Osmotrophic glucose and leucine assimilation and its impact on EPA and DHA content in algae

The uptake of dissolved organic compounds, that is, osmotrophy, has been shown to be an efficient nutritional strategy for algae. However, this mode of nutrition may affect the biochemical composition, for example, the fatty acid (FA) contents, of algal cells. This study focused on the osmotrophic assimilation of glucose and leucine by selected seven algal strains belonging to chlorophytes, chrysophytes, cryptophytes, dinoflagellates and euglenoids. Our laboratory experiments with stable isotope labeling showed that osmotrophy occurred in four of the selected seven strains. However, only three of these produced long chain omega-3 FAs eicosapentaenoic acid (EPA; 20:5 omega 3) and docosahexaenoic acid (DHA; 22:6 omega 3). High glucose content (5 mg L-1) affected negatively on the total FAs of Mallomonas kalinae and the total omega-3 FAs of Cryptomonas sp. Further, glucose assimilation explained 35% (negative effect) and leucine assimilation 48% (positive effect) of the variation of EPA, DHA and the FAs related to their synthesis in Cryptomonas sp. Moderate glucose concentration (2 mg L-1) was found to enhance the growth of Cryptomonas ozolinii, whereas low leucine (20 mu g L-1) enhanced the growth of M. kalinae. However, no systematic effect of osmotrophy on growth rates was detected. Our study shows that osmotrophic assimilation of algae is species and compound specific, and that the effects of the assimilated compounds on algal metabolism also varies depending on the species.Peer reviewe

Lake zooplankton delta C-13 values are strongly correlated with the delta C-13 values of distinct phytoplankton taxa

Analyses of carbon stable isotopes are often used to estimate the contributions of allochthonous and autochthonous dietary resources to aquatic consumers. Most pelagic food web studies assume that all phytoplankton taxa have a similar delta C-13 value. We studied pelagic food web compartments (dissolved inorganic carbon [DIC], phytoplankton, bacteria, seston, cladoceran zooplankton) in 12 small (<0.1 km(2)) lakes in southern Finland. These lakes were classified as oligotrophic, mesotrophic, eutrophic, and dystrophic based on their concentrations of total phosphorus and dissolved organic carbon. Additionally, we studied phytoplankton photosynthetic carbon fractionation (epsilon(p)) in laboratory conditions. The photosynthetic fractionation in 28 phytoplankton cultures from nine different phytoplankton classes varied significantly at the class level, and fractionation correlated significantly with the DIC concentration of the growth media. In small boreal lakes, the delta C-13 values of different phytoplankton taxa, as directly measured or estimated from the delta C-13 values of biomarker fatty acids, varied greatly (-18 parts per thousand to - 44.5 parts per thousand). Phytoplankton delta C-13 values varied significantly by lake type and were most depleted in dystrophic lakes even though the delta C-13 values of the DIC was similar to mesotrophic lakes. Further within-taxa variation was found between lakes and between different depths within a lake. Vertical samples from dystrophic lakes also showed lower ep in the phytoplankton from meta-and hypolimnion, possibly as a result of reduced light intensity. Altogether, in nine of the 10 sampled lakes, the delta C-13 values of cladoceran zooplankton were between the minimum and the maximum phytoplankton delta C-13 value of each lake, and thus, phytoplankton alone could explain zooplankton delta C-13 values. We conclude that stable isotope mixing models should take into account carbon variation among different phytoplankton taxa.Peer reviewe

Inferring Phytoplankton, Terrestrial Plant and Bacteria Bulk delta C-13 Values from Compound Specific Analyses of Lipids and Fatty Acids

