气候变化领域集成服务门户

In the Arctic, especially in the coastal mountainous areas, gradual changes in elevation above sea level and allochthonous nutrients delivered by seabirds modify environmental conditions. Increasing elevation affects temperature whereas allochthonous nutrients delivered by seabirds to the terrestrial ecosystem remarkably influence primary production and diversity of organisms. Knowing the abundance of ubiquitous tardigrades (a microinvertebrate phylum), their multitrophic level function and their trophic composition might be essential for understanding ecosystem functioning and matter flow in fragile polar ecosystems. In this study, we tested the effects of altitude and seabird guano on modifying trophic diversity of tardigrades. We found that the tardigrades in Hornsund were herbivorous and microbivorous species dominated. Microbivores were significantly more abundant in guano-supplied than in control areas, which may be explained by the presence of higher nutrient and organic matter content in comparison with areas not fertilised by birds. We observed no significant relationship between the abundance of tardigrade trophic groups and altitude. However, the abundance of xerictolerant herbivorous terrestrial tardigrades representing the class Heterotardigrada increased with altitude. Strongly hygrophilic conditions (ponds, swamps, streams) at lower elevations as well as acidic conditions formed by seabird guano may reduce the abundance of heterotardigrades. Our study shows that seabirds rather than the effect of altitude or the generally predicted increasing temperatures in the Arctic, are affecting high Arctic tundra limno-terrestrial invertebrate trophic groups proportion. Our results provide baseline data for future studies of the Hornsund region, since climate change scenarios predict decreased guano delivery by seabirds on mountain slopes, shifts in plant species dominance and more intense fertilisation of lakes by geese, all of which may alter invertebrate trophic composition in southern Svalbard.