As the largest and most poorly environment on Earth, the deep-sea is facing global threats from climate change and anthropogenic disturbance further compounded by the lack of critical baseline data on seafloor species composition and community structure. Many data-deficient regions include those in geographically-isolated offshore environments, like low-latitude seamounts, where sampling and surveys have been limited, resulting in critical knowledge gaps that do not allow for effective conservation measures to be realized. This work seeks to characterize the coral fauna of tropical seamount environments greater than 150 m depth and understand the environmental controls on species distribution and community assembly for long-lived, ecologically-important species, primarily from the Octocorallia, Antipatharia, Stylasteridae, and Scleractinia. Methodologies for accomplishing this research have included analysis of remotely operated vehicle (ROV) video surveys and identification of collected voucher specimens to understand biogeographic patterns within coral communities on seamounts and other rugged seafloor features in 3 different regions: the tropical western Atlantic (Anegada Passage), the equatorial central Pacific (Phoenix Islands), and the tropical eastern Pacific (Costa Rica). These regions represent vastly different oceanographic regimes in terms of biological productivity and water column structure resulting in differential effects on deep-sea coral communities. Evidence from these three regions has shown significant effects of the role that oceanic water masses have on structuring deep-water coral biodiversity and suggests that these features, along with other abiotic environmental variables, are important indicators for understanding species distribution patterns, community structure, and global biogeographic patterns. More broadly, the results of this work have demonstrated the capabilities of exploratory ROV surveys, across multiple platforms, to add practical knowledge to coral species inventories and identify bathyal biogeographic patterns in remote regions of the deep sea. The results of this work, serving as baseline coral biodiversity surveys for each area, are also germane to evaluating the effects of human-mediated disturbance and global climate change in the deep ocean. These disturbances also include ocean acidification, ocean deoxygenation, deep-sea mining, and bottom-contact fishing, all of which have been identified as threats to the seamount benthos. / Biology

Human population growth and global industrial development are driving potentially irreversible anthropogenic impacts on the natural world, including altering global climate and ocean conditions and exposing oceanic environments to a wide range of pollutants. While there are numerous studies highlighting the variable effects of climate change and pollution on marine organisms independently, there are very few studies focusing on the potential interactive effects of these stressors. The deep-sea is under increasing threat from these anthropogenic stressors, especially cold-water coral (CWC) communities which contribute to nutrient and carbon cycling, as well as providing biogenic habitats, feeding grounds, and nurseries for many fishes and invertebrates. The primary goals of this dissertation are to assess the vulnerability of CWCs to independent and interacting anthropogenic stressors in their environment; including natural hydrocarbon seepage, hydrocarbon and dispersant concentrations released during an accidental oil spill (i.e. Deepwater Horizon), and the interacting effects of climate change-related factors and hydrocarbon/dispersant exposure. To address these goals, multiple stressor experiments were implemented to assess the effects of current and future conditions [(a) temp: 8C and pH: 7.9; (b) temp: 8C and pH: 7.6; (c) temp: 12C and pH: 7.9; (d) temp: 12C and pH: 7.6] and oil spill exposure (oil, dispersant, oil + dispersant combined) on coral health using the CWC Lophelia pertusa. Phenotypic response was assessed through observations of diagnostic characteristics that were combined into an average health rating at four points during exposure and recovery. Regardless of environmental condition, average health significantly declined during 24-hour exposure to dispersant alone and increased temperature resulted in a delay in recovery (72 hours) from dispersant exposure. The overall gene expression patterns varied by coral colony, but the dispersant exposure elicited the strongest response. Gene ontology (GO) enrichment analysis revealed that L. pertusa likely experienced varying stages of the cellular stress response (CSR) during exposure to oil, dispersant, and a decrease in pH. The most severe responses were associated with the dispersant exposure including GO terms related to apoptosis, the immune system, wound healing, and stress-related responses. However, the oil exposure induced an upregulation of metabolic pathways and energy transfer but a downregulation of cell growth and development, indicating that the coral nubbins could have been reallocating resources and reducing growth to maintain cellular homeostasis. The decrease in seawater pH elicited a similar response to oil through the enrichment of terms associated with a reduction in the cell cycle and development. Interestingly, the increase in temperature did not elicit a CSR that was detectable in the gene expression data. To further investigate the influence of hydrocarbon exposure on CWCs, comparisons of gene expression profiles were conducted using Callogorgia delta colonies that live in close proximity to active hydrocarbon seepage (“seep”) areas with no current active seepage (“non-seep”) at two different sites in the Gulf of Mexico. There were fewer differentially expressed genes in the “seep” versus “non-seep” comparison (n=21) than the site comparison (n=118) but both analyses revealed GO terms indicating slight alterations in natural biological housekeeping processes, as opposed to a CSR. Our results indicate that distinct stages of the CSR are induced depending on the intensity of stress. This bolsters the idea that there is a stress response shared by all corals in response to a variety of stressors. These data provide evidence that CWCs can be more negatively impacted, both on the phenotypic and molecular levels, by exposure to chemical dispersants than to hydrocarbons alone. Gaining an understanding of how these communities respond, not only to independent stressors, but the combination of these stressors, provides vital information about how CWC communities will fair in current and future conditions. / Biology

The Coastal and Marine Ecological Classification Standard (CMECS) provides a comprehensive framework of common terminology for organizing physical, chemical, biological, and geological information about marine ecosystems. Federally endorsed as a dynamic content standard, all federally funded data must be compliant by 2018; however, applying CMECS to deep sea datasets and underwater video have not been extensively examined. The presented research demonstrates the extent to which CMECS can be applied to deep sea benthic habitats, assesses the feasibility of applying CMECS to remotely operated vehicle (ROV) video data in near-real-time, and establishes best practices for mapping environmental aspects and observed deep sea habitats as viewed by the ROV’s forwardacing camera. All data were collected during 2014 in the Northern Gulf of Mexico by the National Oceanic and Atmospheric Administration’s (NOAA) ROV Deep Discoverer and ship Okeanos Explorer.

The chemical diversity of the phylum Porifera have provided marine natural products (MNPs) such as alkaloids, terpenoids and peptides with ranging biological activity. Every two days a novel compound deriving from sponges are discovered. The aim of this report is to explore the metabolic diversity of deep-sea sponges collected from five different geographical locations. The metabolome of the deep-sea sponges was studied with tandem mass spectrometry (UPLC- MS/MS) and screened for peptides and other major compounds. The aim also includes the selection, isolation and characterisation of a compound obtained from the metabolic profiling of the sponges. The metabolic profiles of 25 sponges were screened. The specimens analysed in this report displayed great metabolic diversity and peptides, halogenated compounds as well as presumable alkaloids were found. The spectra of some specimens displayed low sensitivity which required optimisation such as increase of volume injection. Nevertheless, the report offers novel discoveries for sponges that have never previously been examined. The brominated compound derived from the sponge Desmacella annexa was analysed using large-scale extraction and different analytical techniques such as preparative-HPLC, Q-Tof-MS and NMR. However, the isolation of the target compound was unsuccessful due to co-extractant compounds and insufficient amount of the compound to perform further purification.  Nevertheless, the discoveries made from the metabolic profiles of the sponges may be of assistance when selecting potential bioactive compounds for further studies. Furthermore, bioassays may be performed in the future on the extracts obtained from the sponge Desmacella annexa.

