Accretionary Wedge #3: Between a Rock and Squishy Face, Geology and Life

n=1That is our sample size, our replicate number with 0 degrees of freedom. If you believe the most popular estimates, Earth is ~4.6 billion years old. For a long time only rock existed once the planet cooled. Out of rock came life. Perhaps not literally, but only certain raw materials were present to work with: Nitrogen, Oxygen, inorganic Carbon, Hydrogen, Sulfur. Perhaps metals provided the catalyst, perhaps the Flying Spaghetti Monster reached down to bless our planet with His noodly appendage. The answer isn't clear, but I can guarantee its written in the rocks.

Geology has had an intimate relationship with biology, a long term romance spanning at conservative estimate around 3 billion years. As the disciplines of each are concerned, they were inseparable until the mid-19th century. Both were included with the modern sciences and maths as the study of Natural History, a subset of Theology. Some might say that the discipline of Geology was born with the work of James Hutton and Alfred Gottleib Werner in the 18th and early 19th centuries. Later on with the work of Charles Lyell, which heavily influenced Charles Darwin's theory of evolution by natural selection, Geology became a subject to study in its own right regardless of other subdisciplines of Natural History. Several years after which Biology was separated from Medicine and Natural History with the work of Darwin and Thomas Huxley and many others that followed into the 20th century.

Life exists, establishes and persists with geology's permission. Natural disasters can wreak havoc wiping generations of establishment and millenia of adaptation and diversity. Yet out of the ashes rises the phoenix and life reestablishes and re-adapts, and modifies the geological environment. Lichens break down rock into soil, plants establish their roots and suck out minerals and add organic carbon, microorganisms and meiofauna recycle and mobilize nutrients in the soil, animals enrich the soil both while living and dead. In the ocean, microscopic organisms extract calcium and silica to form tiny houses. These fall to the ocean depths as they die. After several thousands of years, this ooze layers on top of itself hardening and combining with weathered rock debris to form the substrate of Earth's most extensive habitat, the abyssal plain. Life may exist by geology's consents, but with a price.

The submissions received for this edition vary widely on the theme but are all enjoyable reads! For any new readers to the Accretionary Wedge, it is a geology-themed carnival started a couple months ago. Click on the link in the last sentence to find out more about it and consider submitting articles and hosting future editions.

Like me, Brian from Clastic Detritus has to write his dissertation. We can't just blog our lives away right? It also doesn't pay very well, or at all... But he was kind enough to take a break and submit an article on trace fossils he has found while doing his research. Check out the monster Ophiomorpha!

Also blogging on dissertation research, I present the introduction to my thesis proposal in the first part of a week long series of Dissertation Blogging as I prepare for my comprehensive exams in less than 2 weeks (I have to keep reminding myself). Prepare to be amazed by hydrothermal vents at back-arc basins!!

Chris from Zoogeomorphology Brilliant Mediocrity avoided talking about his thesis research, but captures the essence of the theme posting how life interacts with and modifies its environment using examples from beavers and whales.

Chris #2 from Highly Allochthonous, already completed his dissertation, takes a "grand and sweeping look at Geology and Life" and discusses how the air breathe became breathable in a BPR3-certified article.

Christopher (not to be confused with a Chris) from the Catalogue of Organisms highlights beautiful New Zealand serpentine soils and the plants the establish there. In an earlier post, he discusses a recent Nature paper on continental collisions with this loverly quote:

"Great chunks of the planet's surface get ripped up by colliding masses of rock bigger than all imagining, at scales at which living organisms just become negligible."

In a related post from earlier this year, brought to my attention by Yami from Green Gabbro, Joseph from the blog Science, AntiScience and Geology discusses research suggesting that the geochemical influx from the building of Gondwana may have triggered the Cambrian Explosion. Unfortunately, it seems seems these geologists may have disregarded some important biological information

Brian from the newly sexed up Laelaps, professes his love of squishy things and waxes beautifully and poetically on Aldo Leopald, the Book of Job, and Charles Darwin.

Julia at the Ethical Palaeontologist uses volcano farts as a segway segue into a discussion of volcanism and the public perception of climate change.

From the very cleverly titled All My Faults Are Stress Related, Kim ponders the granitic soil and its properties that make those oh so delicious blueberries grow there and be so... delicious!

Neil of Microecos reminds us to take a close look around us in public buildings. Fossils are everywhere in architecture and monuments!

