Benthic foraminifera associated with a hydrocarbon seep in the Rockall Trough (NE Atlantic)

Recent benthic foraminiferal assemblages in surface sediments of the Rockall Trough (NE Atlantic) have been qualitatively and quantitatively studied in order to investigate the effects of hydrocarbon seepage on benthic foraminiferal populations. Species diversity and abundance data have been examined in samples of similar lithology collected from hydrocarbon seep and non-seep (control) areas at a water depth of about 1000 m. Three species groups with different environmental preferences can be recognized. Group 1 dominates seep samples, and includes species tolerant to hydrocarbon emission, especially Angulogerina bradyana. In contrast, the less tolerant Group 2 species are weakly represented at seeps but dominate control samples. Group 3 species occur in low frequencies in both seep and non-seep samples. Furthermore, the measurement of species diversity (Shannon-Wiener and Simpson indices) demonstrates a difference in foraminiferal occurrence and frequencies between the seep and non-seep sites. Thus, the benthic foraminiferal distribution pattern is guided by different sensitivities of the species to hydrocarbons, reduced bottom-water oxygen usually associated with seepage and/or to a relatively elevated organic matter content in the sediment.     

The predation of mysids by fish of the Rockall Trough,northeastern Atlantic Ocean

The stomach contents of representatives of approximately 100 species of pelagic and demersal fish caught in the Rockall Trough, northeastern Atlantic ocean, have been examined for the occurrence of mysids. More than 40 species of fish included mysids in their diets. The majority of the 21 species of mysids identified in the stomachs live in close association with the sediment and are rarely caught in pelagic nets. Mysids contributed significantly to the diets of many demersal fish but were not apparently important constituents of the food of pelagic fish.     

From sediment to rock: diagenetic processes of hardground formation in deep-water carbonate mounds of the NE Atlantic

Modern cool-water carbonate mounds topped by corals form an extended reef belt along the NW European continental margin at 200–1200 m water depth. An essential element of mound growth are hardgrounds which provide a stable substratum for mound-building invertebrate colonisation and stabilise the inclined mound flanks. Evaluating the degree of lithification and the slope stability against erosion represents an important task within the ESF programme MOUNDFORCE under the umbrella of EUROMARGINS. Sampling of hardgrounds during RV Meteor cruises M61-1 and -3 in 2004 by means of the IFM-GEOMAR TV-grab and the Bremen ROV QUEST focused on carbonate mounds of the Porcupine Seabight and northwestern Rockall Bank off Ireland. Lithified carbonates of mid-Pleistocene age were exhumed during the Holocene and are now exposed on the top and flanks of numerous carbonate mounds showing a patchy to dense colonisation by living corals and associated invertebrates. The sediments, composed of foraminiferal–nannoplankton oozes and admixed mound-derived invertebrate skeletons, range from partly lithified chalks to dense micritic limestones. These wackestones to packstones clearly differ from bacterially induced authigenic carbonate crusts typical of hydrocarbon seep settings by showing current-induced sedimentary structures, a non-luminescing matrix indicating oxic pore fluids, and a marine isotopic signature lacking any depleted carbon regime which is typical of anaerobic methane oxidation. The carbonate lithification is driven by carbonate ion diffusion from supersaturated seawater into the pore fluids in the studied areas. Vigorous bottom currents were the ultimate control not only of carbonate cementation by enhancing the diffusion process and supporting a pumping mechanism, but also of hardground formation and mound shaping by exhuming lithified carbonates and preventing fine-grained sediment accumulation at the downslope mound flanks.     

Diversity and abundance of sponges in bathyal coral reefs of Rockall Bank, NE Atlantic, from boxcore samples

