UV-B exposure, ROS, and stress: inseparable companions or loosely linked associates?

Ultraviolet-B (UV-B) radiation has long been perceived as a stressor. However, a conceptual U-turn has taken place, and UV-B damage is now considered rare. We question whether UV-stress and UV-B-induced reactive oxygen species (ROS) are still relevant concepts, and if ROS-mediated signaling contributes to UV-B acclimation. Measurements of antioxidants and of antioxidant genes show that both low and high UV-B doses alter ROS metabolism. Yet, there is no evidence that ROS control gene expression under low UV-B. Instead, expression of antioxidant genes is linked to the UV RESISTANCE LOCUS 8 pathway. We hypothesize that low UVB doses cause ‘eustress’ (good stress) and that stimulispecific signaling pathways pre-dispose plants to a state of low alert that includes activation of antioxidant defenses.Funding agencies are:COST Action  FA0906UV4Growth  Faculty of Business, Science, and Technology at Örebro University  Science Foundation Ireland (SFI)  11/RFP.1/EOB/3303 Hungarian Scientific Research Fund  OTKA NN-85349 UV-B-fotobiologi: mekanismer för perception och cellulära response

Zoochorous dispersal of freshwater bivalves: an overlooked vector in biological invasions?

Vectors that underpin the natural dispersal of invasive alien species are frequently unknown. In particular, the passive dispersal (zoochory) of one organism (or propagule) by another, usually more mobile animal, remains poorly understood. Field observations of the adherence of invasive freshwater bivalves to other organisms have prompted us to assess the importance of zoochory in the spread of three prolific invaders: zebra mussel Dreissena polymorpha; quagga mussel Dreissena bugensis; and Asian clam Corbicula fluminea. An extensive, systematic search of the literature was conducted across multiple on-line scientific databases using various search terms and associated synonyms. In total, only five publications fully satisfied the search criteria. It appears that some fish species can internally transport viable adult D. polymorpha and C. fluminea specimens. Additionally, literature indicates that veligers and juvenile D. polymorpha can adhere to the external surfaces of waterbirds. Overall, literature suggests that zoochorous dispersal of invasive bivalves is possible, but likely a rare occurrence. However, even the establishment of a few individuals (or a single self-fertilising C. fluminea specimen) can, over-time, result in a substantial population. Here, we highlight knowledge gaps, identify realistic opportunities for data collection, and suggest management protocols to mitigate the spread of invasive alien species

Spatial patterns of natural regeneration in stands of English yew (Taxus baccata L.); Negative neighbourhood effects

Understanding the mechanisms underlying spatial patterns of regeneration of tree species can improve the effectiveness of forest management and restoration activities. English yew (Taxus baccata L.) stands have declined across their native range and yew dominated woodlands have priority status under the EU Habitats Directive. Several conservation and restoration programmes for this species have been established. We investigated population structure and spatial distribution of natural regeneration of yew at six woodlands in the south and west of Ireland. Specifically, the influence of adult conspecific neighbourhood density, canopy cover and distance from seed source on regeneration was explored. Within each site, canopy openness, soil and vegetation characteristics were established. Weiner spatial analysis revealed that the density of conspecific adults was negatively related to the recruitment of yew juveniles. In addition, a significant negative relationship between presence of conspecific canopy cover and regeneration density was evident. Although seedlings and saplings were scarce directly beneath conspecifics, regeneration was highest in nearby areas suggesting that intermediate dispersal distance maximises recruitment probability. Yew regeneration was correlated with a number of habitat characteristics, particularly percentage cover of woody shrubs. Management operations should focus on regeneration around the edges of populations to conserve existing yew stand

Environmental plastics in the context of UV radiation, climate change, and the Montreal Protocol

There are close links between solar UV radiation, climate change, and plastic pollution. UV-driven weathering is a key process leading to the degradation of plastics in the environment but also the formation of potentially harmful plastic fragments such as micro- and nanoplastic particles. Estimates of the environmental persistence of plastic pollution, and the formation of fragments, will need to take in account plastic dispersal around the globe, as well as projected UV radiation levels and climate change factors. UV radiation, climate change, and plastic pollution are closely interlinked. Existing studies on the persistence of plastics do not fully consider these linkages, challenging global assessments of plastic dispersal, persistence, and weathering. Recently, an Intergovernmental Negotiating Committee was tasked with developing an international binding agreement to end plastic pollution. In response, the UNEP Environmental Effects Assessment Panel assessed effects of UV radiation and interacting climate change factors on plastics, focusing on the durability of products as well as the production and dispersal of micro- and nano-plastic pollutants in the environment

Frond development gradients are a determinant of the impact of zinc on photosynthesis in three species of Lemnaceae

Chlorophyll-a fluorescence is an effective tool for measuring photosynthesis. Photosynthesis is particularly sensitive to the presence of zinc or other metals. Plant age and developmental stage strongly influence the effects of metals on the photosynthetic apparatus. However, there is little information on how this may affect toxicological assessment in plants. In this study, three Lemnaceae species were exposed to a range of zinc concentration in static, batch exposures for seven days, as detailed for Lemnaceae toxicity testing in OECD guidelines. Effects of zinc on photosynthetic performance in the three species were measured over the seven days. The maximum quantum efficiency of photosystem II, Fv/Fm, the effective quantum efficiency, Y(II), and photochemical quenching, qP, were measured in mature and young fronds, as well as along a developmental gradient within fronds. Fv/Fm and Y(II) in young, emerging Landoltia punctata fronds were more severely impacted by zinc than in developed, mature fronds. Furthermore, younger proximal sections of L. punctata fronds were more impacted than older distal frond sections. Overall, Fv/Fm and Y(II) also tended to be more affected by zinc in young, compared to mature, Lemna gibba and Lemna minor fronds. Single colony, time-point or leaf-zone analyses may not, therefore, show the full biological picture of the impact of a toxicant, while species-specific differences need also to be considered. Therefore, selection of Lemnaceae species and developmental stages of fronds should be given careful consideration when using chlorophyll-a fluorometry for assessing chemical toxicity in Lemnaceae

Differential decomposition patterns of marine and terrestrial biomass in a coastal lagoon

Abstract. Lagoons are ecosystems where freshwater and marine organisms converge together with lagoonal specialists to form a mixed community that may vary spatially along a salinity gradient. Many organisms can only survive within relatively narrow bands of salinity. As a result of marine and freshwater inflows, together with exposure to variable salinity levels, dead marine and terrestrial biomass is accumulated in lagoons where it enters the detritic pathway. This study examined the in situ decomposition of marine (Fucus vesiculosus) and terrestrial (Alder glutinosa) biomass in Cuskinny Lagoon, South West Ireland. F. vesiculosus decayed rapidly and uniformly across the lagoon. A. glutinosa biomass loss varied throughout the lagoon, with the greatest loss occurring near the freshwater inflow. Thus, the spatial pattern of A. glutinosa decomposition differs from that of F. vesiculosus decomposition. Invertebrate abundances were not related to the amount of biomass loss of the marine and terrestrial material. This study demonstrates the differential decomposition patterns of marine and terrestrial biomass in the dynamic environment of a coastal lagoon. Abbreviations: ppt (parts per thousand); AFDW (ash free dry weight