All Hail Plankton: A Study of Climate Change Impacts on Phytoplankton Populations
Kansas City, MO
2019, Senior, Creative Writing
In September 2017, residents of Houston, Texas, saw ruin following Hurricane Harvey. Worse, another tropical storm, Hurricane Irma, would hit the Northern Caribbean and parts of Florida almost immediately afterwards. With millions impacted, reconstruction is still ongoing. In spite of all the devastation, life blossomed along the coasts of the Gulf of Mexico. Massive blooms of phytoplankton could be seen thriving from the runoff of nutrients that the hurricanes pushed into the ocean.[1] These algal blooms have been noticeably more common in recent decades along the Gulf of Mexico, in large part because of climate change, which has undoubtedly caused fluctuations in populations of marine organisms.[2] Despite the resurgence in many phytoplankton populations near coastal areas such as these, many populations are declining around the world. In order to better assess the rapid change these marine organisms are enduring, it is important now more than ever to understand the ways in which climate change affects them.
The key to cracking climate change lies in perspective. People tend to focus on things they can physically see with their own eyes, such as buildings or birds flying overhead. It is much easier to sympathize with a polar bear, so iconic in size and color, than the thousands of marine invertebrate species that vanish every year unnoticed. This viewpoint inhibits a holistic view of the world and the multilayered impacts of climate change. Acknowledging these points, phytoplankton, microscopic organisms that inhabit all salt and freshwater ecosystems, serve as an excellent case study to visualize the various impacts climate change brings to the oceans. By examining the biology of phytoplankton, their impacts as primary producers in relation to climate change, and solutions for mitigating the consequences of climate change and declining phytoplankton populations, we can better improve our understanding of climate change’s effects on marine organisms.
Phytoplankton Biology
Phytoplankton encapsulate hundreds of thousands of different species that range from Precambrian cyanobacteria to larger photosynthetic eukaryotes. However, most conduct photosynthesis, in which they absorb light to fix carbon dioxide (CO2) into chemical energy. This process also releases oxygen into the ocean, ensuring the development and prosperity of most marine organisms. It is estimated that phytoplankton produce about half of the world’s atmospheric oxygen every year, which is equivalent to all the oxygen produced by land plants each year.[3] Because these organisms rely on photosynthesis to survive, they mainly live in the euphotic zone of the ocean, where enough light penetrates to allow for this chemical process.[4]
The two main classes of phytoplankton, dinoflagellates and diatoms, differ in a few ways. While dinoflagellates have more complex shells and use flexible tails called flagella to move through the water, diatoms are composed of more rigid shells and must rely on ocean currents to move.[5] Many phytoplankton, like plants, also rely on nutrients such as phosphate, nitrate, silica, and calcium in order to successfully grow and reproduce. These nutrients, along with sunlight, CO2, ocean temperature, ocean salinity, and wind and ocean currents, also affect the development of phytoplankton populations and can limit resource cycling in the upper ocean layers.[6] Because of their reliance on certain nutrients, phytoplankton populations are distributed unevenly across the globe, with the highest concentrations near places such as coastlines and continental shelves, along the equator in the Pacific and Atlantic Oceans, and in high-latitude areas.[7] Scientists can measure populations of phytoplankton by using satellite imaging to observe levels of chlorophyll in the ocean, one of the main molecules used in photosynthesis.
Phytoplankton play a crucial role as the primary producers of the ocean ecosystem and not only provide food to other smaller organisms such as zooplankton, but also provide oxygen to marine organisms. Because they serve as the foundation of the aquatic food web, they directly or indirectly affect every trophic level above them. The fish and other sea creatures that many people around the world depend on rely on phytoplankton for food. Without phytoplankton, the ocean not only falls apart in biodiversity, but also in carbon dioxide and oxygen levels. Because phytoplankton consume so much CO2 as a result of photosynthesis, they mitigate the effects of climate change by reducing greenhouse gasses and storing several gigatons of CO2 in the bottom-most layers of the ocean.
