By Do-Yeon Myeong
Foraminifera (pronounced ‘For-a-mi-ni-fer-a’)
It may sound quite unfamiliar, but you’ve probably touched it, stepped on it, and even bought it during your summer vacation at the beach. Foraminifera is one of the most common creatures you can find in the coastal area. Yet, it would have been very hard to differentiate it from other particles; being just less than one centimeter of height, its life would’ve been a tough one to recognize.
In spite of its size, this minute creature contributed greatly to the understanding of the paleoclimate and finally became the main agent of your weather forecast. The image below, outlines this lovely creature that rules over paleoclimatology.
Left: foraminifera from Viti Levu, Fiji / Right: foraminifera from Ulleung basin, Korea
What is, exactly, Foraminifera?
Foraminifera is an amoeboid protist with a grand history of 550 million years (starting from the Ordovician period). Because of their impressive evolutionary speed and environmental sensitivity, more than 5,000 species have been discovered around the globe, and some are still being discovered today.
Basic features of Foraminifera
Foraminifera contains the following structure, which serves as a guideline for their taxonomy.
Basic structure of foraminifera
Shells made of Calcium carbonate(CaCO₃)
Pseudopodia - made for mobility
position and the diameter of basal cavity
In addition to these structural features, Foraminifera are also distinguished by their habitat. First, there are ones that live floating in the sea (planktonic). Secondly, there are ones that live in the sea basin, crawling by their gastric limbs (benthic). Using their pseudopods, both foraminiferal species hunt on minute organisms to obtain the nutrients from the seawater.
How Foraminifera conveys Climatic Information
The study of Foraminifera’s evolution paves the way to investigate paleoclimates. For example, the general coil position shift of the foraminifera community shows the shift in the water temperature or salinity. A clockwise-direction coil is called the SN coil, and the opposite is called the DX coil. SN coil is often observed in the higher latitude with low temperature and more salinity, while DX coil is found in the lower latitude with higher temperature and less salinity. So, if one colony’s coil was SN dominant at first, but became DX dominant as time changed, it reflects that the region has experienced some salinity decrease or temperature rise. Similarly, other structures like size, the lamellar structure of a shell, and pseudopod length contribute to such reasoning of tracing down the paleoenvironment.
Foraminifera fossils also tell us quite accurate information about the temperature of a certain period in a more chemical way; by Oxygen isotopes. Mostly made of Calcium carbonate, foraminifera mainly contains oxygens in their shells. So the scientists dissolve them in the HCl and obtain CO₂ gas, therefore obtaining the oxygen composition ratio of an ancient environment.
The ratio of 18O in an overall Oxygen composition is inversely proportional to the average water temperature of the sea. This happens because 18O is heavier than 18O. In warmer climates, 16O tends to evaporate easily and follow the water cycle without altering the original portion. However, when temperatures decrease, these light oxygen atoms are trapped inside the ice and the glaciers, therefore increasing the portion of the 18O.
Valuable data obtained is then processed, being used for further research, or ending up in a climate observatory such as NOAA. And every morning, you are likely to get your weather alarm from our little weather - helper, foraminifera.
Examples of recent foraminifera-based paleoclimate research topics
Did you know that there was actually a climate change very similar to current global warming 5.5 billion years ago? Well, there is! In the period called Paleocene-Eocene Thermal Maximum (PETM), the rapid change of climate was caused by the abnormal increase of calcium dioxide and methane, which evoked dramatic changes in the earth’s environment. In PETM, the ancestors to the current mammal species rose, and gymnosperm were nearly overpopulated by the angiosperm plants.
There were no exceptions for foraminifera. Due to the sudden rise in temperature and lack of calcium carbonate in the sea at the time of PETM, 35% to 50% of the foraminiferal species became extinct, and the surviving species had to undergo a change in their structure or lifestyle. The table below is a chronological breakdown of Foraminifera excavated in the Shakla, Dohook, and Shakla in Western Asia (Iraq), indicating that about 80% of the existing species died out during the PETM period, and were replaced by the new ones which were fitter than the primary species. Reaching this period in both evolutionary reasoning and chemical experiments, paleontologists are eager to find more information about it and use it as a guiding stone for predicting the future.
Foraminiferal distribution in the Sinjar, Dohuk, and Shaqlawa sections (Wan, Larger benthic foraminiferal response to the PETM in the Potwar Basin (Eastern Neo Tethys, Pakistan),2021)
References
Introduction to the Foraminifera. (n.d.). https://ucmp.berkeley.edu/foram/foramintro.html
Zakrzewski, R. (2005). Biodiversity response to climate change in the Middle Pleistocene—the Porcupine Cave fauna from Colorado. Anthony D. Barnosky (ed.). 2004. University of California Press, Berkeley, 385 p., cloth. ISBN 0-520-24082-0. Journal of Paleontology, 79(6), 1239-1240. doi:10.1666/0022-3360(2005)079[1239:R]2.0.CO;2
Babila, T. L., Penman, D. E., Standish, C. D., Doubrawa, M., Bralower, T. J., Robinson, M. M., Self‐Trail, J. M., Speijer, R. P., Stassen, P., Foster, G. L., & Zachos, J. C. (2022). Surface ocean warming and acidification driven by rapid carbon release precedes Paleocene-Eocene Thermal Maximum. Science Advances, 8(11). https://doi.org/10.1126/sciadv.abg1025
Muhammad Kamran, Fabrizio Frontalini, Dangpeng Xi, Cesare Andrea Papazzoni, Arman Jafarian, Khalid Latif, Tian Jiang, Kamran Mirza, Huyue Song, Xiaoqiao Wan, Larger benthic foraminiferal response to the PETM in the Potwar Basin (Eastern Neo Tethys, Pakistan),2021