mid-Atlantic Ocean Research Articles

Clock drift corrections for large aperture ocean bottom seismometer arrays: application to the UPFLOW array in the mid-Atlantic Ocean

SUMMARY Accurate timing corrections for seismic data recorded by ocean bottom seismometers (OBSs) are essential for a wide range of applications. The synchronization of internal OBS clocks with Global Positioning System (GPS) is typically only possible prior to deployment on the seafloor and upon retrieval. Thus, untracked, clock errors in seismic data may accumulate over the deployment period. The measurement of the clock's offset from GPS at retrieval, referred to as ‘skew’, can be used to correct the data solely under the assumption of a uniform rate of clock drift throughout the whole deployment. However, clock errors can be non-linear. We, therefore, develop a new workflow along with an associated open-source, interactive graphical user interface to estimate clock drift of large aperture OBS arrays. We use the workflow to estimate OBS clock drift curves for 40 OBSs of the large-scale UPFLOW seafloor array in the Madeira–Azores–Canaries region deployed for ∼14 months in 2021–2022. We use the relative shift of daily empirical Green's functions obtained from seismic ambient noise recorded by all available data channels to track clock error. We find that 95 per cent of our OBS clock drift observations have a substantial non-linear component: most maximum deviations to linearity are ∼0.75–1 s (and up to 2 s) occurring mainly halfway through the deployment. We test our drift curves by using them to correct teleseismic earthquake recordings, which enables larger numbers of high-quality P-wave traveltime measurements than when using linear drift corrections. Our drift curves have on average an uncertainty of ∼0.11 s indicating the suitability of the corrected data for future seismological studies such as for seismic tomography, seismicity analysis and moment tensor inversions.

Unraveling sources of cyanate in the marine environment: insights from cyanate distributions and production during the photochemical degradation of dissolved organic matter

Cyanate is a nitrogen and energy source for diverse marine microorganisms, playing important roles in the nitrogen cycle. Despite the extensive research on cyanate utilization, the sources of this nitrogen compound remain largely enigmatic. To unravel the sources of cyanate, distributions and production of cyanate during photochemical degradation of natural dissolved organic matter (DOM) were investigated across various environments, including freshwater, estuarine, coastal areas in Florida, and the continental and slope regions of the North American mid-Atlantic Ocean (NATL). Cyanate production was also examined during the photochemical degradation of exudates from a typical strain of Synechococcus, an important phytoplankton component. To deepen our understanding of the sources and production mechanisms of cyanate, its production was assessed during the photochemical degradation of a natural seawater DOM supplemented with five nitrogen–containing compounds with distinguishing structures and functional groups. Generally, cyanate exhibited higher concentrations in the Florida coastal, estuarine, and freshwater environments than the NATL. However, cyanate distribution did not consistently align with its production rates. Despite significantly low concentrations in the NATL, DOM from this region exhibited cyanate production rates comparable to estuarine and Florida coastal environments. Although relatively high cyanate concentrations were observed in the freshwaters, DOM in this environment exhibited very low cyanate production rates. A highly significant correlation was observed between cyanate and chlorophyll a (Chl a) concentrations in these areas. Moreover, in most estuarine and NATL stations, cyanate concentration and production rate in the Chl a maximum layer were significantly higher than in other layers. Cyanate was produced during the photochemical degradation of the Synechococcus exudates. The cyanate production was significantly enhanced when the natural seawater DOM was supplemented with GlycylGlycine, 4-(methylamino) benzoic acid, 4-[ethyl(methyl)amino] benzaldehyde or methyl 2-aminobenzoate. Our study implies that photochemical degradation of marine DOM, especially phytoplankton-derived DOM, is a substantial source of cyanate in the ocean. Additionally, cyanate may form during the degradation of peptides and small aromatic compounds in DOM, providing novel insights into the nitrogen cycle.

