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Grubisic, M., Singer, G., Bruno, M. C., van Grunsven, R. H. A., Manfrin, A., Monaghan, M. T., et al. (2018). A pigment composition analysis reveals community changes in pre-established stream periphyton under low-level artificial light at night. Limnologica, 69, 55–58.
Abstract: Freshwaters are increasingly exposed to artificial light at night (ALAN), yet the consequences for aquatic primary producers remain largely unknown. We used stream-side flumes to expose three-week-old periphyton to LED light. Pigment composition was used to infer community changes in LED-lit and control periphyton before and after three weeks of treatment. The proportion of diatoms/chrysophytes decreased (14%) and cyanobacteria increased (17%) in lit periphyton in spring. This may reduce periphyton nutritional quality in artificially-lit waters.
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Karling, J. S. (1924). A Preliminary Account of the Influence of Light and Temperature on Growth and Reproduction in Chara fragilis. Bulletin of the Torrey Botanical Club, 51(12), 469.
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Woolsey, S., Capelli, F., Gonser, T., Hoehn, E., Hostmann, M., Junker, B., et al. (2007). A strategy to assess river restoration success. Freshwater Biol, 52(4), 752–769.
Abstract: 1. Elaborate restoration attempts are underway worldwide to return human-impacted rivers to more natural conditions. Assessing the outcome of river restoration projects is vital for adaptive management, evaluating project efficiency, optimising future programmes and gaining public acceptance. An important reason why assessment is often omitted is lack of appropriate guidelines.
2. Here we present guidelines for assessing river restoration success. They are based on a total of 49 indicators and 13 specific objectives elaborated for the restoration of low- to mid-order rivers in Switzerland. Most of these objectives relate to ecological attributes of rivers, but socio-economic aspects are also considered.
3. A strategy is proposed according to which a set of indicators is selected from the total of 49 indicators to ensure that indicators match restoration objectives and measures, and that the required effort for survey and analysis of indicators is appropriate to the project budget.
4. Indicator values are determined according to methods described in detailed method sheets. Restoration success is evaluated by comparing indicator values before and after restoration measures have been undertaken. To this end, values are first standardised on a dimensionless scale ranging from 0 to 1, then averaged across different indicators for a given project objective, and finally assigned to one of five overall success categories.
5. To illustrate the application of this scheme, a case study on the Thur River, Switzerland, is presented. Seven indicators were selected to meet a total of five project objectives. The project was successful in achieving ‘provision of high recreational value’, ‘lateral connectivity’ and ‘vertical connectivity’ but failed to meet the objectives ‘morphological and hydraulic variability’ and ‘near natural abundance and diversity of fauna’. Results from this assessment allowed us to identify potential deficits and gaps in the restoration project. To gain information on the sensitivity of the assessment scheme would require a set of complementary indicators for each restoration objective.
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Grubisic, M., van Grunsven, R. H. A., Manfrin, A., Monaghan, M. T., & Hölker, F. (2018). A transition to white LED increases ecological impacts of nocturnal illumination on aquatic primary producers in a lowland agricultural drainage ditch. Environmental Pollution, 240, 630–638.
Abstract: The increasing use of artificial light at night (ALAN) has led to exposure of freshwater ecosystems to light pollution worldwide. Simultaneously, the spectral composition of nocturnal illumination is changing, following the current shift in outdoor lighting technologies from traditional light sources to light emitting diodes (LED). LEDs emit broad-spectrum white light, with a significant amount of photosynthetically active radiation, and typically a high content of blue light that regulates circadian rhythms in many organisms. While effects of the shift to LED have been investigated in nocturnal animals, its impact on primary producers is unknown. We performed three field experiments in a lowland agricultural drainage ditch to assess the impacts of a transition from high-pressure sodium (HPS) to white LED illumination (color temperature 4000 K) on primary producers in periphyton. In all experiments, we compared biomass and pigment composition of periphyton grown under a natural light regime to that of periphyton exposed to nocturnal HPS or, consecutively, LED light of intensities commonly found in urban waters (approximately 20 lux). Periphyton was collected in time series (1–13 weeks). We found no effect of HPS light on periphyton biomass; however, following a shift to LED the biomass decreased up to 62%. Neither light source had a substantial effect on pigment composition. The contrasting effects of the two light sources on biomass may be explained by differences in their spectral composition, and in particular the blue content. Our results suggest that spectral composition of the light source plays a role in determining the impacts of ALAN on periphyton and that the ongoing transition to LED may increase the ecological impacts of artificial lighting on aquatic primary producers. Reduced biomass in the base of the food web can impact ecosystem functions such as productivity and food supply for higher trophic levels in nocturnally-lit ecosystems.
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Pocock, T. (2016). Advanced lighting technology in controlled environment agriculture. Lighting Research and Technology, 48(1), 83–94.
Abstract: There is a recent awareness of the importance of plants in our everyday lives. Light is a requirement for plants and serves two important roles. It provides energy for growth and provides information that elicits plant responses including, among others, plant shape, pigmentation, nutritional content and resistance to stress. Light is paradoxical to plants, it is a requirement however, in excess it is damaging. Plants sense and interpret light through many families of photoreceptors and through the energy state of the photosynthetic apparatus. Light emitting diodes (LEDs) are quickly replacing traditional light sources for human applications, and currently there is effort being put into tailoring these technology platforms for the plant community. Potential plant sensing pathways and the spectral effects on pigmentation and photochemistry in red lettuce are described.
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