This assessment was based primarily upon what was known of green and filamentous algae, both common and abundant in most lakes. This year water testing through CSLAP detected high levels of blue-green algae as well. Blue-green algae grows in warm, slow moving, shallow water rich in nutrients, and becomes visible only when present in large numbers. Although not always harmful, some types of blue-green algae can produce toxins.
It is probable that blue-green algae (cyanobacteria) has always been in Putnam Lake. However, it was never actually identified before now or isolated as a separate problem apart from the other algae groups. This year residents could easily see conditions had intensified simply because the streaks and pea soup-like signs were visible everywhere on the lake. Thick scum affected all areas including the beaches and southern deep end where water usually remained clear. These cyanobacterial blooms occur when algae that normally are present grow excessively.
The first water samples taken through CSLAP (and analyzed by the DEC) on July 8th indicated these concentrations were blue-green algae and producing toxins. CSLAP samples taken in open water (1.5 meters below the surface) where concentrations did not appear, detected less amounts but were none-the-less also present.
Anticipating a repeat of the usual weed situation, Allied Biological Inc. was contracted to do a weed survey this August when summer weeds were expected to be at their peak. A survey (and map) would be needed to indentify the concentrations, location and type of weeds present before any remediation could be planned. However, Allied’s biologists quickly discovered that few aquatic weeds even existed. It appeared the algae had also inhibited the growth of aquatic weeds in the lake. A first time occurrence, this would be another factor to indicate how severe the blue-green algae situation was for the lake’s ecology.
Water quality analysis from the DEC, Allied Bilogical Inc. and the Putnam County Health Department have all independently confirmed blue-green algae amounts and high toxin levels existed. Putnam Lake is now listed on the NYDEC website for Harmful Algae Blooms (HAB) at: http://www.dec.ny.gov/chemical/83310.html Although the Health Department does not normally test for algae at the beaches (monthly tests are for fecal coliform only), established levels reported elsewhere in the lake (via the DEC) coupled with their own visual inspections brought the beaches to a close. The Health Department sampling protocol for blue-green algae was then initiated and the beaches were not reopened in August.
In addition to these organizations providing information, the Park Advisory Board has had ongoing discussions this summer with Ms. Aris Efting, a research scientist working through Bard College. Ms. Efting has taken samples at Putnam Lake and is working specifically on blue-green algae and the triggers that release the toxins. Her research has brought her all over the country to study this phenomenon. She has graciously offered to forward her findings and remain available for information.
Harmful blue-green algae blooms can cause health effects when people and animals come in contact with them. Symptoms can include nausea, vomiting, diarrhea, skin rashes, throat irritation, asthma-like reactions or breathing difficulties. Blue-green algae can also produce toxins that affect the liver and nervous system when consumed in sufficient quantities.
We may never know if toxins were present in the lake before now or if they were triggered this year by the high concentrations. Either way, we do know that this particular type of algae is well established for future cycles. We suspect the expediential growth this year was due to the following converging factors:
1. The Severe Winter Draw-Down Last Winter. The drawdown gave spring weeds a major push. Typically, this action kills the roots of exposed plants along the shoreline. However, Curly Pondweed, the prevalent spring weed in Putnam Lake, can tolerate both low light (under ice and snow) and low temperatures. As temperatures warmed in early spring, the Curly Pondweed grew voraciously from an early start and no competition.
2. Curly Pondweed Die-off and Heavy Rains. In mid-spring as the Curly Pondweed died off, a huge surge of nutrients from all these decaying plants entered the water system at the same time heavy spring rains rushed more nutrients into the lake. Essentially we had a double-duty nutrient dose for algae to feed upon.
3. Hot Sunny Weather after the Rains. Coinciding perfectly after the Curly Pondweed die-off, we experienced a long few weeks of very hot, sunny weather that warmed the water to help the cyanobacteria reproduce. As mentioned previously, blue-green algae likes warm, shallow, slow moving water rich in minerals.
4. No Water Movement. All these negative factors were unfortunately aided by the fact water was not going over the spillway.
Before the season began, one of the AB’s initial concerns was how to deal with the excessive weeds in the lake. It now appears blue-green algal growth and the toxins they produce will shift our focus for the near future until conditions change again. Aside from the serious health considerations, these are very difficult environmental dilemmas to deal with because the algae growth depends on existing nutrients already in the lake as well those entering with each rainfall.
Our CSLAP sampling efforts have six more weeks to go, and Allied Biological is due to take their last water quality test this September. After the CSLAP and Allied reports come in at the end of the year, the Park Advisory Board will make their recommendation on a course of action for next year. Our goal is to have all plans and permits in place before spring. Fortunately the weather is starting to cool at night and the algae has begun to die off. As this happens the lake will be free once again of toxins, and we’ll have a long winter to plan for next year.