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Biological oceanography

If you can’t stand the heat, get out of the kitchen: An analysis of phytoplankton with changing ocean temperature

References: González-Silvera, Adriana; Santamaría-del-Ángel, Eduardo; Camacho-Ibar, Victor; López-Calderón, Jorge; Santander-Cruz, Jonatan; Mercado-Santana; Alfredo. (2020). The Effect of Cold and Warm Anomalies on Phytoplankton Pigment Composition in Waters off the Northern Baja California Peninsula (México): 2007–2016. J. Mar. Sci. Eng. 8, 533-551.

DOI: https://doi.org/10.3390/jmse8070533

Reading Time: 5 minutes

An image of a phytoplankton. Image Credit: NOAA MESA Project

To begin, let me ask a question. Have you ever visited a beach during the winter? The sky may be gray and the wind may be chilly. How about the water? Would you jump in? It would be too cold right? Now let us picture the summer. Bright blue skies and warm sun rays showering upon the sands. The water is warm (or at least more hospitable) and you decide to hop in. Now let us think about this, we decided not to get into the water because it was too cold right? We are not alone as creatures of all sizes skip out on taking a cold dip! Animals like sharks and whales migrate across oceans, and we are constantly learning more about their migrations. Recently, researchers at the Universidad Autónoma de Baja California have found that even microscopic critters called phytoplankton move as the ocean changes temperature! The group of scientists focused on the Pacific Ocean close to the Baja California peninsula as there were two significant time periods when the water heated up, the Pacific Heat Anomaly (2014) and El Niño (2015-2016). They investigated the water down to a depth of 100 meters for phytoplankton over the years 2007-2016 and found some interesting results!

What did they find?

After a lot of calculations, the group found that there were less phytoplanktonat the ocean’s surface when the sea temperature increased. On the other hand, the amount of phytoplankton stayed the same below 40 meters (a.k.a. subsurface) when the water temperature increased. This means that the ocean warming causes a big discrepancy in water conditions. Phytoplankton perform a plethora of functions, like photosynthesis, which are incredibly important for both the water around them and the animals that would eat them. So, these discrepancies in water temperature can cause large shifts in the hospitability of the surface ocean environment for phytoplankton.

In addition, the researchers found that several different types of phytoplankton lived in the ocean at different depths. When the water temperatures changed, they found that the phytoplankton shifted as well! Meaning phytoplankton moved away from (or toward) the water because of its temperature, just like us at the beach! The team of researchers noticed that there were some permanent residents of the waters there (including groups like diatoms, dinoflagellates, Chrysophytes, and Cyanobacteria), but these groups did not always show up in the same amounts with regards to depth and time. The researchers also found that some phytoplankton could absolutely dominate the water! For example, the phytoplankton Prymnesiophytes monopolized the waters near the Todos Santos Bay (see image below) in May 2011, yet their population shrank to 40% of the total phytoplankton in October 2011. So, it is worthwhile to acknowledge that this ocean environment is incredibly complex in its behavior.

How did they do it?

The location of the ANTARES station where the group took their water samples. Image Credit: González-Silvera et. al.

The researchers used multiple strategies to investigate phytoplankton groups. First, the group took samples of the water at a station (called ANTARES station) about 10 kilometers off the coast of Todos Santos Bay for their experiments. From these samples, they used a machine called a HPLC (which stands for High-Performance Liquid Chromatography) which could separate and quantify molecules from the phytoplankton. The group targeted the coloring pigments of each group, as they are generally unique between each other, as well as the total chlorophyll a that these phytoplankton groups have. With the help of this analytical machine, the researchers could deduce which phytoplankton were in the water sample and how much of them were there.

Measurements of chlorophyll a at different depths. Image Credit: González-Silvera et. al.

To further inform their results, the group studied additional data from the ANTARES station. They investigated the nitrate and silicate molecules in the water, as these are both significantly important for phytoplankton to grow and function. These molecules Last, the group used satellite images of the water surrounding the ANTARES station to confirm the presence and amount of chlorophyll from phytoplankton. All of these methods were combined to produce their holistic understanding of that ecosystem of phytoplankton.

Why does it matter?

The researchers wanted to investigate this specific area for a longer period of time, as collecting continuous data provides us with a better understanding of the oceans around us. By studying phytoplankton over a long time period, we can understand how creatures of all sizes adapt to the water temperature as well as the conditions of that environment. As mentioned above, studying phytoplankton provides us insight into where larger animals would travel to eat them. Furthermore, investigating the amount of phytoplankton in an area can explain the productivity of local fisheries as they are both connected through the ocean’s food web. In conclusion, these analytical experiments provide a more accurate depiction of our world and how it behaves around us.

Hey! I’m a PhD student at the University of California, Davis studying biophysics. I previously studied organic chemistry (B.S.) at the College of William and Mary. Currently, I investigate the physical responses of lipid membranes to their environmental stimuli and explore the mechanistic potential of the protein reflectin, from D. opalescens, in soft matter systems. Generally, I am interested in how biological systems respond to physical stressors across all size scales, no matter how big or small! I am driven to pursue a career in science communication and outreach, especially in translating research findings into actionable, grassroots reform. Outside of school, I surf the Norcal coastline, play ultimate frisbee, and read.


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