Western North Atlantic Ocean Research Articles

A description of echolocation clicks recorded in the presence of True's beaked whale (Mesoplodon mirus).

True's beaked whales (Mesoplodon mirus) were encountered on two separate shipboard surveys on 24 July 2016 and 16 September 2017 in the western North Atlantic Ocean. Recordings were made using a hydrophone array towed 300 m behind the ship. In 2016, three different groups were sighted within 1500 m of the ship; clicks were recorded for 26 min. In 2017, a single group of five whales was tracked over the course of five hours in which the ship maintained a distance <4000 m from the group. A total of 2938 frequency-modulated (FM) clicks and 7 buzzes were recorded from both encounters. Plausible inter-click-intervals (ICIs) were calculated from 2763 clicks, and frequency and duration measurements were calculated from 2150 good quality FM clicks. The median peak frequencies were 43.1 kHz (2016, n = 718) and 43.5 kHz (2017, n = 1432). Median ICIs were 0.17 s (2016) and 0.19 s (2017). The spectra and measurements of the recorded clicks closely resemble Gervais's beaked whale clicks (Mesoplodon europaeus) and distinguishing between the two species in acoustic data sets proves difficult. The acoustic behavior of True's beaked whales was previously unknown; this study provides a description of echolocation clicks produced by this species.

Distribution of angel sharks (Squatinidae) in United States waters of the western North Atlantic Ocean

Distribution of angel sharks (Squatinidae) in United States waters of the western North Atlantic Ocean

Genetic evidence for regional philopatry of the Bull Shark (Carcharhinus leucas), to nursery areas in estuaries of the Gulf of Mexico and western North Atlantic ocean

Nursery areas are critical for the reproductive cycle and biological requirements of Bull Sharks (Carcharhinus leucas) as they increase the survival of populations. Females tend to be philopatric to these areas as documented in estuaries from Australia, and inferred in the northern Gulf of Mexico and western North Atlantic Ocean, but not yet confirmed in these regions. In coastal waters of the southeastern United States, several sites have been proposed as nurseries for the Bull Shark, but little is known about how adult females utilize these areas during parturition. Philopatry for the Bull Shark was evaluated by comparing sequences of the mitochondrial DNA control-region (mtDNA-CR) and 8 microsatellite loci in juveniles and neonates from four previously reported nursery areas in United States (US) coastal waters; three in the northern Gulf of Mexico (Texas, Louisiana and Charlotte Harbor, Florida) and one in the western North Atlantic Ocean (Indian River Lagoon, Florida). A group of adult individuals from the Gulf of Mexico and Atlantic Ocean off the southeastern US were used to test genetic differences owed to limited gene flow between both regions. The analysis of genetic variation with the mtDNA-CR showed no differences among nurseries within the Gulf but significant differences when comparing the nursery areas of the two regions (Gulf vs Atlantic). In contrast, genetic homogeneity was observed among nursery areas within and between regions with the nuclear microsatellites suggesting male biased dispersal among regions. In addition, adult individuals from each of these two broad regions (Gulf of Mexico and Atlantic Ocean) showed no significant differentiation with any of the markers characterized in this study. These patterns of genetic differences support evidence for philopatry, further relaying the importance of protection and effective management of critical nursery habitats for future conservation of the species.

The silicon stable isotope distribution along the GEOVIDE section (GEOTRACES GA-01) of the North Atlantic Ocean

Abstract. The stable isotope composition of dissolved silicon in seawater (δ30SiDSi) was examined at 10 stations along the GEOVIDE section (GEOTRACES GA-01), spanning the North Atlantic Ocean (40–60∘ N) and Labrador Sea. Variations in δ30SiDSi below 500 m were closely tied to the distribution of water masses. Higher δ30SiDSi values are associated with intermediate and deep water masses of northern Atlantic or Arctic Ocean origin, whilst lower δ30SiDSi values are associated with DSi-rich waters sourced ultimately from the Southern Ocean. Correspondingly, the lowest δ30SiDSi values were observed in the deep and abyssal eastern North Atlantic, where dense southern-sourced waters dominate. The extent to which the spreading of water masses influences the δ30SiDSi distribution is marked clearly by Labrador Sea Water (LSW), whose high δ30SiDSi signature is visible not only within its region of formation within the Labrador and Irminger seas, but also throughout the mid-depth western and eastern North Atlantic Ocean. Both δ30SiDSi and hydrographic parameters document the circulation of LSW into the eastern North Atlantic, where it overlies southern-sourced Lower Deep Water. The GEOVIDE δ30SiDSi distribution thus provides a clear view of the direct interaction between subpolar/polar water masses of northern and southern origin, and allow examination of the extent to which these far-field signals influence the local δ30SiDSi distribution.

