After Pliny’s monstrosity, many centuries went by before this question was really tackled again.  In 1815, Edward Forbes took a ride aboard the HMS Beacon, where he dredged the bottom at depths from 1-1,380 feet (0 – 420 m).  Just so you know, the average depth of the ocean is about 12,000 feet (4,000 m).  So, when I say he was barely scratching the surface, I’m not really exaggerating.  But nevertheless, he dredged the depths that he did and found that the deeper he dredged at, the less things he found.  So naturally, he thought, there must be a “zero point” at which no animals live.  He wildly extrapolated his data and determined that below 1,800 feet (600 m) there exist no animals, and he called this the “azoic zone.” So, Forbes’ answer to how many species in the deep sea was a big fat “not many.”

Luckily this “azoic zone” nonsense only lasted about 50 years.  In 1869, Charles Wyville Thomson and the rest of the crew onboard the HMS Porcupine pulled up animals from 14,610 feet (4,450 m) deep in the waters south of Ireland.  These results were later confirmed by the Challenger expedition which found animals at all depths, all over the globe.  This undeniably proved there was life at all depth of the oceans- but the question still remained.  How many species in the deep sea?

Fast forward to 1992.  Frederick Grassle and Nancy Maciolek conduct a massive (for the time) survey of the tiny animals that live in the sediments in the deep sea.  These are not the cute crawlies that live on top of the mud that had been previously sampled with dredges.  These are the small animals that live their lives between the grains of dirt at the bottom of the ocean.  Of the 798 species that they found, over half were new to science!  Pliny’s head would explode if he heard that more than double the total animals he thought existed in the whole ocean were found just in the mud.

Grassle and Maciolek did some impressive math and ended up calculating that they were finding one new species per square kilometer they sampled.  Let’s break that down.  One square kilometer is equal to a little more than one-third of a square mile.  So, they are basically finding three new species in each one-mile-square block of mud they are sampling.  This means if they were to sample an area the size of New York City, they would find around 782 new species, and if they were to sample an area the size of London, they would find about 1,572 new species.  These new species add up fast – you see, there are 300,000,000 square kilometers (115,830,647 square miles – almost 30 Europes or 431 Texases) of mud deeper than 1000 m in the ocean. The end result of all this is a conclusion of 300,000,000 species living in the mud at the bottom of the deep ocean.  This is not counting swimming things!  That’s a heck of a larger estimate than the 176 species estimate of centuries ago.

.It turns out that this calculation of Grassle and Maciolek was probably a bit of an overestimation.  They realized that much of the ocean is oligotrophic, or not very nutrient-rich and therefore not very productive.  This would mean that in many areas of the ocean, the rate of new species added per square kilometer is probably much less than what they found in their sampling area.   So, they ended up conservatively estimating the true number at more like 10,000,000 species in the mud. This is still a huge amount of diversity in the deep sea.

Grassle and Maciolek’s 10 million species hypothesis sparked quite the controversy, with biologists from many sub-disciplines quickly arguing for or against the high number.  Isopod biologists Poore and Wilson said they had seen even more diversity just among isopods in their samples than the average number of species per 100 samples that Grassle and Maciolek had used in their calculations.  This, they argued, must mean there are even more than 10 million species!  In 1971, though, Thorson argued that there were only 160,000 species in the oceans across all depths- so far less than 10 million could be in the deep sea.  In 1992, May argued that only 500,000 species would be possible in the deep sea.  Lambshead in 1993 reminded everyone that there are a boatload of nematode worms and other animals (collectively called meiofauna) that live in the mud that were too small to be sampled by the gear Grassle and Maciolek used.  This, Lambshead argued, could mean a total of 100,000,000 marine species.  Consensus just could not be reached.

Here’s the problem, though.  It is a hard question to answer.  Each person who has attempted to answer this question was doing the best with the data that they had at the time (except Pliny- that guy was just an idiot okay). However, species diversity and especially how many species you discover in each new deep-sea “block” can vary considerably at different depths, regions, and oceans. Grassle and Maciolek’s encoutering 3 new species per block was based on data from the North Atlantic. Does 3 new species “rule” also apply to other parts of the Atlantic or to the Pacific? So without massive amounts of data, it is likely we will be kept guessing for a few more years to come. So, I can’t tell you exactly how many species are in the deep sea, but I can tell you that we currently have 409,543 named species in the ocean (World Register of Marine Species, accessed 03/18/2019).  The best part is that we are getting better and better at discovering new species, and hopefully in years to come we will be much better equipped to answer this question realistically.

Cover photo credit to Monterey Bay Aquarium Research Institute (MBARI).

The post How many species are in the deep sea? first appeared on Deep Sea News.

