Preliminary Raw Data - 13C and Vegetation

Aloha everyone!

I wanted to share with you some of our raw preliminary data. We have conducted isotope analysis on six shells (of multiple genera), which have given us valuable information about what the environment might have been like at different times at our study site, Ka'ena Point State Park!

For our project, we are conducting isotopic analysis on complete shells gathered from our study site. Full information about how we are preparing shells for isotopic analysis can be found in the Methods tab of our project, under the note "Preparing Shells for Isotopic Analysis."

We will be examining 13C and 18O isotopes, which tell us about the environmental conditions that our snails lived in thousands of years ago. Today I'm going to focus on what we have learned from our preliminary work with 13C isotopes.

 

13C information vs 14C age from six shells gathered from our study site, Ka'ena Point State Park. A lighter isotopic signature indicates cooler and/or wetter conditions, while a heavier isotopic signature indicates hotter and/or drier conditions. Isotopic analysis conducted at the UC Davis Stable Isotope Facility in 2019.

13C isotope data can tell us what type of vegetation our snails lived and fed off of. "C3" plants thrive in cool and wet environments, while "C4" plants thrive in hot and dry environments. Because of differences in how these different types of plants do photosynthesis, C3 plants also have lighter isotope signatures (more negative) than C4 plants, which impacts the isotopic signature of the snails that eat these plants.

Finding a lighter isotopic signature in a shell tells us that the snails were feeding off of more C3 plants than C4 plants, which means that the environment was most likely cool and wet (ideal conditions for a snail!). In contrast, a heavier isotopic signature (less negative) means that the snails were feeding on C4 plants, which tells us that the environment was heating up and/or drying out.

This graph, made from our preliminary data, indicates that as years went by, the environment may have been heating up and drying out, as shown by the isotopic signatures getting heavier. However, six shells is too small a sample size to say anything for certain yet about how the environment may have been changing, which is why we would like to examine more shells.

It's important to note that this change is taking place over tens of thousands of years, in stark contrast to the climate changes we are seeing take place today. However, we expect that the information we learn from our project, which is examining a period of natural climate change on the Hawaiian island of O'ahu, can help us prepare for changes we may see in the coming years.

Mahalo for reading, and for your support!