Maternal Transfer of Flame Retardants in Sharks from the Western North Atlantic Ocean.

The present work represents a comprehensive study of in utero maternal transfer of legacy and emerging flame retardants (FRs) in marine predators. We analyzed liver tissues from pregnant sharks of five viviparous species, including blacknose shark ( Carcharhinus acronotus; n = 12), blacktip shark ( Carcharhinus limbatus; n = 2), bonnethead ( Sphyrna tiburo; n = 2), Atlantic sharpnose shark ( Rhizoprionodon terraenovae; n = 2), and spinner shark ( Carcharhinus brevipinna; n = 2), as well as their embryos ( n = 84 in total from five species), collected from the western North Atlantic Ocean. Concentrations of frequently detected emerging FRs in adult female blacknose sharks were determined to be 6.1-83.3 ng/g lipid weight (lw) for dechlorane analogues, 2.5-29.8 ng/g lw for tetrabromo- o-chlorotoluene, and nondetection -32.6 ng/g lw for hexabromobenzene. These concentrations were 1-2 orders of magnitude lower than those of legacy polybrominated diphenyl ether flame retardants (85.7-398 ng/g lw). Similar contamination profiles were also found in the other four species, although FR concentrations varied in different species. A total of 21 FRs were commonly found in developing embryos of female sharks from five species, demonstrating maternal transfer in utero. The maternal transfer ratio (i.e., ratio of the mean litter concentration to their mother's concentration) determined in blacknose shark mother/embryo groups for each FR chemical was negatively associated with its octanol-water partition coefficient. Our work lays a solid foundation for future investigation of the underlying mechanisms of in utero transfer and additional physical or chemical factors that affect maternal transfer.

First insights into the movements of young-of-the-year white sharks (Carcharodon carcharias) in the western North Atlantic Ocean

In recent years, white sharks (Carcharodon carcharias) have become more accessible to researchers off the northeastern U.S. as feeding aggregation sites have emerged and the population has increased. However, there has been limited research on young-of-the-year (YOY) sharks relative to older age classes in this region. Previous research indicated that YOY white sharks were most frequently observed in the New York Bight, suggesting the region serves a nursery role. To further examine the species’ use of this area, we deployed satellite and acoustic tags on ten YOY white sharks (138–166 cm total length) off Long Island, New York. The sharks remained resident in New York Bight waters through summer (August through October), further supporting the notion that the region is a nursery area. Southward movements were observed during fall, with overwintering habitat identified off North and South Carolina shelf waters. Return migrations toward the New York Bight were observed in some individuals the following spring. YOY white sharks in this heavily-populated region are exposed to anthropogenic impacts such as fisheries bycatch and coastal habitat degradation. As juvenile survival rates are important for long-term population sustainability, further research is necessary to assess the potential impacts of these activities on the western North Atlantic white shark population.

