Eastern Atlantic Waters Research Articles

Caligus madeirensis sp. nov. (Copepoda: Caligidae) Parasitic on Pompano, Trachinotus ovatus (Linnaeus, 1758), from Eastern Atlantic Waters, Surrounding the Madeira Archipelago, Portugal

IntroductionA new species of the genus Caligus is described based on specimens collected from pompano, Trachinotus ovatus (Linnaeus), caught in eastern Atlantic waters, near the Madeira archipelago.MethodsPompano (n = 21) were purchased from the local fish market and examined for parasitic copepods. Morphological features of the copepods were examined and drawn using an Olympus BX51 equipped with a drawing tube. Key diagnostic characters were scanned using a confocal laser scanning microscope and a scanning electron microscope.ResultsCaligus madeirensis sp. nov., can be distinguished from all congeners (270 spp.) by the combination of the following characters: (i) an accessory process on the 3 outer terminal spines located on the distal exopodal segment of leg 1, (ii) a mandible with 14 teeth, (iii) a sternal furca with parallel, spatulate tines, (iv) a maxilliped with 2 simple setae at base of a claw, (v) a leg 3 with second endopodal segment with 5 pinnate setae, (vi) a 2-segmented leg 4 exopod with I; III spine formula, (vii) a male antenna with 4 overlapping plates on the distal segment, (viii) a male maxilliped corpus bearing a prominent myxal process ornamented with dense corrugations along inner margin.ConclusionTogether with Caligus madeirensis sp. nov., the Caligus fauna of Portugal consists of 13 species reported from 17 Portuguese marine fishes. Considering the large number of marine fish species (510 spp.) currently recorded from Portuguese waters it seems that only 3.3% of the Portuguese marine fishes have been found to be infested with species of the genus Caligus O.F. Müller, 1758, the result of which, however, might be due to limited sampling.Electronic supplementary materialThe online version of this article (10.1007/s11686-020-00290-3) contains supplementary material, which is available to authorized users.

Deep phylogeographic structure may indicate cryptic species within the Sparid genus Spondyliosoma.

Two geographically nonoverlapping species are currently described within the sparid genus Spondyliosoma: Spondyliosoma cantharus (Black Seabream) occurring across Mediterranean and eastern Atlantic waters from NW Europe to Angola and S. emarginatum (Steentjie) considered endemic to southern Africa. To address prominent knowledge gaps this study investigated range-wide phylogeographic structure across both species. Mitochondrial DNA sequences revealed deep phylogeographic structuring with four regionally partitioned reciprocally monophyletic clades, a Mediterranean clade and three more closely related Atlantic clades [NE Atlantic, Angola and South Africa (corresponding to S. emarginatum)]. Divergence and distribution of the lineages reflects survival in, and expansion from, disjunct glacial refuge areas. Cytonuclear differentiation of S. emarginatum supports its validity as a distinct species endemic to South African waters. However, the results also indicate that S. cantharus may be a cryptic species complex wherein the various regional lineages represent established/incipient species. A robust multilocus genetic assessment combining morphological data and detailing interactions among lineages is needed to determine the full diversity within Spondyliosoma and the most adequate biological and taxonomic status.

The unknown bathyal of the Canaries: new species and new records of deep-sea Mollusca

A set of seven dredge hauls, between 195-215 m and 655-660 m deep on the NW slope of Gran Canaria (Canary Islands, Spain), recovered 15 000 specimens belonging to 295 species of molluscs. Of these, 254 are identified at the species level. Only 47 species, totalling 867 specimens, were live collected, which amounts to 84% of the species and 94% of the specimens represented only by shells. The dredges DW 133 (shallowest) and DW 130 (deepest) hold the highest number of species and abundance, representing about 90% of the material. Fifty-one species are new records for Canarian waters; of these, 23 are new for Spanish waters overall and three are the first reference in eastern Atlantic waters. Another 13 species, in the genera MikroWaren, 1996, DiscaclisMoolenbeek & Waren, 1987, Mucronalia A. Adams, 1860, Marginella Lamarck, 1799, Dentimargo Cossmann, 1899, Prunum Herrmannsen, 1852, Microvoluta Angas, 1877, Spirotropis G.O. Sars, 1878, Gymnobela Verrill, 1884, Mitromorpha Carpenter, 1865, Orbitestella Iredale, 1917 and Liostomia G.O. Sars, 1878, are described as new, most of them from the deepest haul at 655-660 m. Anatoma richardi (Dautzenberg & Fischer, 1896) is restored as valid species and the identification of Canarian specimens as Anatoma tenuis (Jeffreys, 1877) is disputed. Ancistrobasis lavaleyeiHoffman & Freiwald, 2017 is synonymized with A. reticulata (Philippi, 1844). Pleurotomella megalembryon (Dautzenberg & Fischer, 1896), type species of Azorilla Nordsieck, 1968, is assigned to Teretia Norman, 1888; Teretia strongyla (Dall, 1927) is synonymized with T. megalembryon, and Azorilla with Teretia. Pleurotoma teres Reeve, 1844 is selected under ICZN Art. 70.3.2 as type species of Teres Bucquoy, Dautzenberg & Dollfus 1883 and of its substitute name Teretia, discarding therefore Pleurotoma anceps Eichwald, 1830.

