Abstract: Background and Aims: The reefs of the Parque Nacional Arrecifes de Cozumel constitute one of the main reef formations in Mexico. However, up to date phycofloristic studies that allow detecting changes in the phycofloristic composition or its affinity for some substrates are practically non-existent. Our aim was to determine the taxonomic composition of marine macroalgae present in the Parque Nacional Arrecifes de Cozumel, as well as realize their morphological descriptions and an analysis of their affinity with the substrate they colonize. Methods: The sampling was carried out in October and November 2018 by autonomous diving in 14 reefs of the Parque Nacional Arrecifes de Cozumel. Morphological observations were made using optical and stereoscopic microscopes. The taxonomic determination was made using specialized literature. Key results: Fourty-two taxa were determined: five Ochrophyta, 12 Rhodophyta and 25 Chlorophyta. The best-represented family for Ochrophyta was Dictyotaceae; for Rhodophyta, Ceramiaceae and Rhodomelaceae; and for Chlorophyta, Halimedaceae. New records for the Parque Nacional Arrecifes de Cozumel are described, including Lobophora guadeloupensis as a new record for Mexico. Additionally, four different substrates for the algae were identified: psammophytic (33%), epilithic (32%), epizoic (19%) and epiphytic (16%). The most diverse reefs were La Francesa (LF) and Santa Rosa (SR), whereas the least diverse were Chankanaab (CK) and Tormentos (TM). Conclusions: Although many of the previous records in the area were confirmed in the present study, the presence of 18 new records revealed, on the one hand, the lack of constant monitoring of the algal richness of the region, and on the other hand, the need for morphological descriptions or photographic references that allow contrasting the previous records with the current ones. Given the importance of the Parque Nacional Arrecifes de Cozumel, our results, in addition to offering updated information, represent a starting point for studies in conservation biology.

Resumen: Antecedentes y Objetivos: Los arrecifes del Parque Nacional Arrecifes de Cozumel constituyen una de las principales formaciones arrecifales de México. Sin embargo, actualmente, son prácticamente inexistentes los estudios ficoflorísticos que permiten detectar cambios en la composición ficoflorística o su afinidad por algún sustrato. Por lo tanto, nuestro objetivo fue determinar la composición taxonómica de macroalgas marinas presentes en el Parque Nacional Arrecifes de Cozumel, así como realizar sus descripciones morfológicas y análisis de afinidad con el sustrato que colonizan. Métodos: Los muestreos se realizaron en octubre y noviembre de 2018 en 14 arrecifes del Parque Nacional Arrecifes de Cozumel, mediante buceo autónomo. Se realizaron observaciones morfo-anatómicas utilizando tanto microscopios ópticos como estereoscópicos. La determinación taxonómica se realizó a partir de literatura especializada. Resultados clave: Se determinaron 42 taxa: cinco Ochrophyta, 12 Rhodophyta y 25 Chlorophyta. La familia mejor representada para Ochrophyta fue Dictyotaceae; para Rhodophyta, Ceramiaceae y Rhodomelaceae; y para Chlorophyta, Halimedaceae. Se describen nuevos registros para el Parque Nacional Arrecifes de Cozumel incluyendo a Lobophora guadeloupensis como nuevo registro para México. Adicionalmente, se identificaron cuatro diferentes sustratos para las algas: psamofítico (33%), epilítico (32%), epizoico (19%) y epífito (16%). Los arrecifes más diversos fueron La Francesa (LF) y Santa Rosa (SR), y los menos diversos fueron Chankanaab (CK) y Tormentos (TM). Conclusiones: Aunque muchos de los registros previos en el área fueron confirmados en el presente estudio, la presencia de 18 nuevos registros reveló, por un lado, la falta de monitoreos constantes de la riqueza algal de la región, y, por otro lado, la necesidad de contar con descripciones morfológicas o referencias fotográficas que permitan contrastar los registros previos con los actuales. Dada la importancia del Parque Nacional Arrecifes de Cozumel, nuestros resultados, además de ofrecer información actualizada, representan un punto de partida para estudios en biología de la conservación.

