Poop. Yeah that’s right I said it. It’s what makes the world go round. Not really that’s mostly done by gravity, but in the marine environment poop is very important. If you pass by sizable rocky islands you may notice that a lot of are the same shade of brownish-white. This is not because they were all formed by the same type of rocks, no it’s because a whole consortium of different types of animals love to sit on top of those rocks to rest, eat, and…poop. These islands don’t have any organisms like dung beetles or fungi to clean up the pop so it just sits there and bakes. On a sunny day you can smell it from pretty far away if you’re downwind. Layer upon layer of this stuff gathers and hardens making a sometimes meters thick shell coating on these rocky outcrops that we call guano. It’s full of nitrogen, phosphorous, and potassium, and is super useful as fertilizer for terrestrial plants. It’s so valuable major colonization efforts and wars in the western world were fought over it in the 18th and 19th centuries to secure control over a reliable fertilizer resource. It also sparked the earliest western society wildlife conservation efforts after some folks noticed that if the animals that pooped on the rocks were disturbed too much or didn’t have enough fish to eat, they supply of guano would quickly diminish!
The most important function that guano serves is that it fertilizes the ocean. Occasionally when it rains hard or the tides or waves reach up onto the rocky outcrops encrusted with poop, it gets washed away! But don’t worry it doesn’t go very far. All of the nutrients are quickly used up by algae species, like kelp, to help them grow. The oceans are usually pretty nutrient poor, one because they’re so big and all the nutrients are spread pretty thin, and two, because most of the nutrients fall to the very bottom where they are functionally useless for algae and plants that need sunlight. So, next to these guano rocks huge forests of kelp sometimes grow using all the nutrients that are washed into the sea. These kelp forests provide food and safe havens for young invertebrates and fish that eventually feed the birds and sea lions that create the guano thus completing the circle. Oh, and one more thing these algae produce more than half of all the oxygen we breathe, so next time thank the poop instead of remarking on its smell! Have a San Juanderful Day!
Naturalist Erick