Recent (2004) boxcoring on the SW Rockall Bank, west of Ireland (approx. 55°N 15°W, depths between 557 and 1407 m) yielded 95 species of sponges in 20 boxcore attempts. There are no published reports of Rockall Bank coral reef sponge fauna, but comparison with trawl and dredge efforts in neighbouring parts of the NE Atlantic (east of Rockall Trench, off the Scottish coasts) made in the late 19th and early 20th century leads to the conclusion that our boxcoring efforts yielded similar numbers of species as these more elaborate collecting programs. Numbers of specimens for all boxcore samples combined was 466, together occupying a total volume of approx. 3.38 l, based on length x width x height measurements of all individuals. These results indicate a generally low biomass of sponges contributing to the deep water coral reef fauna. Species composition in this bathyal habitat shows a high heterogeneity (Eveness J': 0.81-0.97) and the majority of sponge individuals does not exceed 1 cm³ in volume. Nevertheless, high densities of a large hexactinellid species, Asconema aff. setubalense (up to 30 cm in height), were encountered locally. Sponge community analysis showed that there was no clear correlation between coral cover and sponge diversity, and only a weak correlation between coral cover and abundance and volume of sponges. This, combined with the overall very small size of the sponges, suggests that substratum is not a limiting factor for their occurrence.     

Photoacclimation and photoregulation strategies of Corallina (Corallinales,Rhodophyta) across the NE Atlantic

This study characterizes the photoacclimation and photoregulation mechanisms that allow calcified macroalgae of the genus Corallina (Corallinales, Rhodophyta) to dominate rock pool habitats across the NE Atlantic despite the highly variable irradiance regimes experienced. Rapid light curves (RLCs) were performed with pulse amplitude modulation (PAM) fluorometry in situ across a full seasonal cycle in the UK intertidal with C. officinalis and C. caespitosa. Latitudinal comparisons were performed across the full extent of C. officinalis’ range in the NE Atlantic (Iceland–northern Spain), and for C. caespitosa in northern Spain. Ex situ RLCs with dark recovery were further employed to assess the optimal, as compared with actual, photophysiology across seasons and latitudes. Corallina species were shown to photoacclimate at seasonal timescales to changing irradiance, increasing light-harvesting during low-light autumn/winter periods and protecting photosystems during high-light summer conditions. Seasonal photoacclimation was achieved through alteration in the number of photosystem (PS) units (PSII and light harvesting antennae) over time. Non-photochemical quenching (NPQ) served as an important photoregulation mechanism utilized by Corallina to prevent or minimize photoinhibition over shorter time scales (seconds–hours), though the efficiency of NPQ was dependent on the seasonal-acclimated state. With increasing latitude the efficiency of photoregulation decreased, representing potential differential photoadaptation of Corallina across species ranges in the NE Atlantic. In contrast, highly conserved inter-specific patterns in photophysiological responses to irradiance were apparent. This study demonstrates the photophysiological mechanisms allowing Corallina to optimize use of the variable irradiance conditions apparent in rock pool environments, when and how they are employed, and their limitations.     

Characterization of 13 microsatellite loci for the deep-sea coral, Lophelia pertusa (Linnaeus 1758), from the western North Atlantic Ocean and Gulf of Mexico

A suite of 13 polymorphic tri- and tetranucleotide microsatellite loci were isolated from the ahermatypic deep-sea coral, Lophelia pertusa. Among 51 individuals collected from three disjunct oceanic regions, allelic diversity ranged from six to 38 alleles and averaged 9.1 alleles per locus. Observed heterozygosity ranged from 9.1 to 96.8% and averaged 62.3% in the Gulf of Mexico population. For some loci, amplification success varied among collections, suggesting regional variation in priming site sequences. Four loci showed departures from Hardy-Weinberg equilibrium in certain collections which may reflect nonrandom mating.     

Systematics,palaeoecology and palaeobiogeography of the Neogene fossil sharks from the Azores (Northeast Atlantic)

The Azores Archipelago is a group of isolated islands located in the North Atlantic Ocean. One of these oceanic islands – Santa Maria – exhibits marine fossiliferous sediments of late Miocene/early Pliocene and also of Pleistocene age. Recent research provided new selachian fossil material, with three new records (Carcharias acutissima, Megaselachus megalodon, and Carcharhinus cf. leucas) increasing the number of fossil sharks reported from the Azores (Santa Maria Island) to seven species (Notorynchus primigenius, C. acutissima, Cosmopolitodus hastalis, Paratodus benedenii, Isurus oxyrinchus, M. megalodon, and C. cf. leucas). So far, no teeth of batoids or small sharks have been found despite the screen-washing of several sediment samples from Santa Maria. The Azorean Mio-Pliocene selachian fauna clearly differs from those described from sediments deposited on continental shelves, in which batoids and small benthic sharks (e.g., scyliorhinids) are usually well represented. During the late Miocene/early Pliocene, subtropical to warm-temperate seas were prevalent in the area of the Azores, as deduced from palaeontological, geological and isotopic data, all indicating a warmer climate than in the present.     

