So. Many. Tiny. Cups. That’s the conclusion today after my first foray into stable isotope analysis with Henna. Though I must admit, chemistry was my least favorite subject in my early years, with a few years more wisdom, its benefits have become evident. Stable isotope analysis is a tool that allows us to measure the relative weight of carbon and nitrogen in freeze dried tissue samples. The weight of carbon helps us discern the original source of primary productivity in the tissue sample of interest. For instance, organisms that feed on suspended phytoplankton, such as diatoms, should have a different carbon isotope signal than organisms that feed on seaweed, this signal is proliferated up through each subsequent level in the food web. The weight of nitrogen in an organism’s tissue is correlated with its trophic level, or its position in the food web. Organisms that are higher order consumers such as sharks will have a heavier isotopic nitrogen signal than lower order consumers such as sea urchins.
Next, it’s off to the mass spectrometer for these little samples. Within a few weeks, we hope to have data back which give us a first look into how food web structure compares between natural and man-made shorelines in Sydney Harbor.