Prior to 1967, the environmental extremes of the deep were thought to limit life. The deep sea is dark (can’t-see-your-hand-in-front-of-your-face dark), cold (only-four-degrees-above-freezing cold), and under an extreme amount of pressure (one-elephant-on-each-square-inch-of-your-body pressure).  This suite of factors should make survival challenging, and thus for a century, scientists assumed the deep sea was biologically a desolate wasteland.  Even after the discoveries of animals living at extreme depths in the late 1800s, Victorian scientists expected that there could not be a diverse array of animals surviving in the deep sea.  Enter Robert Hessler and Howard Sanders who in 1967 used newly developed sampling devices to discover that the deep sea is shockingly diverse, and perhaps just as diverse as tropical shallow-water habitats. 

Scientists were completely baffled as to how high diversity could occur in such a bleak place.  They began to throw out theories, but they were limited by the little data that had been gathered from a poorly explored deep ocean.  The scientific publications of this time on deep-sea diversity read like there were a few people in a room with a whiteboard, writing everything they remember from their ecological textbooks, talking through each theory, slowly crossing off possibilities, and working their way down the list.  

Howard Sanders began by writing “Specialization” on the whiteboard with his paper introducing the Stability-Time Hypothesis in 1968.  He suggested that because the deep sea is monotonous and predictable (i.e., it is stable), populations have the evolutionary time to become newly specialized in how they feed. Over time, these populations become so specialized they evolve into totally new species, eventually driving diversity up.  Further research and explorations indicated that the premise of this argument was wrong- the deep sea is actually not that stable.

Then, Paul Dayton and Robert Hessler walked up to the board and scratched off the “Specialization” idea with their paper in 1972 entitled “The role of biological disturbance in maintaining diversity in the deep sea.”  The pair do not argue against the idea that the deep sea is predictable and stable.  In fact, they favor the idea… except for the part where they proved that deep-sea species are actually not more specialized than shallow water species.

“Specialization” got a strikethrough on the whiteboard, and Dayton and Hessler wrote “Predation” below it.   The duo introduced a specific type of predation pressure they labelled “biological cropping.”  No, biological cropping is not deep-sea animals learning agricultural techniques… but a combination of predation and deposit feeding.  Animals can eat other animals either intentionally (e.g. hunting down prey) or unintentionally (e.g. stuffing everything you come across into your mouth and it just so happens that you get a live one).  This “cropping,” whether accidental or not, reduces competition by preventing one or a few abundant species from monopolizing the resource.  These species get knocked out, allowing far more species to get a piece of the proverbial pie. Nobody gets sent into extinction by competition.  Dayton and Hessler’s idea is not necessarily that diversity is driven to be high in the deep sea, just that it is not limited.

Dayton and Hessler’s “Predation” idea never got fully scratched off the list, but the difficulty of testing the idea and conflicting results have led many to write large question marks next to it.   Many other ideas now are situated below “Predation,” including: “Disturbance,” “Patchiness,” and “Successional Dynamics.”

Ultimately, those of us in the deep-sea scientific community are still today standing around the dry erase board bouncing many of these same ideas off each other.  Sometimes we manage to cross one off the list, or add one, or at least add to our understanding of the ideas.  One thing is clear though, we still haven’t gotten it all figured out.  So… anyone have a dry erase marker?

The post How is the deep sea so diverse? The struggle is real for late 1900s ecologists first appeared on Deep Sea News.

Nearly two miles below the ocean’s surface, we are building new worlds. You might be surprised that these ecospheres are wooden—little log cabins hosting a cornucopia of sea life.  By controlling the size of these wooden homes, we can begin to answer fundamental questions about how the oceans will adapt to climate change. In our most recent, paper we are beginning to grasp the extent that food controls biodiversity, biological novelty, and the competition among species.

On the seafloor, chunks of wood—we call them wood falls—play host to a variety of invertebrate species often not found anywhere else in the ocean.  These species live their entire lives on waterlogged timber; settling out of the water column as larvae to consume wood, or to prey upon other species that do.  Once on a wood fall, these organisms can never leave, their dispersal limited to the beginning of their lives as plankton. And for all of these reasons, the island communities created by wood falls serve as the perfect experiment.

Because of humans, the oceans are radically changing.  They’re becoming warmer, more acidic, and less oxygenated.  But an even more disturbing trend has been uncovered; the oceans may be becoming less productive, providing less food and carbon for its denizens.  Scientists do not really have a handle on how life in the oceans will react to this finding. What will happen to individual species and whole communities of species?  This is an intractable question in many ways because it is hard to test. We cannot easily experimentally adjust how much food a swath of ocean gets. Or can we? In a wood-fall experiment we can change the amount of food the community receives by simply adjusting the size of the log. These species cannot leave to look for better meals once they arrive.  They are wholly dependent on the log we’ve provided in an otherwise barren patch of the deep ocean floor.

