Keystone? Ecology, Not Architecture

Blog Post By: Chase, Sea Turtle Intern

A lot of the questions we get along our patrols are something along the lines of: "What makes sea turtles so important?"

Or, more simply: "Why do they matter?"

Surprisingly, we care about our sea turtles for many more reasons than their absolutely adorable babies. Although their cuteness plays a factor in our love, their importance to the world environment is much more motivating. Sea turtles are what's known as a keystone species. This means that the survival of their ecosystem is reliant on their species' survival. In other words, without the keystone species, the environments they occupy would be drastically different, or even cease to exist altogether.

The concept of a "keystone" species was bourne from research by Dr. Robert T. Paine. In his research, he removed one species entirely - the ochre starfish - from Tatoosh Island, off of the coast of Washington state. Within a year, biodiversity on the island dropped to half. With the ochre starfish in the environment, the beach contained 15 different species. Without it, 7 species disappeared entirely.

What happened on Tatoosh Island?

Dr. Paine's research quickly revealed how important the ochre starfish was to the island ecosystem. Without it, mussels and barnacles rapidly populated the shores, killing off a majority of the prey species on the island, as well as all but one species of algae. It turned out that the ochre starfish single-handedly (single-armedly?) controlled only the barnacles and the mussels' populations. By doing so, they also controlled the space available in their habitat, as well as the populations of all types of prey and plant life forms. One species of starfish is able to protect the entire ecosystem from collapsing - earning it the "keystone" title.

Keystone species define an entire ecosystem through complex webs of chain reactions. The disappearance of one animal causes more and more of them to disappear, until eventually, the ecosystem is totally different than it started.

Sea turtles provide a much similar ecological role, on a much larger scale. Sea turtles munch on seagrass beds, promoting the grasses' health, providing a shelter for fish all over the planet, and preventing seagrasses from overwhelming other plants' resources. At the same time, they also keep prey animals like jellyfish at bay, many of which feast primarily on fish eggs. No sea turtles means no fish, because the fish never hatch. Even more so, sea turtles also provide a food source for many animals both on land and in the water - sharks, birds, crabs, and more all rely on various parts of the sea turtle's life cycle as part of their diet.

Being a keystone species is a big deal. Sea turtles are our friends not just because we share an island, but because our oceans rely on them. We need sea turtles just as much as they need us.