Although Harold at Ontario-Geofish *claims* it happened to a friend, he discusses why one should go the emergency room and not try to solve medical problems with beer, especially urinary tract infections. Though not scientific, I thought there were lessons to be learned for field researchers in there.
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Thats all for for edition #3 of the Accretionary Wedge. Next month's Wedge will be hosted at GoodSchist and please go the Accretionary Wedge page to submit ideas for the next and further editions.

Dissertation Blogging, Part 1: Introduction

*This marks my 200th post. In preparation for comprehensive examination in less than 2 weeks and because its International Dissertation Writing Month, I will be posting my thesis proposal as I madly try to finish it all in time over the next few days. Feel free to question, correct, nitpick, criticize (constructively, I'm in a fragile state right now!), comment, praise me and make suggestions for improvement. And yes, I'm freakin' out!!!!
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Biodiversity of Chemosynthetic Communities at the Eastern-Lau Spreading Centre

Many communities persist due the presence of a foundation species. Dayton (1972) defined a foundation species as an large, influential species that has a positive effect on community inhabitants through modifying environmental parameters, species interactions and resource availability. It is hypothesized that foundation fauna can ameliorate abiotic stress by modifying the chemical and physical environment (Bruno et al. 2003). The refuge provided by the foundation species increases abundance, biomass and diversity of other associated species (Bruno & Bertness 2001). Many chemoautotrophic megafauna at hydrothermal vents are foundation fauna that live in environments with high concentrations of toxic chemicals, heavy metals, high temperatures and low oxygen concentrations. Chemoautotrophs may modify the physical and chemical habitat (Johnson et al. 1994, Shank et al. 1998) and provide structural heterogeneity (Govenar & Fisher 2007), making the local environment more amenable to less tolerant colonizers (Shank et al. 1998). My research aims to test hypotheses relating environmental stress to the species composition and diversity of chemosynthetic communities at the Eastern-Lau Spreading Center (ELSC). Additionally, I will investigate the trophic ecology and food web structure between communities associated with three chemoautotrophic foundation species.

This thesis work is part of a larger project investigating the geology, chemistry, microbiology and ecology of deep-sea hydrothermal vents at the ELSC. Back-arc basins are the result of a complex plate tectonics setting where two or more oceanic plates converge with one plate subducting beneath the other(s). The friction caused by the subducting plates’ movement melts the rock along the plate boundary causing a volcanic arc to form on the overlaying plate. On the backside of that arc, a spreading centre is created as a result of the extensional forces of the subduction. Where back-arc spreading occurs, the crust is thin and fragile (see figure below). Seawater seeps down into cracks and fissures and comes into contact with super-heated rock. The seawater is heated and rises, carrying reduced chemicals and heavy metals in solution, which exits the crust at the seafloor and precipitates out of solution creating hydrothermal vent chimneys. Bacteria have evolved metabolic pathways to utilize the energy from oxidizing some of these reduced chemicals such as sulfides and methane. Furthermore, several metazoans have evolved a symbiosis with these bacteria with the result being abundant communities surrounding many vents worldwide.


The hydrothermal vent ecosystem is based upon chemosynthetic primary production and offers an opportunity to empirically test various measures of the diversity-stress hypothesis. At the ELSC, 3 major chemoautotrophic foundation species occur in dense aggregations: the snails Alviniconcha hessleri and Ifremeria nautilei and the mussel Bathymodiolus brevior. Henry et al. (submitted) have found clear differences in the thresholds for maximum H2S and minimum O2 concentrations and maximum temperatures for the three foundation species. Podowski et al. (submitted) have found significant differences in situ of H2S, O2 and temperature measurements between each of these community types, supporting the hypothesis that each foundation species occupies a specific thermo-chemical microhabitat. Furthermore, they occupy a gradient of stress, similar to a “bull’s eye” pattern, with A. hessleri in the highest stress environment (high H2S, low O2, high temp.), B. brevior in lowest stress environment (low H2S, higher O2 and near ambient temp.) and I. nautilei occupying an intermediate position with overlap on both ends. This well-defined gradient allows me to test the relationship between species diversity and stress.

