Resumen Las macroalgas dependen de sustratos específicos para su crecimiento y propagación. Esta relación es importante para comprender el funcionamiento de los arrecifes de coral. En México, sin embargo, los estudios sobre este tema son escasos. Así, en el presente estudio se determinó la diversidad de especies de macroalgas en el Parque Nacional Arrecifes de Xcalak (PNAX), en relación con el sustrato que colonizan. En julio del 2012, se seleccionaron 10 sitios de muestreo en 4 zonas del PNAX: canal de Zaragoza (C), laguna arrecifal 1 (LA1), laguna arrecifal 2 (LA2), y arrecife frontal (AF). Con ayuda de transectos y cuadrantes se recolectaron manualmente especímenes de 61 taxones de macroalgas (entre ellos un morfotipo), principalmente rodofitas, sobre 3 sustratos abióticos y 18 bióticos. De estos taxones, 17 especies constituyeron nuevos registros para el PNAX y 1 para la costa de Quintana Roo. La diversidad fue mayor en LA (3.89), seguido de AF (3.71), observando especies comunes entre ambas zonas. Las familias Halimedaceae, Udoteaceae y Anadyomenaceae se observaron creciendo sobre sustrato abiótico, mientras que las familias Halimedaceae y Dictyotaceae constituyeron sustrato para otras rodofitas. El número de macroalgas registrado en el PNAX representa 10.4% del total registrado para la costa de Quintana Roo.

Abstract Macroalgae depend on specific substrata for their growth and propagation. This relationship is essential to understand the functioning of coral reefs. In Mexico, however, studies on this subject are scarce. Therefore, in the present study, the diversity of macroalgae species in the Xcalak Reefs National Park (PNAX) was determined in relation to the substrata they colonize. In July 2012, 10 sampling sites were selected in 4 zones of the PNAX: Zaragoza Canal (C), Lagoon Reef 1 (LA1), Lagoon Reef 2 (LA2), and Fore Reef (AF). With the help of transects and quadrants, specimens of 61 taxa of macroalgae (among them a morphotype) were collected manually, mainly Rhodophyta, on 3 abiotic and 18 biotic substrata. Of these taxa, 17 species were new records for the PNAX and 1 for the Quintana Roo’s coast. The diversity was higher in LA (3.89), followed by AF (3.71), observing common species between both zones. The families Halimedaceae, Udoteaceae, and Anadyomenaceae were observed growing on abiotic substrata, while the families Halimedaceae and Dictyotaceae constituted substrata for other Rhodophyta. The number of macroalgae registered in the PNAX represents 10.4% of the total registered for Quintana Roo’s coast.

Abstract We present the first records of ophiuroids found in 6 tropical coastal lagoons of the northern Yucatán Peninsula. Specimens were collected from Ría Celestún, Chelem, Dzilam, Ría Lagartos, Yalahau, and Nichupté-Bojórquez lagoons, during May and June 2010. Six species belonging to the families Amphiuridae, Ophionereididae, and Ophiodermatidae were recorded. Amphiodia pulchella was recorded in all lagoons; Ophiostigma isocanthum was recorded only in Yalahau, and Ophionereis olivacea and Ophioderma appressa were recorded only in Nichupté- Bojórquez. Amphiodia cf. planispina was recorded in all the coastal lagoons except in Yalahau; all the individuals of this species were juveniles. Finally, Ophiophragmus filograneus was recorded in Ría Celestún, Ría Lagartos, and Nichupté-Bojórquez, being a new record for the southern Gulf of Mexico. The range of distribution of these species is extended and their presence in brackish waters is recorded, an environment that has not been properly studied concerning ophiuroids.

Resumen Presentamos los primeros registros de ofiuroideos encontrados en 6 lagunas costeras tropicales del norte de la península de Yucatán. Los especímenes provienen de las lagunas Ría Celestún, Chelem, Dzilam, Ría Lagartos, Yalahau y Nichupté-Bojórquez, que fueron muestreados durante mayo y junio 2010. Se recolectaron 6 especies pertenecientes a las familias: Amphiuridae, Ophionereididae y Ophiodermatidae. Amphiodia pulchella se registró en todas las lagunas; Ophiostigma isocanthum se registró solo en Yalahau, y Ophionereis olivacea y Ophioderma appressa se registraron solo en Nichupté-Bojórquez. Amphiodia cf. planispina se registró en todas las lagunas con excepción de Yalahau; todos los individuos de esta especie fueron juveniles. Finalmente, se registró Ophiophragmus filograneus en Ría Celestún, Ría Lagartos y Nichupté-Bojórquez, siendo también un nuevo registro para el sur del Golfo de México. Se amplía el rango de distribución de estas especies y se registra su presencia en aguas salobres, un ambiente que no se ha estudiado adecuadamente con respecto a los ofiuroideos.

