Creature feature: Opalescent Nudibranch

One of the more beautiful creatures we find in our tidepools is the Opalescent Nudibranch or Hermissenda Crassicornis.  This organism has several adaptations (some of which I mentioned in an earlier post on Mollusks) that make it particularly interesting.  Most impressive is the nudibranch's ability to 'steal' stinging cells from its prey and pass them untriggered to the tips of its cerrata (the orange tipped structures on its back).    

Click to enlarge

As they live less than a year, they must go through their life cycle quickly and seem to do so without respect for the seasons.  Being hermaphrodites, nudibranchs can self-fertilize or mate with any other nudibranch of the same species though they usually choose the latter option (presumably to ensure the diversity of their gene pool).  

Another species, the Barnacle-eating Nudibranch, seen out of water

When tide-pooling, we often find opalescent nudibranchs close to the water line tucked away in rock crevices or sticking to pieces of kelp.  Searching amongst hydroids, one of their main food sources, is another way to increase the chances of an encounter with this nudibranch.  If you do find a sea slug and it is out of water, it is nice to have a small specimen jar or large clam shell that you can fill so as to observe the nudibranch in all its glory.  Be careful though, nudibranchs are delicate animals and cannot withstand rough handling.

Sources:
Monterey bay aquarium
Puget Sound Sealife

Eagles!

One of the cool things about Homer (and Alaska in general) is the number of Bald Eagles living here.  They are everywhere.  The first time I came to Homer in 2008 there was a woman dubbed "the eagle lady" who fed the eagles near the harbor.  As a result you would see them by the dozen sitting on pilings, along rock walls and on the tops of shops and homes.  She died later that year and there was legitimate concern as to what the eagles would do when deprived of one of their major food sources.  People with small dogs had to be particularly careful as eagles have been known to target them.  In the end they decided to continue feeding the Eagles through the winter and then slowly wean them off the unnatural food source.

Now, a few years removed from "the eagle lady", the eagles are still plentiful but are not as concentrated around the harbor.  Our country has perpetrated a few myths about eagles, portraying them as hunters descending on their prey with a mighty screech. While eagles do hunt for their food, consuming fish, birds or small mammals, they are also scavengers.  The best place in Homer to get photos of Bald Eagles is at the dump.  Eagles, along with the Glaucous winged gulls, are drawn to trash, dead animals and other easy meals.

As for the "mighty screech" that you often hear on TV, whoever first put eagles on film decided that the eagle's actual call was too wimpy to be associated with America's mascot.  Instead they dubbed in the voice of the Red Tailed Hawk which provides that classic screech. Here is a video of a Red Tailed Hawk's call, and here is a Bald Eagle's call.  The eagle's call is quite beautiful but it is not what you would expect from such a large, powerful bird.

Interestingly, the juvenile eagles often appear larger than the adults.  This is due to the juvenile's feathers which are longer and heavier than those on an adult eagle.  The juvenile feathers serve as "training wheels" while young eagles are learning to fly.  The adult's smaller feathers allow them to fly more gracefully and with greater maneuverability than the younger eagles.

Juvenile Eagle between two adults

Despite the cynical attitude I've treated eagles with in this post, I still stop an admire them when they soar past.  They add to the majesty of this place and it is a privilege to be able to see them with such frequency.

Fab four Phyla part four: Arthropoda

Arhtropoda is the largest and most diverse phlyum on Earth.  The pre-fix Athro refers to joints (as in arthritis) and pod means foot, so the name arthropod refers to animals with jointed feet or legs. The phylum arthropoda encompasses organisms such as insects, spiders and crustaceans.  Besides having jointed legs, athropods also have segmented bodies and a tough chitinous exoskeleton that they occasionally molt.  On our beaches we see mostly crustaceans; i.e. crab, shrimp and barnacles.

Black Clawed Cancer Crab
Its large claws are used to crush barnacles

Most people don't realize that barnacles are so closely related to crabs and shrimp.  Barnacles begin their life as a plankton and as they grow larger they change through various stages until they become a cyprid.  The cyprid's task is to find a good spot to settle on the sea floor and become a barnacle.  They land head first and begin to create a hard, 6 plated calcium shell around themselves.  To feed, they kick out their feet, which are shaped like tiny fans, and collect their food from the water.  We just recently had a barnacle fall out in our area and now everything is coated in the brittle white shells of young barnacles.  You feel bad crushing so many animals underfoot but our beaches are just so packed with life that it is impossible to do otherwise while tidepooling.

