The Underwater World that Exists Just Below the Surface

From Expedition Guide Ashley Bolwerk, Wilderness Adventurer:


Most guests who arrive in Alaska for an Uncruise adventure, come with an extensive checklist of wildlife that they are hoping to see: bears, whales, eagles, etc. Most of these lists leave out the marine invertebrates that share the waters that we cruise on; yet many guests leave our adventures with a renewed fascination for our spineless neighbors.

The term invertebrate actually encompasses several different phylums of organisms that are far more diverse than our own vertebrate group. The vast differences between a human and a sea lamprey pale in comparison to the differences between groups of invertebrates. Aside from not having a backbone, many invertebrates have planktonic larval stages, and are otherwise completely unique from one another.

For example:

Echinoderms, which include sea stars, sea urchins, sea cucumbers, and sand dollars, tend to have penta-radial (five-part) symmetry, spiny skin, and tube feet.

Bryozoans, including crusting and branching forms of bryozoans are tiny, colonial animals that feed on plankton and are often viewed as white crust on kelps.

Cnidarians, which include anemones and jellyfish, have stinging tentacles to capture their prey and an incomplete digestive track, meaning food enters and leaves the body through the same opening.

Mollusks, which include mussels, clams, chitons, sea slugs, limpets, and snails, typically have one or more shells for protection (except sea slugs and the octopus relatives), a muscular foot for locomotion, and a rasping radula (except bivalves and octopus relatives) for feeding.

Porifera, which include sponges, have silica (glass) spicules inside their tissue that provide support and protection and have no symmetry (asymmetrical).

Annelids, include all of the marine relatives of terrestrial earth worms, which have segmented bodies, and small, hairy feet called setae. They, also often come outfitted with extravagant pinching, tearing, or sucking mouthparts and can produce large amounts of mucous.

Arthropods, are the largest and most diverse phylum of animals on the planet (roughly 80% of all described species) and include crabs, shrimp, barnacles, isopods, and amphipods. They have hard external skeletons that they must shed in order to grow, and their limbs are jointed. 

These and so many more organisms are visible during low tides while snorkeling, kayaking, skiff touring, or beach walking. The diversity of organisms rivals that of tropical reefs and the vibrant colors deeply contrast the grey rocks and sky that abound in Southeast Alaska. Every guest that I’ve ever taken on an invertebrate scavenger hunt has been left in awe of their unexpected beauty and variety. We all leave with a deeper love for the underwater, invertebrate-dominated world that exists just below the surface of the sea here in Southeast Alaska.