Bathymodiolus brevior (Mytilidae)
At vents, stress can be ameliorated by chemoautotrophic foundation species by removal of sulfide from the environment (Johnson et al. 1988, Johnson et al. 1994). Mussel beds in low vent flow at the Galapagos Rift Zone vents have been shown to diffuse venting laterally and removal experiments have shown that sulfide concentrations above the mussel bed are lower pre-removal (Johnson et al. 1994). Stress reduction, by way of vent flow diffusion and sulfide removal, should increase with biomass of the foundation species if facilitation were an important factor in structuring communities associated with a foundation species. I hypothesize that diversity should increase with foundation species biomass (greater stress reduction) to a point where the response curve asymptotes at the maximum local species diversity. If competitive exclusion played a role in structuring these communities, then according to theory diversity is predicted to be greatest at intermediate levels of stress (Bruno et al. 2003). Since I. nautilei inhabits an intermediate position in stress tolerance, I would expect to see its associated community have the highest mean diversity.

The ELSC is further characterized by two different substrate types: lava tends to exhibit more basaltic characteristics in the north and andesitic in the south. The physical and chemical properties of these lava types are subtly different, but may have implications for how the hydrothermal venting regime is distributed over space. Preliminary evidence suggests that andesite, a more pliable and porous lava type, diffuses venting laterally more than basalt. This has implications for the fauna living on each lava type. This observation leads to the prediction that communities on andesite hosted substrate will have higher biomass and greater diversity than communities on basalt hosted substrate. The effect of substrate may be confounded by lateral diffusion by beds of mussels, and presumably snails. Even so, the greater diffusivity of andesite may act synergistically the diffusive activity of the mussel and snail beds to increase the amount of habitat that can support their respective associated communities.

Ifremeria nautilei (Provannidae)
The communities associated with these foundation fauna are poorly documented and the biological literature for this area consists mainly of taxonomic descriptions and video observations. Rapid progress is being made in understanding the ELSC communities due to the 2005 and 2006 expeditions to the area. Podowski et al. (submitted) built upon the limitations imposed by the laboratory setting of Henry et al.’s (submitted) physiological work of the chemoautotrophic species by measuring in situ chemical concentrations and temperature measurements of communities as a whole. Though their findings were novel and furthered our understanding of these communities, but Podowski et al.’s work was limited to the 2-dimensional view of the surface of the communities. Thus, diversity was biased against smaller fauna and those that lived within the foundation species’ matrix and not at the surface. Inferences on abundance, biomass, diversity and trophic interactions to the communities as a whole are thus limited. In order to understand how the communities associated with chemoautotrophic foundation species are structured, I collected 36 quantitative whole-community samples nested within site, which is nested within substrate (basaltic or andesitic). Each community is based on collections of one of three chemoautotrophic foundation species, confirmed upon retrieval as dominants in terms of abundance and biomass. Mixed communities, defined arbitrarily as the dominant foundation species composing 75% or less of the total foundation species abundance or biomass, were collected a priori and discovered a posteriori upon retrieval. I recognize that sampling may be biased by collecting from sites where the research team concentrated most of their multidisciplinary studies and by collecting the communities observed to be best collected by our sampling device. Sampling is thus haphazard and not random.

Alviniconcha hessleri (Provannidae)
The hydrothermal vent food web is structured upon bacterially-derived chemoautotrophic primary production (Jannasch 1985). Bacteria may be free-living or in an endosymbiosis with a wide range invertebrates (Childress & Fisher 1992). There is evidence for the cycling of chemoautotrophic-derived nutrients through consumers at vents and exportation of these nutrients outside the vent system (Van Dover & Fry 1989, Fisher et al. 1994, Van Dover & Fry 1994, Bergquist et al. 2007). Tunnicliffe (1991) constructed the first general food web model of the vent ecosystem which was later expounded upon by Bergquist et al. (2007) for the Juan de Fuca vent ecosystem. Their models included 3 producer pools (subsurface bacteria, bacterial mats on the surface and symbiotic bacteria) and 4 consumer pools (grazers, scavengers/detrivores, suspension feeders, predators and endosymbiotic hosts) interacting through four trophic pathways. Bergquist et al. (2007) recognized the utility of investigating trophic structure in a quantitative community setting in order to compare those results to community characteristics, but their analyses were limited to only one community. In order to better understand the relationship between community characteristics and trophic structure, I will analyze stable isotopes of fauna from quantitative collections on both andesitic and basaltic substrates.