Another notable feature of phytoplankton is their ability to grow rapidly in very brief periods of time. These periods, known as algal blooms, occur when phytoplankton populations consume a large mass of nutrients and can be seen through satellite imaging as swirls of greens and blues, marking the high concentration of chlorophyll. Some of these surges in populations can produce negative effects on the ocean ecosystems. These harmful algal blooms (HABs) occur when certain phytoplankton species produce toxins that directly affect other marine organisms and can even go airborne to affect birds and land organisms. For example, “red tide” is a HAB in which the dinoflagellate Karenia brevis produces a neurotoxin that inhibits the firing of nerve cells. Such blooms are common occurrences in areas around the Gulf of Mexico, and notably Florida, in recent years.[8] While the less harmful blooms may appear healthy to marine ecosystems, in some cases they can lead to ocean hypoxia or “dead zones” when organisms decomposing the dead phytoplankton deplete a large quantity of oxygen in the ocean. By analyzing these algal blooms, scientists can get a sense of global shifts in phytoplankton populations and how they have changed over the years. With so many factors affecting phytoplankton populations and consequences resulting from their presence in ocean environments, it is crucial now more than ever to see how climate change has impacted them on a global scale.
Climate Change and Phytoplankton
While phytoplankton populations have fluctuated with a high level of variance since the 1940s, an overall decline in their population is evident and likely caused by climate change, intensifying coastal eutrophication, land runoff, and other anthropogenic factors.[9] These changes pose significant threats to phytoplankton populations, who will either be forced to migrate to more habitable environments or die. Phytoplankton’s demographic change is particularly concerning because of the role they play in net primary production (NPP), the energy available to consumers in an ecosystem. While phytoplankton and other similar marine organisms only represent 0.2 percent of biomass of the world’s primary producers, they produce nearly half of the biospheric NPP.[10] This means that phytoplankton are the cornerstone of the oceanic food chain. Any major fluctuation or shift in their population will reverberate throughout the ocean.
Because of human-induced greenhouse gas emissions, the ocean will experience, over the next century, significant physical and biogeochemical changes. Multiple studies all indicate changes in ocean salinity, increasing oceanic temperature, and increased ocean acidity in response to anthropogenic carbon.[11] Higher ocean temperature may also have a significant impact on the vertical cycling of nutrients in the upper layers of the ocean, leading to less available nutrients for phytoplankton to grow.[12] These developments pose a significant threat to phytoplankton populations who are not suited to these rapid changes. Andrew Barton, oceanographer and associate research scholar at Princeton University, asserts that, “[Phytoplankton are] incredibly important,” because, “they’re at the very bottom of the food chain, and what happens at the bottom impacts everybody.”[13] In a 2015 study, Barton and a team of researchers tracked trends in ocean temperature and salinity and found that phytoplankton in the North Atlantic basin will gradually migrate towards the cooler Greenland Shelf.[14] This migration has the potential to disrupt fish and other marine populations in the North Atlantic Basin who rely on phytoplankton for food. This development will either drive those marine populations north or see a diminishing marine population in the North Atlantic.
The migration of phytoplankton communities northwards poses a looming threat to coastal communities that rely on fishing. Fish and phytoplankton share an intertwined relationship, where the size of a phytoplankton population influences the growth and reproduction rates of local fish populations.[15] The absence of phytoplankton is felt not only by maritime populations, but humans as well. One example comes from the collapse of the Faroe Islands’ fishing-dependent economy during the 1990s. Declining phytoplankton populations in the 1990s contributed to a shrinking cod population in the Faroe Shelf. The declining cod populations led to the collapse of the Faroe Islands’ fishing-dependent economy and led to heavy debt, significant emigration from the island, and over 18 percent unemployment.[16] As phytoplankton migrate seeking more suitable habitats, coastal communities will have to deal with declining fish populations and a declining local economy. Because phytoplankton are so fundamental to the marine food chain, any major change involving phytoplankton inevitably spills over to affect the rest of our interconnected world.