Empty molt of a helmet crab

There are several species of crabs on our beaches, though none of them are popular commercially.  Decorator crabs are my personal favorite.  Decorator crabs do not have large claws to protect themselves with, instead they rely on camouflage.  Using their narrow claws, they hang algae and other things from the tiny hooks on the carapace until the blend seamlessly into their environment.  It is nearly impossible to see a decorator crab unless it is moving.  Taking one out of water, they become spider-like, with long narrow legs and a proportionately small body.

A friend holding a decorator crab

Hermit crabs are another popular arthropod found on our beaches.  We have a few different varieties ranging in color from a drab brown to a brilliant orange.  Hermit crabs appropriate the empty shells of other organisms (usually snails) to give themselves additional protection.  Their body curls to fit into the shells and they have legs specifically adapted to hanging onto the shell.  One of their claws is generally over sized and acts as a shield to cover the entrance to their home.  We keep several large hermit crabs in our touch tanks at the field station and you can often watch them squabbling over new shells.

Helmet crabs mating

  At one point there were several species of crabs in Kachemak bay that were commercially important to Homer.  Tanner crabs, Dungeness crabs and King crabs could all be caught in the bay during the late 70's.  No one is exactly sure why the fisheries collapsed; whether it was due to mismanagement, a fuel spill, or just part of a natural cycle, these species no longer exist in Kachemak bay in harvestable numbers.  The Tanner crab and Dungeness crab populations are slowly recovering and hopefully they will continue to do so.

An Orange Hermit crab from our touch tanks

Gull Island

Just a short boat ride from the Homer Spit is Gull Island, a rookery for sea birds.  Gull island is home to more than 15,000 birds during the summer months when they come to nest.  There are eight different species that nest on gull island, including puffins, cormorants and murres.  

There are two species of gulls here.  The larger of the two is the Glaucous winged gull and the smaller is the Black Legged Kittiwake whose wingtips are black in addition to their legs.  Though these birds will scatter before an eagle, using their maneuverability they will often harass the predator from above to distract it from its intended prey.

When stirred up by an eagle or raven trying to hunt or steal eggs they will take off, en masse, swirling around in enormous flocks as the air fills with the sound of their keening.  When they squabble amongst themselves on the rocks, bickering over nest space, it sounds eerily like children screaming.

Islands like this form important habitats for nesting sea birds.  They need safe places to raise their young away from terrestrial predators.  Here they only have to contend with Eagles.  On the mainland they would need to worry about bears, coyotes and other smaller mammals like marmots.

The gulls and cormorants prefer to nest on the rock faces.  They glue bits of grass to the rock with their own feces which gives gull island a rather pungent smell.  Other species nest on different parts of the rock.  Common murres prefer to nest on top of the island, and puffins burrow tunnels into the narrow band of dirt between the grass and the hard rock of the cliff face.

Red face cormorants are in the center with
 murres to the right and  gulls to the left.

Though the gulls put on a spectacular show, most people are interested in the Red Faced Cormorants.  These are a fairly rare bird and are difficult to find in the wild.  Homer is the most accessible place in the world to see these birds whose habitat ranges down the Aleutian change and into parts of Japan.  We get birders from all over the world coming to see the cormorants so they can add something new to their bird lists.

 The two species of gulls are strong fliers and will get food by scavenging and diving to grab small fish off the surface. Other spercies, such as the puffin and the common murre, are excellent divers.  The murre can reach depths of over 600 feet.  Though they are poor and awkward flyers, they maneuver extraordinarily well underwater.  Before they nest, they form giant rafts in the water that can number in the thousands.  As a boat approaches, the murres at the outer edge will begin diving to get away; this begins a domino effect and creates a rippling wave of birds disappearing into the water.

Instead of flying to escape, these murres are diving into the water.

Fab four Phyla part three: Mollusca

An empty butter clam shell.
If you look closely, you can see a tiny snail laying eggs in the center of the shell.

  By many, this would be considered the most delicious of our fab four phyla. Mollusca is filled with edible organisms like clams, mussels, chitons, oysters, snails, octopus and squid.  People routinely go clam digging on the beaches here and there are several oyster farms around the bay as well.  It behooves people to harvest with care though; these animals, though numerous, are not unlimited in number and we can have a detrimental effect on their populations if we harvest unchecked.

A lined chiton, an organism that scrapes algae from rocks.

