Well it could be any species. Anglerfish, carnivorous sponge, giraffe, or even a montane unicorn.

BUT I WANT TO WRITE ABOUT THE NARWHAL! NOBODY CAN STOP ME!

MWAHAHAHA

Let’s assume that once a species gets closer and closer to this geographic limit it is getting closer and closer to some aspect of the environment that is intolerable for them. For our Narwhal, too far South the temperature is uncomfortably warm. This happens with each of its boundaries on the north, south, east, and west sides. But the center of that geographic range is prime position. Everything is just right. The perfect balance. A Goldilocks scenario. At this place the Narwhal flourishes and the number of that Narwhals is spectacular. This is the Abundant Center Hypothesis. A species is most abundant at the middle of its range. And in the case of our Narwhal, we should find the most of that horned, blubbery beauty right smacked dab in the center of its geographic range.

Graphically, you can think of the Abundant Center Hypothesis as normally distributed bell curve (see above). Pick one of those geographic or environmental axes like temperature or latitude and at the center is peak density or abundance for that organism.

But how well does this actually work in the wild among all animals and plants?

New work by Tad Dallas, Robin Decker, and Alan Hastings at the University of California, Davis sheds some new light on this almost 40-year old question. They recast the Abundant Center Hypothesis into a new testable relationship, if a species is most abundant at their range center, then a negative correlation should exist between abundance and distance from the center—a distance-abundance relationship (above illustration). Overall, the group of scientists examined this relationship for 1,109 birds, 63 fish, 81 mammals, and 166 trees in the Americans.

Overall, distance-abundance relationships like in the figure above were rarely observed. For birds, only 123 out of 1,109 species displayed a negative distance-abundance relationship as predicted. Moreover, 151 birds displayed the exact opposite pattern, their abundances actually increased away from their center. For fish, mammals, and trees combined only 13 negative relationships were found.

So what of the Abundant-Center Hypothesis? Alas, it may be time for the trash bin.
Recovering the predicted relationship for only 9.5% of the organisms tested isn’t exactly impressive. One glimmer of hope remains. The study by Dallas, Decker, and Hasting was for land dwellers. For my beloved Narwhal and other denizens of the sea, they may still be most bountiful at the centermost.

The post Where Do the Most Narwhals Live? first appeared on Deep Sea News.

This year marked the 100th Anniversary of the Western Society of Naturalist (WSN) meeting. An organization developed in 1910, WSN is the second oldest natural history society on the West Coast of the U.S. Every year since 1916, they have held a sort of science shin-dig as it were that has seen the likes of some of the most renowned ecologists in the field.

In celebration of a century of science and nerd-dom, 2016 WSN President Dr. Jay Stachowicz called on the help of the Society to (somewhat scientifically) compile an epic list of top 100 Most Influential Papers to Ecology. The Greatest Eva.

Over 450 papers were submitted to the bucket and out of those, 100 rose to the top of the salty brine. Check out the full list HERE. Unsurprisingly, Darwin’s Origin of the Species reigned supreme.

Also, if you are as cool as I am (I love data yes I do) and want to know how J.Stach sorted through it all… like any fine, upstanding Ecologist he laid out his methods and the caveats of his study HERE.

Let us know in the comments section what you would add to the list. Have any of our readers read all of these?

The post Last Name: Eva, First Name: Greatest first appeared on Deep Sea News.

I was smiling the whole time like the nerdy Ecologist I am. Happy Hump Day.

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In The Smithsonian Atlas of the Amazon, Goulding and co-authors Ronaldo Berthem and Efrem Ferreira take a spatially explicit  approach to the world’s largest river basin, exploring the major tributaries such as the Madeira, Xingu, Tapajos, Tocantins, and Negro, many of which would be mighty rivers in their own right, if only they drained into the sea instead of an even bigger basin.  Despite the name, maps do not make up the majority of the book.  Instead, it is full of photographs and explanatory text, describing the geological, climatological, sociological and ecological settings of each region.  Especially relevant are the discussions of the different habitat types including whitewater (muddy), clearwater and blackwater tributaries, as well as flooded forests full of frugivorous fish, floodplain lakes  with their meter-wide giant lilies, and vast floating meadows of grass munched by shy riverine manatees.   The maps are there more to help you understand where in this mind-bogglingly convoluted labyrinth of channels, lakes, forests and floodplains the current discussion is focused.  In that role, they’re perfectly applied, and I found the book to be immensely informative and surprisingly readable.  Then again, I’m the kind of guy who actually reads atlases, so what does that say?  Best discovery:  I had no idea that until the Andes were pushed up, the Amazon flowed the other way, from east to west, draining Eastern Brazil and Guyana into the Pacific somewhere in Peru.

