If you’re afraid of what may be lurking in the shadows, never fear – Diadumene is here!

I, like most people, was introduced to anemones as the home of Nemo in Finding Nemo and I can now confirm that they are as cool as I thought they would be! A few weeks ago, I fulfilled my dream of encountering anemones up close as I dug around in some Jericho Beach tide pools looking for them, in the name of science. (If you’re looking for a fun weekend activity, you too can live the dream by turning over some cantaloupe-sized rocks in tide pools.) The species I studied is called Diadumene lineata, the orange-striped green anemone, and takes a few tries to locate since they’re usually only a few millimeters wide! 

When I was looking for them, it seemed like almost all of them were on the underside of the rocks in tide pools since I didn’t see too many anywhere else. If you’re looking for a new living arrangement, this location does not check off the box for natural light, but apparently anemones don’t care about that stuff? To see what was going on here, I went back and counted the number of anemones I could find in low light/dark habitats (like the undersides of rocks) and high light habitats (on top or on the sides of rocks exposed to light). 

Here’s what I found: these anemones seem to love hanging out in the dark! 

I brought some anemones home with me (not something I thought I would be saying) to see how they reacted to me annoying them in dark vs. light conditions. This consisted of me separating half of the anemones to be put in a tank exposed to high light (natural light on a sunny day) and the other half were in a tank exposed to low light (a very scientific towel covering the tank to reduce light). Then came the fun part: I poked the anemones until they closed up and folded their tentacles inside their body and then measured the amount of time it took for them to fully open back up.

I found that anemones were faster to open back up when they were in the low light tank. When they were in the tank exposed to high light, they took much longer to open back up. This may be because anemones, like university students during finals season, seem to stay up all night and eat. Anemones feeding at night may be why they were faster to react in the dark/low light environment, since they’re used to hunting for food in these conditions.

In closing, anemones are tough animals, great roommates, and aren’t afraid of the dark!

To fuel our invertebrate obsession, we took a (virtual) field trip to the Bamfield Marine Sciences Centre (BMSC) to see what lurks beneath the waves. We took a closer look using a subtidal dredge to get a sense of the benthic organisms inhabiting this region. A dredge acts like a basket that scoops up the contents of the sea floor, and in our case, is used to introduce students to local invertebrates. Invertebrates are divided into groups called phyla, so here’s a field guide!

1. Cnidaria: anemones, jellyfish, corals

This phylum gets its name from cells called cnidae, which are the reason you may end up in the ER after swimming next to a jellyfish. Cnidae are high-tech cells that shoot out a tiny sword-like structure delivering a sting in the process. In our dredge we found an orange cup coral, which is one of the few local coral species. 

2. Echinodermata: sea stars, sea cucumbers, sea urchins

Echinoderms have mastered the unique art of regeneration, which we noticed on a bat star found in our subtidal dredge. They are able to regenerate lost arms, even if they lose a large percentage of their body. Sea stars come in many shapes, sizes, and smells in the case of the leather star who could ward off vampires with their garlic smell. 

3. Mollusca: snails, mussels, octopuses 

Molluscs are a diverse group of mostly shelled organisms ranging from oysters to terrestrial snails. Moon snails, a marine snail, are unique parents as they are known to build an egg casing out of sand and mucus to act as a home for the eggs they lay. What initially looks like ocean plastic actually serves an integral purpose! Who knew?

4. Arthropoda: crabs, barnacles, lobsters

Arthropods are another diverse group of animals who are distinguishable by their hard exoskeleton. Since the sub-groups within arthropoda are quite different, they also exhibit different habits. For example, barnacles use suspension feeding in which they try to grab anything in the water column whereas crabs scavenge for food using their claws. A pretty wild looking animal we saw in our dredge was the decorator crab who tastefully wears tiny pieces of seaweed as a way to stylishly blend into their surroundings. 

5. Chordata: sea squirts/tunicates

The chordates we saw in our dredge were in the form of sea squirts (also called tunicates) and are actually the closest relation to humans of the invertebrates. Tunicates have similarities to vertebrates like us as we both start off life with a nerve cord (spinal cord in our case) but sea squirts lose this feature once they become adults. 

Sea stars are a charismatic member of local intertidal habitats, easily spotted by their bright colours and iconic star shape. If you’re an avid admirer of sea stars, you may have noticed it’s been more difficult to find them in the last few years due to a decline in their abundance around BC. Sea stars are in trouble because they are going through their own pandemic: sea star wasting disease (SSWD). A bit more physically noticeable than COVID-19, SSWD shows symptoms of white lesions on a sea star’s arms, severe tissue damage and sometimes causes arms to fall off all together.

Our research this week has focused on the lovable sea stars studying the performance of 2 species, Pisaster ochraceus and Evasterias troschelii, after placing them on different substrates. Sea star wasting disease is on my mind because our research was affected by this disease when it claimed some of our sea stars. 

Although we’ve been dealing with COVID-19 for about a year now, sea stars have become pros at social distancing since SSWD was first observed in 2013 in Howe Sound, BC. Unfortunately for sea stars, they won’t be receiving any vaccine shipments any time soon, but scientists are trying to determine the cause of SSWD. Right now, we know that warmer temperatures may provide a better environment for the disease to persist, so we can expect that marine heatwaves = bad for sea stars (and a lot of other organisms). 

A study by Dr. Drew Harvell at Cornell University in 2019 studied the sunflower sea star (creatively named since it has many arms comparable to sunflower petals) who have been hit hard by SSWD. They suggest that the disease could be linked to the sea star associated densovirus which when combined with warmer waters, becomes an issue for sea stars.   

SSWD is problematic for a few reasons: it’s influencing the health of the beautiful sea stars but also indirectly impacts their role in maintaining ecosystem relationships. Like a good friend, sea stars keep the individuals around them in check. Especially in the intertidal regions, sea stars are predators who keep prey population numbers at stable levels; essential for a working natural system. Remember those funky sunflower stars? They have gotten to such low numbers in some areas that we see a huge change in the rest of the ecosystem. 

Instead of balance, we now see that the sea urchins take over since they aren’t being eaten by sea stars, which also means the kelp preyed on by urchins gets decimated. It’s like when you try to pull out a piece in Jenga (removing sea stars from the ecosystem) and you end up causing the whole structure to collapse. 

So, hopefully you agree that sea stars are interesting and ecologically relevant animals! Here are some resources if you would like to continue to nerd out about sea stars:

Research by Dr. Drew Harvell et al. https://advances.sciencemag.org/content/5/1/eaau7042

https://kids.nationalgeographic.com/animals/invertebrates/facts/sea-star