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Abstract Invasion of ocean surface waters by anthropogenic CO 2 emitted to the atmosphere is expected to reduce surface seawater pH to 7.8 by the end of this century compromising marine calcifiers. A broad range of biological and mineralogical mechanisms allow marine calcifiers to cope with ocean acidification, however these mechanisms are energetically demanding which affect other biological processes (trade-offs) with important implications for the resilience of the organisms against stressful conditions. Hence, food availability may play a critical role in determining the resistance of calcifiers to OA. Here we show, based on a meta-analysis of existing experimental results assessing the role of food supply in the response of organisms to OA, that food supply consistently confers calcifiers resistance to ocean acidification.
Abstract. Carbon dioxide and coupled CO2 and O2-driven compromises to marine life were examined along the Chilean sector of the Humboldt Current System, a particularly vulnerable hypoxic and upwelling area, applying the Respiration index (RI = log10 pO2pCO2) and the pH-dependent aragonite saturation (Ω) to delineate the water masses where aerobic and calcifying organisms are stressed. As expected, there was a strong negative relationship between oxygen concentration and pH or pCO2 in the studied area, with the subsurface hypoxic Equatorial Subsurface Waters extending from 100 m to about 300 m depth and supporting elevated pCO2 values. The lowest RI values, associated to aerobic stress, were found at about 200 m depth and decreased towards the Equator. Increased pCO2 in the hypoxic water layer reduced the RI values by as much as 0.59 RI units, with the thickness of the upper water layer that presents conditions suitable for aerobic life (RI>0.7) declining by half between 42° S and 28° S. The intermediate waters hardly reached those stations closer to the equator so that the increased pCO2 lowered pH and the saturation of aragonite. A significant fraction of the water column along the Chilean sector of the Humboldt Current System suffers from CO2–driven compromises to biota, including waters corrosive to calcifying organisms, stress to aerobic organisms or both. The habitat free of CO2-driven stresses was restricted to the upper mixed layer and to small water parcels at about 1000 m depth. Overall pCO2 acts as a hinge connecting respiratory and calcification challenges expected to increase in the future, resulting in a spread of the challenges to aerobic organisms.
Las empresas son quizás una de las más extendidas formas de organización social de la actualidad. Como bien sabemos, estas responden a una particular manera de formalizar la contradicción clásica entre capital y trabajo, respondiendo a diversas necesidades del mercado o de una comunidad. Estas, además de responder a una función económica, están formadas por personas y para personas, lo que significa que se encuentran circunscritas a los contextos sociales que las originan. A pesar de su importancia, nuestra capacidad para pensar las empresas parece más bien limitada. Por una parte, los debates parecen remitirse a reflexiones apologéticas y narrativas institucionales, que en el mejor de los casos desembocan en los modernos discursos de sostenibilidad empresarial. Por otra parte, los ejercicios analíticos realizados desde las ciencias sociales caen fácilmente en posiciones binarias que tienden a estigmatizar de facto el rol empresarial en cualquier contexto en el que se mencione. Por lo anterior, la presente convocatoria de la edición 212 de la Revista Controversia invitó a reflexionar en torno a los diferentes modelos empresariales que conviven, compiten, dinamizan y entran en conflicto con diversos sectores de la sociedad colombiana, especialmente los de su entorno. En términos generales, se buscó comprender los vínculos y las tensiones entre el sector privado empresarial y las diversas comunidades, especialmente rurales.
Plant mortality and birth rates are critical components of plant life history affecting the stability of plant populations and the ecosystems they form. Although allometric theory predicts that both plant birth and mortality rates should be size-dependent, this prediction has not yet been tested across plants ranging the full size spectrum. Here we show that both population mortality and population birth rates scale as the -(1/4) power and plant lifespan as the (1/4) power of plant mass across plant species spanning from the tiniest phototrophs to the largest trees. Whereas the controls on plant lifespans are as yet poorly understood, our findings suggest that plant mortality rates have evolved to match population birth rates, thereby helping to maintain plant communities in equilibrium and optimizing plant life histories.