Tesis por compendio / [ES] A lo largo de la historia, el hombre ha explotado los recursos minerales de la tierra para su supervivencia y desarrollo tecnológico sin un equilibrio con su regeneración. Dado el crecimiento de la población mundial y la reducción de recursos, el hombre comenzó a buscar nuevos depósitos que se encontraron en la década de 1960 en las profundidades de los océanos. Con estos, la humanidad empezò a pensar en extraer los minerales de estos depósitos y esto llevò al nacimiento de Deep Sea Mining (DSM). Las consecuencias de las actividades mineras en las profundidades del mar no se conocen realmente y los efectos pueden ser diferentes: contaminación acústica, contaminación lumínica, contaminación química, destrucción del hábitat, fragmentación del hábitat y pérdida de especies que son la base de muchos sistemas vitales. El impacto acústico de estas actividades puede tener importantes consecuencias en las especies marinas, aunque este es el tema más ignorado. El propósito de este proyecto de doctorado fue proporcionar una comprensión básica de los posibles impactos acústicos del DSM en la biodiversidad antes de que comiencen estas actividades. Para hacer esto, el proyecto de doctorado se organizó en varios pasos. Primero, durante un experimento indoor, se analizaron las respuestas bioquímicas en invertebrados sometidos a estrés acústico, Arbacia lixula y Mytilus galloprovincialis. Los resultados demostraron efectos significativos en la actividad de citotoxicidad, expresión de heat shock protein (HSPs) y actividades enzimáticas (esterasas, fosfatasas alcalinas, peroxidasas) en el líquido celomático de los erizos de mar sometidos a estrés acústico. También se observaron efectos significativos en el nivel de glucosa, la citotoxicidad y las actividades enzimáticas (esterasa, fosfatasa alcalina, peroxidasa) de la glándula digestiva del mejillón. En segundo lugar, se analizaron las respuestas bioquímicas de vertebrados e invertebrados sometidos in-situ a la emisión de watergun: Chromis chromis, Holothuria tubulosa y Arbacia lixula. Se encontraron efectos significativos sobre los niveles de cortisol en peces y las actividades enzimáticas (esterasas, fosfatasas alcalinas, peroxidasas y superoxide dismutasas) en membrana peristomial de erizo de mar. Además, las respuestas bioquímicas enzimáticas analizadas en los fluidos celómicos de los equinodermos fue significativa solo por A. lixula y solo en la activade peroxidasica. Tercero se estudiaron los cambios de comportamiento en las condiciones experimentales en juveniles de Sparus aurata sometidos a 4 frecuencias de emisión acústica diferentes. Este experimento demostró que solo las bajas frecuencias tuvieron efectos en todas las respuestas comportamental: altura de natación, motilidad y dispersión del grupo. Sobre la base de los datos de comportamiento obtenidos in vivo en peces jóvenes, se creó un modelo numérico para predecir los impactos de diferentes frecuencias de emisión acústica. Utilizando los resultados obtenidos y la bibliografía científica, se propuso un primer estándar técnico que es útil para la minería. / [CA] A lo llarc de l'historia, l'home ha explotat els recursos minerals de la terra per a la seua supervivencia i desenroll tecnologic sense un equilibri en la seua regeneracio. Donat el creiximent de la poblacio mundial i la reduccio de recursos, l'home escomençà a buscar nous deposits que se trobaren en la decada de 1960 en les fondaries dels oceans. En estos, l'humanitat empezò a pensar en extraure els minerals d'estos deposits i aço llevò al naiximent de Deep Sea Mining (DSM). Les conseqüencies de les activitats mineres en les fondaries del mar no se coneixen realment i els efectes poden ser diferents: contaminacio acustica, contaminacio lluminica, contaminacio quimica, destruccio de l'habitat, fragmentacio de l'habitat i perdua d'especies que son la base de molts sistemes vitals. L'impacte acustic d'estes activitats pot tindre importants conseqüencies en les especies marines, encara que este es el tema mes ignorat. El proposit d'este proyecte de doctorat fon proporcionar una comprensio basica dels possibles impactes acustics del DSM en la biodiversidad abans de que escomencen estes activitats. Per a fer aço, el proyecte de doctorat s'organisà en varis passos. Primer, durant un experiment indoor, s'analisaren les respostes bioquimiques en invertebrats somesos a estrés acustic, Arbacia lixula i Mytilus galloprovincialis. Els resultats demostraren efectes significatius en l'activitat de citotoxicidad, expressio d'heat shock protein (HSPS) i activitats enzimáticas (esterasa, fosfatasas alcalina, peroxidasas) en el liquit celomático dels capellanets de mar somesos a estrés acustic. Tambe s'observaren efectes significatius en el nivell de glucosa, la citotoxicidad i les activitats enzimáticas (esterasa, fosfatasa alcalina, peroxidasas) de la glandula digestiva de la clochina. En segon lloc, s'analisaren les respostes bioquimiques de vertebrats i invertebrats somesos in-situ a l'emissio de watergun: Chromis chromis, Holothuria tubulosa i Arbacia lixula. se trobaren efectes significatius sobre els nivells de cortisol en peixos i les activitats enzimáticas (esterasas, fosfatasas alcalines, peroxidasas y superoxide dimutases) en peristomes de capellanet de mar. Ademes, les respostes bioquimiques