Cape Verde Archipelago Research Articles

Crustal and uppermost mantle structure of Cape Verde from ambient noise tomography

SUMMARY We present a seismic ambient noise tomography of the Cape Verde archipelago, located in the Atlantic Ocean, approximately 600 km west of Senegal. We used 38 seismic broad-band stations that continuously recorded for 10 months, in order to construct the first 3-D model of Sv-wave velocities for the crust and uppermost mantle beneath the Cape Verde region. We started by computing phase cross-correlations for vertical component recordings using all possible inter-island station pairs. Next, a time–frequency phase-weighted stack was applied to obtain robust Rayleigh-wave group-velocity dispersion curves in the period band between 10 and 24 s. Group-velocity maps at different periods are obtained by inverting the dispersion curves. We then inverted the group-velocity maps to obtain the 3-D shear wave velocity structure of the crust and uppermost mantle beneath Cape Verde. The final 3-D model extends from 8 km down to 23 km and has a lateral resolution of about 50 km. The crust in the southwestern sector, encompassing Fogo, presents lower S-wave velocities that may be caused by the presence of melt pockets and/or hydrothermal fluids circulation. The uppermost mantle beneath the northwestern sector is characterized by higher S-wave velocities in agreement with previous results obtained from Ps and Sp receiver functions. Those high-velocity anomalies can reflect non-altered crust or remnants of magma chambers or solidified basaltic intrusions, which fed the volcanism in these islands. Our maps revealed the presence of crustal underplating across the entire archipelago, yet stronger beneath the groups Santo Antão—São Vicente—São Nicolau and Fogo—Santiago—Maio.

A 3D Innovative Approach Supporting the Description of Boring Sponges of the Precious Red Coral Corallium rubrum

The carbonatic scleraxis of Corallium rubrum (L.), commonly known as red coral, is often found infested by excavating sponges. These boring organisms produce galleries inside the compact axis of the coral in a variety of shapes compromising the integrity of the skeleton and reducing its commercial value. Three sponge species, already known to bore into Corallium rubrum, have been identified in colonies collected from Cape Verde Archipelago—Alectona millari (Carter, 1879); Dotona pulchella mediterranea (Rosell and Uriz, 2002); and Thoosa armata (Topsent, 1888)—together with a new species belonging to the genus Alectona and here described. SEM analysis provided evidence of the microerosion patterns of these species, confirming the presence of radial scars overlapped with the concentric ones, in T. armata. For the first time, microcomputed tomography was employed to obtain three-dimensional reconstructions of sponge excavations inside the red coral scleraxis and to estimate the eroded volume.

Some phenotypic variation in Leptotes pirithous on the Cape Verde Islands, in a wider geographical context (Lepidoptera: Lycaenidae)

Unusual phenotypes of Leptotes pirithous (Linnaeus, 1767) were encountered on islands of the Cape Verde Archipelago in 2013 and 2017. Dark/pale and tailed/tailless forms of this polyommatine lycaenid species are illustrated and discussed. The name capverti Libert, Baliteau & Baliteau, 2011, is considered and the phenotype compared with dark forms elsewhere. It is concluded that many individuals are indistinguishable from the Indian Ocean f. insulana Aurivillius, 1909, and from other dark forms that occur in many localities. L. pirithous host-plants on eight different islands, and observations regarding phenotypes, are tabulated. The three specimens of Aurivillius’ insulana and the holotype and both paratypes of capverti are illustrated for the first time, together with a sample of specimens of L. pirithous from the African mainland, the Cape Verde Islands and other islands in the Atlantic and Indian Oceans.

Shearwaters' nest attendance patterns throughout the lunar cycle: Are oceanographic conditions decisive for timing of nest arrival?

