The Food Chain
Everything in the sea is waiting to be a meal for something else. “Troph” means “food,” so we call each link in the food chain a “trophic level.”
Surfers sometimes say, “Enter the water, and you enter the food chain.” It’s true today, and it was just as true in the Cretaceous. But what does a marine food chain look like?
On land, everything depends on “primary producers” – plants like grasses that turn energy from the sun into energy that supports herbivores like rabbits and deer, which in turn provide energy for carnivores like wolves and foxes. In the sea, what we think of as plants can be hard to come by. The primary producers are actually tiny organisms that float around, suspended in the water. They get eaten, not by herbivores, but by animals called “suspension feeders” that filter seawater all day just to find these tiny sources of energy. Those suspension feeders – clams, oysters and other invertebrates – make up the bulk of the fossils at the Inversand quarry, followed by the animals that ate them, like rays and fish, followed by the animals that ate those animals, like crocodiles and mosasaurs. What ate mosasaurs? Only the vast, indifferent passage of time.
Learn about the roles – or trophic levels – these creatures played in their ecosystem:
The base of the food chain
On land, primary producers are plants. We’ve found a few bits of wood that floated out to sea, but most of the primary producers in this ecosystem were tiny organisms that lived suspended in the water. Sometimes we can see their fossilized shells with a microscope, but most of them weren’t preserved at all.
The fruits of the sea
The second level of the food chain is made of animals that ate the primary producers. These are the clams, oysters, sponges and others that evolved digestive systems suited for catching and absorbing tiny organisms and edible particles directly from the water or sand deposits they lived in. They were extremely abundant and would have covered the sea floor in a dazzling array – which strongly resembled a buffet table, if you were one of the creatures in the next level up.
The meat eaters
When you think of marine carnivores, you probably think of sharks, crocodiles and pointy-toothed mosasaurs. They’re all in the list of carnivores found at the quarry, but you might find a few surprises, too: birds, shrimp, lobsters and even snails!
Technically speaking, you’re an omnivore – along with raccoons, bears, and other animals that can eat both meat and plants. The sea has omnivores, too, and we’ve found several at the quarry. You probably never thought of a graceful sea turtle as a “raccoon of the sea,” but that’s just one of the many surprises nature has in store when you start studying it.
The plant eaters
Since few plants grow on the sea floor, even fewer plant eaters live there. We have found one herbivore at the quarry so far, however – a dinosaur that lived on land, and probably floated out here after it died. Even if we never find another herbivore here, that one deserves its own category.