Western North Atlantic Ocean Research Articles

Genetic diversity of Borrelia garinii from Ixodes uriae collected in seabird colonies of the northwestern Atlantic Ocean

The occurrence of Borrelia garinii in seabird ticks, Ixodes uriae, associated with different species of colonial seabirds has been studied since the early 1990s. Research on the population structure of this bacterium in ticks from seabird colonies in the northeastern Atlantic Ocean has revealed admixture between marine and terrestrial tick populations. We studied B. garinii genetic diversity and population structure in I. uriae collected from seabird colonies in the northwestern Atlantic Ocean, in Newfoundland and Labrador, Canada. We applied a multi-locus sequence typing (MLST) scheme to B. garinii found in ticks from four species of seabirds. The B. garinii strains found in this seabird colony ecosystem were diverse. Some were very similar to strains from Asia and Europe, including some obtained from human clinical samples, while others formed a divergent group specific to this region of the Atlantic Ocean. Our findings highlight the genetic complexity of B. garinii circulating in seabird ticks and their avian hosts but also demonstrate surprisingly close connections between B. garinii in this ecosystem and terrestrial sources in Eurasia. Genetic similarities among B. garinii from seabird ticks and humans indicate the possibility that B. garinii circulating within seabird tick-avian host transmission cycles could directly, or indirectly via connectivity with terrestrial transmission cycles, have consequences for human health.

Influence of temperature on the occurrence and distribution of the sand shrimp Crangon septemspinosaSay, 1818 (Decapoda: Caridea: Crangonidae) in polyhaline lagoons in Maryland, USA

Abstract Sand shrimp, Crangon septemspinosaSay, 1818, is one of the most abundant decapod crustaceans in estuaries and coastal waters of the northwestern Atlantic Ocean, though little is known about its population dynamics in polyhaline lagoons of the mid-Atlantic region. Seasonal and spatial patterns of abundance and distribution of C. septemspinosa were evaluated in relation to temperature, salinity, and dissolved oxygen in Maryland coastal bays (MCBs) using monthly data (April to October 1994 to 2012). We tested the hypothesis that temperature influences the occurrence and distribution of sand shrimp in the lagoons. A consistent pattern of high relative abundance of shrimp in spring and its scarcity in summer and early fall was observed. Shrimp abundance was highest in the northern bays and at sites closest to the Ocean City Inlet during April, but lowest at sites in the upper parts of Chincoteague Bay and MCBs tributaries. As mean temperature increased from April (12.2–17.1 oC) to June (21.8–26.7 oC), the relative abundance of the shrimp decreased substantially at most sites except at two sites where mean water temperature was comparatively low (21.8–23.3 oC). By July, when mean temperature was at its maximum (23.1–28.9 oC) in the bays, shrimp were rarely caught in trawls even in early fall in spite of the decline in temperature. It is likely that shrimp moved into nearshore waters with cooler temperature or suffered high mortality due to high temperature during this period. Generalized linear models suggest that temperature, and temperature and dissolved oxygen combined, were the most important abiotic factors examined that influenced the spatial distribution of C. septemspinosa in May and June, respectively. Considering their trophic importance, the spatio-temporal variations in the occurrence and abundance of the shrimp have implications for food web dynamics in the MCBs.

