For the removal of nutrients from eutrophic stream water polluted by non-point sources, an artificial aquatic food web (AAFW) system comprising processes of phytoplankton growth and Daphnia magna grazing was developed. The AAFW system was a continuous-flow system constructed with one storage basin of 3 m³ capacity, one phytoplankton tank of 3 m³ capacity, and one zooplankton growth chamber of 1.5 m³ capacity. The system was optimized by setting hydraulic retention time of phytoplankton tank as 3 days and D. magna density as 740-1000 individual l⁻¹. When the system was operated on eutrophic stream water that was delivering 471 g of total nitrogen (TN) and 29 g of total phosphorus (TP) loadings for 45 days, 250 g (53%) of TN and 16 g (54%) of TP were removed from the water during its passage through the phytoplankton tank. In addition, 64 g (14%) of TN and 4 g (13%) of TP were removed from the water by harvesting zooplankton biomass in the zooplankton growth chamber, resulting in significant overall removal rates of TN (69%), nitrate (78%), TP (73%), and dissolved inorganic phosphorus (94%). While the removal efficiency of the AAFW system is comparable to those of other ecotechnologies such as constructed wetlands, its operation is less limited by the availability of space or seasonal shift of temperature. Therefore, it was concluded that AAFW system is a highly efficient, flexible system for reducing nutrient levels in tributary streams and hence nutrient loading to large aquatic systems receiving the stream water.

Much of our current knowledge about non-limiting dietary carbon supply for herbivorous zooplankton is based on experimental evidence and typically conducted at ~1 mg C L–¹ and ~20°C. Here we ask how low supply of dietary carbon affects somatic growth, reproduction, and survival of Daphnia magna and test effects of higher water temperature (+3°C relative to ambient) and brownification (3X higher than natural water color; both predicted effects of climate change) during fall cooling. We predicted that even at very low carbon supply (~5µg C L–¹), higher water temperature and brownification will allow D. magna to increase its fitness. Neonates (<24 h old) were incubated with lake seston for 4 weeks (October-November 2013) in experimental bottles submerged in outdoor mesocosms to explore effects of warmer and darker water. Higher temperature and brownification did not significantly affect food quality, as assessed by its fatty acid composition. Daphnia exposed to both increased temperature and brownification had highest somatic growth and were the only that reproduced, and higher temperature caused the highest Daphnia survival success. These results suggest that even under low temperature and thus lower physiological activity, low food quantity is more important than its quality for D. magna fitness.

This corrects the article entitled “Daphnia magna fitness during low food supply under different water temperature and brownification scenarios” by the authors Andrea Gall, Martin J. Kainz and Serena Rasconi, published with DOI 10.4081/jlimnol.2016.1450. The data on somatic growth rates reported in the results section, paragraph “Life history traits”, page 165, were incorrect and the rectified data are presented. Fig. 4 has also been corrected accordingly.

1. Many prey organisms show adaptive trait shifts in response to predation. These responses are often studied under benign conditions, yet energy stress may be expected to interfere with optimal shifts in trait values. 2. We exposed the water flea Daphnia magna to fish predation and food stress and quantified both life history responses as well as physiological responses (metabolic rate, stress proteins, energy storage and immune function) to explore the architecture of defence strategies in the face of the combined stressors and the occurrence of trade-offs associated with energy constraints. 3. All traits studied showed either an overall or clone-dependent response to food stress. The chronic response to predation risk was less strong for the measured physiological traits than for life history traits, and stronger under food stress than under benign conditions for age at maturity, intrinsic population growth rate and offspring performance (measured as juvenile growth). Immune function (measured as phenoloxidase activity) was lower under predation risk but only at high food, probably because minimum levels were maintained at low food. 4. Overall, food stress induced stronger adaptive predator-induced responses, whereas more energy was invested in reproduction under benign conditions at the cost of being less defended. Our results suggest that food stress may increase the capacity to cope with predation risk and underscore the importance of integrating responses to different stressors and traits, and show how responses towards one stressor can have consequences for the susceptibility to other stressors.

Nanomaterials of various shapes and dimensions are widely used in the medical, chemical, and electronic industries. Multiple studies have reported the ecotoxicological effects of nanaoparticles when released in aquatic and terrestrial ecosystems; however, information on the toxicity of silver nanowires (AgNWs) to freshwater organisms and their transfer through the food webs is limited. In the present study, we aimed to evaluate the toxicity of 10- and 20-μm-long AgNWs to the alga Chlamydomonas reinhardtii, the water flea Daphnia magna, and the zebrafish and study their movement through this three-species food chain using a variety of qualitative and quantitative methods as well as optical techniques. We found that AgNWs directly inhibited the growth of algae and destroyed the digestive organs of water fleas. The results showed that longer AgNWs (20μm) were more toxic than shorter ones (10μm) to both algae and water fleas, but shorter AgNWs were accumulated more than longer ones in the body of the fish. Overall, this study suggests that AgNWs are transferred through food chains, and that they affect organisms at higher trophic levels, potentially including humans. Therefore, further studies that take into account environmental factors, food web complexity, and differences between nanomaterials are required to gain better understanding of the impact of nanomaterials on natural communities and human health.