While identifying and enumerating species for the community ecology portion of my research, I became very interested in systematics. This is due to my own personal fascination with diversity and to the fact that many species remain undescribed. The ELSC fauna are taxonomically similar to fauna from other biogeographic provinces. One such example are species are shrimp in the family Alvinocarididae. They have so far been found only at gas/oil seeps and hydrothermal vents worldwide. I am describing, with a colleague from France, a new species of Alvinocaris from the ELSC that is morphologically most similar to A. lusca from the Galapagos Rift Zone and East Pacific Rise. This species phylogenetic placement, based only on the COI gene, is somewhat obscured and awaits further phylogenetic analysis with a wider array of nuclear and mitochondrial genes. Another interesting taxonomic group are the cnidarian fauna of the ELSC. The Cnidaria have not been reported to make up a significant portion of the community at vents in the Pacific and Atlantic Oceans. Eight species from five biogeographic provinces have been described. Only recently have they garnered attention as dense communities of anemones been observed at Central Indian Ridge vents (Van Dover et al. 2001). Our recent expeditions to the ELSC have discovered another densely populated community of mixed anemones and zoanthids. With colleagues from the Ohio State University, I am describing seven new species of anemone and one new species of zoanthid. The zoanthid and four of the anemone species live within the influence of hydrothermal vent flow. An additional species is found both near vents and in the ambient deep sea community. The remaining 2 anemone species are found in the ambient deep sea community only. The proximity of these cnidarians to vent effluent suggests a link to chemoautotrophic primary production. The additions of these new species of shrimp and cnidarians from ELSC fills gaps in the western Pacific back-arc basins that aid in our understanding of the biogeography of hydrothermal vent fauna.

An additional study I have undertaken is a stable isotope bioassay for primary production of particulate organic matter (POM) at methane seeps in the Gulf of Mexico using filter-feeding taxa. Previous studies have focused on primary production from the standpoint of the chemoautotrophic symbioses or free-living bacteria found in and on top of the sediment at seeps. Little attention has been given to the role of seeps in creating POM that enters the water column, despite the observations of suspension-feeding invertebrates at and near seep communities (i.e. tubeworm aggregations, mussel beds). Since filter-feeders directly uptake the POM in the water column, their tissue stable isotope values are point estimates of the available POM at that time. Stable carbon, nitrogen and sulfur isotope ratios for methanotrophy at seeps are distinct from photosynthetic-derived nutrients that fall down from surface water. We can exploit this difference in food source “signatures” to approximate the input of seep-derived primary production of POM relative to photosynthetic primary production of POM. I used a 2 end-member stable isotope mixing model to approximate the relative contribution of seep-derived nutrients to the POM pool at a methane seeps. Interestingly, about ¼ of the POM can be attributed to methane seep primary production of POM. This is my first chapter, so it will comprise the next edition of Dissertation Blogging!

**Photographic images are copyright C.R. Fisher/Ridge2000 Program**

Literature Cited

Bergquist DC, Eckner JT, Urcuyo IA, Cordes EE, Hourdez S, Macko SA, Fisher CR (2007) Using stable isotopes and quantitative community characteristics to determine a local hydrothermal vent food web. Marine Ecology Progress Series 330:49-65

Bruno JF, Bertness MD (2001) Habitat modification and facilitation in benthic marine communities. In: Bertness MD, Steven D. Gaines, Mark E. Hay (ed) Marine Community Ecology. Sinauer Associates, Inc., Sunderland, MA, p 201-218

Bruno JF, Stachowicz JJ, Bertness MD (2003) Inclusion of facilitation into ecological theory. TREE 18:119-125

Childress JJ, Fisher CR (1992) The biology of hydrothermal vent animals: physiology, biochemistry and autotrophic symbioses. Oceanography and Marine Biology: An Annual Review 30:337-441

Dayton PK (1972) Toward an understanding of community resilience and the potential effects of enrichments to the benthos at McMurdo Sound. In: Proceedings of the Colloquium on Conservation Problems in Antarctica, p 81-96

Fisher CR, Childress JJ, Macko SA, Brooks JM (1994) Nutritional interactions in Galapagos Rift hydrothermal vent communities: inferences from stable carbon and nitrogen isotope analyses. Marine Ecology Progress Series 103:45-55

Govenar B, Fisher CR (2007) Experimental evidence of habitat provision by aggregations of Riftia pachyptila at hydrothermal vents on the East Pacific Rise. Marine Ecology 28:3-14

