Lending an Ear to the Ocean

Conch shells are large so they provide a lot of surfaces for sounds to bounce around and amplify. These are often used to produce the “sound in a shell” phenomenon. Photo by Bob Peterson via Wikimedia commons.

Have you ever lifted a shell to your ear to hear the ocean? While it is nice to think that each shell is bringing memories of the ocean with it, what you are actually hearing is ambient sound from your environment bouncing off the surfaces of the inside of the shell. The noises are mixed together and amplified, and the result is a sound that reminds us of a wave.

While the ocean-in-a-shell is just a myth, the truth about sound in the ocean is far more amazing. Sound waves are pressure waves, and as the density of the substance they are moving through increases, the speed of the sound increases. Since water is denser than air, sound can move much faster in water than in air. That means sound is an excellent way to communicate over long distances in the ocean, and many animals have taken advantage of sound as a means to send messages.

The blue whale is the largest, and the loudest animal alive. It is louder than a jet engine! Photo courtesy of NOAA.

Whales and dolphins are some of the first animals we think of when it comes to communication in the ocean. Noises made by large whales are the loudest produced by any living animal. In fact, certain low-frequency whale calls can be transmitted across an entire ocean basin. The ability to produce noise that can travel so far is very helpful in the ocean, where whales must find each other despite being separated by large distances.

Snapping shrimps, such as this species from an island in the middle of the Atlantic Ocean, can produce very loud noises using their large claw. These noises are used to communicate and to stun prey. See the embedded video for a demonstration. Photo by Anker A., Grave S vie Wikimedia commons.

Large marine mammals are not the only ocean animals that use sound. Environments with a lot of activity, such as oyster reefs, are loud. Snapping shrimp and a variety of sounds produced by feeding animals can increase sound by as much as 30 decibels over an oyster reef. That is about the same amount of sound as an average human residence (ex. the intensity of “inside voices”). These reef noises may provide a cue for drifting oyster larvae that this would be a good place to settle (see Lillis et al. 2014). Other animals use cues from their environments to avoid areas that are dangerous. Crabs can detect sound and will stop feeding when researchers play noises generated by large predators (see Hughes et al. 2014). Scientists are just starting to understand all of the ways that animals use sound to transmit and receive information.

A research team applies an acoustic tag to a pilot whale. Photo by Ari S. Friedlaender via Wikimedia Commons.

Humans also use ocean sound to transmit and collect information. Acoustic tags are used to track movements of endangered species, such as the great white shark. These tags produce pinging noises that are picked up by receivers as the shark swims past. Receivers are often anchored at the entrances to bays and across the shallows of the ocean, but they may also be anchored or free-drifting in the open ocean. When a ping is picked up, the noise lets researchers know a shark is nearby, and specific characteristics of the noise let them know which shark it is. Through the movement of individuals we can start to understand migration patterns, behavior, and even which groups of sharks may be related to each other, based on where they go to breed. This is important to understand so we can protect the areas of the world that are most commonly used by these threatened animals, so they are still around for future generations.

In addition to understanding behavior, acoustic tags can help scientists and ocean resource managers learn if a marine protected area actually protects the animals it is designed to protect. Marine protected areas are areas where fishing and other human activities that remove or destroy marine life are prevented. These areas often support large numbers of fish that can then spill over into areas where fishing is allowed and support the livelihoods of fishermen in a sustainable manner. These areas are only effective if they protect fish long enough for them to breed and grow the population. We can track specific fish to see if they are using the areas that are protected from fishing, and how long they stay there (see Garcia et al. 2014). Depending on what we find out about fish movements, we can change the shape and size of the protected area to make it more effective.

Larger sound receivers, called hydrophones, can be used to pick up extremely loud noises, such as earthquakes. A sea-floor earthquake in 2004 caused most of the continental shelf off Sumatra to tumble into the ocean depths and resulted in a series of tsunamis that devastated coastal communities in the Indian Ocean. The sound of the earthquake (see below) was picked up by many hydrophones in the Indian Ocean, even thousands of kilometers away. Sounds from category 4 earthquakes are regularly heard across an entire ocean basin!

At certain depths sounds can travel across an entire ocean. The aptly named SOFAR channel is a depth at which sound waves, once they reach it, tend to stay and travel across entire ocean basins without losing much intensity. We put most of our hydrophones in this region so we can pick up the maximum number of sounds generated in the ocean.

Hydrophones are collecting sound signals all of the time, and sometimes they pick up very strange things. These noises are named and researchers try to determine what caused them. You can see some of the explained and unexplained noises here. As much as we would like them to be caused by some huge sea creature, often they are the result of glacial activity. For instance, take “The Bloop”. This noise was recorded in 1997 and was unexplained until very recently. People now believe it is the sound of a glacier breaking in half, because we have recordings of comparable, explainable glacial noise from the Southern Ocean. Listen to “The Bloop” here- it is not hard to understand how many thought that this was the noise of some sea creature.

This post is only the tip of the iceberg (pun intended) of all of the ways sound is used in the ocean. However, even this handful of examples is enough to develop an understanding of how important sound is in the marine realm. The idea that animals other than whales and dolphins can use sound to transmit information is fairly new, and we call it “soundscape ecology”. Soundscape ecology is bound to provide some unique insights into how animals collect information in an environment as vast and unpredictable as the ocean.

For more information:

Garcia, J., Y. Rousseau, H. Legrand, G. Saragoni, and P. Lenfant. 2014. Movement patterns of fish in a Martinique MPA: implications for marine reserve design. Marine Ecology Pogress Series 513:171-185.

Hughes, A.R., D.A. Mann, and D.L. Kimbro. 2014. Predatory fish sounds can alter crab foraging behavior and influence bivalve abundance. Proceedings of the Royal Society B 282(1802), DOI: 10.1098/rspb.2014.0715

Lillis, A., D.B. Eggleston, and D.R. Bohnenstiehl. 2014. Soundscape variation from a larval perspective: the case for habitat-associated sound as a settlement cue for weakly swimming estuarine larvae. Marine Ecology Progress Series 509:57-70.

