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Study Shows Novel Way to Manage Harmful Algal Blooms and Toxins in Ponds

Study Shows Novel Way to Manage Harmful Algal Blooms and Toxins in Ponds

A relatively new commercial algaecide may prove useful for controlling harmful algal blooms (HABs) in ponds and lakes. HABs are typically made up of photosynthetic bacteria called cyanobacteria, which can release toxins into the water. These toxins can be hazardous for aquatic life and could cause fish kills in aquaculture ponds. 

Dr. Amit Sinha, assistant professor in the Department of Aquaculture and Fisheries at the University of Arkansas at Pine Bluff, and colleagues studied a newer algaecide called PAK® 27. They looked at how that compound affects cyanobacterial blooms in ponds that have excessive amounts of nutrients, termed hypereutrophic.

PAK® 27 is made of sodium carbonate peroxyhydrate (SCP), a dry granulated compound that releases hydrogen peroxide (H2O2) when it mixes with water. H2O2 can kill cyanobacteria, and at the same time can break down toxins that may be released as these organisms die. Other chemical treatments that are commonly used, such as herbicides and copper sulfate, kill cyanobacteria but do not break down the toxins. 

Dr. Sinha wanted to determine how much SCP is needed to kill off cyanobacteria while allowing green algae, diatoms, and zooplankton to survive since these organisms are more palatable for fish. “Our goal was to remove the cyanobacteria, but we also needed to determine how much SCP was too much,” Sinha said. “We didn’t want to harm the food base for the fish living in the ponds,” he added.

They applied SCP to four aquaculture ponds to achieve H2O concentrations of 2.5 mg/L in two ponds and 4.0 mg/L in the other two. They also had 2 control ponds where no SCP was added. They sampled the ponds for 6 weeks to look at how the algal and zooplankton communities changed over time.

Picture: Student collects water sample from aquaculture pond.

Student collects water sample from aquaculture pond.

At the end of the study, they found both cyanobacteria abundance and microcystin, a common toxin produced by many cyanobacteria, had decreased in the SCP treated ponds relative to the control. Additionally, edible green algae and diatoms increased in the ponds that received the lower concentration of H2O2, likely due to increased nutrient availability. However, in the higher SCP treated ponds, H2O2 reduced all forms of phytoplankton, not just the cyanobacteria.

Interestingly, application of SCP controlled cyanobacterial blooms for up to 5 weeks, even though the chemical itself degraded rapidly. “Within 4 to 5 days H2O2 disappeared, leaving no long-term traces in the environment, which is great,” Sinha said. “The SCP was not only effective at removing the cyanobacteria but also the toxin” he added.

In this study, Planktothrix sp. was the dominant cyanobacteria. They suggest that future work should be conducted to determine if SCP has similar effects on other types of cyanobacteria such as Microcystis and Anabaena sp.

This research was funded by the AWRC – USGS 104B grant program and was published in the 2018 edition of the Arkansas Bulletin of Water Research and was also published in the peer-reviewed Journal ‘Science of the Total Environment (Sinha et al., 2018, 637–638 524–537)’.

About Arkansas Water Resources Center

Founded in 1964, the AWRC engages with students by supporting student research and providing employment opportunities. The AWRC also operates a water quality laboratory where water samples are analyzed for researchers, students, and the public.

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The mission of the AWRC is three-fold:

  1. to support water research in Arkansas
  2. to train future water scientists and engineers
  3. to share information with stakeholders.

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The AWRC Team

Dr. Brian E. Haggard
AWRC Director
479-575-2879, haggard@uark.edu