Effects of climate change on Mediterranean marine ecosystems: the case of the Catalan Sea

29 pagex, 9 figures, 2 tablesThe Catalan Sea, located between the eastern Iberian coast and the Balearic Islands, is a representative portion of the western Mediterranean basin and provides a valuable case study for climate change effects on Mediterranean ecosystems. Global warming is reflected regionally by a rise in sea level over the last century, an increase in surface temperature of around 1.1°C in the last 35 yr, a progressive salinisation of intermediate and deep waters and a strengthening of the stratification. A likely scenario of what we can expect in the Mediterranean Sea is a considerable decrease in rainfall and wind, warmer surface waters and a prolonged stratification period. The effects on Mediterranean ecosystems are evident in: (1) a meridionalisation of the algal, invertebrate and vertebrate species, which favours the more thermophilic species over the temperate species; (2) mass mortality events of sessile invertebrates of the coralligenous communities owing to anomalous warm waters during the period when food is scarce; (3) increases in the smallest phytoplankton due to the prolongation of the water stratification period; (4) proliferation of gelatinous carnivores, including jellyfish, due to the temperature rise and the lack of rainfall; (5) a faster acidification of seawater, compared with the global oceans, accompanied by a decrease in the capacity to absorb atmospheric CO2. In order to anticipate and mitigate these predicted changes, we recommend investing in research and observation, conserving areas that serve as indicators of climate change and reducing other anthropogenic pressures such as habitat destruction, overfishing or pollution, which may act synergistically to accelerate these changes.E.C., C.P., M.R. and R.C. acknowledge funding from the Spanish Ministerio de Ciencia e Innovación through grants CTM2009-08849/MAR, CTM2006-01463 and CGL2007-66757-C02-01/BOS and a Ramón y Cajal contract to E.C. This paper is a contribution from the Marine Biogeochemistry and Global Change research group, funded by Generalitat de Catalunya (Catalan Government) through grant 2009SGR142.Peer reviewe

Evaluación del problema de la acidificación en el Mediterráneo mediante series temporals de pH y experimentos con corales

Ponencia presentada en: VI Congreso Internacional de la Asociación Española de Climatología celebrado en Tarragona del 8 al 11 de octubre de 2008.[ES]El incremento de los niveles de CO2 atmosférico y la elevada absorción de éste por los mares y océanos está provocando una acidificación progresiva de los mismos. Las predicciones apuntan hacia una acidificación entre 0.3 y 0.5 unidades de pH en el año 2100 y cerca de 0.8 unidades de pH en el año 2300, un escenario sin precedentes para los últimos cientos de millones de años. En el caso concreto del Mar Mediterráneo, aún no está claro cual es la velocidad de absorción del CO2 antropogénico y la consecuente reducción de pH, aunque, debido a su reducida extensión, es posible que esta acidificación sea más severa que en los océanos del planeta.[EN]The increasing CO2 levels in the atmosphere and its high uptake by the oceans are lowering the pH of the oceans. Predictions point towards acidification of 0.3 to 0.5 pH units by year 2100 and of nearly 0.8 pH units by year 2300, a scenario for which there is no obvious precedent over the last hundreds of millions of years. In the specific case of the Mediterranean Sea, it is still not clear how rapidly it is absorbing anthropogenic CO2 and thus lowering its pH but, owing to its smaller size, there is the possibility that the lowering of pH may be more severe and abrupt than in the world oceans.Este trabajo forma parte del proyecto ROMIAT (CTM2006-01957/MAR), financiado por el Ministerio de Educación y Ciencia, y es una de las actividades del Grup de Recerca en Biogeoquímica Marina i Canvi Global (2005SGR00021), financiado por la Generalitat de Catalunya. Juancho Movilla está financiado mediante una beca FPI (BES-2007-16537) del Ministerio de Educación y Ciencia

Biodiversity loss in a Mediterranean ecosystem due to an extreme warming event unveils the role of an engineering gorgonian species

Stochastic perturbations can trigger major ecosystem shifts. Marine systems have been severely affected in recent years by mass mortality events related to positive thermal anomalies. Although the immediate effects in the species demography affected by mortality events are well known, information on the mid- to long-term effects at the community level is much less documented. Here, we show how an extreme warming event replaces a structurally complex habitat, dominated by long-lived species, by a simplified habitat (lower species diversity and richness) dominated by turf-forming species. On the basis of a study involving the experimental manipulation of the presence of the gorgonian Paramuricea clavata, we observed that its presence mitigated the effects of warming by maintaining the original assemblage dominated by macroinvertebrates and delaying the proliferation and spread of the invasive alga Caulerpa cylindracea. However, due to the increase of sediment and turf-forming species after the mortality event we hypothesize a further degradation of the whole assemblage as both factors decrease the recruitment of P.clavata, decrease the survival of encrusting coralligenous-dwelling macroinvertebrates and facilitate the spreading of C. cylindracea

