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Se presentan los desafíos y oportunidades generados a partir de la delimitación de los nuevos límites exteriores de la Plataforma Continental Argentina. En ese contexto se propone el desarrollo de una política activa de investigación científica enfocada en el ambiente bentónico, por el impacto que tendría en la reafirmación de la soberanía nacional y en el desarrollo de actividades productivas. Se propone priorizar aquellas zonas donde actualmente existen actividades problemáticas para nuestro país, y donde se necesita contar con mejor información científica, tanto para realizar una explotación de recursos estratégicos, como para instalar herramientas de conservación de la biodiversidad, como por ejemplo Áreas Marinas Protegidas. Por ello, se postula al sector del Agujero Azul que incluye tanto el sector dentro de la Zona Económica Exclusiva Argentina como la zona adyacente en alta mar, como principal objetivo inmediato para investigaciones de aspectos referidos a la ecología bentónica y estudios oceanográficos y pesqueros asociados., The challenges and opportunities generated from the delimitation of the new outer limits of the Argentine Continental Shelf are presented. In this context, the development of an active policy of scientific research focused on the benthic environment is proposed, due to the impact it would have on the reaffirmation of national sovereignty and on the development of productive activities. It is proposed to prioritize those areas where there are currently problematic activities for our country, and where better scientific information is needed, both to exploit strategic resources, and to install biodiversity conservation tools, such as Marine Protected Areas. For this reason, the Blue Hole sector is proposed, which includes both the sector within the Argentine Exclusive Economic Zone and the adjacent area on the high seas, as the main immediate objective for investigations of aspects related to benthic ecology and associated oceanographic and fishing studies., Neste artigo, apresentamos as oportunidades e desafios gerados a partir da delimitação dos novos limites externos da Plataforma Continental Argentina. Nesse contexto, propõe-se o desenvolvimento de uma política ativa de pesquisa científica voltada para o meio bentônico, pelo impacto que teria na reafirmação da soberania nacional e no desenvolvimento das atividades produtivas. Propomos priorizar as áreas onde atualmente existem atividades problemáticas para o nosso país e onde se faz necessária uma melhor informação científica, tanto para explorar recursos estratégicos, como para instalar ferramentas de conservação da biodiversidade, como no caso das Áreas Marinhas Protegidas. Por essa razão, propomos o setor Blue Hole, que inclui tanto o setor dentro da Zona Econômica Exclusiva Argentina enquanto área adjacente em alto mar, como o principal objetivo imediato para investigações de aspectos relacionados à ecologia bentônica e estudos oceanográficos e pesqueiros associados., Cátedra Libre Ciencia, Política y Sociedad

Diel vertical migration (DVM) is the most common behavioral phenomenon in zooplankton, and numerous studies have evaluated DVM under strong seasonality at higher latitudes. Yet, our understanding of the environmental drivers of DVM at low latitudes, where seasonal variation is less pronounced, remains limited. Therefore, we here examined patterns of vertical distribution in copepods in six subtropical Bahamian blue holes with different food web structure and tested the role of several key environmental variables potentially affecting this behavior. Day and night samplings showed that copepods generally performed DVM, characterized by downward migration to deeper depths during the day and upward migration to surface waters at night. Across all blue holes, the daytime vertical depth distribution of calanoid copepods correlated positively with both predation risk and depth of food resources (Chlorophylla), but was less affected by ultraviolet radiation (UVR). A potential explanation is that since UVR is a continuous threat across seasons, zooplankton have established photoprotective pigmentation making them less vulnerable to this threat. The copepods also showed a size-structured depth segregation, where larger individuals were found at deeper depths during the day, which further strengthens the suggestion that predation is a major driver of DVM in these systems. Hence, in contrast to studies performed at higher latitudes, we show that despite the constant exposure to UVR, predator avoidance and food availability are the most pronounced drivers of copepod DVM at those low latitudes, suggesting that the main driver of DVM may vary among systems, but also systematically by latitude.

In this paper we have explored for the first time the biodiversity pattern of the meiobenthic assemblage in a Blue Hole of the Maldivian Archipelago. The cave is characterised by a marked change of the chemical water parameters below 50 m of depth, with a relevant increase in hydrogen sulfide, carbon dioxide, and sulfates (H2S, CO2 and SO42–). Thus, three stations were selected above and two below the chemo-thermocline in order to test the possible effects of the chemical variations on the meiobenthos. The difficulty of adaptation to these environmental conditions is clearly suggested by the presence of only a few dominant meiobenthic taxa in the bottom of the cave. However, meiobenthic organisms seemed more resistant than macrobenthos, which disappeared completely below this depth. The nematode assemblage was mainly represented by Xyalidae, Desmodoridae, Comesomatidae and Linhomoeidae. A high level of confinement of nematode genera at the different depths has been documented. In the upper part, t...

