Sander, Sylvia G. and Koschinsky, Andrea. Metal flux from hydrothermal vents increased by organic complexation. Nature Geoscience 4:145-150. 20 February 2011.
The concentration of metals such as iron and copper is highly relevant to biological and chemical processes throughout the ocean, and as such understanding where exactly these come from is vital to a holistic comprehension of the deep ocean. This paper was written to challenge the contemporary understanding that the primary contribution of hydrothermal vents to the greater metal concentration in the open ocean was negligible, almost all of the metals presumably forming sulphide and oxide compounds upon contact with seawater and so fairly localized to the surrounding sea floor. These two authors realized that, in addition, there is also the possibility of these ions forming highly stable ligands with organic molecules (formed either biologically or through interaction of organic carbon compounds with increased H2 present in hydrothermal fluid), which would allow for the spread of molecules into the greater deep ocean, potentially contributing a significant portion to the observed concentrations of metals. This was tested using a modeling path called REACT, in which organic ligands’ binding proficiency was simulated to predict metal solubility in ocean water using metal flow data from the Turtle Pits and Rainbow field vent systems. The model found that solubility of both metals increased with the presence of ligands, with ‘assumed’ hydrothermal ligands playing a greater role in complexing with copper in anoxic conditions, and seawater ligands contributing more significantly when oxygen is introduced to the system. Iron binding ligands were found to be more effective with the iron was oxidized to form Fe(III). This experiment demonstrates the complexing ability of organic ligands, and the required diversity of ligands to complex in varying conditions. This strongly suggests that hydrothermal vents indeed act as a source of metal, potentially making up 14% and 9% of the dissolved deep ocean copper and iron concentrations respectively.
This paper does a good job of identifying an issue and seeking to contribute to its resolution – in this case the lack of knowledge surrounding hydrothermal vents’ contribution to metal concentrations in the deep ocean. However, as useful as modeling systems are, the paper did not itself conduct any concrete experiments to support their theory, merely noting that their model appears to line up, more or less, with the observations. The authors also admit that their model did not take into account the breaking up of sulphide compounds, or biological processes that could affect iron or copper solubility. What is needed now is a series of experiments that validates the predicted complexing ability of ligands in hydrothermal vent systems specifically, as well as a study into the two unaccounted processes mentioned before, as it is often found that in situ behavior can differ radically from modeling or in vitro experiments. The paper also brings up a possible interaction between sulfide nanoparticles that also bind to metals, acting as a potential medium as they travel to increasingly oxic waters, at which point organic molecules would steal the bound metals and keep them dissolved. This is an area worth studying as well, to promote the complete understanding of the chemical processes required to transport these metals long distances.
Glover et al. ”World-wide whale worms? A new species of Osedax from the shallow north Atlantic”. Proceedings of the Royal Society B. University of Hawaii, 272: 2587-2592. 18 October 2005.
Whale falls present a unique landscape of organisms that feed off decaying whale carcasses, including Osedex species known for their ability to root themselves within whale bones. However, studies done up to the point of the paper have focused exclusively on very deep portions of the Northeast Pacific ocean, and no experiments done out of the laboratory have focused on shallower north Atlantic waters. In order to shed new light on the diversity of species that surrounds whale falls in that area, the authors dumped a Minke whale carcass near the southwestern coast of Sweden at a depth of 125 meters in late 2003. In August of the following year, and twice in 2005, a remote operated vehicle Phantom XL was used to collect samples of the whale remains and a novel species Osedex mucofloris. Genetic sequencing of their mitochondrial cytochrome oxidase 1 and the 18S rRNA subunit gene demonstrated a close relation to Osedax frankpressi, although significant morphological differences including variation in palp and root system color, size, and distinguishing genetic difference of CO1 and 18S rRNA sequences established the species as unique. This identification the growing understanding of the phylogenetic relationship these worms share with vent and sediment worms. For example, Osedax mucofloris is also shown to derive from vent worms sucha as as Riftia and Tevnia, just like the other Osedax sp. The geographic distribution of the worm, which is also present in the Northeast Pacific, appears to be at odds with the phylogeny however, as the two northeast Pacific species of Osedax were present on the Swedish whale fall, even though they don’t act as sister clades to mucofloris, which according to the authors implies an unexpected method of distribution.
The significance of this phylogeny suggests the species were transported through some sort of dispersal or migration event, as opposed to the more common movement of tectonic plates that commonly determines the diaspora of these types of worms. This paper also brings into question current knowledge of the many species found in the deep sea, or around whale falls. In addition, the authors point out that the specifics of symbiont related feeding have not been explored, although presumably these worms also utilize sulfur oxidizing chemoautotrophs.
Robert et al. “Small-scale thermal responses of hydrothermal vent polynoid polychaetes: Preliminary in situ experiments and methodological development”. Journal of Experimental Marine Biology and Ecology. Elsevier, 420-1: 49-76. 3 May 2012.
