The Environmental Effects Assessment Panel (EEAP) is one of three Panels of experts that inform the Parties to the Montreal Protocol. The EEAP focuses on the effects of UV radiation on human health, terrestrial and aquatic ecosystems, air quality, and materials, as well as on the interactive effects of UV radiation and global climate change. When considering the effects of climate change, it has become clear that processes resulting in changes in stratospheric ozone are more complex than previously held. Because of the Montreal Protocol, there are now indications of the beginnings of a recovery of stratospheric ozone, although the time required to reach levels like those before the 1960s is still uncertain, particularly as the effects of stratospheric ozone on climate change and vice versa, are not yet fully understood. Some regions will likely receive enhanced levels of UV radiation, while other areas will likely experience a reduction in UV radiation as ozone- and climate-driven changes affect the amounts of UV radiation reaching the Earth's surface. Like the other Panels, the EEAP produces detailed Quadrennial Reports every four years; the most recent was published as a series of seven papers in 2015 (Photochem. Photobiol. Sci., 2015, 14, 1-184). In the years in between, the EEAP produces less detailed and shorter Update Reports of recent and relevant scientific findings. The most recent of these was for 2016 (Photochem. Photobiol. Sci., 2017, 16, 107-145). The present 2017 Update Report assesses some of the highlights and new insights about the interactive nature of the direct and indirect effects of UV radiation, atmospheric processes, and climate change. A full 2018 Quadrennial Assessment, will be made available in 2018/2019.

Ultraviolet-B (UV-B) radiation can have a negative impact on the growth and development of plants. Plants tolerant to UV-B alleviate these effects using UV-screening pigments that reduce the penetration of UV-B into mesophyll tissue. Little is known about the relative contribution of specific phenolic compounds to the screening capacity of leaves. The D1 and D2 proteins constituting the photosystem (PS) II reaction center heterodimer are targets of UV-B radiation and can be used as an in situ sensor for UV penetration into photosynthetic tissue. Degradation of these proteins occurs under very low fluences of UV-B, and is strongly accelerated in the presence of visible light. Using the D1-D2 degradation assay, we characterized UV-B sensitivity of Arabidopsis mutants (tt4, tt5, and fah1) that are genetically altered in their composition of phenolic compounds. We found that changes in phenol metabolism result in altered rates of PSII reaction center heterodimer degradation under mixtures of photosynthetically active radiation and UV-B. A comparison of D2 degradation kinetics showed increased UV sensitivity of the Landsberg (Landsberg erecta) tt5 mutant relative to the Landsberg tt4 mutant and the Landsberg wild type. Despite a lack of flavonoid accumulation, the tt4 mutant is not particularly UV sensitive. However, the tolerance of this mutant to UV-B may reflect the increased accumulation of sinapate esters that strongly absorb in the UV range, and may thus protect the plant against environmentally relevant UV-B radiation. This sinapate-mediated protection is less obvious for the tt4 mutant of Columbia ecotype, indicating that the relative contribution of particular phenolics to the total screening capacity varies with the genetic background. The role of sinapate esters in UV screening is further substantiated by the results with the fah1 mutant where absence of most of the sinapate esters results in a significantly accelerated degradation of D2 under mixed light conditions. Because the latter mutant is not expected to be deficient in flavonoids, the relative contribution of flavonoids as protectants of PSII reaction center heterodimer against UV-B damage in Arabidopsis needs to be re-evaluated vis-a-vis screening by simple phenolics like sinapate esters.

SummaryThe photosystem II reaction centre has at its core a heterodimer made up of two proteins, D1 and D2. The D1 protein is known to be rapidly degraded by photosynthetically active radiation while the D2 protein is relatively stable. This paper reports that when the aquatic higher plant, Spirodele was exposed to ultraviolet-B radiation, D2 degradation accelerated markedly and half life times approached those of the D1 protein. Moreover, in the presence of an environmentally relevant background of photosynthetically active radiation, low fluxes of ultraviolet-B (but not ultraviolet-A) radiation synergistically stimulated degradation of the D2 protein within functional reaction cantres. Thus, above a critical threshold, uitraviolet-B specifically targets the D1-D2 heterodimer for accelerated degradation.

Microplastics have become ubiquitous in all environments. Yet, their environmental fate is still largely unknown. Plastic fragmentation is a key component of plastic degradation, which is mostly caused by abiotic processes over prolonged time scales. Here, it is shown that the freshwater amphipod Gammarus duebeni can rapidly fragment polyethylene microplastics, resulting in the formation of differently shaped and sized plastic fragments, including nanoplastics. Fragments comprised 65.7% of all observed microplastic particles accumulated in digestive tracts. Higher numbers of fragments were found in response to longer exposure times and/or higher microplastic concentrations. Furthermore, the proportion of smaller plastic fragments was highest when food was present during the depuration process. It is concluded that G. duebeni can rapidly fragment polyethylene microplastics and that this is closely associated with the feeding process. These results highlight the crucial role, currently understudied, that biota may play in determining the fate of microplastics in aquatic ecosystems.