Evidence of Halodule wrightii flower and seed production at its northern range extent in the western North Atlantic (USA)

Three species of Bryopsis have commonly been reported from the western North Atlantic, but continuous morphological variation has often confounded specimen identification. This study evaluates the utility of the coding and non-coding sequences of the psbB gene cluster of Bryopsis, compared to morphological characters, as a means of distinguishing Bryopsis species. The sequences examined include a group II intron within the psbT gene, the 3′ exon of this gene, the spacer separating psbT and psbH, as well as the 5′ part of the latter gene. Sequences of 616 bp of Bryopsis from 28 collections from the study area were aligned with those for eight collections from elsewhere in the Atlantic and Pacific, in order to test the monophyly of Atlantic Bryopsis. The phylogenies were rooted using Lambia as an outgroup. Parsimony analysis resolved the sequences into five clades, with strong bootstrap support. Three of the clades had wide distributions, two including individuals from both the western and eastern North Atlantic and the Pacific and one including plants from the Caribbean and the Pacific. The other two clades were more restricted: one clade was found only in the warm temperate western North Atlantic, and the other derived from the central California coast. Three methods of cluster analysis were applied to the morphological data but failed to find robust higher level structure; they neither supported nor refuted the molecular data. The four clades from the western North Atlantic and Caribbean appear to be either seasonally or geographically disjunct throughout this region. The molecular data support the current recognition of multiple species of Bryopsis along the western North Atlantic, some with worldwide distributions, but the morphological data do not correlate with this.

Subtropical cyclones (STCs) derive a considerable portion of their energy from baroclinic and diabatic processes. The opportunity to investigate the roles of baroclinic and diabatic processes during the evolution of STCs from a potential vorticity (PV) perspective motivates this study. The roles of baroclinic and diabatic processes during the evolution of STCs are determined by calculating three PV metrics from the 0.5° NCEP Climate Forecast System Reanalysis dataset. The three PV metrics quantify the relative contributions of lower-tropospheric baroclinic processes, midtropospheric latent heat release, and upper-tropospheric dynamical processes during the evolution of individual cyclones. An evaluation of the three PV metrics, as well as the sign of the upper-tropospheric thermal vorticity, during the evolution of individual cyclones is used to devise an objective STC identification technique and construct a 1979–2010 climatology of North Atlantic (NATL) STCs that undergo tropical transition. An investigation of the intraseasonal variability associated with the location and frequency of STCs identified in the 1979–2010 climatology shows that STCs typically form over the southern Gulf of Mexico and western NATL during April–June; over the northern Gulf of Mexico and western NATL during July–September; and over the western, central, and eastern NATL during October–December. STC formation occurs most frequently during September, when baroclinic and convectively driven forcings overlap across portions of the NATL. The frequency of STC formation is sensitive to the phase of ENSO and is maximized during periods of anomalously low SSTs in the eastern equatorial Pacific.