Resumo En regiones tropicales hay una gran cantidad de especies de diatomeas que todavía no han sido identificadas. Esta investigación tuvo como objetivo estudiar la composición de la flora de diatomeas epilíticas encontradas en muestras recolectadas en el río Dagua, una cuenca hidrográfica andina tropical, ubicada suroeste de Colombia. Los muestreos se realizaron en tres estaciones con sus respectivas tres réplicas entre enero y abril de 2018 para recolectar muestras para la identificación de diatomeas (Clase Bacillariophyceae). Estas muestras se analizaron con microscopía óptica y microscopía de contraste interferencial. Los resultados indicaron la presencia de 18 taxa distribuidos en 9 familias y 11 géneros. Dos de estas, son nuevos registros para Colombia: Navicula incarum y Fragilaria aff. socia. El género con mayor riqueza específica fue Navicula. Una comparación con la flora de diatomeas de la región muestra que se registraron nueve especies en común con el Río Cali.

Abstract In tropical regions there are a large number of species of diatoms that have not been identified yet. This research aimed to study the composition of epilithic diatom flora found in samples collected in Dagua River a tropical Andean hydrographical basin located to the southwest of Colombia. Samplings were performed in three stations with their respective three replicas between January and April 2018 to collect samples for identification of diatom (Class Bacillariophyceae). These samples were analyzed with light microscopy and interferential contrast microscopy. The results indicated the occurrence of 18 taxa distributed in 9 families and 11 genera. Two of these are new records for Colombia: Navicula incarum and Fragilaria aff. socia. The most species-rich genera was Navicula. A comparison with the diatom flora of the region shows that 9 species were recorded in common with the Cali River.

ABSTRACT Background: The Angulo River has been subject to environmental deterioration as a result of agriculture practices and industrial discharges to its tributary. Goal: Determine the species of diatoms that indicate contamination and their distribution in the Angulo river, a tributary of the Lerma river. Method: Twelve sites including 2 springs were selected during the low-water and post-rain periods of 2005. The samples were obtained by scraping the rocks to separate the attached diatoms. These were cleaned by oxidizing the sample with hydrochloric acid and hydrogen peroxide; permanent preparations were made with Naphrax® resin, for review with light microscopy. Results: 50 taxa belonging to 20 genera were identified, of which 5 species belong to central forms and 45 to pennate species. The taxa present in both periods were Achnanthidium minutissimum, Amphora pediculus, Luticola geoppertiana, Nitzschia amphibia, Nitzschia dissipata var. dissipata, Pleurosira laevis, Staurosira pinnata and Ulnaria ulna. The temperature, pH, dissolved oxygen and total dissolved solids in the Angulo river presented spatial variations and with it the species records. Conclusions: Representative taxa of eutrophic and non-eutrophic environments were found throughout the tributary, such as Nitzschia palea and Amphora pediculus, respectively. This study has provided relevant information regarding the presence and distribution of diatom species that can be used as bioindicators of environmental conditions. specific.

RESUMEN Antecedentes: El río Ángulo ha estado expuesto a un deterioro ambiental como consecuencia de las descargas industriales a su afluente. Objetivo: Determinar las especies de diatomeas indicadoras de contaminación y su distribución en el río Angulo afluente del río Lerma. Métodos: Se seleccionaron 12 sitios incluyendo 2 manantiales durante los periodos de estiaje y post lluvias del año 2005. Las muestras se obtuvieron raspando las rocas para separar las diatomeas adheridas. Estas se limpiaron oxidando la muestra con ácido clorhídrico y peróxido de hidrógeno; se elaboraron preparaciones permanentes con la resina Naphrax®, para su revisión con microscopia óptica. Resultados: Se identificaron 50 taxones pertenecientes a 20 géneros de los cuales 5 especies pertenecen a formas centrales y 45 a las pennadas. Los taxones espresentes en ambos periodos fueron Achnanthidium minutissimum, Amphora pediculus, Luticola geoppertiana, Nitzschia amphibia, Nitzschia dissipata var. dissipata, Pleurosira laevis, Staurosira pinnata y Ulnaria ulna. La temperatura, pH, oxígeno disuelto y sólidos disueltos totales en el río Angulo presentaron variaciones espaciales y con ello los registros de las especies. Conclusiones: A lo largo del afluente, se encontraron taxones representativos de ambientes eutrofizados y no eutrofizados como Nitzschia palea y Amphora pediculus. Este estudio aporta información relevante en cuanto a la presencia y distribución de especies de diatomeas que pueden ser utilizadas como bioindicadores de condiciones ambientes específicos.

