ALBERT

Description: Submitted in partial fulfillment of the requirements for the degree of Doctor of Science at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution June 1991

Description: The effluent from a collection of diffuse hydrothennal vents was modelled to determine the fate of this source of flow under typical environmental conditions at seafloor spreading centers. A laboratory simulation was conducted to test an analytic model of diffuse plume rise. The results showed that diffuse plumes are likely to remain near the seafloor, with their maximum rise height scaled with the diameter of the source of diffuse flow. The entrainment of ambient seawater into these plumes is limited by the proximity to the seafloor, thus slowing the rate of dilution. The model of diffuse plume behaviour was used to guide the design and implementation of a scheme for monitoring the flow from diffuse hydrothermal vents in the ocean. A deployment of an array at the Southern Juan de Fuca Ridge yielded measurements of a variety of diffuse plume properties, including total heat output. Two distinct sources of hydrothermal flow were detected during the field deployment. The larger source was 1-1 .5km north of the instrument array. and its energy output was 450±270MW. A smaller source was located 100m east of one instrument in the array. The energy output of this source was 12±8MW. The rise heights of the centerlines of these plumes were 45m and 10m, respectively.

Description: Supported by the WHOI Friends of Vents, with a grant from the Mellon Foundation, by the WHOI ScaGrant (NA86-AA-D-SG090, WHOI project number R10-11-PD), and by the National Science Foundation (OCE-8917448).

Description: Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution June 2000

Description: A spectral camera (ALISS - Ambient Light Imaging and Spectral System) was used to image ambient light from high-temperature vents at 9°N East Pacific Rise and the Juan de Fuca Ridge during 1997 and 1998 Alvin dive cruises. ALISS is a low-light digital camera with custom-designed optics. A set of nine lenses, each covered by an individual bandpass filter (50 and 100 nm nominal bandwidths), allows vents to be imaged in nine wavelength bands simultaneously spanning the range of 400-1 000 nm. Thus, both spatial and spectral information are obtained. ALISS was used to image three types of vents: black smokers, flange pools, and beehives. The primary source of light is thermal radiation due to the high temperature of the hydrothermal fluid (-350°C). This light is dominant at wavelengths greater than 700 nm. At flange pools, where the fluid is relatively stable, only thermal radiation is present. Black smokers and beehives, however, are subject to mixing with ambient seawater (2°C) leading to mineral precipitation. Data from these types of vents show the existence of non-thermal, temporally varying light in the 400-700 nm region. This light is probably caused by mechanisms related to mixing and precipitation, such as chemiluminescence, crystalloluminescence and triboluminescence.

Description: Submitted in partial fulfillment of the requirements for the degree of Master of Science at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution May 1990

Description: Estimates of the heat output of hydrothermal vents, identified along the Endeavor and Southern Segments of the Juan de Fuca Ridge, are used to evaluate the total heat flux associated with hydrothermal circulation for the ridge segment. An array carried by D/V ALVIN sampled the temperature and velocity structure of hydrothermal plumes from individual vents . The maximum heat flux calculated for a single vent is 50 MW, but the average vent output is only 13 MW per vent for 31 vents. The estimates for any given vent may vary over an order of magnitude. This uncertainty is due mainly to the difficulty of locating the centerline of the plume relative to the point of measurement, although the uncertainty in determining the constants from the appropriate equations based on laboratory experiments contributes a significant share to the net error. For the Endeavor Segment, the minimum total geothermal heat flux due to hydrothermal circulation exceeds 70 MW. The minimum estimate for the Southern Segment is 16 MW. The maximum estimate is probably closer to the total heat flux (236 MW and 66 MW respectively) . The estimated heat flux density is 3300 W/m2 for the Endeavor vent field and 39 W/m2 for the Southern vent field. Focused hydrothermal venting accounts for only a small fraction of the heat available according to steady-state predictions of conductive heat flux; however, other hydrothermal phenomena (e.g., diffuse flow) account for the greater share of the total hydrothermal heat flux.

Description: This project was supported by NSF grant #OCE87-14511 and by the WHOI Education Office.

