Little is known about how old-growth and massive forests are responding to environmental change. We investigated tree-ring growth and carbon isotopes of the long-lived and high biomass Fitzroya cupressoides in two stands growing in contrasting environmental conditions in the Coastal Range (~300 years old) and Andean Cordilleras (>1500 years old) of southern Chile. The interannual variability in δ 13 C was assessed for the period 1800-2010, and changes in discrimination and intrinsic water use efficiency (iWUE) were evaluated in relation to changes in climate and tree-ring growth during the last century. 13 C discrimination has significantly decreased, and iWUE has increased since the 1900s in both sites. However, these trends in isotopic composition have been accompanied by different growth patterns: decreasing growth rates in the Coastal Range since the 1970s and increasing growth rates in the Andes since the 1900s. Trees growing in the Coastal Range have become more efficient in their use of water, probably due to reduced stomatal conductance caused by increases in CO 2 and warming. Trees growing in the Andes have also become more water use efficient, but this has been likely due to increased photosynthetic rates. Fitzroya forests, including particularly old-growth stands, are responding to recent environmental changes, and their response has been site dependent. The growth of forests under a more Mediterranean climate influence and restrictive soil conditions in the Coastal Range has been more negatively affected by current warming and drying; while the growth of old stands in the wet Andes has been positively affected by changes in climate (decreasing cloudiness) and increasing CO 2 . Permanent monitoring of these endangered forests under ongoing environmental changes is needed in order to reassure the long-term preservation of this millennial-aged species.The assessment of forest growth responses to environmental changes from seasonal to centennial timescales can be performed using tree rings. Dendrochronological studies in different species have reported divergent growth trends in recent decades, ranging from increases attributed to warming and CO 2 fertilization URRUTIA-JALABERT ET AL.

Sedimentary features, mineralogy, bulk geochemical composition, stable isotope analyses and pollen data from sediment cores were used to reconstruct the Late Quaternary depositional evolution of the Salada Mediana playa lake (central Ebro Basin, northeastern Spain). The 150‐cm‐long sediment core sequence is composed of gypsum‐ and dolomite‐rich muds (Lower and Middle sections) and black, laminated, calcite‐bearing sediments (Upper section). The Salada Mediana formed as a karstic depression in the Miocene gypsum substratum during the Late Pleistocene. The Lower section was deposited in a sulphate–carbonate saline lake that ended with a period of desiccation and basin floor deflation. Subsequent deposition (Middle section) took place in a playa‐lake system. Two cycles of lower water table and expanded saline mud flats occurred. The Holocene sequence is missing, probably as a result of aeolian erosion. Sedimentation resumed only a few centuries ago, and saline pan environments dominated until modern times. The Salada Mediana facies succession was mainly governed by fluctuations in the hydrological balance, brine composition, and salinity; however, aeolian processes (detrital input and deflation) and recycling of previously precipitated salts also played a significant role.

Coastal vegetated ecosystems are intense global carbon (C) sinks; however, seagrasses and mangroves in the Central Red Sea are depleted in organic C (C org ). Here, we tested whether C org depletion prevails along the Red Sea, or if sediment C org and nitrogen (N) stocks reflect the latitudinal productivity gradient of the Red Sea. We assessed C org and N concentrations, stocks, isotopic compositions (δ 13 C and δ 15 N), and the potential contribution of primary producers to the organic matter accumulation in seagrass and mangrove sediments along the Eastern coast of the Red Sea. Sediment C org concentration was higher in mangroves than seagrasses, while N concentrations were similar, resulting in higher C/N ratios in mangrove than seagrass sediments. Mangrove C org stocks (integrated over the top 10 cm) were twofold higher than those of seagrasses. N concentrations and stocks decreased from south to north in seagrass sediments matching the productivity gradient while C org concentrations and stocks were uniform. The δ 15 N decreased from south to north in seagrass and mangrove sediments, reflecting a shift from nitrate and nitrite as N sources in the south, to N 2 fixation toward the north. Stable isotope mixing models showed that seagrass leaves and macroalgae blades were the major contributors to the organic matter accumulation in seagrass sediments; while mangrove leaves were the major contributors in mangrove sediments. Overall, vegetated sediments in the Red Sea tend to be carbonate-rich and depleted in C org and N, compared to coastal habitats elsewhere. Specifically, mean C org stocks in Red Sea seagrass and mangrove sediments (7.2 ± 0.4 and 14.5 ± 1.4 Mg C ha −1 , respectively) are lower than previously reported mean global values. This new information of Blue Carbon resources in the Red Sea provides a background for Blue Carbon programs in the region while also helping to balance global estimates.

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Changes in feeding habits during ontogeny show that organisms can present shifts in foraging behavior during their life cycle, which can alter local trophic dynamics. Therefore, describing diet across species ontogeny clarifies the ecological niche and ecosystem role of marine predators. In this study, diet tracers (stable isotope analysis) were analyzed in 16 scalloped hammerhead sharks Sphyrna lewini, using δ13C and δ15N values of collagen in vertebral cross-sections to reconstruct diet across their ontogeny. Our results suggest that S. lewini occupies a broad isotopic niche due to the consumption of prey belonging to different trophic levels (δ15N: 7.6-13.0‰) of the food chain in both coastal and oceanic zones (δ13C: -17.2 to -14.1‰) during their lifetime. Accordingly, ontogenetic changes in diet and habitat use were suggested by differences in δ13C and δ15N across age groups, indicating high consumption of coastal prey at 0-2 yr, oceanic prey at ~2-4 yr, a shift to high coastal prey at >4 yr, and a shift to high coastal prey, along with the consumption of prey from multiple trophic levels through feeding ontogeny (estimated trophic position: 2.9-6.5). This study showed migration from coastal to oceanic zones in juvenile S. lewini, and their return to coastal habitats as adults, potentially related to the use of coastal zones (i.e. mangroves) in the Eastern Tropical Pacific, both as important feeding areas for neonates and as feeding and breeding grounds for adults.