On the Moisture Origins of Tornadic Thunderstorms

AbstractTornadic thunderstorms rely on the availability of sufficient low-level moisture, but the source regions of that moisture have not been explicitly demarcated. Using the NOAA Air Resources Laboratory HYSPLIT model and a Lagrangian-based diagnostic, moisture attribution was conducted to identify the moisture source regions of tornadic convection. This study reveals a seasonal cycle in the origins and advection patterns of water vapor contributing to winter and spring tornado-producing storms (1981–2017). The Gulf of Mexico is shown to be the predominant source of moisture during both winter and spring, making up more than 50% of all contributions. During winter, substantial moisture contributions for tornadic convection also emanate from the western Caribbean Sea (>19%) and North Atlantic Ocean (>12%). During late spring, land areas (e.g., soil and vegetation) of the contiguous United States (CONUS) play a more influential role (>24%). Moisture attribution was also conducted for nontornadic cases and tornado outbreaks. Findings show that moisture sources of nontornadic events are more proximal to the CONUS than moisture sources of tornado outbreaks. Oceanic influences on the water vapor content of air parcels were also explored to determine if they can increase the likelihood of an air mass attaining moisture that will eventually contribute to severe thunderstorms. Warmer sea surface temperatures were generally found to enhance evaporative fluxes of overlying air parcels. The influence of atmospheric features on synoptic-scale moisture advection was also analyzed; stronger extratropical cyclones and Great Plains low-level jet occurrences lead to increased meridional moisture flux.

A new Western North Atlantic Ocean kitefin shark (Squaliformes: Dalatiidae) from the Gulf of Mexico.

A new species of kitefin shark (Squaliformes; Dalatiidae) is described from the Gulf of Mexico (Western North Atlantic Ocean) based on five diagnostic features not seen on the only other known Mollisquama specimen, the holotype of Mollisquama parini Dolganov which was captured in the Eastern South Pacific Ocean. The new species, Mollisquama mississippiensis sp. nov., is distinguished from its congener by a putative pit organ located ventrally just posterior of the lower jaw margin center, photophores irregularly distributed along many areas of the body, 16 distinct ventral-abdominal photophore aggregations, and two differences associated with the dentition. Other potential distinguishing features are 10 fewer vertebrae than Mollisquama parini and six morphometric proportional differences that exceeded +/- 20% from the holotype.

Echinoderid mud dragons (Cyclorhagida: Kinorhyncha) from Senghor Seamount (NE Atlantic Ocean) including general discussion of faunistic characters and distribution patterns of seamount kinorhynchs

Investigation of Kinorhyncha from Senghor Seamount (tropical northeastern Atlantic Ocean) and the adjacent deep-sea floor revealed seven species of Echinoderes. Of these, Echinoderes kaempfae sp. nov. and Echinoderes schwieringae sp. nov. are described as new species. Echinoderes multiporus originally found on Eratosthenes Seamount, Mediterranean Sea, and Echinoderes cf. adrianovi originally found off Florida, northwestern Atlantic Ocean, were also recovered. In addition, three additional species, which possibly represent undescribed species, occurred on Senghor Seamount. Because of the low number of available specimens or necessity of further observations of closely related congeners for these three undescribed species, we provide only a brief description of them without naming them as new species. The comparison of each species with morphologically similar congeners is also provided. Based on all records of kinorhynchs from seamounts and the adjacent deep-sea floor in the Northeastern Atlantic Ocean, Mediterranean Sea, and Arctic Sea, it is suggested that (1) the kinorhynch fauna on seamounts is partly unique, (2) seamount kinorhynchs originate both from shallow waters and the deep sea, and (3) a few kinorhynch species diversified on seamounts.

50 to 30-Hz triplet and singlet down sweep vocalizations produced by sei whales (Balaenoptera borealis) in the western North Atlantic Ocean.

The life history, distribution, and acoustic ecology of the sei whale (Balaenoptera borealis) in the western North Atlantic Ocean remains poorly understood. In this study an array of bottom-mounted recorders captured previously undocumented low frequency 50 to 30-Hz triplet and singlet down sweep vocalizations in close association with signature 82 to 34-Hz sei whale down sweep vocalizations. Spatiotemporal correlations of acoustically tracked sei whales confirm the original vocalizations are produced by sei whales. The 50 to 34-Hz down sweep call types were characterized with a suite of five spectral and temporal measurements. The pattern and repetition of the full acoustic suite is suggestive of song structure and warrants further investigation. The discovery of vocalizations attributed specifically to sei whales enables historic acoustic records to be re-evaluated for the presence of this species throughout its range.

