Recent studies have improved our understanding of nearshore marine ecosystems surrounding Ascension Island (central Atlantic Ocean), but little is known about Ascension's benthic environment beyond its shallow coastal waters. Here, we report the first detailed physical and biological examination of the seabed surrounding Ascension Island at 100–1000 m depth. Multibeam swath data were used to map fine scale bathymetry and derive seabed slope and rugosity indices for the entire area. Water temperature and salinity profiles were obtained from five Conductivity, Temperature, Depth (CTD) deployments, revealing a spatially consistent thermocline at 80 m depth. A camera lander (Shelf Underwater Camera System; SUCS) provided nearly 400 images from 21 sites (100 m transects) at depths of 110–1020 m, showing high variability in the structure of benthic habitats and biological communities. These surveys revealed a total of 95 faunal morphotypes (mean richness >14 per site), complemented by 213 voucher specimens constituting 60 morphotypes collected from seven targeted Agassiz trawl (AGT) deployments. While total faunal density (maximum >300 m−2 at 480 m depth) increased with rugosity, characteristic shifts in multivariate assemblage structure were driven by depth and substratum type. Shallow assemblages (~100 m) were dominated by black coral (Antipatharia sp.) on rocky substrata, cup corals (Caryophyllia sp.) and sea urchins (Cidaris sp.) were abundant on fine sediment at intermediate depths (250–500 m), and shrimps (Nematocarcinus spp.) were common at greater depths (>500 m). Other ubiquitous taxa included serpulid and sabellid polychaetes and brittle stars (Ophiocantha sp.). Cold-water corals (Lophelia cf. pertusa), indicative of Vulnerable Marine Ecosystems (VMEs) and representing substantial benthic carbon accumulation, occurred in particularly dense aggregations at <350 m but were encountered as deep as 1020 m. In addition to enhancing marine biodiversity records at this locality, this study provides critical baseline data to support the future management of Ascension's marine environment.

Fungal emerging pathogens are one of the main threats for global biodiversity. Sea turtles do not seem to be an exemption, and recent studies on important nesting areas worldwide have shown that two fungal pathogens, i.e. Fusarium falciforme and Fusarium keratoplasticum, are involved in low hatching success in nests of sea turtle species. Although the presence of these pathogens has been detected in Ascension Island, there are no investigations on the distribution of these two pathogens in main nesting beaches in the island. In this study, we analysed 109 eggshells of the species Chelonia mydas from four nesting areas in Ascension Island. We have isolated and identified a total of 46 fungal isolates. A phylogenetic analysis, of the ITS nrDNA region, with a number of reference sequences of the Fusarium solani species complex, showed that 23 of these isolates corresponded to the pathogen F. keratoplasticum. The analyses on isolation frequency, that included other previously obtained isolates, i.e. 11 F. keratoplasticum and one F. falciforme, showed that F. keratoplasticum was the species most frequently isolated in Ascension Island and it was found in all nesting beaches, while F. falciforme was only isolated from Pan Am beach. When compared with other nesting areas worldwide, the abundance of F. keratoplasticum over F. falciforme was higher than any other nesting region tested. These findings are important in order to evaluate the potential threat of this pathogen to nests of the sea turtle population of Ascension Island, and to develop future control strategies.

Environmental specimens lining seawater blowholes of Whale Point, Ascension Island in the South Atlantic Ocean were collected (August 2012) and investigated by morphological and molecular techniques. Reported here, Acremonium stroudii (Ascomycota) sp. nov., a filamentous conidia-forming fungus, was the only fungus isolated from the samples collected. Molecular analysis of the material also indicates the presence of a novel species of green algae being present, however, isolation of this alga has not been possible. Instead it appears that this specimen, which belongs to a novel lineage within the Ulvales, sister to the Dilabifilum species, encourages fungal growth in culture and has been shown to form a symbiotic relationship on low nutrition agar plates, supported by investigation through electron microscopy. As no holotype of this species could be isolated in an axenic culture it was not suitable at this point to try to define this alga, especially as no established genus could be attributed. We recommend trying to further sample areas of Ascension Island looking for other members of this green algal lineage, both investigating free-living green algae and those which are found as lichenized photobionts.

This paper provides a comprehensive checklist of the marine benthic macroalgal flora of Ascension Island (tropical South Atlantic Ocean), based on both new collections and previous literature. 82 marine macroalgae were identified from our work, including 18 green algae (Ulvophyceae), 15 brown algae (Phaeophyceae) and 49 red algae (Rhodophyta). Among our collections, 38 species and infraspecific taxa are reported for the first time from Ascension Island, including seven green, three brown and 28 red macroalgae, raising the total number of seaweeds recorded in Ascension so far to 112 taxa in species and infraspecific level. No seagrasses have been recorded at Ascension Island.

