Re: Do protists affect the enviroment around them? Example, The P.H. of water?

Joe:
     Sorry for the delay, we are usually faster than this, but here is 
your answer regardless...  This is a really neat question.  It is easy to 
see how humans affect the environment, such as landfills, buildings, and 
pollution, but determining how and if protists change/affect their 
environments is a little more difficult.  The answer to your question is a 
definite YES!  Before I discuss some of the changes we need to talk a 
little bit about which environment we are examining.  There are multiple 
environments for any creature or object, but for our purposes we can 
identify two, the microenvironment, or the area in and around the 
protist, such as the dirt, pond scum or water, basically its little corner 
of the Earth, and the macroenvironment, or essentially everything else...
     All organisms affect their immediate environment, by breeding, 
eating, producing waste etc. and these metabolic functions are the primary 
source of changes such as pH (Which is a great example actually, good 
job!), mineral and molecular content, etc. etc.  In fact, think of the 
microenvironmental changes an amoeba makes if it gets into your intestine... 
They are severe enough to cause serious diarrhea and dehydration, which 
with this organism is called dysentary.  In this case, the protist is 
making specific environmental changes to adapt and survive in the host, and 
in the case of the pond scum type organisms, the major observable changes 
are a result of metabolism by-products.  
     Next, the macro environment.  Protists (And like organisms) affect 
this environment as well, but only in large numbers.  The waste and 
products of 1 protist in a pond is essentially zero, but trillions and 
trillions of algae are responsible for a large portion of the oxygen 
generated on this planet as a result of photosynthesis.  Now that, is an
enormus change in the marcoenvironment.  In some water systems, algae and 
protists overgrow to an extent that they kill off everything else within 
that mini-macro environement, this is called eutrofication.
     Another argument could be made for food chains being an important
example of affecting the environment.  A protist is eaten by a water flea, 
which is eaten by an insect, which is eaten by a fish, which someone 
catches and you eat... so you have the energy necessary to write the Mad 
Scientists to ask about how protists affect the environment.  I  hope this 
gives you some help with your question, it was a really good question, and 
as you can see has lots of directions in which to take it.