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Bioremediation Methods for Reducing Cyanobacteria Colonies in Morningside Pond

HAB you ever noticed the green layers of matter in places like ponds, lakes and brooks? In many cases those thick unbreathable layers are a common characteristic of what we call eutrophication! Harmful algal blooms (HABs) which often spur the eutrophication or the rapid depletion of dissolved oxygen in water. That rapid depletion is caused by population explosions of microorganisms like cyanobacteria. In fact 90% of HABs are caused by cyanobacteria, not actual algae. This study focuses on one pond in particular located in Morningside Park, and the pond was particular indeed.


Amber Siurano, Sean Hamilton, Ulysses Olsen


Diana Mendez, Destiny Iheakanwa

Project Period:

2023 Summer



Cyanobacteria are tiny organisms that have existed for billions of years. They are most commonly known for their role in oxidizing the atmosphere over 2 billion years ago which made it possible for the Earth to sustain human life. However, they were identified to be one of the main sources of harmful algal blooms (HABs) in freshwater bodies and a producer of a toxin that can negatively target the skin, liver and brain. There are several techniques that can be used to reduce their populations in water, two of which are aeration and the addition of biochar, a charcoal-like material made from carefully burned organic matter. Aeration introduces air bubbles at the bottom of the tank which makes the body of water less favorable for cyanobacteria by decreasing the pH and nutrient availability as well as disrupting their migration patterns. Alternatively, biochar—which is made from pine wood in this case—works by making the nutrients adhere to its surface in a process known as adsorption. As a result, the nutrients are no longer bioavailable to the cyanobacteria. With this knowledge, eight identical 1L tanks were set up with water taken from Morningside pond, a pond in Harlem, New York with an active cyanobacteria-induced HAB. These tanks were inoculated with a known freshwater strain of cyanobacteria (2973) and allowed to grow under constant light exposure before the respective treatments were applied—two received the aeration treatment, two received a “low” biochar treatment, two received the “high” biochar treatment and two received no treatment. At the end of the experiment, the data was analyzed using Microsoft Excel and the tanks underwent a colorimetry analysis. It was found that dissolved oxygen dropped across the board and aeration worked more rapidly to prevent cyanobacteria colonies from forming while the biochar tanks had fewer nutrients in general. With that being said, biochar is still a promising approach to mitigate cyanobacterial growth especially because it is cost effective and applicable on larger scales.

This page was originally developed by BioBus Summer 2021 Jr. Scientist William Rhee.

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