“Environmental management can’t wait for scientific certainty”- Ragnar Elmgren
Dr. Elmgren’s quote sets the tone for discussion of source water quality issues in our lakes and reservoirs, and the need for continuous monitoring to understand dynamic lake ecosystems. Sampling and being proactive equates to success.
If you’re not monitoring, you’re not managing!
What should we sample for? Where do we take the samples? How and How Often should we sample? These are frequently the questions asked when discussing lake monitoring programs.
Sampling Programs should include analysis for organic and inorganic material that is suspended, and/or dissolved in the water column.
Algae Identification for both species classification and biomass (cell counts expressed as cells/ml) are the most valuable analysis parameters. Identification of both Cyanophyta – cyanobacteria, commonly referred to as blue-green algae and Chlorophyta – green algae is important. For example, knowing the cell counts of cyanobacteria species provides the information needed to calculate the dosage rates of PAK® 27 algaecide to knock them out. Without speciation and cell counts we’re just shooting in the dark. The second most valuable parameter is the Total P & N. Total phosphorus (P) above 50 ppb, yes that is parts per billion, is trouble. We often see 100-200 ppb (P) and that is sure trouble. The dinner table is set for a Cyanobacteria Hazardous Algal Bloom (cyanoHAB).
Metabolites of cyanobacteria and green algae are useful indicators. Taste and odor metabolites, Geosmin and Methylisoborneol (MIB), are produced by cyanos, green algae, and bacteria. Sudden increases in Geosmin and/or MIB are often indicators of a cyano bloom. Cyanotoxins are just that, a variety of toxins produced only by cyanobacteria, and are proof that cyanos are present. There is no useful correlation for between the amount of toxins and the size of a cyano bloom.
Water chemistry analysis for alkalinity, hardness, conductivity, pH, phosphorus and nitrogen (P & N) are useful for establishing a practical and academic baseline. Increases in P & N, and pH are very useful indicators of algae growth and more specifically the probability of a cyanobacteria bloom. Increase in Chlorophyll a, Dissolved Oxygen (DO), Total Suspended solids (TSS), and Turbidity (Secchi Disk) are also valuable indicators of cyanobacteria bloom formation.
I frequently use the statement, “As a species, we tend to respond to situations instead of anticipating them”. There are few scientific certainties when dealing with lake ecosystems. One certainty is that cyanos can outperform their green algae cousins. Secondly, a healthy ecosystem is dominated by green algae. So, we must repeatedly monitor for cyanobacteria to know who they are, where they are and how many there are before we mobilize to remove them.
We will address the topics of where and how often to monitor in our next post.