Australia experiments

I am now finishing up my research projects in Australia, and since I have collected so much video while I’ve been working on my projects, I made a short video to explain some of what I have been doing at Macquarie University in Sydney, Australia.

My goal is to use oysters that have grown up in areas acidified by acid sulphate soils (a natural process that occurs in some parts of Australia) to understand how ocean acidification may impact an oyster’s ability to protect itself from crabs. Ocean acidification is expected to dissolve shell material, in much the same way chalk dissolves in vinegar, or teeth dissolve in soda. However it will be a slow process of acidification, so animals such as oysters may have time to get used to the extra acid in the system. In Australia, the oysters that grow up in areas with acid sulphate soils have had generations to adapt or acclimate to changes, so this is a great place to start. Will oysters that grew up in acidic conditions be eaten faster by predatory mud crabs? Or have they figured out some way to compensate? How might oysters respond to gradual changes in acidity, as is expected to happen world wide with climate change and ocean acidification? Hopefully after I analyze all of my data, I will have some answers.

Diving the Great Barrier Reef

I finally got around to editing some of the video from the dives I went on with my husband, Cal, on the Great Barrier Reef. Hope you enjoy them!

Diving in Cairns

Diving in Port Douglas

In addition to a LOT of blue coral (light was low so a lot of the colors didn’t come out), there are two sharks, a nudibranch, and great footage of a sea turtle at the very end.


Cal on the reef.
Cassie on the reef.
Whitetip reef shark.
Sixbar angel.
Giant clam.
Clown sweetlips.
Christmas tree worms! Pretty worms…
Moon wrasse.





Australia photos!

Photos from the rainforest- Daintree and Cape Tribulation, north of Cairns.

A rainforest waterfall.
Cassowary crossing!
Green crater lake. It is green because it is covered with teeny tiny pond plants.
Waterfall in the Aetherton Tablelands.
Cal and Cassie on the train.
This kookaburra sang to me!

These photos are from a crocodile farm we visited near Cairns.

Crocodile pile!
He’s angry…

To the zoo!

Belly scratch!
Little wallaby just wants some love!
Crocodile boat ride. Don’t tease the crocs!
Crocodile attack show. Sit… stay…
Cassowary at the zoo.

Daintree rainforest path.

Scary jungle bridge!
Cal doesn’t think the jungle bridge is so scary.
Fig trees in the rainforest.

Heading north to Cape Tribulation, where the rainforest meets the reef.

Beach where we stopped for fish and chips on our way to Cape Trib.
Mangrove where we went stick insect hunting.
Peppermint stick insect. I have no idea how we found it.
Peppermint stick insect, found only in one part of one park in Queensland.

Here are some photos from my visit to Canberra for my program orientation.

Role of Honour at the war memorial.
Australian war memorial.
First kangaroo sightings!

Spending some time in Sydney seeing all of the sights.

Look at that water. Coastal Sydney at its finest!
Sights on the walk from Coogee Beach to Bondi Beach.
Sydney Opera House.
Harbor bridge.

On my second trip to Canberra, I went to Tidbinbilla Nature Reserve and guess what I saw?!?!

Platypus! I took about a million pictures of water to get a few like this.
Young koala at Tidbinbilla.
A wild emu at Tidbinbilla.

While Cal was gone diving, I explored the city a bit more. Some nice people took this photo of me while I was walking the Harbor Bridge.

Me in Sydney.

Here is some video I took of Australian landscape from the car window.

Take that, personality test!

Collecting clams with my canine field assistant.
Collecting clams with my canine field assistant. Science involves a lot of “alone” time, and in this case, some frisbee-throwing.

In my second year of grad school I attended a seminar on personality, offered by William and Mary’s counseling office. I think the idea was to allow us to understand some of the reasons we find different situations challenging, since let’s face it, grad school is one big challenge and it helps to understand why we feel stressed or inadequate in certain situations. We were all asked to take the Myers-Briggs personality test in advance, which classifies you into a four letter code based on your answer to a series of questions. My code was an INTJ, which I have to admit fits me pretty well- I am an introvert, drawing energy from alone time and benefiting from time to think. I am fairly intuitive, and grasp large theories and ideas much quicker than details. I am a thinker, and I like to think things through logically, and will rarely follow through only on a “gut feeling”. Lastly, I fit into the “Judging” category (very strongly, I might add), because I prefer to make and stick with plans. It stresses me out to leave things to chance.

While the test clearly can’t encompass the entirety of human behavior, it can be helpful to explain why we feel the way we do in certain situations. For instance, in graduate school I realized that I was almost never able to raise my hand and answer questions first. It made me anxious that I was starting to fall behind, that I was not able to think and to come up with answers as well as my classmates. However, I learned that introverts frequently need more time to think things through before answering a question, so I don’t really worry about this aspect of my personality any more.

Me banding a bluebird nestling. See, I'm capable of attention to det... oh look! An eagle!
Me banding a bluebird nestling. See, I’m capable of attention to det… oh look! An eagle!

One thing that became abundantly clear in this seminar was that most of the scientists in the room fell into one category- ISTJ. These types are very similar to me, but with more attention to detail. About half of the graduate students fell into this category, and the rest of the students were just variations on this theme: ESTJ (extroverts, always the ones with their hands in the air first :) ), ISTP (very similar to ISTJs in the science field), or even myself, INTJ, stringing together big-picture ideas on the spot and then going home to make notecards to remember the little things that come so easily to ISTJs, like the names of authors or mathematical equations. I think ISTJ fits with the traditional image of a scientist- a nerdy loner on the quest for answers, always up to their eyeballs in obscure data- but the more I learn of what it takes to be a scientist, the more I am amazed that so many scientists have these characteristics.

