66 research outputs found
Environmental controls, oceanography and population dynamics of pathogens and harmful algal blooms: connecting sources to human exposure
© 2008 Author et al. This is an open access article distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Environmental Health 7 (2008): S5, doi:10.1186/1476-069X-7-S2-S5.Coupled physical-biological models are capable of linking the complex interactions between environmental factors and physical hydrodynamics to simulate the growth, toxicity and transport of infectious pathogens and harmful algal blooms (HABs). Such simulations can be used to assess and predict the impact of pathogens and HABs on human health. Given the widespread and increasing reliance of coastal communities on aquatic systems for drinking water, seafood and recreation, such predictions are critical for making informed resource management decisions. Here we identify three challenges to making this connection between pathogens/HABs and human health: predicting concentrations and toxicity; identifying the spatial and temporal scales of population and ecosystem interactions; and applying the understanding of population dynamics of pathogens/HABs to management strategies. We elaborate on the need to meet each of these challenges, describe how modeling approaches can be used and discuss strategies for moving forward in addressing these challenges.The authors acknowledge the financial support for the NSF/NIEHS and
NOAA Centers for Oceans and Human Healt
Transcriptomic response of the red tide dinoflagellate, Karenia brevis, to nitrogen and phosphorus depletion and addition
<p>Abstract</p> <p>Background</p> <p>The role of coastal nutrient sources in the persistence of <it>Karenia brevis </it>red tides in coastal waters of Florida is a contentious issue that warrants investigation into the regulation of nutrient responses in this dinoflagellate. In other phytoplankton studied, nutrient status is reflected by the expression levels of N- and P-responsive gene transcripts. In dinoflagellates, however, many processes are regulated post-transcriptionally. All nuclear encoded gene transcripts studied to date possess a 5' <it>trans</it>-spliced leader (SL) sequence suggestive, based on the trypanosome model, of post-transcriptional regulation. The current study therefore sought to determine if the transcriptome of <it>K. brevis </it>is responsive to nitrogen and phosphorus and is informative of nutrient status.</p> <p>Results</p> <p>Microarray analysis of N-depleted <it>K. brevis </it>cultures revealed an increase in the expression of transcripts involved in N-assimilation (nitrate and ammonium transporters, glutamine synthetases) relative to nutrient replete cells. In contrast, a transcriptional signal of P-starvation was not apparent despite evidence of P-starvation based on their rapid growth response to P-addition. To study transcriptome responses to nutrient addition, the limiting nutrient was added to depleted cells and changes in global gene expression were assessed over the first 48 hours following nutrient addition. Both N- and P-addition resulted in significant changes in approximately 4% of genes on the microarray, using a significance cutoff of 1.7-fold and p †10<sup>-4</sup>. By far, the earliest responding genes were dominated in both nutrient treatments by pentatricopeptide repeat (PPR) proteins, which increased in expression up to 3-fold by 1 h following nutrient addition. PPR proteins are nuclear encoded proteins involved in chloroplast and mitochondria RNA processing. Correspondingly, other functions enriched in response to both nutrients were photosystem and ribosomal genes.</p> <p>Conclusions</p> <p>Microarray analysis provided transcriptomic evidence for N- but not P-limitation in <it>K. brevis</it>. Transcriptomic responses to the addition of either N or P suggest a concerted program leading to the reactivation of chloroplast functions. Even the earliest responding PPR protein transcripts possess a 5' SL sequence that suggests post-transcriptional control. Given the current state of knowledge of dinoflagellate gene regulation, it is currently unclear how these rapid changes in such transcript levels are achieved.</p
The Changing Landscape for Stroke\ua0Prevention in AF: Findings From the GLORIA-AF Registry Phase 2
Background GLORIA-AF (Global Registry on Long-Term Oral Antithrombotic Treatment in Patients with Atrial Fibrillation) is a prospective, global registry program describing antithrombotic treatment patterns in patients with newly diagnosed nonvalvular atrial fibrillation at risk of stroke. Phase 2 began when dabigatran, the first non\u2013vitamin K antagonist oral anticoagulant (NOAC), became available. Objectives This study sought to describe phase 2 baseline data and compare these with the pre-NOAC era collected during phase 1. Methods During phase 2, 15,641 consenting patients were enrolled (November 2011 to December 2014); 15,092 were eligible. This pre-specified cross-sectional analysis describes eligible patients\u2019 baseline characteristics. Atrial fibrillation disease characteristics, medical outcomes, and concomitant diseases and medications were collected. Data were analyzed using descriptive statistics. Results Of the total patients, 45.5% were female; median