Andrea Calabrese - The Meaning of Algae

Webster's Third Addition describes algae as, "Any of several divisions of simple organisms: thallophytes, various one-celled, colonial, or filamentous, containing chlorophyll and other pigments (red and brown) and having no true root, stem, or leaf. Algae are found in water or damp places, and include seaweeds and pond scum." This is a very clear definition of what algae, or alga, is. Algae can also be defined as any group of chiefly aquatic nonvascular plants (as seaweeds, pond scums, and stonewarts) with chlorophyll often masked as brown or red pigment. Along with chloroplasts, algae may also possess photosynthetic storage materials and cell walls.

Algae is a general name used for the single-celled plant plankton, seaweeds, and other freshwater plants. Plankton consists of plants and animals occurring at any depth in bodies of water, often microscopic in size. All algae are of the kingdom Protista, except for the blue-green algae known as cyanobacteria, which is of the kingdom, Bacteria. Therefore, algae may be either prokaryote--organisms belonging to the domains Bacteria and Archaea that lack a membrane-bound nucleus, or eukaryote--organisms whose cells have their DNA contained within a membrane-bound nucleus.

There are eleven different divisions of algae. One of these is the scientific division, Heterokontophyta. Heterokonts, such as algae, produce cells having two stucturally distinct flagella. The heterokonts are a major line of eukaryotes. Most range from the giant multicellular kelp to unicellular diatoms, which are a component of plankton. Heterokont algae have chloroplasts surrounded by four membranes, the last being the endoplasmic reticulum. The chloroplasts characteristically contain chlorophyll. Originally, the heterokont algae were treated as two divisions, first with the kingdom Plantae and later the Protista.

There are eleven divisions of different types of algae. Each division of algae varies from one another, containing different pigments (colors), characteristics, origins, habitats, and classifications. Only one of these divisions of algae, classified as the cyanophyceae of the division cyanophyta (also known as blue-green algae) is prokaryote. The other ten divisions of algae are eukaryote. The ten types of eukaryote algae divisions are:

•  Rhodophyta (red algae)

•  Chlorophyta (green algae)

•  Euglenophyta (Euglenoids)

•  Chloromonadophyta (Chloromonads)

•  Xanthophyta (yellow-green algae)

•  Bacillariophyta (diatoms)

•  Chrysophyta (golden-brown algae)

•  Phaeophyta (brown algae)

•  Pyrrhophyta (dinoflagellates)

•  Cryptophyta (Cryptomonads)

Each of these divisions has one or more classes of different types of algae, and each classification has one or more different pigmentations. However, color does not necessarily categorize algae to a specific class, but the morphology of the algae does. Meaning, some algaes are colorless due to loss of chloroplasts over time, but are still classified in the same division as algaes with color.

1. Rhodophyta (red algae) –The majority of red algae consists of red seaweeds of the seashore. The pigment in red algae is phycoerythrin, which reflects red light and absorbs blue light, allowing photosynthesis to occur at greater depths of water. In Asia, Europe, and Japan Dulce and Nori have been popular sources of high vitamin human food for almost three hundred years. Some red algae can be found in tropical reefs, known as coralline algae, because they secrete a hard shell of carbonate around themselves, like coral. Unlike other algae, no cells with flagellum are found in any member of the group. There are around 4100 known species of red algae, almost all of them marine, and only about 200 that live in freshwater.

2. Chlorophyta (green algae) –Almost all forms of green algae have chloroplasts. However, there are many different types of chlorophyll pigments including: carotene, lutein, violaxanthin, and neoxanthin, causing many different shades of color to occur. Green algae also produce/produced embyophytes, known as “higher plants” and usually include unicellular & colonial flagellate with two flagella per cell. All green algae have mitochondria with flat cristae. Some of the first land plants evolved from green algae. The location of green algae varies depending upon classification. Some may be found on rock surfaces near high water marks, whereas other genera of green algae may be found occurring in small bodies of water, in sewage oxidation lakes, and in the soil.

3. Euglenophyta (Euglenoids) –This division of algae is known for unicellular flagellates of varying shapes. They are lacking a cell wall and many are colorless. Those that are not colorless possess discoid chloroplasts distributed throughout the cytoplasm. The Euglenophyceae possess an unusual form of nuclear division, and there is no evidence of a mitotic spindle. Euglenoids occur in both salt and fresh water where they are found in a variety of habitats.

4. Chloromonadophyta (Chloromonads) –A very small division of little known flagellates. They exist in freshwater bogs and ponds. The cells are pear shaped, having two flagella. The pigmented organisms possess numerous yellow-green chloroplasts. The algae of this Division have not been known to store starch, but oils instead.

