Influence of hydrodynamics on the larval supply to hydrothermal vents on the East Pacific Rise

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 2007Examination of the scales at which larval supply varies spatially and temporally, and correlation with concurrent physical observations can provide insights into larval transport mechanisms that contribute to structuring marine benthic communities. In order to facilitate field studies, this thesis first provides new morphological and genetic identifications for hydrothermal vent gastropod larvae along the northern East Pacific Rise. Daily and weekly variability in the supply of hydrothermal vent gastropod larvae to two hydrothermal vents, 1.6 km apart on the East Pacific Rise, were quantified concurrently with current velocity observations. The magnitude and temporal pattern of larval supply differed between vent sites, despite their close proximity. A strong correlation between along-axis flow and daily larval supply suggested that larval supply occurred primarily via along-axis transport between local sources 1-2 km apart. However, weekly larval supply appeared to be driven by larger spatial scales through losses associated with cross-axis flows and the passage of mesoscale eddies. Tracer movement within a quasi-geostrophic eddy model was consistent with the observations of decreased larval supply concurrent with an eddy observed via satellite altimetry. The tracer movement also indicated that deep eddy-induced flow could facilitate a long-distance dispersal event, enhancing dispersal between vents 100s km apart.Financial support was provided by a National Defense Science and Engineering Graduate Fellowship, the WHOI Academic Programs Office, a WHOI Ocean Venture Fund award, the Ocean Life Institute, the Deep Ocean Exploration Institute, and NSF grants OCE0424953 and NSF OCE9712233 to L.S. Mullineaux

Rebuilding a Vent Community: Lessons from the EPR Integrated Study Site

The discovery of a seafloor eruption at the East Pacific Rise (EPR ) in 1991 presented an opportunity to examine the colonization and assembly of macrofaunal communities at newly formed diffuse-flow vents as well as to document the changes in community composition (Shank et al., 1998) in the context of temperature variation (Scheirer et al., 2006) and fluid chemistry (Von Damm and Lilley, 2004). The eruption site became a focus of the Ridge 2000 EPR Integrated Study Site (ISS) established to facilitate studies of the interaction of biological, geochemical, and/or physical processes associated with seafloor spreading. A second seafloor eruption in 2005–2006 provided opportunities to not only observe changes in community composition and environmental conditions, but also to deploy colonization substrata and other specialized equipment from “time zero.” Here we focus on how larval dispersal and recruitment contribute to the establishment of hydrothermal vent communities

Influence of hydrodynamics on the larval supply to hydrothermal vents on the East Pacific Rise

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Biology, 2007.Includes bibliographical references.Examination of the scales at which larval supply varies spatially and temporally, and correlation with concurrent physical observations can provide insights into larval transport mechanisms that contribute to structuring marine benthic communities. In order to facilitate field studies, this thesis first provides new morphological and genetic identifications for hydrothermal vent gastropod larvae along the northern East Pacific Rise. Daily and weekly variability in the supply of hydrothermal vent gastropod larvae to two hydrothermal vents, 1.6 km apart on the East Pacific Rise, were quantified concurrently with current velocity observations. The magnitude and temporal pattern of larval supply differed between vent sites, despite their close proximity. A strong correlation between along-axis flow and daily larval supply suggested that larval supply occurred primarily via along-axis transport between local sources 1-2 km apart. However, weekly larval supply appeared to be driven by larger spatial scales through losses associated with cross-axis flows and the passage of mesoscale eddies.(cont.) Tracer movement within a quasi-geostrophic eddy model was consistent with the observations of decreased larval supply concurrent with an eddy observed via satellite altimetry. The tracer movement also indicated that deep eddy-induced flow could facilitate a long-distance dispersal event, enhancing dispersal between vents 100s km apart.by Diane K. Adams.Ph.D

Larval Dispersal: Vent Life in the Water Column

Visually striking faunal communities of high abundance and biomass cluster around hydrothermal vents, but these animals don’t spend all of their lives on the seafloor. Instead, they spend a portion of their lives as tiny larvae in the overlying water column. Dispersal of larvae among vent sites is critical for population maintenance, colonization of new vents, and recolonization of disturbed vents. Historically, studying larvae has been challenging, especially in the deep sea. Advances in the last decade in larval culturing technologies and more integrated, interdisciplinary time-series observations are providing new insights into how hydrothermal vent animals use the water column to maintain their populations across ephemeral and disjunct habitats. Larval physiology and development are often constrained by evolutionary history, resulting in larvae using a diverse set of dispersal strategies to interact with the surrounding currents at different depths. These complex biological and oceanographic interactions translate the reproductive output of adults in vent communities into a dynamic supply of settling larvae from sources near and far

