The 2024 harmful algal bloom (HAB) season in the Great Lakes is in full swing – but long before the bloom began, scientists at NOAA GLERL and the Cooperative Institute for Great Lakes Research (CIGLR) had already been preparing for this annual phenomenon for months.

HABs in the Great Lakes occur when algae grow rapidly, forming dense scums and water discoloration. Some blooms can produce neurotoxins, liver toxins, or skin irritants and can be very dangerous to come into contact with. These blooms can contaminate drinking water, harm swimmers and pets in areas where toxins are concentrated, and pose a severe nuisance to recreational and commercial boating and fishing. The decomposition of biomass from HABs can also lead to hypoxia, the occurrence of low or depleted oxygen levels in a water body. Hypoxia is common in Lake Erie’s central basin and can lead to fish kills and pose threats to the drinking water treatment process.

The NOAA Great Lakes HABs and Hypoxia program is a collaborative effort between GLERL and CIGLR scientists. This integrative research approach includes using various observing systems, weekly monitoring cruises, and advanced genetic techniques to understand the long and short-term seasonal dynamics of HABs and hypoxia. The data collected are used to inform forecast models used by key Great Lakes stakeholder groups, such as drinking water managers and fisheries managers. 

GLERL and CIGLR’s comprehensive monitoring program in Lake Erie and Saginaw Bay (Lake Huron) is a core element of our ongoing HAB research. Field samples are collected weekly at eight sampling sites across western Lake Erie and biweekly at ten sites in Saginaw Bay. Buoys also collect data continuously throughout the season. Planning and conducting this monitoring work is no small task and calls for all hands on deck both in the field and in the laboratory.

Behind the scenes, before the HAB

Preparations for the 2024 HAB season began last December, when the HAB team began its intensive cleaning process in the lab. In order for the team to accurately analyze lakewater samples starting in the spring, their lab equipment needs to be extremely clean – even cleaner than it comes from the manufacturer. Bottles, vials, filters, and tubes all need to be washed with acid to ensure that no residue will contaminate the water samples brought back from the field. Throughout this past winter and spring, the team was responsible for prepping and cleaning roughly 5,350 individual pieces of lab equipment!

Winter and early spring are also the time for calibrating the high-tech equipment that GLERL and CIGLR use to monitor HABs in the field. A conductivity, temperature, depth device, or CTD, is one of these primary pieces of equipment. A CTD’s primary function is to detect how the conductivity and temperature of the water column changes relative to depth. Conductivity is a measure of how well a solution conducts electricity and it is directly related to salinity. Even though the Great Lakes are freshwater, the salinity component of a CTD still helps us study the water chemistry of the lake. Sensors for photosynthetically active radiation (PAR) and dissolved oxygen are also mounted to our CTD instruments, so that light and oxygen levels in the water can also be measured.

Another key instrument that needs pre-season calibration is the FluoroProbe. Out in the field, the FluoroProbe helps scientists look at how different groups of phytoplankton – the microscopic organisms that make up the algal blooms – are distributed vertically throughout the water column and at different locations in the lake. Back at the lab, the FluoroProbe is used again on water samples from known depths in the lake to double check that the field measurements are accurate.

Ramping up for HAB season with weekly cruises

Once the laboratory is ready and the equipment is calibrated, the HAB crew is ready to begin their weekly monitoring cruises to collect water samples. Cruises began in late April of this year, and are typically conducted through October, depending on the duration of the bloom. With this timeframe, scientists can monitor the water quality before the bloom begins, and then track how its size and toxicity changes throughout the summer. For the 2024 season, 55 HAB-related research cruises are planned, 22 of which are specific to weekly monitoring of the Lake Erie HAB. 

Planning the logistics for each cruise is no small feat. Each weekly monitoring cruise on Lake Erie requires ten people – one boat captain, two field crew members, and seven lab crew members. Cruises are extremely weather-dependent, so day-to-day plans have to remain extremely flexible in order to ensure the crew’s safety as well as the quality of the samples and data collected. A typical cruise day can involve early mornings and late evenings, especially on longer trips like the outer bay stations of Saginaw Bay. The main goals of a weekly sampling cruise involve collecting water samples to bring back to the lab and collecting data with our instrumentation, like the CTD and FluoroProbe.

Once the field crew arrives back at GLERL’s Ann Arbor facility, they immediately pull the data from the CTD and FluoroProbe, and clean all of the equipment for the next cruise. Then, the lab work begins to preserve and analyze that day’s new water samples. Seven people are required for the tasks of dividing up the samples, processing them for all the different parameters that will eventually be analyzed, and either preserving them or starting to analyze them. In total, the water collected on each cruise is analyzed for 30 different parameters, including measurements like turbidity, colored dissolved organic matter, total suspended matter, and microcystins. Photosynthetic pigments, like chlorophyll a and phycocyanin, are extracted and ready to report within days of collection.

One of the most important parameters the crew measures is the water’s concentration of microcystin, the dominant algal toxin in Lake Erie HABs. This measurement tells us how toxic the bloom is at the location the sample was collected, and allows us to track how the bloom changes throughout the season. Certain measurements of organic carbon in the samples also have to be taken right away, as this aspect of the water’s chemistry can’t be preserved in storage. New data from these cruises are available weekly on NOAA GLERL’s website.

After the higher-priority measurements are done, the HABs team stores the water for more analyses later on. One example is the quantity and variety of phosphorus in the water, which is important for researching the formation of HABs. But because phosphorus is time- and labor-intensive to analyze and is able to be stored, the lab crew will actually freeze these water samples and then measure their phosphorus levels the following winter.

A variety of research approaches

While weekly sampling is a vital aspect of GLERL and CIGLR’s HAB research, it goes hand-in-hand with an integrated suite of several other methods. Together, all of these approaches support NOAA’s Lake Erie HAB Forecast and help us gain a more comprehensive understanding of HAB dynamics.

• The Environmental Sample Processor, or ESP is a “lab in a can” that’s designed for autonomous deployment, meaning it can function on its own without human help once deployed. It collects water samples, measures microcystin, and sends the data back to scientists in near-real time. This toxicity data produced by ESPs helps provide water managers with more precise bloom location, projected direction, intensity, and toxicity.

• Remote sensing with hyperspectral cameras allows scientists to study what types of algae are in harmful algal blooms. Hyperspectral cameras capture more bands of discrete wavelengths than normal cameras. To conduct this research, a small plane equipped with the camera is flown over the bloom area.

• Autonomous underwater vehicles (AUVs) and autonomous surface vehicles (ASVs) are useful research tools that can collect high-quality data more efficiently and cost-effectively than scientists taking samples from a ship or along the shore. These vehicles are often equipped with a smaller, more mobile version of the ESP in order to track and analyze the toxicity of the bloom.

• ‘Omics, a growing science and technology focus area, employs fields such as metagenomics, metatranscriptomics, and proteomics to examine genetic material (DNA, RNA and proteins) from an array of species. ‘Omics data has become increasingly valuable in understanding and addressing issues related to Great Lakes HABs, including factors influencing the production of the microcystin toxin.

• Buoys with sensors that measure physical and chemical parameters in the lake provide a continuous source of real-time HAB data throughout the season. Data is available on NOAA GLERL’s website for Lake Erie and Saginaw Bay.

For more information on NOAA GLERL and CIGLR’s HAB research, visit our HABs and Hypoxia page.