5. Xanthophyta (yellow-green algae) –Usually possess two unequal flagella, the short one being simple, and the long one being pleuronematic. Yellow-green chloroplasts are derived from carotenoids, which mask the chlorophyll. There are many different genera of this division to be found. Some are free-floating, tree, soil, or rock dwellers, but most are freshwater inhabitants. Some of these may also be found attached to aquatic phanerogams. One genus, the tribonemataceae, can be found in sheets covering ponds and pools.

6. Bacillariophyta (diatoms) –A characteristic feature of these plants is their cell wall, which is composed of silica and pectin. Each cell contains golden-brown chloroplasts. Diatoms are unicellular, but often occur in colonial forms. They can be found in marine or freshwater plankton, and also as epiphytes on other algae and higher plants. Diatoms are also found on the bottoms of lakes, ponds, and in soil. As well as in rainforests of the tropics, on the leaves of the trees. The chloroplasts are olive green to brown in color and possess chlorophylls with fucoxanthin and acetylenic carotenoids. There is estimated to be apx. 100,000 species, and 200 genera of living diatoms.

7. Chrysophyta (golden-brown algae) –Unicellular organisms, lacking a cellulose wall, having pigments of chlorophyll and fucoxanthin. There are many different genera and many different families in this division. One example is the phaeodermatium, brown small discs found on stones in cold, quickly flowing waters. Most chrysophyta, however, are both marine and fresh water. Many form a major component of the nannoplankton.

8. Phaeophyta (brown algae) –Common brown algae of the seashore are mostly marine algae. Only a few fresh water species exist. The brown color is due to the fucoxanthin protein, which masks chlorophylls. Most of the species is confined to colder waters, many being restricted to the North Pacific. However, there are many different genera of brown algae having many different families with many different qualities. Phaeophytes are a large group of multicellular algae, including many seaweeds. The macrocystis kelp may reach 60 meters in length, forming underwater forests of algae. The upper part of the plant floats on the water surface, kept there by the blades of the leaves. One distinctive characteristic of this class of brown algae is the rate of growth, which averages 7 centimeters per day on the Pacific Coast of N. America, which equals apx. 1-1 ¼ blades per day. At a depth of 20 meters, whole fronds can grow as much as 45 cm per day, the most rapid plant growth known. Brown algae lack plasmodesmata and starch production of land plants and relatives. The colored flagellates develop into multicellular forms with differentiated tissues, reproducing flagellate spores. Many of the brown algae species are and have been used as food by the Russians, Chinese, and Japanese people. They were also valuable as a source of iodine, and as a potassium fertilizer.

9. Pyrrhophyta (dinoflagellates) –Most of the members of this algae division are unicells and are most noted for their large nucleus, containing distinct moniliform chromatin threads, even at resting stage. The products of photosynthesis are starch or fat. Characteristic resting cysts are also produced by many of these forms of algae. The majority possess flagella and get their class name of dinoflagellates because of the characteristic spiral motion of the motile cells. The chloroplast is a brownish color due to the carotenoid peridinin. Some dinoflagellates are also characterized by the ability to luminesce, and by the presence of potent neurotoxins. Although the majority of this Division are free-swimming or attached, marine or fresh water forms, they are also quite common as sand dwellers and parasites in fish and invertebrates.

10. Cryptophyta (Cryptomonads) –This division is interesting in that it is the only group that possesses chlorophylls and biliproteins. It is one of the few algal groups that synthesize a-carotene instead of b-carotene. The color varies from reddish-brown through olive green to blue green due to the presence of chlorophylls a & c, carotenoids, and biliproteins. The cells have a tetrahedral shape. Both marine and freshwater species are known of this class. One of this species, Tetragonidium verrucatum is a rarely found organism that has been recorded from freshwater ponds in Europe, the United States, and New Zealand.

There is also another important form of algae known to mankind as fossil algae. Fossil algaes have been claimed to appear in deserts, on other planets, and evidence of algae existence as far back as 3.5 billion years ago. The facts have yet to be determined or classified on many of these types of fossil algaes. However, “in 2002, William Schopf of UCLA published a controversial paper in the scientific journal Nature arguing that geological formations possess 3.5 billion year old fossilized algae microbes. If true, they would be the earliest known life on earth.” There have also been recent discoveries of green algaes and cyanobacteria found amongst 30 desert lineages, and further evidence has been studied regarding hypolithic algae. Hypolithic algaes grow on lower surfaces of translucent stones, existing on quartzite rocks that are translucent—allowing photosynthesis to occur, and have also been found embedded in soil.

The eleventh Division of algae is Cyanobacteria (blue-green algae, may also look reddish brown or bright green/blue) –Cyanobacteria differ from the other divisions of algae in that it is the only division of algae from the kingdom: Bacteria, and also the only algae to be considered prokaryote. Cyanobacteria is found in almost every habitat: oceans, fresh water, bare rock, and soil; and include unicellular, colonial, and filamentous forms.

