WINDOW ON CLEAR LAKE
Part 2- Fixing Clear Lake
by Jim Steele
The days are getting longer; the sun’s angle is higher in the sky, and sunlight will penetrate the water rather than be reflected off the surface. When the length of the day and light penetration are long enough, a photo compensation point is reached, and single-celled algae will grow and reproduce. That is a good thing for aquatic wildlife. The base of the food chain will feed zooplankton, which are food for small aquatic insects, which feed small fish, and so forth up to larger fish and a great many birds. The cycle of life will soon have the energy it needs to renew. But sometimes things go awry, and people report a cyanobacteria bloom before noticing all the beautiful birds and wildlife.
Algae and flowering plants are the primary producers of oxygen through photosynthesis and create a notable surplus needed by advanced life forms, certainly humans. Algae are technically not flowering plants but instead reproduce by cloning and other simple methods. Single-cell algae are roughly divided into two groups: the primitive forms with simple cell organization are called prokaryotes, such as blue-green algae (cyanobacteria), and those with more complex cell organization are called eukaryotes. The prokaryotes were probably the first life forms three billion years ago. The oxygen produced by these early life forms changed the atmosphere, oceans, and even lakes, making conditions favorable for the development of advanced eukaryotic species. Basically, primitive prokaryotic cyanobacteria thrive in low-oxygen environments, but the eukaryotic phytoplankton thrive in higher-oxygen environments and form the base of the food chain up through all the eukaryotic plants and wildlife.
What causes a loss of lake oxygen to favor primitive cyanobacteria and stink up the lake? Nutrients from soil erosion, fertilizing, highway organics such as oil, and roadkill wash into the lake, creating a nutrient broth. This causes algal types, aquatic rooted plants, zooplankton, insects, and aquatic wildlife to flourish at each trophic level. Is Green good, right? But the large biomass of life in the lake steadily increases during the summer, depending on nutrient availability, all of which need 24 hours of oxygen to thrive.
Oxygen saturation in the water column from daily photosynthesis and winds must last all night, or the primitive cyanobacteria can become competitive in low-oxygen [anoxic] environments. Low-oxygen-tolerant fish species can also die from anoxia and decompose. Decomposing biomass requires additional oxygen, compounding the problem. If enough plants, animals, and decaying material demand oxygen that isn’t available, a sudden mass die-off can cascade, usually just before dawn after a long night. Sometimes, residents will wake to notice cyanobacteria, fish floating, and the smell of decomposing material in what might seem like a sudden event but actually took most of the summer to develop. In the case of nutrients, an extreme level can sometimes take years to build in the lake and have this effect.
The annual dominance of cyanobacteria and accompanying fish kills was studied by major agencies and universities for several decades, most notably U.C. Davis, which published the “Causes and Control of Algal Blooms in Clear Lake [Richerson, Suchanek, Why, 1994].” This publication used data beginning in 1970 [until the report date] and recommended controlling upland sediment and rehabilitating floodplains and wetlands. It further notes that reducing phosphorus in lakebed sediments is an effective strategy to speed recovery.
A new study by U.C. Davis, under a Blue-Ribbon local panel strategy sponsored by Assemblyperson Aguiar-Curry, uses an Engineering approach to the lake. This effort focused on robotic monitoring of lake parameters and later monitored the testing of proposed fixes by outside companies. Among the studies are algae capture and removal, and microbubble and oxygen infusion techniques to temporarily reduce anoxia, thereby benefiting cyanobacteria. These methods add little to permanently balance the problem-causing nutrients in the lake.
But another test approach, more aligned with the 1994 report, locks up the recycling lake-nutrient phosphorus into pebble form using lanthanum/bentonite-clay slurry infusions onto the lakebed. This last approach promises to reduce the level of phosphorus nutrients available to the lake ecosystem. But only if the outside introduction of this nutrient to the lake is also significantly reduced.
When cyanobacteria have the low-oxygen advantage, and the exploding population takes up phosphorus in the lake, they float to the lake surface to gain a sunlight advantage and drift downwind, driven by westerly breezes toward the lower arms of the lake. Here they die and concentrate the phosphorus as a result. By treating these key areas, a significant amount of recycled phosphorus can be locked up using the lanthanum treatments. Yes, the high phosphorus levels fueling cyanobacteria blooms can be reversed.
Next is Part 3, fixing the wetlands.
