Competition drives clumpy species coexistence in estuarine phytoplankton

Understanding the mechanisms that maintain biodiversity is a fundamental problem in ecology. Competition is thought to reduce diversity, but hundreds of microbial aquatic primary producers species coexist and compete for a few essential resources (e.g., nutrients and light). Here, we show that resource competition is a plausible mechanism for explaining clumpy distribution on individual species volume (a proxy for the niche) of estuarine phytoplankton communities ranging from North America to South America and Europe, supporting the Emergent Neutrality hypothesis. Furthermore, such a clumpy distribution was also observed throughout the Holocene in diatoms from a sediment core. A Lotka-Volterra competition model predicted position in the niche axis and functional affiliation of dominant species within and among clumps. Results support the coexistence of functionally equivalent species in ecosystems and indicate that resource competition may be a key process to shape the size structure of estuarine phytoplankton, which in turn drives ecosystem functioning.

Synthesis and biological properties of side-chain-modified bleomycins

New side-chain-modified bleomycins (BLMs) 3a-k have been synthesized by the reaction of demethyl BLM A2 with alpha-bromoacetamides (2a-k). The structures of these BLM analogues have been established by comparison of their NMR spectra with the corresponding spectra of model thiazole derivatives. Mass spectra (FAB) of the modified BLMs are not informative, since the fragmentation patterns exhibit a loss of the modified chain moiety, presumably in the matrix. The purity of the compounds is attested by TLC and HPLC analyses. Biological evaluation of 3a-k in in vitro (survival of B16 melanoma cells) shows that the compounds are almost as effective as bleomycin. Examination of the effects of 3c, 3e, and 3f on lungs of male mice indicates that the analogues do not exhibit lower pulmonary toxicity than bleomycin.

Complete assignment of the 500 MHz 1H-NMR spectra of bleomycin A2 in H2O and D2O solution by means of two-dimensional NMR spectroscopy

1H-NMR spectra of bleomycin A2 recorded at 500 MHz in D2O and H2O at 24 degrees C and 3 degrees C were investigated. Resonances of the individual spin systems were identified by using two-dimensional correlation spectroscopy (COSY), two-dimensional spin echo correlated spectroscopy (SECSY) and by the application of two-dimensional Nuclear Overhauser Effect spectroscopy (NOESY). Employment of these techniques allowed the assignment of 113 exchangeable and 59 non-exchangeable protons in the 1H NMR spectrum of bleomycin A2. By means of 2D NOE spectroscopy also interresidual connectivities could be observed. Comparison of the NOESY spectra at 3 degrees C and 24 degrees C suggest that at low temperatures the central party of the bleomycin A2 molecule tends to adopt an extended conformation.

Implementation and evaluation of an undergraduate emergency medicine curriculum

OBJECTIVE

To describe the implementation and evaluation of an undergraduate course in the first Australian academic emergency medicine unit.

METHODS

A descriptive study of a course involving fifth year medical students at the University of Western Australia was undertaken. Teaching included self-directed case problem solving, small group tutorials, practical-skills teaching, clinical attachments and information handouts. Evaluation involved questionnaire scores and written feedback regarding life-support skills, tutorial teaching, course materials, clinical attachments and the course in general. Some groups of students underwent pre-course and post-course examinations.

RESULTS

Subjective and objective testing showed that student knowledge significantly improved. Feedback was especially positive toward clinical attachments in emergency departments, practical skills tutorials and the case-based learning method. Students requested longer attachments to emergency departments, and more practical, case-based, interactive and bedside teaching. Problems encountered included inadequate time for teaching, vagueness about student roles and objectives, and dealing with death for the first time without adequate preparation.

CONCLUSION

Undergraduate emergency medicine education should become an essential part of Australian and international undergraduate medical education. Emergency medicine is enjoyable and eminently suitable for problem-based, interactive and integrated teaching and improves confidence, clinical experience in emergencies, practical skills and teamwork. Improvements include more problem-based teaching, more practical skills sessions and better definition of student roles. These are general principles that can be applied to other undergraduate courses and to designers of other emergency medicine courses, both undergraduate and postgraduate.

