Written by Ethan Thio '22
Edited by Elana Balch '2.15
Graphics by Caroline Dai
Human activity is introducing profound, wide-reaching change to nearly every part of the biosphere. While rising sea levels and species extinctions deservedly accrue much of the media attention on the issue, many of the other devastating repercussions of human activity and climate change remain largely unknown and unaddressed. The disturbing trend of worsening algal blooms is one of these lesser-known effects, and its consequences are enormous. Algal blooms are overgrowths of microscopic photosynthetic organisms, found in most bodies of water. The primary danger of these blooms stems from the toxins these algae produce, which can affect other organisms in the water while also contaminating water when used for human purposes.
New research published in the journal Nature features the use of images captured by NASA’s Landsat 5 satellite from 1984 to 2012 to assess algal blooms in 71 lakes around the world. Researchers included lakes with differing depths, precipitation levels, and latitudes in their analysis, ensuring a diverse data set that can better eliminate potential confounding variables that may sway broader results. On average, the researchers concluded that the occurrence and intensity of algal blooms has risen since 1984. This finding is relevant, because it disproves hypotheses that growing algal blooms are functions of latitude, or simply due to new attention from researchers. The research shows that these blooms are not isolated to certain regions of the world, nor are they a problem caused by over-research. The multi-decade time span of this research illustrates how this is an intensifying problem that has existed before recent research.
It’s also important to realize that algal blooms come with serious consequences for humans. The organisms that comprise these algal blooms often produce toxins, which harm aquatic food production and contaminate drinking water supplies. These toxins can be lethal to animals and humans, a significant problem for areas that rely on lakes affected by algal blooms for their water supplies. The toxicity of blooms also diminishes recreation and tourism in these lakes, helping account for the estimated $4 billion in economic losses tied to algal blooms. In short, these blooms are dangerous, and their growth is a major cause for concern.
The EPA states that algal blooms require “sunlight, slow-moving water, and nutrients” to grow, but these are broad factors that encompass many lakes. Researchers generally agree that nutrient runoff into lakes worsens algal blooms, but the mechanisms by which other environmental conditions affect algal blooms is still under research. This study uncovered nuance in these alternative drivers of algal blooms. Across all lakes, temperature, precipitation, and fertilizer use lacked consistent correlation with intensifying algal blooms. The researchers stress that the rise in algal blooms is in many cases driven by lake-specific shifts, supporting the push towards more individualized analysis and targeted solutions to mitigate algal blooms.
The study also indicates that climate change is likely playing a role in the intensification of algal blooms. Researchers state that in the limited cases where algal bloom growth slowed, lakes were likely to have “little or no warming” (Ho 3). A major countermeasure used against algal blooms is the limiting of nutrients found in lakes. The researchers assert that warming is likely diminishing the effectiveness of these countermeasures, but do not provide a mechanism for how this occurs. Addressing these temperature shifts, by modulating efforts to combat algal blooms in relation to rising temperatures and other lake-specific conditions, will be paramount in halting the growth of algal blooms.
Algal blooms are a dangerous, relatively unsung environmental issue that continues to deteriorate already threatened bodies of water. This new research sheds new light on the massive scope of the issue, but if anything at all, illustrates how much additional research must be done to combat the issue meaningfully. The lake-specific factors that the study identifies as the key drivers of algal blooms must be pinpointed, and finding effective remedies for them will be crucial. Rather than any simple, quick fix, this large-scale study indicates that large-scale solutions are not going to be effective, due to the unique set of conditions that define many of the lakes affected by algal blooms. Algal blooms required targeted, decisive action, and will only continue to be compounded by the issue of climate change.
If you’d like to read more on algal blooms, check out this article from my colleague Bria Metzger: http://ursa.browntth.com/the-blog/habs-are-happening-can-we-solve-green-rivers-with-green-infrastructure
Ho J., Michalak A., Pahlevan N. (2019). Widespread global increase in intense lake phytoplankton blooms since the 1980s. Nature (2019)
Lakes are experiencing worse algal blooms, global survey shows [Internet] [2019, Oct. 14]. Retrieved October 22, 2019, Available from https://www.upi.com/Science_News/2019/10/14/Lakes-are-experiencing-worse-algal-blooms-global-survey-shows/9821571071813/?sl=1&ur3=1
Harmful Algal Blooms [Internet]. Retrieved November 3, 2019, Available from
Picture Credit: Phytoplankton SoAtlantic 20060215 [Internet]. Retrieved November 3, 2019, Available from https://commons.wikimedia.org/wiki/File:Phytoplankton_SoAtlantic_20060215.jpg
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