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  • Aster Hoving

Some Sciences of Ocean Rhythms

How do scientists know historical movements in the ocean? How do they know patterns of the past, such as ocean upwelling or temperature variations?

Recently, a group of researchers from the Monterey Bay Aquarium used algae that were stored in a museum in order to get insight into historical upwelling patterns.[1] Upwelling refers to the process by which cold, nutrient rich water moves upward in the ocean to replace warm, nutrient poor water. Algae register these environmental fluctuations in their chemical makeup because they respond, for instance, to excesses and restrictions in nutrients. When nutrients are available, algae grow and absorb them. One nutrient these scientists were interested in was nitrogen, which remains as readable sign in the material structures of algae—much like how the seasons of the past can be seen on the inside of trees in the shape of tree rings.


Or, actually, those tree rings are much more like the shells that researchers also use. Environmental fluctuations literally leave rings on the material make up of shells. Another recent piece of research I encountered not so long ago looks at an ancient mollusk called Torreites sanchezi.[2] This mollusk grew very fast, which means that its growth rings don’t just reflect the longer temporal patterns of oceanic upwelling, but also seasonal and even daily ones! These researchers managed to see, in the rings of this mollusk, that the length of the days was half an hour shorter 70 million years ago.


An ongoing question in my mind is something like this: to what extent can these material markers in bodies be used to generate general data that exceeds individual organisms? And to what extent do these bodies resist generalization on the basis of their specific and situated experiences?


In relation to this I am interested in a final piece of recent research also based on algae and shells, but this time not pressed algae specimens or a fossilized shell. Organisms end up compressed in ocean sediments as well, which is another way in which they are read for historical fluctuations. Another group of scientists recently figured out that, when calculating annual changes in global average temperatures, organic materials such as shells had wrongly been assumed to represent the entire year.[3] Instead, it is more likely that they were formed during the summer, when the organisms grew. This means that the slow cooling of the earth that was thought to have started 6000 years ago was actually the start of a period of cooler summers, while average annual global temperatures kept rising.


The analytic importance of rhythm, as opposed to the assumption of stasis, is clear here: attention to rhythms allows us to more accurately approach our current and past environments. In the case of this last group of scientists, they used their insight into the seasonal situatedness of their data to correct existing estimates of the earth’s historical temperatures. This allows them to know in what ways global temperatures and other patterns are changing. Sticking with this analytic importance of rhythm, I wonder if this case also shows us more than a corrective of data—what does it tell us about the relationship between rhythm and generalization?


Notes

[1] For the original paper, see: https://royalsocietypublishing.org/doi/10.1098/rspb.2020.0732. I also consulted the following article: https://www.hakaimagazine.com/article-short/scientists-use-seaweeds-to-travel-back-in-time/ [2] For the original paper, see: https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019PA003723. I also consulted the following article: https://phys.org/news/2020-03-ancient-shell-days-half-hour-shorter.html [3] For the original paper, see: https://www.nature.com/articles/s41586-020-03155-x. I also consulted the following article: https://www.theguardian.com/environment/2021/jan/27/climate-crisis-world-now-at-its-hottest-for-12000-years