Derivatives of eis-NPCl2(NSOCl)2 and (NPCl2)2NSOCl, Part IX [1] Substitution Reactions of cis-NPCl2(NSOCl)2 with Piperidine

Aminolysis of cis-NPCl2(NSOCl)2 by piperidine in acetonitrile at room temperature proceeds via a non-geminal substitution pattern. During the first substitution step the reactivity of a SOCl-centre appears to be greater than that of a PCl2-centre. The second and third substitution step successively take place at the PCl2- and remaining SOCl-centre. The different isomeric forms of the mono-, bis-, tris-, and tetrakis(piperidino) derivatives are characterized by means of 31P NMR data. Application of 13C NMR leads in two cases to a structure assignment.

Derivatives of cis-NPCl2(NSOCl)2 and (NPCl2)2NSOCl, Part XV [1]. Methyl-and Ethylamino Derivatives of (NPCl2)2NSOPh

The aminolysis of (NPCl2)2NSOPh by methyl-and ethylamine in diethylether proceeds mainly via a non-geminal substitution pattern. In acetonitrile both geminal and non-geminal substitution is observed. The preparation of the derivatives is described and the 1H and 31P NMR data are discussed. The interpretation of the NMR spectra is supported by the simulation of the spectra of NPClNHMeNPCl2NSOPh.

Using trait-based approaches to study phytoplankton seasonal succession in a subtropical reservoir in arid central western Argentina

The application of trait-based approaches has become a widely applied tool to analyse community assembly processes and dynamics in phytoplankton communities. Its advantages include summarizing information of many species without losing essentials of the main driving processes. Here, we used trait-based approaches to study phytoplankton temporal succession in a subtropical reservoir. We applied a combined approach including morphological traits (i.e. volume, surface) and functional clustering of species (morphology-based functional groups (MBFG) and Reynolds' groups) and related the clustering of species with the environment. We found that this reservoir is characterized by a low richness and a bimodal distribution of phytoplankton biomass. Taxonomic and functional classifications were coincident, and the dominant species and groups biomasses were explained by the same group of variables. For instance, group X₂, MBFG V and Carteria sp. biomasses were explained by: pH, Secchi disk depth, N-NH₄; while group B, MBFG VI and Cyclotella ocellata biomasses were explained by stability of the water column, incident solar radiation, Secchi disk depth and N-NH4. From our results, we state that functional and taxonomic classifications are complementary rather than opposed approaches, and their specific uses depend exclusively on the aim of the study and the characteristics of the environment under evaluation. Our work is the first description of phytoplankton dynamics in a reservoir in the arid central western Argentina (Cuyo region).

A reply to "Relevant factors in the eutrophication of the Uruguay River and the Río Negro"

A recent paper by Beretta-Blanco and Carrasco-Letelier (2021) claims that agricultural eutrophication is not one of the main causes for cyanobacterial blooms in rivers and artificial reservoirs. By combining rivers of markedly different hydrological characteristics e.g., presence/absence and number of dams, river discharge and geological setting, the study speculates about the role of nutrients for modulating phytoplankton chlorophyll-a. Here, we identified serious flaws, from erratic and inaccurate data manipulation. The study did not define how erroneous original dataset values were treated, how the variables below the detection/quantification limit were numerically introduced, lack of mandatory variables for river studies such as flow and rainfall, arbitrary removal of pH > 7.5 values (which were not outliers), and finally how extreme values of other environmental variables were included. In addition, we identified conceptual and procedural mistakes such as biased construction/evaluation of model prediction capability. The study trained the model using pooled data from a short restricted lotic section of the (large) Uruguay River and from both lotic and reservoir domains of the Negro River, but then tested predictability within the (small) Cuareim River. Besides these methodological considerations, the article shows misinterpretations of the statistical correlation of cause and effect neglecting basic limnological knowledge of the ecology of harmful algal blooms (HABs) and international research on land use effects on freshwater quality. The argument that pH is a predictor variable for HABs neglects overwhelming basic paradigms of carbon fluxes and change in pH because of primary productivity. As a result, the article introduces the notion that HABs formation are not related to agricultural land use and water residence time and generate a great risk for the management of surface waterbodies. This reply also emphasizes the need for good practices of open data management, especially for public databases in view of external reproducibility.