NE Atlantic Ocean Research Articles

Long-term and seasonal changes in the life-history biology of the abyssal holothurian Pseudostichopus aemulatus from the Porcupine Abyssal Plain (North-East Atlantic)

Long-term interannual variations in the benthic community structure are well-known from abyssal plains in the North Atlantic and North Pacific, where rapid responses to changes in the environment by first-order opportunists modify overall species composition. To increase our knowledge of the long-term variations of deep-sea benthic communities in the North-East Atlantic, we studied the response of a second-order opportunist echinoderm, the holothurian Pseudostichopus aemulatus, before, during and after the “Amperima Event” – a four-year episode (1996–1999) where the first-order opportunistic holothurian, Amperima rosea, increased dramatically in density. We used a collection of 14 sampling times of deep-sea community assemblage over a sixteen-year period to understand the temporal variation (i.e., interannual and seasonal) in population structure (i.e., density and individual sizes) and reproduction (i.e., mean oocyte sizes, sex ratios, gonadal indices, and fecundity) in P. aemulatus. Samples were collected from the Porcupine Abyssal Plain (PAP) in the NE Atlantic Ocean at a depth of ca. 4850 m between 1989 and 2005 with a semi-balloon otter trawl (OTSB14) and an epibenthic sledge (BN1.5/C) at varying seasons. We measured individual body size, dissected organisms to prepare histological slides of their gonads, and measured the Feret oocyte diameter in females. We found changes in the life-history biology of P. aemulatus during the “Amperima Event”. Population density increased gradually from September 1997 until April 1999, when P. aemulatus reached a peak in density coinciding with the smallest mean body size observed (1998 and 1999) suggesting recruitment of juveniles. In 1997, before these changes in population structure, mean oocyte sizes were at their largest, suggesting a strong reproductive effort with individuals either preparing to spawn or spawning. This reproductive effort was minimal in the years after 1999, when we found the largest proportions of previtellogenic oocytes in individuals that were probably allocating their energy into growth rather than reproduction given their smaller size. The presence of gametes of all sizes across seasons and a broad range of individual sizes in various sampling times suggests no seasonal reproductive patterns. We suggest that feeding guild differences between various holothurian species explain the diverse life-history responses observed among holothurians competing for resources in a food-poor environment.

In situ recordings of large gelatinous spheres from NE Atlantic, and the first genetic confirmation of egg mass of Illex coindetii (V\xe9rany, 1839) (Cephalopoda, Mollusca)

In total, 90 gelatinous spheres, averaging one meter in diameter, have been recorded from ~ 1985 to 2019 from the NE Atlantic Ocean, including the Mediterranean Sea, using citizen science. More than 50% had a dark streak through center. They were recorded from the surface to ~ 60–70 m depth, mainly neutrally buoyant, in temperatures between 8 and 24°C. Lack of tissue samples has until now, prohibited confirmation of species. However, in 2019 scuba divers secured four tissue samples from the Norwegian coast. In the present study, DNA analysis using COI confirms species identity as the ommastrephid broadtail shortfin squid Illex coindetii (Vérany, 1839); these are the first confirmed records from the wild. Squid embryos at different stages were found in different egg masses: (1) recently fertilized eggs (stage ~ 3), (2) organogenesis (stages ~ 17–19 and ~ 23), and (3) developed embryo (stage ~ 30). Without tissue samples from each and every record for DNA corroboration we cannot be certain that all spherical egg masses are conspecific, or that the remaining 86 observed spheres belong to Illex coindetii. However, due to similar morphology and size of these spheres, relative to the four spheres with DNA analysis, we suspect that many of them were made by I. coindetii.