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 277:181-196 (2004) - doi:10.3354/meps277181 Large-scale biodiversity pattern of Cumacea (Peracarida: Crustacea) in the deep Atlantic J. D. Gage1,*, P. J. D. Lambshead2, J. D. D. Bishop3, C. T. Stuart4, N. S. Jones† 1Dunstaffnage Marine Laboratory, Scottish Association for Marine Science, Oban PA37 1QA, UK 2Natural History Museum, Cromwell Road, London SW7 5BD, UK 3The Laboratory, Marine Biological Association of the United Kingdom, Plymouth PL1 2PB, UK 4Biology Department, University of Massachusetts, 100 Morrissey Boulevard, Boston, Massachusetts 02125, USA *Email: john.gage@sams.ac.uk †Deceased ABSTRACT: Large-scale biodiversity pattern is best known as latitudinal species diversity gradients (LSDGs) on land and may be causally linked to ecological and evolutionary processes influenced by solar insolation. Although similar LSDGs may exist in the sea, patterns are contradictory and not well understood. LSDGs among small benthic taxa in the deep sea are particularly problematic because of sampling and taxonomic limitations, and remoteness from solar-driven processes at the surface. Such explanatory processes are, in any case, likely to be very different from those on land. We investigate large-scale biodiversity pattern in deep-sea benthos by analysis of a data set of 225 species among 55937 individuals of Cumacea identified by the late N. S. Jones from 122 epibenthic sled samples (depth range ≥500 m to ≤4000 m) mostly taken near the continental margin throughout the deep Atlantic Ocean. Although the plotted data showed considerable scatter, and samples from the South Atlantic were relatively few and extended only to mid-latitudes, they showed a parabolic relationship to latitude, peaking at the equator. Sample diversity from the eastern North Atlantic (62 samples) tended to be higher than that from the western North Atlantic (19 samples), with linear regression relationships of diversity to latitude indicating a poleward decline differing only in elevation of the regression line, although those for the western North Atlantic, like those for the South Atlantic, were not significant. Adding 4 samples from the Nordic Seas as high-latitude end member markedly increased the slope of the regression for the deep eastern North Atlantic. This is consistent with impoverished cumacean diversity in the deep Nordic Seas basins caused by Quaternary extinctions and isolation from the deep Atlantic. Other regional differences in diversity, particularly between the western and eastern North Atlantic, also suggested a strong basin-scale imprint. This underlies the, probably productivity-related, negative relationships between diversity and latitude found, which were similar to those found previously in other deep-sea macrofaunal taxa and Foraminifera. Analysis of the whole Atlantic data set did not support a molluscan-type zoogeographic dispersion from the south into the South and then North Atlantic. Hence, although bathyal LSDG may exist in deep-sea Cumacea, evidence suggests that large-scale pattern may reflect regional history as much as modern ecology. KEY WORDS: Deep sea · Cumacea · Benthos · Latitudinal gradients · Regional diversity Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 277. Online publication date: August 16, 2004 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2004 Inter-Research.

The opportunity to examine the structure and evolution of the various upper-tropospheric precursors to the formation of North Atlantic (NATL) subtropical cyclones (STCs) that undergo tropical transition (TT) motivates this study. Intraseasonal variability associated with the location and frequency of NATL STCs forming in the presence of similar upper-tropospheric features, as well as similarities and differences in the various upper-tropospheric precursors to the formation of NATL STCs that undergo TT, are examined. NATL STCs that undergo TT are categorized according to the upper-tropospheric features associated with their formation during 1979–2010 using the 0.5° NCEP Climate Forecast System Reanalysis dataset. This categorization allows for the documentation of the location and frequency of STCs forming in the presence of similar upper-tropospheric features and for the construction of cyclone-relative composites during the five days prior to STC formation.NATL STCs that undergo TT are separated into one of three categories based on the upper-tropospheric features associated with their formation: 1) cutoff lows, 2) meridional troughs, and 3) zonal troughs. STCs included in the cutoff low and meridional trough categories typically develop poleward of ~25°N over the western, central, and eastern NATL during September–November and August–November, respectively. In contrast, STCs included in the zonal trough category typically develop equatorward of ~30°N over the western NATL during June–September. Cyclone-relative composites reveal that ~61% of the categorized NATL STCs that undergo TT form in association with an upper-tropospheric feature whose structure and evolution are linked to anticyclonic wave breaking.

In spite of their excellent preservation potential and abundance, brittle-star microfossils are still an underexploited source of alpha-taxonomical data. Knowledge on the Lower Cretaceous fossil record of the ophiuroids is particularly patchy, hampering the use of the ophiuroids as a model organism to explore macroevolutionary, taphonomic and other further-reaching aspects. Here, we describe three ophiuroid assemblages mostly based on dissociated lateral arm plates from the early Aptian of Cuchia (Cantabria, northern Spain), and the latest Aptian of Wizard Way (Texas, USA). A total of eleven species were identified. Ten species are new to science, three of which (Ophioleuce sanmigueli sp. nov., Ophiozonella eloy sp. nov. and Ophiodoris holterhoffi sp. nov.) are formally described as new. The two Spanish assemblages are dominated by an ophionereidid and an ophiolepidid, and the Texan one by an ophionereidid and, to a much lesser extent, an ophiacanthid assemblage. Our analysis reveals that the eastern (Cuchia) and western (Texas) North Atlantic faunal spectra were not fundamentally different from each other during the Aptian. We furthermore present the first clear bathymetric gradient in the ophiuroid fossil record, comparing the Texan assemblage with a recently discovered coeval fauna from middle bathyal palaeodepths of Blake Nose, western North Atlantic, and show that Aptian shallowwater (<200 m) and deep-sea ophiuroid communities were clearly distinct. Finally, we argue that the Aptian shallowwater assemblages, although dominated by families which typically occur in present-day mid- to low-latitude shallow seas, have no modern equivalents in terms of family-level composition.

