779 research outputs found
Biophysical coupling between turbulence, veliger behavior, and larval supply
Submitted in partial fulfillment of the requirements for the degree of
Doctor of Philosophy
at the
Massachusetts Institute of Technology
and the
Woods Hole Oceanographic Institution
September 2005The goals of this thesis were to quantify the behavior of gastropod larvae (mud snails
Ryanassa obsoleta) in turbulence, and to investigate how that behavior affects larval supply
in a turbulent coastal inlet. Gastropod larvae retract their velums and sink rapidly in
strong turbulence. Turbulence-induced sinking would be an adaptive behavior if it resulted
in increased larval supply and enhanced settlement in suitable coastal habitats.
In laboratory experiments, mud snail larvae were found to have three behavioral modes:
swimming, hovering, and sinking. The proportion of sinking larvae increased exponentially
with the turbulence dissipation rate over a range comparable to turbulence in a tidal inlet,
and the mean larval vertical velocity shifted from upward to downward in turbulence
resembling energetic nearshore areas.
The larval response to turbulence was incorporated in a vertical advection-diffusion
model to characterize the effects of this behavior on larval supply and settlement in a tidal
channel. Compared to passive larvae, larvae that sink in turbulence have higher near-bed
concentrations throughout flood and ebb tides. This high larval supply enables behaving
larvae to settle more successfully than passive larvae in strong currents characteristic of
turbulent tidal inlets.
A study was conducted at Barnstable Harbor, MA to estimate the responses of larvae
to turbulence in the field. Gastropod larvae from different coastal environments had
genus-specific responses to turbulence, suggesting that larvae use turbulence for large-scale
habitat selection. On ebb tides, mud snail larvae had a similar response to turbulence as
in the laboratory, with greater sinking velocities in strong turbulence. Behavior estimates
differed for flood and ebb tides, indicating that additional physical cues influence behavior.
Turbulence-induced sinking behavior would enhance retention and promote settlement of
mud snail larvae in habitats like Barnstable Harbor.Financial support was provided by a National Science Foundation Graduate Research
Fellowship, the WHOI Academic Programs Office, a WHOI Coastal Ocean: Institute grant,
a WHOI Mellon independent study grant to L. S. Mullineaux and M; G. Neubert, a Sea
Grant New Initiative grant (Grant No. NA16RG2273, project no. R/O-38-PD), the WHOI
Biology department, and the Rinehart Coastal Research Center
Recommended from our members
CALCULATING AVERAGE HOT WATER MIXES OF RESIDENTIAL PLUMBING FITTINGS Using the ANSI 301-2019 Hot Water Draw Model and National Residential Data to Estimate Hot Water Use in Showerheads and Lavatory Faucets
Biophysical coupling between turbulence, veliger behavior, and larval supply
Thesis (Ph. D.)--Joint Program in Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Biology; and the Woods Hole Oceanographic Institution), 2005.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Includes bibliographical references.The goals of this thesis were to quantify the behavior of gastropod larvae (mud snails Ilyanassa obsoleta) in turbulence, and to investigate how that behavior affects larval supply in a turbulent coastal inlet. Gastropod larvae retract their velums and sink rapidly in strong turbulence. Turbulence-induced sinking would be an adaptive behavior if it resulted in increased larval supply and enhanced settlement in suitable coastal habitats. In laboratory experiments, mud snail larvae were found to have three behavioral modes: swimming, hovering, and sinking. The proportion of sinking larvae increased exponentially with the turbulence dissipation rate over a range comparable to turbulence in a tidal inlet, and the mean larval vertical velocity shifted from upward to downward in turbulence resembling energetic nearshore areas. The larval response to turbulence was incorporated in a vertical advection-diffusion model to characterize the effects of this behavior on larval supply and settlement in a tidal channel. Compared to passive larvae, larvae that sink in turbulence have higher near-bed concentrations throughout flood and ebb tides.(cont.) This high larval supply enables behaving larvae to settle more successfully than passive larvae in strong currents characteristic of turbulent tidal inlets. A study was conducted at Barnstable Harbor, MA to estimate the responses of larvae to turbulence in the field. Gastropod larvae from different coastal environments had genus-specific responses to turbulence, suggesting that larvae use turbulence for large-scale habitat selection. On ebb tides, mud snail larvae had a similar response to turbulence as in the laboratory, with greater sinking velocities in strong turbulence. Behavior estimates differed for flood and ebb tides, indicating that additional physical cues influence behavior. Turbulence-induced sinking behavior would enhance retention and promote settlement of mud snail larvae in habitats like Barnstable Harbor.by Heidi L. Fuchs.Ph.D
Larval responses to turbulence and temperature in a tidal inlet: Habitat selection by dispersing gastropods?
