Normally greenish water is healthy water. However when surface films or scums form one should be somewhat cautious. Bluegreen algae (Cyanobacteria) is interesting stuff. It is ubiquitous. The different species can exist as single cells, cells grouped or clustered into colonies, or cells can be linked end to end together to form filaments (trichomes). Tricomes can be single strands or clustered together to form flakes or mats. There are many types or species of Cyanobacteria (bluegreens). Many of the bluegreens are harmless, beneficial, and play important roles in the aquatic ecosystems.
Usually Cyanobacteria does not have as much nutritional value as the other main groups of algae. Thus zooplankton do not thrive on it per se. Although, the nutritional health food suppliment of Spirulina is a genus of Cyanobacteria.
A few species, and I emphasize a few, will become very abundant and a few, of the few species, IF abundant enough, will produce enough metabolites and or dedradation products to have concentrations that are toxic to mammals IF those mammals drink enough of the water containing the toxin. Usually 4 species commonly cause most of the problems. There are 4-5 genera that CAN at times cause toxin problems (2009-Lake Line Vol 29; Algal Toxins). The toxins are recognizable and measureable with gas chromatography. There are a lot of ifs for this topic.
As the newspaper article mentioned not all toxin producing Cyanobacteria form surface scums. When Cyanobacteria form surface scums the dissolved phosphorus is usually high and nitrate nitrogen is usually low. They typically develop in nitrogen limited systems. Most of the Cyanobacteria that form surface scums will obtain their nitrogen source from the atmosphere - nitrogen fixing species.
When you see a greenish or bluegreen surface film or scum one should be cautious. And not all of the Cyanobacteria scums have bluegreen hues / colors - some are at times green and will later turn blueish green as they age. Numerous harmless green and euglenoid algae will at times form greenish surface films. The only sure way to tell what type of algae it is, is to examine it under the microscope. One fairly simple way to usually tell if the algae film is potentially harmful Cyanobacteria is to put some in a bottle leaving a fairly large air space, cap it for about 10-20 minutes. Then remove the cap and smell the sample. If the sample smells vial, moldy, or offensively earthy/musty then it is likely Cyanobacteria and MAYBE producing some toxins. Other odors (fishy, aromatic, grassy, cucumber, geranium, violets) are often evident and not harmful or toxic. The toxins have to be injested and at high enough concentrations for them to cause the conditions of discomfort, illness, or death. Almost always low concentrations of the toxins are not harmful. Body weight of the victum has an influence. It all depends.
Last edited by Bill Cody; 11/16/09 10:09 PM.