In 2006, Jim Barry (MBARI) and I placed 16 logs with a remote operated vehicle (ROV) over 2 miles down on the deep-sea floor off the California coast. We left them there for five years and then remotely and robotically harvested them.  After sorting, identifying, and analyzing, these wood falls are revealing yet another fundamental insight.

How does more food, or more specifically more carbon, allow for more species?  To explain the science, let’s visit a donut shop. At this donut shop, there are three types of donuts: chocolate, plain glazed, and raspberry filled. I ask the donut maker to make three new donuts and provide extra ingredients for them to do so.  

In Scenario A, the donut maker produces chocolate, plain glazed, and raspberry filled along with a dark chocolate, a plain glazed with sprinkles, and a blueberry filled.  The donut shop is still just serving three basic types of donuts: chocolate, plain glazed, and fruit filled. These new donuts are just slight deviations. We will call this Scenario A donut packing.  The donut maker is just packing the menu with variants of the original donuts.

Much like donuts in a shop, we can think of species in a community the same way.  As food increases and the number of species increase, are we getting slight deviations (donut packing) or something truly novel (donut expansion)?  In the ecological sense, are niches, i.e. the full set of characteristics that describe a species and their requirements, being packed into the community or are we expanding the overall niche diversity.

And so for our wood-fall species, we put numbers to each of their niches describing their feeding habits, how well and even if they move, as well as their preference for space on the wood fall. We found that as you increase the wood-fall size, and the amount of wood, you do not get truly novel species, rather you pack these species into the community.  They are just slight deviations. This suggest that increased food reduces competition among animals allowing them to coexist peacefully. Species do not have to be completely novel to join the community.

In the end this means that decreases of productivity in the oceans, will limit diversity by not allowing species to coexist.  Species will be vying for the same spots and in the end many may lose.

McClain, C.R., C.L. Nunnally, A. Chapman, and J. Barry. (2018) Energetic Increases Lead to Niche Packing in Deep-Sea Wood Falls. Biology Letters 

The post Wooden Homes on the Seafloor Yield Insights Into the Impacts of Climate Change first appeared on Deep Sea News.

The recent string of violent tragedies, both in the USA and abroad, have wrenched our hearts and left our minds baffled. Minnesota, Dallas, Baton Rouge, Orlando. This list continues. Some may view these tragedies as separated from science. We disagree, science does not happen in a vacuum. Science happens in the daily interactions of curious minds, no matter their race, class, ethnicity, gender identity or orientation. Tragedies affect people’s lives and communities in different ways–some impacts we can fathom, others we cannot.

For anyone who has been impacted by these tragedies, we want you to know we are standing with you. We are here to listen when you need to speak. When words measure short, we will sit with you in silent support. We know that your experiences are what matter, not our interpretations. We recognize that discrimination is not dead and we have a long way to go. We strive to be your allies.

As human beings as well as scientists, we commit to the following: We will continually educate ourselves. We will ask questions. We will challenge our own biases.  We will be inclusive. We will help build a stronger community. We will speak up, even when it is uncomfortable. We are willing to be called out when we make mistakes. We will correct our mistakes. We will consciously respond with awareness. Our DSN core values will provide grounding as we stumble forward through these times.

We encourage other scientists, marine or otherwise, to do the same. Strive to be better allies and make science a place where all people are welcome.

Sincerely, the DSN team:

Kim Martini
Craig McClain
Holly Bik
Rebecca Helm
Douglas Long
Alex Warneke

Below are some resources so you can be a better ally. Know more? List them in the comments.

EDUCATE YOURSELF

Too Traumatized to Science by Dr. Danielle N. Lee

5 Tips for being an Ally by Franchesca Ramsey

A field guide to privilege: some reasons why we lack diversity by Dr. Miriam Goldstein

How Minority Students’ Experiences Differ: What Research Reveals (paywall)

Mentoring Minority Students by Sarah Tuttle

Advice for white folks in the wake of the police murder of a black person

Curriculum for White Americans to educate themselves on race and racism

LEAGUE OF ALLIES

Facing Reality, Speaking Out and Building Trust after St. Paul, Baton Rouge and Dallas by the Union of Concerned Scientists

Sierra Club Statement on the killing of Police in Dallas, Texas 

Members of the AAS Committee on the Status of Minorities in Astronomy (CSMA)

Why building diversity in the Earth and Space Sciences Matters – From the Prow American Geophysical Union (AGU)

The post An open letter from DSN to our fellow scientists first appeared on Deep Sea News.

Maybe if Red Bull funded marine research, we could send a skydiving human icebreaker, whose parachute doubles as an otter trawl and niskin bottle, to crash through polar seas in the winter and collect scientific samples. (Felix Baumgartner, CALL ME!)