The moon cycle has long been recognized as a driving factor of animals' behavioural patterns. However, its influence on seabirds' nocturnal behaviour remains poorly understood. Using a long-term GPS tracking dataset from Cory's and Cape Verde shearwaters (Calonectris borealis and Calonectris edwardsii, respectively) in the Berlengas, Azores, Madeira and Cape Verde archipelagos, North Atlantic Ocean, we investigated nest attendance patterns of breeding birds in relation to oceanographic and natural light conditions during mid-chick rearing. We intended to understand if inter-annual changes in oceanographic conditions around each colony were related with timing of nest arrival and respective light intensity at burrow entrance. For this, oceanographic conditions were evaluated using proxies for marine productivity and metrics of shearwaters' foraging effort. We also wanted to investigate if birds adjusted nest attendance in relation to moonlight throughout the lunar cycle, and whether these patterns changed with contrasting oceanographic conditions. Shearwaters stayed longer at sea after sunset in years of good oceanographic conditions, returning ashore earlier in years of poor conditions, mostly under twilight. Breeding birds also seemed little influenced by moonlight at colonies, although this did not seem to be the case at sea. In particular, they adjusted nest arrivals with the onset of waning moon nights (nights starting without moon), but delayed nest entrances throughout waxing moon nights (nights entailing a growing period of moonlight until moonset). However, this pattern was not extensible to years of poor foraging conditions, when birds returned ashore regardless of moonlight conditions. Combined, these results show that the nest attendance behaviour is mediated by moonlight in Cory's and Cape Verde shearwaters, a pattern that seems to be regulated by prevailing oceanographic and foraging conditions.

Distribution and biomass of gelatinous zooplankton in relation to an oxygen minimum zone and a shallow seamount in the Eastern Tropical North Atlantic Ocean

Physical and topographic characteristics can structure pelagic habitats and affect the plankton community composition. For example, oxygen minimum zones (OMZs) are expected to lead to a habitat compression for species with a high oxygen demand, while upwelling of nutrient-rich deep water at seamounts can locally increase productivity, especially in oligotrophic oceanic waters. Here we investigate the response of the gelatinous zooplankton (GZ) assemblage and biomass to differing oxygen conditions and to a seamount in the Eastern Tropical North Atlantic (ETNA) around the Cape Verde archipelago. A total of 16 GZ taxa (>1100 specimens) were found in the upper 1000 m with distinct species-specific differences, such as the absence of deep-living species Atolla wyvillei and Periphylla periphylla above the shallow seamount summit. Statistical analyses considering the most prominent groups, present at all stations, namely Beroe spp., hydromedusae (including Zygocanna vagans, Halicreas minimum, Colobonema sericeum, Solmissus spp.) and total GZ, showed a strong positive correlation of abundance with temperature for all groups, whereas oxygen had a weak negative correlation only with abundances of Beroe spp. and hydromedusae. To account for size differences between species, we established length-weight regressions and investigated total GZ biomass changes in relation to physical (OMZ) and topographic characteristics. The highest GZ biomass was observed at depths of lowest oxygen concentrations and deepest depth strata at the southeastern flank of the seamount and at two stations south of the Cape Verde archipelago. Our data suggest that, irrespective of their patchy distribution, GZ organisms are ubiquitous food web members of the ETNA, and their habitat includes waters of low oxygen content.

Dust and tropical PMx aerosols in Cape Verde: Sources, vertical distributions and stratified transport from North Africa

We investigated the sources and processes affecting the vertical distribution of tropical PMx aerosols (particulate matter -PM- smaller than 10, 2.5 and 1 μm, PM10, PM2.5 and PM1, respectively) in the low troposphere of Santo Antão and São Vicente islands, in Cape Verde archipelago, a region where a better understanding of aerosols is needed due to their involvement in tropical meteorology and their impact on air quality, ocean and climate. We found that local sources had a low-scale impact. From transect measurements at ground level, we found that PMx levels were predominantly low, except near to PMx sources, where distinctive PM1 / PM2.5 ratios were measured, linked to vehicle exhaust (0.96), biomass burning (0.67) and Cape Verdean dust (0.36) emissions. The depth of the marine boundary layer (MBL) and the vertical distributions of PMx showed wide variability prompted by meteorological conditions. The trade winds prevailed in the MBL, whereas other airflows were situated above it: North-Atlantic, African easterly airflow and Saharan Air Layer. Under North-Atlantic airflow conditions, the MBL extended to 1400 m above sea level (m.a.s.l.). Above this altitude, PMx concentrations decreased quickly (< 3 μg/m3) due to the free troposphere conditions. Under Saharan dust conditions, the MBL was confined to just 70 m.a.s.l., whereas a complex dust stratification was observed above, characterized by alternating dry air layers with high dust loads (PM10 ~ 100 μg/m3) and more humid air layers with lower aerosol loads (PM10 ~ 40 μg/m3). Within the dry easterly African airflow occurring above the marine stratocumulus typical of the MBL top (placed at 500 m.a.s.l.), we detected layers enriched in hydrophilic aerosols (PM10: ~ 8 μg/m3). These were imbedded in relatively humid air (RH ~48%), probably linked to secondary aerosol formation by in-cloud processes in the marine stratocumulus situated below. We found that PMx transport from North Africa, both under dust and dust-free conditions, is associated with complex vertical stratifications, even within the dusty Saharan Air Layer.