Global oceanic wind speed trends

This study presents the regional and seasonal climatic trends of the global oceanic sea surface wind speed for the period 1988–2011 using Cross-Calibrated, Multi-Platform (CCMP) wind data. The relationship between important factors (nino3 and soi index) and occurrences of wind speed is also calculated, in hope of providing references for the analysis of global climate change, development of offshore wind energy resources, air–sea interactions, and the basic reference helping for the mid-long term prediction of sea surface wind speed and occurrences of wind speed. The analysis results show that (1) The global oceanic sea-surface wind speeds increased at a significant overall rate of 3.35 cm s−1 yr−1 for the period 1988–2011; the maximal rate of increase, 4.15 cm s−1 yr−1, was attained between 1991 and 2007. (2) Globally, the sea-surface wind speeds significantly increased from 1988 to 2011. Only a few sporadic small water bodies exhibited decreasing wind speeds without significant variation over the 24-year interval. (3) The sea-surface wind speeds displayed obvious regional variability. The increasing wind speeds were more noticeable over the Pacific low-latitude waters than over waters of higher latitude. Wind speeds trends over the western Atlantic waters were stronger than those over the eastern Atlantic waters, while the south Indian Ocean winds were stronger than that those over the north Indian Ocean. (4) The variation in sea-surface wind speeds demonstrated noticeable seasonal differences. The increasing wind speed trend over the winter hemisphere was stronger than the one over the summer hemisphere. The variation in wind speeds over different waters was seasonally dominated. The increasing trend over the coastal waters of southern Greenland was dominated by the MAM and SON, was dominated by DJF in the Davis Strait and the Mediterranean, and was dominated by the SON 10° N over the Pacific Ocean and over the high-latitude waters in the southern Indian Ocean.

Assessing Octopus vulgaris distribution using presence-only model methods

The distribution of the common octopus (Octopus vulgaris) in the Mediterranean and Eastern Atlantic waters is evaluated using two presence-only analyses: The maximum entropy model (Maxent) and the ecological niche factor analysis (ENFA). Maxent predicts those geographical areas that satisfy the environmental or abiotic requirements of a species while ENFA explores the niche and habitat preferences of O. vulgaris. The analyses were implemented recovering the spatial information from 213 octopus presence data collected from surveys and bibliographical records. Together, these analyses provided reasonable estimates of the species distribution and the octopus habitat. Among the gathered set of explanatory environmental variables, sea bottom temperature, sea bottom salinity, surface dissolved oxygen and sea surface chlorophyll-α appear as the main variables involved in O. vulgaris distribution. These results were confronted with the available literature.

First record of Polymixia nobilis (Polymixiformes: Polymixiidae) close to the Strait of Gibraltar (south-western Spain)

The capture of a specimen of Polymixia nobilis , a rare species in the eastern Atlantic waters north of the Canary and Madeira Islands, is reported as the first record in the vicinity of the Strait of Gibraltar.