Aww, look at those grad students trying to be social! Just kidding, my labmates and I always have a great time.
Aww, look at those grad students trying to be social! Just kidding, my labmates and I always have a great time.

Starting with the first letter in the personality test: the spectrum of I to E, introverts to extroverts. I think it is safe to assume that most scientists are introverts. I can’t speak to what it will be like in the later stages of my career, but I know that being a graduate student in science involves a lot of alone time. You must forge ahead on your own research project, oftentimes with very little help. However, increasingly scientists are called upon or even expected to exhibit very extroverted behaviors in order to succeed in their fields. These include increasing activity in the social sphere, not only on the web (through blogs, which is probably not too hard for most introverts), but in public (*shudder*). Scientists, just like everybody else, find jobs through networking, but I think for us the networking is best done face-to-face, which really throws us out of our comfort zone. A resume does not impress a potential collaborator as much as a discussion of new ideas. This can be extremely nerve-wracking for graduate students, who feel as though they must study a prospective employer’s current body of work, come up with a novel idea or a new direction to build off what this distinguished individual has already done, and convince this professor that you can add to their work and that they need you in their already under-funded lab, usually while you are at a conference and are already feeling very drained from all of the social interaction. Talk about being out of your comfort zone! It is no wonder that at most conferences, when I am interacting with a group of graduate students, we repeat the same tired conversation about the best way to approach scientists in a social situation. None of us know how, we just know that somehow this is a skill we will have to learn to get a job. A cover letter would be so much easier.

NSF EAPSI 2014 fellows at our orientation in Canberra.
NSF EAPSI 2014 fellows at our orientation in Canberra. Ready to engage in some international collaboration!

This leads me to my current activities as an international fellow at Macquarie University in Sydney. International collaborations such as this one are fantastic for my career. I get to expand the scope of my research, meet new people, gain a new perspective on science and environmental issues, and hopefully forge new collaborations that will make myself and my new friends at Macquarie University more competitive in marine science. In addition, I am truly loving my time in Australia, and I am making so many memories that will stick with me. However, my work here is really fantastic at putting me out of my comfort zone. I have planned an international research project involving field work in a system I do not know, for completion in facilities I do not know, with people I have never met. As a person who loves order, and making plans that do not change, the logistics have been a nightmare. Tomorrow I am driving four hours on the opposite side of the road, with three undergraduate volunteers, to a system I have never visited, to collect a species I have never collected before. I have no idea what I will find when I get there. I do however, know a couple of things to be true. First, I have prepared to the point that I know I will be able to make tomorrow a meaningful part of my experience in Australia, even if things go wrong. Second, I am going to leave my comfort zone behind, and as I have done many times in my career path as a marine ecologist, I am going to have the time of my life, showing myself I can overcome challenges to do something I never thought I would be able to do. Take that, personality test.

Great Barrier Reef in a Prickly Predicament

The Great Barrier Reef is arguably the largest living organism in the world. Arguably, because it is actually made up of billions of tiny organisms, that are themselves part animal, part plant, and part mineral. Coral polyps, the base unit of a coral reef, are colonial animals that look like teeny tiny anemones. Inside their skin they have algae that help them by making some extra food from sunlight. These algae are called xoozanthellae. The coral also secret a hard calcium carbonate skeleton, which (for hard corals at least) forms the base of the colony and helps the coral grow. Over thousands of year (8,000 to be exact) these tiny creatures have built a structure that can be seen from space. I have dreamed of seeing the reef ever since I was a child, and am so excited I got to dive on the reef as part of the first few weeks of my 10-week stay in Australia.

Clowning around.

After all of the time I have spent sitting in marine biology classes, I am well aware of all of the problems facing the Great Barrier Reef, including disease, pollution, and climate change, which causes the corals to lose their friendly algae, causing the corals to turn white, or “bleach”. However, after talking to some scientists at the Australian Institute of Marine Science this week, I have learned about another threat to coral reefs- starfish. A particular species of starfish, the crown of thorns starfish, is a very efficient predator of coral. In addition, it has a rather nasty habit of popping up every couple of decades in epidemic proportions. Nobody quite knows why, but it seems every 10 or so years the starfish show signs of increasing in numbers, and then are found everywhere on the reef, consuming coral and sending the Australian tourism business into episodes of head-hanging and hand-wringing anxiety.

Crown of thorns starfish lying in wait. They like to feed mainly at night. Like vampires.

As I mentioned, crown of thorns starfish are predators of coral. In fact, they are extremely effective and efficient predators of coral, perhaps even the perfect predator. Adult crown of thorns starfish start producing eggs when coral are getting ready to reproduce. Just as the corals are storing away extra nutrition for spawning, crown of thorns starfish come through and munch away at the extra-fat coral polyps, siphoning the food directly into their eggs. Then they release their eggs at the perfect time so that when the eggs hatch, the coral is spawning, releasing eggs and sperm into the water column that will serve as a buffet for the young crown of thorns starfish, which spend the first few days of their lives as plankton, drifting in the water and feeding on small things like coral eggs. Then when the crown of thorns starfish are adults, they continue to mow down the coral at a rate of 6 square meters per year. This doesn’t seem like much, but since they have millions of baby starfish each year, very few natural predators, and can live 6-8 years, they can consume quite a bit of coral. It is clear that this creature has evolved to become a very effective predator of coral, and it is understandable that people who depend on the reef for their livelihood are concerned about an outbreak of crown of thorns starfish.

Cassie and Cal being reef tourists.