Stable isotope mixing models in aquatic ecology require delta C-13 values for food web end members such as phytoplankton and bacteria, however it is rarely possible to measure these directly. Hence there is a critical need for improved methods for estimating the delta C-13 ratios of phytoplankton, bacteria and terrestrial detritus from within mixed seston. We determined the delta C-13 values of lipids, phospholipids and biomarker fatty acids and used these to calculate isotopic differences compared to the whole-cell delta C-13 values for eight phytoplankton classes, five bacterial taxa, and three types of terrestrial organic matter (two trees and one grass). The lipid content was higher amongst the phytoplankton (9.5 +/- 4.0%) than bacteria (7.3 +/- 0.8%) or terrestrial matter (3.9 +/- 1.7%). Our measurements revealed that the delta C-13 values of lipids followed phylogenetic classification among phytoplankton (78.2% of variance was explained by class), bacteria and terrestrial matter, and there was a strong correlation between the delta C-13 values of total lipids, phospholipids and individual fatty acids. Amongst the phytoplankton, the isotopic difference between biomarker fatty acids and bulk biomass averaged -10.7 +/- 1.1 parts per thousand for Chlorophyceae and Cyanophyceae, and -6.1 +/- 1.7 parts per thousand for Cryptophyceae, Chrysophyceae and Diatomophyceae. For heterotrophic bacteria and for type I and type II methane-oxidizing bacteria our results showed a -1.3 +/- 1.3 parts per thousand, -8.0 +/- 4.4 parts per thousand, and -3.4 +/- 1.4 parts per thousand delta C-13 difference, respectively, between biomarker fatty acids and bulk biomass. For terrestrial matter the isotopic difference averaged -6.6 +/- 1.2 parts per thousand. Based on these results, the delta C-13 values of total lipids and biomarker fatty acids can be used to determine the delta C-13 values of bulk phytoplankton, bacteria or terrestrial matter with +/- 1.4 parts per thousand uncertainty (i.e., the pooled SD of the isotopic difference for all samples). We conclude that when compound-specific stable isotope analyses become more widely available, the determination of delta C-13 values for selected biomarker fatty acids coupled with established isotopic differences, offers a promising way to determine taxa-specific bulk delta C-13 values for the phytoplankton, bacteria, and terrestrial detritus embedded within mixed seston.Peer reviewe

Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

Funder: European Society of Intensive Care Medicine; doi: http://dx.doi.org/10.13039/501100013347Funder: Flemish Society for Critical Care NursesAbstract: Purpose: Intensive care unit (ICU) patients are particularly susceptible to developing pressure injuries. Epidemiologic data is however unavailable. We aimed to provide an international picture of the extent of pressure injuries and factors associated with ICU-acquired pressure injuries in adult ICU patients. Methods: International 1-day point-prevalence study; follow-up for outcome assessment until hospital discharge (maximum 12 weeks). Factors associated with ICU-acquired pressure injury and hospital mortality were assessed by generalised linear mixed-effects regression analysis. Results: Data from 13,254 patients in 1117 ICUs (90 countries) revealed 6747 pressure injuries; 3997 (59.2%) were ICU-acquired. Overall prevalence was 26.6% (95% confidence interval [CI] 25.9–27.3). ICU-acquired prevalence was 16.2% (95% CI 15.6–16.8). Sacrum (37%) and heels (19.5%) were most affected. Factors independently associated with ICU-acquired pressure injuries were older age, male sex, being underweight, emergency surgery, higher Simplified Acute Physiology Score II, Braden score 3 days, comorbidities (chronic obstructive pulmonary disease, immunodeficiency), organ support (renal replacement, mechanical ventilation on ICU admission), and being in a low or lower-middle income-economy. Gradually increasing associations with mortality were identified for increasing severity of pressure injury: stage I (odds ratio [OR] 1.5; 95% CI 1.2–1.8), stage II (OR 1.6; 95% CI 1.4–1.9), and stage III or worse (OR 2.8; 95% CI 2.3–3.3). Conclusion: Pressure injuries are common in adult ICU patients. ICU-acquired pressure injuries are associated with mainly intrinsic factors and mortality. Optimal care standards, increased awareness, appropriate resource allocation, and further research into optimal prevention are pivotal to tackle this important patient safety threat