Persistent effects of disturbance on larval patterns in the plankton after an eruption on the East Pacific Rise

Author Posting. © The Author(s), 2013. This is the author's version of the work. It is posted here by permission of Inter-Research for personal use, not for redistribution. The definitive version was published in Marine Ecology Progress Series 491 (2013): 67-76, doi:10.3354/meps10463.To predict how benthic communities will respond to disturbance, it is necessary to understand how disturbance affects the planktonic larval supply available to recolonize the area. Deep-sea hydrothermal vent fauna along the East Pacific Rise (EPR) experience frequent local extinctions due to tectonic and magmatic events, but the effects on regional larval abundance and diversity are unknown. We had been monitoring larvae at 9° 50' N on the EPR prior to the 2006 eruption and were able to resume collections shortly afterward. We found that many species that were common before the eruption became significantly less so afterward, whereas a few other species experienced a transient spike in abundance. Surprisingly, overall species richness in the plankton was high 9 mo after the eruption, but then decreased sharply after 1 yr and had not returned to pre-eruption levels after 2 yr. These results suggest that recovery from disturbance may continue to be affected by limited larval supply even several years after a disturbance event. This delay in recovery means that larvae of pioneer species may dominate potential colonists, even after benthic habitats have transitioned to conditions that favor later-successional species. Moreover, the combined effects of natural and anthropogenic disturbance (e.g. mining) would be likely to cause more profound and long-lasting changes than either event alone. Our results indicate that we do not have sufficient data to predict the timing of recovery after disturbance in the deep sea, even in a well-studied vent system.Support was provided by National Science Foundation Grant OCE-0424953 and a Woods Hole Oceanographic Institution grant from the Deep Ocean Exploration Institute

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

Author Posting. © The Authors, 2010. This is the author's version of the work. It is posted here by permission of National Academy of Sciences for personal use, not for redistribution. The definitive version was published in Proceedings of the National Academy of Sciences of the United States of America 107 (2010): 7829-7834, doi:10.1073/pnas.0913187107.The planktonic larval stage is a critical component of life history in marine benthic species because it confers the ability to disperse, potentially connecting remote populations and leading to colonization of new sites. Larval-mediated connectivity is particularly intriguing in deep-sea hydrothermal vent communities, where the habitat is patchy, transient and often separated by tens or hundreds of kilometers. A recent catastrophic eruption at vents near 9°50’N on the East Pacific Rise created a natural clearance experiment and provided an opportunity to study larval supply in the absence of local source populations. Previous field observations have suggested that established vent populations may retain larvae and be largely self-sustaining. If this hypothesis is correct, the removal of local populations should result in a dramatic change in the flux, and possibly species composition, of settling larvae. Fortuitously, monitoring of larval supply and colonization at the site had been established before the eruption and resumed shortly afterward. We detected a striking change in species composition of larvae and colonists after the eruption, most notably the appearance of the gastropod Ctenopelta porifera, an immigrant from possibly >300 km away, and the disappearance of a suite of species that formerly had been prominent. This switch demonstrates that larval supply can change markedly after removal of local source populations, enabling recolonization via immigrants from distant sites with different species composition. Population connectivity at this site appears to be temporally variable, depending not only on stochasticity in larval supply, but also on the presence of resident populations.Support was provided by NSF grants OCE-969105, OCE-9712233, and OCE-0424953), WHOI grants from DOEI and the Ocean Venture Fund, a NDSEG graduate fellowship to DA, and the WHOI Jannasch Chair for Excellence in Oceanography to LM

Evolution of T Cell Responses during Measles Virus Infection and RNA Clearance

Measles is an acute viral disease associated both with immune suppression and development of life-long immunity. Clearance of measles virus (MeV) involves rapid elimination of infectious virus during the rash followed by slow elimination of viral RNA. To characterize cellular immune responses during recovery, we analyzed the appearance, specificity and function of MeV-specific T cells for 6 months after respiratory infection of rhesus macaques with wild type MeV. IFN-γ and IL-17-producing cells specific for the hemagglutinin and nucleocapsid proteins appeared in circulation in multiple waves approximately 2-3, 8 and 18-24 weeks after infection. IFN-γ-secreting cells were most abundant early and IL-17-secreting cells late. Both CD4 and CD8 T cells were sources of IFN-γ and IL-17, and IL-17-producing cells expressed RORγt. Therefore, the cellular immune response evolves during MeV clearance to produce functionally distinct subsets of MeV-specific CD4 and CD8 T cells at different times after infection

Mitosis in circulating tumor cells stratifies highly aggressive breast carcinomas.