Climate change-induced temperature increase may influence the ecotoxicity of agricultural herbicides such as atrazine and consequently negatively impact aquatic biota. The objective of this study was to assess the effects of increased temperature on the ecotoxicity of atrazine to diatom community structure and stream periphyton load using laboratory microcosm experiments. A natural periphyton community from the Mukwadzi River, Zimbabwe, was inoculated into nine experimental systems containing clean glass substrates for periphyton colonisation. Communities were exposed to 0 µg∙L-1 (control), 15 µg∙L-1 and 200 µg∙L-1 atrazine concentrations at 3 temperature levels of 26°C, 28°C and 30°C. Periphyton dry weight and community taxonomic composition were analysed on samples collected after 1, 2 and 3 weeks of colonisation. A linear mixed-effects model was used to analyse the main and interactive effects of atrazine and temperature on dry mass, species diversity, evenness and richness. Temperature and atrazine had significant additive effects on species diversity, richness and dry mass. As temperature increased, diatom species composition shifted from heat-sensitive species such as Achnanthidium affine to heat-tolerant species such as Achnanthidium exiguum and Epithemia adnata. Increasing temperature in aquatic environments contaminated with atrazine results in sensitive and temperature-intolerant diatoms being eliminated from periphyton communities. Climate change will exacerbate effects of atrazine on periphyton dry mass and diatom community structure.

Background and Aims: The diatom Craticula gadorensis sp. nov. is described from samples of epilithic algae collected in a shallow pond from the Gador mountains, in the province of Almería (Spain). M: Samples were taken and processed following the usual protocols for diatoms. Morphological and ultrastructural characteristics of this new taxon are described and illustrated using light and scanning electron microscopy. Results: The new species is characterised by having elliptic-lanceolate to rhombic-lanceolate valves, with slightly protracted, subrostrate apices, a linear, narrow axial area and a slightly dilated, linear-lanceolate central area. Conclusions: A morphological comparison with related species shows that the combination of features in Craticula gadorensis is unique (mainly the dimensions, areola density and the shape of the central area).

Introducción y objetivos: Se describe la diatomea Craticula gadorensis sp. nov. a partir de muestras de algas epilíticas recogidas en una balsa ganadera de la Sierra de Gádor, en la provincia de Almería. M: Las muestras se tomaron y procesaron siguiendo los protocolos metodológicos para diatomeas. Los caracteres morfológicos y ultraestructurales de este nuevo taxón se describen e ilustran mediante imágenes de microscopía óptica y electrónica. resultados: La nueva especie se caracteriza por presentar valvas elíptico-lanceoladas a rómbico-lanceoladas, con ápices ligeramente prolongados, subrostrados, con un área axial lineal, estrecha y un área central un poco dilatada, lineal-lanceolada. conclusiones: La comparación morfológica con otras especies del género muestra que la combinación de caracteres de Craticula gadorensis (principalmente las dimensiones, la densidad de areolas y la forma del área central) es única.

