Fish assemblages were studied in a hypersaline tropical estuary in Northeastern Brazil. A total of 104 species were collected by beach seine during the dry and rainy seasons of 2012. Two families, Atherinopsidae and Gerreidae, were numerically dominant in all zones of the estuary; juveniles of Atherinella brasiliensis, Eucinostomus argenteus, Lile piquitinga, Ulaema lefroyi, Lutjanus analis and Sphoeroides greeleyi contributed 77% of the total catch. The factors that best explained the fish abundance pattern were salinity and depth, which were related to spatial segregation. Species richness was lowest in the upper zone, an area with high salinity and shallow depth. The distinct roles of structurally different habitats (submerged macrophyte beds and mangrove prop‐roots) and the influence of physicochemical conditions in the middle zone of the estuary may influence taxonomic diversity. The middle zone of the estuary is the one most attractive to juveniles of reef species (Lutjanidae and Serranidae). The fish assemblages are clearly dominated by marine estuarine dependent species, highlighting the importance of the ecosystem as a nursery ground for marine species of the Brazilian coast. 相似文献
We determined 15N/14N ratios of total nitrogen in surface sediments and dated sediment cores to reconstruct the history of N-loading of the North Sea. The isotopic N composition in modern surface sediments is equivalent to and reflects the isotopic mixture of oceanic nitrate on the one hand (δ15N = 5‰) and the imprint of river-borne nitrogen input into the SE North Sea (δ15N up to 12‰ in estuaries of the SE North Sea) on the other hand. We compare the results with δ15N records from pre-industrial sediment intervals in cores from the Skagerrak and Kattegat areas, which both constitute significant depositional centres for N in the North Sea and the Baltic Sea/North Sea transition. As expected, isotopically enriched anthropogenic nitrogen was found in the two records from the Kattegat area, which is close to eutrophication sources on land. Enrichment of δ15N in cores from the Skagerrak – the largest sediment sink for nitrogen in the entire North Sea – was not significant and values were similar to those found in sediment layers representing pre-industrial conditions. We interpret this isotopic uniformity as an indication that most riverine reactive nitrogen with its characteristic isotopic signature is removed by denitrification in shallow shallow-water sediments before reaching the main sedimentary basin of the North Sea. 相似文献
Investments in adaptation are required to reduce vulnerability and strengthen the resilience of food systems to the impacts of climate change. For low-income nations, international financing plays a central role in supporting adaptation. In this article, we document and examine adaptation projects targeting food systems financed through funding bodies of the United Nations Framework Convention on Climate Change (UNFCCC). We find that between 2004 and 2015, 3% (n?=?96) of adaptation projects supported through the UNFCCC explicitly focused on the production, processing, distribution, preparation and/or consumption of food, with US$546 m mobilized through funding bodies directly and US$1.44bn through co-financing. Agriculture is the most common sector supported, with extreme weather events the primary climate change-related impact motivating nations to apply for adaptation financing. The majority of actions are documented to adapt the food production component of food systems, with limited focus within projects on the full range of food system vulnerability and the implications on food security.Key policy insights
Enhanced international adaptation financing targeting food systems is needed, and in particular financing to address limited adaptation readiness
Supported food system projects should include holistic assessments of the entire food system in order to prioritize sector and food system component issue areas for short- and long-term efficiency
To better analyse food system linkages and aid in the prioritization of adaptation activities, adaptation-directed funds should consider placing a higher emphasis on a cross-sectoral approach within projects
Linkages between official development assistance and adaptation-directed funds could help optimize financing for food systems and mainstream food system adaptation efforts
Intellectual property rights (IPRs) and the transfer of low carbon technologies to developing countries have been the focus of sustained disagreement between many developed and developing country Parties to the United Nations Framework Convention on Climate Change (UNFCCC). We argue that this disagreement stems from two conflicting political discourses of economic development and low carbon technology diffusion which tend to underpin developing and developed countries’ respective motivations for becoming party to the Convention. We illustrate the policy implications of these discourses by examining empirical evidence on IPRs and low carbon technology transfer and highlight how the two discourses are based on an incomplete understanding of the role of technological capacity in either economic development or technology diffusion. This has important implication for the success of post-2012 international climate agreements. 相似文献
