Sites and Critters

Video tour of the underwater urban environment

As terrestrial beings, we often look out over an urban landscape and see the coastline as the city’s boundary. It’s hard to remember that there’s a whole world down there – a patchy landscape of riprap, sunken boats, used construction materials, discarded appliances, and networks of pipelines – all inhabited by a suite of creatures that are as adaptable to urbanization as the Norwegian rat, the raccoon, and the coyote. (Yes, coyotes are urban dwellers too! Link.) Below is another video diary of some of the habitats types and critters I commonly encounter underwater in Seattle.

The video starts with one of my favorite dive buddies – SCUBA instructor and diver extraordinaire, Rhoda Green. She’s in front of the grain terminal in the north side of Elliott Bay (you can see the Seattle skyline in the background). My video skills at this point certainly aren’t winning any awards, but my hope is to provide a sense of the variety of urban habitats we commonly encounter underwater. In order, you’ll see tire reefs, corrugated metal pipes, concrete slabs, and riprap. I then switched to common critters we see: Coonstripe shrimp (Pandalus danae), northern kelp crabs (Pugettia producta), the frosted nudibranch (Dirona albolineata), a large nereid polychaete worm, and the moon jelly (Aurelia aurelia). Enjoy!

Sites and Critters

Octopus Life, Death, and Birth at Three Tree Point

I wanted to briefly highlight the video below. It is the result of many months of hard work by Drew Collins, Myra Wisotzky, and others, to document the late life cycle of a particular giant Pacific octopus this winter. The individual they followed lived in a tire reef structure at Three Tree Point, just south of Seattle. The video is beautiful and the story compelling; it needs little introduction. Enjoy!

Sites and Critters, This Week In The Lab

Interns share their favorite critters

In the Sebens Lab in Seattle, we are very lucky to have a group of fantastic interns. This fall, we’ve been spending a lot of time sorting through sediment samples from an experiment we conducted in West Seattle last summer. After many, many hours in the lab, the Sebens Lab interns are true experts at finding and extracting worms, clams, and other critters in sediment samples. Inevitably when you’re doing this type of work, you come to favor certain organisms, be it for their beauty, their bizarre life history, their unusual appearance, or the ease with which you can find them within an expanse of similarly sized sand grains. For this post, two interns, Monisha Ray and Amy Green, have provided us with a look into their favorite soft sediment organisms and a description of what they like about them.

Monisha writes:

Photo of Monisha Ray

Monisha Ray, Sebens Lab Intern

One of the most interesting finds for me while processing our enrichment sediment samples was the presence of ostracods, tiny crustaceans that look like little reddish brown sesame seeds. Although they are related to shrimp, they have a clam-like resemblance due to the valves that enclose the rest of their body. These valves are made up of calcite or chitin. Usually the body of the ostracod ranges from 0.2 to 1mm, but the ostracods in our sediment analysis tended to be a bit larger (2-4mm) which was interesting to note. They were almost easy to overlook as some sort of marine seed, until upon closer examination the bivalved hinge becomes apparent as well as the sensory and swimming appendages protruding from within the carapace. Up to a third of the body of ostracods is dedicated to their reproductive organs, and the sperm of an ostracod can be up to 10 times the length of the body. Certain species of ostracods are also bioluminescent and produce a blue light that has been observed in Japan and Australia amongst other regions. Although the ones in our sample weren’t quite this spectacular, they were still an interesting find and a new encounter for me in my marine science experience. 

Photo of an ostracod

Ostracod, (c) Peter J. Bryant

Amy writes:

Photo of Amy Green

Amy Green, Sebens Lab Intern

My favorite infauna genus includes the Lacuna marine gastropod.  In the family Littorinidae, they are commonly known as chink shells.  They are found on eelgrass, rocks and seaweed low in the intertidal. They are herbivores and lay egg clusters that look like tiny donuts colored yellow or tan (kind of like spaghetti-Os). They have a thin shell with five to six whorls. The shell seems smooth to the naked eye, but has fine spiral ridges upon magnification. They usually have brown bands on whorls, but not always.  A study done by Chavanich and Harris (2001) in the Gulf of Maine found that L. vincta prefer Antithamnionella floccose, Ulva lactuca and Laminaria saccharina. These charismatic snails are my favorite because of their pretty banding, and cute squat shape.

