae are called seaweeds, while the most complex freshwater forms are the Charophyta, a division of algae that includes Spirogyra and the stoneworts. Algae has several uses in nature and for mankind. Agar is a jelly-like substance, obtained from algae, which is derived from red algae, has a number of commercial uses. It is a good medium on which to grow bacteria and fungi as most microorganisms cannot digest agar. Alginic acid, or alginate, is extracted from brown algae. Its uses range from gelling agents in food, to medical dressings. Alginic acid also has been used in the field of biotechnology as a biocompatible medium for cell encapsulation and cell immobilization. Molecular cuisine is also a user of the substance for its gelling properties, by which it becomes a delivery vehicle for flavors. Algae fuel or algal biofuel is an alternative to fossil fuel that uses algae as its source of natural deposits. Several companies and government agencies are funding efforts to reduce capital and operating costs and make algae fuel production commercially viable. Like fossil fuel, algae fuel releases CO2 when burnt, but unlike fossil fuel, algae fuel and other biofuels only release CO2 recently removed from the atmosphere via photosynthesis as the algae or plant grew. Seaweed fertilizer, is seaweed that is collected and used as fertilizer. Today, algae are used by humans in many ways; for example, as fertilizers, soil conditioners and livestock feed. Edible seaweed are algae that can be eaten and used in the preparation of food. It typically contains high amounts of fiber and they contain a complete protein. They may belong to one of several groups of multicellular algae: the red algae, green algae, and brown algae. Seaweeds are also harvested or cultivated for the extraction of alginate, agar and carrageenan, gelatinous substances collectively known as hydrocolloids or phycocolloids. Hydrocolloids have attained commercial significance, especially in food production as food additives. Most edible seaweeds are marine algae whereas most freshwater algae are toxic. While marine algae are not toxic, some do contain acids that irritate the digestion canal, while some others can have a laxative and electrolyte-balancing effect. Algae also helps with pollution control. Sewage can be treated with algae, reducing the usage of large amounts of toxic chemicals that would otherwise be needed. Algae can be used to capture fertilizers in runoff from farms. When subsequently harvested, the enriched algae itself can be used as fertilizer.
Algae, fungi, and lichens are related by their mutual organism lichen. A lichen is a composite organism that emerges from algae or cyanobacteria (or both) living among filaments of a fungus in a mutually beneficial (symbiotic) relationship. The fungus benefits from the symbiotic relation because algae or cyanobacteria produce food by photosynthesis. The algae or cyanobacteria benefit by being protected from the environment by the filaments of the fungus, which also gather moisture and nutrients from the environment, and (usually) provide an anchor to it. Lichenized fungus may refer to the entire lichen, or to the fungus growing in it. The lichen combination of fungus with algae and/or cyanobacteria has a very different form physiology, and biochemistry than the parts growing by themselves. Lichens are said to be "species", but what is meant by "species" is different from what is meant for plants, animals, and fungi, for which "species" implies a common ancestral lineage. Lichens are really combinations of species from two or three different biological kingdoms, so there is no common lineage. By convention, lichens have the same scientific name as the fungus in them, and are not classified according to the species of the algae and/or cyanobacteria growing in them.
When algae is present in a water when they have the right conditions such as adequate nutrients (mostly phosphorus but nitrogen is important too), light levels, pH, temperature, etc. Generally the amount of phosphorus controls the amount of algae found in a freshwater lake or water body. The more nutrient-enriched a lake, typically the more algae in the water is present. When the water becomes polluted their usually with be bacteria growth present. Blue-green algae are actually bacteria. They are called cyanobacteria after the blue-green pigments that they produce. Blue-green blooms can form surface scums up to several inches thick, especially along the shoreline. Cyanobacteria are of greater concern than true algae because some species can produce potent toxins. However, even known toxin-producing species may not produce toxins all the time. If a blue-green bloom is composed of toxin-producing species, it is not possible to determine whether it is producing toxins without special testing. Even then, if a bloom tests non-toxic, it has the potential to become toxic. Therefore people and their pets are warned to avoid contact with surface scums whenever a blue-green bloom is suspected. Even if blue-green blooms are not toxic or are composed of a species that does not produce toxins, they are unsightly and when they decompose often produce bad odors. Blue-greens are also not very edible.

References
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"Lichen Biology and the Environment", Lichens of North America Information, Sylvia and Stephen Sharnoff.
"All About Agar". Sciencebuddies.org. Archived from the original on 3 June 2011
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