The other book, Floods of Fortune: Ecology and Economy Along the Amazon, is co-authored  with Nigel Smith and Dennis Mahar and is a quite different critter.  This one takes a more historical narrative approach to explaining how the Amazon comes to be what we see today, both biologically and sociologically.  The different phases – pre-conquest, colonial, rubber, jute, livestock, fisheries – are defined with respect to the development of rural life and the major cities (especially Manaus) alike, along with civil projects like dams and highways and how they’ve generally failed to open the Amazon to anything that might be called sustainable development.  Instead, the Amazon has developed a litany of problems: overfishing, pollution, poverty, deforestation and introduced species.  In reading this I realised that, while much of the Amazon is part of sovereign Brazil, you can’t blame any one country, or indeed all of them, for the problems of the basin.  The thing that allows many of these problems to develop is the very same thing preventing the from becoming more serious: the sheer remote, inaccessible vastness of the ecosystems in question and the enormous refugia that this offers (to animals and criminals alike!).  Some parts of the forested floodplain are so remote that uncontacted tribes are still being encountered.  Think about that: uncontacted in 2010!  In reading Floods of Fortune I did find myself hankering for maps from time to time, especially when Goulding et al. were bandying around exotic names for places and peoples.  Perhaps it would not be so had I read it before I read the Atlas and not the other way around, but I doubt it.

Taken together, these two books provide a great introduction to the history and status of the worlds mightiest river system.  Certainly I was left with a sense of anxiety about the problems facing the basin, but also with profound hope that the Amazon is still big enough and unexplored enough that all is not lost.  Far from it; it seems clear that there is time and opportunity enough to conserve vast tracts of meadow, flooded forest, blackwater streams and muddy main channel, as long as we act decisively and with the interests of the people of the basin (both native and other) given equal consideration as the ecology.  Or rather, that the people are seen as part of that ecology.  If I had to pick one of the two, it would be the Smithsonian Atlas (that geographical context is just essential) but, really, you can’t go wrong.  Now, where’s my passport…

The post Twofer book review from the Amazon (the river, not the website) first appeared on Deep Sea News.

You might have noticed that my posting frequency is down recently.  Why?

1. Kevin Z convinced me to start Tweeting.  There seems to be an inverse relationship to my writing for DSN and posting Tweets.  Previous attempts to integrate our Twitter content into DSN were rocky at best and met with many complaints.  Suggestions on how to integrate the two meaningfully are welcomed. You can follow me at DrCraigMc

2. I am working on a review of this book for American Scientist.

3. I am also writing a feature article for American Scientist following on the theme of my talk last year at Sigma Xi.

4. Isopocaplyse 2010 consumed a bit of my time.  If you didn’t catch it already check out GlassBox Design and National Geographic’s coverage.  I am delightfully snarky!

5. I worked with the spectacularly talented Robin Smith to put together a press release and video for my recent paper in Ecology.  That was met with a fair amount of cricket chirping.  O’ well Bora, Science360, and I think its cool.

6. Multiple scientific papers in the works right now on deep-sea biogeography, source-sink dynamics in the deep sea, the evolution of body size in deep-sea bivalves, what drives the evolution of size on islands, describing the new species above, changes in energy consumption of snails through geologic time, changes in seamount diversity with increasing depth, and how microhabitat diversity in the deep sea drives biodiversity.  Whew!

7.  My day job.

8.  The fact there is only 24 hours in a day.

So what would I like to blog on but haven’t found time?