Photo of Lacuna

Photo of Lacuna, (c) Amy Green

Check in soon for more postings on soft sediment organisms and our work in the lab. And thanks so much for reading!

Photo of Melibe leonine, copyright of Monterey Bay Aquarium
Sites and Critters

The hooded nudibranch

Two things are occurring right now that justify a posting about my favorite of all sea slugs, the hooded nudibranch (Melibe leonina). The first is that they have been all over Seattle waters in recent months.  The second is that they are the inspiration for my Halloween costume, which interns will have to put up with tomorrow in the lab.

Rhoda Green, my diving partner in crime, recently posted this great medley of Melbe leonina video footage:

In Rhoda’s video, you can see their interesting movements when they’re swimming.  It is common to see Melibe in doing these side to side movements in the water column, but eventually they settle in seagrass or kelp and get to their real purpose in life: feeding and mating. Melibe doesn’t have a radula like most other sea slugs. Instead, their large oral hood, which is lined with tentacles, closes around food particles like you see in the video. Like many gastropods, Melibe is hermaphroditic. Mating Melibes will reciprocally fertilize one another and then each lay coils of cream-colored eggs on the surface of eelgrass or kelp.

One of my favorite things about Melibe is that when you pull them out of the water and smell them, they have the undeniable scent of watermelon.  It’s not even an “essence” of watermelon or a “hint” of watermelon.  It’s like chewing Bubbalicious watermelon gum. Oddly, this smell at least in part results from the production of 2,6-dimethyl-5-heptenal and 2,6-dimethyl-5-heptonic acid, two chemicals the organism produces for defense purposes. I’m not sure why smelling like Bubbalicious would deter predators from gobbling you up, but apparently predators of the marine environment have different tastes than I do.

Photo of Eliza's Melibe leonina Halloween costume

My Halloween costume…

Clip art of rat
Sites and Critters

Rats in the intertidal

On many occasions, I see rats scurrying through riprap habitat in the intertidal. It’s kind of gross, particularly when you’re climbing through these boulder fields to get to your dive sites. Maybe it is because of this “gross” factor that I don’t usually mention rat sightings when I’m talking about what I do.  But the fact is that rats have been an undeniable part of urban ecosystems throughout human history.  In the intertidal riprap, they form extensive networks of burrows that I suspect are relatively undisturbed by human activities. What do they eat in their little waterfront colonies?  Is it possible that they rely on food resources from the marine environment?

Food web diagram from Kurle et al. (2008)

Food web from Kurle et al. (2008) of rats in the Aleutian Islands. Rats reduced seabird populations, which reduced predation pressure on grazing intertidal invertebrates, decreasing the abundance of algae.

I should say that while I’ve been seeing rats in the intertidal in Seattle for some time, it didn’t really occur to me to ask these questions until a recent conversation with Dr. Bob Paine at the University of Washington. He has been taking note of their presence in the intertidal for some time, and it was based on his suggestion that I began to consider rats as potential predators in urban marine ecosystems.

Indeed, there is some precedent for considering the role of rats in marine ecosystems. In 1993, Sergio Navarrete and Juan Castilla at Estación Costera de Investigaciones Marinas published a paper documenting predation by invasive Norway rats (Rattus norvegicus) on intertidal invertebrates in a marine reserve (link to Navarrete and Castilla 1993). They found that rats were particularly keen on keyhole limpets and crabs. In a more recent paper, Carolyn Kurle and colleagues documented the effects of predation by Norway rats on seabird eggs and chicks in the Aleutian Islands (link to Kurle et al. 2008).  Because seabirds feed on intertidal invertebrates, the presence of rats facilitated greater abundances of invertebrates and less dominance by algae, which invertebrate grazers controlled.