Cetacean and Sea Turtle Observations in the Remote Mid-Atlantic (NW) Ocean

Due to its remoteness, little is known about the occurrence and abundance of cetaceans and sea turtles in the pelagic mid-Atlantic Ocean. Data on cetacean and sea turtle occurrence and distribution were collected by dedicated biological observers to address U.S. monitoring and mitigation requirements associated with a vessel-based academic geophysical survey in international waters in the northwestern and mid-Atlantic Ocean from 14 June through 16 July 2018. A total of 6,949 km (503 h) of visual observations occurred while surveying north from Bermuda and ending in Woods Hole, Massachusetts. A total of 928 cetaceans representing at least 14 species and 15 sea turtles representing three species were observed. The most frequently observed cetacean species was the Atlantic white-sided dolphin (Lagenorhynchus acutus) (340 individuals; 37%) followed by the short-beaked common dolphin (Delphinus delphis) (286 individuals; 31%) and pilot whales (Globicephala spp.) (95 individuals; 10%). These sighting data also included an extralimital sighting of a sperm whale (Physeter macrocephalus) calf at 43.44° N latitude and 36.85° W longitude, and extralimital sightings of Atlantic white-sided dolphins below 38° N latitude. Loggerhead sea turtles (Caretta caretta) were seen most frequently (6 individuals). This study addresses a data gap in documented occurrence and lack of occurrence of cetaceans and sea turtles over a large pelagic area in the northwestern Atlantic Ocean during summer.

Consistent foraging habitat use by a vulnerable breeding seabird highlights potential areas for protection in the mid-Atlantic Ocean

Identifying animal foraging habitat can help prioritise areas for conservation and enable better predictions of how populations respond to environmental change. Recent reductions in the size of biologging devices now enable fine-scale foraging habitat tracking for very small seabirds. We investigated the foraging distribution and habitat preferences of Monteiro’s storm-petrel Hydrobates monteiroi, a tiny (<60 g), vulnerable seabird that is endemic to the Azores Archipelago. We tracked 67 storm-petrels with 108 GPS deployments across 4 consecutive breeding seasons (2018-2021) to identify important foraging areas and preferences for dynamic and static features of their mid-ocean environment. We found that static bathymetric features such as seafloor depth and distance from the nearest seamount were the most important predictors of foraging location, suggesting that topographic features may provide areas of enhanced biological productivity in the mid-Atlantic Ocean that are predictable across long timescales. Although dynamic oceanographic variables (sea surface temperature and chlorophyll a) also helped predict foraging activity, both the location and environmental characteristics of foraging habitat were relatively stable across 4 consecutive years. This suggests that meso-scale oceanographic dynamics do not drive strong interannual variation in foraging behaviour in this system. Currently, only 11.4% of Monteiro’s storm-petrel foraging locations overlap with designated marine protected areas. A total of 95% of unprotected foraging locations fell within the Azores exclusive economic zone (EEZ), indicating a responsibility of the Portuguese government to increase habitat protection. Our findings suggest that more comprehensive at-sea conservation for this vulnerable species could be focused in predictable geographic areas over the mid-Atlantic ridge and seamounts.

Interpretation of the magnetic anomalies over the Mid-Atlantic Ocean Ridge using Swarm-A satellite

The procedures and interpretation of the magnetic data measured over the Mid-Atlantic Ocean Ridge by Swarm-A satellite is discussed in this paper. The data processing procedure has four phases after the data format conversion. The first phase is the selecting data whose Kp index is lower than 1. Secondly, the main magnetic field should be subtracted from the measured data for example through the IGRF model. This step is followed by removing trend, related to the satellite trajectory. The final step is eliminating the dipole nature of the magnetic field via Reduction to the Pole (RTP). Nonetheless, the RTP process might cause misinterpretation over the large study area and lower latitudes. Therefore, the amplitude of the analytic signal (AS) is used as an alternative to the RTP. The qualitative interpretation of the magnetic anomaly is conducted via AS anomaly, bathymetry, heat flow and tectonic map. Quantitatively correlation coefficients of bathymetry and heat flow with respect to AS are interpreted.

