New explorations in the desert of northeastern Zacatecas, in central-northern Mexico, revealed dozens of archaeological and geoarchaeological sites. One of them, Ojo de Agua, contains the remains of a Pleistocene spring-fed hydrographic system located at the southeastern end of a large elongated endorheic basin. The locality yielded a particularly dark, highly organic stratigraphic layer commonly known in the Americas as Black Mat (BM), exposed on the natural profiles of a creek, but not associated with cultural materials. Several radiocarbon assessments confirmed the formation of the Ojo de Agua Black Mat during the Younger Dryas chronozone, with ten calibrated results clustering between 12,700–12,100 cal BP. This multi-proxy study confirmed the peculiarity of the deposit and found similarities and differences with other contexts of Younger Dryas age. The Ojo de Agua Black Mat (stratum C2) is far richer in charcoal specks than the related strata, but lacks phytoliths, diatoms or ostracods. No further biological remains were found in it, except for intrusive capillary roots. Clearly water-lain in a shallow pond, the stratum qualifies as a clayey silt with an acidic-to-neutral pH. Rich in heavy metals and with high contents of titanium, the Ojo de Agua Black Mat yielded significant indicators of intense wildfires during the Younger Dryas, but produced no carbon spherules or nanodiamonds supposedly linked to the impact theory.

Se ofrece una sinopsis de las especies del género Navicula sensu lato identificadas en acuatorios dulciacuícolas de Cuba. En 79 localidades se determinaron 43 taxones, de los cuales 25 se registran en un área mas amplia que la anterior y siete son nuevos registros para el país: N. bicephala, N. concentrica, N. goeppertiana var. dapalis, N. lateropunctata, N. pseudoanglica, N. schadei y N. stroemii. El trabajo incluye además las dimensiones celulares, comentarios taxonómicos, la distribución por localidades e ilustraciones originales de cada taxón. Citación: Toledo, L. & Comas,A. 2008. Especies de agua dulce de Navicula (Bacillariophyceae) de Cuba. Revista Jard. Bot. Nac. Univ. Habana 29: 171-184. Publicado: 3 de marzo de 2010. | In the present paper a sinopsis of the genus Navicula sensu lato inhabiting the Cuban freshwaters is offered. Based on samples collected from 79 localities, 43 taxa are identified, from which: N. bicephala, N. concentrica, N. goeppertiana var. dapalis, N. lateropunctata, N. pseudoanglica, N. schadei y N. stroemii are new reports. In the paper are also included cell dimensions, characteristics of Cuban populations and original drawings for each taxon involved. Citation: Toledo, L. & Comas,A. 2008. Especies de agua dulce de Navicula (Bacillariophyceae) de Cuba. Revista Jard. Bot. Nac. Univ. Habana 29: 171-184. Published: 3 March 2010.

A catalog of Bacillariophyceae for the rivers of NW of Spain is made for the first time. It includes a re-examination of the taxa reported in previous publications, taxa cited during the last years of the rivers of the Galicia-Costa Hydrographic Demarcation, and a revision of the taxonomy, in line with the systematic and nomenclature changes, which have occurred mainly in recent years. The epilethic diatoms of the river basins of Galicia-Costa were sampled during the years 2005, 2006, and 2007, in May-June and September. The study was carried out in 41 localities distributed along 31 rivers, samples were taken in upstream and downstream sections. Diatom communities were compared in all upstream sections of these rivers draining from siliceous substrates. We identified 141 taxa of diatoms from the coast of Galicia. In this paper we present 15 new citations for Galicia, two for Spain and three for the Iberian Peninsula, in addition to a new species recently described. The dominant taxa are: Achnanthidium minutissimum, Achnanthes subhudsonis, Karayevia oblongella, Cocconeis placentula var. euglypta, Gomphonema rhombicum, and Navicula minima. Achnanthes subhudsonis was the most abundant species during the spring and summer months. The remaining species showed no relevant changes regardless of the time of year. The results indicate that the river diatoms of Galicia are an important component of the diversity of the ecosystem. | Se realiza por primera vez un catálogo de Bacillariophyceae para los ríos del NW de España. Se incluyen un nuevo examen de los táxones recogidos en publicaciones anteriores, datos de táxones citados durante los últimos años de los ríos de la demarcación hidrográfica de Galicia-Costa y una revisión de la taxonomía, en consonancia con los cambios sistemáticos y nomenclaturales, que se han producido sobre todo durante los últimos años. Se estudiaron las diatomeas epilíticas de las cuencas de los ríos de Galicia-Costa entre los años 2005, 2006 y 2007, durante dos temporadas diferentes: mayo-junio y septiembre. El estudio se llevó a cabo en 41 localidades distribuidas a lo largo de 31 ríos, donde se tomaron muestras en tramos aguas arriba y aguas abajo. Las comunidades de diatomeas de estos ríos que drenan de sustratos silíceos fueron comparadas en todos los tramos de aguas arriba. Se identificaron 141 táxones de diatomeas de la costa de Galicia. En este trabajo presentamos 15 nuevas citas para Galicia, dos para España y tres para la Península Ibérica, además de una nueva especie recientemente descrita. Los táxones dominantes son: Achnanthidium minutissimum, Achnanthes subhudsonis, Karayevia oblongella, Cocconeis placentula var. euglypta, Gomphonema rhombicum, y Navicula minima. Achnanthes subhudsonis fue la especie más abundante durante los meses de primavera y verano. Las especies restantes no mostraron cambios pertinentes independientemente de la época del año. Los resultados indican que las diatomeas de los ríos de Galicia son un componente importante de la diversidad del ecosistema.