Heterotrophy in the earliest gut: a single-cell view of heterotrophic carbon and nitrogen assimilation in sponge-microbe symbioses

Sponges are the oldest known extant animal-microbe symbiosis. These ubiquitous benthic animals play an important role in marine ecosystems in the cycling of dissolved organic matter (DOM), the largest source of organic matter on Earth. The conventional view on DOM cycling through microbial processing has been challenged by the interaction between this efficient filter-feeding host and its diverse and abundant microbiome. Here we quantify, for the first time, the role of host cells and microbial symbionts in sponge heterotrophy. We combined stable isotope probing and nanoscale secondary ion mass spectrometry to compare the processing of different sources of DOM (glucose, amino acids, algal-produced) and particulate organic matter (POM) by a high-microbial abundance (HMA) and low-microbial abundance (LMA) sponge with single-cell resolution. Contrary to common notion, we found that both microbial symbionts and host choanocyte (i.e. filter) cells and were active in DOM uptake. Although all DOM sources were assimilated by both sponges, higher microbial biomass in the HMA sponge corresponded to an increased capacity to process a greater variety of dissolved compounds. Nevertheless, in situ feeding data demonstrated that DOM was the primary carbon source for both the LMA and HMA sponge, accounting for ~90% of their heterotrophic diets. Microbes accounted for the majority (65–87%) of DOM assimilated by the HMA sponge (and ~60% of its total heterotrophic diet) but <5% in the LMA sponge. We propose that the evolutionary success of sponges is due to their different strategies to exploit the vast reservoir of DOM in the ocean

In situ Pumping Rate of 20 Marine Demosponges Is a Function of Osculum Area

Sponges play a key role in the transfer of energy and nutrients into many benthic ecosystems, and the volume of water they process is an important regulator of these fluxes. Theoretical scaling relationships between sponge volume, osculum cross-sectional area, and pumping rates were recently proposed and confirmed for small sponge specimens in the lab. To examine how these relationships apply to field populations we measured, in situ, the pumping rate (PR) of 20 species representative of different morphologies and host types (high- and low-microbial-abundance, HMA and LMA) from temperate and tropical regions. The total oscula area (∑OSA) increased allometrically with sponge volume (V) exhibiting similar exponents (∑OSA=aVb, b ranging 0.6–0.7) for all species, except for tropical HMAs (b = 0.99). Osculum flow rate (OFR) also increased allometrically with OSA and oscula of the same size pumped at the same rate irrespective of sponge volume. As a result, and in contrast to former reports, the PR of most of the sponges increased allometrically (PR=a∑OSAb) with scaling exponent b≈0.75, whereas PR of tropical HMAs increased isometrically. Osculum jet speed declined with the increase in the OSA for most species. The number of oscula and their OSA were the best predictors of the PR in sponges, explaining 75–94% of the in situ variation in PR throughout the natural range of sponge size. The pumping rate of a sponge population can be estimated by measuring the osculum density and cross-sectional area distribution once the relationships between the OSA and OFR are established for each species

Sea Urchins Predation Facilitates Coral Invasion in a Marine Reserve

Macroalgae is the dominant trophic group on Mediterranean infralittoral rocky bottoms, whereas zooxanthellate corals are extremely rare. However, in recent years, the invasive coral Oculina patagonica appears to be increasing its abundance through unknown means. Here we examine the pattern of variation of this species at a marine reserve between 2002 and 2010 and contribute to the understanding of the mechanisms that allow its current increase. Because indirect interactions between species can play a relevant role in the establishment of species, a parallel assessment of the sea urchin Paracentrotus lividus, the main herbivorous invertebrate in this habitat and thus a key species, was conducted. O. patagonica has shown a 3-fold increase in abundance over the last 8 years and has become the most abundant invertebrate in the shallow waters of the marine reserve, matching some dominant erect macroalgae in abundance. High recruitment played an important role in this increasing coral abundance. The results from this study provide compelling evidence that the increase in sea urchin abundance may be one of the main drivers of the observed increase in coral abundance. Sea urchins overgraze macroalgae and create barren patches in the space-limited macroalgal community that subsequently facilitate coral recruitment. This study indicates that trophic interactions contributed to the success of an invasive coral in the Mediterranean because sea urchins grazing activity indirectly facilitated expansion of the coral. Current coral abundance at the marine reserve has ended the monopolization of algae in rocky infralittoral assemblages, an event that could greatly modify both the underwater seascape and the sources of primary production in the ecosystem

Seguiment temporal de la gorgònia Paramuricea clavata de les Illes Medes. Exercici 1999

Podeu consultar l'Informe complet a: http://hdl.handle.net/2445/2366

Seguiment temporal de la gorgònia Paramuricea clavata de les Illes Medes. Exercici 1997

Podeu consultar l'Informe complet a: http://hdl.handle.net/2445/2366