Phytoplankton species composition and abundance in a Gulf Stream warm core ring. I. Changes over a five month period

During the spring and summer of 1982, Gulf Stream warm core ring (WCR) 82B was sampled during four cruises from April to August to investigate the changes in the phytoplankton flora with time. Discrete water samples from 28 stations were collected for identification and enumeration of phytoplankton. The spring increase in WCR 828 occurred from late April to mid-May and was multiphasic; early periods were dominated by the diatoms Minidiscus trioculatus (4–5 μm diam.) and a small Thalassiosira, possibly T. bulbosa, while later periods were dominated by a small (2–3 μm) biflagellate. In June, another diatom concentration was detected at ring center, but this one was dominated by Chaetoceros cf. vixvisibilis and Leptocylindrus danicus. After interactions with and overwashes by the Gulf Stream and Slope Water in July, diatom numbers in the surface waters of the ring in August were greatly reduced relative to June, and no single species dominated. Changes in phytoplankton abundance in the ring core occurred on different time sequences from changes in the surrounding Slope Water or in the source water, the Sargasso Sea. The dominant taxa in the ring changed rapidly, on time scales of 1.5 months or less (intercruise time period). Successional changes were more important in altering the phytoplankton composition during the first two cruises, while sequential changes characterized the end of the study period. The ring center showed dramatic differences from its source water just 2 months after ring formation but remained distinct from the Slope Water for 4–5 months

Phytoplankton species composition and abundance in a Gulf Stream warm core ring. II. Distributional patterns

During the spring and summer of 1982, Gulf Stream warm core ring (WCR) 82B was sampled during four cruises from April to August to investigate phytoplankton distributional patterns. Discrete water samples from 28 stations were collected for identification and enumeration of phytoplankton. In April, when the water column was well mixed to 350 m, quantitative samples clustered by station when the 100 most frequently observed taxa were used as variables, indicating fairly unique assemblages at each station that were consistent with depth. Two transects across the ring in June showed a symmetrical diatom abundance maximum, dominated by Chaetoceros cf. vixvisibilis (maximum abundance 31,900 cells l–1) and Leptocylindrus danicus (maximum abundance 21,000 cells l–1), situated in the surface water at ring center. Dinoflagellate and coccolithophorid maxima were situated slightly deeper than the diatom maximum, in the seasonal thermocline from 20 to 35 m. A biomass maximum observed in a Shelf Water entrainment feature wrapping around the eastern perimeter of the ring contained elevated numbers of coccolithophorids and coccoid, unicellular monads (1–3 μm in diameter) and was thus compositionally distinct from the ring center biomass maximum. In July and August the ring underwent numerous interactions with and overwashes by the Slope Water and Gulf Stream. August samples from the ring, Sargasso Sea, Gulf Stream, and Slope Water all contained similar taxa and abundances. Different phytoplankton groups may be responding to different nutrient input mechanisms at the ring edge and center. Diatom maxima at ring center may form as a result of pulsed nutrient input from storms and a slight upwelling due to the gradual relaxation of the thermocline as the ring ages, while concentrations of ultraplanktonic algae (monads, coccolithophorids) toward the ring margin may result from near steady-state nutrient input along sloping isopycnals and/or advection from the ring exterior

Spatial/Spectral Resolution of a Galactic Bulge K3 Giant Stellar Atmosphere via Gravitational Microlensing

We present two Keck HIRES spectra (R=40,000) of a bulge K3 giant taken on successive nights during the second caustic crossing of the binary microlensing event EROS BLG-2000-5. This caustic crossing served to effectively resolve the surface of the source star: the spectrum from the second night is dominated by the limb, while the spectrum from the first night is comprised of light from a broader range of radii. To demonstrate that the spectra are adequate to resolve the differences between them, we analyze the H-alpha line. The equivalent width is ~8% smaller on the second night, and the signal-to-noise ratio per resolution element (165 and 75 on the two nights respectively) is sufficient to show that the difference is approximately constant over the ~2A (~15 resolution element) extent of the line. The sign of the difference is in the expected direction since the limb is the coolest part of the star and therefore should have the weakest H-alpha. We invite atmosphere modelers to predict the difference spectrum from the entire spectral range 5500<lambda<7900A so that these predictions can be compared to our observations.Comment: 12 pages, 3 figures, Accepted by ApJ Letters 2001 Jan