A theory that an ancient population of Isarachnanthus from the eastern Atlantic originated the current species is discussed. Based on analysis of DNA barcoding and cnidome it was possible to identify some specimens from Ascension Island. These specimens were identified as Isarachnanthus maderensis, since the divergence of DNA barcoding was very small and the cnidome data agreed with published data. This material permitted an enhanced discussion about the origin of this population.

This is the first report on the Zoantharia fauna (Cnidaria: Hexacorallia) of the isolated oceanic island of Ascension, southern Atlantic, where zoantharians are a dominant component of the shallow-water benthos. Specimens from two expeditions (1983, 2012) were examined regarding external morphology and molecular phylogeny using three DNA markers, which confirmed the presence of four zoantharian species: Palythoa caribaeorum; Palythoa aff. clavata; Parazoanthus swiftii; and Zoanthus sp. Two of these, Palythoa aff. clavata and Parazoanthus swiftii, were previously only known from the western Atlantic and Caribbean. Molecular examination of the zooxanthellae (=Symbiodinium spp.) of Palythoa specimens showed that they were in association with only one type, subclade C1.

Seven species of antipatharian corals (Cnidaria: Anthozoa: Antipatharia) are recorded from Ascension Island; five of these for the first time. Tanacetipathes spinescens and Stichopathes occidentalis were the two most commonly collected species.

The reef-building fire coral Millepora alcicornis is reported from Ascension Island (South Atlantic). This record, based on a recent expedition to Ascension, is the first in which the identification of a Millepora coral is supported by photographic evidence from the field and by morphological and molecular analyses of collected specimens. This finding is discussed in relation to earlier Millepora records from Ascension and the biogeographic range of this particular species in the Atlantic.

The presence of five shallow-water scleractinian species at Ascension Island is confirmed, i.e. Favia gravida, Madracis sp., Siderastrea radians, Polycyathus atlanticus and Rhizosmilia gerdae. The three former are zooxanthellate, the two latter azooxanthellate. A sixth species, Cladocora debilis (azooxanthellate), dredged from moderately deep water is also expected to occur in shallow water. Madracis sp. and P. atlanticus are new records for the island. A previous record of Astrangia solitaria at Ascension is now referred to as P. atlanticus. Favia gravida, S. radians and C. debilis are amphi-Atlantic. Rhizosmilia gerdae is currently known only from Ascension Island and the Western Atlantic. None of the species are endemic to Ascension Island. No member of the family Dendrophylliidae has as yet been found at Ascension, whereas that family is represented at its nearest neighbour, St Helena Island.

During a recent expedition to Ascension Island in the southern Atlantic Ocean, a polyplacophoran of the genus Acanthochitona was collected, corresponding to the first recorded species of this molluscan class from this remote island. A scanning electron microscope study reveals a close affinity to Acanthochitona subrubicunda, which was so far only known from the Cape Verde Archipelago. Due to the lack of comparable type material the new finding warrants a confirmed identification and is only tentatively attributed to Acanthochitona subrubicunda. It is hypothesized that the class Polyplacophora was either overlooked during earlier surveys or colonized the island in more recent time. If the latter scenario took place, a transport by ships is thinkable.

Common rock oysters Saccostrea cucullata (Bivalvia) were sampled from intertidal volcanic rocks at five sites around Ascension Island (central-east Atlantic) in austral winter 2012–2014. Their left valves were sectioned to reveal annual growth increments. Their periodicity was validated by the presence of specific growth marks in the increment sequence visible in consecutive years of sampling. No significant differences in shell height-weight relationships were revealed between sites. Marginal analysis of the increment width showed that S. cucullata accelerated their growth in cooler winter months and decelerated the growth in warmer summer months. Rock oysters in Ascension Island lived up to 14–16 years with maximum age of 26 years. Young oysters (1–5 years old) had the same growth rates both in shell height and weight in all sites. However, their starting point (size and weight of 1-year-old animals) was different in various sites, with largest animals occurring in the most protected site Northeast Bay with sheltered inlets and smallest animals inhabiting exposed to surf site of Letterbox. Growth in shell height was best described by von Bertalanffy growth function with the largest L∞ in animals inhabiting the windward side and smallest animals occurring in the leeward side of the Island. In summary, S. cucullata around Ascension Island lived longer but had slower growth than those from tropical regions of Southwest Asia probably due to comparatively low productivity observed in the central part of the equatorial tropical Atlantic.