Discovery of Two Sub‐Volcanic Basins Below the North Atlantic Igneous Province (NAIP), Faroe Platform, NE Atlantic Ocean

AbstractThe Faroe Platform lies on the outer continental margin of NW Europe. Its pre‐breakup structural configuration has long been debated as it is entirely buried beneath a thick cover of lower Palaeogene volcanic rocks. Here we present the results of an integrated geological and geophysical study designed to test whether low‐gravity areas on the Faroe Platform are basins inverted during the Neogene, and high‐gravity areas are basement blocks. Based on a series of profiles constructed from forward gravity modeling, our results identify two new sedimentary basins—the Beinta and Kerstin basins—bounded by four basement highs—the West Suðuroy High, East Suðuroy High, Borðoy High, and the Sandoy High. The Beinta and Kerstin basins extend to depths of 8–10 km and 8–9 km, respectively, whereas the tops of the structural highs are located between 3–6 km below the present‐day surface of the platform. Deformation of the A‐horizon, which marks the boundary between pre‐and syn‐breakup volcanism, is consistent with a phase of Miocene‐Pliocene basin inversion, also evident in the adjacent Faroe‐Shetland Basin. Our study also gives indications of cross‐cutting intrusive networks that likely represent part of the magmatic plumbing system in the central part of the Faroe Platform.

Suspended particulate matter in a submarine canyon (Whittard Canyon, Bay of Biscay, NE Atlantic Ocean): Assessment of commonly used instruments to record turbidity

Nepheloid layers with elevated concentrations of suspended particulate matter (SPM) are found throughout the world's oceans. They are generated by both natural processes, involving resuspension of seabed sediment by bottom currents, and anthropogenic sediment resuspension due to bottom trawling, dredging and in the future potentially due to deep-sea mining. These nepheloid layers represent pathways of lateral SPM transport, including lithogenic and biogenic sediment, organic matter, (trace) metals, organic pollutants and plastics. For assessment of the dispersion of these materials, it is essential that SPM mass concentrations can be accurately quantified. However, this is not straightforward as the detected turbidity signal, which is used as a proxy for SPM mass concentration, not only depends on the concentration of particles, but also on physical characteristics of these particles, such as particle size, substance and shape. Here we present a comparative study of turbidity data to assess the potential implications different sensors have on the estimates of SPM mass concentration. Optical backscatter sensors (OBSs), transmissometers and both low- and high-frequency ADCPs were deployed simultaneously in the Whittard Canyon (North Atlantic Ocean), and water samples were collected for quantification of SPM mass concentration and ex-situ particle size analysis. We found that SPM mass concentrations inferred from the transmissometer are easily overestimated in the biologically productive surface layer due to higher light absorption by chlorophyll-bearing phytoplankton, compared to suspended detritic particles. Furthermore, we observed that depending on sensor type some particles are not, or less well, detected. This is due to differences in particle size sensitivities of these sensors towards the diverse range of particle sizes found in the Whittard Canyon, whereby the low-frequency ADCP was most sensitive for coarse-grained material and the high-frequency ADCP and OBSs most sensitive for fine-grained material. In future studies, we suggest to use a combination of different sensors as the use of only one type of sensor could potentially lead to misinterpretation and mis-quantification of particle transport processes and fluxes.

Untangling the origin of the newcomer Phorcus sauciatus (Mollusca: Gastropoda) in a remote Atlantic archipelago

The marine topshell Phorcus sauciatus is currently found along the temperate–subtropical shores of the Northeast Atlantic Ocean. Although present in the Iberian Peninsula, Madeira, and Canaries for centuries, P. sauciatus has only recently reached another oceanic volcanic archipelago in the region. In 2013, a small population was recorded for the first time in Santa Maria Island (Azores), widening its distribution around the entire island and to the neighbouring island of Sao Miguel in a short period of time. The success of such colonization of the remote archipelago by P. sauciatus still awaits an explanation. To better understand the populational dynamics of the species in the NE Atlantic Ocean, we used a molecular approach to evaluate the genetic structure of P. sauciatus aiming at the determination of a potential origin for the first individuals that reached the Azores. On the foundations of detailed oceanographic, palaeontological, and ecological data, we discuss the impact of climate change as a trigger for colonization of remote oceanic islands and suggest a mechanism that might explain the long-distance dispersal of the non-planktotrophic gastropod P. sauciatus across important biogeographical barriers in the NE Atlantic.

