In honor of shark week, and because I miss Australia powerfully, I am posting two NEW videos of diving adventures in Australia. Both videos are from dives around Sydney, Australia (the dive sites were called “Magic Point” and “The Apartments”). They feature two different sharks, sand tiger sharks Carcharias taurus and Port Jackson sharks Heterodontus portusjacksoni.
In this video, the sharks appear about half way through. Check out the colony of sand tigers, which is unique to Magic Point. This was very special because sand tiger sharks are a threatened species, as are many sharks. You can also see weedy sea dragons, a very friendly and very large blue groper, and a LOT of cuddle fish!
In this video, it became VERY clear to us that it was Port Jackson shark mating season. Just watch, it was awesome.
We have walked on the moon and developed plans to put a colony on Mars. Given mankind’s interest in exploration, it may be surprising that here on our home planet Earth, 95% of the oceans remain unexplored. In a time when global change is happening unbelievably fast, it has become clear that we should try to understand the incredible diversity our oceans have to offer, before we lose it. This goal is not science for the sake of science- in order to understand the ocean resources and products that will be available for future generations, we need to first figure out what used to be in the oceans, and what is there now. Only then can we begin to make predictions about what will be there in the future.
Answering these three questions- what was in the oceans what is in the oceans, and what will be there in the future- was the main goal of the decade-long Census of Marine Life. This project started in 2000, and wrapped up in 2010 when I was just starting graduate school. While collaborations between scientists from around the world are becoming more and more common, this effort was still an uncommon example of the global science community banding together in huge numbers to accomplish a seemingly insurmountable task. Over 2,700 scientists participated, from over 80 countries around the world.
How many brand new species do you think they found in ten years? How many species do you think are in the ocean, total, and how many do you think we have found so far? After all, the study of the ocean is still fairly young. We have been studying the ocean for about 160 years. Modern ocean science, known as oceanography, has only been around since the mid 1800’s. People mostly thought that no life could exist in the deep sea until the Challenger expedition in 1874. The HMS Challenger was a research vessel employed by the British Royal Navy, and it turned what we thought we knew about the ocean on its head when it started dredging up all sorts of life from the depths of the ocean. Study of the deep sea is so new and the deep sea holds so many surprises, that it makes sense that we are finding new things all of the time. So maybe it won’t surprise you to learn that in 10 short years, the Census of Marine Life documented and described 1,200 brand new species. You may be more surprised to learn that there are MANY more species- over 5,000 in fact- that the scientists have not even had time to look at and describe to the scientific community. That is over 7,000 new species in 10 years! The scientists involved in the Census used the rates at which we were able to find brand new species to try and calculate how many more new species might be out there, and they believe that there are about 750,000 more species just waiting to be discovered. We have only described about 250,000 ocean species so far, so we clearly have only just begun exploring all the ocean has to offer.
If all of this discovery is exciting to you, you should know that you can be in the middle of it. Recently the U.S. has launched an exploratory research ship called the Okeanos Explorer. This ship has her work cut out for her, and her calendar is full of expeditions. Since 2010 the Okeanos Explorer has been to Indonesia, the Pacific Ocean between Hawaii and California, the deepest part of the Caribbean Sea (the Mid-Cayman Rise), the Galapagos islands, deep-sea habitats in the Gulf of Mexico, and deep-sea canyons along the U.S. eastern seaboard. For the latest expedition (as of May 2015) the ship has embarked on a trip halfway around the globe, from Puerto Rico to Hawaii, mapping the seafloor 24 hours a day, 7 days a week. Perhaps the coolest thing about these missions is that outreach is a HUGE component of the Okeanos mission. In fact, that huge ball on top of the ship is a satellite dome, allowing the ship to broadcast video and audio, live-streaming all of the things the ship is doing. They call this telepresence technology. This live feed is not only available to scientists, it is available to everybody. You can visit the live stream and join in on the science happening on the Okeanos Explorer, any time. This is especially awesome when the ship deploys its submarine, and takes video of the ocean depths and all of the critters found there. You can watch the discoveries happen in real time, and listen to marine scientists as they weigh in on the identity of brand new species, the unique geology of the seafloor, and sometimes archeological finds when they are exploring shipwrecks.
In addition, there is another expedition called Nautilus Live. Nautilus Live is led by Dr. Robert Ballard, best known for his discovery of the Titanic shipwreck in 1985. His ship, the EV Nautilus, is currently exploring the Gulf of Mexico. The ship’s crew is investigating the impacts of the Deepwater Horizon oil spill on the deep sea, and exploring shipwrecks along the way. They are also using telepresence technology to live broadcast video and audio, so you can join them on their expeditions. A few weeks ago the Nautilus’ submarine was paid a visit by a sperm whale, and the whole thing was live broadcast to an audience of scientists and the public. Check it out below!
We are smack in the middle of an amazing age of oceanic exploration, and the best part about it is the technology which allows everyone to be involved. So if you want to do a little deep-sea exploration on your lunch break, make sure to tune in to one of the live feeds from the Okeanos Explorer or Nautilus Live. I guarantee you will leave with a sense of wonderment and discovery.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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:
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.
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.