In shallow estuaries, artificial substrates provide a means of assessing the response of the diatom community to water chemistry. The shallow St Lucia Estuary was historically connected to the Mfolozi River at the mouth. This connection was severed during the early 1950s due to sediment input from the agriculturally impacted Mfolozi River. A connection has recently been re-established and the potential impact of dissolved inorganic nutrients from the Mfolozi River needs to be determined, as it may alter the ecological integrity of the St Lucia Estuary which forms part of a UNESCO World Heritage Site. This study found that the epilithic algal biomass and diatom species composition grown on glass slides were good indicators of nutrient enrichment in the estuary. Over a 28-day study period an above-average rainfall event resulted in an increase of nutrient-enriched freshwater flow into the estuary. No significant biomass differences were recorded in either the natural phytoplankton or microphytobenthos communities because of high variability. By contrast, the epilithic algal biomass accumulation on the glass slides was highest following the freshwater input. Statistical analyses indicated that the accumulation of the epilithic community on the glass slides was mostly affected by DIN and salinity. Diversity index scores for both the natural phytoplankton and microphytobenthos were variable, while the epilithic diatom index scores consistently declined from Day 7 (H' = 1.2) to Day 28 (H' = 0.7). These data indicate that epilithic algae grown on glass slides can be used as an effective monitoring tool to detect nutrient-induced changes as a supplementary method in this highly variable estuary.

Abstract: Diatom growth strategies, which are used as a proxy to analyze disturbances and environmental impacts, can also provide reliable information about environmental gradients. In this study, we used diatom communities and biological traits to assess the structure of epilithic diatoms after an oil spill in a large tributary of the Iguaçu River (Paraná, Brazil). Epilithon and water samples were taken on July 12th, 2004, and after an unexpected oil spill, on the following days: 09/19, 10/03, and 10/13/2004. We observed that the spill caused a distinct shift in both diatom composition and guild group. Diversity decreased and pollution-tolerant diatoms of the motile group became dominant in response to the elevated nutrient levels and reduced light. Tube-forming diatoms, which are strong competitors for light, dominated the epilithon 24 days after the oil spill. Both diatom guilds and growth forms were successfully used to predict the environmental conditions. While diatom guilds responded to disturbances along a temporal gradient, changes inside the guilds were the main factor for understanding the environmental gradient.

Resumo A presente pesquisa objetivou o estudo da composição da flora de diatomáceas epilíticas encontradas em amostras coletadas na bacia hidrográfica do Rio Cali, Colômbia. Excursões trimestrais (março, junho, setembro e dezembro de 2012 e março de 2013) foram realizadas em seis sítios de amostragem para coletar amostras para a identificação dos organismos do grupo das diatomáceas (Classe Bacillariophyceae). Os resultados indicaram a ocorrência de 83 táxons, distribuídos em 26 famílias e 38 gêneros. 32 desses táxons são novas ocorrências na Colômbia. As famílias mais representativas foram Gomphonemataceae, Naviculaceae e Bacillariaceae. Os gêneros com maior riqueza de espécies foram Navicula, Gomphonema e Nitzschia. Oito espécies tiveram ocorrência em todos os sítios de amostragem: Achnanthidium minutissimum, Cocconeis lineata, Cymbella affinis, Gomphonema pumilum var. rigidum, Melosira varians, Navicula symmetrica, Reimeria sinuata e Rhoicosphenia abbreviata. Os resultados indicaram 13 espécies consideradas dominantes, e caracterizam a flora diatomológica da bacia hidrográfica do Rio Cali, Colômbia.

Abstract This research aimed to study the composition of epilithic diatom flora found in samples collected in Cali River hydrographical basin, Colombia. Quarterly excursions (March, June, September and December of 2012 and March of 2013) were performed in six sampling sites to collect samples for identification of diatom organisms (Class Bacillariophyceae). The results indicated the occurrence of 82 taxa distributed in 26 families and 38 genera. 32 of these are new occurrences in Colombia. The most representative families were Gomphonemataceae, Naviculaceae and Bacillariaceae. The genera richest in species were Navicula, Gomphonema and Nitzschia. Eight species occurred in all sampling sites: Achnanthidium minutissimum, Cocconeis lineata, Cymbella affinis, Gomphonema pumilum var. rigidum, Melosira varians, Navicula symmetrica, Reimeria sinuata and Rhoicosphenia abbreviata. The results indicated 13 species considered dominant and characterize the flora of epilithic diatoms in Cali River hydrographical basin, Colombia.