Description: Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution May 2000

Description: Eighteen strains of flagellated protists representing 9 species were isolated and cultured from four deep-sea hydrothermal vents in the Eastern Pacific Ocean: Juan de Fuca Ridge, Guaymas Basin, and both 21°N and 9°N on the East Pacific Rise (EPR). The hydrothermal vent flagellates belonged to six different taxonomic orders: the Ancyromonadida, Bicosoecida, Cercomonadida, Choanoflagellida, Chrysomonadida, and Kinetoplastida. Molecular and ultrastructural evidence point to one of the isolates, Ancyromonas, as a plausible candidate for the closest relative to the common ancestor of Metazoans, Fungi, and Choanoflagellates (the Opisthokonta). Using l8S rDNA sequences from most of the major eukaryotic lineages, maximum likelihood, minimum evolution and maximum parsimony analyses yielded congruent phylogenies supporting this hypothesis. Deep-sea vent samples were both cultured to select for kinetoplastid flagellates and analyzed without culturing by denaturing gradient gel electrophoresis (DGGE) using PCR primers specific to the kinetoplastid clade. By comparing these two different methods of analysis, my goal was to decrease the biases and/or errors inherent in either method alone and to improve our ability to assess flagellate diversity and distribution in samples from remote vent environments. PCR and DGGE were used to specifically isolate and amplify target DNA's from all cultured kinetoplastid species in matching vent samples, thus corroborating the findings of culturing. Molecular methods had the additional ability to detect species presence where culturing did not, thereby providing a better indication of the distribution of these species. Many of the vent isolates were ubiquitous members of marine, freshwater, and terrestrial ecosystems worldwide, suggesting a global distribution of these flagellate species. This discovery advanced the hypothesis that ubiquity in distribution patterns among heterotrophic flagellates implies high tolerance and/or adaptability to a wide range of environmental conditions. Experiments under vent conditions of high pressure and high concentrations of metals and sulfide showed that some of these species are very tolerant to extreme environmental conditions.

Description: WHOI Education Office, National Science Foundation, Rhinehart Coastal Research Center, PADI Foundation

Description: Submitted in partial fulfillment of the requirements for the degree of Master of Science at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February 1998

Description: Stable sulfur isotopes (δ34S) and trace Co are analyzed in sulfide and sulfate minerals from six sample types collected from the TAG active mound, 26°N Mid-Atlantic Ridge. δ34S values range from 2.7 to 2O.9%, with sulfate minerals isotopically indistinguishable from seawater (21%), and sulfide minerals reflecting input of 1/3 seawater and 2/3 basaltic sulfur (~0%). Co concentrations in pyrite analyzed by ion microprobe primarily reflect depositional temperatures. The δ34S and Co data are combined to provide information regarding the sources and temperatures of parent fluids, the genetic relationships among sample types, and the circulation of hydrothermal fluids and seawater in the mound. δ34S values and Co concentrations vary by sample type. Chalcopyrite from black smoker samples exhibits invariant δ34S values, indicating direct precipitation from black smoker fluids. Crust samples contain chalcopyrite with a mean δ34S indistinguishable from that of black smoker samples, and pyrite with some light δ34S and moderately high Co values, consistent with crust samples precipitating from cooled black smoker fluids. Massive anhydrite samples are a mixture of anhydrite with high δ34S, and pyrite with variable δ34S and Co values, indicative of deposition from disequilibrium mixing between black smoker fluids and seawater. White smoker samples contain chalcopyrite and sphalerite with high δ34S, and pyrite with low Co values, reflecting deposition from cooler fluids formed from mixtures of seawater and black smoker fluid, with some reduction of sulfate. Mound samples contain chalcopyrite with a mean δ34S indistinguishable from that of black smoker and crust samples, and pyrite with low Co values, suggesting deposition from a fluid isotopically similar to black smoker fluid at temperatures similar to those of white smoker fluid. Massive sulfide samples exhibit pyrite with high δ34S values and very high Co, indicating deposition from and recrystallization with very hot fluids contaminated with seawater-derived sulfate. The data demonstrate that direct precipitation from black smoker fluids, conductive cooling, disequilibrium mixing with entrained seawater, sulfate reduction, and recrystallization all contribute to the formation of the TAG mound deposit. The successful preliminary Co analyses demonstrate that ion microprobe analyses are a viable technique for measuring trace elements in sulfides.

Description: Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution April 8, 1988

