Sites and Critters

Sea Lions as urban megafauna

Sea Lion pup in restaurant booth (c) Mike Aguilera

Sea Lion pup in restaurant booth (c) Mike Aguilera

The owners of the “Marine Room” restaurant in San Diego were certainly in for a surprise this morning, after an eight-month old sea lion pup found her way into their establishment overnight and decided to set up shop. She was quite obviously grumpy when a marine mammal rescue team arrived to take her away (right). You can read the full story and see the video of her deportation here from the LA Times.

(c) The Cave Store

(c) The Cave Store

Oddly enough, this was not the first strange sea lion encounter in San Diego this year. Back in January, another California Sea Lion pup (left) climbed up 145 steps from the beach below to colonize a gift shop in La Jolla; the desperado allegedly would only vacate the premises upon being bribed with salmon. In addition, this young sea lion decided to hitch a ride with a random paddle boarder near the Coronado Bridge back in October, though no ransom was reported for the high jacking:

If you’re thinking to yourself: ‘Why on Earth are sea lion pups moving into restaurants and gift shops?’ you’re not alone. Representatives from Sea World suggest that high tides and high sea surface temperatures associated with El Niño have reduced the food supply for California Sea Lions. Indeed, coastal areas in the Pacific have experienced abnormally warm temperatures as of late, and a recent paper from Bernardo Shirasago-Germán and colleagues in Mexico highlights that pups and young adults are particularly vulnerable to environmental fluctuations like higher sea surface temperatures. But further science on the matter has yet to hit the primary literature as far as I can tell. While the pup who found her way into the restaurant last night was apparently tiny for her age, it’s not clear to me whether her journey, and that of her gift shop- and paddleboard-invading comrades can be effectively linked to climate-induced food shortages.

(c) Takashi Hososhima

(c) Takashi Hososhima

Marine mammals may well serve as the canary in the coal mine for large-scale ecological changes in the ocean, but perhaps a different species would be a better representative for such an important task… one that’s not inherently so curious and unruly. California Sea Lions have lived and interacted with humans in heavily urban areas for as long as I can remember. When I was a girl, they took over a popular tourist destination in San Francisco and have remained in charge there ever since (left). In Seattle, they do just as they please on the buoys and barges operated by the port (at the top of this post). And when I’m underwater, they generally seem quite keen to make their presence known (below).

Perhaps it’s best to think of them like other urban wildlife, such as raccoons and coyotes – natural in a sense, but there in large part because of their ability to thrive in dense urban centers. This is all conjecture, of course, as much work would be needed to confirm whether California Sea Lions are indeed the type of generalist consumer the has adapted to urban life. Just something to ponder next time a sea lion wanders into your neighborhood coffee shop or corner market.

Big Ideas, Recent Research


Figure 1 from Loke et al. (2014) - A screenshot from CASU.

Figure 1 from Loke et al. (2014) – A screenshot from CASU.

Here’s a neat tool that could be of use to urban planners and restoration ecologists – CASU, the “Complexity for Artificial Substrates” program. CASU is open source software developed by Lynette Loke at the National University of Singapore and colleagues in Singapore, the Netherlands, Brazil, and the United Kingdom. The program allows users to design and visualize artificial substrates for urban waterfronts that are more complex than traditional, uniform surfaces we currently see on most bulkheads and seawalls. Since substrate complexity is tied to biodiversity of intertidal ecosystems, more complex substrates like those generated by CASU may serve as “ecological enhancements” for urban waterfronts.

Loke and colleagues originally developed CASU as part of a project aimed at increasing biodiversity on seawalls in Singapore using molded concrete tiles. By manipulating the topographic complexity of the tiles and deploying them in the field, they wanted to test whether more complex tile designs would increase the diversity of intertidal organisms. The problem is that you can define complexity in number of different ways. What specific aspects of habitat complexity actually affect intertidal diversity most and which are most important to include in your design?