age was 71 (interquartile range: 64, 78) years. Patients were from Europe (47.1%), North America (22.5%), Asia (20.3%), Latin America (6.0%), and the Middle East/Africa (4.0%). Most had high stroke risk (CHA2DS2-VASc [Congestive heart failure, Hypertension, Age 6575 years, Diabetes mellitus, previous Stroke, Vascular disease, Age 65 to 74 years, Sex category] score 652; 86.1%); 13.9% had moderate risk (CHA2DS2-VASc = 1). Overall, 79.9% received oral anticoagulants, of whom 47.6% received NOAC and 32.3% vitamin K antagonists (VKA); 12.1% received antiplatelet agents; 7.8% received no antithrombotic treatment. For comparison, the proportion of phase 1 patients (of N = 1,063 all eligible) prescribed VKA was 32.8%, acetylsalicylic acid 41.7%, and no therapy 20.2%. In Europe in phase 2, treatment with NOAC was more common than VKA (52.3% and 37.8%, respectively); 6.0% of patients received antiplatelet treatment; and 3.8% received no antithrombotic treatment. In North America, 52.1%, 26.2%, and 14.0% of patients received NOAC, VKA, and antiplatelet drugs, respectively; 7.5% received no antithrombotic treatment. NOAC use was less common in Asia (27.7%), where 27.5% of patients received VKA, 25.0% antiplatelet drugs, and 19.8% no antithrombotic treatment. Conclusions The baseline data from GLORIA-AF phase 2 demonstrate that in newly diagnosed nonvalvular atrial fibrillation patients, NOAC have been highly adopted into practice, becoming more frequently prescribed than VKA in Europe and North America. Worldwide, however, a large proportion of patients remain undertreated, particularly in Asia and North America. (Global Registry on Long-Term Oral Antithrombotic Treatment in Patients With Atrial Fibrillation [GLORIA-AF]; NCT01468701
Net community production and dark community respiration in a Karenia brevis (Davis) bloom in West Florida coastal waters, USA
Oxygen-based productivity and respiration rates were determined in West Florida coastal waters to evaluate the proportion of community respiration demands met by autotrophic production within a harmful algal bloom dominated by
Karenia brevis. The field program was adaptive in that sampling during the 2006 bloom occurred where surveys by the Florida Wildlife Research Institute indicated locations with high cell abundances. Net community production (NCP) rates from light-dark bottle incubations during the bloom ranged from 10 to 42
ÎŒmole
O
2
L
â1
day
â1 with highest rates in bloom waters where abundances exceeded 10
5
cells
L
â1. Community dark respiration (
R) rates in dark bottles ranged from <10 to 70
ÎŒmole
O
2
L
â1
day
â1 over 24
h. Gross primary production derived from the sum of NCP and
R varied from ca. 20 to 120
ÎŒmole
O
2
L
â1
day
â1. The proportion of GPP attributed to NCP varied with the magnitude of
R during day and night periods. Most surface communities exhibited net autotrophic production (NCP
>
R) over 24
h, although heterotrophy (NCP
<
R) characterized the densest sample where
K. brevis cell densities exceed 10
6
cells
L
â1
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The fate of upwelled waters in the Great Whirl, August 1995
The Great Whirl is a large, anticyclonic gyre that develops off the northern Somali coast during the Southwest Monsoon. In August 1995 the NOAA Ship
Malcolm Baldrige surveyed the seaward edge of the upwelling zone associated with this gyre. The fate of recently upwelled water was followed by mapping surface property distributions along a cool surface feature that extended seaward along the northern edge of the Great Whirl. Surface properties (
T,
S, and chlorophyll
a), surface velocity (ADCP), and XBT and CTD casts were interpreted in relation to the trajectories of three instrumented surface drifters deployed in the feature. Cool surface waters correspond in space to the shoaling of the upper thermocline and offshore advection from the coast. Surface chlorophyll
a concentrations decreased from 2 to 3
ÎŒg
l
â1 in the upwelling zone to 0.5â1.5
ÎŒg
l
â1 in the surface feature and contiguous waters. Maximum surface velocities in the Great Whirl were 250
cm
s
â1 with velocities> 100
cm
s
â1 along the northern perimeter of the gyre. Decorrelation time-scales for
u and
v velocity components, and chlorophyll
a fluorescence, from the drifters were on the order of 4 to 7 days. These times are comparable to those over which the drifters were ejected from the Great Whirl into the Socotra Gyre. Decorrelation times for sea-surface temperature were somewhat longer (10 days). All three platforms passed between the Somali coast and Socotra within a week of their deployment and then traveled east into the northern Arabian Sea
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Seasonal variations in the phytoplankton biomass and productivity of a warm-core Gulf Stream ring
Phytoplankton biomass, as chlorophyll
a (Chl
a) and ATP, and carbon productivity rates were determined in three cruises to a warm-core Gulf Stream ring. Ring 82B was formed in late February 1982 with observations made in April to May, June and August. Vertical profiles of Chl
a, ATP and particulate organic carbon (POC) in April to May showed little vertical structure during a period when the ring mixed layer extended from the surface to
>350
m
. Daily productivity rates, Chl