Description: Several experiments are presented in this thesis which examine methods to measure and monitor fluid flow from hydrothermal vent fields. Simultaneous velocity, temperature, and conductivity data were collected in the convective flow emanating from a hydrothermal vent field located at 10°S6'N, 103° 41'W on the East Pacific rise. The horizontal profiles obtained indicate that the flow field approaches an ideal plume in the temperature and velocity distribution. Such parameters as total heat flow and maximum plume height can be estimated using either the velocity or the temperature information. The results of these independent calculations are in close agreement, yielding a total heat flow from this vent site of 3.7 ± 0.8 MW and a maximum height of 150±10 m. The nonlinear effects of large temperature variations on heat capacity and volume changes slightly alter the calculations applied to obtain these values. In Guaymas Basin, a twelve day time series of temperature data was collected from a point three centimeters above a diffuse hydrothermal flow area. Using concurrent tidal gauge data from the town of Guaymas it is shown that the effects of tidar currents can be strong enough to dominate the time variability of a temperature signal at a fixed point in hydrothermal flow and are a plausible explanation for the variations seen in the Guaymas Basin temperature data. Theoretical examination of hot, turbulent, buoyant jets exiting from hydrothermal chimneys revealed acoustic source mechanisms capable of producing sound at levels higher than ambient ocean noise. Pressure levels and frequency generated by hydrothermal jets are dependent on chimney dimensions, fluid velocity and temperature and therefore can be used to monitor changes in these parameters over time. A laboratory study of low Mach number jet noise and amplification by flow inhomogeneities confirmed theoretical predictions for homogeneous jet noise power and frequency. The increase in power due to convected flow inhomogeneities, however, was lower in the near field than expected. Indirect evidence of hydrothermal sound fields (Reidesel et al., 1982; Bibee and Jacobson, 1986) showing anomalous high power and low frequency noise associated with vents is due to processes other than jet noise. On Axial Seamount, Juan de Fuca Ridge, high quality acoustic noise measurements were obtained by two hydrophones located 3 m and 40 m from an active hydrothermal vent, in an effort to determine the feasibility of monitoring hydrothermal vent activity through floW noise generation. Most of the noise field could be attributed to ambient ocean noise sources of microseisms, distant shipping and weather, punctuated by local ships and biological sources. Water/rock interface waves of local origin, were detected which showed high pressure amplitudes near the seafloor and, decaying with vertical distance, produced low pressures at 40 m above the bottom. Detection of vent signals was hampered by unexpected spatial non- stationarity due to shadowing effects of the caldera wall. No continuous vent signals were deemed significant based on a criterion of 90% probability of detection and 5% probability of false alarm. However, a small signal near 40 Hz, with a power level of 1x10-4 Pa2/Hz was noticed on two records taken near the Inferno black smoker. The frequency of this signal is consistent with predictions and the power level suggests the occurrence of jet noise amplification due to convected density inhomogeneities. Ambient noise from the TAG (Trans-Atlantic Geotraverse) hydrothermal area on the Mid-Atlantic Ridge near 26°N, in the frequency band 1-30 Hz at a range of 0.75-14 km from the site of an extremely active high temperature hydrothermal vent field (Rona, 1986) was examined. The ambient noise field exhibits great temporal and spatial variations attributed in part to typical ocean noise sources such as distant shipping and microseisms. Power spectral levels as measured at each of six ocean bottom hydrophones (OBH) were used to estimate the location of point sources of sound in the area, if any. The hydrothermal vent did not produce enough sound to be located as a point source using data from the OBH array. The only consistently identifiable point source found with the data set was generating sound in a 0.8-3.5 Hz bandwidth and located outside the median valley. It appears to be harmonic tremor associated with the tip of a ridge on the western side of the spreading axis and may be volcanic in origin.

Description: This work was supported by the WHOI/MIT Education Office, the Center for Analysis of Marine Systems, the National Science Foundation (grant OCE83-l0l75), NOAA National Sea Grant College Program Office, Dept. of Commerce under grant #NA86-AA-D-SG090, WHOI Sea Grant (R/6-l4), the Office of Naval Research grant #N0014-87-K-0007, and the NOAA Vents Program.

Description: Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution May 1998

Description: Planktonic protozoan grazers have the potential to significantly affect the chemistry of particle-associated trace metals. This is due both to the importance of protists as consumers of bacterial-sized particles, and to the unique low-pH, enzyme-rich microenvironment of the grazer food vacuole. This thesis examines the role of protozoan grazers in the marine geochemistry of strongly hydrolyzed, particle-reactive trace metals, in particular Th and Fe. A series of tracer experiments was carried out in model systems in order to determine the effect of grazer-mediated transformations on the chemical speciation and partitioning of radioisotopes C9Fe, 234Th, 51Cr) associated with prey cells. Results indicate that protozoan grazers are equally able to mobilize intracellular and extracellular trace metals. In some cases, protozoan regeneration of trace metals appears to lead to the formation of metal-organic complexes. Protozoan grazing may generate colloidal material that can scavenge trace metals and, via aggregation, lead to an increase in the metal/organic carbon ratio of aggregated particles. Model system experiments were also conducted in order to determine the effect of grazers on mineral phases, specifically colloidal iron oxide (ferrihydrite). Several independent techniques were employed, including size fractionation ors9Fe-labeled colloids, competitive ligand exchange, and iron-limited diatoms as "probes" for bioavailable Fe. Experimental evidence strongly suggests that protozoan grazing can affect the surface chemistry and increase the dissolution rate of iron oxide phases through phagotrophic ingestion. In further work on protozoan-mediated dissolution of colloidal Fe oxides, a novel tracer technique was developed based on the synthesis of colloidal ferrihydrite impregnated with 133Ba as an inert tracer. This technique was shown to be a sensitive, quantitative indicator for the extent of ferrihydrite dissolution/alteration by a variety of mechanisms, including photochemical reduction and ligand-mediated dissolution. In field experiments using this technique, grazing by naturally occuring protistan assemblages was shown to significantly enhance the dissolution rate of colloidal ferrihydrite over that in non-grazing controls. Laboratory and field results indicate that, when integrated temporally over the entire euphotic zone, protozoan grazing may equal or exceed photoreduction as a pathway for the dissolution of iron oxides.