While I don’t see a lot of evidence of seabirds nesting in urban settings, the abundance of rats in the intertidal raises the question of how they may be impacting intertidal communities. Limpets and crabs are certainly potential prey items here, as are mussels, seaweeds, and a variety of other types of species.  Of course, it is possible that the plethora of food options provided to city rats by humans make intertidal organisms a minimal component of their diets despite how much time some of them may spend in intertidal habitats. For now, we can’t be sure.  Time permitting, it’s something I’d like to look at in future work.


Photo of noble sea lemon
Sites and Critters

The noble sea lemon

I took the photo above recently at Alki Pipeline, in West Seattle.  It’s a noble sea lemon, Peltodoris nobilis, and it’s larger than any other specimen I’ve ever seen, at almost 20 cm in length. According to Andy Lamb and Bernard Hanby, who wrote every Pacific Northwest Diver’s go-to companion, Marine Life of the Pacific Northwest, noble sea lemons can actually grow to be up to 25 cm long.

Photo of noble sea lemon eating a sponge

Photo by Marquis McMurray. Source:

Noble sea lemons are a type of nudibranch, or sea slug. Closely related to snails and terrestrial slugs, nudibranchs come in a striking array of beautiful and vibrant coloration patterns. Many have frilly (functional) adornments, such the darker-colored, fuzzy gill rosette you see here on the noble sea lemon’s back.  (The word nudibranch actually means “naked gills.”) In the front, it has two rhinophores to detect odors. Because nudibranchs have lost their shell, they have developed alternative methods of defense, including blending into their surroundings and harboring chemical toxins, which they may produce themselves or harvest from their prey and reuse.

Nobles sea lemons generally feed on sponges (and sometimes detritus), but individuals apparently have quite specific preferences when it comes to their favorite sponge species. This one on the right appears to have found its prey species of choice! I love this photo from Marquis McMurray – the noble sea lemon there is chowing down so intensely on a sponge that its face is almost completely is buried in it! From what we can tell, noble sea lemons gain chemical defenses (toxins) from the sponges they eat. When they’re eating sponges, they contain doridosine, a toxin that was found to be lethal when injected into shore crabs and mice.

We took the above photo at about 25 ft. While I didn’t see a lot of sponges in the vicinity, I’ll certainly be looking out for potential prey items of the noble sea lemon on future dives.

Photo of spotted ratfish
Sites and Critters

My friend the spotted ratfish

A few times recently when I’ve been out collecting sediment, I’ve had the feeling that I’m being followed.  Each time, I turn around and find one of these little guys in tow, hovering over the areas of sea floor that I’ve just disturbed by my sampling.  They’re called spotted ratfish (Hydrolagus colliei) and I’ve grown quite fond of them, despite their funny looks. They’re like my little underwater sidekicks, always interested in what I’m doing and standing by patiently as I do my work.  If the name weren’t already taken, I’d suggest we call them “dogfish” for their loyal underwater companionship.  But given their genus name, Hydrolagus (lagos means hare in Greek), I might instead just take to calling them water bunnies.

Photo of spotted ratfish

Photo by Linda Snook

Spotted ratfish are part of an ancient group of fish called Chimaeras, which are cartilaginous and most closely related to sharks. Their tails are long and skinny, providing limited propulsion. To swim, they instead flap their pectoral fins like a bird. They’re generally thought to favor crunchy foods like crabs and clams, but may also eat worms and other invertebrates in soft sediment. Similar to dogs, what keeps them hovering nearby is probably the hope that I’ll uncover something delicious as I’m sampling. Dog-like or not, though, I ignore the urge to reach out and pat them on the head. They have a venomous spine in front of their dorsal fin that can deliver a painful sting.