1. The discovery of the world’s deepest hydrothermal vent. It’s really hot and deep!

2. What will likely be the coolest discovery of the year and decade…anaerobic multicellular organisms in the deep sea.  This one is so cool I just decided to stay up late to write about it.  While I grab another Ardbeg and you wait for the next couple hours, check out Susan Milius’s spectacular write up.

3. Larvae from afar colonize deep-sea hydrothermal vents after a catastrophic eruption

Any other papers or news I should add to this list?

The post What’s New With the Dr. M and the Oceans? first appeared on Deep Sea News.

I am very excited today!  My new paper in the journal Ecology will be coming out in April on the regulation of biodiversity in the deep sea.  NESCent is issuing a press release (below) written by our very talented, Communications Director Robin Smith.  Above is a high-definition Youtube video we put together for the occasion.

Durham, NC – Surplus food can be a double-edged sword for bottom-feeders in the ocean deep, according to a new study in the April issue of Ecology. While extra nutrients give a boost to large animals on the deep sea floor, the feeding frenzy that results wreaks havoc on smaller animals in the seafloor sediment, researchers say.

Descend thousands of feet under the ocean to the deep sea floor, and you’ll find a blue-black world of cold and darkness, blanketed in muddy ooze. In this world without sunlight, food is often in short supply.

Animals in the deep sea survive on dead and decaying matter drifting down from above, said marine biologist Craig McClain of the National Evolutionary Synthesis Center. Only about 3-5% of the remains of microscopic plants and animals that feed life at shallower depths actually makes it to the deep sea floor, he explained. “If the ocean’s primary production were a 5-pound bag of sugar, that would be the equivalent of a sugar packet.”

Collaborating with James Barry of the Monterey Bay Aquarium Research Institute (MBARI), McClain traveled to the deep waters off the coast of California to an area of the ocean floor that receives an additional source of food. In a steep, winding, underwater gorge known as Monterey Canyon —similar in size to the Grand Canyon —bottom-feeders get a boost from nutrient-rich sediments that slough off the canyon walls and collect on the canyon floor.

“There’s typically more food available in the canyon than you would see outside the canyon,” Barry explained. “The stuff that rains down from above and accumulates at the base of the cliffs isn’t just mud – it’s food,” McClain added. “There are tiny food particles and bacteria in the sediment.”

The researchers wanted to understand how the surplus food affected deep sea life on the canyon floor. Buried in the sediment and hidden from view, a diverse world of tiny marine animals – snails, worms, crustaceans, clams, and other creatures no bigger than a pencil eraser – live and feed in the canyon mud.

To find out how these animals are affected by the boost of food, the researchers sent a Remotely Operated Vehicle (ROV) equipped with video and sampling equipment to the base of the canyon. Piloted from a control room onboard a ship at the ocean surface, the ROV dove more than a mile to the canyon floor. As the ROV crept across the seafloor sediment, it video recorded everything in its path and pushed plastic tubes into the mud, pulling up cores of and animals and silt.

When they brought the samples back to the surface, they found nearly 200 species in the sediment. But as they sampled closer to the canyon walls, they were surprised to find that despite the extra food and nutrients, the small sediment-dwellers (0.25 to 25 mm in size) became even smaller and less diverse. Why might this be?

A closer look at the video footage suggests the answer lies not in the sediment, but just above. As the ROV approached the canyon walls, the researchers noticed swarms of bigger, mobile animals – crabs, starfish, urchins, sea cucumbers and other seafloor scavengers – crawling on the sediment surface. Normally few and far between, these animals sense that food has arrived and converge at the base of the cliffs, the researchers explained. “The cliff face becomes a smorgasbord for larger animals,” said McClain.

Ironically, more food for big, mobile animals on the sediment surface is bad news for smaller sediment-dwellers buried below. The larger animals devour all the food in their path as they plow across the canyon floor, wrecking habitat and leaving little for other animals to feed on. “Larger organisms come in and they churn up the sediment and eat all the food. That has big consequences for smaller animals that live there,” McClain explained.

“The number of species near the cliff face was reduced by half compared to the middle of the canyon,” said McClain. “More food isn’t always better,” he added.

The team’s findings will be published online in the April 2010 issue of Ecology.

The post When the dinner bell rings for seafloor scavengers, larger animals get first dibs first appeared on Deep Sea News.