A revised multilocus phylogeny of Old World sparrows (Aves: Passeridae)

Abstract The Old World sparrows include some of the best-studied passerine species, such as the cosmopolitan human commensal, the house sparrow (Passer domesticus) as well as poorly studied narrow-range endemics like the Iago sparrow (P. iagoensis) from the Cape Verde Archipelago or specialists from extreme environments like the desert sparrow (P. simplex). It is therefore notable that to date the most complete phylogenetic hypothesis for the Old World sparrows comprised only ten of 43 currently accepted species. With this study we provide an updated phylogeny of Passeridae covering about two third of the family’s species richness. Though still being far from taxon-complete, this new phylogenetic hypothesis provides firm evidence to clarify some open taxonomic questions. All genus-level taxa were reciprocally monophyletic with strong support. Contrary to previous classifications, bush sparrows and rock sparrows were not sister taxa, and therefore their classification in separate genera Gymnoris and Petronia is justified. Plumage color traits like the yellow throat patch of the latter two genera or head color pattern in Passer species do not provide reliable phylogenetic information, except for the large-sized African grey-headed sparrows that resulted as a monophyletic group (P. diffusus, P. griseus, P. gongoensis). Unexpectedly, two small-sized species, P. eminibey and P. luteus that to date are regarded as close relatives were firmly nested in two separate clades of Passer sparrows. Therefore, their separate generic treatment under Sorella eminibey and Auripasser luteus (together with A. euchlorus) does not seem justified.

Optimal use of the Prede POM sky radiometer for aerosol, water vapor, and ozone retrievals

Abstract. The Prede POM sky radiometer is a filter radiometer deployed worldwide in the SKYNET international network. A new method, called Skyrad pack MRI version 2 (MRI v2), is presented here to retrieve aerosol properties (size distribution, real and imaginary parts of the refractive index, single-scattering albedo, asymmetry factor, lidar ratio, and linear depolarization ratio), water vapor, and ozone column concentrations from the sky radiometer measurements. MRI v2 overcomes two limitations of previous methods (Skyrad pack versions 4.2 and 5, MRI version 1). One is the use of all the wavelengths of 315, 340, 380, 400, 500, 675, 870, 940, 1020, 1627, and 2200 nm if available from the sky radiometers, for example, in POM-02 models. The previous methods cannot use the wavelengths of 315, 940, 1627, and 2200 nm. This enables us to provide improved estimates of the aerosol optical properties, covering almost all the wavelengths of solar radiation. The other is the use of measurements in the principal plane geometry in addition to the solar almucantar plane geometry that is used in the previous versions. Measurements in the principal plane are regularly performed; however, they are currently not exploited despite being useful in the case of small solar zenith angles when the scattering angle distribution for almucantars becomes too small to yield useful information. Moreover, in the inversion algorithm, MRI v2 optimizes the smoothness constraints of the spectral dependencies of the refractive index and size distribution, and it changes the contribution of the diffuse radiances to the cost function according to the aerosol optical depth. This overcomes issues with the estimation of the size distribution and single-scattering albedo in the Skyrad pack version 4.2. The scattering model used here allows for non-spherical particles, improving results for mineral dust and permitting evaluation of the depolarization ratio. An assessment of the retrieval uncertainties using synthetic measurements shows that the best performance is obtained when the aerosol optical depth is larger than 0.2 at 500 nm. Improvements over the Skyrad pack versions 4.2 and 5 are obtained for the retrieved size distribution, imaginary part of the refractive index, single-scattering albedo, and lidar ratio at Tsukuba, Japan, while yielding comparable retrievals of the aerosol optical depth, real part of the refractive index, and asymmetry factor. A radiative closure study using surface solar irradiances from the Baseline Surface Radiation Network and the parameters retrieved from MRI v2 showed consistency, with a positive bias of the simulated global irradiance of about +1 %. Furthermore, the MRI v2 retrievals of the refractive index, single-scattering albedo, asymmetry factor, and size distribution have been found to be in agreement with integrated profiles of aircraft in situ measurements of two Saharan dust events at the Cape Verde archipelago during the Sunphotometer Airborne Validation Experiment in Dust (SAVEX-D) 2015 field campaign.