First study of the bat fossil record of the mid-Atlantic volcanic islands

ABSTRACTBats are one of the most abundant and important mammals in ecosystems. However, their fossil record is scarce and fragile, making them difficult to find. Accordingly, there is no record of this group in the volcanic islands of the mid-Atlantic Ocean apart from the Canary Islands. This paper studies the first bat fossil record of the Canary Islands (Spain). The material studied is found within two Quaternary lava tubes, Cueva de los Verdes on Lanzarote and Cueva Roja on the island of El Hierro. The dental and humeral morphology and biometry are analysed and compared with current specimens. Among our results we highlight the first fossil data of two species endemic to the islands of the mid-Atlantic Ocean,Plecotus teneriffaeandPipistrellus maderensis, the former from the Canary Islands and the latter from the Azores, Madeira and the Canary Islands. We also confirm the presence ofPipistrellus kuhliiin the fossil record of the island of Lanzarote. No differences are observed between the dental morphology of the current and the fossil populations ofP. maderensisandPl. teneriffae. In the case ofP. kuhlii, the populations of the Canary Islands and the Iberian Peninsula show differences in the paraconule with respect to the populations from central Europe. Palaeoecological studies of these taxa suggest that these islands presented a similar habitat when the sites were formed to the present-day habitat.

A snapshot on composition and distribution of fish larvae across the North Atlantic Ocean

Abstract. Harith MN, O’ Donnell C, Johnston G, Power AM. 2021. A snapshot on composition and distribution of fish larvae across the North Atlantic Ocean. Biodiversitas 22: 4496-4504. This study aims to describe the composition and distribution patterns of fish larvae communities across the North Atlantic Ocean. Several cruises were involved in the effort to collect the fish larvae samples. The sampling took place on the east side of the North Atlantic Ocean, towards the mid-Atlantic Ocean, and on the west side of the North Atlantic Ocean, near the eddies approaching Flemish Cap. A total of 9522 fish larvae were collected and identified from these surveys. These larvae came from 79 taxa and 29 families. Referring to the total abundance, considering all the sampled stations, Atlantic mackerel (Scomber scombrus) was the most abundant species (38.82% of the total fish larvae abundance), followed by blue whiting (Micromesistius poutassou) (15.9%). Referring to the Multi-dimensional scaling (MDS) ordination plots, two major stations clusters separate the on-shelf and off-shelf stations supported by SIMPER analysis. This study provides a snapshot of larval fish concentrations and assembly structure, but current knowledge suggests that the distribution of larval fish assemblages will be highly spatially variable, more research into plume front dynamics and their effects on the region's biota is needed to predict and understand changes.

First Insights into the Diet Composition of Madeiran and Monteiro's Storm Petrels (Hydrobates castro and H. monteiroi) Breeding in the Azores

Although studying the diet of threatened species is crucial in terms of conservation, the diet of the Madeiran Storm Petrel (Hydrobates castro) and the vulnerable, Azores-endemic Monteiro's Storm Petrel (H. monteiroi) is mostly unknown. The only information available to date comes from anecdotal observations, analysis of mercury levels and stable isotopes. Here is presented the first insights into prey consumption by adults and chicks from the two species breeding in the Azores Archipelago, Portugal, in the mid-Atlantic Ocean. The rapidly developing field of metabarcoding was used to identify dietary items from fecal samples, to species level where possible. A total of thirteen fish, five cephalopod, one crustacean and two oligochaete operational taxonomic units (OTUs) were detected. Results suggest that both petrel species feed mainly on myctophid fish. However, differences were detected between the prey species consumed by (i) H. monteiroi and H. castro, (ii) two distinct H. castro populations (Vila and Praia islets), and (iii) chicks and adults within the same population.

Estimating target strength and physical characteristics of gas-bearing mesopelagic fish from wideband in situ echoes using a viscous-elastic scattering model.

Wideband (38 and 50-260 kHz) target strength of organisms were measured in situ using a towed platform in mesopelagic (200-1000 m depth) layers. Organisms with a gas-inclusion are strong scatterers of sound and acoustically distinct from organisms lacking one. In the mesopelagic zone, some of the fish species and physonect siphonophores have a gas-inclusion. Trawl and multinet biological sampling as well as photographic evidence indicate that in the study area (eastern mid-Atlantic Ocean) the majority of the gas-bearing organisms were fish. Subsequently, using a two-layer viscous-elastic spherical gas backscattering model, physical characteristics such as gas-bladder features and body flesh properties were deduced from the measured backscattering signal of individual gas-bearing fish. Acoustic techniques are non-extractive, can be used for the monitoring and quantification of marine organisms in a time- and cost-effective manner, and suit studies of the mesopelagic zone, which is logistically challenging. Vessel-mounted acoustics, widely used for epipelagic studies, has limitations for mesopelagic studies as the deep organisms are inaccessible to high-frequency (≳100 kHz) acoustic pulses transmitted from the surface due to absorption. Therefore, a towed platform equipped with wideband acoustics has several features that can be utilized for monitoring the mesopelagic dense scattering layers containing mixed species.

