Bloom Events Research Articles

Analytical study on the steady-state thermal blooming effect of high-power ytterbium-doped fiber lasers propagating through the atmosphere.

Thermal blooming effect is one of the significant factors affecting the propagation performance of high-power ytterbium-doped fiber lasers (YDFLs) in the atmosphere. In this paper, two 20 kW YDFL systems with typical wavelengths (1070 nm and 1080 nm) are fabricated for propagation comparison experiments, which are used to investigate the thermal blooming effect induced by high-power YDFL propagation through the atmosphere. Under approximately the same laser system parameters (except wavelength) and atmospheric environment, the 1070 nm laser has better propagation characteristics than the 1080 nm laser. Due to the combined effect between the different central wavelengths of the two fiber lasers and the spectral broadening caused by output power scaling, the thermal blooming caused by the different absorptivity of water vapor molecules to the two fiber lasers is the main factor for the variation of the propagation properties. Through theoretical analysis and numerical calculation of factors affecting the thermal blooming effect, and considering the industrial manufacturing difficulty of YDFLs, a reasonable selection of fiber laser parameters can effectively improve atmospheric propagation performance and reduce manufacturing costs.

Harmful effects of cyanobacterial blooms in Lake Ludaš (Serbia) on Carassius gibelio tissues

Harmful effects of cyanobacterial blooms in Lake Ludaš (Serbia) on Carassius gibelio tissues

Bio-optical properties of South Brazil Bight coastal waters and implications for satellite chlorophyll-a concentration retrieval

ABSTRACT Retrieving chlorophyll-a concentration (Chla) from remote-sensing data is especially challenging in coastal regions because of the presence of other co-dominant optically significant constituents (OSCs). In this study, we characterize bio-optical variability at a fixed coastal time series station in the South Brazil Bight (SBB), the ANTARES-Ubatuba site (São Paulo, Brazil) from radiometric measurements and water sample analyses, and evaluate the performance of ocean colour (OC) algorithms for Chla retrieval. In situ Chla and the spectral absorption of phytoplankton (aph), detritus, and coloured dissolved organic matter (CDOM), as well as the above-water remote-sensing reflectance (Rrs) were obtained from 2004 to 2019 at a quasi-monthly sampling frequency. Chla exhibited high variability, with a standard deviation twice as large as the mean (1.0 ± 1.83 mg m−3), and values ranging from 0.18 mg m−3 up to 18.09 mg m−3 during episodic bloom events. CDOM was the dominant OSC contributing to the absorption coefficient at 443 nm all-year round, suggesting the influence of continental sources, even though the station is located at the external limit of the inner shelf (40 m). Two optical water types were defined: one composed mainly of ‘blue’ waters with lower concentrations of the OSCs and another of ‘green’ waters with higher concentrations of OSCs. Despite the CDOM spectral dominance, the empirical OCx performed reasonably well with a positive bias for both in situ (17–25%) and satellite (25–31%) Chla retrievals. The performance was slightly better using the 3-band OC3 algorithm by selecting the best band ratio with lower influence of CDM (CDOM + detritus) absorption (Rrs (490/555)). The main sources of uncertainty were caused by higher CDM proportions and phytoplankton-specific absorption, yielding positive biases on the OC3 retrievals. The results suggest that standard satellite products of Chla can be used (with some caution) to monitor and study the dynamics of the phytoplankton biomass within the region, knowing the expected uncertainties.

Urban Surface Thermal Runoff Generation Mechanism and Scenario Simulation

AbstractWhen precipitation happens in summer, the thermal runoff from impervious surfaces flow into urban lakes, causing the rise of the surface water temperature. Such a process eventually leads to the short‐term effects of cyanobacteria blooms in eutrophic lakes and the long‐term effects of changes in the structure and quantity of lake species. It is of great scientific significance to understand the heat exchange process between surface air, underlying surface, and surface runoff and reveal the thermal runoff formation mechanism. In this study, the heat transfer models between land, surface‐air, and surface‐water were implemented, aiming to quantify the heating process of surface runoff caused by surface heat load under real conditions. The results show that the two established models can accurately simulate the heat exchange process. Based on our model simulations and field measurements, we analyzed the impact of weather conditions, hydrological conditions, and underlying surface types on runoff temperature. The study finds that the initial surface temperature, wind speed, rainfall intensity, thermal conductivity, and the underlying surface's water permeability can explain 95.4% and 91.9% of the observed differences in surface runoff heating and temperature increase rate, respectively. The initial surface temperature is the most critical factor in the heat exchange process. The reduction of urban ventilation will aggravate the heat effect of surface runoff. Compared with the underlying permeable surface, the impervious surface is the main driving force for the formation of surface thermal runoff pollution.