No, marine research is funded by government agencies – they hold the dolla$ for the ships. Winter sampling-by-stuntman would be a little too risky for their tastes, and so research in polar regions by default has to happen in the summer (one of the reasons the Antarctic program was almost screwed by the government shutdown). My point? Our knowledge of polar regions is almost exclusively based on research done during ONE season. But according to a recent study, that seasonal bias is really messing with our understanding of biology.

In a badass new paper, Ladau et al. (2013) looked at diversity in bacterial communities around the globe, comparing patterns across seasons, and at the equator versus the poles. Although we generally think of the tropics as “biodiversity hotspots” for larger organisms, bacteria swimming in surface ocean waters are way to hipster to follow such mainstream diversity patterns.

Because scientists always sample high latitudes during summer months, previous data seemed to give the appearance of higher bacterial species diversity in tropical waters. But this isn’t actually true! The bacteria all go party at high latitudes in the WINTER – you know, that time of year when there are NO SCIENTISTS doing any sampling. Bacterial diversity shows huge, seasonal winter peaks (in December at temperate and high latitudes in the Northern Hemisphere, and in June at temperate latitudes in the Southern Hemisphere), making tropical biodiversity look  pretty LAME in comparison.

Ladau et al. used a modeling approach to compensate for the persistent sampling bias in time and location – they were able to extrapolate the predicted species distributions of bacteria based on real environmental datasets (rRNA genes sequences). They pummeled the data from every possible angle – changing models, changing parameters, subsampling their data, using other datasets, and even looking at error rates. Nothing could mess with their results – the predicted biodiversity patterns stood up to every kind of test.

Why does bacterial diversity show seasonal peaks during the wintertime in both hemispheres? We’re still not sure, but it might be due to vertical mixing which brings nutrients (and species?) to the surface. Another theory is that bacteria could migrate across latitudes. Models are no substitute old fashioned fieldwork, but they’re important for letting us look at biology from a different perspective. In this case, it shows we need to collect way more wintertime samples.

Reference:

Ladau J, Sharpton TJ, Finucane MM, Jospin G, Kembel SW, Dwyer JOA, et al. (2013) Global marine bacterial diversity peaks at high latitudes in winter. The ISME Journal, 7:1669–77.

The post Hipster bacteria hate the tropics (it’s too mainstream) first appeared on Deep Sea News.

After I successfully defended my Ph.D., and as I and packed up my belongings to move across the country for a new job (more on that in a later post), I’ve been reflecting on privilege in marine science. The word “privilege” often makes people turn away, afraid of being made to feel guilty and scolded. Certainly these discussions are way less fun than talking about the latest wonderful ocean discovery. But by driving people away from science, we are missing out on so much talent and so many wonderful discoveries, and so I want to use this post to detail some of the invisible barriers that are keeping talented people out of our field.

To quote from the excellent Finally, A Feminism 101 blog:

Privilege, at its core, is the advantages that people benefit from based solely on their social status. It is a status that is conferred by society to certain groups, not seized by individuals, which is why it can be difficult sometimes to see one’s own privilege.

Scientists don’t always recognize the additional barrers, besides hard work, that prevent people from succeeding at science. My perspective on this is as a person from a non-professional middle class family (father a small business owner, mother a physical therapist) who went to mediocre public schools and then to an Ivy League college. My family was well off by the standards of our town – homeowners, two cars, regular vacations within the USA- but nowhere near the financial level that was the norm for a prestigious private college. Entering college was quite a shock, both academically and socially. I have never forgotten that terrible feeling of inadequacy, and I was already coming from a white college-educated family in the middle class. It’s much, much more difficult for people, particularly those of color, coming out of working-class and poor households.

Here, I present a short field guide to type of privilege that I’ve observed in science, and explain why becoming a scientist becomes immensely more difficult for people without that form of privilege. This is aimed at professors, since academia is my experience, but please add your own perspective in the comments.

Before college [added 24 Jan 2013 18:3o PT]

David Shiffman made the excellent point in the comments:

I’d also consider adding pre-undergraduate experiences (summer science camps, internships, etc) which help getting into an undergraduate college with a good science program in the first place. They’re also a good way to get people excited about science at an early age. However, these are expensive (though many have scholarships, there’s still an opportunity cost associated with not working).

David’s absolutely correct – summer experience before college set many scientists on the path. I participated in two no-cost summer programs as a high school student: the University of New Hampshire Math & Marine Science program (which no longer exists), and in the Earthwatch Student Fellowship program. The Math & Marine Science program took me to Shoals Marine Lab, which blew my mind with awesomeness, kept me taking science classes, and indirectly got me involved with my undergraduate lab (a long story involving student theater & Jarrett Byrnes).