HATCHING TIMES, LARVAL DURATION, SETTLEMENT AND LARVAL GROWTH OF PLAICE (PLEURONECTES PLATESSA (L.)) IN GALWAY BAY DETERMINED USING OTOLITH MICROSTRUCTURE

The otolith microstructure of juvenile plaice from two beaches in Galway Bay on the Irish west coast, Ballyloughaun and Silverstrand, was examined. Sampling was carried out monthly in the spring of 2003. The hatch date, larval duration, settlement date and larval growth rates were determined for 85 fish. Hatching occurred from late January to late March. The mean larval duration was 33 days, and fish settling earlier in the year had a longer larval life on Silverstrand. Settlement occurred between early March and late April. Settlement pulses closely corresponded to hatching times, indicating that hatching/settlement cohorts could exist for plaice in Galway Bay. Larval growth was consistent between locations assessed. There was a positive relationship between larval growth and hatch date, and an inverse relationship was noted between larval growth and larval duration. Results from this study were compared to studies from other European areas, and a relationship between larval duration and temperature was noted, with fish from cooler areas in Europe having longer larval durations. This is the first study of its kind on the west coast of Ireland and the first study within eastern Atlantic waters to focus on the early life history of plaice.

HATCHING TIMES, LARVAL DURATION, SETTLEMENT AND LARVAL GROWTH OF PLAICE (<i>PLEURONECTES PLATESSA</i> (L.)) IN GALWAY BAY DETERMINED USING OTOLITH MICROSTRUCTURE

The otolith microstructure of juvenile plaice from two beaches in Galway Bay on the Irish west coast, Ballyloughaun and Silverstrand, was examined. Sampling was carried out monthly in the spring of 2003. The hatch date, larval duration, settlement date and larval growth rates were determined for 85 fish. Hatching occurred from late January to late March. The mean larval duration was 33 days, and fish settling earlier in the year had a longer larval life on Silverstrand. Settlement occurred between early March and late April. Settlement pulses closely corresponded to hatching times, indicating that hatching/settlement cohorts could exist for plaice in Galway Bay. Larval growth was consistent between locations assessed. There was a positive relationship between larval growth and hatch date, and an inverse relationship was noted between larval growth and larval duration. Results from this study were compared to studies from other European areas, and a relationship between larval duration and temperature was noted, with fish from cooler areas in Europe having longer larval durations. This is the first study of its kind on the west coast of Ireland and the first study within eastern Atlantic waters to focus on the early life history of plaice.

Total and organic Hg concentrations in cephalopods from the North Eastern Atlantic waters: Influence of geographical origin and feeding ecology

Total (T–Hg) and organic (O–Hg) mercury concentrations and tissue distribution were examined in 20 species of cephalopods (n=278) from the north eastern Atlantic waters, i.e. from the Bay of Biscay to the Faroe Islands. Concentrations of T–Hg in whole cephalopods showed elevated variations among species, i.e. from 40 to 3560ng g−1 dwt, but a low variability within each species (mean CV%=39%). With the exception of oceanic squids, the digestive gland globally displayed higher T–Hg concentrations than the remaining tissues. In contrast, O–Hg concentrations determined in selected species were generally higher in the remaining tissues. Despite higher T–Hg concentrations, the digestive gland weakly contributed to the total body burden of both T–Hg and O–Hg (<25% and <15%, respectively). In fact, from 75% to 95% of the T–Hg and O–Hg were contained in the muscular remaining tissues. Therefore, O–Hg may have a strong affinity to proteins in cephalopods. Sex and size only significantly influenced the bioaccumulation of Hg for the Loliginidae family. T–Hg and O–Hg concentrations were also influenced by geographical origin: Celtic Sea>Bay of Biscay>Faroe Islands, corresponding to the seawater Hg concentrations in these areas. In the Faroe Islands and the Celtic Sea, benthic cephalopods contained significant higher Hg concentrations compared to pelagic ones. This suggests that diet is not the main pathway of Hg uptake in cephalopods as pelagic species were expected to be more exposed to O–Hg through fish consumption than benthic ones.

The distribution and biochemical composition of biogenic particles across the subtropical Front in June 1993 (Azores-Madeira region, Northeast Atlantic)