The niche of a stress-tolerant specialist, Dinophysis acuminata, in a coastal upwelling system

Dinophysis acuminata, the main cause of shellfish harvesting bans in Europe, blooms in the Galician Rías (NW Spain) throughout the upwelling season (ca. March to September). Here we illustrate rapid changes in vertical and across ría-shelf distributions of diatoms and dinoflagellates (including D. acuminata vegetative and small cells) in Ría de Pontevedra (RP) and Ría de Vigo (RV) during transitions from spin-down to spin-up phases of upwelling cycles. A subniche approach based on a Within Outlying Mean Index (WitOMI) showed that under the transient environmental conditions met during the cruise, both vegetative and small cells of D. acuminata colonized the Ria and Mid-shelf subniches, exhibiting good tolerance and extremely high marginality, in particular the small cells. Bottom-up (abiotic) control overwhelmed biological constraints, and shelf waters became a more favourable environment than the Rías. Contrasting higher biotic constraints inside the Rías were found for the small cells, with a subniche possibly controlled by unsuitable physiological status (notwithstanding the higher density) of the vegetative cell population. Results here on behaviour (vertical positioning) and physiological traits (high tolerance but very specialized niche) of D. acuminata give new insights into the ability of this species to remain in the upwelling circulation system. Higher shelf-ría exchanges in the Ría (RP) with more dense and persistent D. acuminata blooms reveal the relevance of transient event-scales and species- and site-specific characteristics to the fate of these blooms. Earlier statements about simple linear relationships between average upwelling intensities and the recurrence of Harmful algae bloom (HAB) events in the Galician Rías Baixas are questioned.

Cyanobacterial bloom monitoring and assessment in Latin America

Cyanobacterial blooms have serious adverse effects on human and environmental health. In Latin America, one of the main world's freshwater reserves, information on this phenomenon remains sparse. To assess the current situation, we gathered reports of cyanobacterial blooms and associated cyanotoxins in freshwater bodies from South America and the Caribbean (Latitude 22° N to 45° S) and compiled the regulation and monitoring procedures implemented in each country. As the operational definition of what is a cyanobacterial bloom remains controversial, we also analyzed the criteria used to determine the phenomena in the region. From 2000 to 2019, blooms were reported in 295 water bodies distributed in 14 countries, including shallow and deep lakes, reservoirs, and rivers. Cyanotoxins were found in nine countries and high concentrations of microcystins were reported in all types of water bodies. Blooms were defined according to different, and sometimes arbitrary criteria including qualitative (changes in water color, scum presence), quantitative (abundance), or both. We found 13 different cell abundance thresholds defining bloom events, from 2 × 103 to 1 × 107 cells mL−1. The use of different criteria hampers the estimation of bloom occurrence, and consequently the associated risks and economic impacts. The large differences between countries in terms of number of studies, monitoring efforts, public access to the data and regulations regarding cyanobacteria and cyanotoxins highlights the need to rethink cyanobacterial bloom monitoring, seeking common criteria. General policies leading to solid frameworks based on defined criteria are needed to improve the assessment of cyanobacterial blooms in Latin America. This review represents a starting point toward common approaches for cyanobacterial monitoring and risk assessment, needed to improve regional environmental policies.

INVESTIGATING BLOOD LACTATE CONCENTRATION AS A PROGNOSTIC INDICATOR FOR BIRDS PRESENTING WITH BREVETOXICOSIS: 2020-2021.