Anisakis simplex (s.s.) larvae (Nematoda: Anisakidae) hidden in the mantle of European flying squid Todarodes sagittatus (Cephalopoda: Ommastrephidae) in NE Atlantic Ocean: Food safety implications

Few reports exist upon the occurrence and localization of zoonotic anisakid nematodes in T. sagittatus, especially in the mantle of the squid. The occurrence and site of infection of larval anisakids in 98 T. sagittatus caught West off St. Kilda, NE Atlantic Ocean, were investigated. Squids were examined for anisakids using the UV-Press method. In total, 689 nematodes were detected in the viscera and mantle. According to morphology, all the larvae (L3) were assigned to genus Anisakis. Diagnostic allozymes and mtDNA cox2 sequence analysis permitted to genetically identify all larvae as Anisakis simplex (s.s.) (N = 100). Overall prevalence (P = 81%) and mean intensity (mI = 8.6) of infection with A. simplex are provided. Most of the larvae present in the mantle cavity were embedded in the stomach wall or attached in the outer layer of the stomach and caecum (49%). Over a third of squids (37%) hosted A. simplex (s.s.) larvae in the mantle. A novel schematized representation of larvae distribution in the mantle is provided, showing where they were mostly located. According to the results obtained, the risk of anisakiasis associated with consumption of raw or undercooked T. sagittatus should be considered.

Anthropogenic disturbances and conservation of coastal environments in an oceanic archipelago

Oceanic islands are biotically fragile environments prone to suffer irreversible anthropogenic disturbances. The growth of the human population and the intensive occupation of the coastline are the cause of great ecological pressure on global insular coastal ecosystems. We review the current situation and future scenarios on a paradigmatic oceanic archipelago (Canary Islands, NE Atlantic Ocean), as a case study of the human footprint on marine coastal communities. The role of humans is pivotal, as we directly affect patterns of coastal occupation, pollution, invasive species or fishing. Here we synthesize the information that describes the current situation of the coastal ecosystems of the Canary Islands, indicating the main sources of environmental conflict and impacts. In addition, we review the state of the most relevant or threatened habitats and the taxonomic groups as actors of the main disturbances in the coastal ecosystems of the archipelago. We propose future general scenarios about expected changes, and foreseeable interactions that could occur to transform the coastal environments of the islands, in order to indicate areas susceptible to improvement for the conservation of these ecosystems. Integrative coastal actions are urgently needed for sustainable future scenarios to oppose deleterious trends such as tropicalization, fisheries collapse and extensive coastal degradation due to urbanization and infrastructure construction.

The potential of video imagery from worldwide cabled observatory networks to provide information supporting fish-stock and biodiversity assessment

AbstractSeafloor multiparametric fibre-optic-cabled video observatories are emerging tools for standardized monitoring programmes, dedicated to the production of real-time fishery-independent stock assessment data. Here, we propose that a network of cabled cameras can be set up and optimized to ensure representative long-term monitoring of target commercial species and their surrounding habitats. We highlight the importance of adding the spatial dimension to fixed-point-cabled monitoring networks, and the need for close integration with Artificial Intelligence pipelines, that are necessary for fast and reliable biological data processing. We then describe two pilot studies, exemplary of using video imagery and environmental monitoring to derive robust data as a foundation for future ecosystem-based fish-stock and biodiversity management. The first example is from the NE Pacific Ocean where the deep-water sablefish (Anoplopoma fimbria) has been monitored since 2010 by the NEPTUNE cabled observatory operated by Ocean Networks Canada. The second example is from the NE Atlantic Ocean where the Norway lobster (Nephrops norvegicus) is being monitored using the SmartBay observatory developed for the European Multidisciplinary Seafloor and water column Observatories. Drawing from these two examples, we provide insights into the technological challenges and future steps required to develop full-scale fishery-independent stock assessments.

