Phenotypic variation of larks along an aridity gradient:Are desert birds more flexible?

We investigated interindividual variation and intra-individual phenotypic flexibility in basal metabolic rate (BMR), total evaporative water loss (TEWL), body temperature (T-b), the minimum dry heat transfer coefficient (h), and organ and muscle size of five species of larks geographically distributed along an aridity gradient. We exposed all species to constant environments of 15degreesC or 35degreesC, and examined to what extent interspecific differences in physiology can be attributed to acclimation. We tested the hypothesis that birds from deserts display larger intra-individual phenotypic flexibility and smaller intern individual variation than species from mesic areas.Larks from arid areas had lower BMR, TEWL, and h, but did not have internal organ, sizes different from birds from mesic habitats. BMR of 15degreesC-acclimated birds was 18.0%, 29.1%, 12.2%, 25.3%, and 4.7% higher than of 35degreesC-acclimated Hoopoe Larks, Dunn's Larks, Spike-heeled Larks, Skylarks, and Woodlarks, respectively. TEWL of 15degreesC-acclimated Hoopoe Larks exceeded values for 35degreesC-acclimated individuals by 23% but did not differ between 15degreesC- and 35degreesC-acclimated individuals in the other species. The dry heat transfer coefficient was increased in 15degreesC-acclimated individuals of Skylarks and Dunn's Larks, but not in the. other species. Body temperature was on average 0.4degreesC +/- 0.15degreesC (mean +/- 1 SEM) lower in 15degreesC-acclimated individuals of all species. Increased food intake in 15degreesC-acclimated birds stimulated enlargement of intestine (26.9-38.6%), kidneys (9.8-24.4%), liver (16.5-27.2%), and. stomach (22.0-31.6%). The pectoral muscle increased in 15degreesC-acclimated Spike-heeled Larks and Skylarks, remained unchanged in Hoopoe Larks, and decreased in 15degreesC-acclimated Woodlarks and Dunn's Larks. We conclude that the degree of intra-individual flexibility varied between physiological traits and among species, but that acclimation does not account for interspecific differences in BMR, TEWL, and h in larks. We found no general support for the hypothesis that species from desert environments display larger intra-individual phenotypic flexibility than those from mesic areas.The coefficient of variation of larks acclimated to their natural environment was smaller in species from and areas than in species from mesic areas for mass-corrected BMR and surface-specific h, but not for mass-corrected TEWL. The high repeatabilities of BMR, TEWL, and h in several species indicated a within-individual consistency on which natural selection could operate.</p

Tracking seasonal changes in North Sea zooplankton trophic dynamics using stable isotopes

Trophodynamics of meso-zooplankton in the North Sea (NS) were assessed at a site in the southern NS, and at a shallow and a deep site in the central NS. Offshore and neritic species from different ecological niches, including Calanus spp., Temora spp. and Sagitta spp., were collected during seven cruises over 14 months from 2007 to 2008. Bulk stable isotope (SI) analysis, phospholipid-derived fatty acid (PLFA) compositions, and δ 13CPLFA data of meso-zooplankton and particulate organic matter (POM) were used to describe changes in zooplankton relative trophic positions (RTPs) and trophodynamics. The aim of the study was to test the hypothesis that the RTPs of zooplankton in the North Sea vary spatially and seasonally, in response to hydrographic variability, with the microbial food web playing an important role at times. Zooplankton RTPs tended to be higher during winter and lower during the phytoplankton bloom in spring. RTPs were highest for predators such as Sagitta sp. and Calanus helgolandicus and lowest for small copepods such as Pseudocalanus elongatus and zoea larvae (Brachyura). δ 15NPOM-based RTPs were only moderate surrogates for animals’ ecological niches, because of the plasticity in source materials from the herbivorous and the microbial loop food web. Common (16:0) and essential (eicosapentaenoic acid, EPA and docosahexaenoic acid, DHA) structural lipids showed relatively constant abundances. This could be explained by incorporation of PLFAs with δ 13C signatures which followed seasonal changes in bulk δ 13CPOM and PLFA δ 13CPOM signatures. This study highlighted the complementarity of three biogeochemical approaches for trophodynamic studies and substantiated conceptual views of size-based food web analysis, in which small individuals of large species may be functionally equivalent to large individuals of small species. Seasonal and spatial variability was also important in altering the relative importance of the herbivorous and microbial food webs

Impacts of 1.5°C Global Warming on Natural and Human Systems

An IPCC Special Report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate povert

IPCC, 2023: Climate Change 2023: Synthesis Report, Summary for Policymakers. Contribution of Working Groups I, II and III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, H. Lee and J. Romero (eds.)]. IPCC, Geneva, Switzerland.

This Synthesis Report (SYR) of the IPCC Sixth Assessment Report (AR6) summarises the state of knowledge of climate change, its widespread impacts and risks, and climate change mitigation and adaptation. It integrates the main findings of the Sixth Assessment Report (AR6) based on contributions from the three Working Groups1 , and the three Special Reports. The summary for Policymakers (SPM) is structured in three parts: SPM.A Current Status and Trends, SPM.B Future Climate Change, Risks, and Long-Term Responses, and SPM.C Responses in the Near Term.This report recognizes the interdependence of climate, ecosystems and biodiversity, and human societies; the value of diverse forms of knowledge; and the close linkages between climate change adaptation, mitigation, ecosystem health, human well-being and sustainable development, and reflects the increasing diversity of actors involved in climate action. Based on scientific understanding, key findings can be formulated as statements of fact or associated with an assessed level of confidence using the IPCC calibrated language

Differential routing of 'new' nitrogen toward higher trophic levels within the marine food web of the Gulf of Aqaba, Northern Red Sea

Mesozooplankton communities in the mesooligotrophic Gulf of Aqaba, Northern Red Sea, were investigated over a 2 years period (2005-2007) with emphasis on the trophodynamic relations among different taxonomic groups ranging from primary consumers to carnivorous predators. Based on stable isotope analyses, we present evidence for a strong contribution of 'new' nitrogen mainly derived from the utilization of aerosol nitrate by unicellular cyanobacteria especially during summer stratification and the propagation of exceptionally low δ15N onto higher trophic levels. In contrast, N2-fixation by diazotrophs seemed to play a minor role, while the utilization of deep water nitrate by cyanobacteria and eukaryotic algae might be of importance during winter mixing. Based on 15N enrichment of consumers, clear differences between exclusively herbivorous organisms (doliolids, appendicularians, pteropods) and those with omnivorous feeding modes were detected. The category of omnivores comprised a large variety of taxons ranging from small meroplanktonic larvae to non-calanoid copepods (harpacticoids, cyclopoids and poecilostomatoids) that together form a diverse and complex community with overlapping feeding modes. In addition, distinct seasonality patterns in δ15N of copepods were found showing elevated trophic positions during periods of winter mixing, which were most pronounced for non-calanoid copepods. In general, feeding modes of omnivores appeared rather unselective, and relative contributions of heterotrophic protists and degraded material to the diets of non-calanoid copepods are discussed. At elevated trophic positions, four groups of carnivore predators were identified, while calanoid copepods and meroplanktonic predators showing lowest 15N enrichment within the carnivores. The direct link between 'new' nitrogen utilization by primary producers and the 15N enrichment of consumers in the planktonic food web of the Gulf of Aqaba emphasizes the significant contribution of 'new' nitrogen to the nitrogen budget and ecosystem functions in subtropical and tropical oligotrophic oceans