Length-weight relationships of seven fish species from tidepools of an intertidal rocky shore in the Gulf of Cadiz,Spain (NE Atlantic)

Length-weight relationships for seven fish species caught from tidepools in an intertidal rocky shore in the Gulf of Cadiz are presented. Fish were sampled monthly (April 2008–January 2012), using hand nets (mesh size 1.5 mm). The values of b parameter remained within the expected range of 2.5–3.5 for all fish species. An ANCOVA test was used to evaluate differences in the b growth parameter between females and males. Gobius cobitis, G. incognitus and G. paganellus showed significant differences in the parameters of the length-weight relationships according to the sex.     

Blastodinium galatheanum sp. nov. (Dinophyceae) a parasite of the planktonic copepod Acartia negligens (Crustacea,Calanoida) in the central Atlantic Ocean

A new dinoflagellate species, Blastodinium galatheanum sp. nov., was found parasitizing the planktonic copepods Acartia negligens and Acartia sp. in the Atlantic Ocean between the Azores and the Cape Verde Islands. These copepods have not previously been reported hosting a Blastodinium species. Characters that distinguish the new species are the shape and size of the trophic stage, its host species, and its predominantly solitary existence. Dinospores of Blastodinium galatheanum sp. nov. are peridinioid in nature and morphologically indistinguishable from dinospores of two other previously investigated Blastodinium species. SSU rRNA gene sequences from two isolates of this new species were almost identical and showed similarities to SSU rRNA sequences of other species of Blastodinium. A phylogenetic analysis based on SSU rRNA gene sequences suggested monophyly for all existing sequences of Blastodinium spp., including a sequence from the type species B. pruvoti, presented here for the first time.     

Allozyme differentiation within and between red drum (Sciaenops ocellatus) from the Gulf of Mexico and Atlantic Ocean

Nine polymorphic nuclear-gene (allozyme) loci were surveyed among 491 red drum ( Sciaenops ocellatus ) sampled in 1988 and 1989 from nearshore localities in the northern Gulf of Mexico (Gulf) and the Atlantic coast of the southeastern United States (Atlantic). Data were combined with those from a previous study to generate a data set of 762 individuals representing 11 sample localities in the Gulf and 175 individuals representing five sample localities in the Atlantic. The combined data set included individuals from the 1986 and 1987 year classes and permitted rigorous testing of both temporal and spatial genetic heterogeneity. Average heterozygosity-per-locus values (estimated using 33 assumed monomorphic loci) were 0·048 (Gulf red drum) and 0·046 (Atlantic red drum). Tests of heterogeneity in allele frequencies between year classes at individual localities and across regions (Gulf and Atlantic) were non-significant. Tests of spatial (geographic) heterogeneity indicated that red drum are weakly subdivided: genetically-differentiated subpopulations occur in the northern Gulf and along the south-eastern Atlantic coast. Genetic data were consistent with the hypothesis that red drum within the Gulf and along the Atlantic coast comprise singie subpopulalions. Genetic differences between Gulf and Atlantic red drum seem likeiy to stem from historical or recent interactions between dispersal and impediments to gene flow.     

Two new Cocconeis taxa (Bacillariophyceae) from coral sands off the Mascarenes (Western Indian Ocean) and some related unidentified taxa

Coral sands off Réunion Island and Rodrigues (Mascarene archipelago, Western Indian Ocean) support diverse diatom communities, particularly rich in Monoraphidineae. Recent surveys of reef environments (June 2005 and June 2007) permitted the recognition of several taxa belonging to the diatom genus Cocconeis, among which are two new, relatively small taxa, epipsammic on coral sand. Cocconeis coronata Riaux-Gobin et Romero sp. nov. is similar to C. scutellum but has its own distinctive features. In external view, the concave raphe valve possesses uniseriate striae and a subsident hyaline marginal rim, while the strongly convex sternum valve has a submarginal, generally continuous crest, a hexagonal pattern of areolation, short, rounded spines that are often regularly arranged around valve face areolae, a complex areola hymen and small marginal chambers. Some morphometric differences were noted between the populations of C. coronata at Réunion and Rodrigues. Cocconeis margaritata Riaux-Gobin et Al-Handal, sp. nov. is smaller, possesses a sternum valve like that of C. placentula and C. neothumensis, but has denser striation and small pearl-like concretions around the areola aperture on the sternum valve. Several other taxa that resemble, or may be varieties of, C. margaritata require further study before being formally described. Cocconeis margaritata and C. coronata are small and relatively rare, so their study requires scanning electron microscopy.     