Large blooms of the dinoflagellate Karenia brevis cause annual harmful algal bloom events, or "red tides" on Florida's Gulf Coast. Each year, the Clinic for the Rehabilitation of Wildlife (CROW) is presented with hundreds of cases of aquatic birds that exhibit neurologic clinical signs due to brevetoxicosis. Double-crested cormorants (Phalacrocorax auratus) are the most common species seen, and typically present with a combination of ataxia, head tremors, knuckling, and/or lagophthalmos. Blood lactate levels are known to increase in mammals for a variety of reasons, including stress, hypoxia, sepsis, and trauma, but there is limited literature on blood lactate values in avian species. The objective of this study was to determine the prognostic value of blood lactate concentration on successful rehabilitation and release of birds presenting with clinical signs consistent with brevetoxicosis. Blood lactate levels were collected on intake, the morning after presentation and initial therapy, and prior to disposition (release or euthanasia) from 194 birds (including 98 cormorants) representing 17 species during the 2020-2021 red tide season. Overall, mean blood lactate at intake, the morning after intake, and predisposition was 2.9, 2.8, and 3.2 mmol/L, respectively, for released birds across all species (2.9, 2.9, and 3.2 mmol/L for released cormorants); 3.4, 3.4, and 6.5 mmol/L for birds that died (4.0, 3.5, and 7.9 mmol/L for cormorants that died); and 3.1, 3.5, and 4.7 mmol/L for birds that were euthanized (3.5, 4.7, and 4.9 mmol/L for cormorants that were euthanized). On average, birds that died or were euthanized had an elevated lactate at all time points as compared to those that were released, but these results were not statistically significant (P = 0.13). These results indicate that blood lactate levels do not appear to be useful as a prognostic indicator for successful release of birds, including double-crested cormorants, affected by brevetoxicosis.

Field measurements of the carbon to chlorophyll-a ratio using Imaging FlowCytobot: Implications for dissolved oxygen modeling

In subtropical coastal waters around Hong Kong, dissolved oxygen (DO) can undergo significant diurnal changes (up to 40%–50% saturation) during algal blooms. The carbon to chlorophyll-a ratio (CCHL) – a key parameter in water quality models – is variable and depends on factors that include light intensity and temperature. Despite numerous laboratory and field investigations, the prediction of CCHL and DO during high productivity conditions remains a difficult problem; the CCHL during algal blooms has also not been measured.The phytoplankton and DO dynamics are studied in a semi-enclosed tidal inlet using a submerged Imaging FlowCytobot (IFCB) together with a real-time water quality monitoring system. A diurnal pattern of algal abundance is observed with peaks around 4pm. Based on carbon estimates from the bio-volumes of the algal images and direct measurements of chlorophyll-a, the CCHL ratio is monitored continuously during an algal bloom event. The CCHL is found to vary significantly over a bloom cycle—in the range of 10 to several hundred and generally much greater than the constant values (in the order of 10) assumed in industry standard water quality models. A first order theoretical estimate of the CCHL as a function of algal growth rate and light saturation intensity is supported by field data. Using a simple oxygen budget model, the diurnal DO changes during an algal bloom can be satisfactorily predicted by integrating IFCB data with water quality data. The findings help to improve environmental and ecosystem modeling and mariculture management.

Bacterial community (free-living vs particle-attached) assembly driven by environmental factors and a more stable network in the pre-bloom period than post-bloom

Cyanobacterial blooms are common phenomenon in freshwater ecosystems, influencing the composition and function of bacterioplankton communities. However, the drivers on the pattern and mechanism of bacterial community were still little known especially before and after bloom outbreak. Here, high-throughput sequencing of bacterial 16S rRNA gene was used to investigate the dynamics of communities with two lifestyles of free-living (FL, 0.22–3 μm) and particle-attached (PA, >3 μm) in the Lake Taihu, and co-occurrence patterns and assembly mechanism of bacteria were also explored between pre-bloom and post-bloom periods. The results exhibited that the bloom event significantly changed the composition and diversity of plankton community. Primarily, phyla of Proteobacteria, Actinobacteria and Bacteroidetes were dominated in FL bacteria, whereas Proteobacteria, Cyanobacteria and Bacteroidetes were distributed in PA bacteria. Additionally, PA bacteria had higher α-diversity than FL bacteria in two periods. Co-occurrence network analysis revealed that the network was more complex interactions in the pre-bloom than post-bloom. Null-model analysis indicated homogeneous selection was the key assembly process in the pre-bloom, while stochastic processes played predominant role in the post-bloom. Moreover, abiotic factors were significantly correlated with keystone taxa to further reveal the deterministic process in the pre-bloom (p < 0.05). Overall, these findings indicate the ecological network and assembly mechanisms of bacteria driven by environmental factors (especially ORP, Nitrogen related concentrations, and Chla) in the pre-bloom more than post-bloom in a changing aquatic niche.