&lt;p class="Body"&gt;&lt;strong&gt;New species and new records of phytoseiid mites (Acari: Phytoseiidae) from Cape Verde archipelago &lt;/strong&gt;&lt;/p&gt;

The phytoseiid mites of the Cape Verde archipelago are scarcely known. We report the results of a survey conducted on the islands of Santiago and Santo Antão, where phytoseiids were collected from native, cultivated and invasive plants. Fourteen species were collected, four of which represent new records for the islands. One new species, Typhlodromus (Anthoseius) macrodactylus Ferragut sp. nov., is described and illustrated. We describe the unknown male of Amblyseius neolargoensis van der Merwe, provide a redescription of the male of Euseius fustis (Pritchard &amp; Baker) and additional morphological information for all examined species.

A contribution to the knowledge of the bryophytes of the Cape Verde Islands, with an emphasis on Santo Antão and São Vicente

Introduction The Cape Verdean bryophyte flora comprises representatives of various floristic elements including Afrotropical, Neotropical, Mediterranean and Asiatic elements, together with some endemic taxa. However, the knowledge of Cape Verdean bryophytes lags far behind that of vascular plants. Methods A total of seven sites were sampled during 2016 in the Cape Verde archipelago, one on São Vicente and six on Santo Antão. Results and conclusions Five species are reported new to Cape Verde, Cheilolejeunea rigidula (Nees ex Mont.) R.M.Schust., Riccia trabutiana Steph., Lewinskya acuminata (H.Philib.) F.Lara, Garilleti & Goffinet, Lindbergia patentifolia Dixon and Timmiella cameruniae Broth. The presence of Porella canariensis (F.Weber) Underw in the archipelago is also confirmed. Additionally, Frullania spongiosa Steph., Bryum dichotomum Hedw., Cryptoleptodon longisetus (Mont.) Enroth and Didymodon hastatus (Mitt.) R.H.Zander are reported for the first time from Santo Antão. Cheilolejeunea rigidula, Lindbergia patentifolia and Timmiella cameruniae are new to Macaronesia and a description of the last taxon is presented.

Geo-Climatic Changes and Apomixis as Major Drivers of Diversification in the Mediterranean Sea Lavenders (Limonium Mill.).

The Mediterranean realm, comprising the Mediterranean and Macaronesian regions, has long been recognized as one of the world’s biodiversity hotspots, owing to its remarkable species richness and endemism. Several hypotheses on biotic and abiotic drivers of species diversification in the region have been often proposed but rarely tested in an explicit phylogenetic framework. Here, we investigate the impact of both species-intrinsic and -extrinsic factors on diversification in the species-rich, cosmopolitan Limonium, an angiosperm genus with center of diversity in the Mediterranean. First, we infer and time-calibrate the largest Limonium phylogeny to date. We then estimate ancestral ranges and diversification dynamics at both global and regional scales. At the global scale, we test whether the identified shifts in diversification rates are linked to specific geological and/or climatic events in the Mediterranean area and/or asexual reproduction (apomixis). Our results support a late Paleogene origin in the proto-Mediterranean area for Limonium, followed by extensive in situ diversification in the Mediterranean region during the late Miocene, Pliocene, and Pleistocene. We found significant increases of diversification rates in the “Mediterranean lineage” associated with the Messinian Salinity Crisis, onset of Mediterranean climate, Plio-Pleistocene sea-level fluctuations, and apomixis. Additionally, the Euro-Mediterranean area acted as the major source of species dispersals to the surrounding areas. At the regional scale, we infer the biogeographic origins of insular endemics in the oceanic archipelagos of Macaronesia, and test whether woodiness in the Canarian Nobiles clade is a derived trait linked to insular life and a biotic driver of diversification. We find that Limonium species diversity on the Canary Islands and Cape Verde archipelagos is the product of multiple colonization events followed by in situ diversification, and that woodiness of the Canarian endemics is indeed a derived trait but is not associated with a significant shift to higher diversification rates. Our study expands knowledge on how the interaction between abiotic and biotic drivers shape the uneven distribution of species diversity across taxonomic and geographical scales.