On the interaction between a hurricane, the Gulf Stream and coastal sea level

Tropical storms and hurricanes in the western North Atlantic Ocean can impact the US East Coast in several ways. Direct effects include storm surges, winds, waves, and precipitation and indirect effects include changes in ocean dynamics that consequently impact the coast. Hurricane Matthew [October, 2016] was chosen as a case study to demonstrate the interaction between an offshore storm, the Gulf Stream (GS) and coastal sea level. A regional numerical ocean model was used, to conduct sensitivity experiments with different surface forcing, using wind and heat flux data from an operational hurricane-ocean coupled forecast system. An additional experiment used the observed Florida Current (FC) transport during the hurricane as an inflow boundary condition. The experiments show that the hurricane caused a disruption in the GS flow that resulted in large spatial variations in temperatures with cooling of up to ~ 4 °C by surface heat loss, but the interaction of the winds with the GS flow also caused some local warming near fronts and eddies (relative to simulations without a hurricane). A considerable weakening of the FC transport (~ 30%) has been observed during the hurricane (a reduction of ~ 10 Sv in 3 days; 1Sv = 106 m3 s−1), so the impact of the FC was explored by the model. Unlike the abrupt and large wind-driven storm surge (up to 2 m water level change within 12 h in the South Atlantic Bight), the impact of the weakening GS on sea level is smaller but lasted for several days after the hurricane dissipated, as seen in both the model and altimeter data. These results can explain observations that show minor tidal flooding along long stretches of coasts for several days following passages of hurricanes. Further analysis showed the short-term impact of the hurricane winds on kinetic energy versus the long-term impact of the hurricane-induced mixing on potential energy, whereas several days are needed to reestablish the stratification and rebuild the strength of the GS to its pre-hurricane conditions. Understanding the interaction between storms, the Gulf Stream and coastal sea level can help to improve prediction of sea level rise and coastal flooding.

A Closure Study of Total Scattering Using Airborne In Situ Measurements from the Winter Phase of TCAP

We examine the performance of our approach for calculating the total scattering coefficient of both non-absorbing and absorbing aerosol at ambient conditions from aircraft data. Our extended examination involves airborne in situ data collected by the U.S. Department of Energy’s (DOE) Gulf Stream 1 aircraft during winter over Cape Cod and the western North Atlantic Ocean as part of the Two-Column Aerosol Project (TCAP). The particle population represented by the winter dataset, in contrast with its summer counterpart, contains more hygroscopic particles and particles with an enhanced ability to absorb sunlight due to the larger fraction of black carbon. Moreover, the winter observations are characterized by more frequent clouds and a larger fraction of super-micron particles. We calculate model total scattering coefficient at ambient conditions using size spectra measured by optical particle counters (OPCs) and ambient complex refractive index (RI) estimated from measured chemical composition and relative humidity (RH). We demonstrate that reasonable agreement (~20% on average) between the observed and calculated scattering can be obtained under subsaturated ambient conditions (RH &lt; 80%) by applying both screening for clouds and chemical composition data for the RI-based correction of the OPC-derived size spectra.

Phytoplankton chemotaxonomy within contiguous optical layers across the western North Atlantic Ocean and its relationship to environmental parameters

A CHEMTAX analysis of the phytoplankton community composition is presented for the summertime northwest Atlantic Ocean from the Sargasso Sea to the New England continental shelf. To minimize the confounding influence of light intensity-related changes in internal pigment concentration (photo-acclimation), we compared CHEMTAX community composition within (but not between) five discrete optical depth layers (OL1 -5) arranged vertically throughout and beneath the euphotic zone, and extending horizontally from the oligotrophic to mesotrophic regions. CHEMTAX model results revealed a gradient of increasing proportions of eukaryotes to prokaryotes in the landward direction. The oligotrophic oceanic waters were dominated about equally by Prochlorococcus and haptophytes with Synechococcus and prasinophytes being secondarily important, while the mesotrophic slope and shelf waters were dominated by haptophytes and prasinophytes, with Prochlorococcus undetectable in shelf waters. Redundancy analysis revealed strong and significant niche separations between eukaryotic and prokaryotic phytoplankton, with the cyanobacteria more common in warmer, saltier waters, and eukaryotic species more common in fresher, colder waters. Salinity was the strongest predictor of the phytoplankton community composition in OLs 2 through 5, but in the surface OL1 temperature was the strongest predictor. There were positive significant correlations between salinity and Prochlorococcus, and negative significant correlations between salinity and all eukaryote groups: pelagophytes, chlorophytes, haptophytes, diatoms, prasinophytes, cryptophytes, and dinoflagellates, in most cases the strength of the correlation increased with depth. Other environmental variables, PO43-, NO3-+NO2-, and vertical density stratification were all weak predictors of phytoplankton community composition.

