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.

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This Week In The Lab

Soft sediments – they’re alive!!!

On Aug 3, I told you about the dives we’d done to collect soft sediments.  Tube of macrofauna in ethanolSince then I’ve spent many an hour in the lab processing the samples we collected.  Processing involves (1) quantifying the volume of riprap-originating algal material in each sample, (2) quantifying sediment grain size, (3) identifying each type of shell hash, and (4) identifying and counting all macrofauna.

Macrofauna are organisms that live in soft sediment.  Until just a few years ago, I had no idea how many critters actually live embedded in sand and mud. From above, the soft sediment landscape appears barren, almost devoid of life.  But it’s actually alive in a way I never imagined – at a tiny scale.  After many hours of picking through sand and mud in my sediment cores, I am again amazed at the density and diversity of macrofaunal life forms.  They come in all shapes and sizes, colors and textures, life histories and strategies.  Worms, clams, snails, amphipods, ostracods, sea cucumbers, and more!  It’s overwhelming.

For now, I’m simply pulling specimens out of sediment samples and storing them in ethanol (as in the photo), but I’ll be identifying them over the coming months and look forward to sharing.  Their stories are bazaar, amazing, surreal – from vicious hunters with exploding mouth parts to little arthropods that spend their entire lives moving about the seafloor in the organic equivalent of a hamster ball. I’ll highlight my favorites as they arise.  Stay tuned!

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