Water samples were collected in the north-east Atlantic Ocean between the Azores and Madeira (33°N-36°N and 24°W-26°W) during the Oceanographic Cruise SEMAPHORE in June 1993. Temperature, salinity, nutrients (nitrate and phosphate) and particulate organic matter (organic carbon, organic nitrogen, carbohydrates, proteins and phytopigment) were investigated in the water column to a depth of 2000 m. The presence of the subtropical front (STF) separating warmer more saline Western Atlantic Water (WAW) from colder and fresher Eastern Atlantic Water (EAW) in the upper 100 m, and a tongue of salt water arising from the influence of Mediterranean Water (MW) at a depth of 1000 m, were well identified by the physical and chemical parameters. POC and PON concentrations, in the surface layer (0-100 m), ranged between 23.3-64.5 and 2.9-9.1 µg l-1 respectively, while concentration between 12.4-30.5 and 1.1-4.0 µg l-1 prevailed below the thermocline (100-2000 m). The very low POC and PON concentrations together with the low nutrient and chlorophyll-a concentrations confirmed the oligotrophic nature of the Azores-Madeira region. Statistical analysis was carried out to investigate the difference in the quantity and quality of POM between water masses. Regression analysis showed a high correlation between POC and PON but the slopes and intercepts of the regression lines did not differ significantly between WAW and EAW. In contrast, an examination of vertical profiles as well as mean integrated values of biochemical variables in the upper 100 m suggest a difference in the quantity and quality of biogenic particles between the water masses. WAW showed the lowest integrated concentrations of particulate organic carbon, particulate organic nitrogen, particulate protein and particulate carbohydrate. In contrast, frontal stations showed the highest values while EAW stations showed intermediate values. All these results, coupled with the occurrence of the highest POC:Chl-a ratio in EAW, suggest a temporal offset in the production cycle between the two water masses. Alternatively, the WAW is a more stratified and oligotrophic body of water than is EAW, and it always has lower biomass and nutrients than the more productive EAW. High chlorophyll-a concentrations were linked to the STF; moreover the average depth of the subsurface chlorophyll maximum (DCM) appeared to shift to shallower values at the frontal stations, suggesting a close association between the STF-Azores Current (AC) physical structure and the distribution of chlorophyll-a in this area.

Symphurus insularis: A New Eastern Atlantic Dwarf Tonguefish (Cynoglossidae: Pleuronectiformes)

Symphurus insularis, a dwarf species of tonguefish reaching sizes to about 80 mm SL, is described based on 39 specimens collected in shallow-water habitats (3–23 m) at Madeira, the Canary Islands, and São Miguel, Azores. The new species is distinguished from its congeners by the combination of a 1-3-2 ID pattern, 12 caudal fin rays, 80–87 dorsal fin rays, 66–72 anal fin rays, 45–48 total vertebrae, 84–98 scales in a longitudinal series, unpigmented peritoneum, and ocular surface pigmentation featuring a yellowish to dark-brown background with a series of 3–8 mostly incomplete crossbands and usually 1–3 small, dark, spherical spots arranged in a longitudinal row along the body midline, together with a series of dark blotches alternating with unpigmented areas on the dorsal and anal fins, and a spot and dark band on the caudal fin base with the distal four-fifths of the caudal fin unpigmented. Symphurus insularis most closely resembles S. reticulatus from St. Helena, S. rhytisma from the Caribbean Sea and northern Brazil, and S. lubbocki from Ascension Island. Symphurus insularis is the only species of dwarf tonguefish known from shallow-water habitats in the Macaronesian biogeographic subprovince of the eastern Atlantic. Previous reports of other species of symphurine tonguefishes from shallow-water habitats in these areas were based on misidentifications. A key to species of Symphurus occurring in middle and eastern Atlantic waters is provided.

Coupling between physical and biological fields in the North Atlantic subtropical front southeast of the Azores

The physical and biological properties of the North Atlantic subtropical region southeast of the Azores were studied during an oceanographic cruise carried out in March 1992. The main patterns of physical variability were defined by the presence of (a) a thermohaline front (subtropical front; STF) located at 34°N–35°N and extending from 15°W to 28°W, which separates warmer more saline Western Atlantic Water from colder and fresher Eastern Atlantic Water, and (b) a strong eastward flow running along the subtropical front (Azores Current; AC) extending down to at least 250 m and showing velocities of 50–70 cm s −1 at the core of the current. Overall a close linkage was observed between the STF-AC physical feature and high levels of chlorophyll a. A high resolution survey showed chlorophyll a fluorescence associated with the southern frontal boundary (consisting of chain forming diatoms and flagellates) and with the AC (made up of cells in the less than 2 μm size-class), respectively. Primary production rates measured in the frontal high-chlorophyll region (> 1 mg C m −3 h −1) were much higher than previous measurements carred out in the same area in late spring and summer and about 2 times higher than modelling estimates for the region. The large spatial extension of the biological signature associated with the STF-AC system suggests that carbon fixation within the frontal structure could be significant for regional carbon budgets of the subtropical northeast Atlantic.