Biogeographical distribution of Hartaetosiga strains (Choanoflagellatea,Craspedida, Salpingoecidae) including morphological and transcriptomic data from a transect across the Atlantic Ocean

The genus Hartaetosiga Carr, Richter and Nitsche, 2017 comprised up to now only three species, H. gracilis (Kent) Carr, Richter, Nitsche, 2017, H. balthica (Wylezich and Karpov) Carr, Richter and Nitsche, 2017 and H. minima (Wylezich and Karpov) Carr, Richter and Nitsche, 2017. Based on distinct molecular data these species were relocated from the strictly freshwater genus Codosiga (Ehrenberg) Bütschli, 1878 to a new genus comprising brackish and marine species. During the cruise MSM82/2 across the Atlantic Ocean in 2019, surface water samples were taken from 15 stations along a transect ranging from 35°S to 23°N. We were able to isolate and cultivate 14 strains of the genus Hartaetosiga. Morphometric data showed no distinct morphological traits allowing for a species delineation, indicating a cryptic species complex within the genus. Based on cultivation, morphological data, and molecular analyses, we recorded H. gracilis for the first time from off-shelf waters of the Atlantic Ocean and could describe a new species, H. australis n. sp. This new species was recorded from sampling stations in the Southern Hemisphere only, which may indicate a potential biogeographic restriction likely caused by the Equatorial Counter Current (ECC), dividing the northern and southern surface waters.     

Paleoecological significance of laminated diatomaceous oozes during the middle-to-late Pleistocene,North Atlantic Ocean (IODP Site U1304)

We examined diatom assemblages in a series of remarkable laminated diatomaceous ooze (LDO) horizons in the marine sediments from Integrated Ocean Drilling Program (IODP) Site U1304 to reconstruct the middle-to-late Pleistocene paleoceanographic evolution of the northern North Atlantic Ocean. Four confirmed diatom biohorizons combined with calcareous nannofossil and paleomagnetic stratigraphies established the chronological framework for the material. The planktonic, araphid, needle-like species Thalassiothrix longissima was the greatest contributor to the LDO facies. From the results of a principal component analysis using the percent abundances of 65 significant (p = 5%) diatom taxa, except for Tx. longissima, which was extremely dominant in almost all horizons observed, we identified two principal component (PC) axes. Taxa probably associated with the stratigraphic distribution of the major zonal marker Neodenticula seminae (ranging from 1.26 to 0.84 Ma in this ocean) loaded on PC1 with a high value. PC2 was related to the ocean surface temperature. The stratigraphic variability of the PC2 score indicated that switching between warm- and cold-water assemblages occurred concurrently with LDO deposition (or extreme Tx. longissima dominance) episodes in several horizons (particularly after 0.84 Ma), suggesting that the Subarctic Convergence (SAC) oceanic front passed over Site U1304 during Pleistocene glacial/interglacial cycles. Our floral evidence supports the model of nearly monospecific LDO formation caused by the enhanced physical accumulation of particular diatoms such as Tx. longissima. On the other hand, Nd. seminae, which probably contributes to spring phytoplankton blooms in the modern ocean, was present only between 1.26 and 0.84 Ma in this area. Thus, we infer that the main contributor of export flux in the regional annual primary production cycle would have shifted drastically from one of a spring phytoplankton bloom leader (Nd. seminae) to minor but mass dump assemblages (Tx. longissima etc.) in the mid-Pleistocene.     