Cyanobacteria Index as a Tool for the Satellite Detection of Cyanobacteria Blooms in the Baltic Sea

Cyanobacteria blooms in the Baltic Sea have been studied for years due to their toxicity, which negatively affects all biota, along with the influence of these floating colonies on surface fluxes. However, mapping these blooms is still a challenge since their high dynamics, wide coverage, and specific radiometric footprint hinder atmospheric correction and negatively affect the quality of satellite images. In this study, we assessed the use of an alternative approach called the cyanobacteria index (CI), which is based on the reflectance spectral shape and which does not require comprehensive atmospheric correction. We demonstrated a close relationship between the positive CI values, indicating the presence of blooms, and the concentration of phycocyanin, the marker pigment of filamentous cyanobacteria in the Baltic Sea. We proved that the CI index could efficiently identify cyanobacteria-dominated blooms where colonies floated near the surface. Therefore, this index represents a valuable complement to the previous monitoring methods, suitable for extreme bloom events. The analysis of a time series of satellite images obtained between 2002 and 2018 using the CI index revealed the elongation of the bloom season, which may have been a consequence of the water temperature remaining within the cyanobacteria’s tolerance range for a longer time.

Effect of Iron Availability on the Growth and Microcystin Content of Natural Populations of Microcystis spp. from Reservoirs in Central Argentina: A Microcosm Experiment Approach

The eutrophication of aquatic systems is a problem related to the contribution of excess nutrients—phosphorus (P) and nitrogen (N)—to water bodies, which produces an increase in cyanobacterial blooms. Under eutrophic conditions, P and N concentrations are sufficient for cyanobacteria growth, and some micronutrients are considered to become limiting for population growth. This work aimed to assess the effect of iron on cyanobacteria growth and the content of MCs in natural populations of Microcystis spp. Microcosm setting experiments were carried out with natural samples collected during two bloom events of Microcystis spp., kept under controlled light, temperature and pH conditions. The first bloom sample was exposed to different iron concentrations (400, 700 and 1100 µg Fe·L−1) to determine the optimum concentration for growth. The second was exposed to different iron addition modes (one: T1P, and two pulses: T2P) to imitate the iron increase produced by the downward migration of Microcystis spp. colonies. Our results show that iron is a growth-promoting factor and that its optimal range of concentrations for the growth of Microcystis spp. under the experimental setting conditions is between 700 and 1100 µg Fe·L−1. On the other hand, growth rates were not significantly different between T1P and T2P; thus, different addition modes did not have an effect on growth. Regarding microcystin content, the MC quota in natural populations of Microcystis spp. did not show a clear relationship with the iron supply. This work contributes to the understanding of the underlying factors affecting cyanobacteria bloom formation and the production of MCs, which in turn would impact the development of management strategies to control cyanobacteria blooms.

Cyanobacterial Blooms Increase Functional Diversity of Metazooplankton in a Shallow Eutrophic Lake

Harmful cyanobacterial blooms disrupt aquatic ecosystem processes and biological functions. However, studies focusing on the effect of cyanobacterial blooms on the functional diversity of consumers are still insufficient. To examine the interactions of cyanobacterial blooms and the diversity and composition of metazooplankton, we investigated the variation in metazooplankton and their driven variables during the cyanobacterial bloom and non-bloom periods in 2020 and 2021 in Lake Xingkai. We found that cyanobacterial blooms reduced the metazooplankton species diversity but increased their biomass, functional dispersion, and functional evenness. Generalized additive mixed model results revealed that cyanobacteria showed different effects on metazooplankton biodiversity and functional diversity during the bloom and non-bloom periods. Variance partitioning analysis indicated that cyanobacteria, physicochemical variables, and temporal variation explained 15.93% of the variation in metazooplankton during the bloom period and 20.27% during the non-bloom periods. Notably, cyanobacteria during the bloom period explained more variations in metazooplankton composition than those during the non-bloom period. Our results suggest that cyanobacterial blooms significantly impact the functional diversity and community composition of metazooplankton. Physicochemical and spatiotemporal factors may mask the effects of cyanobacteria on metazooplankton. Our findings may improve the understanding of the dynamics and responses of metazooplankton communities to environmental changes and cyanobacterial blooms disturbances and enhance our ability to assess the effectiveness of aquatic ecosystem restoration and eutrophication management.

