1,738 publications from this institution
Out of all the biological carbon (or green carbon) captured in the world, over half is captured by marine living organisms hence it is called blue carbon. Although emissions reductions are currently at the centre of the climate change debate, the critical role that oceans and ocean ecosystems play has been vastly overlooked. The objective of this report is to highlight their essential function in maintaining our climate and to assist policy makers to mainstream an oceans agenda into national and international climate change initiatives.
Atmospheric deposition is an important source of limiting nutrients to the ocean, potentially stimulating oceanic biota. Atmospheric inputs can also deliver important amounts of organic matter, which may fuel heterotrophic activity in the ocean. The effect of atmospheric dry aerosol deposition on the metabolic balance and net production of planktonic communities remains unresolved. Here we report high inputs of aerosol‐bound N, Si, P, Fe and organic C to the subtropical NE Atlantic and experimentally demonstrate these inputs to stimulate autotrophic abundance and metabolism far beyond the modest stimulation of heterotrophic processes, thereby enhancing new production. Aerosol dry deposition was threefold to tenfold higher in the coastal ocean than in the open ocean, and supplied high average (±SE) inputs of organic C (980 ± 220 μ mol C m −2 d −1 ), total N (280 ± 70 μ mol N m −2 d −1 ), Si (211 ± 39 μ mol Si m −2 d −1 ), and labile Fe (1.01 ± 0.19 μ mol Fe m −2 d −1 ), but low amounts of total P (8 ± 1.6 μ mol P m −2 d −1 ) to the region during the study. Experimental aerosol inputs to oceanic planktonic communities from the studied area resulted, at the highest doses applied, in a sharp increase in phytoplankton biomass (sevenfold) and production (tenfold) within 4 days, with the community shifting from a dominance of picocyanobacteria to one of diatoms. In contrast, bacterial abundance and production showed little response. Primary production showed a much greater increase in response to aerosol inputs than community respiration did, so that the P/R ratio increased from around 0.95 in the ambient waters, where communities were close to metabolic balance, to 3.3 at the highest nutrient inputs, indicative of a high excess production and a potential for substantial net CO 2 removal by the community in response to aerosol inputs. These results showed that aerosol inputs are major vectors of nutrient and carbon inputs, which can, during high depositional events, enhance new production in the NE subtropical Atlantic Ocean.
Conservation measures to protect marine life are already paying off. These actions have made it possible to halt the decline of some species and re-establish degraded marine ecosystems. But restoring the health of the ocean on a large scale requires a more active fight against pollution, overfishing and the effects of climate change.
1 Os primeiros passos . . . . . . . . . . . . . . . . . . . . . . 2 2 Relembrando o contexto: Portugal entre 1807 e 1974 . . . . 10 3 Da critica do jornalismo a teorizacao sobre a liberdade de imprensa . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 4 Da teorizacao sobre liberdade de imprensa a teorizacao sobre opiniao publica . . . . . . . . . . . . . . . . . . . . . . . . 36 5 A historia do jornalismo . . . . . . . . . . . . . . . . . . . . 44 6 Conjuntura jornalistica . . . . . . . . . . . . . . . . . . . . 66 7 Jornalistas e vida profissional . . . . . . . . . . . . . . . . . 70 8 Ensino do jornalismo . . . . . . . . . . . . . . . . . . . . . 78 9 Teoria do jornalismo (em geral) . . . . . . . . . . . . . . . . 92 Conclusoes . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158 Bibliografia . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161
Abstract The build‐up of sulphide concentrations in sediments, resulting from high inputs of organic matter and the mineralization through sulphate reduction, can be lethal to the benthos. Sulphate reduction is temperature dependent, thus global warming may contribute to even higher sulphide concentrations and benthos mortality. The seagrass Posidonia oceanica is very sensitive to sulphide stress. Hence, if concentrations build up with global warming, this key Mediterranean species could be seriously endangered. An 8‐year monitoring of daily seawater temperature, the sulphur isotopic signatures of water ( δ 34 S water ), sediment (δ 34 S CRS ) and P. oceanica leaf tissue (δ 34 S leaves ), along with total sulphur in leaves ( TS leaves ) and annual net population growth along the coast of the Balearic archipelago (Western Mediterranean) allowed us to determine if warming triggers P. oceanica sulphide stress and constrains seagrass survival. From the isotopic S signatures, we estimated sulphide intrusion into the leaves ( F sulphide ) and sulphur incorporation into the leaves from sedimentary sulphides ( SS leaves ). We observed lower δ 34 S leaves , higher F sulphide and SS leaves coinciding with a 6‐year period when two heat waves were recorded. Warming triggered sulphide stress as evidenced by the negative temperature dependence of δ 34 S leaves and the positive one of F sulphide , TS leaves and SS leaves . Lower P. oceanica net population growth rates were directly related to higher contents of TS leaves . At equivalent annual maximum sea surface water temperature ( SST max ), deep meadows were less affected by sulphide intrusion than shallow ones. Thus, water depth acts as a protecting mechanism against sulphide intrusion. However, water depth would be insufficient to buffer seagrass sulphide stress triggered by Mediterranean seawater summer temperatures projected for the end of the 21st century even under scenarios of moderate greenhouse gas emissions, A1B. Mediterranean warming, therefore, is expected to enhance P. oceanica sulphide stress, and thus compromise the survival of this key habitat along its entire depth distribution range.