Hydrodynamic response of Bahamas archipelago to storm surge and hurricane generated waves – A case study for Hurricane Joaquin

The Bahamas or Lucayan Archipelago located in the western North Atlantic Ocean is highly susceptible to impact of hurricanes considering its location along the major pathways of Atlantic hurricanes and increased storminess in the Atlantic basin. The hydrodynamics of the narrow and steep carbonate continental shelf of Bahamas archipelago provides a stark contrast to the east coast of the United States by means of distinct interaction of shelves with hurricane induced waves, storm tide and currents. The present study implements a coupled ADCIRC-SWAN model to investigate the surge and wave dynamics along the coasts of Bahamas archipelago during Hurricane Joaquin, using multiple reanalyzed wind products. The analysis is focused on the hydrodynamic response of the archipelago considering its varying coastal bathymetry, slope and arching coastlines. Model computed a maximum significant wave height of 15 m, storm surge 1.5 m and coastal currents of 4 m/s during Hurricane Joaquin. Moreover, validation study also shows very good agreement with the buoy observations from the region. Spatio-temporal variability of storm tide and waves along with nonlinear impacts of wave setup and setdown highlights the dominance of waves with moderate influence of storm tides along the coastal zone of the island chain. The study also evaluated interaction of coastal currents with the arching coastlines of the Bahamas. In addition, wave parameters attributed to the sinking of the cargo ship El-Faro during the Hurricane Joaquin have been examined. Significant wave heights exceeding 12.5 m with wave period of 12.5 s and the reversing wave direction during Hurricane Joaquin might have resulted in the capsize of the cargo ship.

Thin chlorophyll layer concomitant of the thermohaline intrusion in the confluence of the Gulf Stream and Labrador Current (a case study)

Summary Based on the depth-cycling data of a fluorometer probe in the northwestern Atlantic ocean, this paper considers features of the chlorophyll fluorescence layer against a background of concurrent variability of seawater temperature and fluorescence of CDOM (Colored Dissolved Organic Matter). The vertical distributions of chlorophyll fluorescence complied with the criteria of a thin chlorophyll layer at the site where changes of temperature and CDOM fluorescence were indicative of the intrusion of Labrador waters into adjacent warmer waters below the upper mixed layer. As may be supposed, the thin chlorophyll layer was due to the gyrotactic trapping of phytoplankton cells induced by water shear between the upper mixed layer and the intrusion.

Small pigmented eukaryotes play a major role in carbon cycling in the P‐depleted western subtropical North Atlantic, which may be supported by mixotrophy

AbstractWe found that in the phosphate (PO4)‐depleted western subtropical North Atlantic Ocean, small‐sized pigmented eukaryotes (P‐Euk; < 5 μm) play a central role in the carbon (C) cycling. Although P‐Euk were only ~ 5% of the microbial phytoplankton cell abundance, they represented at least two thirds of the microbial phytoplankton C biomass and fixed more CO2 than picocyanobacteria, accounting for roughly half of the volumetric CO2 fixation by the microbial phytoplankton, or a third of the total primary production. Cell‐specific PO4 assimilation rates of P‐Euk and nonpigmented eukaryotes (NP‐Euk; < 5 μm) were generally higher than of picocyanobacteria. However, when normalized to biovolumes, picocyanobacteria assimilated roughly four times more PO4 than small eukaryotes, indicating different strategies to cope with PO4 limitation. Our results underline an imbalance in the CO2 : PO4 uptake rate ratios, which may be explained by phagotrophic predation providing mixotrophic protists with their largest source of PO4. 18S rDNA amplicon sequence analyses suggested that P‐Euk was dominated by members of green algae and dinoflagellates, the latter group commonly mixotrophic, whereas marine alveolates were the dominant NP‐Euk. Bacterivory by P‐Euk (0.9 ± 0.3 bacteria P‐Euk−1 h−1) was comparable to values previously measured in the central North Atlantic, indicating that small mixotrophic eukaryotes likely exhibit similar predatory pressure on bacteria. Interestingly, bacterivory rates were reduced when PO4 was added during experimental incubations, indicating that feeding rate by P‐Euk is regulated by PO4 availability. This may be in response to the higher cost associated with assimilating PO4 by phagocytosis compared to osmotrophy.