Author Posting. © Sears Foundation for Marine Research, 2010. This article is posted here by permission of Sears Foundation for Marine Research for personal use, not for redistribution. The definitive version was published in Journal of Marine Research 68 (2010): 153-188, doi:10.1357/002224010793079013.Marine larval dispersal is affected by hydrodynamic transport and larval behavior, but little is known about how behavior affects large-scale patterns of dispersal and recruitment. Intertidal habitats are characterized by strong and variable turbulence relative to shelf and pelagic waters, so larval responses to turbulence may affect both dispersal and habitat selection. This study combined observations and theoretical approaches to model gastropod larval responses to multiple physical variables in a well-mixed tidal inlet. Physical measurements and larvae were collected in July 2004 in Barnstable Harbor, Massachusetts (USA). Physical measurements were incorporated in an advection-diffusion model where larval vertical velocity is a function of turbulence dissipation rate, temperature, and the temperature gradient. Modeled larval distributions were fitted to observed concentration profiles by maximum likelihood to estimate larval behavioral velocity (swimming or sinking) as a function of environmental conditions. These quantitative behavior estimates were used to test hypotheses about behavioral differences among groups and to assess the relative impact of different cues on overall larval behavior. Larvae of five common gastropod species from different coastal habitats reacted most strongly to turbulence but had genus-specific responses to environmental cues. Larvae of a species from tidal inlets (the mud snail Nassarius obsoletus) had near-zero velocities under calmer conditions and sank in strong turbulence. In contrast, larvae from exposed beach habitats (Crepidula spp. and Anachis spp.) sank in weak turbulence and swam up in strong turbulence, with additional responses to temperature and temperature gradient. Larval responses also differed between small and large size classes and between flood and ebb tides. Behavior of mud snail larvae would contribute to retention inside the inlet and near adult habitats, whereas behavior of beach snail larvae would contribute to rapid export from muddy inlets lacking suitable adult habitats.This work was funded by the Woods Hole Oceanographic Institution (WHOI) Coastal Ocean
Institute, the WHOI Rinehart Coastal Research Center, the National Science Foundation (NSF OCE-
0326734), NSF and US Office of Naval Research grants to S. Elgar and B. Raubenheimer, and the
WHOI Sea Grant (National Oceanic and Atmospheric Administration, Grant No. NA16RG2273,
project no. R/O-38-PD). Analyses were completed while HLF was a postdoctoral scholar at Scripps
Institution of Oceanography (SIO), supported by the California Current Ecosystem Long-Term Ecological
Research program (NSF OCE-0417616) and by SIO funding to P. Franks
Processed data from Particle Imaging Velocimetry (PIV) observations of Tritia trivittata and Tritia obsoleta behavior in various flow tanks
Dataset: Snail larvae in turbulence and wavesDispersing marine larvae can alter their physical transport by swimming vertically or sinking in response to environmental signals. However, it remains unknown whether any signals could enable larvae to navigate over large scales. We tested whether flow-induced larval behaviors vary with adults' physical environments using congeneric snail larvae from the wavy continental shelf (Tritia trivittata) and from turbulent inlets (Tritia obsoleta). This dataset includes observations of larvae in turbulence, in rotating flows dominated by vorticity or strain rates, and in rectilinear wave oscillations. Larval and water motion were observed using near-infrared particle image velocimetry (IR PIV), and analyses identified threshold signals causing larvae to change their direction or magnitude of propulsive force. The two species reacted similarly to turbulence but differently to waves, and their transport patterns would diverge in wavy, offshore regions. Wave-induced behaviors provide evidence that larvae may detect waves as both motions and sounds useful in navigation. For a complete list of measurements, refer to the supplemental document 'Field_names.pdf', and a full dataset description is included in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: http://www.bco-dmo.org/dataset/739790NSF Division of Ocean Sciences (NSF OCE) OCE-106062
Delirium screening in an acute care setting with a machine learning classifier based on routinely collected nursing data: A model development study