Potential Solutions
Because phytoplankton play a significant role in marine environments, they must be protected in order to cultivate a sustainable future for all. The ocean acts as a carbon sink, a source of revenue, and reservoirs of biodiversity that humanity should protect. Communities most impacted by the changing ocean must lead us in the push to save our oceans. Over 34 percent of the world’s coasts are at high risk of degradation from coastal development. For that reason, coastal communities should be the first to pass stronger fertilizer restrictions, transition away from septic systems to sewers, and better manage stormwater pollution.[17] These actions can help curb the decrease of pH in the ocean, which pushes phytoplankton further north, away from fisheries that sustain coastal economies.
Even communities hundreds of kilometers away from the sea can assist the ocean. The Environmental Protection Agency (EPA) lists nutrient pollution as one of the leading causes of degradation to water quality inland and in coastal systems.[18] Paired with phytoplankton’s ability for sudden growth, the influx of nutrients, such as nitrogen and phosphorus, can lead to harmful algal blooms. Most of these nutrients come from Midwestern agricultural communities. Active inland citizens can limit coastal eutrophication by planting vegetation along stream beds and rivers to slow erosion and absorb nutrients, while other individuals can limit the usage of industrial scale fertilizers.[19]
Immediate global cooperation is key to mitigating the rapid anthropogenic changes occurring in our oceans. Recent research led by Professor Joe Roman from the University of Vermont shows that whales and other marine mammals enhance phytoplankton nutrition through their fecal plums.[20] With many whale populations at historic lows in the North Atlantic, many areas may be missing a key player in the recycling of nutrients for phytoplankton. We must urge our public leaders to support landmark regional and international protocols and conventions on ecological maritime protections such as the 2030 Agenda for Sustainable Development or the Caribbean Environment Program.[21]
Conclusion
While observable changes have been seen in global phytoplankton populations in the past few decades, more needs to be done to ensure the safety of the world’s phytoplankton. Phytoplankton are not only the primary producers of the marine food chain, they also form the basis for marine life as we know it. We must ensure that nothing disrupts this firm foundation so that people, animals, and marine life can continue to live environmentally sustainable lives. We, as humans, do not live lives disconnected and severed from nature. The opposite is true. What happens to even the smallest of marine organisms can have massive ramifications for human populations. Going forward, we must take measures to lessen the consequences of climate change while also ensuring the safety of organisms such as phytoplankton, so that all organisms can thrive together.
[1] Natalia Alamdari, “‘Mother Nature is very resilient’: A Year After Hurricane Harvey, Coastal Ecosystems are
Thriving,” The Texas Tribune, https://www.texastribune.org/2018/08/15/year-after-harvey-scientists-continue-study-its-environmental-effects.
[2] Ibid.
[3] WHOI, “Phytoplankton,” accessed June 16th, 2019, https://www.whoi.edu/know-your-ocean/ocean-topics/ocean-life/phytoplankton.
[4] Ibid.
[5] Phytoplankton Identification, “Diatoms and Dinoflagellates,” accessed June 17th, 2019, http://oceandatacenter.ucsc.edu/PhytoGallery/dinos%20vs%20diatoms.html.
[6] NASA, “What are Phytoplankton,” accessed June 16th, 2019, https://earthobservatory.nasa.gov/features/
Phytoplankton.
[7] Ibid.
[8] Danielle Hall, “What Exactly is a Red Tide,” Ocean.si.edu., https://ocean.si.edu/ocean-life/plants-algae/what-exactly-red-tide.
[9] Daniel G. Boyce, Marlon R. Lewis, and Boris Worm, “Global Phytoplankton Decline over the Past Century,” Nature 466 (2010): 591-596, DOI: 10.1038/nature09268.
[10] Christopher B. Field et al., “Primary Production of the Biosphere: Integrating Terrestrial and Oceanic
Components,” Science 281, no. 5374 (1998): 237-240, DOI: 10.1126/science.281.5374.237.