Environmental predictors of habitat suitability and occurrence of cetaceans in the western North Atlantic Ocean

The objective of this study was to identify the main environmental covariates related to the abundance of 17 cetacean species/groups in the western North Atlantic Ocean based on generalized additive models, to establish a current habitat suitability baseline, and to estimate abundance that incorporates habitat characteristics. Habitat models were developed from dedicated sighting survey data collected by NOAA- Northeast and Southeast Fisheries Science Centers during July 2010 to August 2013. A group of 7 static physiographic characteristics and 9 dynamic environmental covariates were included in the models. For the small cetacean models, the explained deviance ranged from 16% to 69%. For the large whale models, the explained deviance ranged from 32% to 52.5%. Latitude, sea surface temperature, bottom temperature, primary productivity and distance to the coast were the most common covariates included and their individual contribution to the deviance explained ranged from 5.9% to 18.5%. The habitat-density models were used to produce seasonal average abundance estimates and habitat suitability maps that provided a good correspondence with observed sighting locations and historical sightings for each species in the study area. Thus, these models, maps and abundance estimates established a current habitat characterization of cetacean species in these waters and have the potential to be used to support management decisions and conservation measures in a marine spatial planning context.

Hybridization between sympatric hammerhead sharks in the western North Atlantic Ocean.

Hybridization between closely related species has been documented across a wide range of taxa but has not been well studied in elasmobranchs. Hammerhead sharks have drawn global conservation concern because they experience some of the highest mortality rates among sharks when interacting with fisheries. Here we report on the detection of hybrids between the globally distributed scalloped hammerhead ( Sphyrna lewini) and recently described Carolina hammerhead ( S. gilberti) which are only known from the western Atlantic Ocean. Using a genomics approach, 10 first-generation hybrids and 15-17 backcrosses were detected from 554 individuals. The identification of backcrosses demonstrates hybrids are viable, and all backcrosses but one involved a scalloped hammerhead. All hybrids but one possessed Carolina hammerhead mtDNA, indicating sex-biased gene flow between species. Repeated hybridization and backcrossing with scalloped hammerheads could lead to the loss of endemic Carolina hammerheads.

Presence of a resting population of female porbeagles (Lamna nasus), indicating a biennial reproductive cycle, in the western North Atlantic Ocean: suppl. figs. 1-3

Presence of a resting population of female porbeagles (Lamna nasus), indicating a biennial reproductive cycle, in the western North Atlantic Ocean: suppl. figs. 1-3

Presence of a resting population of female porbeagles (Lamna nasus), indicating a biennial reproductive cycle, in the western North Atlantic Ocean

Presence of a resting population of female porbeagles (Lamna nasus), indicating a biennial reproductive cycle, in the western North Atlantic Ocean

Novel Dechlorane Analogues and Possible Sources in Peregrine Falcon Eggs and Shark Livers from the Western North Atlantic Regions

During the investigation of dechlorane-related chemicals in North American wildlife, two unknown polychlorinated compounds (referred to as U1 and U2) were discovered. After extensive sample cleanup, structural information on U1 and U2 was characterized by gas chromatography (GC) coupled with single quadrupole mass spectrometer (MS) or GC-quadrupole time-of-flight (QToF) MS. Mass spectral evidence suggests that both U1 and U2 are structurally related to Dechlorane 603 (Dec603; C17H8Cl12), an analogue of the chlorinated flame retardant Dechlorane Plus. From the results we suspect U1 (C17H9Cl11) to be a monohydro analogue of Dec603 (i.e., one chlorine atom in Dec603 is replaced by a hydrogen atom). U1 may be formed via the degradation of Dec603's stereoisomers or present as an impurity in commercial Dec603 products. Mass spectral characterization of U2 (C17H7OCl11) suggests it is a carbonylic derivative of Dec603, likely formed via metabolic transformation of Dec603 or its photoisomer. Semiquantitative measurement revealed that U1 and U2 were present at estimated median concentrations of 49 ng/g lipid weight (lw) and 59 ng/g lw in peregrine falcon ( Falco peregrinus) eggs, from the mid-Atlantic region of the United States, and 4.6 and 3.0 ng/g lw in shortfin mako shark ( Isurus oxyrinchus) livers from the western North Atlantic Ocean, respectively. Our results demonstrate the occurrence of these two novel Dec603-related chemicals in both terrestrial and aquatic ecosystems.