Delirium screening in acute care settings is a resource intensive process with frequent deviations from screening protocols. A predictive model relying only on daily collected nursing data for delirium screening could expand the populations covered by such screening programs. Here, we present the results of the development and validation of a series of machine-learning based delirium prediction models. For this purpose, we used data of all patients 18 years or older which were hospitalized for more than a day between January 1, 2014, and December 31, 2018, at a single tertiary teaching hospital in Zurich, Switzerland. A total of 48,840 patients met inclusion criteria. 18,873 (38.6%) were excluded due to missing data. Mean age (SD) of the included 29,967 patients was 71.1 (12.2) years and 12,231 (40.8%) were women. Delirium was assessed with the Delirium Observation Scale (DOS) with a total score of 3 or greater indicating that a patient is at risk for delirium. Additional measures included structured data collected for nursing process planning and demographic characteristics. The performance of the machine learning models was assessed using the area under the receiver operating characteristic curve (AUC). The training set consisted of 21,147 patients (mean age 71.1 (12.1) years; 8,630 (40.8%) women|) including 233,024 observations with 16,167 (6.9%) positive DOS screens. The test set comprised 8,820 patients (median age 71.1 (12.4) years; 3,601 (40.8%) women) with 91,026 observations with 5,445 (6.0%) positive DOS screens. Overall, the gradient boosting machine model performed best with an AUC of 0.933 (95% CI, 0.929 - 0.936). In conclusion, machine learning models based only on structured nursing data can reliably predict patients at risk for delirium in an acute care setting. Prediction models, using existing data collection processes, could reduce the resources required for delirium screening procedures in clinical practice
Joint eQTL assessment of whole blood and dura mater tissue from individuals with Chiari type I malformation
The Milky Way Tomography with SDSS: III. Stellar Kinematics
We study Milky Way kinematics using a sample of 18.8 million main-sequence
stars with r<20 and proper-motion measurements derived from SDSS and POSS
astrometry, including ~170,000 stars with radial-velocity measurements from the
SDSS spectroscopic survey. Distances to stars are determined using a
photometric parallax relation, covering a distance range from ~100 pc to 10 kpc
over a quarter of the sky at high Galactic latitudes (|b|>20 degrees). We find
that in the region defined by 1 kpc <Z< 5 kpc and 3 kpc <R< 13 kpc, the
rotational velocity for disk stars smoothly decreases, and all three components
of the velocity dispersion increase, with distance from the Galactic plane. In
contrast, the velocity ellipsoid for halo stars is aligned with a spherical
coordinate system and appears to be spatially invariant within the probed
volume. The velocity distribution of nearby ( kpc) K/M stars is complex,
and cannot be described by a standard Schwarzschild ellipsoid. For stars in a
distance-limited subsample of stars (<100 pc), we detect a multimodal velocity
distribution consistent with that seen by HIPPARCOS. This strong
non-Gaussianity significantly affects the measurements of the velocity
ellipsoid tilt and vertex deviation when using the Schwarzschild approximation.
We develop and test a simple descriptive model for the overall kinematic
behavior that captures these features over most of the probed volume, and can
be used to search for substructure in kinematic and metallicity space. We use
this model to predict further improvements in kinematic mapping of the Galaxy
expected from Gaia and LSST.Comment: 90 pages, 26 figures, submitted to Ap
Temperate infection in a virus–host system previously known for virulent dynamics
The blooming cosmopolitan coccolithophore Emiliania huxleyi and its viruses (EhVs) are a model for density-dependent virulent dynamics. EhVs commonly exhibit rapid viral reproduction and drive host death in high-density laboratory cultures and mesocosms that simulate blooms. Here we show that this system exhibits physiology-dependent temperate dynamics at environmentally relevant E. huxleyi host densities rather than virulent dynamics, with viruses switching from a long-term non-lethal temperate phase in healthy hosts to a lethal lytic stage as host cells become physiologically stressed. Using this system as a model for temperate infection dynamics, we present a template to diagnose temperate infection in other virus–host systems by integrating experimental, theoretical, and environmental approaches. Finding temperate dynamics in such an established virulent host–virus model system indicates that temperateness may be more pervasive than previously considered, and that the role of viruses in bloom formation and decline may be governed by host physiology rather than by host–virus densities
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