Genetic Consequences of the Transatlantic Slave Trade in the Americas

According to historical records of transatlantic slavery, traders forcibly deported an estimated 12.5 million people from ports along the Atlantic coastline of Africa between the 16th and 19th centuries, with global impacts reaching to the present day, more than a century and a half after slavery’s abolition. Such records have fueled a broad understanding of the forced migration from Africa to the Americas yet remain underexplored in concert with genetic data. Here, we analyzed genotype array data from 50,281 research participants, which—combined with historical shipping documents—illustrate that the current genetic landscape of the Americas is largely concordant with expectations derived from documentation of slave voyages. For instance, genetic connections between people in slave trading regions of Africa and disembarkation regions of the Americas generally mirror the proportion of individuals forcibly moved between those regions. While some discordances can be explained by additional records of deportations within the Americas, other discordances yield insights into variable survival rates and timing of arrival of enslaved people from specific regions of Africa. Furthermore, the greater contribution of African women to the gene pool compared to African men varies across the Americas, consistent with literature documenting regional differences in slavery practices. This investigation of the transatlantic slave trade, which is broad in scope in terms of both datasets and analyses, establishes genetic links between individuals in the Americas and populations across Atlantic Africa, yielding a more comprehensive understanding of the African roots of peoples of the Americas.

The fumarolic CO2 output from Pico do Fogo volcano (Cape Verde)

The Pico do Fogo volcano, in the Cape Verde Archipelago off the western coasts of Africa, has been the most active volcano in the Macaronesia region in the Central Atlantic, with at least 27 eruptions during the last 500 years. Between eruptions fumarolic activity has been persisting in its summit crater, but limited information exists for the chemistry and output of these gas emissions. Here, we use the results acquired during a field survey in February 2019 to quantify the quiescent summit fumaroles' volatile output for the first time. By combining measurements of the fumarole compositions (using both a portable Multi-GAS and direct sampling of the hottest fumarole) and of the SO2 flux (using near-vent UV Camera recording), we quantify a daily output of 1060±340 tons CO2, 780±320 tons H2O, 6.2±2.4 tons H2S, 1.4±0.4 tons SO2 and 0.05±0.022 tons H2. We show that the fumarolic CO2 output from Pico do Fogo exceeds (i) the time-averaged CO2 release during 2015-type recurrent eruptions and (ii) is larger than current diffuse soil degassing of CO2 on Fogo Island. When compared to worldwide volcanoes in quiescent hydrothermal-stage, Pico do Fogo is found to rank among the strongest CO2 emitters. Its substantial CO2 discharge implies a continuous deep supply of magmatic gas from the volcano’s plumbing system (verified by the low but measurable SO2 flux), that becomes partially affected by water condensation and sulphur scrubbing in fumarolic conduits prior to gas exit. Variable removal of magmatic H2O and S accounts for both spatial chemical heterogeneities in the fumarolic field and its CO2- enriched mean composition, that we infer at 64.1±9.2 mol. % H2O, 35.6±9.1 mol. % CO 0.26±0.14 mol. % total Sulfur (S ), and 0.04±0.02 mol. % H2.