Mollusks are characterized by a having a strong muscular foot, a soft body, a mantle and usually, a shell.  Of the Mollusks we find on our beaches, it is the exceptions to the rule that people are most interested in.  The mollusks without shells are the flashiest and most interesting,  organisms such as nudibranchs and octopuses.  Nudibranch means "naked shell" and these organisms are commonly referred to as sea slugs.

The opalescent nudibranch.
The feathery cerrata on its back hold  scavenged nematocysts.

Nudibranchs have some truly amazing adaptations and seem to specialize in eating things that no other animals will.  One of our most beautiful nudibranchs, the opalescent nudibranch, eats sea anemones and passes their nematocysts (stinging cells) untriggered through its digestive system, places them on its own back adopts the nematocysts for its own defense.  Other species of nudibranch eat equally difficult prey; animals that are poisonous or seemingly undigestible are preferred by sea slugs.

Two (fully grown) opalescent nudibranchs.
There is a tiny snail just to the left of the nudibranchs.

Our other most popular mollusk, the octopus, is also without a shell.  Octopuses are the smartest invertebrates and are smarter than many mammals as well.  They can solve puzzles, learn from one another and even use tools.  On our beaches we have the giant pacific octopus, which nestles beneath rocks to wait for the tide to return. The ones we have are fairly small, no larger than 6-8 feet across.  As they grow larger, the octopuses will abandon their cramped dens and move out to deeper waters where their large size affords them some protection.  Eventually, over the course of just a few years, they may grow to have 20 foot arm spans and achieve weights of 160lbs.

Tentacles of a giant pacific octopus.
Notice the empty crab shells outside the den.

 The octopus dens on our beaches are fairly easy to spot because the entrances are often littered with the carcasses of their prey; crab, snail and clam shells lie broken and discarded at an octopus den's opening.  Usually we can only see a few tentacles but occasionally we will find a baby octopus under a rock or see one free swimming in the water.  They are extremely curious animals and will often shake 'hands' with you if you touch the water near the entrance of their dens.

Curiously poking around the entrance to its den.

Mollusks are a group of animals deserving of attention.  Not only are they a commercially and economically important group of animals but they are also important for the health of our bays and oceans.  Clams and mussels can filter upwards of 25 gallons of water a day keeping bays clean.  They are also an extremely important food source for both humans an animals.  For example, there is a tiny pelagic (mid water) snail called a pteropod that serves as the main food source for young salmon.  Mollusks are particularly at risk from ocean acidification which occurs as more and more released CO2 is absorbed into the oceans.  The excess of CO2 in the ocean forms carbonic acid which releases more H+ ions into the water and drops the ocean's ph level.  The acidification of the oceans hinders the formation of the calcium carbonate shells formed by nearly all mollusks and, if it continues, could see the collapse of many of the oceans food webs (including salmon that thrive on pelagic pteropods).  This is one of many environmental challenges facing the world today and it is one that is very deserving of our attention.

New Hobby - Fire dancing

Lene and I were at someone's birthday the other night and one of the guests turned out to be a fire dancer who brought her fire poi with her.  Fire poi are kevlar pads attached to chains with handles at the end for you to slip your fingers through.  The pads are dipped in fuel and once lit will burn for a couple of minutes.    She showed us a few things and let anyone who wanted to try them have a go.  I think both Lene and I are hooked now and we are looking to get a pair of our own to keep practicing with.

I snapped a bunch of pictures of everyone trying it out and miraculously no one set themselves on fire.  In the pictures everyone looks like an expert since who would be spinning chains of fire around if they didn't know what they were doing?

Fortunately, even if you hit yourself with one of the chains, they tend not to burn you (or leave scorch marks on your clothes).  We all tied our hair back as a precaution but other than that it felt pretty safe.  The whooshing noise the poi make as you whirl them around puts you in your own little world and its definitely an experience I would recommend to anyone who has the chance.

I'll try to get a video up later.

Fab four Phyla part one: Echinoderms

When we take groups out tidepooling they are going to see a lot of new and interesting animals and 80% of these animals fall into one of four different phyla.  Phyla are on of the levels of classification scientists use to  where the broadest group is a Kingdom and it increases in specificity until you reach the species level.  All together you have Kingdom, Phylum, Class, Order, Family, Genus, Species.  We rarely use scientific names when referring to animals but we like people to know the four main phyla that we see on our beaches.  Our fab four phyla are Cnidaria (anemones and jellies), Arthropoda (crabs, shrimp, barnacles), Echinodermata (urchins, stars, cucumbers) and Mollusca (clams, octopus, snails).