Global patterns of parasite diversity in cephalopods

We compiled an updated global catalogue of parasites in cephalopods. Data were used to assess changes in taxonomic distinctness of parasites over two centuries and across the world’s oceans, to quantify turnover and nestedness components of parasite β-diversity, and to attempt estimating their γ-diversity at a global scale. A total of 309 parasites infecting 164 cephalopods were found. We hypothesize that this diversity counts for less than half the potential parasite richness in this molluscan taxon. Taxonomic breadth of parasites was significantly above expectations from null models for Mediterranean Sea and NE Atlantic Ocean, whereas the opposite occurred for NW Pacific Ocean, where a few closely related genera characterized the parasite pool. β-diversity of parasites was very high and dominated by turnover, except for the Atlantic Ocean where a nested pattern among sub-basins emerged. Taxonomic relatedness of parasite species remained substantially unchanged through time, but species replacements largely occurred over the last two centuries. Our findings highlighted potential hotspots of taxonomic distinctness in cephalopod parasites, geographic regions deserving future research, and the need for a deeper understanding of the magnitude of marine parasite diversity, their biogeography, and their role in marine ecosystems. Our global overview may represent a baseline step for future advances in this direction.

Seasonal variation in the survival of discarded Nephrops norvegicus in a NW Mediterranean bottom-trawl fishery

The landing obligation in the revised European Union Common Fisheries Policy allows for exemptions to obligatory landing of the entire catch for species for which “high survival” of discards can be demonstrated. Nephrops norvegicus is an important target species in many fisheries across Europe in the Mediterranean Sea, NE Atlantic Ocean and North Sea. Historically, Mediterranean fisheries have had a high discard rate of small-sized Nephrops, and it is suspected that this unwanted component of the catch may have a high survival potential that is comparable to those of other EU fisheries, where survival rates of up to 0.56 have been demonstrated. However, to date, no investigations have confirmed a high discard survival rate for Nephrops in the Mediterranean Sea. Furthermore, the environmental, technical and biological characteristics that could affect Nephrops survival have been shown to be substantially different from those in the survival assessments conducted in the NE Atlantic and the North Sea. To address this knowledge gap, this study was conducted to determine the survival of Nephrops discarded from trawls in the Mediterranean Sea. The survival and vitality status of the discarded Nephrops removed from trawl catches were monitored onboard and for 14 days in the laboratory. The results showed seasonality in survival, with the highest survival rate in winter (0.74; CI: 0.7−0.78), lower survival in spring (0.36; CI: 0.31−0.41) and the lowest survival in summer (0.06; CI: 0.04−0.09). Survival was monitored to the asymptote in all cases, and season and vitality status were shown to have statistically significant relationships with survival.

Comparison of Modern and Pleistocene (MIS 5e) Coastal Boulder Deposits from Santa Maria Island (Azores Archipelago, NE Atlantic Ocean)

Modern and palaeo-shores from Pleistocene Marine Isotope Substage 5e (MIS 5e) featuring prominent cobble/boulder deposits from three locations, on the southern and eastern coast of Santa Maria Island in the Azores Archipelago, were compared, in order to test the idea of higher storminess during the Last Interglacial. A total of 175 basalt clasts from seven transects were measured manually in three dimensions perpendicular to one another. Boulders that exceeded the minimum definitional diameter of 25 cm contributed to 45% of the clasts, with the remainder falling into the category of large cobbles. These were sorted for variations in shape, size, and weight pertinent to the application of two mathematical formulas to estimate wave heights necessary for traction. Both equations were based on the “Nott-Approach”, one of them being sensitive to the longest axis, the other to the shortest axis. The preponderance of data derived from the Pleistocene deposits, which included an intertidal invertebrate fauna for accurate dating. The island’s east coast at Ponta do Cedro lacked a modern boulder beach due to steep rocky shores, whereas raised Pleistocene palaeo-shores along the same coast reflect surged from an average wave height of 5.6 m and 6.5 m. Direct comparison between modern and Pleistocene deposits at Ponta do Castelo to the southeast and Prainha on the island’s south shore produced contrasting results, with higher wave heights during MIS 5e at Ponta do Castelo and higher wave heights for the modern boulder beach at Prainha. Thus, our results did not yield a clear conclusion about higher storminess during the Last Interglacial compared to the present day. Historical meteorological records pit the seasonal activity of winter storms arriving from the WNW-NW against the scant record of hurricanes arriving from the ESE-SE. The disparity in the width of the marine shelf around Santa Maria Island with broad shelves to the north and narrow shelves to the south and east suggested that periodic winter storms had a more regular role in coastal erosion, whereas the rare episodic recurrence of hurricanes had a greater impact on southern and southeastern rocky shores, where the studied coastal boulder deposits were located.