RESUMO Arnoldiella elbakyaniae sp. nov. é descrita com base em material epilítico coletado em uma cascata de um riacho no nordeste brasileiro, Estado do Piauí. O riacho pertence à bacia do rio Parnaíba que é uma das regiões mais pobremente amostradas no país. Apresentamos aqui também uma nova combinação de Basicladia emedii C.K. Peres & C.C.Z. Branco em Arnoldiella emedii comb. nov. seguindo o arranjo proposto para o grupo. Arnoldiella elbakyaniae pode ser reconhecida por um talo heterotríqueo com filamentos eretos pequenos, não ramificados ou esparsamente ramificados e célula basal do sistema ereto curta e larga. Difere de A. emedii pelas suas células basais mais curtas, pelas células do eixo mais estreitas e cilíndricas e pelos zoosporângios em cadeias terminais.

ABSTRACT Arnoldiella elbakyaniae sp. nov. is described based on epilithic material collected in a cascade of a stream in Northeastern Brazil, Piauí State. The stream belongs to the Parnaíba river basin, which encompasses one of the most poorly sampled regions in the country. We also propose here the combination of Basicladia emedii C.K. Peres & C.C.Z. Branco into Arnoldiella emedii comb. nov., following the new arrangement proposed for the group. Arnoldiella elbakyaniae can be recognized by the heterotrichous thallus with short erect, unbranched or sparsely branched filaments, and by the short and enlarged basal cells of the erect system. The new species differs from A. emedii by its shorter basal cells, the narrower and cylindrical axis cells, and the zoosporangia in terminal chains.

Abstract: The Bernardo O’Higgins National Park (BONP) covers a total area of 3,525,901 hectares, where a great diversity of terrestrial and marine habitats converges. Its coastal area is characterized by a complex system of Patagonian Channels and Fjords. This marine ecosystem does not have an ecological simile with other along the Souther Pacific coast, with a high biodiversity in its marine biota, specifically in its marine benthic algae. There are few or almost no scientific contributions regarding which species of macroalgae inhabit this conservation area between ~ 49° - 55° of South latitude. Therefore, the aim of this work was to be a first qualitative approximation of macroalgae flora in these coastal systems of BONP. In order to corried out the objetive of this work, qualitative subtidal samplings in mover delante de qualitative stations on the coast of the BONP, through SCUBA diving during the summer of 2010. A total of 64 taxa were of subtidal benthic macroalgae belong to 31 families. The most diverse taxa was the Delesseriaceae (8 species), followed by Ceramiaceae (7 species) and Ulvaceae (7 species). In addition, we observed that Macrocystis pyrifera is the dominant subtidal macroalgae species in the whole study area. This work contributed to the phycological knowledge of the Subantarctic ecoregion. However, it is necessary to continue developing research effort in the area, which without a doubt would provide more records to those already achieved.

Resumen: El Parque Nacional Bernardo O'Higgins (PNBO) abarca un área total de 3.525.901 hectáreas, donde confluyen una gran diversidad de hábitats terrestres y marinos. Su área costera está caracterizada por la presencia de un complejo sistema de Canales y Fiordos Patagónicos. Este tipo de ecosistema marino, no poseen un símil ecológico en otro ambiente a lo largo de la costa del Pacífico Suroriental, con una alta biodiversidad en su biota marina, específicamente en su flora marina bentónica. Existen pocas o casi ninguna contribución científica respecto a que especies de macroalgas habitan esta área de conservación entre ~49° - 55° de latitud Sur. Este trabajo tiene como objetivo ser una primera aproximación cualitativa de la flora macroalgal en estos sistemas costeros del PNBO. Para lo cual, se realizaron muestreos submareales cualitativos en 19 estaciones en la costa del PNBO, mediante buceo autónomo durante el verano de 2010. Se determinaron un total de 64 taxa de macroalgas bentónicas submareales. Estas macroalgas se distribuyeron en 31 familias, siendo las más representadas las Delesseriaceae (8 especies), seguido de Ceramiaceae (7 especies) y Ulvaceae (7 especies). Además, se logró observar que Macrocystis pyrifera es la especie de macroalga submareal dominante en el área de estudio. Este trabajo pretende ser un real aporte al conocimiento de la flora ficológica de la ecorregión Subantártica, sin embargo, es necesario seguir desarrollando esfuerzo de investigación en el área, que sin lugar a duda aportarían más registros a los ya logrados.