Nonlinear full waveform inversion of wide-aperture OBS data for Moho structure using a trans-dimensional Bayesian method

SUMMARY Seismic full waveform inversion (FWI) is a powerful method for estimating quantitative subsurface physical parameters from seismic data. As the FWI is a nonlinear problem, the linearized approach updates model iteratively from an initial model, which can get trapped in local minima. In the presence of a high-velocity contrast, such as at Moho, the reflection coefficient and recorded waveforms from wide-aperture seismic acquisition are extremely nonlinear around critical angles. The problem at the Moho is further complicated by the interference of lower crustal (Pg) and upper mantle (Pn) turning ray arrivals with the critically reflected Moho arrivals (PmP). In order to determine velocity structure near Moho, a nonlinear method should be used. We propose to solve this strong nonlinear FWI problem at Moho using a trans-dimensional Markov chain Monte Carlo (MCMC) method, where the earth model between lower crust and upper mantle is ideally parametrized with a 1-D assumption using a variable number of velocity interfaces. Different from common MCMC methods that require determining the number of unknown as a fixed prior before inversion, trans-dimensional MCMC allows the flexibility for an automatic estimation of both the model complexity (e.g. the number of velocity interfaces) and the velocity–depth structure from the data. We first test the algorithm on synthetic data using four representative Moho models and then apply to an ocean bottom seismometer (OBS) data from the Mid-Atlantic Ocean. A 2-D finite-difference solution of an acoustic wave equation is used for data simulation at each iteration of MCMC search, for taking into account the lateral heterogeneities in the upper crust, which is constrained from traveltime tomography and is kept unchanged during inversion; the 1-D model parametrization near Moho enables an efficient search of the trans-dimensional model space. Inversion results indicate that, with very little prior and the wide-aperture seismograms, the trans-dimensional FWI method is able to infer the posterior distribution of both the number of velocity interfaces and the velocity–depth model for a strong nonlinear problem, making the inversion a complete data-driven process. The distribution of interface matches the velocity discontinuities. We find that the Moho in the study area is a transition zone of 0.7 km, or a sharp boundary with velocities from around 7 km s−1 in the lower crust to 8 km s−1 of the upper mantle; both provide nearly identical waveform match for the field data. The ambiguity comes from the resolution limit of the band-limited seismic data and limited offset range for PmP arrivals.

SEAFLOOR MAPPING OF THE ATLANTIC OCEAN BY GMT: VISUALIZING MID ATLANTIC RIDGE SPREADING, SEDIMENT DISTRIBUTION AND TECTONIC DEVELOPMENT

The study presents the insights of the tectonic development and geological settings of the Atlantic Ocean supported by cartographic visualization in Generic Mapping Tools (GMT). The aim is to study geologic situation and trends in the tectonic development of the Mid-Atlantic Ridge and Atlantic Ocean seafloor. The objective is to find out impact of various factors (such as volcanic, tectonic, hydrothermal and sedimentary processes) that sculpt seafloor geomorphology, and correlation between early history of crust formation, geological processes and present submarine landforms. Other assignments in this work refer to mutual comparison of raster grids on sedimentation, topography, geology, seafloor fabric and highlighting similarities among the landforms and sediment thickness. Asymmetry in crustal accretion is explained by the tectonic history of the lithosphere formation. Correlation between plate subduction and development of the submarine landforms is explained by the Earth's crust extension resulting in formation of cracks, elongations, faults, rifts. Ocean seafloor geomorphology is shaped by a variety of factors that impact its form at different scales. These drivers (tectonic evolution, oceanic currents, hydrology, sedimentation) have effects on geomorphic landforms of the seafloor in context of historic geological development and during Quaternary. Technical part of this work was performed by GMT scripting toolset with all maps plotted in American polyconic projection. The results are received by overlay, cartographic analysis and synthesis of the multi-source geodata through mapping and interpreting grids (ETOPO1, EGM96, GlobSed, crustal age). This work contributes to expand the knowledge on geological and tectonic development of the Atlantic Ocean seabed in order to complete the view of its submarine geomorphology

The Bristol Sponge Microbiome Collection: A Unique Repository of Deep-Sea Microorganisms and Associated Natural Products.