What can be done? Some scientists are focusing on understanding what causes the starfish to reach epidemic proportions, so they can reverse or at least prevent outbreaks. One leading hypothesis is that pollution from land, especially extra nutrients, causes more young crown of thorns starfish to survive to adulthood, because there is more food for them. However, other scientists believe that crown of thorns outbreaks are simply natural phenonmenon that are caused by a slight change in water flow around the reef, which keeps more young starfish on the reef, instead of flushing them out to sea. Other researchers are focusing on an immediate fix for the crown of thorns starfish problem. They focus on developing a way to kill crown of thorns on the reef, and they have developed a lethal injection that will kill the starfish, but this method is expensive and would require a lot of man power. Other researchers are looking for deterrants or even attractants so we can keep starfish out of some areas or trap and remove them in large numbers. The trouble is that they will have to find an attractant/deterrant that works only for the crown of thorns, and not on any other starfish, because we are still concerned about keeping the other starfish that do not destroy the reefs healthy.

If this is likely a natural phenomenon, why should we care? While reefs may be able to bounce back from an outbreak of crown of thorns starfish, it is also just as likely that the other problems that plague the reef, including pollution, climate change, and other natural phenomena like storm events, may make it too difficult for coral to repopulate the reef. Certain coral species, and even certain reefs, may be lost.

So how likely is it that crown of thorns starfish will eat the Great Barrier Reef? The best coral reef scientists believe that the crown of thorns starfish numbers are increasing, and the last time this happened there was a severe outbreak within a few years, so many people are very concerned. I, for one, am glad I made it out to see the reef this year, and not a couple of years from now. The reefscape may look very different in just a few short years.

Adventures with Acidification

This summer I will be traveling to Australia to complete a research project sponsored by the National Science Foundation. Photo of me after I heard the news. Photo by C Glaspie.
This summer I will be traveling to Australia to complete a research project sponsored by the National Science Foundation. Photo of me after I heard the news. Photo by C Glaspie.

This morning I am making my last few travel plans for my next big adventure. In less than three weeks I will be boarding a plane for Sydney, to spend 10 weeks exploring and studying one of the most unique places on earth. Since I will be posting a lot about my research in Australia, this week’s topic will be an introduction of one of my main research interests, which also happens to be a very complex and serious issue facing the world’s oceans: ocean acidification. Get ready, I’m about to bust out some chemistry.

Ocean acidification is the process of the oceans becoming gradually more acidic, due to increasing levels of carbon dioxide in the atmosphere. This is how it works. As we hear almost every day, atmospheric concentrations of CO2 are increasing at an alarming rate. This is the driver of climate change. More CO2 in the atmosphere means that more CO2 will come in contact with ocean surface waters, where gas exchange occurs. After CO2 is dissolved in water, it takes part in a number of reactions. The products of these reactions are carbonic acid, bicarbonate, and the carbonate ion. There is, however, one other important byproduct of these reactions. At each step, hydrogen ions are lost into the water. More hydrogen ions in a liquid means the liquid become more acidic. The result is a decrease in seawater pH, because a lower pH means a solution is more acidic. Under some scenarios, if the current rate of CO2 emissions continues, we can expect a decrease in pH of 0.4 units by the end of the century. While this may not seem like a significant decrease in pH, it actually represents a three-fold increase in hydrogen ions.

Image of a newly-hatched Pacific cod. IT is easy to see how a young fish can be very sensitive to changes in it's environment.
Image of a newly-hatched Pacific cod. IT is easy to see how a young fish can be very sensitive to changes in it’s environment.

Acid can harm many organisms in the ocean. Fish gills are very sensitive to acidity, and more acid in the blood stream is, as you can imagine, very stressful. The main concern is usually for young life stages of many ocean species, because young animals are usually more sensitive to changes in the environment. In addition to the direct effect of acid, there are other, potentially more harmful consequences of ocean acidification. For example, carbonate ions are a natural buffer for seawater. They are the Tums of the ocean- just as Tums help relieve extra acid in your stomach, carbonate ions help eliminate extra acid in the ocean. As ocean acidification continues, the result is a loss of carbonate ions from the ocean. By the end of the century, there may be 60% fewer carbonate ions in the ocean. This means there will be less “Tums” to rid the ocean of extra acidity.

I addition to acting as Tums, carbonate ions are one of the building blocks for shell material. As carbonate ions get used up to buffer acid in the ocean, there are less carbonate ions available for the animals that need them to build hard shells, such as crabs, clams, oysters, corals, and some plankton which form the base of the ocean food web. Not only will there be less material for them to use to build shells, but if the oceans get acidic enough shell material may even begin to dissolve away, just as Tums dissolve in your stomach. Hard shells protect and provide structure for these animals. If the shells weaken or dissolve, these animals cannot grow and are less likely to survive an attack by a predator.

Coral reefs are built on top of layers of hard shell secreted by the corals. This material is at risk of dissolving in acidified ocean water. Photo By U.S. Fish and Wildlife Service Headquarters (Coral Reef  Uploaded by Dolovis) [CC-BY-2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons.
Coral reefs are built on top of layers of hard shell secreted by the corals. This material is at risk of dissolving in acidified ocean water. Photo By U.S. Fish and Wildlife Service Headquarters (Coral Reef Uploaded by Dolovis) [CC-BY-2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons.
Despite the importance and complexity of this issue, relatively little research has been done on ocean acidification. Besides coral, which has been studied extensively, few species have been included in ocean acidification experiments. Many studies experiment with extremely low pH values which have dramatic effects on animals, but are unlikely to be seen in the oceans in the next century. Perhaps the greatest problem is the lack of long-term ocean acidification studies. Most of the research that has been done covers a period of less than 7 days. Such a short-term study is not adequate to understand the effects that ocean acidification may have over an organism’s lifetime, let alone the effect it might have on generations of animals that have a chance to adapt to change.