Another obstacle that comes up in high school is Advanced Placement (AP) or International Baccalaureate (IB) classes. Entering college with credit are a great help with completing the many class requirements of a science major. However, many schools do not offer these programs – my high school didn’t.

Alison notes the lack of stability in science:

In my experience, high school students from lower income backgrounds, even those who are interested in math and science, are wary of starting down a career path where they are not likely to be financially stable for 10 years. They often feel guilty about attending a four year school or leaving home to go to college because they won’t be helping their families during that time. Just the idea that this financial uncertainty might extend for many more years excludes a grad school path for many of them.

Undergraduate research experiences

The main pathway to becoming a scientist is through research experiences as an undergraduate. However, many of these cost substantial amounts of money, or at least don’t pay enough to fulfill financial aid work/study requirements. Barriers for undergraduates include:

• Research that costs money to participate in, even if that money is just for equipment or room/board. This is extremely common in the field sciences, like ecology & geology.
• Volunteer research that prevents a student from making money. Remember that most financial aid packages REQUIRE a student to make a certain amount of money over the summer. If they aren’t getting paid to do research, then they are either adding to their debt or working two jobs, neither of which is setting them up for scientific success.
• Transportation. I had a Research Experience for Undergraduate internship (REU) that required me to have a car, which I was fortunately able to borrow from my grandfather for the summer. This REU launched my independent research career, but I would not have been able to participate at all had my grandfather not coincidentally become unable to drive at that time.
• Family expectations. Many undergraduates are expected to help out their families, by caring for younger relatives, doing household chores, and making money for shared costs. It is therefore more difficult for them to have as flexible a schedule as undergraduates who do not have these responsibilities. They may not be able to stay late or come in on weekends.
• In the comments, Stacy notes:
  

  I would like to point out another thing that I think is a really big barrier — not KNOWING that you SHOULD BE seeking out opportunities to do research as an undergrad.

  Similarly, SMA says:

  As a first-generation, minority, female student I would have never ever done something like apply for an REU, let alone graduate school (who goes to grad school?! No one I knew)…I very well may have never gone to graduate school if it wasn’t for programs that were aimed for people like me.

It’s really important to remember that undergraduates – particularly the driven and responsible undergraduates most likely to succeed in science –  often don’t want to explain the details of their financial and logistical difficulties to their professors. They may mysteriously turn down opportunities that seem perfect, or not show up to lab activities. For my REU that required a car, I certainly did not wish to explain to my intimidating PI that I had no way of getting to the marine lab – I wanted desperately to appear worthy and responsible. This is why it’s important for professors to think about the invisible barriers that might be preventing certain talented students from success.

Graduate school

Graduate school can be much easier to navigate than undergraduate, simply because expenses are paid from fellowships and grants. (Though see Jessica’s comment.) The major invisible difficulty that I’ve observed has been the reimbursement process. It’s common practice for people to spend their own money on scientific supplies and then apply for reimbursement from their grant, actually receiving the money 3-8 weeks later. For people without substantial cash flow, this can lead to credit card debt and future problems.

[EDIT 11:05 AM ET]: Oh man, I can’t believe I forgot LGBTQ-ness! Science is social and people are going to meet your partner. It’s a privilege to be certain that your advisor/committee/classmates won’t be (at best) nervous and awkward around your partner.

Britt adds in the comments:

Coming at this from a field biology perspective, I think there is a big privilege issue related to socialization and cultural fit. We literally live with our bosses. PIs tend to pick RAs and students they feel comfortable around, because otherwise the field season will be terrible. But that privileges students who are already equipped with middle class intellecutal tools and experience, to get each others jokes and get along.

Post-graduate school

Oh, the real world come crashing down again! But frankly, some aspects of the post-doc life are worse for post-doc than they are for non-science fulltime employment.

• Work-family balance. This has been amply written about elsewhere, but many late-20s & 30s people are partnered and have children. This means they can’t just pick up and move anywhere there is a job. Having a partner who WILL move with you is a privilege! Especially a partner who takes care of domestic work so that you can just do your science.
• Debt. Many post-doc jobs pay rather poorly, and students with substantial debt (e.g., from not working in the summer during their undergrad so that they could do science!) may be unable to stay in science.
• Health insurance (USA only). This is the one that really blindsided me, and is causing me substantial problems right now. Some fellowships do not give you access to group health insurance, but require you to purchase health insurance on the individual market.  This makes health insurance impossible or unaffordable for fellows with a health history – for example, people who have common conditions such as diabetes, multiple sclerosis, mental health problems, or in remission for cancer. People with disabilities are likely also to be excluded, and women of childbearing age have to purchase a separate maternity policy, penalizing them. In my case, I had a pancreatic tumor when I was 17, which led to major hospitalization and surgeries, and has made me difficult to insure ever since. (I have a couple awesome pirate-ly scars, at least!) My husband and I have spent weeks trying to figure this out, but may be forced to spend over $13,000 just on health insurance this year. Since health insurance and travel funds come out of the same pool, my health insurance difficulties may prevent me from traveling for work, leading to lack of future opportunity. Stay tuned!