Low-quality management of Marine Protected Areas in the North-East Atlantic

The effectiveness of a marine protected area (MPA) requires adequate management plans (MgPs), good management performance and effective governance. This study diagnosed management quality on 126 MPAs and 57 MgPs in four countries in the NE Atlantic Ocean (France, England, Spain and Portugal) by adapting the MPA Management Effectiveness Assessment Tool to assess management quality, and management effort, strengths and weaknesses. Despite the fact that these MPAs were, in 2013, on average 14-year old, fewer than 30% showed sufficient management capacity, 18% showed operational management, and only 3% showed effective management. Therefore, 70% could be considered unmanaged or “paper” reserves. Among their strengths, MPAs were in general well legislated in the four countries and had operational management bodies in France and England. However three key factors need to be improved in all countries: (i) periodic MgP updated; (ii) periodic MPA monitoring and assessment; and (iii) education and communication activities. Enforcement should be improved in England, France and Portugal; Portugal and Spain also need to improve the management body and England and Portugal the community participation.

Pliocene and Late Pleistocene actinopterygian fishes from Santa Maria Island, Azores (NE Atlantic Ocean): palaeoecological and palaeobiogeographical implications

AbstractFossil fishes are among the rarest in volcanic oceanic islands, their presence providing invaluable data for the understanding of more general (palaeo)biogeographical patterns and processes. Santa Maria Island (Azores Archipelago) is renowned for its palaeontological heritage, with representatives of several phyla, including the Chordata. We report on the fossil fishes, resulting in an increase in the number of Pliocene fishes from the Azores to 11 taxa: seven Chondrichthyes and at least four Actinopterygii. The genusSparisomais reported for the first time in the fossil record. The presence of fossil remains of the parrotfishSparisoma cretensein Last Interglacial outcrops is significant, because it posits a setback for the theory that most of the present-day Azorean marine species colonized the area after the last glacial episode. Our multidisciplinary approach combines palaeontological data with ecological and published genetic data, offering an alternative interpretation. We suggest that most of the Azorean shallow-water subtropical and temperate marine species living in the archipelago during the Last Interglacial were not affected by the decrease in sea surface temperatures during the last glacial episode. We also predict low genetic diversity for fish species presently living in the Azores and ecologically associated with fine sediments, as a result of the remobilization and sediment transport to abyssal depths, during the Last Glacial episode; these are viewed as post-glacial colonizers or as ‘bottleneck’ survivors from the Last Glaciation.

Difficulties to identify global and local key biodiversity areas in diverse and isolated marine jurisdictions

Biodiversity conservation requires efficient methods to be integrated into environmental management planning. The Key Biodiversity Area (KBA) approach has been recently developed for identifying sites of greatest conservation importance. They are regarded as priorities for management intervention and for identifying investment priorities. While the KBA approach has been extensively used to identify locations of high biodiversity significance in the terrestrial realm, this methodology is scarcely known by stakeholders in marine jurisdictions. Identification of a network of KBA sites should be regarded as a high priority in diverse and isolated areas, such as oceanic islands. In the Canary Islands (NE Atlantic Ocean), a number of KBA sites are here identified across the archipelago using irreplaceability and vulnerability criteria to safeguard populations of threatened marine species. If global standards associated with the IUCN Red List are considered, only nesting beaches and regular feeding grounds of sea turtles (Caretta caretta and Chelonia mydas) qualify as KBAs. However, this approach overlooks most of the biodiversity hotspots in the Canary archipelago that include representative ecosystems of volcanic islands (e.g. marine caves) or habitats with high conservation importance in terms of productivity, regional rarity and diversity (e.g. seagrass meadows and maerl seabeds), as well as presence of locally threatened species.