A photo of jarosite, a mineral that forms in acid-sulphate soils (soils acidified by iron and sulphides). Photo by Rodney Burton [CC-BY-SA-2.0 (http://creativecommons.org/licenses/by-sa/2.0)], via Wikimedia Commons.
A photo of jarosite, a mineral that forms in acid-sulphate soils (soils acidified by iron and sulphides). Photo by Rodney Burton [CC-BY-SA-2.0 (http://creativecommons.org/licenses/by-sa/2.0)], via Wikimedia Commons.
There are some places in the world that are already experiencing acidification on a small scale, due to a variety of natural (and sometimes unnatural) phenomena. This acidification occurs in polluted bays, at carbon dioxide seeps, around deep-sea volcanoes, and on the East coast of Australia, where acidic soil rinses acid into coastal waters. In Australia, acidification from acid soil is a natural process that has been going on for the last 10,000 years. The acidic soils form when iron-rich sediment is exposed to seawater, which then evaporates or recedes and leaves behind sulfide, a substance that is naturally found in seawater. The sulphide combines with iron to form iron-sulphide sediments. When this sediment is dried out and exposed to oxygen, the iron sulphides undergo a chemical reaction to form sulphuric acid. Then every time it rains or the tide comes in, all of that sulphuric acid is washed into the coastal water. The animals that live there must find a way to adapt to the acid in the water, or they will die.

Sydeny rock oysters, the species I will be studying while in Australia. Photo from Wikimedia Commons, by Stevage.
Sydeny rock oysters, the species I will be studying while in Australia. Photo from Wikimedia Commons, by Stevage.

While I am in Australia I will be taking a look at the communities of oysters living in the acidic bays and estuaries near Sydney, to see if they have been able to adapt to the long-term acidification of Australian coastal waters. Since my interests lie in predator-prey interactions, I will be looking at how oysters and crabs interact, and whether oyster shells are weaker and result in more acidified oysters being eaten by crabs. This study in Australia will serve as a natural experiment to help scientists understand the effect of the slow process of ocean acidification on animals as they adapt to their environment from generation to generation. It is important to understand the effects of ocean acidification because if some shellfish species are going to have a hard time, commercial shellfish farmers and harvesters may find their livelihoods threatened. Fisheries aside, plenty of animals have shells. These animals are an important component of the food web, and figuring out which ones are likely to disappear from the ocean will help us to predict if there will be large changes to the flow of energy in the ocean.

In the meantime, I will share some stories about my research and my travels in Australia this summer. Australia is full of unique landscapes and creatures, so I will undoubtedly have some cool facts that I pick up along the way, and share with all of you on my blog. Stay tuned for some adventures on the reef and in the mangrove.

Photo of a goblin shark captured in Japan.

Goblins and isopods and whales, oh my!

Head of a goblin shark. By Dianne Bray / Museum Victoria [CC-BY-3.0 (http://creativecommons.org/licenses/by/3.0)]
Head of a goblin shark. By Dianne Bray / Museum Victoria [CC-BY-3.0 (http://creativecommons.org/licenses/by/3.0)]
Last week the discovery of a goblin shark in the Gulf of Mexico made headlines. This is only the second record of a goblin shark in the Gulf of Mexico. The goblin shark is a deep-sea species that is very rare. Most specimens come from Japan, but even there it is still not common. Scientists know almost nothing about this shark, including why it looks the way it does, how old it gets, how large it gets, or anything about goblin shark reproduction. Until 2000, when the first Gulf of Mexico goblin shark was caught, scientists didn’t even know it existed in the Gulf of Mexico. This truly was an amazing discovery, but then researchers started looking closer at the fisherman’s catch.

Underside of a deep-sea isopod captured from the Gulf of Mexico.
Underside of a deep-sea isopod captured from the Gulf of Mexico.

If you look closely at the photos of the catch, you may notice some giant creatures that look like lobster tails or pill bugs. These are deep-sea isopods, and they are about the size of a house cat. Since I have an unreasonable fear of cockroaches, these isopods naturally give me the heeby-jeebies, but there is no doubt that they are cool. These isopods are not really uncommon, but they are never found in such large numbers unless a really tasty food source is around, and such decadence is hard to come by in the deep sea. This led some scientists to suggest that the fisherman’s trawl net may have passed over something very rare and very interesting- a whale fall.

A whale fall is what happens after a whale dies. Sometimes whales float for a while after they die, but they all inevitably sink. Even most beached whales are eventually dragged out to sea to sink. Whales rest at the bottom of the ocean and provide an opportunity for lots of food in a landscape that normally does not have any. As a result, whale falls draw a number of unique species, including some that live around very rare deep-sea habitats like hydrothermal vents and cold seeps. They also draw some species that specifically feed on bone, meaning they can only be found at whale falls. This video is a great artistic representation of what happens in the deep sea when a whale arrives.

Sleeper shark captured on camera by a NOAA Okeanos mission.
Sleeper shark captured on camera by a NOAA Okeanos mission.

Whale falls can be broken up into different stages, each with their own group of animals. The first stage attracts crustaceans such as the squat lobster, hagfish, and large sharks like the sleeper shark. This stage may last anywhere from four months to two years. The second stage invites a variety of animals that live in the soil or on the bones, eating increasingly hard-to-digest material to make use of the rare appearance of nutritious food in the barren deep sea. This stage lasts about the same amount of time as phase one (months to years). In the third stage, species that use sulphide as an energy source instead of the sun, such as those found around hydrothermal vents, appear around the whale. Sulfide is a compound made of sulphur that builds up when bacteria are very active, and causes the rotten egg smell you may notice when passing a marsh. This phase may last from six years to decades.

The following video offers some great footage of a whale fall caught on camera by a deep-sea submersible:

Skeleton of a 35-ton, 13-m gray whale on the sea bottom. Ribbon-like animals are hagfish.
Skeleton of a 35-ton, 13-m gray whale on the sea bottom. Ribbon-like animals are hagfish.

