When most people think about the impacts of climate change on the world’s oceans, they’re first thoughts are things like ‘corals’ and ‘ocean acidification’. And while these are both excellent examples of how climate change affects the oceans, they’re not the only ones. Science magazine recently published a great article by Hunter-Cevera et al., 2016 about how changing climate, specifically rising ocean temperatures, have important implications for phytoplankton blooms in the Northern Atlantic Ocean.
If you’ve been following UNdertheC for awhile, you probably already know what phytoplankton are, but for you newbies, phytoplankton are tiny organisms that float and live in the ocean. They’re kind of like plants in the sense that they can make their own energy via photosynthesis, but, unlike plants, they live in a three dimensional world and are at the mercy of the ocean currents and the ocean’s physical environment. And this physical environment is changing in response to climate change. Specifically, the ocean is warming. And as the ocean warms, temperatures warm earlier in the spring. It’s this earlier warming in the spring that is having an impact on phytoplankton blooms in the Northern Atlantic ocean. With warmer temperatures earlier in the year, phytoplankton are able to bloom earlier and earlier.
This notion of earlier phytoplankton blooms has been hypothesized before, but what makes this study unique is there ability to show the earlier blooming was due to more phytoplankton growth as opposed to less phytoplankton death. There are two ways phytoplankton blooms can occur, and if we think about it in terms of M&M’s it might be easier (and tastier!) to understand. Think of it this way: if you had some number of M&M’s, say 10 M&M’s. If you started eating two M&M’s per minute, in order to keep the same number of 10 M&M’s, you’d have to not only eat two M&M’s per minute, but also replace two M&M’s per minute from the bag. This is called steady state – when one phytoplankton is created, one phytoplankton dies (or as you eat two M&M’s, you get two more M&M’s from the bag to replace them).
If, however, you removed two M&M’s from the bag per minute but only started to eat one M&M per minute, you are no longer at steady state and would start to accumulate M&M’s. This is one way a phytoplankton bloom can form: more phytoplankton are growing than are being removed.
Another way a bloom can form is if more phytoplankton are growing than are being removed. Back to the M&M’s: if you start to get three M&M’s out of the bag per minute but eat two M&M’s per minute, then you would start to accumulate M&M’s (you would now have 11 M&M’s after the first minute, then 12 after the second minute, and so one). This is also a bloom. And this is what the study was able to show happens to the phytoplankton earlier, and earlier in the year. More phytoplankton are produced than consumed and you start to get more phytoplankton in the water.
The way the study figured this out was through a TON of data they collected for 13 years! That’s a long time, but that long time is necessary to understand these long term trends. There is so much variability in day-to-day weather, that in order to understand how climate (which underlies weather and is essentially weather on decades-long time scales) impacts things like phytoplankton production (or even coral growth) you have to study things on very long time scales (13 years, or more!). Science is not an overnight thing but takes years of dedicated patience and persistence, but with this dedicated persistence, you can discover some pretty cool things!