May 31, 2022
by Nicole Misarti
Presentation by Nicole Misarti at the 2021 Ecosystem Studies of Subarctic and Arctic Seas (ESSAS) Webinar Annual Science Meeting in Sapporo, Japan 30 May–4 June, 2021
Transcript:
Most people see the world like this, but paleoecologists, we see the world like this, particularly those of us who specialize in the isogeochemistry of bones and teeth. But we also look at shells, soils, and sediments and all of these materials are archives of the past, a single bone, for example, can tell us a story about what an individual's life, sex, size, health, diet, and geographic location.
But why should we care about the past? How is this research relevant?
It's relevant because research about the past lends context to our current research and knowledge. It helps us understand where we are now, and perhaps even how and why we got there. The past can also give us clues to how a species, ecosystem, etc, will adapt to future change.
This is one of the reasons why partnerships between paleoecologists and neoecologists, are essential.
We ask many of the same questions other ecologists do and we use multiple lines of evidence to paint a picture of how and why a population may have changed over time.
Did a population of a particular species grow, did they move, has their diet changed, and in what way were they stressed, was reproduction high or low at any given time, and how did all of this change through long time periods.
In this way, we can reconstruct shifting baselines throughout history and prehistory.
The methods on the screen are just a few of the methods paleoecologists use to reconstruct food webs, climate, oceanographic conditions, etc.
Many of these will be familiar to most of you, but we extract this information from less familiar materials, take stable isotopes for an example.
We analyze nitrogen and carbon from proteins, and in the case of bones and teeth that's, that gives us information on trophic dynamics and position of the plant base of the food web productivity and even geographic location.
Proteins are even bound up in shell and we can extract those as well. Compound specific amino acid isotope work can help us fingerprint that base of the food web and better understand whether change through time is based on a change in prey or a bottom-up, driven productivity change within the entire system.
We look at oxygen and carbon from carbonates in shells, corals, bones, teeth, and sediments. These can give us, for example, sea surface temperature estimates from shells and coral, amount of precipitation, and origin of moisture in ice and lake cores.
Geographic location, in conjunction with sulfur isotopes from teeth and bone, and when used in conjunction with collagen data in bone and teeth, it can help parse out terrestrial versus coastal diets, which is mostly helpful in humans.
In lake and ocean core sediments, we can also use carbon as a proxy for productivity. Lakes with salmon have the added bonus of being able to use nitrogen data to give a relative number of returning salmon into a system.
Even nitrogen and tree rings from trees at the edge of salmon lakes and streams can be used to look at this. For more information on tree rings I'll let Ben Gaglioti tell you about the other proxies including a more precise look at timing of when different events and changes occurred.
Trace element data is also very useful and can come from bone, teeth, shell, and sediment, for example, we can trace mercury in the food web. In walruses we've found that we can use zinc to trace the age at sexual maturity through teeth, and we can also trace the year at which a walrus is weaned through barium in teeth and we're hoping that all of this translates to terrestrial species as well.
Hormones can also be extracted from bone. This includes progesterone, cortisol, testosterone, and estrogen. This allows us to look reproduction levels as well as stress in animals. Oddly, we have been unable to successfully sex an animal using testosterone and estrogen as both sexes can have either hormone.
We also use DNA just with different techniques and again extracting from slightly different materials.
This includes soils and sediments and that's called eDNA or environmental DNA. As techniques advance, we are also able to do more than just look at ancient DNA that's maternal DNA. If a bone is preserved well enough, we can also look at snips or nuclear DNA.
We can use bones to look at the size of an individual, sometimes it's sex, and a general age class for that individual.
Some health metrics can also be analyzed based on bone conditions, arthritis is a good example of this. Teeth can tell us a more exact age in the same way that growth annuali on shellfish can, as can the otoliths in fish and growth rings in trees. We can use things such as percent opal and ocean cores to give us an idea of productivity and the type of plankton at any particular time.
Pollen data and terrestrial cores can tell us what plants, as well as the types of moisture and temperature regimes at a particular time.
Because I keep talking about time, I also need to mention radiocarbon data, which can help us put all of this data into timeframes in the past, but not always as precisely as we would like. Usually radiocarbon dates come with a plus or minus of a certain number of years, but it's an extremely useful tool. Tree rings and even corals can give a more accurate time, down to the year, if they can be consistently matched with others until a known date.
Speaking of known dates this brings us to historic documents and traditional knowledge, both of which are invaluable to our work.
We can glean particular historic occurrences in time, general weather, ecosystem stage, precipitation amounts, information about a species, and perhaps it's diet and habitat, all from a certain time period if we are looking closely enough at the documents.
All in all, using these techniques paleoecologists can trace changes in ecosystems, climate, and species over long periods of time and begin to place the current information we have about them into context with past change and their ability to adapt to all of those changes.
Thank you very much.