First record of ‘plasticrusts’ and ‘pyroplastic’ from the Mediterranean Sea

We report the presence of ‘plasticrusts’ and ‘pyroplastic’ from coastal habitats in Giglio island, Tyrrhenian Sea, Italy. These novel plastic debris types have only recently been described for the first time from Madeira island (NE Atlantic Ocean) and the United Kingdom, respectively. While ‘plasticrusts’ are generated by sea waves smashing plastic debris against intertidal rocks, ‘pyroplastic’ derives from (un)deliberately burnt plastic waste. Using Fourier-transform infrared (FTIR) spectroscopy, we identified the ‘plasticrust’ material as polyethylene (PE) and the ‘pyroplastic’ material as polyethylene terephthalate (PET). These polymers are widely used in everyday products and, therefore, contribute heavily to plastic pollution in aquatic and terrestrial environments worldwide. Furthermore, our field surveys suggest that ‘plasticrust’ abundance is related to wave-exposure and that the ‘pyroplastic’ derived from beverage bottles which we frequently found along the Giglio coast. Overall, our findings corroborate the notion that ‘plasticrusts’ and ‘pyroplastic’ are common debris types in marine coastal habitats.

Population structure and movement patterns of blackbelly rosefish in the NE Atlantic Ocean (Azores archipelago)

AbstractBlackbelly rosefish Helicolenus dactylopterus (Delaroche, 1809) is one of the most important species of the demersal/deep‐water assemblages fished in the NE Atlantic Ocean (Azores archipelago). However, there is insufficient information about the stock structure of this species to support analytical resource assessments and it is currently managed with a precautionary approach. Here, we examine the depth and temporal distribution, size composition, sex, and movement patterns of blackbelly rosefish in order to test the hypothesis that the stock structure in the Azores region comprises different local management units (MUs). We also evaluate annual abundance indices and size composition from scientific surveys and commercial landings over the past c. 25 years for an assessment of the species' vulnerability to bottom longline fishing pressure. The greatest abundance occurred in seamount areas at 350–800 m depth. Larger individuals were mainly found in deeper waters, and no sexual segregation by depth was observed. Tagging results indicated a strongly sedentary behavior and an intraregional separation among populations. Although the abundance pattern and size composition were very similar over time, this species is particularly vulnerable to overfishing due to its biological characteristics (long life, large size, late maturity, slow growth, and low mortality rate). Proper monitoring and management of its exploitation should be a priority. Exploratory analysis for analytical assessment should be performed under the assumption of local MUs. Further oceanographic research is needed to understand larval transport and mixing of populations.

On the genus Crossaster (Echinodermata: Asteroidea) and its distribution.

Several starfish (Echinodermata, Asteroidea) are keystone species of marine ecosystems, but some of the species are difficult to identify using morphological criteria only. The common sunstar, Crossaster papposus (Linnaeus, 1767), is a conspicuous species with a wide circumboreal distribution. In 1900, a closely similar species, C. squamatus (Döderlein, 1900) was described from the NE Atlantic Ocean, but subsequent authors have differed in their views on whether this is a valid taxon or rather an ecotype associated with temperature variations. We assessed the differentiating morphological characters of specimens from Norwegian and Greenland waters identified as C. papposus and C. squamatus and compared their distributions in the NE Atlantic as inferred from research cruises. The field data show that C. papposus is found mainly in temperate and shallow waters, whereas C. squamatus resides on the shelf-break in colder, mixed water masses. Intraspecific diversity and interspecific genetic differentiation of the two putative species, and their phylogenetic relationships to several Crossaster congeners worldwide, were explored using mitochondrial and nuclear DNA sequences. The molecular evidence suggests that C. papposus is the more diverse and geographically structured taxon, in line with its wide distribution. C. papposus and C. squamatus are closely related, yet clearly distinct taxa, while C. papposus and C. multispinus H.L. Clark, 1916, the latter from the South Pacific Ocean, are closely related, possibly sister taxa.

Does harvesting affect the relative growth in Patella aspera Röding, 1798?