Correction to: Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

The original version of this article unfortunately contained a mistake

Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

Funder: European Society of Intensive Care Medicine; doi: http://dx.doi.org/10.13039/501100013347Funder: Flemish Society for Critical Care NursesAbstract: Purpose: Intensive care unit (ICU) patients are particularly susceptible to developing pressure injuries. Epidemiologic data is however unavailable. We aimed to provide an international picture of the extent of pressure injuries and factors associated with ICU-acquired pressure injuries in adult ICU patients. Methods: International 1-day point-prevalence study; follow-up for outcome assessment until hospital discharge (maximum 12 weeks). Factors associated with ICU-acquired pressure injury and hospital mortality were assessed by generalised linear mixed-effects regression analysis. Results: Data from 13,254 patients in 1117 ICUs (90 countries) revealed 6747 pressure injuries; 3997 (59.2%) were ICU-acquired. Overall prevalence was 26.6% (95% confidence interval [CI] 25.9–27.3). ICU-acquired prevalence was 16.2% (95% CI 15.6–16.8). Sacrum (37%) and heels (19.5%) were most affected. Factors independently associated with ICU-acquired pressure injuries were older age, male sex, being underweight, emergency surgery, higher Simplified Acute Physiology Score II, Braden score 3 days, comorbidities (chronic obstructive pulmonary disease, immunodeficiency), organ support (renal replacement, mechanical ventilation on ICU admission), and being in a low or lower-middle income-economy. Gradually increasing associations with mortality were identified for increasing severity of pressure injury: stage I (odds ratio [OR] 1.5; 95% CI 1.2–1.8), stage II (OR 1.6; 95% CI 1.4–1.9), and stage III or worse (OR 2.8; 95% CI 2.3–3.3). Conclusion: Pressure injuries are common in adult ICU patients. ICU-acquired pressure injuries are associated with mainly intrinsic factors and mortality. Optimal care standards, increased awareness, appropriate resource allocation, and further research into optimal prevention are pivotal to tackle this important patient safety threat

Data from: The importance of phytoplankton biomolecule availability for secondary production

The growth and reproduction of animals is affected by their access to resources. In aquatic ecosystems, the availability of essential biomolecules for filter-feeding zooplankton depends greatly on phytoplankton. Here, we analyzed the biochemical composition, i.e., the fatty acid, sterol and amino acid profiles and concentrations as well as protein, carbon, nitrogen, and phosphorus content of 17 phytoplankton monocultures representing the seven most abundant phytoplankton classes in boreal and sub-arctic lakes. To examine how the differences in the biochemical composition between phytoplankton classes affect their nutritional quality for consumers, we assessed the performance of Daphnia, on these diets. Furthermore, we defined the most important biomolecules regulating the somatic growth and reproduction of Daphnia, expecting that higher concentrations of certain biomolecules are needed for reproduction than for growth. Finally, we combined these results with phytoplankton field data from over 900 boreal and sub-arctic lakes in order to estimate whether the somatic growth of Daphnia is sterol-limited when the natural phytoplankton communities are cyanobacteria-dominated. Our analysis shows that Daphnia grows best with phytoplankton rich in sterols, ω-3 fatty acids, protein, and amino acids. Their reproduction follows food sterol and ω-3 concentration as well as C:P-ratio being two times higher in Daphnia feeding on cryptophytes than any other diet. Interestingly, we found that a high dietary ω-6 fatty acid concentration decreases both somatic growth and reproduction of Daphnia. When combined with phytoplankton community composition field data, our results indicate that zooplankton is constantly limited by sterols in lakes dominated by cyanobacteria (≥40% of total phytoplankton biomass), and that the absence of cryptophytes can severely hinder zooplankton production in nature

Data from: The importance of phytoplankton biomolecule availability for secondary production