Enter the sieve. It is a marine biologists best friend, saving hours of sorting and enabling quantification of fauna. In fact you can get these miracle  workers at McMaster-Carr for a mere $40-50. You take good care of these puppies and they will last several graduate student’s lifetimes! I prefer the 500 micron mesh size myself, but usually on top of the 64. You see, those damn limpets (Scheißeschnecke!!) always foul things up. I mean, there are ALOT of little limpets in vent ecosystems. Govenar et al. 2002 found up to nearly 100,000 of these bastards per square meter in tubeworm clumps at the Juan de Fuca Ridge. Sorting tens of thousands of limpets can be quite drearisome and on the occasion you find something that is to be classified as no a limpet is a moment of silent (or not so silent) joy. Stacking different size sieves has been a strategy that I have partaken in extensively in my career of bean counting.

The sieve size I use at the bottom though is the most important. It is my cut off. I am essentially saying I will ignore anything which exists that can fall through this size hole. Though I would ideally like to have this be as low as possible, usually around 64 micron – the cutoff size for meiofauna, I am often limited by what size my colleagues have used in past studies. This is important because my results need to be compared to theirs if I want to understand general patterns in species compositions and community structure. But a new study, building upon a slightly older one, reminds us that instead, interpretations might be limited by sieve size.

Gage and colleagues published an important methodological paper in 2002 describing the influence of sieve size on characterizing a deep sea community. The graph to the left is from their paper and clearly shows the biomass, numbers of individuals and numbers of species significantly increasing for 2 independent box-core samples. About 20 more species were recovered by winnowing down from 500 micron to 250 micron mesh. Twenty species is no laughing matter. That can mean the difference between a significant treatment effect or “meh, nothing here”.

In a recent paper published in Marine Biology Research, Pavithran and colleagues took it a step further and asked if it mattered what type of animal was being shaken down the gauntlet. Using a replicated transect of box-cores in the Indian Ocean they looked at the effect a 200 micron difference in mesh size (between 500 and 300 microns) had in characterizing 7 very different animal groups: nematodes, polychaete worms, tanaids, a type of copepods, isopods, bivalves and nemertines (a worm-like animal).

The authors found the greatest difference in biomass occurred with the polychaetes, up to 90% reduction using the 500 micron mesh, followed by 78% reduction of nematode biomass. But a reduction in biomass doesn’t necessarily translate to a reduction in species present on the larger mesh size. After all, it could be smaller individuals of one or two major species retained on the smaller mesh. Unfortunately in this case it did translate, quick significantly too. The smaller mesh retained 66 species, while the larger mesh only 40. Additionally, there were nearly twice as many individuals on the smaller mesh sieve. This actually translates to a loss of 43% of the species, just from simple methodology choices alone!

What does this mean for interpretation though? As I mentioned above, one of the important things in designing a study is make sure your work will be comparable to the work of others. But if other researchers have been missing a certain size fraction of the animal community, should you ignore it too? Meiobenthologists would respond sharply with a very vocal NO! In fact, they would argue that the majority of deep-sea studies are just plain wrong and misleading at best since traditionally, they have ignored a potentially important component of the deep-sea benthos. Some of the world’s best nutrient recyclers are in that under 200 micron size class. So perhaps interpretations are in general limited, especially if you want to make grandiose claims about general principles or ecosystem functioning. But the data gleaned is still important nonetheless. My concern is that there is likely a size class of deep sea animals between 64 and 250 microns that have remained undiscovered in the several decades of experimental deep-sea ecology because we didn’t sieve down enough! Potentially 40-50% of deep sea macrofauna could have been thrown overboard during the last 50 years!

Gage, J., Hughes, D., & Gonzalez Vecino, J. (2002). Sieve size influence in estimating biomass, abundance and diversity in samples of deep-sea macrobenthos Marine Ecology Progress Series, 225, 97-107 DOI: 10.3354/meps225097

Breea Govenar, Derk C. Bergquist, Istvan A. Urcyuo, James T. Eckner, & Charles R. Fisher (2002). Three Ridgeia piscesae assemblages from a single Juan de Fuca sulphide edifice: structurally different and functionally similar Cahiers Biologie Marine , 43, 247-252

Pavithran, S., Ingole, B., Nanajkar, M., & Goltekar, R. (2009). Importance of sieve size in deep-sea macrobenthic studies Marine Biology Research, 5 (4), 391-398 DOI: 10.1080/17451000802441285

The post (Sieve) Size Matters first appeared on Deep Sea News.

