No abstract

The Eastern Mediterranean and the Middle East (EMME) are likely to be greatly affected by climate change, associated with increases in the frequency and intensity of droughts and hot weather conditions. Since the region is diverse and extreme climate conditions already common, the impacts will be disproportional. We have analyzed long-term meteorological datasets along with regional climate model projections for the 21st century, based on the intermediate IPCC SRES scenario A1B. This suggests a continual, gradual and relatively strong warming of about 3.5–7°C between the 1961–1990 reference period and the period 2070–2099. Daytime maximum temperatures appear to increase most rapidly in the northern part of the region, i.e. the Balkan Peninsula and Turkey. Hot summer conditions that rarely occurred in the reference period may become the norm by the middle and the end of the 21st century. Projected precipitation changes are quite variable. Annual precipitation is expected to decrease in the southern Europe – Turkey region and the Levant, whereas in the Arabian Gulf area it may increase. In the former region rainfall is actually expected to increase in winter, while decreasing in spring and summer, with a substantial increase of the number of days without rainfall. Anticipated regional impacts of climate change include heat stress, associated with poor air quality in the urban environment, and increasing scarcity of fresh water in the Levant.Electronic supplementary materialThe online version of this article (doi:10.1007/s10584-012-0418-4) contains supplementary material, which is available to authorized users.

We quantify the trophic positions of subtropical open-ocean zooplankton species using amino acid-specific (AA) stable nitrogen isotopic compositions. We model animal trophic position by computing trophic 15 N enrichment of glutamic acid relative to phenylalanine, and find that trophic position for primary copepod consumers (Oithona spp., Neocalanus robustior) and secondary copepod consumers (Pleuromamma xiphias and Euchaeta rimana) varied little over a 5-10-yr period in the North Pacific Subtropical Gyre (NPSG; mean 6 SD: 2.1 6 0.1 and 2.9 6 0.1, respectively). Comparison of AA 15 N enrichment patterns in different copepod species suggests that trophic 15 N enrichment is most consistent in glutamic acid, aspartic acid, and alanine, ''trophic'' AAs that are intimately involved in the citric acid cycle and energy production. We further test equations involving these trophic AAs and ''source'' AAs (which appear to retain the nitrogen isotopic composition of the food-web base), and find that such compound-specific models give results that are identical to those calculated using whole-animal (bulk) stable isotopic compositions. However the benefits of our AA-based approach (i.e., the relatively few samples needed for precise TP estimation, elimination of the need for concurrent prey isotopic analyses, and the ability to utilize formalin-preserved specimens from archived collections), make this a powerful technique for the quantitative assessment of trophic position within the pelagic food web. We further discuss how stable isotopic analyses provide a new perspective on the structure of open-ocean food webs and can be used to trace large seasonal fluctuations in nitrogen source in the NPSG.

We used amino acid (AA) compound-specific isotope analysis (d 15 N AA and d 13 C AA values) of midwater zooplankton and suspended particles to examine their dynamics in the mesopelagic zone. Suspended particle d 15 N AA values increased by up to 14% with depth, whereas particle trophic status (measured as trophic position, TP) remained constant at 1.6 6 0.07. Applying a Rayleigh distillation model to these results gave an observed kinetic isotope fractionation of 5.7 6 0.4%, similar to that previously measured for protein hydrolysis. AA-based degradation index values also decreased with depth on the particles, whereas a measure of heterotrophic resynthesis (SV) remained constant at 1.2 6 0.3. The main mechanism driving 15 N enrichment of suspended particles appears to be isotope fractionation associated with heterotrophic degradation, rather than a change in trophic status or N source with depth. In zooplankton the ''source'' AA phenylalanine (Phe) became 15 N enriched by up to 3.5% with depth, whereas zooplankton TP increased by up to 0.65 between the surface ocean and midwaters. Both changes in the d 15 N values of food resources at the base of the zooplankton food web and changes in zooplankton TP drive observed zooplankton 15 N enrichment with depth. Midwater zooplankton d 15 N Phe values were lower by 5-8% compared with suspended particles, indicating this organic matter pool is not a significant zooplankton food resource at depth. Instead, 62-88% of the N sustaining midwater zooplankton is surface derived, obtained through consumption of sinking particles, carnivory of vertical migrants, or direct feeding in surface waters at night.