The small volcanic island of Ascension is situated in the middle of the South Atlantic Ocean, more than 1500 km from the coast of Africa, its nearest continental area. To date, eight ‘opisthobranch’ species were reported from the island. As a result of a recent survey, 10 species were found. Seven species are new records from Ascension: Platydoris angustipes (Mörch, 1863), Diaulula sp., Dolabrifera dolabrifera (Rang, 1828), Aplysia parvula Guilding in Mörch, 1863 and Caliphylla mediterranea A. Costa, 1867, and two new species: Phidiana mimica sp. nov.; and Felimida atlantica sp. nov. Half of the species found have a wide geographical distribution, being not restricted to the Atlantic Ocean. However, traditional taxonomy based on few characters is probably masking complexes of species.

Recent molecular studies have proved beneficial in providing taxonomic resolution within the Octopus vulgaris species complex, therefore aiding in the appropriate management of this high value global fisheries resource. This study used the mitochondrial ‘barcode of life’ gene Cytochrome Oxidase subunit I (COI) to investigate the identity of shallow-water benthic octopuses in the mid-Atlantic Ocean and their relationship to members of the Octopus vulgaris species complex. Maximum likelihood and Bayesian phylogenetic inference placed individuals collected from two tropical islands, Ascension and St Helena, into a highly supported monophyletic clade with the North Brazilian species O. insularis (BS = 81, PP = 1), extending the known distribution of O. insularis to Ascension and St Helena Islands. Octopus vulgaris and two other member species of the O. vulgaris species complex, O. tetricus and O. cf. tetricus formed a highly supported monophyletic clade (BS = 99, PP = 1). Interspecific distances between the O. mimus group (O. mimus, O. bimaculoides, O. maya and O. insularis) and the O. vulgaris species group (O. vulgaris, O. tetricus and O. cf. tetricus) ranged from 14.7–26.0%, and an estimated date of divergence suggests these groups diverged from a common ancestor between 19.0 and 40.9 million years ago.

The decapod Crustacea from Ascension Island are reported upon on the basis of major expeditions undertaken during 2008 and 2012, including several minor additional collections made in other years. Two species, Gnathophyllum americanum and Corallianassa longiventris are new records for the island bringing the total known marine decapod fauna to 75 species, of which 11 are currently endemic to Ascension Island.

Little is known about colonization of remote island coasts by marine invertebrates, other than corals. The structure of hard substrata assemblages was investigated across Ascension Island's littoral zone in comparison with other sites. Arrays of acrylic panels were deployed at two sites for 2 years at Ascension Island to measure subtidal recruitment. Colonization of panels at Ascension I. was low, though space occupation, abundance and richness varied considerably. After ~1 and 2 years Ascension panels were <17 and <37% covered by fauna and each had <22 recruits and 54 recruits (per 100 cm2) respectively, amongst the lowest density of recruits reported. Recruitment rates of corals (25 m2 year−1) at Ascension I. were also similar to the lowest levels reported elsewhere (e.g. at Bermuda or Midway islands). Less dispersive animal types, e.g. cheilostome bryozoans, were poorly represented. Panels immersed in Tanzania and Scotland were >30% covered, with >76 recruits per 100 cm2 and with bryozoans well represented after 1 year. Across-littoral surveys of established macrofauna at five remote islands (Ascension I., Easter I., Azores, South Georgia and Signy I., Antarctica) revealed similar trends of a rich sublittoral and lower littoral reducing drastically up-shore; molluscs dominating abundance and species numbers, whilst polychaetes, crustaceans and echinoderms were well represented. Established sessile animals occurred patchily at a mean density of 8.26 m−2 but recruits had mortality levels >99%. Polar or remote temperate/tropical sites are typically less colonized than at non-remote, low latitudes but the lowest levels reported are at remote polar sites. Reduced colonization at Ascension island reflects remoteness.

A checklist of the fishes of Ascension Island is presented. The species Rhincodon typus, Alopias superciliosus, Isurus oxyrinchus, Carcharhinus obscurus, Galeocerdo cuvier, Sphyrna lewini, Hexanchus griseus, Manta birostris, Gymnothorax vicinus, Hippocampus sp., Epinephelus itajara, Cookeolus japonicus, Apogon pseudomaculatus, Phaeoptyx pigmentaria, Remora albescens, Caranx bartholomaei, Carangoides ruber, Decapterus tabl, Seriola dumerili, Thalassoma sanctaehelenae, Cryptotomus sp., Ruvettus pretiosus, Acanthocybium solandri, Auxis rochei, Auxis thazard, Euthynnus alletteratus, Katsuwonus pelamis, Thunnus alalunga, Thunnus obesus, Xiphias gladius, Istiophorus platypterus, Kajikia albida, Makaira nigricans, Tetrapturus pfluegeri, Hyperoglyphe perciformis, Schedophilus sp., Cantherhines macrocerus, Sphoeroides pachygaster and Diodon eydouxii are recorded for the first time from Ascension Island. We have recognized two previous records as identification errors and indicate 11 other records as doubtful. Including the 40 new records, we now list 173 fish species from Ascension Island, of which 133 might be considered ‘coastal fish species’. Eleven of these (8.3%) appear to be endemic to the island and a further 16 species (12%) appear to be shared endemics with St Helena Island.