Whale falls are notoriously hard to find, because the deep sea is so vastly large (139,000,000 square miles). When researchers find a whale fall, it is a big deal. When they find a whale fall in an ocean as remote as the Southern Ocean (the ocean surrounding Antarctica), it is an even bigger deal. In 2013 researchers found a whale fall near Antarctica, the first discovery of its kind. The Antarctic whale was home to nine species we had never seen before. As amazing as this discovery was, scientists that study whale falls do not have the time or money to comb the deep sea, so they take a shortcut- they sink beached whales, and monitor their progress over time. Researchers in Japan tracked 12 whale carcasses over three and a half years. In the Japanese whale experiments, two new species were discovered, one a lancelet (a primitive fish, and one of my favorite critters), and one a new species of bone-eating worm. If they continue to monitor the whale falls, it is possible they may find even more unique species. Even after three and a half years, there was still some blubber and tissue present, so the decomposition process was nowhere near complete and other groups of animals are still likely to move in.

While locating a whale fall is an extremely rare occurrence, that does not mean that whale falls are uncommon. By doing some quick math to calculate the number of whales estimated to be in the ocean, then factoring in the number that are likely to die in the next year or so (about 1%), as well as an estimate of how long it takes for a whale carcass to disappear (at least 6 years), you can give a reasonable estimate of the number of whale falls currently in the ocean (a little over 100,000 whale falls). Factoring in the total area of the ocean, that means one whale fall every 1,300 square miles. That seems like a lot of area to search for a whale fall. However, think of it this way. Say you are planning a trip across the Atlantic Ocean, and are taking a ship from New York to London (3,500 miles). While on the ship, your path line along the ocean floor is likely passing within one mile of about 10 whale falls. You may have been right on top of one of these unique communities, perhaps full of goblin sharks and deep-sea isopods, and never even knew.

This figure is a representation of the number of whale falls on the sea floor. It is not to-scale. All whale data was obtained from the International Whaling Commission or NOAA. The figure is for demonstrative purposes only, and is not intended to be used as scientific evidence. Calculations and figure by Cassandra Glaspie, 2014.
This figure is a representation of the number of whale falls on the sea floor. It is not to-scale. All whale data was obtained from the International Whaling Commission or NOAA. The figure is for demonstrative purposes only, and is not intended to be used as scientific evidence. Calculations and figure by Cassandra Glaspie, 2014.

For more information:

Amon, D.J., A.G. Glover, H. Wiklund, L. Marsh, K. Linse, A.D. Rogers, and J.T. Copley. 2013. The discovery of a natural whale fall in the Antarctic deep sea. Deep-Sea Research II 92:86-96.

Fujiwara, Y., M. Kawato, T. Yamamoto, T. Yamanaka, W. Sato-Okoshi, C. Noda, S. Tsuchida, T. Komai, S.S. Cubelio, T. Sasaki, K. Jacobsen, K. Kubokawa, K. Fujikura, T. Maruyama, Y. Furushima, K. Okoshi, H. Miyake, M. Miyazaki, Y. Nogi, A. Yatabe, and T. Okutani. 2007. Three-year investigations into sperm whale-fall ecosystems in Japan. Marine Ecology 28:219-232.

The king crab regains the throne

Red king crab at the Kodiak Lab. Photo by Cassandra Glaspie.
Red king crab at the Kodiak Lab. Photo by Cassandra Glaspie.

In 2008 I got the chance to travel to Kodiak, Alaska for an entire summer of research on the red king crab. Researchers were concerned that global change would threaten an economically important and thriving fishery around the Aleutian Islands. The poles are warming faster than anywhere else in the world. In addition, waters are gradually becoming more acidic in a process called ocean acidification, which is caused by increased uptake of carbon dioxide in ocean waters. Ocean acidification was my specific area of research as an intern in Kodiak. I was responsible for trying to figure out the effect of acidified water on the young life stages of the red king crab. The assumption was in this area of the world, global climate change would cause problems for this cold-water species of crab. However, that is not the assumption everywhere in the world.

This is what Antarctica would look like without ice. The light blue is the continental shelf, which quickly drops away (continental shelf) to deep ocean in dark blue. Image from BEDMAP Consortium/British Antarctic Survey.
This is what Antarctica would look like without ice. The light blue is the continental shelf, which quickly drops away (continental shelf) to deep ocean in dark blue. Image from BEDMAP Consortium/British Antarctic Survey.

Some species benefit from warming waters. A large part of the Antarctic continental shelf (or the shallow waters that fringe the land mass that is Antarctica), is off limits to many species because it is simply too cold. In very cold places like Antarctica, the water at the ocean’s surface is actually colder than the deep water because the air temperature cools the surface water. So in Antarctica, many species aren’t able to live and grow in the shallow waters, even though they are abundant in the deep water offshore of the continental shelf. This is the case for many species of large crabs with crushing claws, that are abundant in the colder waters near the North Pole and Alaska, like king crabs. King crabs are the crabs of “Deadliest Catch” fame.

Antarctic corals. Photo by Zapata-Guardiola y López-González.
Antarctic corals. Photo by Zapata-Guardiola y López-González.

The shallow waters of Antarctica have been too cold for crushing crabs for 14 million years. As far as crustaceans on the Antarctic continental shelf go, currently there are only five shrimp species that are able to survive in the colder, shallower waters around Antarctica. The absence of large crab predators is very important to the bottom-dwelling critters in Antarctica. Large crabs not only tear apart and crush prey they find while foraging on the ocean floor, they also produce gashes and holes in the surface of the mud at the bottom of the ocean. This is a lot of disturbance. Since the shallow waters of Antarctica have been free of many crab and fish predators for so long, they have developed some of the most diverse communities of starfish, corals, and mollusks found anywhere in the world. More than half of all the species found on the Antarctic shelf are endemic to the area, meaning they are found nowhere else in the world.

Antarctic snail Pleurotomella endeavourensis, reproduced courtesy of Museum of New Zealand Te Papa Tongarewa under a CC BY-NC-ND license.
Antarctic snail Pleurotomella endeavourensis, reproduced courtesy of Museum of New Zealand Te Papa Tongarewa under a CC BY-NC-ND license.

