Treasures in Tide Pools

Typical tide pool at Larrabee State Park

Tide pools are used by invertebrates to overcome environmental challenges. They provide a sanctuary for various creatures such as crabs, hermit crabs, worms, and anemones. Tide pools are used to avoid one of the biggest threats in intertidal ecology – desiccation and heat. Tide pools, usually located at the supratidal fringe (covered only at highest tide) provide a way for invertebrates to avoid heat and desiccation. Some invertebrates, such as barnacles, simply aggregate to overcome this threat (interestingly, I noticed that they did not aggregate as much inside tide pools as outside. This is most likely because they do not face the same threat of desiccation). Others, such as annelids are forced to find water. At the supratidal fringe, disturbance is the biggest threat, rather than competition and predation at lower levels.

I went to Larrabee State park this morning to take a look at what the tide pools there had to offer. I stupidly went at high tide, so I had to wait a while, but when the tide lowered, the tide pool’s treasures were revealed. Unfortunately, my “dumb” phone’s camera is not a treasure. Please bear with me.

The most common invertebrate that I found in the tide pools was the Brachyuran (true crab). Of these, by far the most numerous was the Purple Shore Crab (Hemigrapsus Nudis).

Hemigrapsus Nudis, a common brachyuran. Brachyurans have 5 visible sets of legs and are referred to as true crabs. Anomurans, also known as hermit crabs, also have 5 sets of legs, but the last pair is not visible.

A less plentiful, larger brachyuran.

A few of the tide pools I looked at also had anomurans (hermit crabs). While these are not as common as brachyurans, they are still plentiful.

Typical Hermit Crab

My most exciting find was an annelid – somewhat uncommon in tide pools. These are usually found in the sand or underneath rocks at low tide. They resemble a segmented worm with parapedia (legs). I found a predatory one, most likely in the class Nereididae. I couldn’t get a picture of it because it swam away incredibly quickly.

A Nereididaen. Photo by Chris Moody.

Anthopleura Elegantissima.

The tide pools were also riddled with anthozoans (anenomes). Most of the ones I found were Anthopleura Ellegantisima, but I found one Anthopleura Xanthogrammica, which is invasive. Their fleshy bodies make them especially vulnerable to desiccation.

Anthopleura Xanthogrammica.

A Coenogastropoda species.

In many of the tide pools, I saw gastropods. I was able to identify 2 of the species by their clades, coenogastropoda (snails) and patellogastropoda (limpets).

Balanus Nubilus at Larrabee State Park.

Of course, I also found plenty of cirripedia (barnacles).

Taking Marine Invertebrates and their Environment has fueled an interest in marine invertebrates for me. Every time I go to the beach, I pray for low tide and hunt for invertebrates. I was never aware of how interesting they were until I started studying them. The diversity of life and adaptations these creatures take to survive is absolutely amazing.

I have only seen a glimpse of the life that these invertebrates live. I have seen them only in their defensive positions where they are most vulnerable. After 12pm, the tide will begin to creep up, and their lives will once again be shrouded in mystery.