 |
This is a medium power
photomicrograph of Cladophora fracta
from Emigration Creek |
Green
Filamentous Algae
|
This is a medium power
photomicrograph of Cladophora fracta
from Emigration Creek |
Algae are plantlike protists found in the Kingdom Protista. Protists are eukaryotic, unicellular or multicellular organisms. Like plants, algae have chloroplasts, and their cells are strengthened by the cell wall. Algae refer to aquatic organisms that carry on photosynthesis. Algae are part of a fresh water's phytoplankton (phyton=plant and planktos=wandering), which produce energy that maintains an entire community of organisms. Not only do algae provide food, but they also play a key role in the stream ecosystem because they produce oxygen.
It has been customary to classify algae according to their color, which come in a variety of color such as green Chlorophyta, brown Phaeaphyta, golden brown Chrysphyta, and red Rhodophyta. All algae do contain at least one type of chlorophyll, but they also contain other types of pigments, which mask the color of the chlorophyll.
Green algae are the most plantlike of the all the algae. Green algae are believed to be closely related to the first plants because they have a cell wall that contains cellulose, they possess chlorophyll a and b, and they store reserve food as starch inside the chloroplast.
Some algae
are colonial, which means there is a loose association of
independent cells that are specialized for reproduction. Algae
that are multicellular have specialized tissues, but are not
considered to be plants because they are adapted to water
environments and have not evolved to protect their gametes and
zygotes from drying out. (Mader, pp. 524-526).
Habitats and Distribution of Algae
Green algae like to grow in wet places like lakes, ponds, ditches, and streams. They can also be found on damp soil and on the shaded sides of damp walls and trees. The chemical nature of water is a major factor that strongly influences the growth, abundance and distribution of algae. Some algae favor acidic conditions, some like neutral conditions and a few prefer alkaline conditions. (Flowers, pg. 6)
We think this picture of Cladophora fracta, shows cell division toward production of isogametes due to low-light conditions in a lab aquarium.
When examined with the microscope, Cladophora filaments are branched, which are often spaced distantly and sparingly. Fronds are the whole system of branched filaments and are attached to rocks on the stream bottom. Fronds of Cladophora are frequently covered with ephiphytic diatoms, in fact, there can be so many diatoms that it is difficult to observe the Cladophora cells. (Flowers, pp. 38-41)
When growth conditions are favorable, Cladophora reproduces asexually. The adult alga divides, forming zoospores or flagellated spores that are smaller than the parent cell. A spore is a haploid body that develops into a mature adult. When growth conditions are unfavorable, Cladophora reproduces sexually. Gametes from two different mating gamates come into contact and join to form a zygote. When a zygospore germinates, it produces four zoospore by meiosis. A heavy wall forms around the zygote and it becomes a resistant zygospore, which is able to survive until conditions are favorable for germination. The zoospores are haploid and are released in the spring to grow into adult algal filaments such as those shown in the above photomicrograph. Isogamy (GK. isos: equal and gamos: marriage, union) is the conditions where gametes are identical. These gametes are known as isogametes. (Mader, pg. 525).
Shown is the branching system of Cladophora fracta from Emigration Creek. The brown clumps found at the fork of the branches are epiphytic diatoms, Rhoicosphenia curvata
Biological Significance of Freshwater Algae:
Relationship to the Emigration aquatic food chain. Cladophora is a key player in the Emigration Creek food web. It directly or indirectly provides food or habitat for the following organisms: herbivorous mayflies, caddisflies, scuds and snails.
As mentioned earlier, the cell walls are an important habitat for epiphytic diatoms.Troublesome contamination of water supplies and runoff, see stormdrains.
Eutrophication is the excessive growth of algae in water.
Algae makes a great indicator for the degree of water pollution (Prescott, pg. 1) chemical
Water assists in the dispersal of algae. Water birds distribute algal spores, which are in the mud that sticks to their feet. The wind disperses algal microscopic spores through the air.
Water transports algal spores to new locations during flooding and normal runoff events.
Migratory aquatic birds bring about the transfer of plankton algae when they move from one body of water to another. (Smith, pp. 12-13).
Environmental Factors Affecting the Growth of Algae
Water is essential for the growth of the alga in a new location, but there are factors that may prevent its establishment and growth. Three factors instrumental in growth are light, temperature, the chemical composition and acidity or alkalinity of the water.
Light is essential for photosynthesis and Cladophora is found only in shallow water areas of Emigration Creek where there are openings in the riparian tree canopy, which allows sunlight to fall on the creek bed.
Temperature has a very important effect with Cladophora growing in clumps on stones in the summer and fall when water temperatures are warmer.
Inorganic compounds, such as nitrogen and phosphorous, are essential elements for the growth of algae. (Smith, pp. 13-15). A fall growth spurt occurs due to low water and the abundance of minerals from decomposing leaves and detritus.
Flowers, Seville. (privately published). Algae of Utah. University of Utah, Salt Lake City, Utah.
Mader, Sylvia S. 1998. Biology, Sixth Edition. The McGraw-Hill Companies, Inc., Boston, Massachusetts.
Prescott, G.W. University of Montana.1978. How to Know the Freshwater Algae, Third Edition. Wm. C. Brown Company Publishers, Dubuque, Iowa.
Smith, Gilbert M. Professor of Botany, Stanford University. 1933. The Fresh-Water Algae of the United States, First Edition, Fourth Impression. McGraw-Hill Book company, Inc., New York.