enzimáticas analisades en els decorreguts celómicos dels equinoderms fon significativa nomes per A. lixula i nomes en l'activade peroxidasica. Tercer s'estudiaren els canvis de comportament en les condicions experimentals en jovenils de Sparus aurata somesos a 4 freqüencies d'emissio acustica diferents. Este experiment demostrà que nomes les baixes freqüencies tingueren efectes en totes les respostes comportamental: alçada de natacio, motilidad i escampada del grup. Sobre la base de les senyes de comportament obtinguts in vivo en peixos jovens, se creó un model numeric per a predecir els impactes de diferents freqüencies d'emissio acustica. Utilisant els resultats obtinguts i la bibliografia cientifica, se propongue un primer estandart tecnic que es util per a la mineria. / [EN] Throughout history, man has exploited the earth's mineral resources for its survival and for technological development without regard for their regeneration. Given the growth of the world population and given the fall in resources, man started looking for new deposits, which were found in 1960s in the ocean depths. Humankind then began to consider extracting minerals from these deposits and this gave origin to Deep Sea Mining (DSM). The consequences of mining activities in the deep sea are not entirely known and the effects can be varied: noise pollution, light pollution, chemical pollution, habitat destruction, habitat fragmentation and the loss of species which we consider the basis of many life systems. The acoustic impact of these activities could have significant consequences on marine species; nevertheless, this has been the most overlooked issue to date. The aim of this PhD project was to provide baseline knowledge of possible acoustic impacts of DSM on biodiversity before mining begins. In order to do this, the PhD project was organised into 3 different stages. First, during an indoor experiment, the biochemical responses of invertebrates Arbacia lixula and Mytilus galloprovincialis subjected to acoustic stress were analysed. The results showed significant changes in cytotoxicity activity, expression of heat shock proteins (HSPs), and enzyme activities (esterases, alkaline phosphatases, peroxidases) in the coelomic fluid of sea urchins subjected to acoustic stress. Significant effects were also observed in glucose levels, cytotoxicity and enzyme activities (esterase, alkaline phosphatase, peroxidase) in the digestive gland of the mussel. Second, the biochemical responses of vertebrates and invertebrates subjected in-situ to watergun emission were analysed: Chromis chromis, Holothuria tubulosa and Arbacia lixula. Significant effects on fish cortisol levels and on enzyme activities in sea urchin peristomes were found. Furthermore, the enzyme biochemical responses analysed in the coelomic fluids of echinoderms showed significant effects only in A. lixula sea urchin and only in peroxidase activity. Third, behavioural changes in experimental conditions were studied in juveniles of Sparus aurata subjected to 4 different acoustic emission frequencies. This experiment showed that only low frequencies had effects on all the behavioural responses analysed: swimming height, motility and dispersion of the group. Based on behavioural data obtained in vivo on juvenile fish, a numerical model was created to predict the impacts of different acoustic emission frequencies. Using the results obtained and literature, a first technical standard useful for mining activities was drawn up. / The study of the Section 3.3 was supported by grants from MIUR (Ministry of Education, University and Research), Fondo Finalizzato alla Ricerca di Ateneo (FFR, 2018-2021) to M.V. and by the CNR research project: IMPLEMENTATION OF THE SOS CONVENTION - Offshore Platforms & Impacts between MATTM and CNR-DTA, (Capo Granitola, Campobello di Mazara) Work Package E: Indepth technical and scientific evaluation of the effects on marine ecosystems of airgun technologies and the effects of a watergun The study of the Section 3.4 study was conducted in the framework of the PhD program in Mediterranean Biodiversity XXXII cycle (International) of the University of Palermo. I. Perez-Arjona, M. Bou-Cabo and V. Espinosa acknowledge the financial support of the European Comission -project 11.0661/2018794607/SUB/ENV.C2. Risk-based Approaches to Good Environmental Status (RAGES). The other founding supports come from PhD Innovative with Industrial Characterization PON 2014-2020 and the projects CAIMAR Joint Laboratory Italy-Argentina (Laboratori Congiunti Bilaterali Internazionali of the Italian National Reseach Council, 2017-2019) and BOSS – Study of bioacoustics and applications for the sustainable exploitation of marine resources (Projects of major importance in the Scientific and Technological Collaboration Executive Programmes, funded by the Italian Ministry of Foreign Affairs and International Cooperation). / Mauro, M. (2020). Mining extraction in the ocean depths: a baseline to understand and reduce acoustic impact on biodiversity [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/144131 / TESIS / Compendio

