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Water Quality: Sampling Confirms Toxic Bloom

By Hilary Arens

Toxic Bloom

If you’ve ever recreated at one of Utah’s lakes or reservoirs during the late summer or early fall, you’ve probably seen areas where greenish scum was floating on the water or collecting on the shore. What you probably didn’t know was that this bright-green water is a sign of an algal bloom. These blooms are caused by a rapid increase in a type of bacteria that can produce toxins that are harmful to humans, pets, wildlife, and fish.

When the Utah County Health Department notified the Division of Water Quality (DWQ) that a dog had died after swimming in Utah Lake’s green waters over the weekend, we immediately took action to sample the water for the presence of cyanotoxins, the poisons that can sometimes be produced by the cyanobacteria in the bloom.

Although algae are a natural part of many freshwater ecosystems, under the right conditions these populations can explode to create large algal blooms. Cyanobacteria—sometimes known as blue-green algae because like algae, they have the ability to photosynthesize—can multiply when elevated levels of nutrients, warm temperatures, and calm water combine to create the perfect environment for rapid growth. Sampling is critical, because the only way to know if a cyanobacteria bloom is harmful is to test for the presence of toxins in the water.

As soon as DWQ was notified about the possible toxic bloom, we sent our scientists to the Lindon Harbor Jetty to begin sampling. We took our first samples in the early afternoon of Monday, October 6, 2014, in the area where the dog played, on the shoreline, and within the boundaries of the marina.

Before we began sampling, we performed a visual assessment to look for the telltale green color, large concentrations of algae, floating mats, and any residue along the shoreline. This helped us identify the best locations to collect samples.

We followed Standard Operating Procedures (1 MB) established by our division to ensure that the samples we collect gave us an accurate representation of the water conditions. In this case, we performed grab samples where we hold the sample bottle in our hand, tilt it, and allow it to fill below the surface of the water. We also wore protective gear, like boots and gloves, to make sure our skin didn’t come into contact with any toxins that may have been present in the water.

After we collected our samples, we put them in a cooler to keep them at the appropriate temperature. We immediately shipped the cooler to a lab in Florida that specializes in cyanotoxin testing and analysis and put in for a rush order so we could get the toxic bloom results quickly.

Last Thursday, we got the lab results back. The lab analysis looked for four cyanotoxins associated with cyanobacteria, and the tests for the sample taken north of the jetty detected microcystins at 11 micrograms per liter (ug/l), which is above the public health advisory level of 6 ug/l found in some other states.

DWQ conducted additional sampling in the lake and downstream areas, like the outlet to the Jordan River, to determine the extent of the cyanotoxin contamination. Late last Friday, we received the results from the samples we collected Wednesday. These latest results indicate that the toxin levels have dropped below the thresholds used by other states to trigger public health advisories. Good news.

We will reevaluate the toxic bloom early this week to determine if we need to do any additional monitoring. In the meantime, the Utah County Health Department is advising people to avoid swimming or boating in areas with bright-green algae growth and keep their pets out of the water.

We will continue to post updates of sampling results from the Utah Lake algal bloom on our website. If you’d like to learn more about the ways DWQ is working to reduce nutrient pollution our lake and streams, check out our state nutrient strategy. You can also read previous blogs by DWQ’s John Mackey on Holding the Line on Nutrient Pollution and Paul Krauth on when It’s Not Healthy Being Green for more information.
Sampling toxic Blooms


I’ve worked for the Utah Division of Water Quality for five and a half years in the Watershed Protection Section. My focus has been on the Jordan River Basin and now has expanded to include the Utah Lake watershed. I have a master degree in Watershed Science from Colorado State and an undergraduate degree in Biology and Environmental Science from Colby College. Outside of work, I love being on rivers, skiing, biking and taking my toddler twins where few toddlers usually go.


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