Spring phytoplankton communities of the Labrador Sea (2005–2014): pigment signatures, photophysiology and elemental ratios

The Labrador Sea is an ideal region to study the biogeographical, physiological, and biogeochemical implications of phytoplankton community composition due to sharp transitions between distinct water masses across its shelves and central basin. We have investigated the multi-year (2005–2014) distributions of late spring and early summer (May to June) phytoplankton communities in the various hydrographic settings of the Labrador Sea. Our analysis is based on pigment markers (using CHEMTAX analysis), and photophysiological and biogeochemical characteristics associated with each phytoplankton community. Diatoms were the most abundant group, blooming first in shallow mixed layers of haline-stratified Arctic shelf waters. Along with diatoms, chlorophytes co-dominated at the western end of the section (particularly in the polar waters of the Labrador Current (LC)), whilst Phaeocystis co-dominated in the east (modified polar waters of the West Greenland Current (WGC)). Pre-bloom conditions occurred in deeper mixed layers of the central Labrador Sea in May, where a mixed assemblage of flagellates (dinoflagellates, prasinophytes, prymnesiophytes, particularly coccolithophores, and chrysophytes/pelagophytes) occurred in low-chlorophyll areas, succeeding to blooms of diatoms and dinoflagellates in thermally stratified Atlantic waters in June. Light-saturated photosynthetic rates and saturation irradiance levels were highest at stations where diatoms were the dominant phytoplankton group ( >  70 % of total chlorophyll a), as opposed to stations where flagellates were more abundant (from 40 up to 70 % of total chlorophyll a). Phytoplankton communities from the WGC (Phaeocystis and diatoms) had lower light-limited photosynthetic rates, with little evidence of photoinhibition, indicating greater tolerance to a high light environment. By contrast, communities from the central Labrador Sea (dinoflagellates and diatoms), which bloomed later in the season (June), appeared to be more sensitive to high light levels. Ratios of accessory pigments (AP) to total chlorophyll a (TChl a) varied according to phytoplankton community composition, with polar phytoplankton (cold-water related) having lower AP  :  TChl a. Polar waters (LC and WGC) also had higher and more variable particulate organic carbon (POC) to particulate organic nitrogen (PON) ratios, suggesting the influence of detritus from freshwater input, derived from riverine, glacial, and/or sea ice meltwater. Long-term observational shifts in phytoplankton communities were not assessed in this study due to the short temporal frame (May to June) of the data. Nevertheless, these results add to our current understanding of phytoplankton group distribution, as well as an evaluation of the biogeochemical role (in terms of C  :  N ratios) of spring phytoplankton communities in the Labrador Sea, which will assist our understanding of potential long-term responses of phytoplankton communities in high-latitude oceans to a changing climate

Biogeographical patterns and environmental controls of phytoplankton communities from contrasting hydrographical zones of the Labrador Sea

The Labrador Sea is an important oceanic sink for atmospheric CO2 because of intensive convective mixing during winter and extensive phytoplankton blooms that occur during spring and summer. Therefore, a broad-scale investigation of the responses of phytoplankton community composition to environmental forcing is essential for understanding planktonic food-web organisation and biogeochemical functioning in the Labrador Sea. Here, we investigated the phytoplankton community structure (>4 μm) from near surface blooms (1.2 mg chla m−3) occurred on and near the shelves in May and in offshore waters of the central Labrador Sea in June due to haline- and thermal-stratification, respectively. Sea ice-related (Fragilariopsis cylindrus and F. oceanica) and Arctic diatoms (Fossula arctica, Bacterosira bathyomphala and Thalassiosira hyalina) dominated the relatively cold (<0 °C) and fresh (salinity < 33) waters over the Labrador shelf (e.g., on the southwestern side of the Labrador Sea), where sea-ice melt and Arctic outflow predominates. On the northeastern side of the Labrador Sea, intense blooms of the colonial prymnesiophyte Phaeocystis pouchetii and diatoms, such as Thalassiosira nordenskioeldii, Pseudo-nitzschia granii and Chaetoceros socialis, occurred in the lower nutrient waters (nitrate < 3.6 μM) of the West Greenland Current. The central Labrador Sea bloom occurred later in the season (June) and was dominated by Atlantic diatoms, such as Ephemera planamembranacea and Fragilariopsis atlantica. The data presented here demonstrate that the Labrador Sea spring and early summer blooms are composed of contrasting phytoplankton communities, for which taxonomic segregation appears to be controlled by the physical and biogeochemical characteristics of the dominant water masses