As the name implies, Brittle Stars lose their arms very easily

The first phyla I'd like to talk about is Echinodermata.  Echino means spiny (think of an echidna) and dermata refers to skin (as in a dermatologist) so Echinoderm translates to "spiny skin".  Sea urchins are the eponymous animal for this phyla and don't outwardly resemble their cousins, sea stars and sea cucumbers.  However, all Echinoderms share the distinct characteristics of pentaradial symmetry, the ability to regenerate, and water vascular system that enables them to move.  

A beautiful Rose star

For our groups, Sea stars are the most popular invertebrates and people are always excited to see them.  This works out since there are a lot of cool things we can show people about them.  Sea stars have a dot on their dorsal side called a madreporite or mother pore which serves as a hydraulic intake valve.  By pulling in water through this pore they are able to move their tube feet which act as tiny suction cups.  They use this hydraulic action to pull open mussels and clams and eat them.  Once they have a mussel shell open even a millimeter, the sea star will slide its stomach out of it's body and inside the mussel shell in order to eat it.  Sea stars also have tiny pinchers called pedicilleria which allow them to protect the gills that cover their dorsal side.  They don't want kelp or barnacles to settle on them and the pedicilleria defend this vulnerable spot.  These pinchers are strong enough to tear out arm hair (as I often demonstrate) or they can also be used to attach a sea star to a kid's fleece.

Stimpson's Sun Star

Urchins, the next member or this group, are not nearly as dangerous here as they are are in tropical waters.  Our urchins don't have poisonous spines and are completely safe to handle.  Urchins eat algae using their five teeth and their tube feet are extra long so they can extend past their spines.  Urchins are also capable of seeing color, though this ability is not well understood by scientists.  They have proven in experiments that urchins are able to associate color with food and that urchins can see the entire color spectrum but they are unable to figure out how the urchins can see.  

 

A True Star nestled amongst Green Urchins

The last member of the Echinoderms is the sea cucumber.  Although not readily apparent, sea cucumbers also have penta radial symmetry if you stand them on their ends like a cylinder.  They also have tube feet which they use to hang onto the rocks and mud they bury themselves in.  The cool fact about cucumbers that we quote endlessly to our groups is their ability to eviscerate themselves to distract predators.  They will spit out their guts as an offering/distraction if something is harassing them enough and then they will regrow their insides if given enough time.  Sea cucumbers eat by pushing their mouth parts out in a feathery fan which they can use to collect plankton and other detritus out of the water or mud.  

Sunflower Star

The largest member of the Echinoderms that we find in our tide pools is the sunflower star.  These stars can often reach three feet in diameter and have up to twenty four arms.  Compared to the other sea stars, sunflower stars are extremely soft because they are holding more water.  They use this extra water to operate more tube feet (over 15,000 of them!) and can move much faster than other sea stars because of this.  They are extremely voracious predators and will often eat other sea stars when given the chance.  Because their body is so soft, these creatures prefer the lower inter-tidal zone and cannot be out of water for very long.

Sunflower Star's tube feet

It's good to be back

I've been back in Alaska a little over a month now and while some things have changed, everything is still very familiar.  We've had our first round of groups and were lucky to have had phenomenal conditions; the sun was shining and we've already had the biggest tides of the year.  These ultra big tides give us a twenty eight and a half foot tidal variation which really must be seen to be believed.  Generally, over two days of tidepooling with good negative tides we will find anywhere between 65 and 100 different species.  These species can range from giant sunflower stars more than three feet across to tiny little tube worms the size of a rice grain.

Our dock on a big negative tide (you can touch the tops
 of those pilings on a really high tide).

We've had a few days off this past week for the Easter break; during the spring time we cater exclusively to school groups so our breaks coincided with Alaska's schools.  The timing couldn't have been better as Lene arrived from Norway shortly before Easter and just in time for both of our birthdays.  While I've been in town it's been fun catching up with people I haven't seen since I was last here and showing Lene around.  She's gotten herself a good used bike and is starting to learn her way around town.  I also took a refresher course for my cpr and first aid since my last course was a couple years ago.

Nearly full moon framed by the ghost forest

 We've also been checking out some of the bars and seeing some great live music, most notably from the Holy Santos Gang, a really amazing local band here in Homer.  I first saw them two years ago when I was last here and they were a great band then.  They are truly excellent now and I'm looking forward to seeing them play more often now that I'm back in Homer.

