SPARE A THOUGHT FOR ALGAE: THEY HAVE THEIR BAD DAYS TOO

           
     As you look down into that persistent pea soup gloom which seems forever to be the colour of your pool water and also an image of how you feel after a really bad day, just think what itsTypical algae that may populate any pond anywhere in the world like for those that live down there.
     Everyone knows that that 'peasoupy' colour is caused by millions of microscopic single celled beings classified as plants. They come in a myriad of forms; 20,000 distinct species in fact. Many of them are more like peculiar basic forms of animals, with whip-like flagellae or countless hairy cilia that flick backwards and forwards to propel them through their universe; there are some that are like threads of green hair or bristles that attach themselves to some stable underwater surface; others can be globs of jelly or even just a frothy scum that floats on the water surface. These are the algae, classified as plants because they contain the substance chlorophyll, which enables them to synthesise sugars and starches from carbon dioxide and water, using sunlight. A by-product from this process is oxygen, which is great for the animal life of the pool or pond where there are not enough higher plants in the environment to fulfil the same role.

     But life ain't all basking in sunlight and flagellating around you know. These guys have their problems. It's stressful out there and it's so crowded, crowded with fellow beings that just wont letup their none stop consuming and proliferation. And what is it like to be so small that even the individual molecules of water are like massive globs of greasy jelly that you are constantly squeezing through? What is more, in amongst it all, there are cruising huge Titanic bugs and beasties that only have algae on their minds for breakfast, lunch and tea!

     So if you were some aspiring unicellular chlorophyceae how would you cope? In a universe like that, a humanoid from another dimension standing on the edge of the pool with a bottle of algicide in his hand is the least of your worries. The worst he will do is make a bit of space, wipe out a lot of the competition and predators and life will easier for a while until the population rises again.

               BIG FLEAS HAVE LITTLE FLEAS

     Algae are never more healthy than when the population is small and rising. The population is always rising if the nutrients are there and the competition is not. That is the constant occupation of algae, ensuring the population keeps rising. They usually do it as individuals by themselves with the main nucleus of the cell dividing and moving apart taking with it a proportion of the necessary ingredients to form a new cell. In other types like the Volvox or Euglena, smaller versions of the "mother" cell are formed within the cell wall or body. They grow to uncontainable size and burst forth in true John Hurt "Alien" fashion, but in number.

     When the pressures of population get so bad that even sex is not on the agenda, algae get sick and it is bacteria and fungi that live with them all the time that seem to become a problem. In our world, we as humans are happy to live with bacteria to a certain degree. They populate our armpits and finger nails. They toughen us up and make us resistant to other bacteria that would make us really ill. They even live in our guts and help us with our digestion. This symbiosis is something that helps keep us healthy whilst they feed on our exudes. But come the day when some unfamiliar bacteria breaks our natural barriers or some other factor reduces our resistance, it is very often the case these bacteria that live with us benignly for decades, can turn against us to the extent of helping to destroy us and ultimately consume us completely. So it is with algae.

     For some time now, Scientists have observed that the surface of many of the plants and animals in a pond are bristling with bacteria and fungi; either temporarily or permanently.  The 'simple'  cyanophytes, Nodularia spumigena and Aphanizomenon flos-aquae (otherwise known as Blue-green algae, which are the evolutionary link between 'true Algae' and the more basic bacteria ) have been seen to be colonised by stalked bacteria at very uniform distances. After a time, these are followed by micro-colonies of the cocci bacteria. Then rod forms become dominant made up of groups of bacteria piled on top of one another. These seem to prosper as the 
algae blooms, feeding on the slime on the surface of the algae. However some algae, particularly young algae or vigorously growing algae, seem to be remarkably free from them. It is believed that these algae release bactericidal or bacteriostatic substances that makes the plant surface inhospitable to bacteria.

      On the other hand populations of algae which are stagnating or declining are increasingly colonised by bacteria. On some of the attached algae, the coat of bacteria gets so thick on the basal parts that it serves as the staple diet for some protozoa and rotifera that graze it. G. Rheinheimer in his book on "Aquatic Microbiology" refers to these bacteria as 'Aufwuchs'.