Karst of Yucatàn : Role of geothermal flux, faults, sea water, and evaporites in its genesis. The caver who dives in Yucatan caves finds out that the saltwater underlying the halocline is warmer than the overlying freshwater. He also notes that there are differences in temperature from one cenote to the other. How can we explain these temperature differences ? Why is the saline aquifer warmer than the freshwater aquifer ? These temperature gaps actually indicate a mode of heat transfer by convection from geothermal sources and the existence of two systems of thermal plumes (freshwater and saltwater). The platform of Yucatan was the subject of intense caving exploration and many physico-chemical measurements, which allowed us to quantify the magnitudes of these phenomena. Numerical modeling is used to define conditions for the establishment of such flow regimes and stresses the importance of hydraulic conductivity and the role of fracturing. The contribution of the geochemistry of freshwater is used to evaluate the depth to which thermal plumes are formed. The analysis of heat exchange with the deep waters of the Caribbean Sea and the antagonistic role of the Yalahau laguna are advanced to explain the «cold» area in the north of the peninsula. The mechanisms of karstification, amplified by feedback effects that result from these movements of water, are outlined. The genesis of the blue holes and the existence of short horizontal tunnels at the halocline level can be explained this way. The deep dissolution of Cretaceous evaporites particularly in the area of Lake Chichencanab is evaluated, thus providing a novel interpretation of the existence of large collapse structures visible in satellite photography in this area. These karstic phenomena are not directly influenced by rainfall, the dissolution «engine» being only heat flow, and thus can be classified as hypogenic., Dans les karsts à lentille d'eau douce, le plongeur souterrain qui franchit l'halocline découvre que l'eau salée sous-jacente est plus chaude que l'eau douce surnageante. Il constate aussi qu'il existe des cénotes «chauds » et des cénotes «froids ». Comment expliquer ces disparités thermiques ? Pourquoi l'aquifère salin est-il plus chaud que l'aquifère d'eau douce ? Ces sauts de température indiquent en fait un mode de transfert de la chaleur d'origine géothermique par convections et l'existence de deux systèmes de panaches thermiques (eau douce et eau salée). La plateforme du Yucatan a fait l'objet d'explorations spéléologiques intenses et de nombreuses mesures physico-chimiques, ce qui nous a permis de quantifier les ordres de grandeurs de ces phénomènes. La modélisation numérique permet de définir l'existence des conditions d'établissement de tels régimes d'écoulement et souligne l'importance de la conductivité hydraulique et du rôle de la fracturation. L'apport de la géochimie des eaux douces permet d'évaluer la profondeur à laquelle se forment les panaches thermiques. L'analyse des échanges thermiques avec les eaux profondes de la mer Caraïbe ainsi que le rôle antagoniste de la lagune de Yalahau sont avancés pour expliquer la zone «froide » située au nord-est de la péninsule. Les mécanismes de karstification, amplifiés par des effets rétroactifs qui résultent de ces mouvements d'eau sont développés. La genèse des blue holes et l'existence de courtes galeries horizontales au niveau de l'halocline peuvent s'expliquer de cette façon. L'ablation karstique des évaporites du Crétacé notamment dans la zone du lac de Chichencanab est évaluée, ce qui apporte une interprétation inédite de l'existence de grandes structures d'effondrement visibles en photographie satellite dans cette zone. Ces phénomènes de creusement karstique, de nature hypogène, ne sont pas directement influencés par la pluviométrie, le «moteur » d'écoulement étant uniquement thermique., El carst del Yucatan : su genesis y la funcion del flujo geotérmico, de la fracturacion y del agua del mar. La meseta de Yucatan ha sido objeto de intensas exploraciones espeleolôgicas y de numerosas medidas fisico-quimicas. Se ha constatado, por ejemplo, la existencia des cénotes calientes y de cénotes frios. ¿ Cômo se explican esas diferencias térmicas ? ¿ Por qué los acuiferos de agua salada son mâs calientes que los acuiferos de agua dulce ? La modelizaciôn numérica permite définir la existencia de condiciones para el establecimiento de taies regimenes de flujo y subraya la importancia de la conductividad hidrâulica y del pape I de la fractura. La aportaciôn de la geoquimica de agua dulce permite de examinar la profundidad a la que se forman las variaciones térmicas. El anâlisis de los intercambios térmicos con las aguas profundas del Mar Caribe, asi como el papel antagonista de la laguna de Yalahu, son anticipos para explicar la zona "fria" situada al norte de la peninsula. Los mecanismos de carstificaciôn se desarrollan ampliados por los efectos retroactivos résultantes de esos movimientos de agua. De esta manera, se pueden explicar el origen de los blue holes y la existencia de galerias cortas horizontales en el nivel del haloclino. Estos fenômenos de excavaciôn cârstica, de naturaleza hipogénica, no estân directamente afectados por la pluviometria, siendo el "motor" del flujo unicamente térmico., Thomas Christian. Le karst du Yucatàn : rôle du flux géothermique, des failles, de l'eau de mer et des évaporites dans sa genèse. In: Karstologia : revue de karstologie et de spéléologie physique, n°55, 1er semestre 2010. Le karst du Yucatan (Mexique) pp. 1-18.