The authors of this paper were concerned with the specifics of temperature regulation among two types of worms from the family Polynoidae. These creatures depend very heavily on the temperature of their environment to regulate their own internal temperature, a physiological condition of which applicable organisms are termed ectothermic. These polychaete worms must first remain within survivable temperature ranges, but then additionally maneuver on a much smaller scale of centimeters or decimeters to optimize temperature and access to food. The authors specifically were looking to confirm predictions on movement patterns based on optimal temperatures and the influence of past temperature exposures on these locomotive trends. Based on previous polychaete studies, the Branchinotogluma family and Lepinotopodium piscesae species could not be distinguished, and instead identification was divided into worms with and without visible epibacterial growth on their scales. The human operated submersible Alvin was outfitted with cameras and thermometers and deployed three times on the Grotto chimney of the Main Endeavour Field, and once at the Axial Volcano. Tracking of the worms was then mostly automated in ImageJ after editing in Adobe Photoshop to increase contrast between polychaete scales and the background. Observed walking patterns were compared with a simulated randomized walking pattern, while a temperature map within the camera’s field of view was constructed through Kriging interpolation, which models likely temperatures at points in the area that were not directly measured. The effect of previously encountered temperatures was analyzed by comparing the time interval between experiencing an extreme temperature and subsequent movement to a more comfortable area, and comparing each time’s respective temperatures. Finally, movement patterns were analyzed using a certain modeling technique that determines the degree to which previous behaviors of eating or migrating influence more recent behaviors. When movement was compared with random motion across the constructed temperature maps, worms with epibacteria tended towards the 35-40 oC range less than predicted with a random model, and worms without epibacteria demonstrating similar behaviour in the 30 – 40oC range, while both tended towards the more moderate 5-10 oC or 20-25oC range, depending on the dive. This suggests that polychaetes do exhibit smaller scale temperature optimizing ectothermic activity. There was unfortunately no conclusive data found on the impact of previously exposed temperatures on displacement or velocity of the worms in the area – they tended simply to stay put. There was also no conclusive evidence of migrating behaviors, in which worms were expected to stay localized sometimes or move relatively quickly at others, based solely on temperature. Overall, the study confirmed a preference for milder temperatures, but also strongly suggested that there must be other environmental factors that trump temperature when determining location.
This paper explores very interesting possibilities in worm behavior and modeling techniques. There clearly must be more motivating factors, aside from temperature, that determine location. There is also much left to be explored when distinguishing polychaetes with and without a layer of epibacteria, as some differences in temperature range where demonstrated. Future studies would need to address this, as well as providing a more detailed sea floor layout, as the one used in the study was not able to accurately account for three-dimensional variability along the temperature map. In the end this paper does contribute to an exploration of poylchaete behaviour within the vent systems, a worthy pursuit in the name of understanding the intricacies of their biology.
Chen et al. “The ‘scaly-foot’ gastropod: a new genus amd species of hydrothermal vent-endemic gastropod (Neomphalina: Peltosporidae) from the Indian Ocean. Journal of Molluscan Studies. The Malacological Society of London p. 1-13. 20 April 2015.
Academic familiarity with the scaly-foot gastropod has existed since 2003, when a survey of the Central Indian Ridge revealed a gastropod characterized by pyrite and greigite surfaces along its foot. Despite this, and subsequent identification of other regional gastropods that are within the same species, there has been no formal naming of the organism. This paper acts as a review of previous work investigating this particular species of gastropod, and in the process seeks to solidify its name in future literature officially as Chrysomallon squamiferum. Characterization of the new species involves morphologic and genetic identification, as well as locating geographic distribution. Genetically, as with sequencing the new Osedex sp., focus includes the mitrochondrial cytochrome oxidase 1 gene, in addition to histone 3, 16S rRNA, 18S rRNA, and 28S rRNA genes. The Chrysomallon family is subsequently characterized by the pyrite that covers the surface of their shell and foot, as well as the unique combination of no distinct sex organs or thus malleable limbs along with no clear sexual dimorphism. Specific teeth-like assemblies in curved rows at the ending of its marginal teeth also aids placement within the Peltosporidae family. C. squamiferum is described to live along the Longqi, Kairei, and Solitaire vent fields, although species in this latter field, while genetically the same, notably lack a covering of iron sulphide sclerites, likely due to a lack of iron rich smokers in the area. Cytochrome oxidase I genetic and morphological similarities are used as evidence to support this. Consistent interspecies interaction between these fields is questioned due to the immobile nature of other Peltosporidae larvae that presumably is shared by Chrysomallon. This paper overall characterizes and names this species by connecting many other studies together, and illuminates the many areas of research possible even after current knowledge is assembled.
This paper is a review of C. squamiferum in recent literature, but despite the current level of understanding there are many questions left unanswered. Primarily is the questionable necessity of iron sulphide as a structural component on the gastropod’s surface, since they exist as a population without it in the Solitaire vent field. Extensive detailing of the feeding habits is also missing, as well as the extent of symbiont activity, or specifics on larval dispersal. This paper did do a good job, though, in the way it provided extensive macroscopic and microscopic visuals of the organism in questions, especially of the most identifying characteristics, such as the construction of the marginal teeth.
The Scenic Climax 