Marine Invertebrate Zoology Class Blog

For the last five weeks I’ve been the TA for Marine Invertebrate Zoology at FHL, taught by Gustav Paulay and Bernadette Holthuis.  One of the students’ assignments was to create a blog post about one animal, interaction, or activity from the course.  Our goal is to begin a record of marine invertebrates from the San Juan Islands that documents specific behaviors and appearances that may not be readily available in other online or text resources.

InvertZoology.wordpress.com

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Invertebrate Ball

06 July saw the return of the Invertebrate Ball to the San Juan Islands.  This annual celebration of invertebrates, marine biology and awkward dancing culminated in the Parade of Invertebrates through the FHL dining hall.  Best costume awards went to the Best Food Web Family, Best Rendition of a Cephalopod, and Best Pervertebrate, among others.

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Here’s me, an anemone protecting my symbiotic clownfish from two attacking mantis shrimp.

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Tritonia looking to feed on a juvenile sea pen.

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Red and purple urchins.

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Blanket octopus, horseshoe crab and an acoelomate.

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A pack of juvenile invertebrates.

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The Best Pervertebrate: Pluteus maximus

Diver for a Day

Friday Harbor Labs runs a Diver-for-a-Day program that brings students (typically elementary age) out on our R/V Centennial for a half day.  Divers don a full-face AGA mask with a wireless microphone to communicate with the boat and a tethered video camera to transmit video.  We go for a ~30min dive, showing the students around the undersea world.  The microphone system lets us speak directly with students, answer their questions while on the dive, and zoom the camera in on the things they get particularly interested in.

The trip begins with an introduction the equipment we use and a little about diving practices.

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Make sure to wear your halo.

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It’s a long way back to the surface.

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Eye to eye with the diver.

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Is everyone ok?

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Getting strapped in.

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While we’re underwater, here’s what the students see.

They sent us some great thank you cards too!

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Rockfish-Octopus Interactions

Last night I had the pleasure to give a talk about my research to a group of Shaw Islanders.  Part of this talk was an introduction to a research project I have planned for later this summer involving the interactions between octopus and rockfish.

This octopus project is funded by a generous donation from Robbie and Jan Macfarlane, Shaw Island residents who wished to establish and solidify connections between Shaw Islanders and the researchers at the UW Friday Harbor Labs.  The goal is to encourage researchers to build relationships with the Shaw community, and to include the Shaw community in the research taking place on their island and in their waters.  This connection began with my talk, and will also include a second talk on Shaw after the project finishes with the results we found.  I will also be posting updates here as the research progresses.  Robbie and Jan’s support allowed us to purchase several GoPro cameras which we will be using to record time-lapse videos of octopus and rockfish behavior in the wild.

This is a video I’ve posted before, and this individual is one of the octopus we’ll be following for this study (or at least whichever octopus is currently occupying this den).  Look closely at the end of the video and you’ll see a rockfish swim away from the front of the den as the octopus jumps in, and a tentacle snake out the back entrance to the den, which was chasing out a second rockfish.  These are the kinds of interactions we’ll be looking for – stay tuned for more info soon!

Red Sea Urchins

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Spines for defense and tube feet for moving, holding on and catching algae.

Strongylocentrotus franciscanus is the name for the red sea urchin, the most common mobile invertebrate we encounter.  Urchins are well known from temperate and tropical habitats around the world to be important herbivores.  In tropical oceans like the Bahamas, urchins help herbivorous fishes keep macroalgae (seaweed) at bay, allowing corals to grow.  In temperate oceans like California, Alaska, New Zealand and the Mediterranean, they are known to form foraging herds that can mow kelp forests down and replace them with “urchin barrens,” regions of coralline algae pavement and encrusting invertebrates.

The urchins of the San Juan Islands violate our preconceptions about urchins as important herbivores.  First, they don’t just eat algae, and second, even when they do, they don’t bother going to search for it.

Robin Elahi, a recent Ph.D. graduate from the Sebens Lab, studied the impact of red sea urchins on rock walls, and found them to consume lots of invertebrates, such as social ascidians.  Robin found that urchins are responsible for creating clearings on the walls by eating away space occupying species, and then chitons maintain these open patches by bulldozing or consuming new recruits.

When the urchins aren’t eating invertebrates, they’re waiting for algae to come to them.  The narrow channels between the San Juan Islands create strong tidal currents, which carrie drift algae back and forth through the channels.  Urchins sit and wait for drift algae to catch in their spines, rather than waste energy foraging for live kelp.  The result of this behavior is that urchins in the San Juans do not form massive herds that wipe out kelp beds.  The transport of this drift algae from the shallow productive zone allows urchins and other herbivores to live in much deeper habitats than they might otherwise be able to.  Several FHL researchers have studied various components of this relationship, including Sarah CarterKevin Britton-Simmons, and Aaron Galloway, a Ph.D. student in the Spatial Subsidy Lab at FHL.

Underwater Observatory

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Deployment and initial sampling with an observatory node. Photo: oceanobservatories.org

The Friday Harbor Labs is the testing site for a data collection node as part of the world’s largest ocean observatory network.  This node will be installed off of Cantilever Point, and will allow scientists to connect oceanographic probes, cameras and other data recorders.  This node is installed at 35m depth, shallow enough that it can be easily serviced by scuba divers to work out any kinks before the more extensive network gets installed at much deeper depths.  This network is part of the Ocean Observatories Initiative.

