Exploring Oregon's Tidepools: A Guide to Common Marine Invertebrates

It’s said that 90% of animals on the planet are invertebrates so what are they and how do they all fit together? We’re going to look at this from a marine viewpoint, and use Oregon’s tide-pools as our environmental focus.

When most people think of ocean life, they may typically think of vertebrates, the large animals with backbones, like fish, dolphins, whales, seals, which often steal the show. But if you’ve ever spent time in tidepools along the Oregon Coast, beneath the waves or the tide line lie an even more diverse and fascinating world of creatures—marine invertebrates, or animals that don’t have a backbone. Anemones, sea stars, hermit crabs, mussels, clams, and so much more. These animals, which lack a backbone, make up the vast majority of life in the sea. From the tide pools to the deep sea, marine invertebrates are essential to healthy ocean ecosystems.

On land, invertebrates are animals like insects, spiders (arachnids), worms (annelids), snails (mollusks). In the sea, there are similar creatures plus some additional ones that are exclusive to marine habitats like star fish, sea urchins, etc.

In this post, we’ll explore some of the most common marine invertebrate phylums (major biological groupings), what makes them unique, and where you might encounter them. We’ll organize these marine invertebrate phyla from simplest to most complex, which is typically based on body structure, level of organization (e.g., presence of tissues, organs, symmetry), and nervous system development. This is one of my favorite topics in marine biology, and once you see how animals are similar despite their very different physical appearances, it can really help you understand how they all play a role in our diverse ecosystems!