Length–weight relationships (LWRs) provide valuable information about growth and individual fitness on the population. LWRs are commonly used in studies on life history, population dynamics, ecosystem modelling and stock assessment. A comparative study on the effect of harvesting in the relative growth of Patella aspera between Marine Protected Areas (MPAs) and exploited areas was conducted in the archipelago of Madeira (NE Atlantic Ocean). The results showed that populations from the exploited areas exhibited a negative allometric growth whilst the populations from the MPAs showed predominantly isometric and positive allometric growth. The effects of protection from MPAs on the populations of P. aspera were not only restricted to an increase in mean size but also in a more balanced growth. This study highlight the importance of MPAs in the preservation of P. aspera populations in Madeira archipelago. Hence, these results should be used to corroborate the positive effects of MPAs in safeguarding the exploited resources, especially in oceanic islands were species are more prone to over-exploitation.

Multi-Proxy Approach for Identifying Heinrich Events in Sediment Cores from Hatton Bank (NE Atlantic Ocean)

A series of six gravity cores has been used to reconstruct the depositional history of Hatton Bank (Rockall Plateau, NE Atlantic Ocean). The cores have been studied for magnetic susceptibility (MS), geochemical composition, grain size distribution, and a semi-quantitative foraminiferal association. Two main interbedded facies have been described: (i) calcareous ooze; and (ii) lithogenous silt. The study reveals prominent peaks from the MS signal, silt, Mg/Ca, Fe/Ca, Al/Ca, and Rare Earth Elements normalised by Continental Crust (REE/CC), which are sensitive indicators for Heinrich events (H1, H2, H3, H4, and H5) and ash layers. These peaks may relate to alternations in dominance of the calcareous and lithogenic facies. The sediment displays a high percentage of carbonate in interglacial layers but is lithogenic-dominated in glacial stages. The layers with prominent lithic-rich and foraminifera-poor sediments (established as Heinrich layers) may be related to a possible palaeoclimatic effect, where freshwater discharged during iceberg melting may have reduced the formation of North Atlantic Deep Water (NADW). In the study area, the mean sedimentation rates for the last glacial as ~4.2 cm ka−1 and ~1.4 cm ka−1 for the last ~18 ka (interglacial period) have been estimated. Besides this evidence, Fe/Ca and MS peaks may reflect the presence of basalt, either introduced through ice-rafting or transported and redistributed by bottom currents in the study area. Certain indices, including MS and Fe/Ca, are proposed as good proxies for detecting Heinrich events and ash layers in the Hatton Bank sediments and, in consequence, are parameters that can be used to infer strengthened/weakened NADW formation, according to stadials/interstadials. Moreover, we suggest that the northernmost boundary of the area with evidence of Heinrich events may be situated around 57°38′ N in the Hatton–Rockall area, at least for H4, based on the variation of the Mg/Ca and Fe/Ca curves.

Coolia guanchica sp. nov. (Dinophyceae) a new epibenthic dinoflagellate from the Canary Islands (NE Atlantic Ocean)

ABSTRACT A new warm-water benthic dinoflagellate species, Coolia guanchica sp. nov., is described from the Canary Islands (NE Atlantic Ocean), a subtropical archipelago with a rich benthic biodiversity. Samples of benthic microalgae were collected at Tenerife, and three strains of a previously unreported ribotype of the genus Coolia were found. Identification was carried out by combining morphological (light microscope, LM; and scanning electron microscope, SEM) and molecular (large subunit ribosomal gene, LSU rRNA; and internal transcribed spacer region, ITS1-5.8S-ITS2 rRNA) data from clonal cultures. Phylogenetic analyses revealed that the new strains formed a well-supported clade, sister to Coolia canariensis. The genetic distance of more than 0.20 for LSU and 0.30 for the ITS region (uncorrected p values) from the closest members of the genus (C. canariensis and C. cf. canariensis) showed species-level divergence to justify the description of a new species, Coolia guanchica sp. nov. A bioassay with Artemia salina was used to check the toxicity of the species, with negative results. Coolia guanchica has rounded cells, with plate 4′ as the largest plate of the epitheca and plate 6′′ about twice as wide as long, similar to C. canariensis and C. areolata. It differs morphologically from the other two ribotypes in the C. canariensis complex in having a lighter hypothecal ornamentation, larger thecal plate pores scattered randomly throughout the cell and higher pore density per thecal plate.