Sebens Lab divers (Derek Smith, Tim Dwyer and myself) have completed several dives to the test node site in preparation for its installation.  The node is powered and feeds information back to FHL by a cable connected to the seawater intake pumphouse.  The cable runs down a series of rocky ledges to a flat sand and shell hash bottom, where the node rests on a pallet, awaiting data recorders.  Initial testing will begin this summer.

The network was recently featured in a UW news article.

The test node is located off the point at the east edge of the FHL developed area. The pumphouse building is visible on the point at the bottom of this photo.

How to Measure a Current

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A clod card made of alabaster, adhered to an acrylic plate and strapped to a brick.

One of the simplest and cheapest ways to measure how much water moves by an area is to take advantage of materials that dissolve in water.  The faster water moves past the object, the more of the material will dissolve away, proportional to the exposed surface area of the object.  Materials that have been used for this purpose include plaster of paris, alabaster, and even Lifesavers.  These are typically called “clod cards” because the first ones consisted of clods of plaster attached to paper cards.

Our lab measures current flow with a combination of clod cards made of alabaster (inexpensive to produce, easy to deploy at many sites at once) with an Acoustic Doppler Velocimeter (very expensive, can only be deployed at one site at a time).

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Derek Smith building clod cards.

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Derek Smith and Cori Kane hauling a ton of bricks.

One of the disadvantages of clod cards is that they can only tell you about relative current flow.  That is, we can tell if Site A has faster flow than Site B, but not the actual average current speed at either site.  ADVs are able to measure three-dimensional water movement (“velocimeter”) by sending sound waves (“acoustic”) to bounce off of particles in the water.  When the echos from the sound waves return to the sensor, the ADV measures the doppler shift in the waves (“doppler”).  We pair clod cards with the ADV so we can approximately calibrate dissolution of the clod cards to an average current speed.

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Ryan Knowles installing the ADV (Photo by Megan Cook).

The white instrument at the top right is the actual measurement probe.  Sound waves emanate from the three prongs, bounce off of particles in the water, and are received at the midpoint of the instrument head.  The probe is elevated above the bottom so that we measure free-stream flow instead of the reduced current in the boundary layer.  The large yellow canister strapped to the cement base is the battery pack so it can record for weeks at a time.  One of the calibrating clod cards is off to the left.

Light Attenuation

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Without direct illumination from a strobe, underwater photos take on green or blue hues. These rocks are covered in bright red, orange and yellow organisms, but none of those colors appear unless we bring underwater flashlights.

Shallow coral reefs are bright and colorful.  The deep abyss is pitch black.  What about in between?

Light from the sun is composed of a spectrum of different wavelengths of energy, including visible light.  When white light passes into the ocean, these different wavelengths behave differently.  Some wavelengths are absorbed by the water very rapidly, and some are able to penetrate deep into the water.  Longer wavelenghts of light (red, orange, yellow) are absorbed more rapidly than shorter wavelengths.  If you descend in to clear open-ocean water everything looks blue:

Photo: oceanexplorer.noaa.gov

But in coastal water with lots of nutrients, like along the West Coast of the US, there are tons of phytoplankton in the water.  These phytoplankton absorb blue and red light, and reflect green light (the same reason why grass is green).  This turns coastal waters green instead of blue.

The only way to combat this light attenuation is to bring our own light sources.  We carry flashlights and camera strobes to help illuminate all of the colors in the Salish Sea:

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This photo was taken at about 20m depth. Without the camera strobe, all of these colors would appear as some shade of green.

 

Puget Sound King Crab

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The largest crab we see in the San Juans.  Not edible like the Alaskan king crabs, or at least I’ve never heard of them being harvested and eaten.

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Tim Dwyer, amazed at how large Puget Sound king crabs can get.  Despite the large, heavy claws, these crabs have never pinched us.  When we handle them they tend to tuck all their legs into the body.  This particular crab was scrabbling to find something to crawl away onto, not trying to menace the camera.

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Closeup of the face.  The spiky bits are part of one of the two pairs of the antennae.  You can see the other pair of antennae just above the spiky bit on the left.  The eyes are dead center, on either side of the triangular rostrum (looks like a nose).  The blue rectangular pieces are the 3rd maxillipeds, which help chew up food.  There are five other pairs of mouthparts, including the 2nd and 1st maxillipeds, the 2nd and 1st maxillae, and the mandibles.  All are involved in chewing and shoving food back into the mouth.

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Lopholithodes mandtii is an Anomuran crab, more closely related to the hermit crabs than to shore crabs or Dungeness and red rock crabs.  How to tell if a crab is an Anomuran or a Brachyuran (the group that includes typical crabs)?  Count the number of walking legs, including the pincers.  If it has 4 pairs it’s an Anomuran.  If it has 5 pairs, it’s a Brachyuran.  Another way to tell is to look at the abdomen (the shield on the ventral side of the crab).  If it’s asymmetrical it’s an Anomuran.

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Color in adults tend to be various shades of orange or red, with blue highlights.

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Juveniles are bright orange to red.

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Despite the bright coloration shown in these photos, Puget Sound king crabs are almost perfectly camouflaged.  The bright oranges and red are nearly invisible at the depths these crabs live (we tend to see them at 20m or deeper).  Without the bright colors, they look like all the other rocks they crawl over.  They only pop out when we use flashlights.