Description: This work was financially supported by a Department of Defense ONR-NDSEG Graduate Fellowship, Office ofNaval Research AASERT Award (N00014-94-1-0711), and the National Science Foundation EGB Program (OCE-9523910).

Description: Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution January 1996

Description: Hydrothermal vents are isolated, short-term habitats that support unique biotic assemblages with relatively high biomass utilizing an unusual energy source. How these communities establish themselves and maintain species identity despite their isolation and impermanence is a significant question in vent ecology. Planktonic larval forms provide a dispersive life stage for many species, but the exact mechanism and controls of dispersal are unknown. A description of larval distribution patterns, for which reliable identification of vent larvae is necessary, is critical to understanding larval dispersal. In gastropod species, the retention of the larval shell on the adult allows identification without the necessity of culturing larvae or using species-specific molecular probes, both techniques that are still difficult with vent organisms. At one site (9°N, East Pacific Rise), eleven species of vent gastropod larvae were identified from the water column up to 200 m off the seafloor. The species-specific level of these identifications is important, as there may be species-level differences in species distributions that influence dispersal. Finding vent larvae high in the water column above the source populations suggests that some mechanism must exist to raise larvae off the sea floor. Literature on related species indicates that larval behaviors such as swimming or buoyancy control could not be responsible for such significant vertical movement over a reasonable time period. Passive movement via entrainment into buoyant plumes rising from smoker vents provides a pathway for larvae to get high above the bottom, and has implications for larval dispersal because vertical shear in flows above vents can cause trajectories in the plume to deviate considerably from those along the seafloor. The distance that vent communities extend around smokers is limited, so 28-97% of the larvae produced may be entrained into the rising plume. Buoyant plumes have the potential to transport a substantial proportion of the larvae produced by hydrothermal vent communities. Larvae may follow several different paths in dispersing between vents. Near-bottom flows tend to be topographically constrained to parallel the ridge crest, and advection in near-bottom currents is one potential larval dispersal mechanism. Entrainment into a buoyant plume and lateral advection hundreds of meters above the sea floor is a feasible alternative or additional dispersal mechanism. However, in deep-sea habitats it is difficult to directly test these hypotheses. Ecological modeling offers an alternative to experimental approaches to hypothesis testing. By creating a realistic model simulation, insight can be gained into which factors: vent spacing and instability (geological); flow regime (physical); or fecundity, larval mortality, and adult maturation time (biological), most strongly influence the patterns of species distributions along mid-ocean ridges. The results of model simulations suggest"that long distance dispersal (as might be provided by plume flow) is vital to long-term persistence of vent populations, and that fecundity and larval mortality interact with habitat spacing and vent lifespan to influence the stability of the overall population. Larval transport, establishment of vent communities and specie$ persistence are key factors in hydrothermal vent ecology. This thesis examines the potential for larval dispersal and species survival under various flow regimes, and identifies and observes the distribution of vent larvae in the water column. Its significance lies in the potential to further understanding of endemic species dispersal in a patchy, ephemeral habitat.

Description: Submitted in partial fulfillment of the requirements for the degree of Master of Science at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 2010

Description: At deep‐sea hydrothermal vents chemolithoautotrophic microbes mediate the transfer of geothermal chemical energy to higher trophic levels. To better understand these underlying processes and the organisms catalyzing them, this research used DNA Stable Isotope Probing (SIP) combined with Catalyzed Activated Reporter Deposition‐Fluorescence in situ Hybridization (CARD‐FISH) to identify the microorganisms chemoautotrophically supporting the food web at a diffuse flow hydrothermal vent. Both anaerobic and aerobic shipboard incubations containing various augmented electron donor and acceptor species showed that Epsilonproteobacteria were the dominant chemoautotrophs with greater than 70% of the cells counted within the first 24 hours. 13C DNA SIP identified unique organisms not previously characterized from low temperature diffuse flow venting: green sulfur bacteria (Chlorobi‐like organisms) possibly utilizing photoautotrophy, aerobic Lutibacter litoralis‐like organisms growing under anaerobic conditions, and Epsilonproteobacterial Thioreductor sp. at temperatures above maximum known tolerances. This research illustrates both the promise and pitfalls of the SIP technique applied to hydrothermal systems, concluding that timing of the incubation experiments is the critical step in eliminating undesired 13C labeling. These results set the stage for a more thorough future examination of diffuse flow microorganisms by presenting interesting questions that second generation experiments could be designed to answer.