BACKGROUND: Enumeration of circulating tumor cells (CTCs) isolated from the peripheral blood of breast cancer patients holds promise as a clinically relevant, minimally invasive diagnostic test. However, CTC utility has been limited as a prognostic indicator of survival by the inability to stratify patients beyond general enumeration. In comparison, histological biopsy examinations remain the standard method for confirming malignancy and grading malignant cells, allowing for cancer identification and then assessing patient cohorts for prognostic and predictive value. Typically, CTC identification relies on immunofluorescent staining assessed as absent/present, which is somewhat subjective and limited in its ability to characterize these cells. In contrast, the physical features used in histological cytology comprise the gold standard method used to identify and preliminarily characterize the cancer cells. Here, we superimpose the methods, cytologically subtyping CTCs labeled with immunohistochemical fluorescence stains to improve their prognostic value in relation to survival. METHODS: In this single-blind prospective pilot study, we tracked 36 patients with late-stage breast cancer over 24 months to compare overall survival between simple CTC enumeration and subtyping mitotic CTCs. A power analysis (1-β = 0. 9, α = 0.05) determined that a pilot size of 30 patients was sufficient to stratify this patient cohort; 36 in total were enrolled. RESULTS: Our results confirmed that CTC number is a prognostic indicator of patient survival, with a hazard ratio 5.2, p = 0.005 (95 % CI 1.6-16.5). However, by simply subtyping the same population based on CTCs in cytological mitosis, the hazard ratio increased dramatically to 11.1, p \u3c 0.001 (95 % CI 3.1-39.7). CONCLUSIONS: Our data suggest that (1) mitotic CTCs are relativity common in aggressive late-stage breast cancer, (2) mitotic CTCs may significantly correlate with shortened overall survival, and (3) larger and more defined patient cohort studies are clearly called for based on this initial pilot study

Divergent Evolutionary Histories of DNA Markers in a Hawaiian Population of the Coral Montipora capitata

We investigated intra- and inter-colony sequence variation in a population of the dom- inant Hawaiian coral Montipora capitata by analyzing marker gene and genomic data. Ribosomal ITS1 regions showed evidence of a reticulate history among the colonies, suggesting incomplete rDNA repeat homogenization. Analysis of the mitochondrial genome identified a major (M. capitata) and a minor (M. flabellata) haplotype in single polyp-derived sperm bundle DNA with some colonies containing 2-3 different mtDNA haplotypes. In contrast, Pax-C and newly identified single-copy nuclear genes showed either no sequence differences or minor variations in SNP frequencies segregating among the colonies. Our data suggest past mitochondrial introgression in M. capitata, whereas nuclear single-copy loci show limited variation, highlighting the divergent evolutionary histories of these coral DNA markers

FBXO7 sensitivity of phenotypic traits elucidated by a hypomorphic allele.

FBXO7 encodes an F box containing protein that interacts with multiple partners to facilitate numerous cellular processes and has a canonical role as part of an SCF E3 ubiquitin ligase complex. Mutation of FBXO7 is responsible for an early onset Parkinsonian pyramidal syndrome and genome-wide association studies have linked variants in FBXO7 to erythroid traits. A putative orthologue in Drosophila, nutcracker, has been shown to regulate the proteasome, and deficiency of nutcracker results in male infertility. Therefore, we reasoned that modulating Fbxo7 levels in a murine model could provide insights into the role of this protein in mammals. We used a targeted gene trap model which retained 4-16% residual gene expression and assessed the sensitivity of phenotypic traits to gene dosage. Fbxo7 hypomorphs showed regenerative anaemia associated with a shorter erythrocyte half-life, and male mice were infertile. Alterations to T cell phenotypes were also observed, which intriguingly were both T cell intrinsic and extrinsic. Hypomorphic mice were also sensitive to infection with Salmonella, succumbing to a normally sublethal challenge. Despite these phenotypes, Fbxo7 hypomorphs were produced at a normal Mendelian ratio with a normal lifespan and no evidence of neurological symptoms. These data suggest that erythrocyte survival, T cell development and spermatogenesis are particularly sensitive to Fbxo7 gene dosage