This is a tale of cause and effect in the deep sea woven by threads of hypotheses held together by the loom of targeted sampling efforts and multiple lines of evidence. You see, dear readers, once upon a time existed an observation. Hovland (1989) noticed along the Norwegian coastline that carbonate reefs occurred in sediment laden with detectable concentrations of methane and oil. This led him to suggest that

“such reefs form at locations containing high concentrations of bacteria and other microorganisms suspended in the water column as a result of seeping fluids (solutions and gases) that provide some of the energy basis and carbon source for ecosystems independently of photosynthesis.”

Over the course of the last 20 years that hypothesis has been refined by several lines of evidence to suggest that

“the coral reef is located at this exact location due to sub-surface hydrogeologic properties, i.e. that there is an upward seepage of hydrocarbon-charged porewater on which bacteria and other micro-organisms thrive, thus providing suspension-feeders, including the corals, with a substantial and reliable food source.” (Hovland & Thomsen 1997)

This is known as the “hydraulic theory” for reef occurrence. My colleague and former labmate Erin Becker just published a study which sheds more light on the coral-seep relationship.

Lophelia pertusa community in the deep Gulf of Mexico. Photo from the NOAA Photo Library (click image) and available in the public domain.

For the last several years I’ve had the unfortunate circumstance of cooking with electric stoves. Just last February, my wife and I bought our first house and moved in. Now, we are blessed with a propane line and have the wonders of clean burning fire at my culinary disposal. But it turns out I’m not the only organism that prefers to use gas. In the deep Gulf of Mexico lurks a secret underground society of gasiverous microbes! There bacteria and archaea work in concert to utilize methane and hydrogen sulfide (rotten egg gas) as an energy source and carbon backbone for building metabolites. The byproduct of this microbial consortia results in the carbonates. In other words, these microbes essentially ‘poop’ out rock!

Becker and colleagues studied if the deep sea coral Lophelia pertusa occurs near active oil and gas seeps because it eats organisms associated with the seepage. The carbonate outcrops dot the seafloor landscape around continental margins and provide a roost for other animals like corals and barnacles. These animals like to take advantage of being positioned above the seafloor in order to capture food in the water. Perhaps the methane seeps provided a wealth of locally derived primary production of essential nutrients in the form of particulate matter. If sessile, filter-feeding animals are located in the right place they might surely take advantage of seep-derived mana from the abyssal heavens.

To understand if corals and the animals, such as crabs and polychaete worms, are fueled on gas the authors looked at the tissue stable isotope concentrations for carbon, nitrogen and sulfur – all important elements that are obtained from eating other stuff. Stable isotopes are useful tracers of an animal’s last meal. The old adage “you are what you eat” is actually true to some extent. Each animal has a slightly different signature of stable isotope ratios that reflect the signature of its food item. This cascades down to the primary producer that was able to fix inorganic carbon from carbon dioxide or methane into simple sugars or other metabolites. For instance, many cnidarians capture copepods with their stinging cells, called nematocysts. If that is mostly what they eat then the coral’s tissue would have stable C, N, and S ratios that were similar to the prey. Likewise, if that copepod ate an alga, then its tissue stable isotope concentrations would resemble the alga’s. The alga is a photosynthesizer and fixes carbon dioxide using solar energy. The original stable isotope values depend on the source of inorganic carbon and the metabolic pathway the carbon molecules were shoved through. This is called fractionation. Carbon has the stable isotopes C-12 and C-13. C-12 is lighter and moves through most metabolic pathways more quickly than the slightly heavier C-13. Therefore most animal tissues are “depleted” in C-13 relative to C-12.