Vertical profiles of pelagic communities in the vicinity of the Azores Front and their implications to deep ocean ecology

Three early wintertime and five early summertime stations were occupied in the vicinity of the Azores Front to the south-west of the islands. At each station the surface 1100–1400m of the water column were systematically sampled both by day and by night, using the Institute of Oceanographic Sciences' RMTI+8M system. The biological sampling was set in the context of an extensive study of the physical oceanography of the frontal region. It included one station in the core of an eddy which was seen to spawn from a meander during the course of the physical observations. The biological communities on either side of the front were almost indistinguishable in terms of their specific composition. However, there were substantial differences in the sizes of the standing-crops, the vertical distributions of the major taxonomic groups and the ranges of the diel vertical migrations being carried out by these groups. The waters on both sides of the front were oligotrophic. However, both phytoplankton standing-crop, as indicated by chlorophyll concentrations, and measures of productivity suggested that the water to the north (Eastern Atlantic Water), which was slightly cooler and with a shallower and steeper nutricline, was a little more productive than the water to the south (Western Atlantic Water). Associated with this trend in phytoplankton crop and productivity were quite sharp declines in the standing-crops of both plankton and micronekton across the front, moving from EAW to WAW. There was no evidence of enhanced productivity within the front itself, but there was an increase in the micronektonic standing-crop. Between the stations, there were consistent trends in the ratios of the standing-crops of plankton and micronekton, which were sampled simultaneously. By day, the planktonic biomasses exceeded the micronektonic biomasses by up to an order of magnitude in the wind-mixed layer. The ratios declined with depth, approaching unity at 200m during the wintertime, but remaining quite high to depths of 800m during the summer. At night, the ratios tended to be lower as a result of diel vertical migration, but except in one or two of the deepest samples the planktonic biomass always exceeded that of the micronekton. The total biomass profiles were very similar in shape between the stations, although there were quite large differences in the depths of the quartiles. There were substantial differences between the day and the night profiles. These could be attributed mostly to the effects of diel vertical migrations, but must also have included unquantifiable effects as a result of variations in net avoidance. The subdivision of the catches into the major taxonomic groups showed that the degree of avoidance varied substantially between them; euphausiids were the most effective daytime avoiders, but decapod crustaceans and fish showed a suprisingly small tendency to avoid. The ranges and the numbers of each group undertaking vertical migrations varied markedly between the stations, and these differences were expressed in the biomass estimates. Attempts have been made to quantify the movement of biomass in and out of the surface 200m and 500m resulting from these migrations. There were substantial changes in migratory behaviour across the front, even though there were no detectable changes in the light profiles. The data also imply that the micronektonic migrants play an important role in the active transport of organic substances down from the euphotic zone to mesopelagic depths (>500m), either in their gut contents or directly as a result of predation at depth. In addition, migrating plankton seem likely to be important in redistributing nutrients about the nutricline in these oligotrophic regions where the water column stability limits physical vertical mixing processes. Preliminary estimates suggest that their influence may be sufficiently large to alter the ratio between “new” and “old” production.

Sea surface temperature mapping flights—Norwegian sea, summer 1968

Sea surface temperature mapping flights were carried out with Naval Oceanographic Office research aircraft from April 1968 through September 1968. These flights, carried out in the interest of the Icelandic herring fishery, defined the boundary between the tongue of polar water projecting southward to the east of Iceland and the warmer eastern Atlantic water mass. Examination of historic bathy-thermograph data for the Norwegian Sea demonstrates the potential of defining water-mass boundaries on the basis of airborne radiation thermometer (ART) measurements. Surface thermal structure patterns were delineated by contouring 1-minute ART average temperatures. The aircraft position was fixed at 10-minute intervals using Loran A and altitude determined by pressure altimeter. Accurate horizontal position data are required for definition of the water-mass boundary for subsequent positioning of the fishing fleet. Accurate altitude data, together with flight level air temperature, humidity, and sea surface temperature, are required for environmental correction of the apparent ART temperature as a result of atmospheric absorption and reradiation of the radiant energy emitted by the sea surface.