Western North Atlantic Water Research Articles

First Atlantic satellite tracks of 'lost years' green turtles support the importance of the Sargasso Sea as a sea turtle nursery.

In-water behaviour and long-term movements of oceanic-stage juvenile sea turtles are not well described or quantified. This is owing to technological or logistical limitations of tracking small, fast-growing animals across long distances and time periods within marine habitats. Here, we present, to our knowledge, the first long-term offshore tracks of oceanic green turtles (Chelonia mydas) in western North Atlantic waters. Using a tag attachment technique developed specifically for young (less than 1 year old) green turtles, we satellite-tracked 21 oceanic-stage green turtles (less than 19 cm straight carapace length) up to 152 days using small, solar-powered transmitters. We verify that oceanic-stage green turtles: (i) travel to and remain within oceanic waters; (ii) often depart the Gulf Stream and North Atlantic Subtropical Gyre currents, orienting towards waters associated with the Sargasso Sea; (iii) remain at the sea surface, using thermally beneficial habitats that promote growth and survival of young turtles; and (iv) green turtles orient differently compared to same stage loggerhead turtles (Caretta caretta). Combined with satellite tracks of oceanic-stage loggerhead turtles, our work identifies the Sargasso Sea as an important nursery habitat for North Atlantic sea turtles, supporting a growing body of research that suggests oceanic-stage sea turtles are behaviourally more complex than previously assumed.

Prochlorococcus Ecotype Abundances in the North Atlantic Ocean As Revealed by an Improved Quantitative PCR Method

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.

Water masses in the upper and middle North Atlantic Ocean east of the Azores

During the “ANA” cruise in November 1988, Western North Atlantic Water (WNAW) was found linked to the Azores Current (AC) at 23°W, where according to various authors Eastern North Atlantic Water (ENAW) forms a boundary with WNAW east of the Mid-Atlantic Ridge (MAR). This boundary changes position during the year. The vein of Mediterranean Water (MW) moving towards the MAR seems to be connected with the AC, and restricts the penetration of ENAW of subpolar origin (ENAW P). A subsurface front has been found along 42°N, separating ENAW of subtropical origin (ENAW T) that moves northeastwards generating a cyclonic eddy that is confined between the lower limit of the surface layer and approximately the 27.06 isopycnal, and modified ENAW P that moves southwards forming various anticyclonic eddies.

Distribution of copper-complexing organic ligands in western North Atlantic waters

Organic materials able to complex ionic copper were extracted from seawater by a technique involving the saturation of complexing sites by the addition of excess ionic copper, followed by adsorption on a Sep-Pak C 18 column. Application of this technique to samples from a series of cruises on the Scotian Shelf covering 3 seasons demonstrated a correlation between biological activity, and particularly phytoplankton productivity, and ligand production. The complexing sites were associated with the polar fraction of organic materials, as determined by compound class separations using the Chromarod-Iatroscan technique. INTRODUCTION Stream, on the CSS 'Dawson', during May, August and November 1986. Sampling stations are shown in Fig. l . In previous papers, we have demonstrated that Stn 1 is located on the Scotian Shelf; Stn 2 on the slope; cultured phytoplankton are able to release significant amounts of organic matter capable of complexing copper ions (Zhou & Wangersky 1985). The release of dissolved organic matter by phytoplankton may be an important source of organic ligands in the sea, although the terrestrial input could be dominant in coastal waters where fresh water runoff is significant (Zhou & Wangersky 198913). Most of the reported distributions of complexation characteristics in open water, such as organic ligand concentrations and stability constants for trace metal-organic complexes, were directly related to phytoplankton productivity (Hirose & Sugimura 1983, Buckley & van den Berg 1986, Kramer 1986) or indirectly derived from highly productive surface waters (Mackey 1986). In this study, we used a modified Sep-Pak C 18 column extraction method and a Chromarod TLC technique (Zhou & Wangersky 1989a) to study coppercomplexing by organic ligands in the western Atlantic. , Our results showed that phytoplankton activity could affect the quality and quantity of these compounds and their distribution patterns. MATERIALS AND METHODS 1 Sampling. Seawater samples were collected in 3 cruises across the Scotian Shelf to the edge of Gulf SCALE K m

Rare earth element transport in the western North Atlantic inferred from Nd isotopic observations