Cyanobacteria produces one of three toxic metabolites: neurotoxic, hepatotoxic and non-specific (mostly cytotoxic effects). Cyanobacteria have lipopolysaccharides (LPS, similar to compounds found in the cell walls of harmful bacteria such as Escherichia coli), which can be harmful to the health of the human immune system. However, the mortality rate from cyanobacteria is most commonly heard of in veterinary reports of pets and livestock that have consumed of waters densely packed with algae. In humans, exposure to airborne components of cyanobacteria algae can result in irritant and allergic symptoms and are likely mediated by non-toxic cellular components of the algae. “The mouse bioassay is a method used to determine presence of toxic substrates in algae, and there are numerous laboratory methods for elucidating chemical structures from algae-tainted water.”—http://www.epi.state.nc.us/epi/hab/bgahh.html

Blue-green algae in small numbers are a natural part of the water system. In large numbers, algae will multiply rapidly, causing a “bloom” to occur, possibly turning the water a different color or causing a bad smell. Chemical changes in the water may offset an imbalance to the water’s ecosystem causing an unusual rapid bloom of algae to occur. This intense increase of algae on the water surface may affect many or all of the other elements in the algae’s surrounding ecology. Blooms are not always caused by only one species of algae, but may consist of several species. However, cyanobacteria can usually be identified. The rapidly multiplying algae, known as “algae bloom” may form a densely thick coating of foam or scum on the water’s surface. This will cause many changes to occur. For example, algae blooms cause a greater consumption of oxygen in the water due to a greater number of algae decaying and further stimulating growth of higher increased levels of bacteria. This de-oxygenation of the aquatic system will not only cause the immediate aquatic life and plant forms to die as a result of oxygen deprivation, but may also cause chemical changes in the mud at the bottom, lowering the oxygen value of the sediment, releasing chemicals and toxic gases. A thick algal bloom floating on the surface of the water may also alter or damage the community underneath by over-shading the aquatic life that is normally prone to nourishment by the sun. Algae blooms also disrupt bigger parts of the food chain because the entire ecology will need to adjust to the loss and inaccessibility of the previously existing aquatic life. i.e.birds, forest animals, and other seashore plant life.

Four decades ago, in the 1960s, there was a sudden burst of algae blooms rapidly occurring along the Great Lake shorelines. These drastic increases in algae blooms made human inhabitants miserable due to the outrageous size, smell, and drastic effect the algae blooms had upon the populated waters. This rapid increase in algae blooms caused policy makers to change the rules regarding elements of phosphorus pollution and industry requirements. One lb. of phosphorus can stimulate growth of up to 500 pounds of algae. To reduce the number of occurrences of algae buildup, legislatures in Michigan and some neighboring states imposed limits on phosphate laundry detergents in the 1970s. However, phosphorus continued flowing into the lakes from other sources.  These new rules contributed to reducing further dramatic increases in the algae blooms occurring there.

Today, further suggestions are being made to reduce the current number of algae blooms in Michigan to also limit the amount of phosphate produced and used in dishwashing machine detergents as well.

Another cause of the increase in algae blooms since the 1980’s is the arrival of two exotic species: the zebra mussel and its cousin, the quagga mussel. Mussels filter the water, allowing sunlight to penetrate deeper into the lakes, enabling algae to thrive at greater depths than before. This would contribute to greater levels of redox in the soils on the floors of the aquatic systems.

Other known disruptions in the normal ecology of algae are:

(The following reasons for increased algae blooms were taken directly from various lists from several different websites)

• Runoff into waterways with nutrients (nitrogen and phosphorus) from sewage, agriculture fertilizers, industrial effluent, etc.

• Poor water flow, Algae blooms generally do not occur in steadily moving water.

• Alteration of lake and river ecosystems through land clearing, agriculture and settlement, and water management systems (locks, dams, etc.).

• Eutrophication of surface water from industrial and agricultural activities has been cited as the stimuli for blooms.

• Temperature affects the oxygen concentration since warmer water cannot dissolve as much oxygen as colder water.

• Most of the Chesapeake Bays' more visible living resources will not survive exposure to waters of less than 1 mg/l for more than a few hours. Supersaturation (over 100% DO saturation) can occur when there is a large algal bloom. During the daylight, when the algae are photosynthesizing, they can produce oxygen so rapidly that it is not able to escape into the atmosphere, thus leading to short-term saturation levels of greater than 100%.

• The amount of oxygen dissolved in Bay waters is probably the single most important measure of habitat quality; without oxygen, all of the living resources familiar to us perish.