Stone artifacts

9 p. : ill. ; 24 cm.Includes bibliographical references (p. 9).Tula adze blades -- Knives (yutchawunta) -- Endscrapers (kalara) -- Hammerstones (coolkie) -- Pirris

Size Distributions of Coastal Ocean Suspended Particulate Inorganic Matter: Amorphous Silica and Clay Minerals and their Dynamics

Particulate inorganic matter (PIM) is a key component in estuarine and coastal systems and plays a critical role in trace metal cycling. Better understanding of coastal dynamics and biogeochemistry re-quires improved quantification of PIM in terms of its concentration, size distribution, and mineral species composition. The angular pattern of light scattering contains detailed information about the size and composition of particles. These volume scattering functions (VSFs) were measured in Mobile Bay, Alabama, USA, a dynamic, PIM dominated coastal environment. From measured VSFs, we determined through inversion the particle size distributions (PSDs) of major components of PIM, amorphous silica and clay minerals. An innovation here is the extension of our reported PSDs significantly into the sub-micron range. The PSDs of autochthonous amorphous silica exhibit two unique features: a peak centered at about 0.8mm between 0.2 and 4mm and a very broad shoulder essentially extending from 4mm to\u3e100mm. With an active and steady particle source from blooming diatoms, the shapes of amorphoussilica PSDs for sizes area, but showed more particles of sizes\u3e10mm inside the bay, likely due to wind-induced resuspension of larger frustules that have settled. Compared to autochthonous amorphous silica, the allochthonous clay minerals are denser and exhibit relatively narrower PSDs with peaks located between 1 and 4mm. Preferential settling of larger mineral particles as well as the smaller but denser illite component further narrowed the size distributions of clay minerals as they were being transported outside the bay. The derived PSDs also indicated a very dynamic situation in Mobile Bay when a cold weather front passed through during the experiment. With northerly winds of speeds up to 15 m s-1, both amorphous silica and clay minerals showed a dramatic increase in concentration and broadening in size distribution outside the exit of the barrier islands, indicative of wind-induced resuspension and subsequent advection of particles out of Mobile Bay. While collectively recognized as the PIM, amorphous silica and clay minerals, as shown in this study, possess very different size distributions. Considering how differences in PSDs and the associated particle areas will effect differences in sorption/desorption properties of these components, the results also demonstrate thepotential of applying VSF-inversion in studying biogeochemistry in the estuarine-coastal ocean system

The Impact of Coastal Phytoplankton Blooms on Ocean-Atmosphere Thermal Energy Exchange: Evidence From a Two-Way Coupled Numerical Modeling System

A set of sensitivity experiments are performed with a two-way coupled and nested ocean-atmosphere forecasting system in order to deconvolve how dense phytoplankton stocks in a coastal embayment may impact thermal energy exchange processes. Monterey Bay simulations parameterizing solar shortwave transparency in the surface ocean as an invariant oligotrophic oceanic water type estimate consistently colder sea surface temperature (SST) than simulations utilizing more realistic, spatially varying shortwave attenuation terms based on satellite estimates of surface algal pigment concentration. These SST differences lead to an similar to 88% increase in the cumulative turbulent thermal energy transfer from the ocean to the atmosphere over the three month simulation period. The result is a warmer simulated atmospheric boundary layer with respective local air temperature differences approaching similar to 2 degrees C. This study suggests that the retention of shortwave solar flux by ocean flora may directly impact even short-term forecasts of coastal meteorological variables. Citation: Jolliff, J. K., T. A. Smith, C. N. Barron, S. deRada, S. C. Anderson, R. W. Gould, and R. A. Arnone (2012), The impact of coastal phytoplankton blooms on ocean-atmosphere thermal energy exchange: Evidence from a two-way coupled numerical modeling system, Geophys. Res. Lett., 39, L24607, doi:10.1029/2012GL053634