Synthesizing expert opinion to assess the at-sea risks to seabirds in the western North Atlantic

Marine environments are subject to a range of human disturbances. Identifying effective conservation strategies, in order to manage or mitigate the negative impacts of human activities, requires a way to first identify and evaluate the impact of activities on ecosystem components. Multicriteria decision analysis (MCDA) techniques such as the Analytic Hierarchy Process (AHP) offer a way to systematically evaluate and integrate stakeholder opinion in order to set priorities and make decisions. With a goal to synthesize current knowledge of the potential impacts of human activity on breeding and non-breeding seabirds in the western North Atlantic Ocean, we present a case study involving the use of AHP to assess sensitivity of species to such hazards as: fisheries bycatch, oiling, light pollution, vessel traffic, marine debris, and offshore wind turbines. Based on responses from ten North Atlantic seabird experts, fisheries bycatch (particularly when involving suspended gill nets) was identified as the greatest risk across a wide range of species, with an overall relative value of 0.47±SE 0.026. Oiling risk was the second most highly ranked (0.26±0.026, of which 0.214 corresponded with surface oil, 0.044 with oil and gas platform interactions), and was considered to have the greatest potential impact on alcids (Common and Thick-billed Murre, Atlantic Puffin, Razorbill, Dovekie). Offshore wind turbines (0.097±0.022), marine debris (0.08±0.016), light pollution (0.058±0.0077), and traffic (0.042±0.0053) were considered to be less serious risks for seabirds than fisheries bycatch and oiling. In addition to demonstrating how relative risk can be quantified using a multicriteria decision analysis technique such as AHP, we summarize the sensitivities of fourteen seabirds and suggest ways in which multicriteria decision analysis can enhance conservation planning.

Using oxytetracycline validation for confirmation of changes in vertebral band-pair deposition rates with ontogeny in sandbar sharks (Carcharhinus plumbeus) in the western North Atlantic Ocean: Supplementary Table 1

Using oxytetracycline validation for confirmation of changes in vertebral band-pair deposition rates with ontogeny in sandbar sharks (Carcharhinus plumbeus) in the western North Atlantic Ocean: Supplementary Table 1

Using oxytetracycline validation for confirmation of changes in vertebral band-pair deposition rates with ontogeny in sandbar sharks (Carcharhinus plumbeus) in the western North Atlantic Ocean

Using oxytetracycline validation for confirmation of changes in vertebral band-pair deposition rates with ontogeny in sandbar sharks (Carcharhinus plumbeus) in the western North Atlantic Ocean

A multi-methods approach supports the effective management and conservation of coastal marine recreational flats fisheries

The recreational, catch and release fishery for fishes that inhabit shallow-water, coastal marine habitats in tropical and sub-tropical regions (called the flats fishery) is economically valuable and increasingly perceived as a sustainable ecotourism pursuit. However, knowledge of many aspects of target species (such as bonefish, tarpon and permit) ecology is incomplete, and fishery- and non-fishery-related threats to the fish and habitats are numerous and often poorly understood. The International Bonefish and Tarpon Symposium is convened every three years to share new knowledge and to chart directions for future research, with a focus on research that informs conservation and management. Most of the articles in this Special Issue focus on the flats fishery in the Caribbean Sea, Gulf of Mexico, and western North Atlantic ocean, but the findings presented here provide guidance for similar work in other regions. Conservation and management of flats fisheries present a challenge because the fisheries are typically data poor; they occur in locations that lack resources and there are scant data on the target species and their habitats. Since earlier symposia, much has been accomplished to fill knowledge gaps and contribute actionable knowledge to conservation. Studies are being replicated across a wider geographic range, and connectivity is being studied at local and regional scales. Citizen science and local ecological knowledge have contributed to a better understanding of historical trends and ongoing processes. In some instances, data have been applied to proactive habitat protections, as in the Bahamas, and to habitat restoration, as in Florida. In other instances, though much data have been gathered, additional information is needed before a comprehensive conservation strategy is possible, as in the Florida Keys. As the articles contained in this Special Issue demonstrate, a mixed-methods approach that uses complementary sources of information to construct a broad understanding of the flats fishery is necessary to guide research and inform conservation and management.