Diversity of isopods (Crustacea): new data from the Arctic and Atlantic Oceans

New data on the diversity pattern of isopods (Crustacea) from the northern most part of the North Atlantic and the Arctic Oceans is presented. The pattern of diversity with depth is similar at depths <1000m, but differs considerably below about 1000m. In the Arctic the diversity of isopods (expressed both as numbers of species per sled and expected number of species) increased with increased depth to a maximum at depths of about 320 to 1100m, but then declined towards deeper waters. There was a significant increase in numbers per sled and in the expected number of species with increased depth in the northernmost part of the North Atlantic Ocean. Additionally, changes occurred in the relative composition of the shallow and deep water fauna, with asellote isopods being relatively larger part of the isopod fauna in the Arctic than in the northern most part of the North Atlantic. This indicates major faunistic changes occurring at the Greenland-Iceland-Faeroe Ridge, possibly caused by rapid changes in the temperature. Furthermore, that the low diversity of the Arctic deep-sea is a regional phenomenon, and not a part of a large scale latitudinal pattern in the North Atlantic.     

Leptonotus vincentae,a new pipefish species (Syngnathidae: Syngnathinae) from the south-west Atlantic Ocean near northern Patagonia

A new species of pipefish Leptonotus vincentae sp. nov. (Syngnathidae) is described on the basis of 12 specimens found in shallow waters (<2 m depth) of San Antonio Bay, Patagonia, Argentina, in the south-west Atlantic Ocean. The species is distinguished from congeners by the combination of: dorsal-fin rays 30–33, pectoral-fin rays 12–13, trunk rings 18–19, tail rings 43–46, subdorsal rings (2–4) + (5.5–8) = (8.5–10), head length 13–14% standard length, snout length 35–55% head length and snout depth 21–30% in snout length. Although this species has often been mistaken for Leptonotus blainvilleanus, most diagnostic characters of the two species differ. Both species are clearly distinguished by their snout length. L. blainvilleanus has a relatively longer snout than L. vincentae sp. nov. The new species is similar to a south-west Pacific species, Leptonotus elevatus. However, L. vincentae sp. nov. differs from this species in that it exhibits a lower number of dorsal-fin rays and a relatively longer head.     

Miocene diatom biostratigraphy at ODP Sites 689, 690, 1088, 1092 (Atlantic sector of the Southern Ocean)

Four ODP sites located between 64°S and 41°S in the eastern Atlantic sector of the Southern Ocean were investigated to refine the Miocene diatom biostratigraphic zonation tied to the geomagnetic chronology. The Miocene diatom stratigraphy from two sites located on Maud Rise (ODP Leg 113) is revised considering the progress in diatom biostratigraphic research, diatom taxonomy and magnetostratigraphic age assignment during the past 10 years. A new diatom zonation was erected for Site 1092 (ODP Leg 177) located on Meteor Rise integrating a magnetostratigraphic interpretation of the shipboard data. This zonation was also applied to Site 1088 (ODP Leg 177) located on Astrid Ridge. The study is focused to Middle and Upper Miocene sequences. It reveals latitudinal differentiations in stratigraphic species ranges and species occurrence pattern that are related to latitudinal differences in surface water masses reflecting the climatic development of the Antarctic cryosphere. Considering the latitudinal differences two stratigraphic zonations are proposed that are applicable to the northern and southern zone of the Southern Ocean, respectively. The southern Southern Ocean Miocene diatom biostratigraphic zonation consists of 16 zones in which 11 represent new or modified zones. The northern biostratigraphic zonation contains 10 diatom zones allowing a stratigraphic resolution in the range of 0.2–2 Myr. This paper also includes the taxonomic transfer of seven Miocene diatom taxa from genus Nitzschia Hassal to Fragilariopsis Hustedt.     

The Association of Two Gall Crabs (Brachyura: Cryptochiridae) with the Reef-building Coral Siderastrea stellata Verrill, 1868

The family Cryptochiridae includes a small group of cryptic crabs that inhabit cavities in scleractinian corals. They are represented in Brazil by two species. Troglocarcinus corallicola, found from Maranhão to Bahia states and that occurs in many species of the coral families Mussidae, Faviidae, Caryophillidae and Siderastreidae. Opecarcinus hypostegus, reported from the state of Pernambuco, is mainly associated with Agaricia fragilis. The range of O. hypostegus is extended to Rio Grande do Norte and Alagoas states. Males are usually smaller than females, and couples may be eventually found sharing cavities. Ovigerous females and males of O. hypostegus are recorded for the first time inhabiting adjoining cavities on colonies of Siderastrea stellata, an endemic reef coral widespread along the Brazilian littoral.