Security Challenges for Small Island Developing States: The Case of Cape Verde

&#x0D; &#x0D; &#x0D; &#x0D; This article is an exploratory, descriptive study, with a qualitative and interdisciplinary approach. It integrates concepts and perspectives of contemporary history, international relations, and security studies. Its main aim is to analyse security issues in Africa, taking as a reference the Cape Verde archipelago, which is part of the group of Small Island Developing States. This matter suggests a wider multidimensional approach that prioritizes the intersection of data obtained from a critical analysis in order to deepen regional cooperation and integration mechanisms. This can provide the Cape Verdean state with strategic options to prevent and mitigate potential security threats.&#x0D; &#x0D; &#x0D; &#x0D;

Coastal geomorphic chronosequences across broad spatiotemporal scales. Metrical observations from the Cape Verde hotspot

AbstractThe study of the coastal landscapes of hotspot oceanic islands through comprehensive structural metrics and ecological estimators represents an opportunity to explore geomorphological transformations and broad spatiotemporal scale features of coastal evolution. As part of this approach, a new metrical comparative analysis is presented in this study, comprising four islands in different evolutionary stages. They belong to the Cape Verde archipelago, which forms a double insular chain in which an east–west gradient in age and evolution is particularly evident across the southern chain. A space‐for‐time (SFT) substitution approach is applied to the coasts of (1) Fogo, in the shield stage; (2) Santiago, in the early post‐erosional stage; (3) São Vicente, in the advanced post‐erosional stage; and (4) Boa Vista, in the last erosional stage. From the obtained spatial distributions and frequencies of landforms, the coastal landscapes of these islands are compared in relation to their (i) geomorphic composition, using similarity indices (Whittaker, βw, Sorensen, Cs) and nestedness estimators (NOFD, WNODF), (ii) geomorphic abundance, using morpho‐assembling densities (Dgm), and (iii) geomorphic diversity, using six alpha‐diversity indices (Richness, S, Menhinick, DMN, Simpson, D, Shannon, H', Berger‐Parker, d, and Brillouin, HB). An advanced geomorphological taxonomy is implemented for areas with limited open‐access data, including a set of planform features captured through scale‐frequency decomposition. Photographic, cartographic and fieldwork data are used for landform identification at 1200 random sampling points, empirically determined by a bootstrap method. The results show a chronological ordering of the compared variables and a possible co‐evolution towards an increase in organizational geomorphic complexity of coastal systems at broad space‐timescales. The method proposed in this study can contribute, from a metrical perspective, to finding new long‐term evolutionary features and constitutes an advance in the development of an integrated model of coastal evolution in oceanic islands. © 2019 John Wiley &amp; Sons, Ltd.

Breeding ecology of the Cream-coloured Courser in Cape Verde

The Cream-coloured Courser Cursorius cursor exsul is a data-deficient shorebird distributed across Eurasia and Africa. The subspecies exsul is endemic to the Cape Verde archipelago. In contrast with their mainland breeding sites, where coursers appear to be nomadic and rare throughout their range, the Cape Verde population is year-round resident and locally abundant. Here we investigate the breeding ecology of Cream-coloured Coursers in Maio, Cape Verde, where they breed in rocky semi-desert habitat. Over four consecutive breeding seasons (2015–2018), we found 52 nests, and ringed 56 adults and 100 chicks. Forty eight percent of 52 nests produced at least one chick; the main nest predators were Brown-necked Ravens Corvus ruficollis and domestic dogs Canis familiaris. Although coursers were thought to be sexually monomorphic, we found that adult males had longer tarsi than adult females. Coursers appeared to be socially monogamous and both sexes incubated the eggs and reared the young. Maio is currently a rural island with little development; however, the island is faced with the threat of touristic development. Therefore, research is required to understand how the courser population will respond to anthropogenic pressures in the future.

Computation of Dolphins' Sound ASPL While Foraging.

Scheduled scientific surveys are a valuable asset in beginning to understand the behavior and vocalization of free-ranging cetaceans. The fortuity of a nonscheduled survey has proven to be beneficial as well. In October 2003 a team of biologist oceanographers began a trip aboard a 44.29feet catamaran sailing boat from Piraeus Greece to Cape Verde Archipelago intending to observe free-ranging cetaceans. Acoustic recordings were conducted using a towed stereophonic hydrophone array consisted of two Benthos AQ4 type hydrophones. Photographs were taken in order to ensure species identification. Information on vocalization administration during foraging of Lagenodelphis hosei and Steno bredanensis has been acquired. Calculation of ASPL (apparent source power level) revealed that dolphins' vocalizations did not match to usual vocalization activities. The relation of vocalization administration by dolphins with brain to mash ratio (BMR) is introduced as an additional predator's strategy.

