Yixing/Lake Tai – Heavy-bloom Lake Treatment with Lake Guard™ Blue
Place: People’s Republic of China, Jiangsu province, Yixing
Date: Aug. 6 – Aug. 21, 2019
The purpose of the pilot was to demonstrate the advantages of the use of Lake Guard™ Blue as an economic, safe and environmental mean to control harmful algal blooms, even under the harshest conditions.
The pilot was conducted in an old fishpond (7,100 m2), in the vicinity of Lake Tai, across a similarly infested ‘corridor’ that is linking a waterway between the city of Yixing and Lake Tai. Ongoing efforts to deal with the loads of bacteria streaming through this ‘corridor’ both from the lake as well as from the city – have been fruitless.
The fishpond, which was infested with high levels of cyanobacteria was prescribed with an aggressive dose in order to achieve an immediate result in terms of reducing bloom levels.
Description of Application:
The fishpond was dosed on Aug. 7th and on Aug. 8th 2019.
The particles of the Lake Guard™ Blue traveled with the currents and the wind across the pond, interacting with the phytoplankton inhibiting the water surface. Each application time lasted <5 min.
By the afternoon of Aug. 8, ~6h after the second application, all water parameters have indicated a complete collapse of the bloom and the rehabilitation of the pond.
Two weeks later, the pond has shown a tremendous recovery with beneficial-species outcompeting toxic cyanobacteria, keeping the water, naturally, in a very good condition.
Throughout the pilot period quantitative measurements were made by YSI ProDSS probe, measuring Dissolved Oxygen, pH, Chlorophyll, and Phycocyanin (PC). Chlorophyll measurements serve as a proxy for total algal biomass in the water. PC levels serve as a direct proxy to total cyanobacteria biomass in the water.
At the same time, qualitative assessments were made visually.
- Change in Cyanobacterial and Total Algal Levels (Fig. 1A-B):
Prior to treatment (at time 0), the pond had a PC value of 21.84 µg/l and Chl values of 22.32 µg/l. 48h into the pilot, PC concentration in the pond dropped to 1.72 µg/l (-93% from time 0) and Chl concentration (at the time, made of primarily of toxic cyanoabcterial cells) dropped to 9.39 µg/l (-58% from time 0).
Two weeks later, by Aug. 20 , PC values were stagnant at a low level of 2.04 µg/l while Chl concentration increased to 45.34 µg/l (completing a 482% increase from its post treatment lowest point).
- Change in pH (Fig 2A):
Concurrent to the drop in bloom levels, corresponding changes were measured in the water’s pH and Dissolved Oxygen (DO) which are directly influenced by the intensity of the bloom – and the quality of the treatment.
The dramatic reduction in photosynthetic and respiratory activities (consuming and releasing CO2, respectively) had an immediate and direct influence on pH, which dropped from 9.05 to 8.29 within 48h. By Aug. 20, two weeks later, pH completed a steep drop to a healthy level of 7.43.
- Change in Dissolved Oxygen (“DO”) (Fig. 2B)
Concurrent to the decline in pigment content in the water (chlorophyll and phycocyanin), a corresponding DO decrease was measured. This is a result of the decreasing photosynthetic activity (that generates O2) and the rise of bacterial population that degrade dead cells (and consume O2). With the removal of dead cyanobacterial cells from the environment and the rise of green-algae (and with it – photosynthetic activity), DO levels are seen on the rise once again.
A severe bloom of predominantly toxic cyanobacterial species was treated with Lake Guard™ Blue in an old fishpond.
The simple treatment “surgically” removed the dominant species and enabled other nontoxic phytoplankton species to thrive in the ecological niche. This happened through a “Killing the Winner” mechanism that enables natural competitors to occupy the ecological niche and contribute to the lasting effect of the treatment. The ability to almost-selectively treat the toxic species is attributed to the higher sensitivity of cyanobacterial species to the oxidative stress that is triggered by the treatment.
Chl values represent the concentration of all photosynthetic organisms (cyanoabcteria as well as non-toxic green alage). PC values represent only cyanobacterial concentrations.
The Chl/PC ratio (Fig. 3) serves as an excellent proxy of the fraction of toxic cyanobacteria compared with other algae in the water body. The lower it is – the greater is the abundance of toxic cyanobacteria. Under healthy conditions, this ratio should be high – indicating that non-toxic algae dominate the water body and can inhibit the growth of toxic cyanobacteria. A low ratio indicates that the toxic cyanobacteria took over and inhibits the growth of the ‘good’ species.
It serves to evaluate the pond’s “Resistance Factor” to cyanobacterial blooms.
Over the 2-weeks’ course of the pilot, the Chl/PC ratio in the pond improved by 2,570%!
The significance of the ‘Resistance Factor’ to water management and its impact on the the waterbody’s health clearely correpond with the situation on the ground, as it was clear to the naked eye thorughout the pilot (Fig. 4).
Fig. 3. Chlorophyll to phycocyanin ratio. This value expresses the population variation, or the pond’s ‘Resistance Factor’ to toxic blooms, whereas a higher value represents more nontoxic green algae to cyanobacteria.
Fig. 4. Visual changes in the water quality of the treated pond throughout the period of the pilot.
It is further worth noting the much-worsned situation in the waterway, along the treated pond, serving as a visual control throughout the pilot period.
These results are in agreement with an ongoing work done in Israel and the US over 1,000s of lakes ranging from 1-150 ha.