Numerical Modeling of Historical Storm Tides and Waves and Their Interactions Along the U.S. East and Gulf Coasts

AbstractWe apply a coupled circulation‐wave model to simulate extreme sea levels induced by tropical cyclones at the basin scale. We quantify storm tides, surges, waves, and their interactions for historical tropical cyclones (1988–2015) in the western North Atlantic Ocean. Comparisons between model results and field observations along the U.S. East and Gulf Coasts indicate that the overall performance of the model is satisfactory, with a root‐mean‐square error, bias, and Willmott skill of, respectively, 0.31, −0.04 m, and 0.9 for storm tides and 1.94 m, −0.22 m, and 0.87 for significant wave heights. Model results show that the highest surge levels were generated in Western Long Island Sound and NY/NJ Harbor, along the coasts of the Carolinas and Southwest Florida, near the Mississippi River delta, and along the coasts of Louisiana and East Texas. We find that the nonlinear tide‐surge interaction is often significant, but its contribution to peak storm tides induced by the most extreme events (i.e., storms that caused storm tides larger than 2 m) was moderate (−12% to 5%). We find that the maximum wave setup was relatively large (tens of cm) in most coastal regions, but it did not necessarily coincide with the peak storm tide. The contribution of wave setup to peak storm tides induced by the most extreme events was less than 17%. Finally, we show that while some offshore storms did not affect the coastal areas with high storm surges or strong winds, they generated the largest historical wave setup at the coast.

Invasive Lionfish (Pterois volitans/miles) feeding ecology in Biscayne National Park, Florida, USA

Indo-Pacific Lionfish (Pterois volitans and P. miles) are venomous marine fishes in the family Scorpaenidae that invaded the Caribbean Sea, Gulf of Mexico, and western North Atlantic Ocean beginning in the mid-1980s. Lionfish are generalist, opportunistic predators that consume a variety of invertebrates and small reef fishes, such that the presence of Lionfish can significantly reduce reef fish abundance, diversity, and recruitment on invaded reefs. This study focused on the feeding ecology of Lionfish in Biscayne National Park (BNP), located in southeast Florida, USA. BNP consists of multiple marine habitats, including mangroves, seagrass beds, coral reefs, and limestone keys that support a diverse array of species resulting in multi-million dollar fishing and tourism industries. These habitats within BNP are at risk from the predatory impacts of invasive Lionfish. Through morphological prey identification of stomach contents, supplemented with DNA barcoding for identification of highly-digested prey items, Lionfish diet was analyzed and compared among fish sizes (immature, transitional and mature), BNP region (bay, shelf, and edge), and seasons (wet and dry). A total of 513 stomachs, containing more than 2600 prey items, were examined. We report that Lionfish in BNP fed predominantly on small reef fishes and small crustaceans, with a dietary shift from crustaceans to fishes occurring with increasing Lionfish size. Diets differed among BNP regions for medium-sized (100–179 mm) transitional Lionfish but not for large-sized (≥ 180 mm) mature individuals. Furthermore, dietary differences between seasons were observed in mature Lionfish, but no seasonal differences were detected for smaller Lionfish (i.e., immature and transitional Lionfish). Based on the diet habits observed, Lionfish in BNP could have significant ecological and economic consequences for BNP and south Florida coastal habitats.

Increased Abundance and Nursery Habitat Use of the Bull Shark (Carcharhinus leucas) in Response to a Changing Environment in a Warm-Temperate Estuary

A general northward shift in marine species distributions has been observed in the western North Atlantic Ocean, which may have significant ecological consequences. Large coastal sharks can have wide migratory distributions but show fidelity to specific nursery habitats. Here we show evidence for nursery range expansion into Pamlico Sound, North Carolina by a marine apex predator, the Bull Shark (Carcharhinus leucas). Previous assessments have shown little to no use of estuarine North Carolina waters as nursery habitat by Bull Sharks from 1965–2011. Juvenile sharks were rarely captured in a fishery-independent gillnet survey conducted by the North Carolina Division of Marine Fisheries (NCDMF) from 2003–2011, but were present every year from 2011–2016. Juvenile Bull Shark presence in the Sound was strongly related to early summer temperatures and late summer salinities, which have increased in the estuary over the 13 survey years, and further evidence for increasing water temperatures in Pamlico Sound was found in a 45-year data set for the NCDMF estuarine trawl survey. These results suggest that increasing water temperature and salinity have allowed Bull Sharks to expand their nursery habitat. This shift will have unknown, but potentially strong, impacts on both the local ecosystem and interactions with humans.