The cyanobacterium Prochlorococcus numerically dominates the photosynthetic community in the tropical and subtropical regions of the world's oceans. Six evolutionary lineages of Prochlorococcus have been described, and their distinctive physiologies and genomes indicate that these lineages are "ecotypes" and should have different oceanic distributions. Two methods recently developed to quantify these ecotypes in the field, probe hybridization and quantitative PCR (QPCR), have shown that this is indeed the case. To facilitate a global investigation of these ecotypes, we modified our QPCR protocol to significantly increase its speed, sensitivity, and accessibility and validated the method in the western and eastern North Atlantic Ocean. We showed that all six ecotypes had distinct distributions that varied with depth and location, and, with the exception of the deeper waters at the western North Atlantic site, the total Prochlorococcus counts determined by QPCR matched the total counts measured by flow cytometry. Clone library analyses of the deeper western North Atlantic waters revealed ecotypes that are not represented in the culture collections with which the QPCR primers were designed, explaining this discrepancy. Finally, similar patterns of relative ecotype abundance were obtained in QPCR and probe hybridization analyses of the same field samples, which could allow comparisons between studies.

Ratios of certain organochlorine pollutants in fish tissues are significantly different between the eastern and western North Atlantic and have been used to identify recent (&lt;1 year) transatlantic migrants of Atlantic bluefin tuna (Thunnus thynnus). In this study we observed limited variation of organochlorine pollutant ratios across collections of young-of-the-year (YOY) bluefin tuna from the western North Atlantic (WNA) and eastern North Atlantic (ENA) in different years and highly significant differences between WNA and ENA YOY samples each year and for all years combined. A significant increase in organochlorine ratios was noted between YOY and age-1 ENA bluefin tuna, consistent with the movement of YOY out of the Mediterranean Sea and into the ENA. Using baseline organochlorine ratios from WNA YOY to identify recent eastern migrants, 29% of age-2, 33% of age-3, and 24% of age-4 juvenile bluefin tuna in the WNA were identified as recent migrants from the east during 2011 and 2012. Applying baseline ratios from age-1 ENA bluefin tuna to identify recent migrants from the WNA, 14.3% of age-2, 9.5% of age-3, and 0% of age-4 juvenile bluefin tuna caught in the Bay of Biscay fishery were identified as recent western migrants during 2010 and 2011. These data reveal substantial connectivity of juvenile bluefin tuna across the North Atlantic and demonstrate that WNA juveniles are heavily subsidized by eastern fish.

