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.

Food contact materials can release low levels of multiple chemicals (migrants) into foods and beverages, to which individuals can be exposed through food consumption. This paper investigates the potential for non-carcinogenic effects from exposure to multiple migrants using the Cefic Mixtures Ad hoc Team (MIAT) decision tree. The purpose of the assessment is to demonstrate how the decision tree can be applied to concurrent exposures to multiple migrants using either hazard or structural data on the specific components, i.e. based on the acceptable daily intake (ADI) or the threshold of toxicological concern. The tree was used to assess risks from co-exposure to migrants reported in a study on non-intentionally added substances (NIAS) eluting from food contact-grade plastic and two studies of water bottles: one on organic compounds and the other on ionic forms of various elements. The MIAT decision tree assigns co-exposures to different risk management groups (I, II, IIIA and IIIB) based on the hazard index, and the maximum cumulative ratio (MCR). The predicted co-exposures for all examples fell into Group II (low toxicological concern) and had MCR values of 1.3 and 2.4 (indicating that one or two components drove the majority of the mixture’s toxicity). MCR values from the study of inorganic ions (126 mixtures) ranged from 1.1 to 3.8 for glass and from 1.1 to 5.0 for plastic containers. The MCR values indicated that a single compound drove toxicity in 58% of the mixtures. MCR values also declined with increases in the hazard index for the screening assessments of exposure (suggesting fewer substances contributed as risk potential increased). Overall, it can be concluded that the data on co-exposure to migrants evaluated in these case studies are of low toxicological concern and the safety assessment approach described in this paper was shown to be a helpful screening tool.