Characterization of large basking shark Cetorhinus maximus aggregations in the western North Atlantic Ocean.

Cetorhinus maximus aggregations recorded during extensive aerial survey efforts off the north-eastern United States between 1980 and 2013 included aggregations centring on sightings with group sizes of at least 30 individuals. These aggregations occurred in summer and autumn months and included aggregation sizes of up to 1398 individuals, the largest aggregation ever reported for this species. The aggregations were associated with sea surface temperatures of 13-24° C and chlorophyll-a concentrations of 0·4-2·6mg m-3 and during one aggregation, a high abundance of zooplankton prey was present. Photogrammetric tools allowed for the estimation of total body lengths ranging between 4 and 8m. Characterization of these events provides new insight into the potential biological function of large aggregations in this species.

Two-hundred year record of increasing growth rates for ocean quahogs (Arctica islandica) from the northwestern Atlantic Ocean

Ocean quahogs [Arctica islandica (Linnaeus, 1769)] are the longest-lived, non-colonial animal known today, with a maximum life span exceeding 500 years. Ocean quahogs are a commercially important bivalve, inhabiting the continental shelf of the North Atlantic basin. We examined growth rates of ocean quahogs that were fully recruited to the commercial fishery (>80-mm shell length) from four sites covering the range of the stock along the east coast of the U.S. through analysis of annual growth lines in the hinge plate. Both geographic and temporal differences (on a scale of decadal or longer) in growth rates exist throughout the range of the stock. The age at which animals reached 60, 80, and 90 mm decreased significantly, and average growth rates to 60, 80, and 90 mm increased significantly with birth year at a New Jersey and a Long Island site, both located in the southwestern portion of the stock, since the late 1700s/early 1800s, likely in response to increasing bottom water temperatures. That is, growth rates vary temporally with birth date at the southwestern sites, with younger animals growing at a much faster rate in recent decades than those born many decades previously, whereas at the northern sites off southern New England and on Georges Bank, changes in growth rates through time are limited to older adult animals or absent altogether. Thus, at the southern portion of the range, variation in growth rate over time exists in all phases of ocean quahog life, whereas on Georges Bank, little evidence exists for any differential in growth rate over the last ~200 years. The fact that ocean quahogs record the rise in ocean temperatures after the Little Ice Age in the Mid-Atlantic Bight southeast of southern New England, yet demonstrate little evidence of such a rise in the southern New England and Georges Bank region, would suggest a differential response of ocean circulation and its control of bottom water temperature between the northern and southern portions of the Mid-Atlantic Bight over the last 200+ years.

Spatial and seasonal patterns in acoustic detections of sperm whales Physeter macrocephalus along the continental slope in the western North Atlantic Ocean

Spatial and seasonal patterns in acoustic detections of sperm whales Physeter macrocephalus along the continental slope in the western North Atlantic Ocean

Spatial ecology and conservation of the tiger shark, Galeocerdo cuvier, in the equatorial Atlantic Ocean

Spatial ecology and conservation of the tiger shark, Galeocerdo cuvier, in the equatorial Atlantic Ocean

A High-Resolution Future Wave Climate Projection for the Coastal Northwestern Atlantic

A high-resolution wave climate projection for the northwestern Atlantic Ocean has been conducted to help assess possible regional impacts due to global climate change. The spectral wave model NOAA WAVEWATCH III is utilized with three coupled (two-way) grids to resolve the northwestern Atlantic and coastal southern and eastern USA at approximately 21 km and 7 km respectively, and covers the periods 1979--2003 (historic) and 2075--2099 (future). Hourly wind field forcings are provided by a high-resolution AGCM (MRI-AGCM 3.2S; 21 km) and allow for better modeling of large storm events (important for extreme event statistics). Climatological (25-year) comparisons between future and historical periods indicate significant wave heights will decrease in the northwestern Atlantic Ocean (-5.7 %) and Gulf of Mexico (-4.7 %) but increase in the Caribbean Sea (2.4 %). Comparisons also indicate that large changes in mean wave direction will occur in the Gulf of Mexico (5.0{\deg}), with the largest occurring west of the Florida peninsula (over 15{\deg}).