a and ATP biomass estimates of the euphotic zone were similar to those in the source waters, the Sargasso Sea, but lower than those in contiguous Slope Waters. Despite the absence of a stratified surface layer in the ring, the phytoplankton productivity rates, assimilation numbers, and carbon-specific growth rates were relatively high. In June, a pycnocline existed at 25 m across the ring with biomass maxima of Chl
a, ATP, and POC occurring near the seasonal pycnocline. Although the range in productivity in June (0.26 to 0.98 gC m
â2 day
â1) was similar to that in April, the carbon biomass estimated from ATP increased from 1.42 to 4.77 gC m
â2 between the two cruises. The increase was partially attributed to an increased heterotrophic biomass. Carbon-specific specific doubling times in June were, most likely, influenced by the presence of a large heterotrophic ATP component. In August the surface layer of the ring was displaced by intrusions, or overwash, of Slope and Gulf Stream waters. During the 6 month lifespan of 82B total primary production was estimated at 126 gC m
â2, a value similar to productivity estimates for the contiguous Slope Waters
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Mesoscale pigment fields in the Gulf Stream: Observations in a meander crest and trough
In SeptemberâOctober 1988 and April 1989 a series of hydrographic transects were completed across the Gulf Stream front in a meander crest and meander trough, respectively. One of the main experimental objectives was to relate the spatial distribution of chlorophyll to the physical fields of Gulf Stream meanders. Chlorophyll distributions are derived from conductivityâtemperatureâdepth (CTD)/fluorescence profiles calibrated with discrete pigment samples collected from bottles at several depths at various stations. Objective analysis (OA) maps and vertical sections, in stream coordinates, of chlorophyll on density surfaces show the chlorophyll distribution was strongly related to the structure of the Gulf Stream front. In particular, chlorophyll concentrations greater than 0.4 mg mâ3 were at, or inshore of, the Gulf Stream north wall. Characteristic length scales of chlorophyll distribution determined from the horizontal and temporal correlation function are the same order (50â100 km) as length scales of the physical variables. The maximum chlorophyll concentrations in the vertical were from the surface to 50âm depth on the western flank of the meander crest and deepened to 75â to 100âm depth on the eastern flank. This coincides with the deepening of the 24.4â25.7 ÏΞ surfaces from the western to the eastern flank of the meander crest. Although in the spring cruise the maximum chlorophyll concentrations were also found at depths between the surface and 100 m, there were no clear distinctions in pigment distributions between the western and eastern transects of a relatively weak trough. Maximum chlorophyll concentrations, 1.0â1.5 mg mâ3, from the 1989 spring bloom in slope waters were about double those observed in the 1988 fall data. The primary physical mechanisms influencing the mesoscale pigment distribution in Gulf Stream meanders observed in this study are (1) outcropping of nutrientâbearing strata in the spring, (2) meanderâinduced upwelling of nutrients along sloping isopycnals, and (3) Gulf Streamâring interactions
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Influence of monsoonally-forced Ekman dynamics upon surface layer depth and plankton biomass distribution in the Arabian Sea
Oceanic surface layer properties in the central Arabian Sea at the height of the northeast 1986, 1987 and southwest 1987 monsoons are described. Data from two research cruises on the R.R.S.
Charles Darwin are combined with Comprehensive OceanâAtmosphere Data Set (COADS) winds and a simple model to consider the influence of the monsoons on the surface layers of the Arabian Sea. In December 1986 (NE monsoon) the top of the thermocline was fairly uniform with a mean depth of approximately 60 m. In contrast, this depth varied with latitude in the SW monsoon, with the shallowest depths occurring under the region of maximum winds and the maximum depths to the south of the monsoon jet. This situation is tied to the Ekman flow which leads to open ocean upwelling to the north of the wind maximum, thus suppressing the development of the mixed layer. The thermocline to the south is deepened by a combination of Ekman pumping and advection of dense fluid from the north. A simple two-dimensional model incorporating a non-penetrative mixed layer and a slab Ekman layer flow is used to examine the factors involved in the evolution of the surface layers during the monsoons. The combination of upwelling and surface layer deepening leads to latitudinal gradients in phytoplankton biomass. The major effect in the SW monsoon is the upwelling induced by Ekman dynamics and a consequent shoaling of the nitracline in the northern Arabian Sea. Vertical mixing and the associated deepening of the surface layer dominate phytoplankton distributions in the NE monsoons
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A Lagrangian view of fluorescent chromophoric dissolved organic matter distributions in the Mississippi River plume
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