Deep sea rock record exhumed on oceanic volcanic islands: the Cretaceous sediments of Maio, Cape Verde

Revising the deep water stratigraphy exposed on Maio offers a key section recording the sedimentary evolution in the distal domain of the Central Atlantic and the related North West African Atlantic margin (NWAAM). The oceanic volcanic island is one of nine islands in the Cape Verde archipelago, and is unique to the Central Atlantic due to the exposures of ophiolites and the overlying Mesozoic deep water sediments uplifted during the Cenozoic. This provides the opportunity to assess at outcrop, the exhumed sediments, stratigraphy and palaeo-environments of the early Central Atlantic and contribute towards the knowledge of passive margin evolution along the NWAAM, part of the largest continental remnant of Gondwana.Combined with the previous recording of calpionellids, the first collection of lower Valanginian ammonites from the lowest sedimentary succession provides conclusive evidence that Jurassic sediments are not present on Maio. Bed-by-bed sampling and ensuing micro-palaeontological analysis of these 71 samples, together with a re-interpretation of Stahlecker's remaining historical palaeontological collection providing a comprehensive dataset to build a high-resolution stratigraphic framework for the Mesozoic sediments. This reveals pelagic deep water limestones of the Morro Fm. were deposited until the upper Barremian. A major lithological change from carbonate- to siliciclastic-dominated facies, corresponding to the Morro-Carquiejo Fm. boundary is recognised as a regional hiatus spanning part of the Aptian identified across the Central Atlantic. The overlying Albian and younger Carquiejo Fm. is seen as an equivalent to the Albian-Cenomanian black shales of DSDP Leg 41, yet organic content is absent due to degradation. Future studies can build on this multi-disciplinary investigation revising the stratigraphy of Maio.

Factors Constraining International Growth in Nautical Tourism Firms

In tourism, entrepreneurial internationalisation is considered a measure of the development of the industry and a key driver of innovation, competitiveness and image enhancement. In nautical tourism, research is still scarce in terms of supporting business’ internationalisation. This paper analyses factors constraining the international growth of island-based nautical tourism organisations. For the research, a sample of 60 nautical tourism SMEs´ owners of six different islands in the Macaronesia Region (Canary Islands, Madeira and Cape Verde archipelagos) were interviewed. As a result, we provide up to date information about current conditions and barriers to the internationalisation process within the segment and also identify the profile of the firms with the best international performance. The study is of great usefulness for the industry as it guides on the areas that require special attention to enhance those social, environmental and economic conditions of nautical tourism firms that ensure sustainable international growth. Moreover, it helps policymakers of island destinations seeking specialisation and positioning within the international nautical tourism market to raise the efficiency of current incentive mechanisms for internationalisation, thus contributing to increase tourism competitiveness. Finally, the study highlights the importance of fostering wider cooperation among islands with common interests in nautical specialisation and the challenges that this represents for the tourism management.

Ash-bearing transgressive coastal dune on São Vincente (Cape Verde Islands): dune history and evidence of explosive volcanic activity around 35 ka

Climbing, transgressive dunes are developed at the relief-controlled narrow desert coast of Praia Grande on Sao Vicente (Cape Verde Islands) and this paper describes one of these spectacular coastal dunes. The dune was initiated during a low sea level in the Late Pleistocene; the dune migrated landwards presumably during the influence of persistent northeasterly trade winds and it reached the present coast of the island some time before 35 ka, when it was covered with volcanic ash. Volcanic activity in the Cape Verde archipelago is presently limited to the island of Fogo or is submarine. However, Late Pleistocene eruptions have been identified on many of the islands, but few eruptions younger than 100 ka have been absolutely dated. The revelation of a 35 ka pyroclastic deposit on Sao Vicente is evidence for the continued activity in the northern part of the archipelago. The Praia Grande ash is not readily reconciled with the young Strombolian or effusive Sao Vicente volcanism, which is also geochemically different. The geochemical composition of the fractionation corrected Praia Grande ash is compared to a large database for volcanic rocks of the northern part of the Cape Verde archipelago. Major and trace elements as well as incompatible element ratios in combination allow identification of the likely source for the Praia Grande ash as the Monte Gordo volcano at the island Sao Nicolau 70 km to the SE and the eruption possibly was of VEI ≥ 5.