Possible future change in tropical cyclone (TC) activity over the North Atlantic (NA) was investigated by comparison of 25-yr simulations of the present-day climate and future change under the A1B emission scenario using a 20-km-mesh Meteorological Research Institute (MRI) and Japan Meteorological Agency (JMA) atmospheric general circulation model. The present-day simulation reproduces many essential features of observed climatology and interannual variability in TC frequency of occurrence and tracks over the NA. For the future projection, the model is driven by the sea surface temperature (SST) that includes a trend projected by the most recent Intergovernmental Panel on Climate Change (IPCC) multimodel ensemble and a year-to-year variation derived from the present-day climate. A major finding is that the future change of total TC counts in the NA is statistically insignificant, but the frequency of TC occurrence will decrease in the tropical western NA (WNA) and increase in the tropical eastern NA (ENA) and northwestern NA (NWNA). The projected change in TC tracks suggests a reduced probability of TC landfall over the southeastern United States, and an increased influence of TCs on the northeastern United States. The track changes are not due to changes of large-scale steering flows; instead, they are due to changes in TC genesis locations. The increase in TC genesis in the ENA arises from increasing background ascending motion and convective available potential energy. In contrast, the reduced TC genesis in the WNA is attributed to decreases in midtropospheric relative humidity and ascending motion caused by remotely forced anomalous descent. This finding indicates that the impact of remote dynamical forcing is greater than that of local thermodynamical forcing in the WNA. The increased frequency of TC occurrence in the NWNA is attributed to reduced vertical wind shear and the pronounced local warming of the ocean surface. These TC changes appear to be most sensitive to future change in the spatial distribution of rising SST. Given that most IPCC models project a larger increase in SST in the ENA than in the WNA, the projected eastward shift in TC genesis is likely to be robust.

A global chemical transport model is used to study the three‐dimensional structure of the tropospheric ozone (O3) distribution over the North Atlantic Ocean during summer. A simplified representation of summertime O3 photochemistry appropriate for northern hemisphere midlatitudes is included in the model. The model is evaluated by comparing simulated O3 mixing ratios to summertime O3 measurements taken in and near the North Atlantic Ocean basin. The model successfully reproduces (1) the means and standard deviations of ozonesonde measurements over North America at 500 mbar; (2) the statistical characteristics of surface O3 data at Sable Island off the coast of North America and at Bermuda in the western North Atlantic; and (3) the mean midtropospheric O3 measured at Bermuda and also at the Azores in the eastern North Atlantic. The model underestimates surface O3 in the eastern North Atlantic, overestimates O3 in the lower free troposphere over the western North Atlantic, and also has difficulty simulating the upper tropospheric ozonesonde measurements over North America. An examination of the mean summertime O3 distribution simulated by the model shows a significant continental influence on boundary layer and free‐tropospheric O3 over the western North Atlantic. The model has also been exercised using a preindustrial NOx emission scenario. By comparing the present‐day and preindustrial simulations, we conclude that anthropogenic NOx emissions have significantly perturbed tropospheric O3 levels over most of the North Atlantic. We estimate that present‐day O3 levels in the lower troposphere over the North Atlantic are at least twice as high as corresponding preindustrial O3 levels. We find that the anthropogenic impact is substantial even in the midtroposphere, where modeled present‐day O3 mixing ratios are at least 1.5 times higher than preindustrial O3 levels.

In the eastern North Atlantic, declines in the volume of Atlantic Puffin (Fratercula arctica (Linnaeus, 1758)) eggs have been associated with shifts in the marine ecosystem, such as changes in the abundance of forage fishes and increasing sea-surface temperatures. In the western North Atlantic, where similar shifts in oceanographic conditions and changes in the abundance of forage fishes have presumably occurred, trends in the volume of Atlantic Puffin eggs remain unknown. In this study, we investigate Atlantic Puffin egg volume in the western North Atlantic. We compiled 140 years (1877–2016) of egg volume measurements (n = 1805) and used general additive mixed-effects models to investigate temporal trends and regional variation. Our findings indicate that Atlantic Puffin egg volume differs regionally but has remained unchanged temporally in the western North Atlantic since at least the 1980s.

In this study, we provide preliminary evidence of possible modulation by Saharan dust of hurricane genesis and intensification, by contrasting the 2007 and 2005 hurricane seasons. It is found that dust aerosol loadings over the Atlantic Ocean are much higher in 2007 than in 2005. The temperature difference between 2007 and 2005 shows warming in the low‐middle troposphere (900–700 hPa) in the dusty region in the eastern North Atlantic, and cooling in the Main Development Region (MDR). The humidity (wind) differences between 2007 and 2005 indicate significant drying (subsidence) in the Western North Atlantic (WNA) in 2007. The drier air in the WNA in 2007 is found to be associated with the further westward transport of the Saharan air layer (SAL). To quantify wind pattern favorable for transport of SAL over the WNA, we define a zonal wind stretch index which shows significant long‐term correlation with the mid‐level humidity in the WNA. Analyses of the stretch index and related environmental controls suggest that the westward expansion of the Saharan dry air and dust layer can be an important factor in contributing to the difference between the relatively quiescent hurricane season in 2007 and the very active season of 2005.