This is by no means a comprehensive list, and I’m very interested in hearing from people from different backgrounds and at different career stages. Please comment, and I’ll add relevant comments to this post.

General comments

Erin notes the importance of culture. Erin says:

In my opinion, even if people have the financial means to pursue environmental/marine science as a field of study and career, they may not believe this type of work has the same sense of stability and prestige as the fields of medicine, business, technology, etc. Studying the ocean or the environment just simply doesn’t seem practical to most people from immigrant communities – more of a hobby than a profession.

Other perspectives [updated 24 Jan 18:30 PT]

A Dream Deferred: How access to STEM is denied to many students before they get in the door good. By Danielle Lee.

Who I am, since #IAmScience. By Jennifer Biddle

The post A field guide to privilege in marine science: some reasons why we lack diversity first appeared on Deep Sea News.

Tongue biters have been in my inbox a few times lately.  If you’ve managed never to come across these interesting little isopods before, they are members of a wholly parasitic group called the Cymothoidae.  For regular readers of Deep Sea News, you can think about them as smaller versions of Bathynomus, which they resemble a lot, the main difference being, you know, that whole sucking-the-life-out-of-a-fish-through-its-tongue thing.  There’s quite a few species and they are widely distributed around the world in fishes from salt water and fresh water alike.  What really interests me about these perennial visitors to my newsfeed is that people seem to be singularly horrified by them, whereas I don’t find them the least bit repulsive or even surprising in any way.  To me, they are just another critter that has found a niche to occupy; I guess that’s the parasitologist in me (long before I studied whale sharks, I studied the ecology of parasitism).

In any sort of systematic parasitology training, you quickly realize – or are explicitly taught – that the presence of critters like the tongue biter is not unusual.  Indeed, most wild fish harbour several species of parasites simultaneously and this is totally and completely normal.  This seems to be a really hard concept for a lot of people to wrap their heads around.  Parasites are assumed to be unusual and bad, a sign that things are seriously amiss.  It’s tempting to look at the host of that tongue biter and think “there goes an evolutionary loser – an animal that fell prey to a repulsive little parasite”.  But that’s not how it works at all.  In fact, if you can survive and thrive despite your parasite burden, then you are an evolutionary winner, an idea that was formally codified as the Hamilton-Zuk hypothesis, based on studies of parasitism and plumage in birds.  The corollary of this is that parasitism is a constant and normal part of the evolutionary pressures acting on an animal, and for that to be the case, parasitism has to be not only normal but positively common.  And so it is.  We just don’t notice it, because for the most part parasites are cryptic, they are literally out of sight and out of mind.  It’s only when something as glaringly obvious as a tongue biter comes along that we even notice parasites at all, even though that same fish may well host a half a dozen other species  at the same time.

No fish is an island.  When I snorkel on a Pacific reef, I don’t swim along and see mother-in-law Diagramma labiosum, I see one of the superstars of parasitology.  When I used to study these drabbest of reef fishes in the lab of my PhD advisor Tom Cribb, we had counted sixteen different trematode worm species in the digestive tract alone.  There were also monogenean worms on the outside: a different species for each fin, several on the gills and even one that specialized on the pharyngeal tooth pads (a tough place to live indeed). There were also parasitic copepods of several varieties and a dozen protozoans of varied flavours throughout the tissues.  Oh yeah, there was also an enormous amphilinid – a bizarre worm distantly related to tapeworms – that lived in the body cavity.  All in all, every individual Diagramma was a swimming hotspot of parasite biodiversity, and seeing a school of them together was like looking at a rainforest; you just needed a dissecting scope and some iris scissors so you could see the trees in the forest.

In my PhD studies (which seem to be receding in the rearview mirror altogether too fast these days!), I looked at far more modest critters.  While a Diagramma might weigh a good 5-10lbs, the fishes I did for my dissertation were little goby-like and minnow-like fresh water jobbies that occur in Australia’s species poor temperate rivers.  Even there, the average parasite richness in a 5 cm/2 inch fish was close to five species per individual.  Fish size does make a difference, but the truth is that if there is a fish swimming, then one, and more likely many more, parasite species has made its home there.  I have never heard of a fish that does not host any parasites at all and I doubt that such a fish exists.

The implications of this for global diversity are profound.  If there are 28,000 species of bony fishes, and each has at least 5 unique parasite species, then those 28,000 fishes scale up to 140,000 species of parasites.  If you use more aggressive (I would argue realistic) estimates of parasite richness, then it’s easy to get estimates of a quarter of a million species of fish parasites or more.

