The progress of scientific discovery is always slow, even on life and death matters. It is slow because it follows a strict form. Roughly put, science requires that we check and recheck what we think we know. Then, it advances into the areas of what we do not know and sorts what we do not know into the categories of what we do not need to know, what we know we need to know and what we don’t even realize we need to know. Then, research begins and continues.
This is true whether we are discussing the COVID pandemic or the state of Canandaigua Lake. A headline in Aug. 26 Daily Messenger, “Researchers find foam, algae connection,” could be misread by the lay reader as “source of toxic algae growth found” and this would be untrue.
True, a connection between lake foam and a type of cyanobacteria has been posited. But everywhere in the report delivered recently by Global Aquatic Research LLC is the refrain, “more research is needed.” The report documents a connection between the appearance of lake foam 20 or more years ago, the introduction of dreissenid mussels into the lake at about the same time, and the appearance of blooms of toxic cyanobacteria in late August and early September in the last five years. No causal relationship between foam and cyanobacteria is suggested in the report. In other words, the appearance of foam and cyanobacteria may be a coincidence.
Science is often divided into “pure science” and “practical science.” In the case of both the COVID pandemic and the blooms of cyanobacteria, we have intense practical interests in what causes these problems and what can be done about the causes. Our need is for practical science, not science for its own sake.
First, what we think we know about the recent blooms of cyanobacteria (the oldest organism known of on earth) can be summarized thus: The temperature of the surface waters of the lake (the water above the thermocline, the region where the cold, deep waters and the warm, sunlit surface waters meet) is rising and more conducive to their growth. The thermocline in the lake in summer is falling. These conditions have been well documented by Dr. Bruce Gilman, and the only explanation I have heard for this phenomenon is global warming.
Second, we know that the dreissenid mussels arrived in our waters about 25 years ago from eastern Europe, where they were part of the ecology of other (foaming) lakes. These mussels, whether zebra or quagga, feed by filtering algae from the water. The algae grow predominantly in well-lit waters. The dreissenid mussels can distinguish algae that “taste good” to them from the cyanobacteria, which do not. Hence, they digest other algaes and “spit out” cyanobacteria, creating that vacuum in the ecosystem that nature is known to “abhor” and inviting cyanobacteria to fill it. Also, the fecal pellets that the mussels excrete fall into the deeper, darker waters, where they are subject to bacterial degradation different from what occurs in the surface waters. So they disrupt the food chain in the lake in ways described by Dr. Joseph Makarewicz, of SUNY Brockport, and Webster Pearsall, of the New York State Department of Environmental Conservation.
Third, we know that the delivery of macronutrients to the lake from the watershed runoff is crucial in determining how much algal and bacterial growth will occur in the lake. Phosphorus in a soluble reactive (SRP = usable) form is critical to determining the amount of vegetative growth in the lake. Nitrogen, to a lesser extent, also drives vegetative growth. But here’s the difficult part: we know far too little about in what exact chemical form and when phosphorus and nitrogen are delivered to the lake. There is some evidence that the larger and more intense storms caused by global warming are causing greater and faster delivery of nutrients to the lake during the summer months. Some widely used agricultural herbicides contain a form of phosphorus. Forms of nitrogen such as ammonia and soluble reactive phosphorus and how they interact and how they are sequestered and released by other vegetation, especially new and invasive species such as Starry stonewort, in the lake needs to be better understood in order to be able to limit cyanobacterial growth.
It should also be noted that the current levels of nutrients in Canandaigua Lake continue to be low, causing the lake to be classed as Oligotrophic (low nutrient, little vegetative growth). The enigma is how low nutrient lakes like Canandaigua and Skaneateles can be supporting substantial blooms of cyanobacteria while maintaining their Oligotrophic classifications.
Now we have professional scientists from Global Aquatic Research LLC working for the Canandaigua Lake Watershed Association and assisted by citizen scientists, scientists at the Finger Lakes Institute at Hobart and William Smith Colleges, scientists associated with the Finger Lakes Community College and four NYSDEC scientists dedicated through the “Hub” to research the same problem: what causes large blooms of cyanobacteria in the Finger Lakes? We hope that their collaboration will yield positive results, suggestions for remediation and await them with concern.
Stephen Lewandowski of Canandaigua is a long-time observer of the Canandaigua Lake and its watershed.