Community fluctuations and local extinction in a planktonic food web.

Determining statistical patterns irrespective of interacting agents (i.e. macroecology) is useful to explore the mechanisms driving population fluctuations and extinctions in natural food webs. Here, we tested four predictions of a neutral model on the distribution of community fluctuations (CF) and the distributions of persistence times (APT). Novel predictions for the food web were generated by combining (1) body size-density scaling, (2) Taylor's law and (3) low efficiency of trophic transference. Predictions were evaluated on an exceptional data set of plankton with 15 years of weekly samples encompassing c. 250 planktonic species from three trophic levels, sampled in the western English Channel. Highly symmetric non-Gaussian distributions of CF support zero-sum dynamics. Variability in CF decreased while a change from an exponential to a power law distribution of APT from basal to upper trophic positions was detected. Results suggest a predictable but profound effect of trophic position on fluctuations and extinction in natural communities.

Interannual changes in winter-spring zooplankton estuarine community forced by hydroclimatic variability - With special reference to bioindicator species Eurytemora americana.

Climatic variability and anthropogenic pressures impact the structure and dynamics of pelagic ecosystems and copepods are good indicators of such changes. This investigation aims to explore the interannual pattern of the mesozooplankton community, in relation to environmental variables in the Bahía Blanca Estuary during winter-spring from last two decades focusing on the dominant species Eurytemora americana. Main changes recorded include increased temperature, alteration of the nutrient balance, a decrease in chlorophyll-a, modifications in the abundance-structure of the phytoplankton assemblages, and changes in the abundance-structure of the mesozooplankton community. A significant decrease was observed in species richness of the mesozooplankton over time. Alterations in abundance and reproductive traits of E. americana, were also found. The population of E. americana dropped from mean relative abundance of 47% in first years to 20-12% in lasts one, accompanied with an increase of copepod species characterized by higher trophic plasticity in eutrophic conditions, like Acartia tonsa and Euterpina acutifrons.

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.

The relationship between a calculation test given in nursing orientation and medication errors.

This article presents a descriptive study that investigates the relationship between pass/fail scores on a medication test given to registered nurses in orientation and medication errors made on nursing units. Medication errors made during a 3-year period of time were reviewed to determine number of errors made and the nurses who made the errors. Pass/fail scores from the medication test given in orientation were checked to see whether the nurses who made the errors had passed or failed the test. Chi square, t test, and multiple regression analysis were used to evaluate the data. Results showed that nurses who failed the medication test were more likely to make medication errors than nurses who had passed the medication test.

Management of cardiopulmonary arrest in the rehabilitation setting.

Life-threatening cardiac and respiratory arrests are stressful emergency situations. Nurses may be anxious and unsure of what needs to be done if their roles are not clearly defined. This article describes a system one rehabilitation hospital uses when responding to arrests, reviews the steps in basic cardiopulmonary resuscitation, and presents an algorithm of a cardiopulmonary arrest.

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.

Comparison of the predation rate of freshwater cyclopoid copepod species on larvae of the mosquito Culex pipiens.

The predation rates of six copepod species: Acanthocyclops robustus G.O. Sars, Eucyclops neumani Pesta, Macrocyclops albidus Jurine, Mesocyclops longisetus Thibaud, Metacyclops grandis Kiefer and Metacyclops mendocinus Wierzejski (Copepoda: Cyclopidae) on mosquito larvae, Culex pipiens Linnaeus (Diptera: Culicidae) were assessed. Experiments consisted of 24-h incubations of one copepod and 10 larvae without extra food at 16 degrees C and 26 degrees C. Nine replicates were considered for each species and temperature. Predation rates (larvae per copepod per day) were: M. mendocinus (1.8), M. grandis (3.1), E. neumani (3.8), A. robustus (3.8), Ma. albidus (6.1) and Me. longisetus (7.0). There was a significant effect of both species and temperature on predation: all species experienced higher predation at 26 degrees C than at 16 degrees C, except for A. robustus whose predation rate was similar at both temperatures. These observations are consistent with previous results that point to Macrocyclops and Mesocyclops genera as important larval predators and suggest the need for field trials to evaluate the response of Ma. albidus and Me. longisetus under natural conditions in Uruguay.