ALBERT

Description: Ambient UV radiation has substantially increased during the last decades, but its impact on marine benthic communities is hardly known. The aim of this study was to globally compare and quantify how shallow hard-bottom communities are affected by UV during early succession. Identical field experiments in 10 different coastal regions of both hemispheres produced a consistent but unexpected pattern: (i) UV radiation affected species diversity and community biomass in a very similar manner, (ii) diversity and biomass were reduced to a larger extent by UVA than UVB radiation, (iii) ambient UV levels did not affect the composition of the communities, and (iv) any UV effects disappeared during species succession after 2–3 months. Thus, current levels of UV radiation seem to have small, predictable, and transient effects on shallow marine hard-bottom communities.

Description: The quasi‐biennial oscillation (QBO) of the equatorial zonal wind leads to zonally symmetric temperature variations in the stratosphere that descend downward. Here we investigate the QBO‐induced temperature anomalies in the tropical tropopause layer (TTL) and detect pronounced longitudinal variations of the signal. In addition, the QBO temperature anomalies show a strong seasonal variability. The magnitude of these seasonal and longitudinal QBO variations is comparable to the magnitude of the well‐known zonal mean QBO signal in the TTL. At the cold point tropopause, the strongest QBO variations of around ±1.6 K are found over regions of active convection such as the West Pacific and Africa during boreal winter. The weakest QBO variations of ±0.25 K are detected over the East Pacific during boreal summer, while the zonal mean signal ranges around ±0.7 K. The longitudinal variations are associated with enhanced convective activity that occurs during QBO cold phases and locally enhances the cold anomalies.

Description: The zebra mussel Dreissena polymorpha is one of the most successful, notorious, and detrimental aquatic invasive non-native species worldwide, having invaded Europe and North America while causing substantial ecological and socio-economic impacts. Here, we investigated the spatiotemporal trends in this species' invasion success using 178 macroinvertebrate abundance time series, containing 1451 records of D. polymorpha collected across nine European countries between 1972–2019. Using these raw (absolute) abundance data, we examined trends and drivers of occurrences and relative abundances of D. polymorpha within invaded communities. Meta-regression models revealed non-significant trends both at the European level and for the majority of the invaded countries, except for France (significant decreasing trend) and Hungary (marginally positive trend). At the European level, the number of D. polymorpha occurrences over time followed a flat-top bell-shaped distribution, with a steep increase between 1973–1989 followed by a plateau phase prior to significantly declining post-1998. Using a series of climatic and hydromorphological site-specific characteristics of invaded and uninvaded sites from two periods (1998–2002; 2011–2015), we found that native richness, non-native abundance, distance to the next barrier, and elevation were associated with the occurrence of D. polymorpha. We also found that higher native richness and lower latitude were related to lower relative abundances. Using Cohen's D as a measure of D. polymorpha impact, we found that biodiversity within the invaded sites was initially higher than in uninvaded ones, but then declined, suggesting differences in biodiversity trends across invaded and uninvaded sites. While our results emphasise the high invasion success of D. polymorpha, increasing stressors within the context of global change – particularly ongoing climate change – are likely to enhance invasion rates and the impact of D. polymorpha in the near future, exacerbated by the lack of timely and effective management actions.