Global warming is already causing salinization of freshwater ecosystems located in semi-arid regions, including Turkey. Daphnids, which are important grazers on phytoplankton and a major food source for fish and invertebrates, are sensitive to not only changes in salinity levels, but also presence of predators. In this study, the interactive effect of salinity toxicity (abiotic factor) with predation pressure mimicked by the fish-exuded kairomone (biotic factor) and the effect of salt acclimation on daphnids were investigated. Impacts of these stressors on daphnid survival, life history and molecular profile were observed. The presence of the kairomone antagonistically alters the effect of salinity, as observed from the 24- and 48-h LC(50) values and survival results. Molecular findings provided solid evidence to this antagonism at even lower salt concentrations, for which antagonism was not evident with organismal data. Fish predation counterbalances the negative effect of salinity in terms of reserve energy density. Therefore, it is important to investigate multiple stressor effects in ecotoxicological bioassays complemented with molecular techniques. The single effect of increasing salinity resulted in increased mortality, decreased fecundity, and slower somatic growth in Daphnia, despite their acclimation to salinity. This insignificance of acclimation indicates that Daphnia do not have any physiological mechanisms to buffer the adverse effects of salinity, making it a very crucial factor. Salinity-induced reduction in population growth rate of freshwater keystone species Daphnia-despite acclimation-indicates that global warming-induced salinity may cascade through the food web and lead to dramatic environmental consequences in the structure of lake ecosystems.

Vertical migration of Daphnia represents the best-studied predator-avoidance behaviour known; yet the mechanisms underlying the choice to migrate require further investigation to understand the role of environmental context. To investigate the optimal habitat choice of Daphnia under fish predation pressure, first, we selected the individuals exhibiting strong migration behaviour. The animals collected from the hypolimnion during the daytime were significantly larger, being more conspicuous, and in turn performed stronger diel vertical migration (DVM) when exposed to fish cue. We called them strong migrants. Second, we provided the strong migrant D. pulex with food at high and intermediate (1 and 0.4 mg C l -1 , respectively) levels, which were well above the incipient limiting level and of high quality. They traded the benefits of staying in the warm water layer and moved down to the cold water in response to fish cue indicating fish predation. The availability of food allowed the animals to stay in the cold hypolimnion. However, at the low food level (0.1 mg C l -1 ), which is an additional constraint on fitness, Daphnia moved away from the cold hypolimnion. Poor food condition resulted in strong migrant Daphnia to cease migration and remain in the upper warmer water layer. Although temperature is known to be a more important cost factor of DVM than food, our results clearly show that this is only true as long as food is available. It becomes clear that food availability is controlling the direction of vertical positioning when daphnids experience a dilemma between optimising temperature and food condition while being exposed to fish cue. Then they overlook the predation risk. Thus, the optimal habitat choice of Daphnia appears to be a function of several variables including temperature, food levels and fish predation.

O rman yangınlarının ana sebebi insan faaliyetleridir. Bu nedenle bir alanda orman yangını riski, eğer bitki örtüsü ve topoğrafik özellikler de uygunsa, orman yangınına sebep olabilecek insan faaliyetlerinin etkisindedir. Çalışmamızda eğimin orman yangını riskine etkisi değerlendirilirken, son 10 yılda Türkiye'de meydana gelmiş orman yangınlarının başlangıç noktaları coğrafi bilgi sistemleri (CBS) ile analiz edilmiştir. Böylece eğimin orman yangını riskine etkisi konusunda objektif bir değerlendirme yapılmaya çalışılmıştır. Analiz sonuçlarına göre Türkiye'de orman yangınlarının %40,53'ü %0-10 eğim aralığında meydana gelmektedir. Ayrıca bu yangınların %87,16'sı %0-30 eğimde meydana gelmektedir. Sonuç olarak, genel kanıya zıt bir şekilde, eğim arttıkça orman yangını riskinin azaldığı tespit edilmiştir. Eğim orman yangını riskini ters orantılı olarak etkilerken orman yangını tehlikesini ise doğru orantılı olarak etkilemektedir. Anahtar KelimelerOrman yangını riski, risk indeksi, eğim, CBS.

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