Laser Beam Jitter Control Based on a LabVIEW FPGA Control System

The thermal blooming effect, platform jitter, and other effects of laser beam propagation cause serious deviation, which will have a negative impact on laser tracking systems. It is important to ensure that the laser beam does not deviate. Based on a fast steering mirror, a CMOS camera, and a Flex RIO system, a laser beam jitter control system is designed and implemented. The error is detected by camera and compensated for by the fast steering mirror (FSM), which is controlled by the Flex RIO device. By using LabVIEW and MATLAB, a closed loop model is realized. The results show that the system response is highly stabilized and has a short rise time, providing a reference for engineering applications.

Metagenomic mapping of cyanobacteria and potential cyanotoxin producing taxa in large rivers of the United States

Cyanobacteria and cyanotoxin producing cyanobacterial blooms are a trending focus of current research. Many studies focus on bloom events in lentic environments such as lakes or ponds. Comparatively few studies have explored lotic environments and fewer still have examined the cyanobacterial communities and potential cyanotoxin producers during ambient, non-bloom conditions. Here we used a metagenomics-based approach to profile non-bloom microbial communities and cyanobacteria in 12 major U.S. rivers at multiple time points during the summer months of 2019. Our data show that U.S. rivers possess microbial communities that are taxonomically rich, yet largely consistent across geographic location and time. Within these communities, cyanobacteria often comprise significant portions and frequently include multiple species with known cyanotoxin producing strains. We further characterized these potential cyanotoxin producing taxa by deep sequencing amplicons of the microcystin E (mcyE) gene. We found that rivers containing the highest levels of potential cyanotoxin producing cyanobacteria consistently possess taxa with the genetic potential for cyanotoxin production and that, among these taxa, the predominant genus of origin for the mcyE gene is Microcystis. Combined, these data provide a unique perspective on cyanobacteria and potential cyanotoxin producing taxa that exist in large rivers across the U.S. and can be used to better understand the ambient conditions that may precede bloom events in lotic freshwater ecosystems.

In situ digital holographic microscopy for rapid detection and monitoring of the harmful dinoflagellate, Karenia brevis

Karenia brevis blooms, also known as red tide, are a recurring problem in the coastal Gulf of Mexico. These blooms have the capacity to inflict substantial damage to human and animal health as well as local economies. Thus, monitoring and detection of K. brevis blooms at all life stages and cell concentrations is essential for ensuring public safety. Current K. brevis monitoring methods have several limitations, including size resolution limits and concentration ranges, limited capacity for spatial and temporal profiling, and/or small sample volume processing. Here, a novel monitoring method wherein an autonomous digital holographic imaging microscope (AUTOHOLO), that overcomes these limitations and can characterize K. brevis concentrations in situ, is presented. Using the AUTOHOLO, in situ field measurements were conducted in the coastal Gulf of Mexico during an active K. brevis bloom over the 2020–21 winter season. Surface and sub-surface water samples collected during these field studies were also analyzed in the lab using benchtop holographic imaging and flow cytometry for validation. A convolutional neural network was trained for automated classification of K. brevis at all concentration ranges. The network was validated with manual counts and flow cytometry, yielding a 90% accuracy across diverse datasets with varying K. brevis concentrations. The usefulness of pairing the AUTOHOLO with a towing system was also demonstrated for characterizing particle abundance over large spatial distances, which could potentially facilitate characterization of spatial distributions of K. brevis during bloom events. Future applications of the AUTOHOLO can include integration into existing HAB monitoring networks to enhance detection capabilities for K. brevis in aquatic environments around the world.