Home–school differences in beliefs, support, and control during public pre-kindergarten and their link to children's kindergarten readiness

This study examines the prevalence of home-school match in child-rearing beliefs and socialization practices (control and support) and their relation to ethnicity and readiness skills of children (n=310) making the transition from publicly sponsored pre-k to kindergarten. Home-school match was operationalized both as a continuous absolute measure and as categories of match or mismatch. Overall, home-school match was more prevalent than mismatch. However, the results corroborate previous ethnographic studies showing higher rates of home-school mismatch among African Americans and Latinos than Euro Americans. Controlling for race and socioeconomic status, parents‘ beliefs and practices predicted readiness but teachers‘ did not. Absolute indicators of home-school differences were not related to kindergarten readiness. Directional indicators revealed that children attained greater skills when parents and teachers matched on child-centered beliefs, low control, and high support. Contrary to the cultural match hypothesis, home-school mismatch was associated with better outcomes than match in the case of adult-centered beliefs, control, and low support

Environmental enteric dysfunction includes a broad spectrum of inflammatory responses and epithelial repair processes

Background & AimsEnvironmental enteric dysfunction (EED), a chronic diffuse inflammation of the small intestine, is associated with stunting in children in the developing world. The pathobiology of EED is poorly understood because of the lack of a method to elucidate the host response. This study tested a novel microarray method to overcome limitation of RNA sequencing to interrogate the host transcriptome in feces in Malawian children with EED.MethodsIn 259 children, EED was measured by lactulose permeability (%L). After isolating low copy numbers of host messenger RNA, the transcriptome was reliably and reproducibly profiled, validated by polymerase chain reaction. Messenger RNA copy number then was correlated with %L and differential expression in EED. The transcripts identified were mapped to biological pathways and processes. The children studied had a range of %L values, consistent with a spectrum of EED from none to severe.ResultsWe identified 12 transcripts associated with the severity of EED, including chemokines that stimulate T-cell proliferation, Fc fragments of multiple immunoglobulin families, interferon-induced proteins, activators of neutrophils and B cells, and mediators that dampen cellular responses to hormones. EED-associated transcripts mapped to pathways related to cell adhesion, and responses to a broad spectrum of viral, bacterial, and parasitic microbes. Several mucins, regulatory factors, and protein kinases associated with the maintenance of the mucous layer were expressed less in children with EED than in normal children.ConclusionsEED represents the activation of diverse elements of the immune system and is associated with widespread intestinal barrier disruption. Differentially expressed transcripts, appropriately enumerated, should be explored as potential biomarkers

Predictors of Ventriculostomy Infection in a Large Cohort

Introduction: External ventricular drains (EVDs) are neurosurgical devices used to treat hydrocephalus and monitor intracranial pressure. Ventriculostomy-associated infections (VAIs) are a complication of EVD placement associated with increased morbidity and mortality, as well as cost. A previous study at Jefferson reported a decrease in VAI’s with the use of antibiotic-coated catheters. Objective: The aim of this study was to assess the current rate of VAI’s and determine risk factors associated with infections. Methods: Using Epic, the electronic medical records software, we conducted a retrospective review of patients who underwent EVD placement at Thomas Jefferson University Hospital and Jefferson Hospital for Neuroscience between January 2010 and January 2018. Results: During this time period, 1107 EVD’s were placed in 1034 patients. The most common indications for placement were acute subarachnoid hemorrhage (51%), intraparenchymal hemorrhage (15.4%), and brain tumors (9.7%). 38 patients suffered from a VAI, for an infection rate of 0.03%. Patients with VAI’s had a significantly longer duration of EVD placement (19.4 vs. 11.1 days). Risk factors for VAI included CSF leak (OR 2.35), EVD placement greater than 11 days (OR 2.14), and concurrent infection (OR 1.74). There was no association with patient age, sex, initial diagnosis, drain replacement, number of samples drawn, or prophylactic antibiotics. Discussion: Despite the use of antibiotic-coated catheters, VAI’s still remain a prevalent complication of EVD placement. By working to prevent CSF leaks, minimize the duration of EVD placement, and appropriately treat concurrent infections, it may be possible to further lower VAI rates