CASU allows the user to modify 5 variables that affect complexity: (1) the number of object types, (2) relative abundance of object types, (3) density of objects, (4) variability and range in the objects’ dimensions, and (5) their spatial arrangement. In the case of their molded tiles, these 5 variables altered the arrangement and configuration of depressions in the tiles’ exposed surface (which are the “objects” that alter habitat complexity in their study).

Loke and colleagues describe CASU in further detail in a recent article in PLoS One. Indeed, after deploying their tiles in the field for 13 months, they did find that tiles with more complex surfaces supported greater diversity of intertidal organisms. Their subsequent work teasing apart which components of complexity are most influential for intertidal diversity on Singapore’s seawalls appears to be in press at the moment, so stay tuned for that. In the meantime though, you can download CASU using the links at the bottom of this page.

Figure 2 from Loke et al. (2014) - their caption reads: "3D models (AutoCAD drawings) of tiles with a single structural component (square-pits) at two levels of complexity generated via CASU. (A) ‘simple tile’ and (B) ‘complex tile’. (C) a fabricated 40×40×6 cm^3 concrete tile mounted onto a seawall (photograph taken one month after deployment)."

Figure 2 from Loke et al. (2014) – their caption reads: “3D models (AutoCAD drawings) of tiles with a single structural component (square-pits) at two levels of complexity generated via CASU. (A) ‘simple tile’ and (B) ‘complex tile’. (C) a fabricated 40×40×6 cm^3 concrete tile mounted onto a seawall (photograph taken one month after deployment).”


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.


Photo of hydroids
Recent Research

Hydroid assemblages in Spain’s harbors versus natural rocky habitats

Here’s a cool recent paper from Cesar Megina and colleagues: Harbours as marine habitats: hydroid assemblages on sea-walls compared with natural habitats. Megina et al. compared communities of hydroids in harbors and natural rocky habitats along the southern coast of Spain.

Photo of hydroids

Photo by Peter Southwood

Quick interlude – if you’re wondering what hydroids are, here’s a good overview.  They’re essentially colonies that grow in a vast variety of shapes, sizes and structures. The colonies are comprised of lots of little polyps, but often have a medusoid phase as well, like a jellyfish.

OK, back to the story… Cesar Megina and colleagues from Spain and Italy sampled hydroids at multiple harbors and natural rocky sites on the Iberian Peninsula. They found that hydroid assemblages in harbors tended to be comprised of species that formed small colonies and put a higher proportion of their energetic effort towards reproduction. Conversely, the hydroid species growing in natural rocky habitats away from cities tended to be those that form large colonies, put proportionally less effort into their reproductive stage, and have a greater capacity for competition with other benthic organisms for space.

Harbors also tended to support a higher proportion of non-indigenous hydroid species.  This is a finding that has been extended across multiple taxa and in several other parts of the world (I’ll post soon about a recent paper on this subject from the Pacific Northwest).

Megina et al. note that they were surprised to find high species richness of sessile hydroids in harbors in southern Spain.  As the field of urban marine ecology expands, it would be interesting to see whether this is a finding that carries over to other parts of the world.

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 ocean and riprap at dusk
Big Ideas, Ecosystem Services, Recent Research

Climate change and the proliferation of shoreline armoring

Louise Firth and colleagues recently published this article in Environmental Science Processes & Impacts: Climate change and adaptational impacts in coastal systems: the case of sea defences. It provides a brief exploration of shoreline armoring in the face of climate change. The general idea is this: as sea levels rise, coastal cities and developments are requiring increases in coastal defense structures (breakwaters, riprap, etc). These structures carry negative and potentially positive impacts for marine ecosystems. Why not construct them with these impacts in mind?

Photo of coastline with riprap and seawall

(c) Nigel Chadwick

“There is no doubt,” Firth and colleagues state in their paper, “that [armoring structures] modify the natural environment and can have deleterious impacts…” They cite research that has demonstrated how armoring structures act as stepping stones for species undergoing range expansions and how they have facilitated biological invasions. However, they may have potentially beneficial impacts as well, by supporting species of conservation importance and increasing habitat heterogeneity, as Firth et al. (2013) note.