The Interconnected Global Climate System—A Review of Tropical–Polar Teleconnections

AbstractThis paper summarizes advances in research on tropical–polar teleconnections, made roughly over the last decade. Elucidating El Niño–Southern Oscillation (ENSO) impacts on high latitudes has remained an important focus along different lines of inquiry. Tropical to polar connections have also been discovered at the intraseasonal time scale, associated with Madden–Julian oscillations (MJOs). On the time scale of decades, changes in MJO phases can result in temperature and sea ice changes in the polar regions of both hemispheres. Moreover, the long-term changes in SST of the western tropical Pacific, tropical Atlantic, and North Atlantic Ocean have been linked to the rapid winter warming around the Antarctic Peninsula, while SST changes in the central tropical Pacific have been linked to the warming in West Antarctica. Rossby wave trains emanating from the tropics remain the key mechanism for tropical and polar teleconnections from intraseasonal to decadal time scales. ENSO-related tropical SST anomalies affect higher-latitude annular modes by modulating mean zonal winds in both the subtropics and midlatitudes. Recent studies have also revealed the details of the interactions between the Rossby wave and atmospheric circulations in high latitudes. We also review some of the hypothesized connections between the tropics and poles in the past, including times when the climate was fundamentally different from present day especially given a larger-than-present-day global cryosphere. In addition to atmospheric Rossby waves forced from the tropics, large polar temperature changes and amplification, in part associated with variability in orbital configuration and solar irradiance, affected the low–high-latitude connections.

Modeling population dynamics of roseate terns (Sterna dougallii) in the Northwest Atlantic Ocean

The endangered population of roseate terns (Sterna dougallii) in the Northwestern Atlantic Ocean consists of a network of large and small breeding colonies on islands. This type of fragmented population poses an exceptional opportunity to investigate dispersal, a mechanism that is fundamental in population dynamics and is crucial to understand the spatio-temporal and genetic structure of animal populations. Dispersal is difficult to study because it requires concurrent data compilation at multiple sites. Models of population dynamics in birds that focus on dispersal and include a large number of breeding sites are rare in literature. In this work, we propose a stochastic simulation model that captures the dispersal dynamics of this population of roseate terns. The colonization and decolonization (abandonment) of breeding colonies are modeled as discrete events that follow different dynamics than dispersal. We show that our model reproduces the properties of this population that have been observed in field data. We also analyzed the sensitivity of our model to alterations in different variables, and study the impact of these alterations in the model dynamics. Our results suggest that large colony population size exhibits a threshold sensitivity to adult survival, and that regional persistence is maintained by the larger populations.

Review paper Pseudocollinia histophagous ciliates infect krill in the Pacific and Atlantic Oceans and possibly worldwide

The genus Pseudocollinia (Apostomatida, Pseudocolliniidae) currently includes four species (P. beringensis, P. oregonensis, P. brintoni, and P. similis) that infect adults of seven numerically dominant krill species (Order Euphausiacea) in the northeastern Pacific (Bering Sea-to-Gulf of California). In this review, we found four reports in other parts of the world of misidentified or unidentified protists infecting krill. Based on their morphology, cell size and infection of the hemocoel’s host, we infer they are histophagous Pseudocollinia ciliates. We thus conclude that previous reports of protists (identified as microsporidians) infecting Thysanoessa inermis in the northwestern Atlantic Ocean (Bay of Fundy) and unidentified endoparasite ciliates infecting the Euphausia superba in the Southern Ocean (Admiralty Bay, King George Island), Euphausia pacifica in Sanriku, Japan and Euphausia similis var. armata in Tasmania, Australia are actually Pseudocollinia parasitoid ciliates that await to be morphologically and genetically described. This review provides strong evidence that apostome Pseudocollinia ciliates are widespread distributed in the Pacific and Atlantic Oceans, infecting at least nine krill species from Arctic-to-Antarctic zoogeographic regions, having perhaps worldwide distribution as several of their krill hosts. Future studies should focus on discovering parasitoid ciliates in other krill species, as well as in other phytoplankton and zooplankton taxonomic groups.