Diatom Biogeography From the Labrador Sea Revealed Through a Trait-Based Approach

Diatoms are a keystone algal group, with diverse cell morphology and a global distribution. The biogeography of morphological, functional, and life-history traits of marine diatoms were investigated in Arctic and Atlantic waters of the Labrador Sea during the spring bloom (2013-2014). In this study, trait-based analysis using community-weighted means showed that low temperatures (< 0°C) in Arctic waters correlated positively with diatom species that have traits such as low temperature optimum growth and the ability to produced ice-binding proteins, highlighting their sea ice origin. High silicate concentrations in Arctic waters, as well as sea ice cover and shallow bathymetry, favoured diatom species that were heavily silicified, colonial and capable of producing resting spores, suggesting that these are important traits for this community. In Atlantic waters, diatom species with large surface area to volume ratios were dominant in deep mixed layers, whilst low silicate to nitrate ratios correlated positively with weakly silicified species. Sharp cell projections, such as processes or spines, were positively correlated with water-column stratification, indicating that these traits promote positive buoyancy for diatom cells. Our trait-based analysis directly links cell morphology and physiology with diatom species distribution, allowing new insights on how this method can potentially be applied to explain ecophysiology and shifting biogeographical distributions in a warming climate

The North Atlantic Ocean as habitat for Calanus finmarchicus : environmental factors and life history traits

This paper addresses relationships between the distribution and abundance of zooplankton and its habitat in the northern North Atlantic Ocean. Distributions of ten representative zooplankton taxa, from recent (2000-2009) Continuous Plankton Recorder data, are presented, along with basin-scale patterns of annual sea surface temperature and phytoplankton color. The distribution patterns represent the manifestation of very different physiological, life history and ecological interactions of each taxon with the North Atlantic habitat characteristics. The paper then focuses on a pan-Atlantic compilation of demographic and life history information for the planktonic copepod, Calanus finmarchicus, perhaps one of the most ecologically important and certainly the most studied zooplankton species in the North Atlantic. Abundance, dormancy, egg production and mortality in relation to temperature and phytoplankton biomass, using chlorophyll a as a proxy, are analyzed in the context of understanding factors involved in determining the distribution and abundance of C. finmarchicus across its range. Several themes emerge: (1) transport of C. finmarchicus is from the south to the north in the northeast Atlantic, but from the north to the south in the western North Atlantic, which has implications for understanding population responses to climate forcing on coastal shelves, , (2) recruitment to the youngest copepodite stages occurs during or just after the phytoplankton bloom in the east while it occurs after the bloom in many western sites, (3) while the deep basins in the Labrador Sea and Norwegian Sea are primary sources of C. finmarchicus production, the western North Atlantic marginal seas have an important role in sustaining high C. finmarchicus abundance on the western North Atlantic shelves, (4) differences in mean temperature and chlorophyll concentration between the western and eastern North Atlantic are reflected in regional differences in female body size and egg production responses, (5) differences in functional responses in egg production rate may reflect genetic differences between western and eastern populations, (6) dormancy duration is generally shorter in the deep waters adjacent to the lower latitude western North Atlantic shelves than in the east, and (7) differences in stage-specific mortality rates are related to bathymetry, temperature and potential predators, notably the abundance of congeners Calanus hyperboreus and C. glacialis, which likely feed on early life stages of C. finmarchicus. Two modeling approaches have previously been used to interpret the abundance and distribution of C. finmarchicus in relation to the North Atlantic habitat. A statistical approach based on ecological niche theory and a dynamical modeling approach, based on knowledge of spatial population dynamics and life history and implemented by recent developments in coupled physical-life cycle modeling. The strengths and weaknesses of each approach are discussed. A synthesis of the two modeling approaches to predict North Atlantic zooplankton species shifts, not only for C. finmarchicus, but also for other major taxa, is advocated. While the computational resource requirements and lack of species-specific life history information for physical-biological modeling hinder full application for many zooplankton taxa, use of the approach, where possible, to understand advective influences will provide insight for interpretation of statistical predictions from species distribution models

