Nitrogen and phosphorus limitation of oceanic microbial growth during spring in the Gulf of Aqaba

Bioassay experiments were performed to identify how growth of key groups within the microbial community was simultaneously limited by nutrient (nitrogen and phosphorus) availability during spring in the Gulf of Aqaba's oceanic waters. Measurements of chlorophyll a (chl a) concentration and fast repetition rate (FRR) fluorescence generally demonstrated that growth of obligate phototrophic phytoplankton was co-limited by N and P and growth of facultative aerobic anoxygenic photoheterotropic (AAP) bacteria was limited by N. Phytoplankton exhibited an increase in chl a biomass over 24 to 48 h upon relief of nutrient limitation. This response coincided with an increase in photosystem II (PSII) photochemical efficiency (F v /F m), but was preceded (within 24 h) by a decrease in effective absorption crosssection (σPSII) and electron turnover time (τ). A similar response for τ and bacterio-chl a was observed for the AAPs. Consistent with the up-regulation of PSII activity with FRR fluorescence were observations of newly synthesized PSII reaction centers via low temperature (77K) fluorescence spectroscopy for addition of N (and N + P). Flow cytometry revealed that the chl a and thus FRR fluorescence responses were partly driven by the picophytoplankton (æ10 μm) community, and in particular Synechococcus. Productivity of obligate heterotrophic bacteria exhibited the greatest increase in response to a natural (deep water) treatment, but only a small increase in response to N and P addition, demonstrating the importance of additional substrates (most likely dissolved organic carbon) in moderating the heterotrophs. These data support previous observations that the microbial community response (autotrophy relative to heterotrophy) is critically dependent upon the nature of transient nutrient enrichment. © Inter-Research 2009

A global atlas of artificial light at night under the sea

The impacts of artificial light at night (ALAN) on marine ecosystems have emerged as a focus for ecological light pollution research in recent years, yet the global prevalence of ALAN in underwater marine ecosystems is unknown. We have derived a global atlas of ALAN throughout the marine water column that will accelerate our understanding of its sources and environmental impacts. At a depth of 1 m, 1.9 million km2 of the world’s coastal seas are exposed to biologically important ALAN, which equates to around 3.1% of the global exclusive economic zones.This area decreases to 1.6 million km2 (2.7%) at a depth of 10 m, and to 840,000 km2 (1.4%) at 20 m.The most heavily exposed regions are those that experience intensive offshore development in addition to coastal urbanization.The atlas highlights that ALAN as a global change issue is not exclusive to land but is also widespread in the world’s underwater habitats at irradiances that elicit biological responses in marine organisms

Freezing of gait and fall detection in Parkinson’s disease using wearable sensors:a systematic review

Despite the large number of studies that have investigated the use of wearable sensors to detect gait disturbances such as Freezing of gait (FOG) and falls, there is little consensus regarding appropriate methodologies for how to optimally apply such devices. Here, an overview of the use of wearable systems to assess FOG and falls in Parkinson’s disease (PD) and validation performance is presented. A systematic search in the PubMed and Web of Science databases was performed using a group of concept key words. The final search was performed in January 2017, and articles were selected based upon a set of eligibility criteria. In total, 27 articles were selected. Of those, 23 related to FOG and 4 to falls. FOG studies were performed in either laboratory or home settings, with sample sizes ranging from 1 PD up to 48 PD presenting Hoehn and Yahr stage from 2 to 4. The shin was the most common sensor location and accelerometer was the most frequently used sensor type. Validity measures ranged from 73–100% for sensitivity and 67–100% for specificity. Falls and fall risk studies were all home-based, including samples sizes of 1 PD up to 107 PD, mostly using one sensor containing accelerometers, worn at various body locations. Despite the promising validation initiatives reported in these studies, they were all performed in relatively small sample sizes, and there was a significant variability in outcomes measured and results reported. Given these limitations, the validation of sensor-derived assessments of PD features would benefit from more focused research efforts, increased collaboration among researchers, aligning data collection protocols, and sharing data sets

Combined effect of nutrient and flashing light frequency for a biochemical composition shift in Nannochloropsis gaditana grown in a quasi-isoactinic reactor

Artificial lighting may be an interesting opportunity for the cultivation of microalgae as an alternative to natural sunlight. In particular, light emitting diodes (LEDs) can be employed to tailor the lighting to the microalgal culture in a controlled mode in order to create flashing light. In order to establish the effect of the flashing frequency on growth and biochemical composition of a model microalga, a quasi-isoactinic reactor, in which the light distribution is almost homogeneous, was set up. In this work, it was employed for the cultivation of the heterokont Nannochloropsis gaditana in two growth media with limiting and nonlimiting nutrients. The combined effect of nutrient concentration and flashing frequency on the growth, lipid content, fatty acid content, and pigment content was assessed for the first time. The results indicate that both nutrient concentration and flashing frequency influence the above-mentioned parameters. In particular, under flashing light conditions, an increase of lipid content and a decrease of polyunsaturated fatty acids (PUFAs) and chlorophyll are observed when nutrients are deficient, while the opposite effects are shown when nutrients are abundant