Ecosystem Responses to Climate-Related Changes in a Mediterranean Alpine Environment Over the Last ~ 180 Years

Seronegativity of Iberian ibex (Capra pyrenaica) against Toxoplasma gondii and Neospora caninum is consistent with eco-epidemiological and environmental features in Mediterranean mountainous areas

Knowledge of pathogen epidemiological dynamics and habitat ecological features is essential for wildlife population and health monitoring and management. Toxoplasma gondii and Neospora caninum are two broadly distributed multi-host parasites that affect both wild and domestic animals and, in the case of T. gondii, cause zoonosis. This study reports the seroprevalence of both parasites in Iberian ibex (Capra pyrenaica), a mountain wild ruminant native to the Iberian Peninsula, from the Natural Space of Sierra Nevada (NSSN) in southeastern Spain. Serum from 146 Iberian ibexes were analysed using two in-house ELISA techniques. The positive and doubtful sera were further checked by Western Blot (WB). Seventeen ibexes (11.6 %; 95 % confidence interval 6.4-16.7) were positive for T. gondii and seven (4.8 %; 95 % confidence interval 1.3-8.2) for N. caninum. However, no sera were positive to T. gondii nor to N. caninum by WB. Using at least two different serological techniques is recommended when they are not validated for the target host species. The NSSN is a hypoendemic area for T. gondii and N. caninum, probably determined by the reduced abundance and restricted distribution of their definitive hosts. This would explain the hypoendemic situation in the NSSN and the lack of specific antibodies against these two parasites in the Iberian ibex population. This eco-epidemiological scenario can be challenged by climate and anthropogenic changes, recommending long-term monitoring Iberian ibex population and health, both as a conservation measure for the species and as an indicator of the potential impact of global change on high mountain ecosystems.

Ecosystem shift of a mountain lake under climate and human pressure: A move out from the safe operating space

A multiproxy approach including chironomid, diatom, pollen and geochemical analyses was applied on short gravitational cores retrieved from an alpine lake (Lacul Bâlea) in the Southern Carpathians (Romania) to unveil how this lake responded to natural and anthropogenic forcing over the past 500 years. On the basis of chironomid and diatom assemblage changes, and supported by sediment chemical data and historical information, we distinguished two main phases in lake evolution. Before 1926 the lake was dominated by chironomids belonging to Micropsectra insignilobus-type and benthic diatoms suggesting well-oxygenated oligotrophic environment with only small-scale disturbance. We considered this state as the lake's safe operational space. After 1926 significant changes occurred: Tanytarsus lugens-type and T. mendax-type chironomids took over dominance and collector filterers increased until 1970 pointing to an increase in available nutrients. The diatom community showed the most pronounced change between 1950 and 1992 when planktonic diatoms increased. The highest trophic level was reconstructed between 1970 and 1992, while the indicator species of increasing nutrient availability, Asterionella formosa spread from 1982 and decreased rapidly at 1992. Statistical analyses evidenced that the main driver of the diatom community change was atmospheric reactive nitrogen (Nr) fertilization that drastically moved the community towards planktonic diatom dominance from 1950. The transformation of the chironomid community was primarily driven by summer mean temperature increase that also changed the dominant feeding guild from collector gatherers to collector filterers. Our results overall suggest that the speed of ecosystem reorganisation showed an unprecedented increase over the last 100 years; biological systems in many cases underwent threshold type changes, while several system components displayed non-hysteretic change between alternating community composition. We conclude that Lake Bâlea is outside of its safe operating space today. The main trigger of changes since 1926 was climate change and human impact acting synergically.

Long-term ecological changes in Mediterranean mountain lakes linked to recent climate change and Saharan dust deposition revealed by diatom analyses

Anthropogenic climate change and the recent increase of Saharan dust deposition has had substantial effects on Mediterranean alpine regions. We examined changes in diatom assemblage composition over the past ~180 years from high-resolution, dated sediment cores retrieved from six remote lakes in the Sierra Nevada Mountains of Southern Spain. In all lakes, changes in diatom composition began over a century ago, but were more pronounced after ~1970 CE, concurrent with trends in rising regional air temperature, declining precipitation, and increased Saharan dust deposition. Temperature was identified as the main predictor of diatom assemblage changes, whereas both Saharan dust deposition drivers, the Sahel precipitation index and the winter North Atlantic Oscillation, were secondary explanatory variables. Diatom compositional shifts are indicative of lake alkalinization (linked to heightened evapoconcentration and an increase in calcium-rich Saharan dust input) and reduced lake water turbulence (linked to lower water levels and reduced inflows to the lakes). Moreover, decreases in epiphytic diatom species were indicative of increasing aridity and the drying of catchment meadows. Our results support the conclusions of previous chlorophyll-a and cladoceran-based paleolimnological analyses of these same dated sedimentary records which show a regional-scale response to climate change and Saharan dust deposition in Sierra Nevada lakes and their catchments during the 20th century. However, diatom assemblages seem to respond to different atmospheric and climate-related effects than cladoceran assemblages and chlorophyll-a concentrations. The recent impact of climate change and atmospheric Saharan deposition on lake biota assemblages and water chemistry, as well as catchment water availability, will have important implications for the valuable ecosystem services that the Sierra Nevada provides.