Isolated oceanic islands may give rise not only to new and endemic species, but also to unique behaviours and species interactions. Multi-species fish interactions, such as cleaning, following, mob-feeding and others are understudied in these ecosystems. Here we present qualitative and quantitative observations on cleaning and mob-feeding reef fish associations at the isolated Ascension Island, South Atlantic Ocean. Cleaning interactions were dominated by juveniles of the facultative fish cleaners Bodianus insularis and Pomacanthus paru, with lesser contributions of Chaetodon sanctaehelenae, Thalassoma ascensionis and the cleaner shrimp Lysmata grabhami. Two types of feeding mobs were consistently identified: less mobile mobs led by the surgeonfish Acanthurus bahianus and A. coeruleus and the more mobile mobs led by the African sergeant Abudefduf hoefleri. This is the first record of A. hoefleri from outside of the Eastern Atlantic and also the first report of this species displaying mob-feeding behaviour. The principal follower of both mob types was the extremely abundant Melichthys niger, but the main aggressor differed: Stegastes lubbocki, a highly territorial herbivore, was the main aggressor of Acanthurus mobs; and Chromis multilineata a territorial fish while engaged in egg parental care, was the principal aggressor towards Abudefduf mobs. Our study enhances the scarce information on reef fish feeding associations at the isolated Ascension Island and at oceanic islands in the Atlantic in general.

Ascension Island in the South Atlantic Ocean is renowned for its globally-important nesting population of green turtles (Chelonia mydas) that has been the subject of long-term research. By comparison, very little is known about the apparently small population of hawksbill turtles (Eretmochelys imbricata) that have been recorded in its waters, thousands of kilometres from known nesting beaches. Here, we collate 10 years of in-water tagging data, opportunistic public sighting records and underwater observations to provide a baseline for future research, and present preliminary data on habitat use derived from two individuals fitted with GPS transmitters. Although public sightings were inevitably biased towards popular recreation areas, the resulting distribution suggests that hawksbill turtles occur year round in Ascension Island's waters along the entire 65 km of coastline. Hawksbills were observed feeding on benthic algae and encrusting sponges, and were frequently seen scavenging on fish discards around the Island's pier at night aided by anthropogenic lighting. Between 2003 and 2013, 35 turtles were captured, measured, tagged and then released. Curved carapace lengths ranged from 33.5 to 85 cm (mean = 48.8 cm) indicating that most (if not all) individuals encountered around Ascension are post-pelagic juveniles. Four individuals were recaptured at least once giving a mean minimum residence time of 4.2 yr (range: 2.8–7.3 yr) and a mean growth rate of 2.8 cm yr−1. Turtles fitted with Fastloc™ GPS devices remained at Ascension Island for the duration of the study (>90 days) and occupied restricted home ranges with an average area of 2.5 km2 and an average ‘core use area’ (50% utilization distribution) of 0.05 km2. Together, these results suggest that Ascension Island serves as a mid-Atlantic developmental habitat for benthic-feeding, juvenile hawksbill turtles on extended oceanic migrations before recruiting to their adult foraging grounds, likely to be located in Brazil or tropical West Africa.

Malcolm Roy Clarke (1930–2013) was a British teuthologist who made an important contribution to marine science in the Azores archipelago (Portugal). Malcolm started doing research in the Azores from 1980s onward, settling for residency in 2000 after retirement (in 1987). He kept publishing on Azorean cephalopods collaborating in 20% of the peer reviewed works focusing on two main areas: dietary studies; and the ecology of cephalopods on seamounts. Since his first visit in 1981, he was involved in the description of the dietary ecology of several cetaceans, seabirds, and large pelagic and deep-water fish. Using his own data, Malcolm revised the association of cephalopods with seamounts, updating and enlarging the different cephalopod groups according to species behaviour and ecology. Malcolm taught several students working in the Azores on cephalopods and beak identification, lecturing the Third International Workshop in Faial (2007). He empowered the recently established research community, by providing important contacts with foreign institutes and informal advice. He collaborated in the regional cetacean stranding network (RACA) and was an active member of the advisory board of the journal Arquipelago—Life and Marine Sciences. But the scientific role of Malcolm Clarke in the Azores went beyond his academic activities. In the last 10 years Malcolm and Dot Clarke dedicated themselves to building and running a museum on Pico Island, showing the biology of the sperm whale and its interaction with squid; a cultural and touristic legacy for future generations to enjoy.