Blue Green Algae (Cyanobacteria) in Our Lakes
A recent article in the Danbury News Times about the issues facing Candlewood Lake from blue-green algae had us thinking about the blue-green algae sampled at West Hill Pond last summer.
Blue green algae – also known as Cyanobacteria – has become a visible concern in recent years to lake managers throughout the world. Cyanobacteria are prokaryotes rich in proteins that obtain their energy via photosynthesis. Their high protein makes them less attractive to the Zooplankton grazers found in freshwater lakes that prefer the cellulose rich phytoplankton (Eukaryotes). This lack of predation on Cyanobacteria gives it a selective advantage over other phytoplankton. Today, Cyanobacteria grabs headlines not because of its creating life-enabling oxygen, but for its more insidious side. Certain Cyanobacteria are the source of cyanotoxins implicated in neurodegenerative diseases such as Lou Gehrig’s, Alzheimer’s and Parkinson’s disease. Cyanotoxins are a much broader category than just neurotoxins, and include hepatotoxins, endotoxins and cytotoxins as well. Managing the lake to limit the possibilities for large Cyanobacteria blooms is one of our highest priorities.
Origins of Cyanobacteria
Cyanobacteria have inhabited the earth for over 2.5 billion years. Their arrival coincides with the Great Oxygen Event (catastrophe) since of course Blue Green algae can photosynthesize, producing oxygen. So while they are the reason earth has an atmosphere and we are able to breathe, when they first emerged all bacteria were obligate anaerobes and the oxygen a deadly gas which caused their demise.
Since cyanobacteria thrive in waters with excess nutrients – like those of most freshwater lakes in New England – they are interfering with activities like swimming and fishing, once thought rites of summer. Connecticut DEEP and Department of Health have established guidelines for shutting down public beaches when concentrations are high … and beaches across CT have been impacted in recent summers.
Nutrients Fuel Cyanobacteria Growth
Nutrients – especially phosphorus – are found in fertilizers, soils, atmospheric deposition and septics. These are commonly transported by stormwater flowing through a lakes watershed either over the surface or by recharging groundwater. Phosphorus is then transported into lakes bound with soils and is released during late summer when the lake bottoms become anoxic (no oxygen). Lake bottom dwelling bacteria prefer aerobic respiration, but under anaerobic conditions common in mid summer through fall, selectively reduce iron. It is oxidized Ferric iron complexes which give sediments its Phosphorus binding capacity. When Ferric Iron complexes are reduced to Ferrous iron, phosphorus is released into the lake waters as soluble reactive phosphorus. What was previously limiting growth of photosynthetic algae and Cyanobacteria, is now available, and the result is the blooming of these plankton. The vast population growth of photosynthetic algae and bacteria are the reason for reduction in water clarity (secchi disk readings) during the late summer and early fall. The conditions are ripe for Cyanobacteria from mid-summer to late fall.
Impact on Recreational Resources
Many lakes and beaches were closed during the summer of 2015 on account of the presence of Cyanobacteria. On Candlewood Lake, the three town beaches — Sherman, New Fairfield and Brookfield — were all closed due to the presence of cyanobacteria. The beaches at Squantz Pond State Park were closed. As was the beach at Lake Pocotopaug, and many other Lakes in CT and New England. Closing the beaches is a pretty serious step for a health department to take, and not something we’ve ever experienced at West Hill Pond. With fast action, closing the Brodie Park Beach, Laurel Acres Beach, or beaches of the Scout Camps is something that we hope won’t happen for a long time. While summer of 2015 was the first year we identified Cyanobacteria in our sampling, hopefully it doesn’t progress to where the guidelines require closing the beaches.
Is it possible to manage Cyanobacteria to maintain a resource for recreation? Limiting the food (phosphorus) is the generally accepted best approach. Keeping the phosphorus in the landscape bound to iron by requiring limited or very careful development (low impact site develop – LISD) is the generally accepted approach. In fact, the Town of New Hartford identified this approach in its Plan for Conservation and Development. Fast action in adopting the plan’s number one recommendation has been recognized by experts such as Limnologist George Knoecklein PhD as the best first step to stave off future Cyanobacteria blooms. Getting the Town to take that step is critical.
Recommendation from Dr. George Knoecklein’s West Hill Pond Report for 2015
West Hill Pond drainage basin should have LID incorporated into all aspects of flowage and landscaping over the whole of the watershed.
- Modify and amend any and all existing regulations to include special lake-specific protection language that accounts for the sensitivity of West Hill Pond.
- All future development, and all existing development, in the drainage basin should be Hydrologically Transparent. West Hill Pond is extremely vulnerable to nutrient and sediment inputs from its tiny watershed.
There are other ways to manage Cyanobacteria in reservoirs and lakes. A recent (2015) scholarly article on Cyanobacteria in Reservoirs by Dr. Robert Kortmann of Ecosystem Consulting suggests alternatives for managing Cyanobacteria in reservoirs. A management approach may involve combining several different strategies, but should always include watershed management to limit the watershed’s contribution of phosphorus. Some of the other strategies include: oxygenation, enhanced grazing, managing nitrate and nitrification, season of use (use earlier – Spring and early Summer – before the bacteria blooms), increasing competitive update. Use of Alum or Ferric salts to precipitate phosphorus is a common phosphorus removal technique in wastewater treatment plants, where the process is easy to control. In open lakes the process is more challenging to manage and removal of phosphorus is less efficient. “Back of the envelope” cost estimates have ranged from a half million to a million dollars.