Despite over four decades of research on deep-sea hydrothermal vent ecosystems, major gaps remain in our understanding of these systems. Knowledge of microeukaryote diversity, abundance, and involvement in ecosystem function lags far behind that of prokaryotes, and contributions of the non-endosymbiotic microbiome in faunal assemblages to ecosystem processes and overall hydrothermal vent microbial diversity are not known. This research addresses these gaps using high-throughput sequencing of 16S/18S rRNA genes and metagenomes from vent and surrounding non-vent habitats encompassing diffuse hydrothermal fluids, plumes, deep seawater, and microbes in assemblages of the foundation tubeworm species Ridgeia piscesae. Co-occurrence/covariance is a central method used, first, between prokaryotes with known extreme habitat preferences and microeukaryotes to infer potential endemism in the latter, and then between microbes and fauna in R. piscesae assemblages to infer interspecies interactions. Microeukaryote distribution and abundance suggest potential vent endemic microeukarya are infrequently encountered, potentially in low abundance, and belong to novel lineages of Rhizaria and Stramenopila. Potential endemism is inferred for relatives of known apusomonads, excavates, and some clades of Syndiniales. R. piscesae assemblages are shown to be hotspots of microbial taxonomic richness and exhibit a robust temperature-driven distinction in assemblage composition above and below ~25°C spanning micro, meio and macro size classes and microbial domains (Bacteria, Archaea, and micro-Eukarya). Likely interacting faunal and microbial taxa among R. piscesae assemblages are identified as ‘core communities’, which included eight macro- and meiofaunal taxa and members of the Bacteroidetes and Epsilonbacteraeota in highT communities (>25°C) and more meiofaunal species in addition to Alpha- and Gammaproteobacteria, and Actinobacteria in lowT communities (<25°C). Core communities were used to guide metagenomic investigations of microbial functional potential. Exploratory metagenomic analysis required development of new methods to deal with compositional data. ‘Enrichment leanings’ were developed to prioritize in-depth functional comparisons between sample types, which revealed clades within core community microbes with differing functional potential between highT and lowT assemblages and between assemblages and fluids. The balance of autotrophy-heterotrophy genes and patterns of genes for different carbon, nitrogen, and sulfur-cycling processes were tested as potential metrics of community-level function but did not distinguish assemblages by highT/lowT designations. This research brings us closer to understanding hydrothermal vent ecosystem function and suggests sizeable continued discovery potential. / Graduate / 2022-06-08

<p> Wet chemical neutron activation analysis procedures for Au., Pd and Ir together with a non-destructive gamma-counting procedure for Mn are described and applied to the determination of these metals in three Antarctic (E21 -17, E13-3 and E 17-10) and one Caribbean (P63 04-9) deep-sea cores. A total of 49 samples were analyzed. The average values of Au, Pd, Ir in ppb and Mn in Wt.% (together with standard deviations of the mean are: (see table in theses) No large differences exist between Au, Pd and Ir concentrations in different types of deep-sea sediments nor in cores from different areas and their values are within the general concentration range found in most crustal rocks. A general discussion of the sources of precious metals in deep-sea sediments is given. The most important precious metal source in the cores studied in this work is detrital material from land. The contribution of extraterrestrial material to the Au and Pd content of deep-sea sediments is not important but in cores with depositional rates as low as a few tenths of a mm per thousand years, extraterrestrial material may account for more than half of the total Ir content. From the non-detrital Ir content of deep-sea manganese nodules the accretion rate of extraterrestrial material over the. entire surface of the earth is calculated to be about 200 tons per day with an upper limit of 310 tons per day. The constancy of Ir content in deep-sea cores as a function of depth suggests that the influx of extraterrestrial material during the past 3 to 4 million years was probably fairly constant. </p> / Thesis / Master of Science (MSc)

<p> An assemblage of coral skeletons of the species Desmophyllum cristagalli were obtained from the top of Orphan Knoll, 550 km northeast of Newfoundland, from depths of approximately 1600 and 1800 m. The corals were observed for their macro- and micro-boring assemblages, and the boring morphologies documented, using binocular and scanning electron microscopy. Samples of coral were embedded with resin and etched for examination of the micro-boring assemblages.</p> <p> The largest volumetric amount of skeletal material removed was by sponges forming Entobia. This further corroborates the assumption that various species of boring sponges are distributed ubiquitously throughout a wide bathymetric range.</p> <p> Four distinct fungal forms were found, two tubular forms interpreted to be hyphal filaments and two bulbous forms interpreted to be sporangia. These forms were described on the basis of their shape, size, mode of branching, association with other structures and texture. They were then compared to other micro-boring assemblages found in previous studies from various bathymetric ranges. Some forms described in this study were found to be similar to forms described in other studies. Other forms in this study were not found to be documented. It is suggested, therefore, that certain forms, as well as low ichnodiversity, may indicate deeper water environments.