Biologists can exploit the difference in fractionation to determine potential food sources for the animals. The process by which methane is fixed by chemosynthesis versus carbon dioxide is fixed by photosynthesis can produce vastly different values. The same process works for sulfur, where the oxidation of sulfides is used as an energy source to fix inorganic carbon. Nitrogen is a little more complicated but is useful as a food web tracer. Each isotope fractionates in predictable ways that has been tested hundreds of times in decades of literature (with caveats of course…). That is, every time a critter eats another critter and transforms the tissue of the prey into fat reserves, muscle mass, etc. the stable isotope signature of the prey is incorporated in the biomass of the predator, but the values shift in predictable ways that correspond to trophic levels.

Becker and colleagues found that while coral communities shared several of the same animals found at seep communities, the tissue stable isotope values of the coral and its inhabitants did not reflect a strong signature characteristic of a gas-fueled ecosystem. One exception was a small snail called Provanna sculpta, which had much more depleted C-13/C-12 ratios than the other coral fauna and reflected a metabolic pathway based on oxidation of hydrogen sulfide. This finding could mean that this snail has chemoautotrophic endosymbionts, a condition found in some close relatives in the Provannidae.

But perhaps early in the coral’s life history, during settlement and its initial growth stages, the coral was reliant on seep primary production. The coral skeleton is a record of its history. It tells a story along the length of its intertwining branches. In this living book are chapters on oxygen concentrations, temperatures, and food sources depending on the isotopes being used.

Becker and colleagues took samples along the length of the coral, from the base where the young coral larvae once settled and attached itself to the carbonate to the tips where the only evidence of active growth remain. Two results stood out. First, there was no indication of seep derived stable isotope signatures in even the most basal part of the skeleton. Second, there was no difference from the base to the tip in isotope signatures suggesting that settlement occurs after active seepage has passed. Additionally, the signatures of the carbonate rock it settled upon were different from Lophelia’s skeleton indicating that it was derived from gas-fueled or other microbial processes.

So does this turn the burner off of the flames of the hypothesis linking deep sea corals to methane seeps? While the corals in the Gulf of Mexico do not rely upon chemosynthetic primary production, they do thrive from its byproducts. Deep sea corals support communities similar to those of seep tubeworms, defined by high standing stock biomass, high abundance of associated fauna and similar species composition. This is more telling of the community. It is not endemic to seeps but can thrive in nonchemosynthetic-based ecosystems as well. In their words:

L. pertusa communities rival adjacent vestimentiferan associated communities in biomass and abundance of the associated fauna. We have long known that the high biomass assemblages of seep fauna are possible because of abundant local primary production fueled by migrating hydrocarbons in the otherwise nutrient-poor deeps-sea environment. Although L. pertusa often colonized carbonate that was only meters away from vestimentiferan aggregations, the results of this study show that the occurrence of L. pertusa at seep sites in the Northern Gulf of Mexico is not primarily due to reliance upon seep-derived nutrition, as hypothesized in the hydraulic theory (Hovland and Mortensen, 1999 [KZ note-but see Hovland & Thomsen 1997 for their ideas in an english language paper]). Rather, seep-induced features such as carbonate occurrence and uneven bottom topography provide appropriate substrate and may drive other processes relating to provision of food, such as current acceleration, bottom mixing, and nutrient concentration.

References:

Becker, E., Cordes, E., Macko, S., & Fisher, C. (2009). Importance of seep primary production to Lophelia pertusa and associated fauna in the Gulf of Mexico Deep Sea Research Part I: Oceanographic Research Papers, 56 (5), 786-800 DOI: 10.1016/j.dsr.2008.12.006

Hovland, M. (1989). Do carbonate reefs form due to fluid seepage? Terra Nova, 2 (1), 8-18 DOI: 10.1111/j.1365-3121.1990.tb00031.x

Hovland, M., Mortensen, P.B., 1999. Norske korallrev og prosesser i havbunnen (Norwegian coral reefs and seabed processes). Bergen 167 pp.

Hovland, M. & Thomsen, E. (1997). Cold-water corals—are they hydrocarbon seep related? Marine Geology, 137 (1-2), 159-164 DOI: 10.1016/S0025-3227(96)00086-2

Hovland, M. (2003). Do Norwegian deep-water coral reefs rely on seeping fluids? Marine Geology, 198 (1-2), 83-96 DOI: 10.1016/S0025-3227(03)00096-3

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