Abstract: In the Yalahau coastal lagoon, Quintana Roo, we analyzed spatial (Outer, Sea-lagoon, South, and North zones) and temporal weather-season variations (rainy, nortes, and dry), in physicochemical characteristics of water and sediment. The salinity, soluble reactive silicate (SiRS), and sediment grain size were the variables with the highest spatial and temporal variability: (1) The Outer zone is characterized by marine salinity with little temporal variation, low concentrations of SiRS (<11 µM), and predominantly fine sands; (2) The Sea-lagoon zone has the lowest mean salinity (35.5 psu) and little temporal variation, SiRS concentrations of about 10-15 µM in rainy, and nortes that increased four times in dry, and predominantly coarse sands. (3) The South zone is characterized by mixoeuhaline conditions in nortes and hyperhaline conditions during rains, SiRS concentrations of about 15-20 µM in rains and nortes that increased twofold in dry and predominantly coarse sands; (4) The North zone is characterized by a permanent trend to hyperhaline conditions, concentrations of SiRS > 10 µM during the three seasons that increased up to six times in dry weather, when increased concentrations of ammonium and soluble reactive phosphorus were also observed, and predominantly fine sand. The relatively pristine condition of this protected area suggests that natural factors such as the presence of Thalassia testudinum meadows, the magnitude of freshwater inputs, the decomposition of organic matter, and the entry of exogenous nutrients (e.g., seabird droppings) have a great influence on the environmental heterogeneity of the Yalahau lagoon.

Resumen: Se analizó entre zonas (Externa, Mar-laguna, Sur y Norte) y épocas climáticas (lluvias, nortes y secas) la variación de las características fisicoquímicas del agua y sedimento en la laguna costera Yalahau, Quintana Roo. La salinidad, el silicato reactivo soluble (SiRS) y el tamaño de grano del sedimento fueron las variables que presentaron la mayor variabilidad espacial y temporal: (1) zona Externa, caracterizada por salinidades marinas con escasa variación temporal, concentraciones bajas de SiRS (< 11 µM) y predominio de arenas finas; (2) zona Mar-laguna, presentó la salinidad media mínima (35.5 ups) y escasa variación temporal, concentraciones de SiRS de ~10 a 15 µM en lluvias y nortes que se incrementaron hasta cuatro veces en secas y predominio de arenas gruesas; (3) zona Sur, caracterizada por condiciones mixoeuhalinas en nortes y hiperhalinas en lluvias, concentraciones de SiRS de ~15 a 20 µM en lluvias y nortes que se incrementaron al doble en secas, y predominio de arenas gruesas; y (4) zona Norte, caracterizada por una tendencia permanente a la hiperhalinidad, concentraciones de SiRS > 10 µM durante las tres épocas climáticas que se incrementaron hasta seis veces en secas, cuando también se observaron concentraciones elevadas de amonio y fósforo reactivo soluble, en esta zona predominaron arenas finas. La condición relativamente prístina de esta área natural protegida sugiere que factores naturales como la presencia de praderas del pasto marino Thalassia testudinum, la magnitud de los aportes de agua dulce, la descomposición de materia orgánica y el aporte de nutrientes exógenos (e.g., excretas de aves marinas) ejercen gran influencia sobre la heterogeneidad ambiental de la laguna Yalahau.

Tropical coral reefs are known to exhibit high levels of biodiversity. Amphipod crustaceans are successfully adapted to a wide range of marine habitats in coral reefs, but some regions, such as the Campeche Bank in southern Gulf of Mexico, are poorly studied or even unsurveyed for amphipods. To begin to address this paucity of information, the present study records amphipod species from Isla Pérez, an island of the Alacranes Reef National Park, southern Gulf of Mexico. Twenty sites were sampled in the intertidal zone and shallow water adjacent to the island. Thirty-one species of amphipod were identified, 15 of which represented a geographical range extension to the northern Yucatan Peninsula, with four new records for the Mexican south-east sector of the Gulf of Mexico; nine for the Gulf Coast of Mexico; and two for the entire Gulf of Mexico. Significantly, a difference in faunal composition between windward and leeward areas of the intertidal zone was found.

The Mesoamerican Barrier Reef System (MBRS) extends over 1,000 km along the Caribbean Sea of Mexico, Belize, Guatemala, and Honduras. From 1997 onwards these four countries have considered an initiative to designate the MBRS as a Particularly Sensitive Sea Area (PSSA) by the International Maritime Organization (IMO). The purpose of the initiative is to protect the MBRS against the negative effects of international shipping activities. Such designation would also constitute a mechanism to facilitate conservation and sustainable use of the region's resources. This paper provides a summary of the available information about ecological, socio-economic and shipping activities in the Mexican portion of the MBRS (State of Quintana Roo) that might contribute to the joint countries effort by identifying strengths and weaknesses in complying with the guidelines established by IMO to designate the area as a PSSA.

El Sistema Arrecifal Mesoamericano (SAM) es un área natural que se extiende aproximadamente 1,000 km a través de las costas caribeñas de México, Belice, Guatemala y Honduras. A partir de 1997, los gobiernos de estos cuatro países han considerado una iniciativa para que la Organización Marítima Internacional (OMI) designe al SAM como Zona Marítima Especialmente Sensible (ZMES). La justificación para tal designación sería la protección del SAM contra los efectos negativos del tráfico marítimo internacional. Tal designación constituiría también un mecanismo para conservar su biodiversidad y aprovechar sosteniblemente sus recursos. El presente documento proporciona una síntesis del estado actual de la información sobre las características ecológicas, socioeconómicas y de actividades marítimas sobre la porción mexicana del SAM (Quintana Roo), como una contribución al esfuerzo de protección al identificar fortalezas y debilidades en el cumplimiento de las directrices establecidas por la OMI para la designación del área como ZMES.