[11] L. Bopp et al., “Multiple Stressors of Ocean Ecosystems in the 21st Century: Projections with CMIP5 Models,”
Biogeosciences 10, no. 10 (2013): 6225-6245, DOI: 10.5194/bg-10-6225-2013.
[12] P.G. Falkowski, “The Role of Phytoplankton Photosynthesis in Global Biogeochemical Cycles,” NCBI 39, no. 3
(1994): 235-258, DOI: 10.1007/BF00014586.
[13] Sarah Watts, “Global Warming is Putting the Oceans’ Phytoplankton in Danger,” Pacific Standard,
https://psmag.com/environment/global-warming-is-putting-phytoplankton-in-danger.
[14] Andrew D. Barton et al., “Anthropogenic Climate Change Drives Shift and Shuffle in North Atlantic
Phytoplankton Communities,” PNAS 113, no. 11 (2016): 2964–2969, DOI: 10.1073/pnas.1519080113.
[15] Petur Steingrund and Eilif Gaard, “Relationship Between Phytoplankton Production and Cod Production on the
Faroe Shelf,” ICES Journal of Marine Science 62, no. 2 (2005): 163–176, DOI: 10.1016/j.icesjms.2004.08.019.
[16] Bjarne Skafte and Pernille Thinggård, “The Economic Situation in the Faroe Islands,” Danmarks National Bank,
http://www.nationalbanken.dk/en/publications/Pages/2003/10/The-Economic-Situation-in-the-Faroe-Islands.aspx.
[17] Mara Dias and Holly Parker, “Take Action on Harmful Algal Blooms & Toxic Red Tides in
Florida,” Surfrider Foundation, https://www.surfrider.org/coastal-blog/entry/
take-action-on-harmful-algal-blooms-toxic-red-tides-in-florida.
[18] EPA, “Preventing Eutrophication: Scientific Support for Dual Nutrient Criteria,”
https://www.epa.gov/sites/production/files/documents/nandpfactsheet.pdf.
[19] New South Wales Catchment Management Authority, “Waterways: Streambed Erosion,”
http://archive.lls.nsw.gov.au/__data/assets/pdf_file/0011/495785/archive_waterways-streambed-erosion.pdf.
[20] Joe Roman et al., “Endangered Right Whales Enhance Primary Productivity in the Bay of Fundy,” Plos One 11,
- 6 (2016): 1-14, DOI: 10.1371/journal.pone.0156553.
[21] UNEP-Nairobi Convention and WIOMSA, The Regional State of the Coast Report: Western Indian Ocean
(Nairobi, Kenya: UNEP and WIOMSA, 2015) 263-267, https://read.un-ilibrary.org/environment-and-climate-change/regional-state-of-the-coast-report_dd8dca69-en#page1.
Reflection
For this year’s paper, we decided to focus on one of the smallest and most significant organisms in the ocean—phytoplankton. The choice was one we reached after much deliberation. In a sense, we saw ourselves in phytoplankton. While we may be detached from any greater effort to individually combat climate change, together we form a significant body capable of combating climate change for the better. The research for this project was divided amongst the three of us, with each of us writing about an area that we found personally interesting. We all concluded that we could incorporate fields that interest all of us. Those fields were biology, economics, and international cooperation. We believe that this not only gives our paper more value for analyzing phytoplankton through multiple lenses, but also makes this paper more valuable as a piece on phytoplankton by summarizing these viewpoints in one paper. Furthermore, we wanted to highlight a lesser known marine species that deserve just as much spotlight as the popular sea turtles or coral reefs. After entering this contest last year, we were excited to write again about marine organisms and the effects of climate change on our world’s ocean. Being from the Midwest, we often feel disconnected from coastal regions but still can in many ways help to educate about ocean conservation. We hope that we can spread awareness about the crucial role that phytoplankton serve in our environment as well as help to inspire action when combating climate change.