Sara posing for pictures instead of tidepooling

We are coming up on our big stretch of the season where we do most of our work and I'm hoping that everything goes smoothly.  The job is a lot of fun but it can be exhausting.  Our usual schedule has us getting up and starting to work with the group around 7:30 and though not obligated to, we often take the kids on evening hikes or arrange games for them to play by the campfire until they are in their yurts around 9:30pm.  School groups normally come out for two night stays at our field station and we will often work three groups in a row.

Pelagic cormorants and gulls in front of Poot's Peak

It's pretty funny when you've finally managed to tire a class out on their last day at the station and the boat that picks them up drops off a brand new school group full of energy.  As long as you stay healthy everything is good; getting sick is the biggest worry while working here since everyone is so busy it's hard to take a sick day.  Losing your voice is the worst since it becomes so much more difficult to control a bunch of fifth graders outside if you can't make yourself heard.  But I wouldn't keep coming back for more if I didn't love it and I do love living and working across the bay.

Transects! Go Data!

p.s.  I know I've been a little slack about updating, I'll try to keep the updates coming a little more frequently in the following months.

Hundreds of murres in the water off Gull Island
(enlarge this picture to see them all)

Homer, Alaska

I just arrived here in Alaska last week but things have been busy from the get go.  I'm in the town of Homer, on the Southern coast of Alaska, working for a non-profit called the Center for Alaskan Coastal Studies (CACS).  CACS focuses mostly on educational programs featuring the incredible forests and coastal regions around Homer.

Jackalof Bay, one of the sites we tidepool at

Homer is situated on Kachemak bay, just off of Cook Inlet, which has some of the biggest tidal differences in the world.  On extreme days there is a 28.5 foot vertical tidal change which makes for some incredibly dramatic and amazing tide-pooling.  There are two sites from which we run our programs; on the Homer side we have the Wynn Nature Center which has hiking trails running through some amazing spruce forests and is much easier for people to get to since it has road access.

Cooking dinner in dutch ovens up near the Wynn

The Peterson Bay Field Station on the other hand, is only accessible by a 30 minute boat ride across the bay and is where we do the majority of our school programs.  We have also contracted out to the Kasitsna Bay Laboratory, a facility run by NOAA and UAF, that allows us to take more school groups into the intertidal regions.

Kasitsna bay lab, an extremely nice facility

The first program I was able to jump in after I arrived was the last of our winter programs this year.  We had a group of girl scouts come out who participated in things such as survival skills, snow shoeing and star gazing.  Mostly I hung in the background, as these programs were new to me, and observed two naturalists here, Patrick and Jenni, do a really great job teaching.  The kids had a great time and learned a lot and so did I.  The day after we returned we were already preparing to head out again, this time to the Kasitsna bay lab where we had a small school group from Palmer, Alaska meeting us.

Building telescopes to look at the stars

In an unanticipated bonus, there was a Tribal Marine Science Workshop going on at the lab hosted by the Seldovia Village Tribe and due to a low attendance we were offered spots in the workshop.  Because of this, we went to the lab a couple days before our school group arrived so we could attend all of the lectures.  The lectures included topics such as the decline of the harbor seal population, oceanography, ocean acidification, paralytic shellfish poison, plankton and marine invertebrates.  We had experts and phd's from all over the place giving us these lectures and it was really an amazing experience.  There were also some good negative tides during the conference and we used the opportunity to head out to the beaches and examine possible scientific survey techniques.  I was pleased to find that I remembered most of the marine invertebrates that I had learned about during previous seasons working up here.

Laurel, one of our naturalists, bundled up to go tidepooling

Our school group consisted of just a few students from an advanced science course and when they arrived they attended the remaining lectures with us.  The kids were great and intellectually curious so it was a lot of fun to take them out tide pooling especially since one of them had never been on a boat before.  They were certainly a strange group though, as they were coming from a tiny private school that had less than 50 students and had only a single student comprising their senior class.  In the past I've had groups come from islands on the Aleutian chain where the entire school might be made up of six students.  Because things are so spread out here a lot of children end up being home schooled or going to small group schools with a wide range of ages.  They definitely interact with people a little differently coming from such small communities but when you get down to it they are just regular kids.

Good negative tides create a lot of places to explore

We were a little worried towards the end of our trip because the weather kicked up and flights and boat trips were cancelled going across the bay but in the end were able to make it out during a window of calm and had a nice trip back across the bay.  I head back across the bay in a couple of hours with a boy scout troop; the aim being to make sure our field station at Peterson Bay is up and running and ready to receive school groups.  Peterson Bay is where I'll be spending most of my time for the next five months and I'm really looking forward to getting back over there.

It was cold out there