This is surprising to many people, not least to my fish and fisheries biologist friends.  “Where are they all?”, they say.  When they dissect fish for diet studies or anatomy, they don’t see all the things a parasitologist sees.  The truth is that the majority of parasites are missed unless the person doing the dissection has been trained to look in the right way.  Freezing fish, for example, which is bog-standard practice for diet studies, is basically a total bust for parasites.  To really see everything, you need to dissect fish fresh, immediately after death, and preferably immersed in saline (for internal organs) or the relevant water (for external surfaces), under a dissecting scope.  Only then can you appreciate the delicate form and characteristic movements than can reveal a tiny trematode among strands of mucus and strips of intestinal epithelium.  You also have to look in the right places.  Not just the obvious places like the intestine and gills, but inside the heart chambers, in the gall bladder, in the nares and inside the eyeballs, just for instance.

My aim here is to help break the notion that parasitism is in any way unusual in the sea, or anywhere else  for that matter (those cute fluffy kangaroos? Yuppers – DOZENS of roundworm species each).  To that end, here’s a graphic that I hope helps to show that your average fish is, to parasites, a diverse palette of microhabitats, all of which are ripe for the exploiting for the cost of a few specialized adaptations.  If you look hard enough, you’ll find something living in most of these microhabitats, in most species of fishes.  You can find figures like this in many animal parasitology textbooks, but I made this one special for you lot.  So, enjoy, and use as you see fit (click twice to embiggenate)

The post No fish is an island first appeared on Deep Sea News.

But the food not so delightful,


But since we’ve got no place to go,


Let It Marine Snow! Let It Marine Snow! Let It Marine Snow!

In the late 1960’s, two marine biologists, Howard Sanders and Robert Hessler, made a shocking find–the biodiversity of the deep-sea floor is astoundingly high. In an area the size of a coffee table over 300 species can coexist, a number that rivals tropical rainforests and coral reefs. Yet these findings also raised a paradox. High diversity is typically associated with physically complex habitats, like forests and reefs, plentiful with food that allow for a variety of niches. In the food poor, homogenous mud flats of the deep sea, how can so many species coexist? The answer is snow.

The lack of light in the deep oceans precludes photosynthesis. Thus, primary production of carbon, the base of a food web, is virtually absent. Deep-sea organisms are reliant upon a trickle of falling material from the productive shallow oceans overhead. This material is largely a low quality and low quantity mixture of decaying bodies and feces degraded further by bacteria on its decent into the deep. Roughly 2-5% of the total carbon on the ocean’s surface falls to the deep seafloor, the equivalent of roughly 2-3 tablespoons from a 5-pound bag of sugar. This sinking material, marine snow, falls as a dusting on the ocean bottom. But like a light snow in your yard does not form an even layer and Buffalo receives more snow than Miami, marine snow too is denser in some spots whether an area the size of coffee table or an entire ocean.

In this marine snow medley lays the answer for our deep-sea paradox.

In the 1970’s, Howard Sanders, Fred Grassle, and Paul Snelgrove proposed instead of the deep-sea floor being a homogenous wasteland, it was comprised of a variety of patches each with a unique set of organisms, i.e. the patch-mosaic hypothesis. The deep-sea floor is essentially a patchwork quilt of different small habitats. I began this year by publishing a study addressing how heterogeneity in marine snow of distances of just a few yards can lead to completely different communities of organisms. At the end of this year, just today in fact, I with coauthors show this same pattern over several thousands of kilometers.

In 2006, Jim Barry and I during my tenure at the Monterey Bay Aquarium Research Institute sampled a 3203-meter deep site off the Monterey Bay. We collected with the robotic arm of a remotely operated vehicle 44 sediment cores over approximately 400 yards. Each core we sieved and removed the small invertebrates living in the sediment, from worms to crustaceans to molluscs plus much more. Equally important, we measured the carbon content, of the sediment as an indicator of marine snowfall. Largely, we found that invertebrate communities in cores taken adjacent to each other were just as likely to be similar as dissimilar to one another. Indeed, cores adjacent to one another were just 3% more likely to share common species than cores taken 350 meters apart! Why would communities right next to one another be so different? Differences in marine snow accumulation. Invertebrate communities receiving comparable marine snowfall were more similar.

Today in the Proceedings of the Royal Society with collaborators Allen Hurlbert and James Stegen from the University of North Carolina, I unravel the paradox of the deep a little further. Given the difficulty of conducting deep-sea work, patterns of diversity of entire oceans are rare. In 2008, John Allen, working previously with Howard Sanders, published an amazing dataset of deep-sea bivalves taken form 270 sites across the Atlantic Ocean. We combined this dataset with data on bivalve sizes and genetic relatedness with multiple datasets on the environment, including annual marine snow accumulation. We found that the availability of both chemical, i.e. marine snow, and thermal, i.e. temperature, energy explained differences in compositions of bivalves communities across the Atlantic Ocean. Interestingly, and in contrast to current thinking (including my own!) that invertebrates with planktotrophic larvae should be able to disperse everywhere, we also detected the importance of dispersal ability in explaining community differences. In other words, some of what determines where a bivalve is located in the Atlantic is determined by its dispersal ability and the amount of energy it requires.