KMT-2016-BLG-1107: A New Hollywood-Planet Close/Wide Degeneracy

We show that microlensing event KMT-2016-BLG-1107 displays a new type of degeneracy between wide-binary and close-binary Hollywood events in which a giant-star source envelops the planetary caustic. The planetary anomaly takes the form of a smooth, two-day "bump" far out on the falling wing of the light curve, which can be interpreted either as the source completely enveloping a minor-image caustic due to a close companion with mass ratio $q=0.036$, or partially enveloping a major-image caustic due to a wide companion with $q=0.004$. The best estimates of the companion masses are both in the planetary regime ($3.3^{+3.5}_{-1.8}\,M_{\rm jup}$ and $0.090^{+0.096}_{-0.037}\,M_{\rm jup}$) but differ by an even larger factor than the mass ratios due to different inferred host masses. We show that the two solutions can be distinguished by high-resolution imaging at first light on next-generation ("30m") telescopes. We provide analytic guidance to understand the conditions under which this new type of degeneracy can appear.Comment: 23 pages, 7 figures, accepted for publication in A

KMT-2018-BLG-1990Lb: A Nearby Jovian Planet From A Low-Cadence Microlensing Field

We report the discovery and characterization of KMT-2018-BLG-1990Lb, a Jovian planet $(m_p=0.57_{-0.25}^{+0.79}\,M_J)$ orbiting a late M dwarf $(M=0.14_{-0.06}^{+0.20}\,M_\odot)$, at a distance (D_L=1.23_{-0.43}^{+1.06}\,\kpc), and projected at $2.6\pm 0.6$ times the snow line distance, i.e., a_{\rm snow}\equiv 2.7\,\au (M/M_\odot), This is the second Jovian planet discovered by KMTNet in its low cadence ($0.4\,{\rm hr}^{-1}$) fields, demonstrating that this population will be well characterized based on survey-only microlensing data.Comment: 24 pages, 7 figures, 4 table

KELT-3b: A Hot Jupiter Transiting a V=9.8 Late-F Star

We report the discovery of KELT-3b, a moderately inflated transiting hot Jupiter with a mass of 1.477 (-0.067, +0.066) M_J, and radius of 1.345 +/- 0.072 R_J, with an orbital period of 2.7033904 +/- 0.000010 days. The host star, KELT-3, is a V=9.8 late F star with M_* = 1.278 (-0.061, +0.063) M_sun, R_* = 1.472 (-0.067, +0.065) R_sun, T_eff = 6306 (-49, +50) K, log(g) = 4.209 (-0.031, +0.033), and [Fe/H] = 0.044 (-0.082, +0.080), and has a likely proper motion companion. KELT-3b is the third transiting exoplanet discovered by the KELT survey, and is orbiting one of the 20 brightest known transiting planet host stars, making it a promising candidate for detailed characterization studies. Although we infer that KELT-3 is significantly evolved, a preliminary analysis of the stellar and orbital evolution of the system suggests that the planet has likely always received a level of incident flux above the empirically-identified threshold for radius inflation suggested by Demory & Seager (2011).Comment: 12 pages, 12 figures, accepted to Ap

Bats Use Magnetite to Detect the Earth's Magnetic Field

While the role of magnetic cues for compass orientation has been confirmed in numerous animals, the mechanism of detection is still debated. Two hypotheses have been proposed, one based on a light dependent mechanism, apparently used by birds and another based on a “compass organelle” containing the iron oxide particles magnetite (Fe3O4). Bats have recently been shown to use magnetic cues for compass orientation but the method by which they detect the Earth's magnetic field remains unknown. Here we use the classic “Kalmijn-Blakemore” pulse re-magnetization experiment, whereby the polarity of cellular magnetite is reversed. The results demonstrate that the big brown bat Eptesicus fuscus uses single domain magnetite to detect the Earths magnetic field and the response indicates a polarity based receptor. Polarity detection is a prerequisite for the use of magnetite as a compass and suggests that big brown bats use magnetite to detect the magnetic field as a compass. Our results indicate the possibility that sensory cells in bats contain freely rotating magnetite particles, which appears not to be the case in birds. It is crucial that the ultrastructure of the magnetite containing magnetoreceptors is described for our understanding of magnetoreception in animals