Contrasting patterns of α- and β-diversity in deep-sea bivalves of the eastern and western North Atlantic

&amp;lt;p&amp;gt;Oxygen concentrations in the deep waters of the Lower St. Lawrence Estuary, in eastern Canada, have decreased by 50% over the past century, reaching hypoxic levels. To study the causes of this deoxygenation, we applied a mixing model (an extended multi-parameter analysis - eOMP) to data collected in the St. Lawrence Estuary since the 1970s and from the late 1990s to 2018. This method accounts for diapycnal mixing and can distinguish between the physical and biogeochemical causes of deoxygenation. The eOMP reveals that, in recent years, most of the deoxygenation of deep waters of the St. Lawrence Estuary is due to a change in the circulation pattern in the western North Atlantic. Since 2008, the Slope Sea and the deep waters of the St. Lawrence Estuary are fed by an increasing amount of oxygen-poor North Atlantic Central Waters (NACW), transported by the Gulf Stream, at the expense of oxygen-rich Labrador Current Waters (LCW). The oxygenation level of the St. Lawrence Estuary therefore reflects what is happening in the western North Atlantic. In contrast, the eOMP shows that, from the 1970s to the late 1990s, biogeochemical changes such as local eutrophication and variations in oxygen consumption rates in the North Atlantic dominated the deoxygenation.&amp;amp;#160;&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;Further analyses suggest that the variability in the LCW:NACW ratio in the Slope Waters is mainly controlled by the Scotian Shelf-break Current, an extension of the Labrador Current, and not by the position or strength of the Gulf Stream, as often suggested. When the Labrador Current is strong, little of the southward flowing Labrador Current waters follow the coast all the way to the Scotian Shelf, and most of these waters are deviated east towards the North Atlantic. The opposite is true when the Labrador Current is weak. We will present some analysis of LCW trajectories in different conditions and discuss their potential drivers, based on a high resolution model. Overall, our results highlight the primary role of the Labrador Current in determining (i) the oxygen concentration and other water properties on the western North Atlantic continental shelf and slope, and (ii) the advection of fresh Labrador Current Water into the subpolar North Atlantic, with possible implications on the thermohaline and gyre circulation.&amp;lt;/p&amp;gt;

This study explores the connection of Rossby wave breaking (RWB) with tropical and extratropical variability during the Atlantic hurricane season. The exploration emphasizes subtropical anticyclonic RWB events over the western North Atlantic, which strongly affect tropical cyclone (TC) activity. The first part of the study investigates the link between RWB and tropical sea surface temperature (SST) variability. Tropical SST variability affects tropical precipitation and modulates the large-scale atmospheric circulation over the subtropical Atlantic, which influences the behaviors of Rossby waves and the frequency of RWB occurrence. Meanwhile, RWB regulates surface heat fluxes and helps to sustain SST anomalies in the western North Atlantic. The second part of the study explores the connections between RWB and extratropical atmosphere variability by leveraging weather regime analysis. The weather regimes over the North Atlantic are closely associated with RWB over the eastern North Atlantic and western Europe, but show weak associations with RWB over the western North Atlantic. Instead, RWB over the western basin is closely related to the weather regimes in the North Pacific–North America sector. The finding helps clarify why the correlation between the Atlantic TC activity and the summertime North Atlantic Oscillation is tenuous. The relations between the extratropical weather regimes and tropical climate modes are also discussed. The findings suggest that both tropical and extratropical variability are important for understanding variations of RWB events and their impacts on Atlantic TC activity.

Retreat of the Laurentide ice sheet tracked by the isotopic composition of Pb in western North Atlantic seawater during termination 1