Effects of 4-nonylphenol, fish predation and food availability on survival and life history traits of Daphnia magna straus

Abstract

This study aimed to investigate the compound effect of environmentally relevant 4-nonylphenol (NP) concentrations and natural stressors-namely fish predation and food availability-on Daphnia magna, which were exposed to four NP concentrations (0, 1, 5 and 10 microg l(-1)) under optimum or low food concentrations (1.00 and 0.075 mg C l(-1), respectively) in water (un)conditioned by a fish predator (Alburnus alburnus). A(n) "environmentally relevant" and "no observable effect" concentration (NOEC) of NP (10 microg l(-1)) resulted in a significant reduction (P < 0.01**) in daphnids' survival when it was encountered concurrently with conditions of low food availability and presence of fish predation. The significance of the results lies in the observation that not only environmentally relevant concentrations of NP but also NP concentrations reported to have no observable effect on daphnids may in reality have unexpected critical effects on D. magna survival under conditions more parallel to natural ecosystems. The deterioration of the life-history traits-namely, NP-induced delay in the age at first reproduction (P < 0.001***) and fish kairomone-induced reduction in the size at first reproduction (P < 0.001***)-of the D. magna individuals is also crucial, as such alterations could significantly influence future generations and result in ultimate adverse effects at the community level because large-bodied daphnids are key-stone species in freshwater ecosystems. The results of this study demonstrate the importance of taking into account environmentally realistic conditions while investigating the effects of NOEC levels of toxicants on non-target aquatic species.

Biological interactions mediate context and species-specific sensitivities to salinity

“…We found direct effects of salinity on Plecoptera depended on biotic interactions with salt-tolerant taxa (figure 5b). Similar to the response of Plecoptera taxa that we found, Beklioglu et al [31] identified low and environmentally relevant concentrations of the organic toxicant 4-nonylphenol had no observable effects on Daphnia magna Straus in single toxicity tests with abundant food, but had strong effects when coupled with effects that might be expected in a real ecosystem (i.e. food limitation and predator cues).…”

“…Standard toxicity test methods are structured to minimize control mortality and estimates of toxicity, therefore biological interactions are deliberately avoided [49]. Physical disturbance [50], food limitation [31], and chronic exposure [51], are similarly not typically considered in toxicity tests, although all influence toxicant effects [49]. There are many examples of biotic interactions influencing stressor effects, antagonistically [36], synergistically [35], through delaying recovery [19], with effects in both positive and negative directions [14,19,33,36,49,52,53].…”

Impacts of salinity and fish-exuded kairomone on the survival and macromolecular profile of Daphnia pulex

“…In toxicity studies, single-trophic level testing does not accurately predict the 'real world', which is rather complex due to the presence of biotic interactions (Cairns 1983;Beklioglu et al 2010). Additionally, in order to better understand the mechanisms affecting the organismal level, it is crucial to reveal the molecular responses of target organisms to stressors.…”

Differences in long-term impacts of un-ionized ammonia on life-history traits of three species ofDaphnia

“…To keep the un‐ionized ammonia concentrations constant, the test solution in each beaker was measured and replaced with a fresh one every day. Ammonia test solutions were prepared by dissolving ammonium chloride NH 4 Cl (Sinopharm, Shanghai, China) in de‐chlorinated tap water . The experimental conditions were identical to those used for laboratory maintenance.…”