Assessments of temporal variation in stable carbon and nitrogen ratios were used to examine seasonal trends of the water column and benthic food webs in the Mondego estuary (Portugal). There was a marked seasonality in weather and water column conditions, including nutrient supply and chlorophyll concentrations. In spite of the pronounced environmental changes, we found little evidence of seasonal variation in δ13C and δ15N of producers and consumers in the Mondego estuary, with a few notable exceptions. Nitrogen isotope ratios in macrophytes (Zostera noltii, Ulva sp., Enteromorpha sp., and Gracilaria sp.), and in two grazers (Idotea chelipes and Lekanesphaera levii) increased during late summer, with the highest δ15N values being measured in July, during a period of elevated temperatures and drought, which may have favored high rates of denitrification and heavier δ15N values. The results suggest that stable-isotope values from macrophytes and selected grazers are useful as tracers of seasonal changes in nitrogen inputs into estuaries, and that those of consumers reflect other factors beyond seasonal variations in N and C sources. 相似文献
Calorimetric and P–V–T data for the high-pressure phase Mg5Al5Si6O21(OH)7 (Mg-sursassite) have been obtained. The enthalpy of drop solution of three different samples was measured by high-temperature
oxide melt calorimetry in two laboratories (UC Davis, California, and Ruhr University Bochum, Germany) using lead borate (2PbO·B2O3) at T=700 ∘C as solvent. The resulting values were used to calculate the enthalpy of formation from different thermodynamic datasets;
they range from −221.1 to −259.4 kJ mol−1 (formation from the oxides) respectively −13892.2 to −13927.9 kJ mol−1 (formation from the elements). The heat capacity of Mg5Al5Si6O21(OH)7 has been measured from T=50 ∘C to T=500 ∘C by differential scanning calorimetry in step-scanning mode. A Berman and Brown (1985)-type four-term equation represents
the heat capacity over the entire temperature range to within the experimental uncertainty: CP (Mg-sursassite) =(1571.104 −10560.89×T−0.5−26217890.0 ×T−2+1798861000.0×T−3) J K−1 mol−1 (T in K). The PVT behaviour of Mg-sursassite has been determined under high pressures and high temperatures up to 8 GPa and 800 ∘C using a MAX 80 cubic anvil high-pressure apparatus. The samples were mixed with Vaseline to ensure hydrostatic pressure-transmitting
conditions, NaCl served as an internal standard for pressure calibration. By fitting a Birch-Murnaghan EOS to the data, the
bulk modulus was determined as 116.0±1.3 GPa, (K′=4), VT,0=446.49 3 exp[∫(0.33±0.05) × 10−4 + (0.65±0.85)×10−8T dT], (KT/T)P = −0.011± 0.004 GPa K−1. The thermodynamic data obtained for Mg-sursassite are consistent with phase equilibrium data reported recently (Fockenberg
1998); the best agreement was obtained with ΔfH0298 (Mg-sursassite) = −13901.33 kJ mol−1, and S0298 (Mg-sursassite) = 614.61 J K−1 mol−1.
Received: 21 September 2000 / Accepted: 26 February 2001 相似文献
The high pressure spinel polymorph of Ni2SiO4 persists metastably at 713°C and atmospheric pressure. The enthalpy of the olivine-spinel transition was obtained by measuring the heats of solution of both polymorphs in a molten oxide solvent, 2PbO · B2O3, at that temperature. For Ni2SiO4(ol)→Ni2SiO4, ΔH9860 = +1.4 ± 0.7kcal/mol. The heat content increments, H986 ? H297, were found to be: olivine, 25.73 ± 0.42kcal/mol, and spinel, 25.39 ± 0.20kcal/mol. The measured enthalpy of the transformation is consistent with the low slope of the phase boundary, ?P/?T = ~ 12b/deg, observed by Akimoto and others. The entropy of the olivine-spinel transition in Ni2SiO4 is accordingly about a factor of three smaller in magnitude (ΔS = ~ ?1cal/deg mol) than that for Co2SiO4,Fe2SiO4,Mg2SiO4or Mg2GeO4 (ΔS = ?3to?3.5cal/deg mol). 相似文献
A calorimetric study of the ilmenite and lithium niobate polymorphs of FeTiO3 was undertaken to assess the high-pressure stabilities of these phases. Ilmenite is known to be the stable phase at ambient pressure, but the lithium niobate form may be a quench phase from a perovskite form which has been previously observed in situ at high pressure.In this study, the lithium niobate phase of FeTiO3 was synthesized from an ilmenite starting material at 15– 16 GPa and 1473 K, using a uniaxial split-sphere high-pressure apparatus (USSA 2000). The energetics of the ilmenite to lithium niobate transformation were investigated through transposed-temperature drop calorimetry. The heat of back-transformation of lithium niobate to ilmenite was measured by dropping the sample in argon from ambient conditions to a temperature where the transformation occurs spontaneously. In drops made at 977 K, an intermediate x-ray amorphous phase was encountered. At 1273 K, the transformation went to completion. A value of -13.5±1.2 kJ/mol was obtained for the heat of transformation. 相似文献