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Warmer Waters Increase Harmful Algal Blooms

HABs (Harmful Algal Blooms) are dangerous and harmful to all organisms that are near any water bodies. HABs are Algal that usually grow rapidly around the spring or summer on warm waters which can cause multiple problems. HABs have been occurring before humans walked the Earth which makes this a normal process. However, Climate Change has become a factor increasing Harmful Algal Blooming throughout the years.

Harmful Algal Blooms  need to have favorable conditions in order to grow. They would need to have a huge abundance of nutrients in the water (Nitrogen and Phosphorus). Warmer than usual water temperature and calm still weather. These conditions would offer Algal to Bloom and start to become harmful. HABs consist of Algae and mostly Cyanobacteria which reside on the surface of the water. There are two types of HABs: one type can produce toxins which can sicken and/or cause death to anything that is directly or indirectly affected by it. Physical touch or being close to toxic HABs is how one can get affected by it. The other type of HABs are non-toxins that are so dense they prevent sunlight from reaching underwater plants in bodies of water. The non-toxins consume oxygen within the water when decomposing in a process causing “Dead Zones”. These “Dead zones” lead to little life underwater since there is no oxygen and sunlight for organisms to live. EPA has provided useful information regarding HABs and their increase throughout the years which proves Climate Change has played a factor.

Using Remote Sensing from satellites in orbit one can detect Ch-a concentrations on the surface of the water. Landsat and Sentinel Satellites are used to detect the wavelengths emitted by Chlorophyll-a. Since Algae have chloroplasts in them the Ch-a absorb usually red light and emits out green light which can be remotely sensed by the Satellites.  In other words, Ch-a usually absorbs 500-700nm which can be sensed when a satellite is over a body of water. The limitation with remote sensing with satellites in this case is wind causing certain algae that are on the surface of the water to go underwater; not able to be detected. The EPA measures Ch-a concentration in the water as mg/L and has shown an increasing trend over the years.

The Cause of the increase of Ch-a concentration is due to Climate Change. People who live near bodies of water provide Nitrogen and Phosphorus content through urban runoff due to people using fertilizers on their lawns causing nitrogen and phosphorus to make their way into the body of water nearby. The increase of global temperature caused by Climate Change provides a bigger window for HABs to bloom. The longer summers and warmer waters allow HABs to absorb more sunlight making the water warmer causing negative feedback. Climate Change leads to alternating droughts and storms changes (rainfall patterns) in certain areas which can cause nutrient run off giving HABs favorable conditions to thrive. The increase of carbon dioxide in the air and water helps algae to grow rapidly. These methods were mentioned by the EPA on how it can increase HABs production.

In conclusion, HABs have been occurring before humans existed, but is now increasing because of Climate Change. Algal Blooms ruin aquatic ecosystems in bodies of water such as lakes that prevent us from swimming near them. These “Dead zones” that HABs cause through decomposing processes ruin the aquatic sea life in these lakes since they need oxygen to breathe and sunlight for the aquatic plants to undergo photosynthesis. The toxins the algal bloom produce are dangerous since it can contaminate our drinking water causing immense damage to our way of life. The few things one can do is to reduce nutrient overloading if one lives any water body and to mitigate the global warming of our water bodies.


Image: https://cdn.britannica.com/47/178347-050-F49F2A4E/algae-fish-Lake-Erie-bloom-shore-line-Aug-19-2011.jpg


  1. EPA, Environmental Protection Agency, https://www.epa.gov/nutrientpollution/climate-change-and-harmful-algal-blooms.
  2. EPA, Environmental Protection Agency, https://edg.epa.gov/metadata/catalog/search/resource/details.page?uuid=https%3A%2F%2Fdoi.org%2F10.23719%2F1518546.
  3. Murray, Cameron, et al. “Water Quality Observations from Space: A Review of Critical Issues and Challenges.” MDPI, Multidisciplinary Digital Publishing Institute, 4 Oct. 2022, https://www.mdpi.com/2076-3298/9/10/125/xml.
  4. “Landsat 5.” Landsat 5 | U.S. Geological Survey, https://www.usgs.gov/landsat-missions/landsat-5.








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2 Responses

  1. I really did learn a lot after reading this post. I didn’t know algae blooms were so harmful. There have been many times in my life where I have witnessed algae blooms and I assumed that it was just a part of the natural ecosystem. For example, I can recall many times where I could stroll through
    Central Park on a hot summer’s day and see a pond covered in algae. I thought this was a natural process until I did some research. I found out that these algae blooms were actually harmful to life in the pond. The algae blooms that I saw there often covered the entirety of the pond. I would dip my hand in and move it round just to see the water that was underneath. These blooms now make sense considering the location of the ponds. Being in a city like NYC, there must be so many people coming by and polluting it. Furthermore, the rising heat from global warming and the concrete and glass reflective buildings of NYC makes summer days even hotter. Thus, the ponds get even hotter. The ponds with stagnant water and encountered pollution and a heat rise now vividly explain what I was seeing as a child. As you said, a satellite can easily pick up the algae blooms in the water there. Central Park is also very developed. Thus, fertilizer runoff can also contribute in giving algae blooms the nitrogen and phosphorus that it needs to survive. Ending algae blooms will be a matter of stopping climate change. I believe that is the main cause of algae blooms. Humans can try to enforce stricter laws against people who negligently pollute the pond waters. Also, fertilizers need to also stop being used in Central Park. Overall, this is not a problem that can go away easily since the cause is on a much grander scale.

  2. Not many people even consider algae to be a harmful plant/microorganism, and this really shows the harmful effect if it does grow at an exponential rate. This really connected with and understood this as I did a research topic into algae about their pros and cons. With the earth warming up and an increase of Carbon emissions, it’s a perfect environment for these to grow in unsuspecting rivers or lakes. Plus I like it when you mention that people especially, farmers and landowners, wash down gray water which they think might have a minimal impact, but they can increase the harmful algae bloom. There are some merits to algae. One significant benefit of using algae as they are a microorganism that can be used as biofuel is that it will consume carbon dioxide in a massive scale, which means that we will be reducing a main contributor to the problems of climate change. Naturally, algae grow fast, where they only need sunlight, water and carbon dioxide to thrive. Also, algae can be produced using any type of water from waste to seawater. But overall this article highlight the potential danger of algae as our climate start to become warmer and if these algae are left uncheck.

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