If ratfish look to you like weird mythological creatures concocted by the likes of Napoleon Dynamite, you wouldn’t be alone. The name Chimaera is, of course, borrowed from the Chimera in Greek mythology, a fire-breathing beast composed of parts from a snake, a lion, and a goat.  As wikipedia reports: “The term chimera has come to describe any mythical or fictional animal with parts taken from various animals, or to describe anything perceived as wildly imaginative or implausible.” I love that. Ratfish indeed look like the result of some wildly imaginative experiment, and it makes me love them all the more.

As I dive at sites around Seattle, even when I’m not collecting sediment, I’m amazed at how many spotted ratfish I see (at least 2-3 per dive). An article in the Seattle Times a few years ago highlighted the success of spotted ratfish in Puget Sound (article). Their population here is estimated at 200 million.  As Sandi Doughton, the author of the article, states, “that’s more than 30 [ratfish] for every woman, man and child in the state [of Washington].” Spotted ratfish have been a dominant species in bottom trawl surveys in Puget Sound for some time, particularly as other fish populations have plummeted. Information about their population trajectory is limited, but many believe that something about the changes we have made to the marine environment has provided this species with the conditions it needs to flourish and proliferate. Precisely what conditions these might be is unclear.


Sites and Critters

Underwater video tour of Alki Pipeline

If you live in a coastal city, there is likely a vibrant marine ecosystem just beyond the shoreline you see downtown. We so rarely get to peer into these ecosystems and so it’s easy to forget (or not even know) that they exist. Maybe this will help with that – this is an underwater video taken by my dive buddy, Ed Gullekson.  We shot the video at a dive site in Seattle called Alki Pipeline.  The site consists of a large pipe that is covered in boulders, or “riprap”, to prevent erosion. The boulders have provided rocky habitat for a wide variety of organisms, including giant Metridium anemones, a diversity of red macroalgae species, rockfish, and much more:

Subtidal riprap habitats are the main focus of my research. Specifically, I’m interested in understanding how ecological processes on riprap work and how the organisms growing on riprap affect surrounding soft sediment environments in cities.

This video was taken while swimming along a fixed bearing over the riprap installation at Alki Pipeline.  Originally, we were planning to use it as a means for documenting fish abundance and diversity, which we may still do.  But we realized it might also just be of interest for folks who want to see what it’s like down there.

Photograph of algae presses
Sites and Critters

Red macroalgae artwork… and some science

Algae presses are a cool and creative way to document macroalgal specimens you encounter in the field (and they make great gifts too!). These specimens came from a dive site near Centennial Park in Elliott Bay, Seattle. They represent some of the more common and dominant species I see growing on riprap. I made the presses by placing them on thick paper between two pieces of plywood held together by bolts that I then tightened as the algae dried.

These are presses of red algae species I commonly find on riprap in Seattle.  Tiny pieces of these algae are mixed into adjacent sediments.

These are presses of red algae species I commonly find on riprap in Seattle. Tiny pieces of these algae are mixed into adjacent sediments.

Riprap, the rocky material that makes up jetties, breakwaters, and seawalls, supports an abundance and wide diversity of red macroalgae.  One of the questions I’ve been most interested in testing is whether the red macroalgae growing on riprap get incorporated into neighboring soft sediments.  I recently collected sediment samples along transects extending perpendicularly from riprap installations (see earlier post), and I’m happy to say that I have a finding to report!  After weeks of sorting through the sediment samples, I have found that the amount of red macroalgae that is mixed into soft sediment decreases as you move away from riprap.

The next step is to identify whether these differences in algal content might influence the community of organisms that live in soft sediment.  In ecology, food webs that are altered by the influx of resources from adjacent habitats are said to be “subsidized” or influenced by “spatial subsidies.”  (I’ll write a post soon to give more background on the spatial subsidies literature.)

To test for spatial subsidies, I’ll be conducting field experiments in which I enrich soft sediment plots with fixed volumes of shredded red macroalgae. At the end of 8 and 16 weeks, I’ll be collecting core samples from these enrichment plots and testing for differences in community structure. More to come on that.  In the meantime, I’m excited to say riprap-originating algae do in fact make it to neighboring soft sediments… what is their affect there?  The answer to that is coming soon!