</p> <p> Destructive micritization structures were also found in resin casts as well as in thin section. The extent of micritization may indicate the intensity of the parameters at the substrate that affect carbonate dissolution, such as CaCO3 and CO2 concentrations, pH, temperature, and salinity. It would therefore indicate the ambient water conditions at the substrate. If a sufficiently large database could be obtained, as well as distinct separation of the parameters responsible for carbonate dissolution, micritization may be used in a mapping of the carbonate compensation depth through time and depth ranges.</p> / Thesis / Bachelor of Science (BSc)

Light regulates many biological processes through light-sensitive proteins called opsins. Opsins are involved in vision, but they are also expressed in extraretinal tissue, where their roles are far less clear. Fish have large opsin repertoires, derived from a long history of gene duplication and divergence, making them useful models to study opsin diversity and function. I introduce the deep-sea sablefish (Anoplopoma fimbria) as a model for opsin research for three main reasons: i) the availability of a draft genome and transcriptome, simplifying the characterization of this species’ opsin repertoire, ii) the proximity of the only sablefish aquaculture facility in the world, providing exclusive access to a large number of individuals at all developmental stages, iii) the observation that sablefish occupy very different light environments during the course of development, ranging from well-lit shallow waters to the aphotic zone, which provides a light environment context for opsin gene expression data. My survey of the genome showed that sablefish have 36 distinct opsin genes (7 visual and 29 non-visual), even though they spend most of their lives in the dark. The sablefish opsin sequences and repertoire are similar to those of other teleost fish. To test the hypothesis that the sablefish opsin repertoire is being expressed/transcribed during the comparatively brief period of time when this species is exposed to light (the free-swimming larval stage through to the juvenile stage), I quantified the expression of five paralogous genes from a well-studied non-visual opsin family (OPN4’s) in the brain across life stages. Data show statistically stable expression of Opn4m1 and Opn4m3 among life stages, a rough association of Opn4x1 and Opn4m2 expression with age and light environment, and little-to-no expression of Opn4x2. I localized proteins encoded by the most highly expressed class of OPN4 genes in the brain, the Opn4m genes, to the surface of the optic tectum just below a cranial ‘window’; a zone that has been shown to express dozens of opsins in zebrafish (a distant relative, with their ancestor diverging more than 230 million years ago). Thus, in some cases, expression appears to be correlated with light exposure not only temporally, but also spatially. By studying non-visual opsins in sablefish, I have challenged and broadened the current understanding of opsin evolution and function in fish and provided the foundation for future studies to test brain regions for light-sensitivity, perform opsin gene knock-outs, and explore potential light-independent processes. / Graduate / 2023-09-06

Cold-water corals act as critical foundation species in the deep sea by creating extensive three-dimensional habitat structures that support biodiversity hotspots. There is currently a paucity of data concerning the environmental requirements and physiology of cold-water corals, severely limiting our ability to predict how resilient they will be to future environmental change. Cold-water corals are expected to be particularly vulnerable to the effects of ocean acidification, the reduction in seawater pH and associated changes to the carbonate system caused by anthropogenic CO2 emissions. Here, the ecological niche and physiology of the cold-water coral Lophelia pertusa is explored to predict its sensitivity to ocean acidification. Species distribution models were generated in order to quantify L. pertusa’s niche in the Gulf of Mexico with regard to parameters including seafloor topography, the carbonate system, and the availability of hard substrate. A robust oceanographic assessment of the Gulf of Mexico was conducted in order to characterize the current environmental conditions at benthic sites, with a focus on establishing the baseline carbonate system in L. pertusa habitats. Finally, an experimental approach was used to test the physiological response of biogeographically separated L. pertusa populations from the Gulf of Mexico and the Norwegian coast to ocean acidification. Based on my findings, it appears that L. pertusa already persists near the edge of its viable niche space in some locations, and therefore may be highly vulnerable to environmental change. However, experimental results suggest that some populations may be surprisingly resilient to ocean acidification, yielding broad implications for the continued persistence of cold-water corals in future oceans. / Biology