The animals that live on the floor of the Antarctic shelf have evolved to withstand fairly constant conditions, with not much disturbance. The major predators of the Antarctic shelf are slow-moving predators like starfish and urchins. That means the clams, snails, corals, and other invertebrates that live on the Antarctic shelf are relatively unprotected: thin-shelled, slow-moving, and non-toxic. Examples include thin, almost translucent snails; fragile, fleshy gorgonian corals; meaty, lumpy clams that divers can collect by hand; and white nudibranchs (shell-less snails) that do not collect poisons from their food like their coral reef-dwelling cousins. These animals would likely not do very well if a new, relatively quick predator with crushing claws and pointy, probing feet were introduced onto the continental shelf. Which, of course, is exactly what is happening.

Sea surface temperatures on the west Antarctic Peninsula have risen about 1° C since 1950. Observations made by deep-sea submersibles suggested that this temperature increase may have been enough to allow king crabs to move from the deep water surrounding the Antarctic continental shelf, up the slope, and closer to the continental shelf itself. A team of researchers traveled to Antarctica to document king crab presence on the slope, and to see how close the crabs were to reaching the shelf. This video summarizes what they found.

Two king crabs photographed in Palmer Deep. Photo by: Katrien Heirman, published in Smith et al. 2012.
Two king crabs photographed in Palmer Deep. Photo by: Katrien Heirman, published in Smith et al. 2012.

King crabs were spotted on the lower portion of the continental shelf. Crabs were seen actively consuming starfish and other bottom-dwelling animals, and diversity of other animals was reduced in areas where crabs were abundant. An additional survey of the Antarctic continental shelf in 2012 revealed populations of king crabs in the deeper portions of the shelf itself. In fact, a team of researchers recently discovered a healthy population in a deep basin called Palmer Deep, 120 km away from the slope, indicating that the crabs can cross the shelf already. The amount of crabs found in Palmer Deep is greater than the commercially exploited populations present in Alaska and South America (per unit area). In Palmer Deep, the researchers never saw evidence of the four species of starfish that should have been in the area. They did see an estimated 100-300 punctures and gashes in every one-meter section of seafloor mud the robot camera covered. Wherever researchers found crabs, they also found evidence of crabs changing their environment.

If the current range of king crab in Antarctica is any indicator, current trends in warming suggest that king crabs will be a common fixture on the continental shelf in 100-200 years. This has led researchers to claim that king crabs are invading the Antarctic continental shelf. Are these crabs really invading? The question is not whether crabs will really become more common on the continental shelf of Antarctica, because they most likely will, but whether the term “invasion” is the best word for what is happening in Antarctica. “Invasion” has a very specific meaning to ecologists. According to the International Union for the Conservation of Nature (IUCN), an invasive species is “an alien species which becomes established in natural or semi-natural ecosystems or habitat, is an agent of change, and threatens native biological diversity.” The uncertainty lies in the word “alien”, indicating the species comes from another place. It is difficult to tell how long crabs have been absent from the continental shelf. The fossil record is patchy at best, and scientists must rely on indirect cues, such as a fossil record of starfish that do not suffer from missing arms, which would have presumably been the case if crabs were around. Some would argue that lack of damage in fossilized starfish is not very reliable evidence. Are we just noticing more crabs on the shelf because we are spending more time looking? Have they been in Palmer Deep for much longer time than we expect?

Crabbing vessel in Kodiak, Alaska. Photo by Cassandra Glaspie.
Crabbing vessel in Kodiak, Alaska. Photo by Cassandra Glaspie.

Perhaps these crab species are undergoing a range expansion, driven by changing climate. This is expected to happen commonly around the world, as mobile animals such as fish gradually move to more suitable areas to follow changes in global climate. However, the range shift of king crabs may be more devastating for the ecosystem than a lot of other range shifts, because the Antarctic ecosystem has not experienced this kind of disturbance in many millions of years. King crabs will almost certainly be an agent of change, and a threat to biological diversity. The silver lining is that in this case, perhaps global change will create an economically important and thriving fishery for king crab on the continental shelf around Antarctica. With the remoteness of Antarctica, and the unstable weather conditions, it may be unlikely that such a fishery would ever attract investors or fisherman willing to take the risks. If it did, we better hope there will be a reality show, because this “Deadliest Catch” spinoff will be way more dangerous.

For more information:

Griffiths, H.J., R.J. Whittle, S.J. Roberts, M. Belchier, and K. Linse. 2013. Antarctic crabs: Invasion or endurance? PLOS One 8(7).

Smith, C.R., L.J. Grange, D.L. Honig, L. Naudts, B. Huber, L. Guidi, and E. Domack. 2012. A large population of king crabs in Palmer Deep on the west Antarctic Peninsula shelf and potential invasive impacts.

Sven, T., K. Anger, J.A. Calcagno, G.A. Lovrich, H. Pörtner, and W.E. Arntz. 2005. Challengin the cold: Crabs reconquer the Antarctic. Ecology 86(3):619-625. Proceedings of the Royal Society B 279:1017-1026.

Dr. Shipworm, Ph.D.

Bow section of a shipwreck visited by NOAA Okeanos Explorer on April 20, 2014. Image from NOAA Okeanos Explorer Program, Gulf of Mexico 2014 Expedition.

From April 17th 2014 through May 1st 2014, the National Oceanographic and Atmospheric Administration (NOAA) has brought together a team of scientists and engineers to explore the bottom of the Gulf of Mexico using their ship, the Okeanos Explorer, and their remotely operated underwater vehicle (ROV) named the Deep Discoverer. To the delight of science lovers across the nation, NOAA has been streaming live camera feed from their ROV for anyone to watch, greatly reducing the productivity of marine scientists and nautical archaeologists. On Thursday April 27th the Okeanos Explorer visited two shipwrecks in the Gulf of Mexico (click here to see the highlights). They discovered a variety of “encrusting biology” (animals that live on the hard structures of shipwrecks), archaeological treasures, and even the chronometer (timepiece) and the octant (a navigation device) of the early 19th century ship, which has led me to coin my new favorite phrase for use when facing impossible odds, “It’s like finding an octant in a shipwreck.”

