Fossil penguin…. poop?
Here at March of the Fossil Penguins, the fossils we cover are usually skeletons. Sometimes, there are other types of fossil discoveries to discuss, including fossil eggs and fossil feathers. Today, for the first time ever we will feature a story about fossil penguin poop. Paleontologists refer to fossil droppings as coprolites, and they are no laughing matter. Coprolites can reveal a lot about an extinct animals diet and physiology. Recently, a link between long gone penguins and freshly growing plants was uncovered in Antarctica, and the link was seemingly forgotten penguin waste.
A team led by Sharon Robinson, from the University of Wollongong in Australia, recently reported new data on a remarkable type of moss that grows in Antarctica in incredibly harsh conditions. These plants can survive not only freezing temperatures and nearly total darkness during the winter, but also bombardment with UV rays that pierce through at the hole in the ozone layer which forms annually in over the South Pole. These hardships may seem like enough to make any plant give up, but the mosses face yet another difficulty – nearly barren rock with no nutrients. Yet onwards they grow. It turns out the secret source of nutrients is penguin poop.
How did the team figure out that the plants were using the penguin droppings for nutrients? Animal waste carries a chemical signal based on diet. One isotope that scientists can measure is nitrogen-15, which builds up to higher and higher levels as one moves up the food chain. A tiny larval critter that eats algae will have a low concentration, but the sardine that eats that critter will have higher concentration, and the penguin that eats the sardine will have the highest of all. This is because each “eater” absorbs the nitrogen-15 content of its prey and stores some of it. Analyzing a substance for chemical content can reveal its origin. In the case of the moss, nitrogen isotope data indicates they are gaining nutrients from a seabird source. Certainly the mosses are not eating the penguins, so droppings are the most likely substance
The kicker in the story is that there are no penguins living in the area where the moss grows today. The last penguin colony in the area appears to have failed at least 3000 years ago. Traces like nest pebbles show that Adelié penguins once bred in the area. Even though penguins have not returned, their latrines have provided a food source for remarkably hardly plants for millenniums. This study provides a great example of how animals can influence the environment over very long terms.
Coverage by the BBC is here: http://www.bbc.co.uk/nature/18704332