Abstract Background Most studies on benthic diatoms found in northwestern Mexico have been done along the western coast of the Baja California peninsula. Thus, few studies exist for the Gulf of California. Goals To gather new records of benthic diatoms found in the Gulf of California. Methods Diatom samples from sediments and rocks of the coast of Santa Rosalía, Baja California Sur, were observed under a light microscope (LM). Results Three taxa were recorded and depicted: Caloneis liber var. bicuneata (common), Gyrosigma naja (scarce), and the new combination Entomoneis pulchra var. pulchella (scarce). Conclusions These three taxa were recorded for the first time in northwestern Mexico.

Resumen Antecedentes Los estudios sobre diatomeas bentónicas para el Noroeste mexicano se han hecho principalmente para la costa occidental de la península de Baja California, pero son pocos para el golfo de California. Objetivos Presentar nuevos registros de diatomeas bentónicas para el golfo de California. Métodos Se observaron muestras de diatomeas de sedimentos y rocas de la costa de Santa Rosalía, Baja California Sur, México bajo el microscopio de luz. Resultados Se registraron tres nuevos taxa: Caloneis liber var. bicuneata (común) y Gyrosigma naja (raro), y la nueva combinación Entomoneis pulchra var. pulchella (raro). Conclusiones Estos tres taxa son registrados por primera vez para la región Noroeste de México.

Resumo: Gomphonema Ehrenberg é um gênero bem representado na flora algal perifítica de ambientes epicontinentais. A colonização de substratos é facilitada pela secreção de mucilagem pelo campo de poros permitindo a adesão das células. As amostras analisadas foram removidas das porções vegetativas da macrófita Eichhornia azurea Kunth, coletadas no rio São Francisco Falso, localizado no município de Santa Helena, Paraná. As coletas ocorreram em quatro estações de amostragem, em quatro períodos diferentes, totalizando 16 amostras. A análise qualitativa do material resultou na identificação de 28 táxons, sendo que Gomphonema brasiliense ssp. pacificum, Gomphonema neoapiculatum Lange-Bertalot, Reichardt & Metzeltin Gomphonema pantropicum Reichardt e Gomphonema perapicatum Metzeltin & Lange-Bertalot constituíram citações pioneiras para a diatomoflórula do Paraná. As observações da ultra-estrutura de algumas espécies foram decisivas para distinção entre alguns táxons, como por exemplo, Gomphonema brasiliense Grunow e Gomphonema brasiliensoide D. Metzeltin, Lange-Bertalot & F. García-Rodríguez. Sugerem-se futuros estudos desse ambiente, uma vez que o mesmo possui características propícias ao desenvolvimento de diatomáceas epilíticas, além de estudos filogenéticos para melhor distinção dos táxons com ampla variação morfológica.

Abstract: Gomphonema Ehrenberg is a genus well represented in periphytic algal flora of epicontinental environments. The substrate colonization is facilitated by the secretion of mucilage by the pore field, allowing cell adhesion. Samples were scraped off and analyzed from vegetative portions of the macrophyte Eichhornia azurea Kunth, collected in São Francisco Falso River, located in Santa Helena City, Paraná State. The sampling occurred in four different sites, in four different periods, totaling 16 samples. The quantitative material analysis resulted in 28 identified taxa, in which Gomphonema brasiliense ssp. pacificum, Gomphonema neoapiculatum Lange-Bertalot, Reichardt & Metzeltin Gomphonema pantropicum Reichardt and Gomphonema perapicatum Metzeltin & Lange-Bertalot represented pioneer citations for Paraná diatomflorula. The ultrastructure observations of some species were crucial to distinguish a few taxa, as Gomphonema brasiliense and Gomphonema brasiliensoide D. Metzeltin, Lange-Bertalot & F. García-Rodríguez. We suggest future studies in this environment, once it has propitious characteristics to the development of epilithic diatoms. Moreover, phylogenetic studies are also recommended for a better distinction of taxa with a wide morphologic variation.

