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Optical phenomena in dielectric spheres several light wavelengths in size: a review
Get PDFThe size parameter q = 2πR/λ in spheres with a radius R = (2–3)λ (λ is the radiation wavelength) is on the order of 10. Strong Mie resonances (l>5 ) are observed in these structures; these resonances lead to peculiar optical phenomena, caused by the interference of high-order multipoles and localization of magnetic fields. Examples of such optical phenomena are presented in this review
The accumulation of microplastic pollution in a commercially important fishing ground
Get PDFThe Irish Sea is an important area for Norway Lobster Nephrops norvegicus fisheries, which are the most valuable fishing resource in the UK. Norway lobster are known to ingest microplastic pollution present in the sediment and have displayed reduced body mass when exposed to microplastic pollution. Here, we identified microplastic pollution in the Irish Sea fishing grounds through analysis of 24 sediment samples from four sites of differing proximity to the Western Irish Sea Gyre in both 2016 and 2019. We used µFTIR spectroscopy to identify seven polymer types, and a total of 77 microplastics consisting of fibres and fragments. The mean microplastics per gram of sediment ranged from 0.13 to 0.49 and 0 to 1.17 MP/g in 2016 and 2019, respectively. There were no differences in the microplastic counts across years, and there was no correlation of microplastic counts with proximity to the Western Irish Sea Gyre. Considering the consistently high microplastic abundance found in the Irish Sea, and the propensity of N. norvegicus to ingest and be negatively impacted by them, we suggest microplastic pollution levels in the Irish Sea may have adverse impacts on N. norvegicus and negative implications for fishery sustainability in the future
European Lobster Larval Development and Fitness Under a Temperature Gradient and Ocean Acidification
Get PDFClimate change combined with anthropogenic stressors (e.g. overfishing, habitat destruction) may have particularly strong effects on threatened populations of coastal invertebrates. The collapse of the population of European lobster ( Homarus gammarus) around Helgoland constitutes a good example and prompted a large-scale restocking program. The question arises if recruitment of remaining natural individuals and program-released specimens could be stunted by ongoing climate change. We examined the joint effect of ocean warming and acidification on survival, development, morphology, energy metabolism and enzymatic antioxidant activity of the larval stages of the European lobster. Larvae from four independent hatches were reared from stage I to III under a gradient of 10 seawater temperatures (13-24°C) combined with moderate (∼470 µatm) and elevated (∼1160 µatm) seawater pCO 2 treatments. Those treatments correspond to the shared socio-economic pathways (SSP), SSP1-2.6 and SSP5-8.5 (i.e. the low and the very high greenhouse gas emissions respectively) projected for 2100 by the Intergovernmental Panel on Climate Change. Larvae under the elevated pCO 2 treatment had not only lower survival rates, but also significantly smaller rostrum length. However, temperature was the main driver of energy demands with increased oxygen consumption rates and elemental C:N ratio towards warmer temperatures, with a reducing effect on development time. Using this large temperature gradient, we provide a more precise insight on the aerobic thermal window trade-offs of lobster larvae and whether exposure to the worst hypercapnia scenario may narrow it. This may have repercussions on the recruitment of the remaining natural and program-released specimens and thus, in the enhancement success of future lobster stocks. </p
Spatial and Temporal variation of size at maturity in an intensive crustacean fishery with limited management
Get PDFThe edible crab Cancer pagurus supports a valuable northeast Atlantic fishery, but concerns have been raised about declining catches and its management relies heavily on minimum landing sizes (MLSs). Furthermore, few data are available on spatial and particularly temporal variation in maturity of this and other crab species. Here we estimated size at maturity for C. pagurus in the Irish and Celtic Seas (north and south Wales, UK, respectively, around 200 km apart) caught during 2020–2021 and compared these to the Wales-wide MLS of 140 mm carapace width (CW) and results of a similar study six years earlier. Using a standard scenario where only stage 1 gonads are considered immature, CW50 (50 % of individuals are mature) for all Wales (north and south pooled) was 88 and 107 mm (males and females respectively), in line with regional literature. We found significant spatial variation, with significantly smaller gonadal CW50 in north Wales compared to south Wales, for both males (83 cf. 94 mm) and females (98 cf. 114 mm). By 119 mm CW, a high proportion (99 % males, 50–95 % females) were gonadally mature (standard scenario), morphologically mature (most sex and area combinations), and the smallest functionally (ovigerous) and behaviourally mature females had been recorded. We only found evidence for a significant decline in size at maturity since the previous study using a more conservative gonadal scenario, where stages 1 and 2 are considered immature. This found declines for both sexes in north Wales (and all Wales pooled) and females in south Wales. Our results suggest the MLS adequately protects immature individuals, but further management measures may be needed to address reported declines
Modelling the impact of future climate change on streamflow and water quality in Wales, UK
Get PDFClimate change is likely to have a major impact on future hydrological regimes, impacting numerous sectors reliant on surface waters. We use the Soil and Water Assessment Tool (SWAT) to model future (2021-2080) streamflow and water quality variables (nitrogen, phosphorus, suspended sediment, and dissolved oxygen), in five catchments in Wales, under a worst-case scenario of future greenhouse gas concentrations (RCP8.5). Results show a decline in annual average flows (-4% to -13%) but larger changes seasonally (spring, up to 41% increase; autumn, up to 52% reduction). The magnitude and frequency of high flow events increases in spring (magnitude: Sen’s slope range 0.165-0.589, p <0.01), with more low flows in autumn (Sen’s slope range 0.064-0.090, p <0.01). Water quality declines, with higher nitrogen, phosphorus, and sediment concentrations and lower dissolved oxygen levels. The findings have economic and environmental implications for abstractors, as water resources could become more unreliable, seasonal, and polluted