Spatio-temporal changes of winter and spring phytoplankton blooms in Arabian sea during the period 1997–2020

Arabian Sea (AS) experiences Chlorophyll-a (Chl-a) blooms during winter and early spring (November–March) mainly due to the changes induced by seasonally reversing monsoon winds and associated processes. The seasonal blooms exhibit distinct regional patterns in their onset, duration, intensity and peak period. Recent changes in ocean dynamics and plankton composition have inflicted adverse effects in the distribution of Chl-a concentration in AS. Here, we analyse the long-term spatio-temporal changes in winter and early spring bloom events during the period 1997–2020, and evaluate the role of sea surface temperature (SST), mixed layer depth (MLD), sea surface salinity, winds, mesoscale eddies and surface currents on these bloom occurrences. We observe a significant reduction in these blooms, which started in the early 2000s and intensified in the last decade (2010–2020), with a notable drop in the adjacent gulfs (Gulf of Aden: 1.38 ± 0.7 × 10−5 mg m−3 yr−1, Gulf of Oman: 4.71 ± 1.35 × 10−6 mg m−3 yr−1) and West coast of India (−6.71 ± 2.85 × 10−6 mg m−3 yr−1). The MLD and ocean temperature are the major factors that govern bloom in Gulf of Oman and open waters. Conversely, the coastal upwelling and eddies drive blooms in Gulf of Aden. The winter cooling trigger the bloom in the northern Indian west coast, but the inter-basin exchange of surface waters through the West Indian Coastal Current inhibits its southward spread. This study, therefore, reveals unique processes that initiate and control the winter and early spring blooms in different regions of AS. The ongoing warming of AS could contribute to further decline in these seasonal blooms, which would be a great concern for regional marine productivity and associated regional food security.

Remotely sensed-based analysis about climatic and landscape change effects on phytoplankton bloom in Barra Bonita Reservoir (São Paulo State, Brazil)

The constant land use and land cover (LULC) changes combined with climatic factors are frequently assigned to anthropogenic eutrophication, one of the main ecological imbalances in aquatic systems characterized by dense phytoplankton proliferation. Beyond the degradation of freshwater ecosystems, some cyanobacterial and algae species produce toxins harmful to living beings. Distinct studies in the literature, usually supported by in situ data, have discussed the influence of LULC and climatic changes on phytoplankton bloom events. In this context, motivated by the importance of understanding the environmental mechanisms assigned to phytoplankton bloom events and considering the difficulties imposed by field data collection, our study focuses on analyzing the mentioned issue only using remotely sensed time series data. For this purpose, we performed a temporal analysis between 1985 and 2018 over a portion of the Barra Bonita Hydroelectric Reservoir, Brazil. Initially, we obtained the landscape occupation, precipitation, and temperature information from the MapBiomas, FLDAS, and CHIRPS projects, respectively. A fully automatic algorithm fed by Landsat image series and supported by Google Earth Engine functions was developed and employed to identify and quantify phytoplankton bloom events. Then, the obtained data were inspected by distinct statistical procedures, including correlation and trend analysis. Although there was an absence of a relationship between the climatic components and the emergence of phytoplankton blooms, it was identified using linear regression models (R2 ≥ 78 % ) an intensification of blooms after the increase in nonnatural forestry areas, reduction of pastures, and advance of agricultural areas. Furthermore, machine learning methods were employed to obtain nonlinear regression models (R2 ≥ 73 % ), making evident that the landscape changes are mainly responsible for the phytoplankton insurgences in the analyzed region. This result agrees with other studies found in the literature and highlights the possibility of investigating anthropogenic eutrophication only using remotely sensed data and automatic algorithms.

Toxicity-mediated regime shifts in a contaminated nutrient-plankton system.

In this article, we contemplate the dynamics of a three-tier system of nutrient, phytoplankton, and zooplankton with a gestation delay of discrete type and a distributed delay in nutrient recycling. Phytoplankton secretion-mediated alteration in the grazing pattern of zooplankton is encapsulated by a Monod-Haldane functional response. We carry out global sensitivity analysis for identifying the crucial model parameters having a significant impact on zooplankton density. The system potentially exhibits bistable configurations under identical ecological conditions by allowing different bifurcation scenarios, including multiple saddle-node and transcritical bifurcations with varying input rates of nutrients and inhibitory effects of phytoplankton against zooplankton. We observe that the gestation delay in zooplankton is responsible for the emergence of noxious bloom events. Interestingly, when the delay parameter crosses a threshold, the system experiences chaotic disorder, which prognosticates the onset of irregular bloom. Furthermore, by adding Gaussian white noise, we have extended the deterministic model to its stochastic counterpart. We found that white noise appears to regulate the survival and extinction of interacting populations. Comprehensive numerical simulations are consistent with mathematical results prognosticated by linear analysis.