Abstract: The epilithic algae and cyanoprokaryotes that inhabit the Archaeological Zone of Yaxchilán, Chiapas, cover most of the walls of buildings; it is a site located in the Lacandon Jungle, next to the Usumacinta river with a very high relative humidity. The aim of this work was to document the species of algae and cyanoprokaryotes that grow on the archaeological monuments of this area, based on the microscopic morphology. From 135 samples collected between 2006 and 2008, 49 species were identified: 25 Chroococcales, 12 Nostocales and 3 Oscillatoriales of Cyanoprokaryota; 3 Chlorellales and 4 Trentepohliales of Chlorophyta and 2 Naviculales of Bacillariophyta. We describe 9 species that are new records for Mexico and all the species found are illustrated as a reference. The ecological valence of the species allows to characterize the flora with affinity to a karst substrate with a basic pH and under fluctuating light, humidity and temperature conditions during the day. Finally, the need to preserve flora and monuments following control strategies based on knowledge of the life cycles of epilithic organisms is pointed out. This is the first study on algae and cyanoprokaryotes in the archaeological zone of Yaxchilán.

Resumen: Las algas y cianoprocariontes epilíticas que habitan en la Zona Arqueológica de Yaxchilán, Chiapas, cubren la mayoría de los muros de los edificios; es un sitio que se encuentra en la Selva Lacandona, junto al río Usumacinta con una humedad relativa muy alta. El objetivo de este trabajo fue documentar las especies de algas y cianoprocariontes que crecen sobre los monumentos arqueológicos de esta zona, con base en la morfología microscópica. De 135 muestras recolectadas entre 2006 y 2008, se identificaron 49 especies: 25 Chroococcales, 12 Nostocales y 3 Oscillatoriales de Cyanoprokaryota; 3 Chlorellales y 4 Trentepohliales de Chlorophyta y 2 Naviculales de Bacillariophyta. Se describen 9 especies que son nuevos registros para México y todas las especies encontradas son ilustradas como referencia. La valencia ecológica de las especies permite caracterizar la flora con afinidad a un sustrato calcáreo con un pH básico y en condiciones de iluminación, humedad y temperatura fluctuantes durante el día. Finalmente, se señala la necesidad de conservar la flora y los monumentos siguiendo estrategias de control basadas en el conocimiento de los ciclos de vida de los organismos epilíticos. Este es el primer estudio sobre las algas y cianoprocariontes de la zona arqueológica de Yaxchilán.

Abstract: The knowledge of the continental algae from Mexico is far to be complete. The taxonomic records currently reach 3 256 species, but many of them lack a description, an illustration or both, as well as information about their ecology or economic potential. Studies contributing to the knowledge of Mexican species come mainly from the states of Michoacan, Mexico, Puebla, Oaxaca, and Mexico City; the rest of the country is practically unexplored. Such is the case of Nuevo Leon, where until 2011 its 21 records represented scarcely 0.64% of nation diversity. This lack of information about a potentially important resource motivated the gathering of algal records and prospecting of different water bodies in the center of the state, in order to determine the species of algae. To make it, historical reports of genera and species up to 2015 were compiled and the information was complemented by transect sampling of benthos in 30 stations in the period 2014-2016. The results represent a relative increase of 324% on previous phycologycal knowledge and are presented as a taxonomic list for the state, which consists of 68 species distributed in 51 genera and 37 families. Most of the species are epilithic or planthonic and have a cosmopolitan distribution.

