Scenedesmus
sp. quadricauda and PollutionScenedesmus
sp. quadricauda and PollutionScenedesmus grows, reproduces and survives because it is a living organism. It shows a complex structure of a prop system in pectin. It remains a sensitive alga to work with. Scenedesmus is sensitive to cation concentrations and it's growth will be stopped by a 30ug/l concentration of silver. Most of the research focuses on involving the algae with concentrations of organic and inorganic compounds.
Silver can take inorganic or organic forms and is toxic to most plants. There is a difference in the rate of absorption in the research of depending on the nature of the cation. Mercury is also thought to be toxic to plants. Deficient environments are also known to have an effect. With iorn and/or calcium the same genera show a mutation. Copper too is a cation and it's presence in copper sulphate can cause algae to bloom and is used as a limiting control. This is a metabolic trigger for the pychologist to be aware of in the study of pollution.
These cations in their inorganic and organic forms are all available in water to provide the algae with nutrients necessary to growth. It is only when concentrations are toxic or types are not right that growth is retarded. Deficient amounts cause the scenedesmus to mutate while excess amounts cause the species to die. If a species dies, then it might be assumed that humans might die as well. Knowledge of algae survival(backed up by research) can tell us that the environment is safe from heavy metals.
Normal is a funny thing, while many of classifications are written like Fritsch and Prescott there are no absolutes. Mutation of the scenedesmus goes to show that this is true. Normally a colonial alga the quadricauda is a complex algae. In modern research the deficient amounts of iorn or calcium are showing us a spineless variety of another species. This too leads to the conclusion that nothing is absolute. The mutations form is a matter of guesswork and even the well trained phycologist would only be extrapolating in determining the morphology. The work of D. M. K. Hudson is important research in this direction. The absolute here is that mutation does occur, not that it occurs in some predicatable way. Change of morphology can be associated with adaption through the theory of evolution.
Oxidative assimilation is what is meant in the normal systhesis of organics. This occurs when light is insufficent, such as deep in the water. This might explain why organic forms of mercury seem to be different from the control in the research of D. M. K. Hudson. Of course, this speculation is one of survival and it proves that the quadricauda is tougher than first thought.
In Tech Beat a column from Civil Public Works(jan. 1986) it is suggested that common garden algae chlorella is a good absorber of pollution. This is another viewpoint on the algae as it enters into ecology.
Just as modern farmers use fertilizers of potassium and nitrogen, algae could be used by the oil or chemical industry to clean up spills that have occurred from boats or pipes. Other types of algae may also have absorbing properties which could be determined through experiment. If a polluted creek or stream were found in the location of a small or large chemical plant an experiment could be set up. Harvesting techniques which would allow the experimentor to place large amounts of chlorella on to the creek surface are needed. Also a measure of how much alage is being used and a systematic way of determining what the results are in terms of clean up would be needed.
While many people believe the algae to be an evil smelling problem it too has it's problems. This kind of attitude will stop it from becoming a food. It will also prevent us from saving this important element in the ecosystem. We have seen, that it can be toxic as in the case of dinoflagellates or that it can be a problem relating to drinking supply. It is though a possible food or if processed can be a number of things ranging from an ink to maybe even an explosive. If we do not have an objective viewpoint we may not see it as essential to many aspects of life. It certainly is part of rice cultivation and it too can be endangered by the presence of inorganics. This is probably just a part of the natural competition for survival, but when pollutants are destroying or mutating the algae it may be controlable. The attittude could be that it is a thing to be controlled by powders or metals and natural predators.
In Algae as ecological indicatorsthe great minds of oceanographers, phycologists and marine biologists are put together to find new experiments for research. This book shows some applications for phycological knowledge. The results of one of the presentation in class pointed this out as well. The choice of an algae will show us what the environment is doing. In fact, the scenedemus could also be placed in an assay to determine water quality. The many results in relation to S. quadricauda are making it the right alga for the job.
Scenedesmus quadricauda is one of the strains which was researched by D.M.K. Hudson. Here is a quote from his research:
"Pigmentation changes which occurred were
observed to consist of a general loss of
pigment accompanied by a change in colour
affecting cells."This was shown to be true for six algae tested. Perhaps the colour of the algae would be all that is necessary to observe.
Growth curves from the above show just how sensitive the various strains were. Chlorella vulgaris is a strong algae at 0.1 ppm of mercury nitrate it had a higher dry weight than for any concentration. Scendesmus quadricauda also showed this type of strength. Initally at 10.0 ppm which was the most concentrated it showed a jump at 5 days. This has something to do with the metabolism of the strain. The compounds tested were mercuric acetate, mercuric chloride, mercuric nitrate, phenylmercuric acetate and phenylmercuric nitrate. This is interesting research. The modern research is showing us the way to safer environments. A genuine application of the pychologists knowledge.
Chlorella vulgaris may remain the most common alag but it has competitors. Dinoflagallates may become of interest because of their toxicity. Scenedesmus sp. quadricauda is interesting for it's colonial form, it's complex structure and it's reactions with heavy metals and pollutants.
Copyright by Peter Timusk.