The deep ocean is the largest habitat for life on Earth, though the microorganisms that occupy this unique environmental niche remain largely unexplored. Due to the significant logistical and operational challenges associated with accessing the deep ocean, bioprospecting programmes that seek to generate novel products from marine organisms have, to date, focused predominantly on samples recovered from shallow seas. For this reason, the deep ocean remains a largely untapped resource of novel microbiological life and associated natural products. Here we report the establishment of the Bristol Sponge Microbiome Collection (BISECT), a unique repository of deep-sea microorganisms and associated metabolites isolated from the microbiota of marine sponges, recovered from previously unsurveyed regions of the mid Atlantic Ocean, at depths of 0.3–3 km. An integrated biodiscovery pipeline comprising molecular, genetic, bioinformatic and analytical tools is also described, which is being applied to interrogate this collection. The potential of this approach is illustrated using data reporting our initial efforts to identify antimicrobial natural product lead compounds. Prospects for the use of BISECT to address allied pharmaceutical needs, along with mechanisms of access to the collection are also discussed

Mystery over the Atlantic: the tragic fate of Air France Flight 447

Theoretical basis This case has two primary purposes. First, it allows students to examine how cognitive bias can affect decision making in stressful situations. Students explore why individuals make flawed choices. They learn about how managers shape the context and the process through which teams make decisions. For instance, automation can create a climate in which people then struggle to cope with the unexpected when it happens. Students examine why individuals make these systematic errors in judgment. The case demonstrates that leaders need to be aware of the traps that individuals and teams encounter when they make decisions in crisis situations, and it enables students to discuss the strategies that leaders can employ to avoid these traps. Second, the case provides an opportunity to examine a catastrophic failure in detail. Students discover that it can be nearly impossible to identify a single factor that caused the failure. Instead, they learn how to apply multiple theoretical perspectives to examine a serious organizational breakdown. They become familiar with important concepts from behavioral decision theory, such as complex systems theory and how it interacts with cognitive bias. Research methodology The technical report released by the French Aviation Authority along with the primary flight cockpit voice recorder data were used as the basis for this case. Other available public data such as news reports were used to round out the case study. Case overview/synopsis On June 9, 2009, on a routine flight from Rio de Janeiro to Paris, Air France 447 (AF 447), carrying 220 people crashed in the mid-Atlantic Ocean. Drawing from various first-hand accounts (cockpit voice recorder) and secondary evidence of the tragedy, the case provides a detailed account of the key events that took place leading up to the accident. The case describes how the pilots on AF447 were confronted with a scenario they had not faced before, and through the confusion made a series of errors. Through many of the quotes in the text, readers gain an understanding of the impressions and perceptions of the pilots, including how they felt about many of the critical decisions and incidents during the last minutes of the flight. The case concludes by highlighting the main findings of the BEA report. Complexity academic level This case study is appropriate for undergraduate students studying organizational behavior. It is also appropriate for MBA-level leadership and behavior classes.

Ionospheric wave signature of the American solar eclipse on 21 August 2017 in Europe

A total solar eclipse occurred on 21 August 2017, with the path of totality starting over the North Pacific Ocean, crossing North-America and ending over the Mid-Atlantic Ocean slightly North of the equator. As a result, a partial solar eclipse was observed as far away as the Western Europe. The ionospheric observatory in Dourbes, Belgium, was right on the edge of the partial eclipse and was exposed for a very short period of only few minutes just before the local sunset. High-resolution ionospheric measurements were carried out at the observatory with collocated digital ionosonde and GNSS receivers. The data analysis revealed a clear wave-like pattern in the ionosphere that can be seen arriving before the local onset of the eclipse. The paper details the analysis and provides a possible explanation of the observed phenomenon.