Resumen: El conocimiento de las algas continentales de México es aún deficiente. Los registros taxonómicos suman actualmente 3 256 especies, pero muchos de ellos carecen de una descripción, una ilustración o de ambas, además de información ecológica o de su potencial económico. Los estudios que contribuyen a esta cifra sobre la riqueza específica nacional provienen principalmente de los estados de Michoacán, Ciudad de México, Estado de México, Puebla y Oaxaca, el resto del país está prácticamente inexplorado. Tal es el caso del estado de Nuevo León, donde hasta el 2011 sus 21 registros representaban apenas un 0.64% de la riqueza del país. El desconocimiento de este recurso, potencialmente importante, motivó realizar una prospección en distintos cuerpos de agua del centro del estado, con la finalidad de determinar las especies presentes y con ello, elaborar una lista de especies actualizada. Para este fin se compilaron los reportes históricos de géneros y especies hasta el 2015 y se realizaron muestreos bénticos por medio de transectos en 30 estaciones en el periodo de 2014-2016. Los resultados representan un aumento relativo sobre el conocimiento ficológico previo de un 324% y se presentan como un listado taxonómico para el estado, el cual ahora consta de 68 especies distribuidas en 51 géneros y 37 familias. La mayoría de las especies son epilíticas o planctónicas y tienen una distribución cosmopolita.

Resumo Objetivo: O objetivo deste estudo foi avaliar os aspectos taxonômicos e a distribuição geográfica das desmídias perifíticas de dois substratos diferentes na zona litorânea de um lago artificial urbano. Métodos Amostras de desmídias epífitas e epilíticas foram coletadas por raspagem de gramíneas e rochas, respectivamente, em duas estações no lago municipal de Cascavel, Paraná, durante abril de 2015 e março de 2016 e 2017. No laboratório, os táxons obtidos a partir das amostras foram fotografados e suas características morfométricas foram registradas. A composição das espécies de desmídias foi caracterizada e a frequência de ocorrência, bem como a distribuição geográfica de cada táxon no Estado do Paraná foram registradas. Resultados Nós identificados 35 táxons, distribuídos em 10 gêneros. Os gêneros mais representativos foram Closterium Nitzsch ex Ralfs e Cosmarium Corda ex Ralfs. Uma alta ocorrência de táxons esporádicos (60%) foi observada, e entre os táxons registrados, os mais frequentes foram Cosmarium pseudoconnatum Nordstedt var. pseudoconnatum e Desmidium grevillei (Kützing ex Ralfs) De Bary. Nove táxons foram exclusivos para o substrato epilítico e somente Netrium digitus (Ralfs) Itzigsohn & Rothe var. digitus foi exclusivo para o substrato epifítico, enquanto os demais 25 táxons ocorreram em ambos os substratos. Sete táxons são novas ocorrências para o estado do Paraná. Conclusão Embora nossos resultados sejam de natureza qualitativa, eles fornecem uma base de dados sobre a distribuição biogeográfica dos táxons, os quais são cruciais para futuros estudos taxonômicos e ecológicos que podem contribuir para a preservação da biodiversidade.

Abstract Aim: The aim of this study was to assess the taxonomic aspects and geographical distribution of the periphytic desmids from two different substrates in the littoral zone of an urban artificial lake. Methods Samples of epiphytic and epilithic desmids were collected by grass and rock scraping, respectively, in two stations in the Cascavel municipal lake, Paraná, during April 2015, and March 2016 and 2017. In the laboratory, the taxa obtained from the samples were photographed and their morphometric characteristics recorded. The species composition of the desmid was characterized, and the frequency of occurrence as well as the geographic distribution of each taxon in the Paraná State were recorded. Results We identified 35 taxa, distributed in 10 genera. The most representative were Closterium Nitzsch ex Ralfs and Cosmarium Corda ex Ralfs. A high occurrence of sporadic taxa (60%) was observed and among the recorded taxa, the most frequent were Cosmarium pseudoconnatum Nordstedt var. pseudoconnatum and Desmidium grevillei (Kützing ex Ralfs) De Bary. Nine taxa were exclusive to the epilithic substrate and only Netrium digitus (Ralfs) Itzigsohn & Rothe var. digitus was exclusive to the epiphytic substrate, while the remaining 25 taxa occurred in both substrates. Seven taxa are new records for the Paraná State. Conclusion Although our results are of qualitative nature, they provide baseline data on the biogeographic distribution of taxa, which are crucial for future taxonomic and ecological studies that might contribute to the preservation of the biodiversity.