The biogeochemistry of zinc and cadmium in the Amundsen Sea, coastal Antarctica

The trace metals zinc (Zn) and cadmium (Cd) are both involved in the metabolic processes of marine phytoplankton, and as such, both metals play important roles in ocean biogeochemical cycles. In Antarctica, the Amundsen Sea (AS) experiences rapid ice shelf melting, and the Amundsen Sea polynya (ASP) hosts seasonal phytoplankton blooms in austral summer, with important implications for atmospheric carbon dioxide drawdown. However, the effects of ice melting and phytoplankton blooms on the biogeochemistry and distributions of Zn and Cd in the ASP remain poorly studied. Here, we present the first combined dataset of dissolved and particulate Zn and Cd in the AS (including the inflow and outflow to and from the Dotson and Getz ice shelves) collected as part of the GEOTRACES process study GPpr12. We use this dataset to assess the sources of both elements to the AS region and characterize the particle composition in the ASP. We find that the main source of both dissolved Zn and Cd in the AS is Circumpolar Deep Water (CDW), with an additional small flux of both metals from shelf sediments. By contrast, aerosol deposition, ice shelf melt, and sea ice melt are all deemed insignificant sources for either Zn or Cd in the AS. Labile particulate Zn and Cd dominate the total particulate pool in the surface layer, indicating that biological uptake is a predominant process for the cycling of both metals in the ASP, whereas sediment resuspension and ice shelf melt do not supply a significant amount of either particulate Zn or Cd. Additionally, we use two commonly used approaches to estimate biogenic and lithogenic particulate concentrations. We find high biogenic particulate concentrations at the surface, decreasing with depth, indicating remineralization plays an important role in the cycling of particulate metals. In contrast, lithogenic particulate metal concentrations remain low throughout the water column. We also show that the estimated uptake ratios of Zn and Cd relative to phosphate in the surface layer are lower than reported for the open Southern Ocean, likely related to the spatial and temporal variability of Fe in the AS. Overall, these new observations provide insight into the biogeochemistry of both Zn and Cd in the AS, a region that is subject to the influence of rapid climate change, which may have implications for the larger-scale cycling of trace metals in the Southern Ocean. Specifically, the amount of Zn and Cd supplied to the surface ASP will increase, given that the volume of CDW that flows towards the Dotson Ice Shelf is predicted to increase.

Effects of bloom’s mastery learning model based on CBRN preparedness program on learning skills of nursing students: A randomized controlled trial

BackgroundExposure to chemical, biological, radiological and nuclear (CBRN) threats and hazards can have fatal or disabling consequences. One of the most risky groups in terms of secondary contamination in CBRN exposure is healthcare workers. Nurses need to have several competencies to be able to respond correctly to people exposed to CBRN agents and to protect themselves from secondary contamination. AimThis study aimed to investigate the effectiveness of a Bloom’s Mastery Learning Model-based Chemical, Biological, Radiological, Nuclear Threat and Hazards Preparedness Program for nursing students (MLM-CBRN Preparedness Program) as a means for improving knowledge, attitudes, self-efficacy and skills. DesignA parallel-group trial design was used. MethodsA total of 104 4th-year nursing students were randomized into intervention and control groups. The data from the participants were collected before the intervention, immediately after the intervention and in the 1st and 3rd months after the intervention. ResultsAfter the intervention, a significant difference was observed between the groups in terms of knowledge, attitude and self-efficacy scores. It was seen that there was a significant difference between the pre-intervention measurement (1st measurement) and the 2nd, 3rd and 4th measurements (Table 2). This was due to the increasing scores of the intervention group (p < 0.05). ConclusionsIt shows that the MLM-CBRN Preparedness Program is effective in increasing the knowledge, attitude, self-efficacy and skill development of student nurses about CBRN threats and dangers.