The isotopic composition of Nd in the water column from several western North Atlantic sites and formational areas for North Atlantic Deep Water shows extensive vertical structure at all locations. In regions where a thermocline is well-developed, large isotopic shifts (2 to 3 ϵ units) are observed across the base of the thermocline. Regions without a thermocline are characterized by much more gradual shifts in isotopic composition with depth. In general, the data reveal an excellent correlation between the Nd isotopic distribution in the western North Atlantic water column and the distribution of water masses identified from temperature and salinity characteristics. NADW, as identified from T-S properties, is also characterized by a well-defined isotopic composition having ϵ_(Nd)(0) = −13.5 ± 0.5. This signature is associated with waters identified as NADW from high latitudes near formational areas in the Labrador Sea down to the equatorial region. The isotopic signature of NADW would appear to be formed by a blend of more negative waters originating in the Labrador Sea (ϵ_(Nd)(0) < −18) and more positive waters originating in the overflows from the Norwegian and Greenland Seas (ϵ_(Nd)(0) ≈ −8 to −10) and is consistent with classical theories on the formation of NADW. The isotopic signature of NADW is propagated southward to the equator where it is gradually being thinned out by mixing from above and below with more radiogenic Nd associated with northward-spreading Antarctic Intermediate and Bottom Waters. The preservation of the isotopic signature of NADW over these large distances indicate that the REE undergo extensive lateral transport. The isotopic composition of Nd is largely conservative over the time scales of mixing within the Atlantic in spite of the intrinsic nonconservative behavior of neodymium. Nd concentration gradients generally show surface waters to be depleted in Nd relative to deep waters, which must require vertical transport processes. However, isotopic differences in the water column preclude the local downward transport of REE from the surface into underlying deep waters as a simple explanation of the concentration gradient. The apparent decoupling of REE in NADW from overlying (local) surface waters and the increasing concentration with depth provide a conflict with simple vertical transport mechanisms that is not yet resolved.

Foraminifera: Distribution of Provinces in the Western North Atlantic

All published distributional data on recent benthic foraminifera of the North American Atlantic continental margin were archived into computerized catalogs. Cluster analysis of these data delimited seven large, marginally overlapping provinces exhibiting a congruous relationship with western North Atlantic water masses. The single major latitudinal faunal change occurs at Cape Hatteras.

Observational Evidence for Transformation of Tropospheric Waters within Cyclonic Rings

Abstract The North American Slope and Gulf Stream components that constitute the initial water masses within a cyclonic ring can combine with Sargasso Sea water to generate Western North Atlantic Water (WNAW) common to the main anticyclonic gyre in the Sargasso Sea. Evidence from the 1967 ring survey indicates that warm, saline water from above mixes with cooler, fresher water from below to produce WNAW in the region of the mid-thermocline (7–12°C). At mid-thermocline depths, WNAW can be traced along σt surfaces from the ring center to the Sargasso Sea. Vertical stability conditions support the mixing concept. Distributions of the zooplankton species Nematoscelis megalops found for the 1975–76 Ring D survey can be interpreted as indicating mixing and detrainment through the mid-thermocline region.

Age determination of harbour porpoise, Phocoena phocoena (L.), in the western North Atlantic.

Age, based on analysis of dentinal growth layers, was determined in a sample of 121 harbour porpoises, Phocoena phocoena (L.), from western North Atlantic waters. One growth layer, consisting of a thick opaque zone and a relatively thin translucent zone, is deposited each year.Mean thicknesses of opaque and translucent zones in males and females were 347 μm, 114 μm, 432 μm, and 125 μm, respectively. Significant reduction in thicknesses of growth layers with age was found in both sexes, the major contribution in both cases being progressive reduction in thickness of the opaque zones. Translucent-zone thickness decreased with age in males, but significantly increased in thickness in females. Formation of the opaque zone occurs from June through February, and formation of the translucent zone from January to early September. This overlap is attributed to the protracted calving season of this population, and precludes any simple relationship between food supply and zonation, as proposed by others. Age–length relationships based on numbers of dentinal layers were calculated for males and females using regression analysis. Best fits of body length (b) against age (expressed by completed dentinal layers) (d) were obtained from the curvilinear equations: d = [b/(−1.30b + 209.35)] −1 for males, and d = [b/(−0.84b + 156.15)] −1 for females.