Seabirds fighting for land: phenotypic consequences of breeding area constraints at a small remote archipelago

Identifying associations between phenotypes and environmental parameters is crucial for understanding how natural selection acts at the individual level. In this context, genetically isolated populations can be useful models for identifying the forces selecting fitness-related traits. Here, we use a comprehensive dataset on a genetically and ecologically isolated population of the strictly marine bird, the brown booby Sula leucogaster, at the tropical and remote Saint Peter and Saint Paul Archipelago, mid-Atlantic Ocean, in order to detect phenotypic adjustments from interindividual differences in diet, foraging behaviour, and nest quality. For this, we took biometrics of all individuals of the colony breeding in 2014 and 2015 and tested their associations with nest quality, diet parameters, and foraging behaviour. While body size was not related to the foraging parameters, the body size of the females (responsible for nest acquisition and defence) was significantly associated with the nest quality, as larger females occupied high-quality nests. Our findings suggest that the small breeding area, rather than prey availability, is a limiting factor, emphasizing the role of on-land features in shaping phenotypic characteristics and fitness in land-dependent marine vertebrates.

Extreme Wave Height Events in NW Spain: A Combined Multi-Sensor and Model Approach

The Galician coast (NW Spain) is a region that is strongly influenced by the presence of low pressure systems in the mid-Atlantic Ocean and the periodic passage of storms that give rise to severe sea states. Since its wave climate is one of the most energetic in Europe, the objectives of this paper were twofold. The first objective was to characterize the most extreme wave height events in Galicia over the wintertime of a two-year period (2015–2016) by using reliable high-frequency radar wave parameters in concert with predictions from a regional wave (WAV) forecasting system running operationally in the Iberia-Biscay-Ireland (IBI) area, denominatedIBI-WAV. The second objective was to showcase the application of satellite wave altimetry (in particular, remote-sensed three-hourly wave height estimations) for the daily skill assessment of the IBI-WAV model product. Special attention was focused on monitoring Ophelia—one of the major hurricanes on record in the easternmost Atlantic—during its 3-day track over Ireland and the UK (15–17 October 2017). Overall, the results reveal the significant accuracy of IBI-WAV forecasts and prove that a combined observational and modeling approach can provide a comprehensive characterization of severe wave conditions in coastal areas and shows the benefits from the complementary nature of both systems.

Habitat risk assessment for regional ocean planning in the U.S. Northeast and Mid-Atlantic.

Coastal habitats provide important benefits to people, including habitat for species targeted by fisheries and opportunities for tourism and recreation. Yet, such human activities also can imperil these habitats and undermine the ecosystem services they provide to people. Cumulative risk assessment provides an analytical framework for synthesizing the influence of multiple stressors across habitats and decision-support for balancing human uses and ecosystem health. To explore cumulative risk to habitats in the U.S. Northeast and Mid-Atlantic Ocean Planning regions, we apply the open-source InVEST Habitat Risk Assessment model to 13 habitats and 31 stressors in an exposure-consequence framework. In doing so, we advance the science priorities of EBM and both regional planning bodies by synthesizing the wealth of available data to improve our understanding of human uses and how they affect marine resources. We find that risk to ecosystems is greatest first, along the coast, where a large number of stressors occur in close proximity and secondly, along the continental shelf, where fewer, higher consequence activities occur. Habitats at greatest risk include soft and hard-bottom nearshore areas, tidal flats, soft-bottom shelf habitat, and rocky intertidal zones—with the degree of risk varying spatially. Across all habitats, our results indicate that rising sea surface temperatures, commercial fishing, and shipping consistently and disproportionally contribute to risk. Further, our findings suggest that management in the nearshore will require simultaneously addressing the temporal and spatial overlap as well as intensity of multiple human activities and that management in the offshore requires more targeted efforts to reduce exposure from specific threats. We offer a transparent, generalizable approach to evaluating cumulative risk to multiple habitats and illustrate the spatially heterogeneous nature of impacts along the eastern Atlantic coast and the importance of spatial scale in estimating such impacts. These results offer a valuable decision-support tool by helping to constrain the decision space, focus attention on habitats and locations at the greatest risk, and highlight effect management strategies.

