Our fellows, Krystian Gombosi and Eden Alemayehu, spent their summer piloting an improved cyanobacteria monitoring protocol in the watershed. Developed by University of New Hampshire researcher Nancy Leland and the US Environmental Protection Agency as part of the Cyanobacteria Monitoring Collaborative (CMC), this new protocol --when fully implemented--will mean that MyRWA and municipal partners will be able to more accurately let you know if and when there are harmful algal blooms on the river. (This work is funded in part by the Massachusetts Department of Environmental Protection.)
Our fellows spent countless hours out on the water collecting samples and then analyzing them at our office lab. Read on to learn more about why we monitor cyanobacteria and what this new protocol means for our work!
Krystian Gombosi (left) and Eden Alemayehu (right) out in the watershed collecting water samples for analysis.
What are cyanobacteria?
Cyanobacteria are species of microscopic blue-green algae that can live in freshwater, saltwater, or both! They multiply quickly in warm, nutrient rich environments, which can lead to the formation of algal blooms.
Why monitor cyanobacteria?
Certain species of cyanobacteria produce liver toxins and neurotoxins that can be harmful to people and animals. If we can assess the type(s) of cyanobacteria present and predict cyanobacteria toxin levels in the watershed, we can inform people about the safety of swimming in water bodies.
Previous cyanobacteria monitoring:
Collecting a water sample (left). Fluorometry in action (right).
In the past, we have monitored cyanobacteria using solely fluorometry as a screening tool. Fluorometers measure the amount of phycocyanin pigment present in the sample as a proxy for cyanobacteria biomass. While fluorometry offers a quick assessment of cyanobacteria concentration, it does not provide information about the types of cyanobacteria in the sample and how much of each type is present.
New protocol:
The new protocol that Krystian and Eden performed is a semi-quantitative method that involves a device called the Pocket ZAPPR™. After collecting water samples using the three techniques outlined below, the Pocket ZAPPR™ concentrates the bloom forming cyanobacteria (BFC) to simulate a cyanobacteria bloom. The final BFC sample can then be skimmed off the surface of the device and examined under the microscope for identification of cyanobacteria type.
Three sampling methods: 1) Integrated tube sampler (left) helps to collect a representative cross section of the water body and all cyanobacteria present. 2) <50 micron net filter (center) filters out bloom-forming cyanobacteria from a water sample. 3) Net plankton tow (right) consists of a 53 micron net that traps bloom-forming cyanobacteria (BFC) and creates a highly concentrated BFC solution via towing action.
Putting it all together:
Cyanobacteria concentrated on the Pocket ZAPPR™
Using the Pocket ZAPPR™ and microscope, Eden and Krystian were able to identify which cyanobacteria genus was dominant in the sample. Combined with the information from fluorometry on overall cyanobacteria concentration and with previous research findings on how likely certain bacteria populations are to produce the cyanotoxin microcystin, this allows us to predict how much toxin is in our water bodies!
Spy Pond: A case study
In July and August, Spy Pond exhibited signs of large cyanobacteria populations. The water turned green and more opaque. So Eden and Krystian turned these new tools toward Spy Pond.
Spy Pond during a cyanobacteria bloom
This graph shows the results of fluorometry analysis over this period, with Upper Mystic Lake and Wedge Pond included for comparison:
You can see that there is clear evidence of elevated levels of cyanobacteria in the water at Spy Pond over this period. But what does that tell us about probable levels of the toxin microcystin in the water?
This is where the background research from the University of New Hampshire comes in. Based on extensive toxin testing, UNH researchers developed relationships between phycocyanin concentrations and microcystin toxin in lakes dominated by specific genera of cyanobacteria. (For more information, see Leland et al. 2019)
And it turns out that over the first three sampling events, Spy Pond was dominated by the genus Microcystis. The UNH regressions told us that the toxin levels were likely below the Mass Department of Public Health guidelines for posting health advisories by a factor of 5 or so. Later lab tests confirmed this.
Microscope image showing cyanobacteria in a Spy Pond sample in July. Mycrocystis cyanobacteria are the round, clumpy structures. The long threads are the genus Dolichospermum.
By the August 9 sampling date, the population had shifted to one dominated almost completely by the genus Dolichospermum. Even though there was more cyanobacteria in the water, it was dominated by a type of cyanobacteria that is much less likely to produce the dangerous microcystin toxin.
What we don’t know
While this is much more fine-grained knowledge of conditions that we had available in the past, there is still a lot we don’t know, and as we continue to gather more data and knowledge, we will share results with municipalities in a way that allows water managers to make more informed decisions.
One area that is not well studied yet is how likely toxins other than the microcystin toxin are likely to be present when the Dolichospermum type dominates a bloom. It’s known that these cyanobacteria produce anatoxins, but these are less well studied. It may be that the best course of action is to err on the side of caution and to declare conditions such as those that existed on August 9 as potentially of public health concern and sufficient to call for lab testing for toxins.
Conclusions
Overall, this new technique allows us to go from things that are relatively easy and cheap to measure (phycocyanin, species composition) to conclusions about things that are hard and expensive to measure (toxin concentrations). We could not have gotten as far as we did this summer without our wonderful, careful intern scientists.
Thank you Krystian and Eden for all of your hard work implementing this new cyanobacteria monitoring protocol for the first time in our watershed!