So what does this mean for the construction of coastal defense structures? If the objective is to enhance intertidal biodiversity, Firth et al. (2013) provide these guidelines:

  • ”Build structure lower in the intertidal zone.”  Areas that are submerged for longer tend to support a greater number of species. Would this alter habitat that would otherwise be unaltered? That’s a discussion for another day I suppose.
  • Avoid smooth rocky material“, as these types of surfaces tend to be to be colonized by fewer species.  Specifically, they suggest a mixture of hard and soft rock to create greater surface roughness.
  • Create rock pools,” which should provide refuges for some species at low tide and support greater diversity.
  • Create pits” and crevices.  These provide hiding places and habitat heterogeneity.
  • Deploy precast habitat enhancement units.” Firth et al. (2013) note that a variety of such units are currently being tested around the world at the moment.  More on this soon in future posts!



Recent Research

Could jellyfish blooms be attributed to “ocean sprawl”?

Photo of Jellyfish by Ole Kils

Image by Ole Kils

You may have heard that jellyfish are taking over the world’s oceans, proliferating at a rate that is unfounded by historical standards.  Is it possible that this has been facilitated by the urbanization of coastal ecosystems?

This is the question posed by Carlos Duarte and colleagues in a recent a paper published in Frontiers in Ecology and the Environment (link). Many jellyfish have two life stages: the pelagic, medusoid phase that probably comes to mind when you think of jellyfish, and a juvenile stage in which they are attached to the bottom as tiny polyps. Most previous studies that have tried to explain recent increases in jellyfish abundance have focused on the pelagic stage.  Tiny polyps are hard to find, and have thus not been a central focus for research.

That is until now… Duarte and colleagues searched far and wide for the tiny creatures.  Where did they eventually find them? On the underside of floating docks, buoys, riprap and other artificial structures. They suggest that the proliferation of artificial structures (which they identify as “ocean sprawl”) is precisely what has allowed jellyfish populations to explode.

Many questions remain, of course, and much more must be done to see if their theory holds water. While Duarte et al. found that jellyfish polyps of some species favor shaded habitats, has the increase in shaded habitat associated with “ocean sprawl” really been sufficient to facilitate the types of increases we’ve seen in adult jellyfish populations? Does the trend extend to species they have yet to test experimentally? And can we actually find these polyps on our local floating docks prior to jellyfish blooms? All of this remains to be seen.

Map of population change in US coastal watersheds

Why Urban Marine Ecology?

Despite all my hype about urban marine ecology, it’s a field that really doesn’t exist yet. At least not in any standardized or formal way. It’s a discipline in the making, inspired by the explosion of research in terrestrial urban ecology and a void of comparable knowledge when it comes to the marine environment in cities.

You may have seen the statistics about coastal population growth. Overall, it’s estimated that we will reach a population of 8 billion in ten years. Currently about 50% of people live in coastal areas, but by 2025, it’s expected that that percentage will increase to 75%. That an estimated 6 million people living within 100km of a coastline!

The movement of people to coastal areas is not uniform. Check out this graphic from the National Oceanic and Atmospheric Administration (NOAA) of population change in coastal watersheds (link). From this, you can see that population in more rural coastal areas is actually decreasing. People aren’t just moving to the coasts. They’re moving to coastal cities.

What will be the effect of population growth on marine ecosystems?  We have no idea.  Not only are we limited in our understanding of what these will look like in the future – we know almost nothing about the characteristics of urban marine ecosystems today.  Much work is needed to characterize the biodiversity of these systems, understand their ecological processes and identify how they differ from their natural, more rural ecological counterparts.  In many respects, these are systems of our own making. Don’t you want to know what we’ve created?  I certainly do.  There’s much work ahead!