Jannasch HW (1985) The chemosynthetic support of life and the microbial diversity at deep-sea hydrothermal vents. Proceedings of the Royal Society of London B 225:277-297

Johnson KS, Childress JJ, Beehler CL, Sakamoto CM (1994) Biogeochemistry of hydrothermal vent mussel communities: the deep-sea analogue to the intertidal zone. Deep-Sea Research I 41:993-1011

Johnson KS, Childress JJ, Hessler RR, Sakamoto-Arnold CM, Beehler CL (1988) Chemical and biological interactions in the Rose Garden hydrothermal vent field, Galapagos spreading center. Deep Sea Research Part A Oceanographic Research Papers 35:1723-1744

Shank TM, Fornari DJ, Von Damm KL, Lilley MD, Haymon RM, Lutz RA (1998) Temporal and spatial patterns of biological community development at nascent deep-sea hydrothermal vents (9deg.50'N, East Pacific Rise). Deep-Sea Research II 45:465-515

Tunnicliffe V (1991) The biology of hydrothermal vents: ecology and evolution. Oceanography and Marine Biology: An Annual Review 29:319-407

Van Dover CL, Fry B (1989) Stable isotopic compositions of hydrothermal vent organisms. Marine Biology 102:257-263

Van Dover CL, Fry B (1994) Microorganisms as food resources at deep-sea hydrothermal vents. Limnology and Oceanography 39:51-57

Van Dover CL, Humphris SE, Fornari D, Cavanaugh CM, Collier R, Goffredi SK, Hashimoto J, Lilley MD, Reysenbach AL, Shank TM, Von Damm KL, Banta A, Gallant RM, Götz D, Green D, Hall J, Harmer TL, Hurtado LA, Johnson P, McKiness ZP, Meredith C, Olson E, Pan IL, Turnipseed M, Won Y, Young III CR, Vrijenhoek RC (2001) Biogeography and ecological setting of Indian Ocean hydrothermal vents. Science 294:818-823

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*This post was updated on Nov. 30 after I made substantial changes to my thesis proposal after reading comments from my advisor.

I Really Am A Genius

Cash Advance Loans

Just because my ego needs to be inflated more. Like Björn Brembs says, "it probably means incomprehensible".

Tuesday Toon

Another classic from Gary Larson's Bride of the Far Side.

Invertebrates 3: Vertebrates 1

Rick has gotten a point for the vertebrates. Although a cheeky one at that. An epic battle between an octopus and moray in which the weakened octopus escapes the wrestling clutches of the moray with the ink tactic only to be picked off by a couple of spectator fish. But inverts won the battle in this one, just not the war. Hence, I concede.

Invertebrate 3: Vertebrates 0

First I brought you Octopus vs. Shark
Then came Centipede vs. Mouse
and now...

Centipede vs. Bat
When will this madness stop!! The absence of sound on this pirated YouTube video only makes it more eerie. For those wanting to hear David Attenborough's soulful narration, go here. This is a giant Amazonian centipede (genus Scolopendra, probably S. morsitans) taking down a bat in midflight. Sweet.

Thanks to Ed Yong for bringing this to my attention.

Glamorous Insects!

A friend sent me this webpage from Dark Roasted Blend on Glamorous Insects. Though they are not all insects, these unbelievable macro photos are better than National Geographic quality. I will steal one just to get you to go over there and see the rest! I really love the mantids.

Invertebrates 2: Vertebrates 0

If you aren't keeping score, Invertebrates 1: Vertebrates 0 was an octopus taking down a shark. Here we have a Vietnamese Giant Centipede (named Father Christmas by the proprietors of the YouTube video), Scolopendra subspinipes, taking down a typical mouse. This video was being watched by my intro bio students this morning while doing a "Diversity of Life" lab. This group was doing the animals and picked out the leech to do there class presentation on over any vertebrates. I am proud I must say. When discussing the leech reproduction, they referred to it "sexytime". Nice.

Carnival of the Godless

One of my favorite blogs, Aardvarcheology, has the latest and greatest Carnival of the Godless up! Included is my Vlog on why the spineless are atheist.

Let It Be Known...

... that today, November 11th 2007, my nearly 2-year old son uttered the following words from mouth: "Octopus". Well it sounded more like "ockpoos". I am so proud. His first invertebrate was "fly" (meant for butterfly and fly), followed by "snail" and "shell". I think it is about time we start working on latin names.