The growth and reproduction of animals is affected by their access to resources. In aquatic ecosystems, the availability of essential biomolecules for filter-feeding zooplankton depends greatly on phytoplankton. Here, we analyzed the biochemical composition, i.e., the fatty acid, sterol and amino acid profiles and concentrations as well as protein, carbon, nitrogen, and phosphorus content of 17 phytoplankton monocultures representing the seven most abundant phytoplankton classes in boreal and sub-arctic lakes. To examine how the differences in the biochemical composition between phytoplankton classes affect their nutritional quality for consumers, we assessed the performance of Daphnia, on these diets. Furthermore, we defined the most important biomolecules regulating the somatic growth and reproduction of Daphnia, expecting that higher concentrations of certain biomolecules are needed for reproduction than for growth. Finally, we combined these results with phytoplankton field data from over 900 boreal and sub-arctic lakes in order to estimate whether the somatic growth of Daphnia is sterol-limited when the natural phytoplankton communities are cyanobacteria-dominated. Our analysis shows that Daphnia grows best with phytoplankton rich in sterols, ω-3 fatty acids, protein, and amino acids. Their reproduction follows food sterol and ω-3 concentration as well as C:P-ratio being two times higher in Daphnia feeding on cryptophytes than any other diet. Interestingly, we found that a high dietary ω-6 fatty acid concentration decreases both somatic growth and reproduction of Daphnia. When combined with phytoplankton community composition field data, our results indicate that zooplankton is constantly limited by sterols in lakes dominated by cyanobacteria (≥40% of total phytoplankton biomass), and that the absence of cryptophytes can severely hinder zooplankton production in nature

Fatty acid composition as biomarkers of freshwater microalgae: analysis of 37 strains of microalgae in 22 genera and in seven classes

The fatty acid (FA) composition of algae is an important determinant of their food quality for consumers, and FAs can also be used as biomarkers for biochemical and energetic pathways in food webs. FA analyses of 7 freshwater algal classes and 37 strains showed clear similarity within classes and strong differences amongst classes. Class was a dominant factor (66.4%) explaining variation in FA signatures of microalgae. The 7 algal classes comprised 4 separate groups according to their FA profiles: (1) Chlorophyceae and Trebouxiophyceae, (2) Bacillariophyceae, (3) Cryptophyceae, Chrysophyceae, and Raphidophyceae, and (4) Euglenophyceae. Each group had a characteristic FA composition, although the proportional abundance of individual FAs also differed between species and with environmental conditions. FAs found to be particularly representative for each group (i.e. diagnostic biomarkers) were as follows: 16:4ω3 and 16:3ω3 for Chlorophyceae and Trebouxiophyceae; 16:2ω7, 16:2ω4, 16:3ω4, 16:4ω1, and 18:4ω4 for Bacillariophyceae; 22:5ω6 and 18:4ω3 for Cryptophyceae and Chrysophyceae (Synurales), 16:3ω1 for Chrysophyceae (Ochromonadales), 16:2ω4, 16:3ω4, 16:3ω1, and 20:3ω3 for Raphidophyceae; and 15:4ω2, 20:4ω3, 20:2ω6, 20:3ω6, and 22:4ω6 for Euglenophyceae. FAs thus offer a powerful tool to track different consumer diets in a lacustrine food web. Based on the 20:5ω3 (eicosapentaenoic acid) and 22:6ω3 (docosahexaenoic acid) content among the investigated freshwater algal classes, Chlorophyceae, Trebouxiophyceae, and Chrysophyceae are of intermediate food quality for zooplankton, and Cryptophyceae, Bacillariophyceae, Euglenophyceae, and Raphidophyceae should be excellent resources for zooplankton.peerReviewe

Isotopic difference between fatty acid and bulk biomass of freshwater phytoplankton.

<p>The carbon isotopic difference (Δ δ¹³C, mean ± SD) between fatty acid groups and bulk biomass varied amongst the phytoplankton classes.</p