     Many of these bacteria use the algae merely as physical support. Others feed from the nutrients expelled by the algae that are the by-products of the photosynthetic activity, such as amino and organic acids, sugars and even oxygen.

                  WORSE THAN FLEAS                  

     Being an alga and having bacteria crawling all over you is not the worst it can get. Some bacteria, and fungi too, are parasitic and even worse, pathogenic. There has not been much research on the bacterial level, but the fungus Polyphagus euglenae grows tendrils towards several free swimming Euglenae and holds them together. Then like a fungal octopus that feeds through its limbs, it saps the life force from its entangled hostages.

     Other fungi have self motile zoospores flicking flagellae through the globular world until a host is found and the flagella doubles as a spear to spike its potential host.  There is a Diatom called Asterionella formosa. Diatoms are algae with the added protection of a hard silicon coat. But for the Asterionella it is not so brilliant against a fungal parasite, Rhizophydium planktonicum, which multiplies whilst the algae blooms in spring. The peculiar thing here is that percentage of Asterionella cells infected always remains the same and it does not seem to affect the decline in the population even after it has reached its maximum. This is solely governed by the concentration of nutrients available and thus the host and parasite seem to live in harmony.

     There are various species of slime mould from the Labyrinthula that can live as a parasite in some of the higher forms of algae but would normally live like a small net strewn across the bottom of the pond.

     One fungus that puts the Venus FlyTrap and The Sundew to shame for its amazing agility is Ectrogella bacillariaceaum. This is a Saproleagniale (familiar types to the fish keeper manifest themselves as 'cotton-wool' growth on sick and dying fish). This attacks attacks diatoms and filamentous algae by growing long hyphae from which branch shorter hyphae. When touched by an algae or a rotifer, they secrete a sticky substance and the animal or plant is held. Then with great rapidity they grow into its mouth and inside to form a mycelium (the fungal equivalent to roots) which gradually absorb the contents of the animal's or plant's body.

                     BODILY PROTECTION

     The substances that some algae, particularly the Chlorophyceae produce to keep themselves free of bacteria are effectively antibiotics, which makes you wonder what potential for research is still down there in every pond to be done. The Cyanophytes have gone to extremes in producing chemicals for their own protection that can also affect the growth of other species. Back to Aphanizanomenon flos-aquae again, this produces an endotoxin capable of killing fish. Other genus such as Anabaena have caused dermatitis in human bathers, where as Nodularia spumigena has been blamed for the deaths of dogs, poultry, sheep, cattle and even horses. Human beings dont feel too brilliant either even after just swimming in the stuff. However, research is at present being carried out in the USA into the use of some of these chemicals exuded by Cyanophytes (the chemical Cryptophycin in particular) in the treatment of cancerous tumours since they have been shown to actively inhibit unnatural cell growth.

                 SYMBIOTIC SANCTUARY

     Another method of self protection that has evolved has been to seek sanctuary in another higher plant. A blue-green algae (another Cyanophyte) called Nostoc - this is the one that is capable of forming those disgusting looking jelly-like blobs that float around in some ponds - has been found living in the water fern Azolla, which provides it with its nitrogen needs.

                LOVE-HATE RELATIONSHIP

     It's a tough old world down in that pond. "Dog eat Dog" so to speak. But all the ingredients of that pond need each other. They are interdependent and by no means least, the bacteria and the algae cannot do without each other. The production of organic matter that sinks to the bottom to rot is mostly due to cyanophytes and algae. Although there is a process by which algae and bacteria work together to break down the organic matter to its mineral constituents, it is mainly bacteria and fungi that do the digestion process. For the environment to stay healthy, this process requires a considerable amount of oxygen and in the absence of oxygenating plants, this is provided by the algae. They in turn absorb the mineral products of the break down of organic matter. These are nitrates and it is plant food to them and any other plants that are there. Therefore if there are not enough of the higher plants to take up what nitrates that are produced by the breakdown of organic matter, the result can be the blooming proliferation that you see as that (wondrous?) peasoupy effect.

BIBLIOGRAPHY:

AQUATIC MICROBIOLOGY, G Rheinheimer

              POND LIFE, John Clegg, illustrations by Ernest C. 
                                                     Mansell
              Collins Field Guide - FRESHWATER LIFE, R. Fitter 
                                                  and R.Manuel