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.

[Postraumatic epidural arachnoid spinal cyst: case report]. / Quiste aracnoideo espinal epidural postraumático: presentación de un caso.

INTRODUCTION: Extradural arachnoid spinal cysts are unfrequent lesions that are associated with spinal trauma, surgery and less frequently with congenital anomalies. The clinical manifestations are similar to those seen with other compressive spinal cord lesions. Magnetic resonance techniques allow to diagnose correctly this pathology and to define its thopographic situation. The pathologic history of the patient is essencial to establish the ethiology. Surgery is the elective treatment in most cases. CLINICAL CASE: The patient is a 35 years old man who has a medical history of penetrating spinal trauma two years ago. In that instance he suffered an unilateral spinal cord section at D2-D3 level with the corresponding Brown Sequard syndrome. A small wound was detected at the skin dorsal level and it was closed without difficulties. At the beginning, he improved his motor right leg function with rehabilitation and vitamins. After two years of good recovery he came to our hospital suffering a neurological deterioration of six months of evolution. The physical examination revealed an spastic paraparesis. Magnetic resonance was performed demonstrating a cystic extradural collection compressing the spinal cord at D3-D4 level. Surgical decompressive treatment allowed to excise the cyst and it was possible to define a dural tear that was closed successfully. The outcome was good with restoration of the initial motor function that he had after the spinal trauma. CONCLUSIONS: Surgical management of postraumatic epidural arachnoid spinal cyst allows to detect the meningeal tear and to close it, which is highly effective on these kinds of lesions.