Biogeography of key mesozooplankton species in the North Atlantic and egg production of Calanus finmarchicus

-Here we present a new, pan-North-Atlantic compilation of data on key mesozooplankton species, including the most important copepod, Calanus finmarchicus. Distributional data of eight representative zooplankton taxa, from recent (2000–2009) Continuous Plankton Recorder data, are presented, along with basin-scale data of the phytoplankton colour index. Then we present a compilation of data on C. finmarchicus, including observations of abundance, demography, egg production and female size, with accompanying data on temperature and chlorophyll

Remote climate forcing of decadal-scale regime shifts in Northwest Atlantic shelf ecosystems

Author Posting. © Association for the Sciences of Limnology and Oceanography, 2013. This article is posted here by permission of Association for the Sciences of Limnology and Oceanography for personal use, not for redistribution. The definitive version was published in Association for the Sciences of Limnology and Oceanography, doi:10.4319/lo.2013.58.3.0803.Decadal-scale regime shifts in Northwest Atlantic shelf ecosystems can be remotely forced by climate-associated atmosphere–ocean interactions in the North Atlantic and Arctic Ocean Basins. This remote climate forcing is mediated primarily by basin- and hemispheric-scale changes in ocean circulation. We review and synthesize results from process-oriented field studies and retrospective analyses of time-series data to document the linkages between climate, ocean circulation, and ecosystem dynamics. Bottom-up forcing associated with climate plays a prominent role in the dynamics of these ecosystems, comparable in importance to that of top-down forcing associated with commercial fishing. A broad perspective, one encompassing the effects of basin- and hemispheric-scale climate processes on marine ecosystems, will be critical to the sustainable management of marine living resources in the Northwest Atlantic.Funding for this research was provided by the National Science Foundation as part of the Regional and Pan-Regional Synthesis Phases of the U.S. Global Ocean Ecosystem (GLOBEC) Program

Recent Arctic climate change and its remote forcing of Northwest Atlantic shelf ecosystems

Author Posting. © The Oceanography Society, 2012. This article is posted here by permission of The Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 25, no. 3 (2012): 208-213, doi:10.5670/oceanog.2012.64.During recent decades, historically unprecedented changes have been observed in the Arctic as climate warming has increased precipitation, river discharge, and glacial as well as sea-ice melting. Additionally, shifts in the Arctic's atmospheric pressure field have altered surface winds, ocean circulation, and freshwater storage in the Beaufort Gyre. These processes have resulted in variable patterns of freshwater export from the Arctic Ocean, including the emergence of great salinity anomalies propagating throughout the North Atlantic. Here, we link these variable patterns of freshwater export from the Arctic Ocean to the regime shifts observed in Northwest Atlantic shelf ecosystems. Specifically, we hypothesize that the corresponding salinity anomalies, both negative and positive, alter the timing and extent of water-column stratification, thereby impacting the production and seasonal cycles of phytoplankton, zooplankton, and higher-trophic-level consumers. Should this hypothesis hold up to critical evaluation, it has the potential to fundamentally alter our current understanding of the processes forcing the dynamics of Northwest Atlantic shelf ecosystems.Funding for this research was provided by the National Science Foundation as part of the Regional and Pan-Regional Synthesis Phases of the US Global Ocean Ecosystem (GLOBEC) Program