Hi all,
Algae, phosphorus and "optical brighteners" has been a hot debate for decades. The real problem is that once you have the phosphorus it doesn't really go anywhere, and a lot of farm land (via fertilisers) and water courses (via fertilisers, optical brighteners, PIMS and sewage) now have a phosphorus load that would take thousands of years to remove, even if we stopped the supply tomorrow.
In natural ecosystems nitrogen and phosphorus are definitely the "2 horse men of the apocalypse".
Because the phosphorus cycle doesn't have an aerial phase, isolated water bodies can potentially be kept in their natural state, but it is difficult to stop diffuse pollution from agriculture.
cheers Darrel