But we went one step further and developed a simulation. We constructed virtual bivalves allowing them to evolve traits, fill environmental niches, and disperse across a virtual Atlantic Ocean. This is a computationally complex and demanding operation and required a cluster of computers at UNC to run. In each simulation, we could control the dispersal ability and food requirements for the bivalves. For each simulation, we would then compare the patterns that emerged with those in our real Atlantic bivalves communities. This would allow us to determine the exact level of dispersal ability and food requirements of bivalves to produce changes in community compositions across the Atlantic. From our simulations, we found that 95% of bivalves could disperse 749 km from their natal site. We also found that 5% of bivalve juveniles would not be able to persist in habitats that deviated from their optimum habitat more than 2.1 grams of carbon per meter squared per year. That translates to about 1 teaspoon over a dining room table over the course of an entire year! Bivalves are extremely sensitive to the amount food available.

Overall, these studies illustrate that the deep-sea floor is like your Grandma’s quilt presenting a variety of patches of material. These patches, driven by differences in marine snow, whether occurring over inches or miles, provide unique habitats that allow a variety of different animals to coexist. And much like humans prefer different amounts of snow (give me warm weather or give me death!), deep-sea species are uniquely adapted to differences in marine snow.

Craig R. McClain, James C. Stegen, and Allen H. Hurlbert Dispersal, environmental niches and oceanic-scale turnover in deep-sea bivalves Proceedings of the Royal Society B: Biological Sciences published online before print December 21, 2011, doi:10.1098/rspb.2011.2166

UPDATE 1:
Also take a look at the great write ups by Wired and IO9. Love the titles! The Bounty of Species in a Single Scoop of Seafloor Mud and The Ocean Floor is Like a Rainforest Where Feces and Dead Animals Rain From the Sky

UPDATE 2: I was asked for a legend to the animals above.  Hopefully this helps. As for the species, I could give you the actual species names but perhaps that would not be helpful to readers.  Instead I will give you the general groupings that may be more informative.

So in this orientation above from left to right

Row 1 bivalve, polychaete, ophiuroid, polychaete, bivalve, cumacean, amphipod

Row 2 cumacean, anemone, aplacophoran, bivalve, cumacean, bivalve, aplacophoran

Row 3 polychaete, bivalve, cumacean, bivalve, big polychaete, amphipod, 2 oligochaetes

Row 4 scaphopod, bivalve, aplacophoran, long polychaete, cumacean, amphipod, bivalve

Row 5 bivalve, polychaete, aplacophoran, amphipod, bivalve, amphipod, polychaete

Row 6 ostracod, polychaete with tube, bivalve, anemone, polychaete, amphipod, polychaete, bivalve

Row 7 polychaete, gastropod, amphipod, caprellid shrimp, scaphopod, bivalve, polychaete, cumacean

Echinoderms

ophiuroid http://en.wikipedia.org/wiki/Brittle_star

 Molluscs

bivalve http://en.wikipedia.org/wiki/Bivalve

aplacophora http://en.wikipedia.org/wiki/Aplacophora

scaphopod http://en.wikipedia.org/wiki/Scaphopod

gastropod http://en.wikipedia.org/wiki/Gastropod

 Annelids

polychaete http://en.wikipedia.org/wiki/Polychaete

oligochaete http://en.wikipedia.org/wiki/Oligochaete

Crustaceans

cumacean http://en.wikipedia.org/wiki/Cumacean

amphipod http://en.wikipedia.org/wiki/Amphipod

ostracod http://en.wikipedia.org/wiki/Ostracod

caprellid http://en.wikipedia.org/wiki/Skeleton_shrimp

Cnidarian

anemone http://en.wikipedia.org/wiki/Sea_anemone

The post Let It Snow, Let It Snow, Let It Snow first appeared on Deep Sea News.

This lovely piece of art, by graduate students Laurel Hiebert and Kira Treibergs with artwork by Marley Jarvis, made the rounds last week. We are thrilled to have been given permission to post it on Deep Sea News! This design is now available as t-shirts and totebags, with proceeds to benefit the Oregon Institute of Marine Biology and the new Charleston Marine Life Center. Spineless Supporters can also join their Facebook group.

Our own para_sight had a similar take on the 99%.

The post Octopi Wall Street! first appeared on Deep Sea News.

The post We are the 99% first appeared on Deep Sea News.