A denitrifying community associated with a major, marine nitrogen fixer.

The diazotrophic cyanobacterium, Trichodesmium, is an integral component of the marine nitrogen cycle and contributes significant amounts of new nitrogen to oligotrophic, tropical/subtropical ocean surface waters. Trichodesmium forms macroscopic, fusiform (tufts), spherical (puffs) and raft-like colonies that provide a pseudobenthic habitat for a host of other organisms including marine invertebrates, microeukaryotes and numerous other microbes. The diversity and activity of denitrifying bacteria found in association with the colonies was interrogated using a series of molecular-based methodologies targeting the gene encoding the terminal step in the denitrification pathway, nitrous oxide reductase (nosZ). Trichodesmium spp. sampled from geographically isolated ocean provinces (the Atlantic Ocean, the Red Sea and the Indian Ocean) were shown to harbor highly similar, taxonomically related communities of denitrifiers whose members are affiliated with the Roseobacter clade within the Rhodobacteraceae (Alphaproteobacteria). These organisms were actively expressing nosZ in samples taken from the mid-Atlantic Ocean and Red Sea implying that Trichodesmium colonies are potential sites of nitrous oxide consumption and perhaps earlier steps in the denitrification pathway also. It is proposed that coupled nitrification of newly fixed N is the most likely source of nitrogen oxides supporting nitrous oxide cycling within Trichodesmium colonies.

The Role of Mid-Atlantic Ocean Data Portal in Supporting Ocean Planning

The Mid-Atlantic Regional Council on the Ocean (MARCO) was established in 2009 to enhance the vitality of the region's ocean ecosystem and economy. One of MARCO’s first action items was the development of the Mid-Atlantic Ocean Data Portal to serve as an on-line platform to engage stakeholders across the region with the objective of improving their understanding of how ocean resources and places are being used, managed, and conserved. A key component is the Marine Planner, an interactive map-based visualization and decision support tool. These types of on-line tools are becoming increasingly popular means of putting essential data and state-of-the-art visualization technology into the hands of the agencies, industry, community leaders, and stakeholders engaged in ocean planning. However to be effective, the underlying geospatial data has to be seen as objective, comprehensive, up-to-date and regionally consistent. To meet this challenge, the portal utilizes a distributed network of web map services from credible and authoritative sources. Website analytics and feedback received during the review and comment period of the 2016 release of the Mid-Atlantic Ocean Action Plan confirm that the Data Portal is viewed as integral to this ocean planning process by the MidAtlantic Regional Planning Body and key stakeholders. While not all stakeholders may agree with specific planning decisions, there is broad based agreement on the need for better data and making access to that data widely available.

The multimethod palaeointensity approach applied to volcanics from Terceira: full-vector geomagnetic data for the past 50 kyr

The island of Terceira (38.5°N, 27.2°W) in the Azores Archipelago boasts a wealth of well-dated recent volcanic products; it is therefore the ideal location to improve the resolution of the full-vector geomagnetic field record for the Mid-Atlantic Ocean. We investigated 21 (sub-)sites sampled from 10 different cooling units; six of these cooling units are from the Holocene, the other four are approximately coeval with the age of known geomagnetic excursions. After successfully determining the palaeodirections from all but one site, we applied the multimethod palaeointensity approach to all sites. Here, we used three different palaeointensity methods: the IZZI-Thellier protocol, the Multispecimen technique, and the calibrated pseudo-Thellier method. For the Holocene sites four robust palaeointensity estimates were obtained, they mostly agree with data from the nearby island of Sao Miguel and data from the Iberian Peninsula and West Africa. Two older sites, dated at 25.7 and 46.3 ka, produced low palaeointensities: 24.4 and 24.1 μT, respectively. As both the IZZI-Thellier and pseudo-Thellier methods yielded technically acceptable results for these sites we used them to improve the pseudo-Thellier calibration relation and establish its applicability to lower palaeointensities. Sixty per cent of all sampled cooling units/ages in our study yielded a technically successful palaeointensity estimate; this unusually high success rate is attributed both to our sampling strategy and the implementation of the multimethod approach.