Assessment of the Relationship of Stock and Recruitment in the Atlantic Surfclam Spisula solidissima in the Northwestern Atlantic Ocean

Atlantic surfclams support a major commercial fishery in the western North Atlantic Ocean with landings consistently between 15,000 and 25,000 metric tons since 1982. The stock is not and historically has not been overfished nor has overfishing occurred; however, in recent years landings per unit effort have declined. Surfclams are a biomass dominant on the continental shelf and a bellwether of climate change in the northwestern Atlantic. This study investigated the relationship of broodstock and recruitment during a period when Mid-Atlantic warming initiated a shelf-wide shift in the surfclams range. A species distribution function model was used to assess the effective area occupied by surfclams for five study regions (Delmarva, New Jersey, Long Island, Southern New England, and Georges Bank). The effective area occupied by small surfclams was consistently much greater than that for large (≥120 mm) surfclams. Three independent statistical analyses of the stock-recruitment relationship found little evidence of a significant association in any of the five regions, suggesting that factors besides spawning stock biomass (SSB) are primary determinants of recruitment success. Interannual variability in recruitment, in part associated with variations in larval transport and in part associated with spatially different rates of mortality post-settlement, is an important source of uncertainty and warming bottom waters driving surfclams into new habitat may decouple any inherent interaction between recruits and SSB. A recruitment index obtained from a fishery-independent survey across the range of the stock, as a consequence, is unlikely to usefully presage changes in abundance of the fishable stock. The wider distribution of settlers relative to the fishable stock, however, positions the species well to respond to changing bottom water temperatures as Mid-Atlantic warming continues.

Combining multiple visual surveys to model the habitat of deep‐diving cetaceans at the basin scale

AbstractAimDeep‐diving cetaceans are oceanic species exposed to multiple anthropogenic pressures including high intensity underwater noise, and knowledge of their distribution is crucial to manage their conservation. Due to intrinsic low densities, wide distribution ranges and limited presence at the sea surface, these species are rarely sighted. Pooling data from multiple visual surveys sharing a common line‐transect methodology can increase sightings but requires accounting for heterogeneity in protocols and platforms.LocationNorth Atlantic Ocean and Mediterranean Sea.Time period1998 to 2015.Major taxaZiphiidae; Physeteriidae; Kogiidae.MethodsAbout 1,240,000 km of pooled effort provided 630 sightings of ziphiids, 836 of physeteriids and 106 of kogiids. For each taxon, we built a hierarchical model to estimate the effective strip width depending on observation conditions and survey types. We then modelled relative densities in a generalized additive modelling framework. Geographical predictions were limited to interpolations identified with a gap analysis of environmental space coverage.ResultsDeeper areas of the North Atlantic gyre were mostly environmental extrapolation in the predictions, thereby highlighting gaps in sampling across the different surveys. For the three species groups, the highest relative densities were predicted along continental slopes, particularly in the western North Atlantic Ocean where the Gulf Stream creates dynamic frontal zones and eddies.Main conclusionsPooling a large number of surveys provided the first basin‐wide models of distribution for deep‐diving cetaceans, including several data‐deficient taxa, across the North Atlantic Ocean and the Mediterranean Sea. These models can help the conservation of elusive and poorly known marine megafauna.