If you watched the feed from the Monterey C shipwreck, you may have noticed one major thing missing from much of the ship’s debris field- wood. Since wood from a shipwreck is pretty much the only organic material in such a harsh environment as the deep sea, a lot of the wood from the ship had long since been eaten away by animals that feed on wood. Wood is not an easy thing to eat. It is full of fiber and difficult for the gut to break down. Even animals that have special guts for digesting plant matter, such as cows and other ruminants, cannot break down wood. In the ocean there is one fairly common critter that can eat wood. They are called shipworms.

Photo of a shipworm extracted from its burrow. Photo by USGS via Wikimedia Commons.

Shipworms are not worms at all. They are actually bivalves, a name that comes from the latin class Bivalvia. All of the members of the class Bivalvia have two (bi) shells (valves) that are hinged. Examples would be clams, oysters, scallops, and mussels. However, shipworms do not look like clams at all. They look more like worms, with long, fleshy, cylindrical bodies. They use their shells not for protection, like a clam or oyster, but to bore through wood. They can be a few centimeters long, or as long as a meter depending on the species, and they live in the burrows that they carve out of wood. The wood shavings are also consumed as food. The shipworm uses substances called cellulases to break down the wood, allowing them to extract nutrition from the tough fiber. This ability allows shipworms to join only a few known species that are capable of digesting wood, including protists, fungi, bacteria and a handful of species in several different invertebrate groups, including termites.

Shipworm burrows in a piece of wood. Photo by Wilson44691 via Wikimedia Commons.

Just as termites can cause problems for homeowners, shipworms can cause problems for people whose livelihoods depend on the sea. Shipworms are responsible for destroying ships and piers around the world. They also eat shipwrecks, which in many parts of the world are an important part of history and heritage. The shipworm’s tendency to nibble away at nautical history means they are mostly viewed as pests that need to be eradicated. There are a few marine environments in the world where shipworms are not found. One is the Antarctic, which is protected from shipworms by the circumpolar currents which act as a barrier to shipworm movement. The Baltic Sea, which is too fresh for shipworms to survive, has been protected from shipworm feeding in the past. This shipwreck oasis is now in trouble because recently shipworms have begun to invade the Baltic. An eradication program has begun to prevent the shipwrecks from becoming mollusk food.

Diagram of the tunnel shield used to build a tunnel under the Thames River. 19th century image, probably from the illustrated London News, via Wikimedia Commons.

I understand the need to protect historical wrecks. However, far from considering shipworms as a pest, I propose we celebrate the shipworm as a genius. In fact, I suggest we award the shipworm an honorary degree in engineering. Here’s why. The shipworm has played a major role in helping humans discover solutions to two major engineering problems over the last two hundred years. Have you ever wondered what it takes to make a tunnel under a river? I know I have. Turns out it is not easy. Tunnels in soft sediment, like the mud under a river, tend to collapse as they are built. In the early 1800s, Marc Isambard Brunel solved this problem with a little help from the shipworm. He observed a shipworm’s tunneling behavior. The shipworm bores through the wood and as it makes its tunnel, it encases the tunnel walls in shell material to prevent the wood from swelling, closing the tunnel and crushing the worm. Brunel designed a tunneling shield, which was an iron cylinder that was pushed further and further into the tunnel as it was excavated, preventing the walls from collapsing in on the workers. In this way he was able to make the first tunnel under the Thames River, and it was all thanks to the shipworm.

A field of Miscanthus (elephant grass) being grown for biofuel production. Photo by David Wright via Wikimedia Commons.

A more recent example of the shipworm’s prowess as an engineer is the quest for the fuel that will replace fossil fuels. The energy crisis has led us to look at biofuels, or fuels derived from living organisms, such as plants. The production of biofuels involves collecting sugars from plants and fermenting those sugars to make ethanol. However, plants store glucose in a tough fiber called cellulose. Getting the glucose out of cellulose is costly, making biofuel production from plants costly as well. A lot of recent biofuel research has aimed at reducing the costs associated with removing glucose from plant tissue. I am sure you can see where this is going. Shipworms have already solved this problem by developing an association with bacteria that live in shipworm gills and digest cellulose. In fact, some shipworms appear to live off of wood alone, and do not grow any faster when provided with extra food. These bacteria are being cultured for use in biofuel production. Perhaps in a few years the shipworm will have helped us solve another complicated engineering problem, improving human lives.

Is the shipworm an irritant or an inspiration? Shipworms have experienced an interesting evolutionary path to fill a unique niche, and they have developed the ability to eat a substance that is extremely abundant, but useless as a food source for the vast majority of other animals. This path has unfortunately led the shipworm to torment ship-owners and owners of waterfront property. It has also led to some of the most amazing achievements in engineering in the last two hundred years. This is the reason I think the shipworm deserves an honorary degree in engineering, and I hope this interesting animal will continue to inspire the great thinkers of my generation as we tackle increasingly difficult environmental issues.

For more information:

Honein, K., G. Kaneko, I. Katsuyama, M. Matsumoto, Y. Kawashima, M. Yamada, and S. Watanabe. 2012. Studies on the cellulose-degrading system in a shipworm and its potential applications. Energy Procedia 18:1271-1274.

Asfa-Wossen, L. 2012. Tunnel vision. Materials World, 20(5):10.

Tanimura, A., W. Liu, K. Yamada, T. Kishida, and H. Toyohara. 2013. Animal cellulases with a focus on aquatic invertebrates. Fisheries Science 79:1-13.

Miller, R.C., and L.C. Boynton. 1926. Digestion of wood by the shipworm. Science 63(1638):524

Gregory, D. 2010. Shipworm invading the Baltic? The Nautical Archaeology Society 431.