Organisms around the globe are experiencing novel environments created by human activities. One such disturbance of growing concern is the salinization of freshwater habitats from the application of road deicing salts, which creates salinity levels not experienced within the recent evolutionary history of most freshwater organisms. Moreover, salinization can induce trophic cascades and alter the structure of freshwater communities, but knowledge is still scarce about the ability of freshwater organisms to adapt to elevated salinity. We examined if a common zooplankton of freshwater lakes (Daphnia pulex) could evolve a tolerance to the most commonly used road deicing salt (sodium chloride, NaCl). Using a mesocosm experiment, we exposed freshwater communities containing Daphnia to five levels of NaCl (15, 100, 200, 500, and 1000 mg Cl− L−1). After 2.5 months, we collected Daphnia from each mesocosm and raised them in the lab for three generations under low salt conditions (15 mg Cl− L−1). We then conducted a time-to-death experiment with varying concentrations of NaCl (30, 1300, 1500, 1700, 1900 mg Cl− L−1) to test for evolved tolerance. All Daphnia populations exhibited high survival when subsequently exposed to the lowest salt concentration (30 mg Cl− L−1). At the intermediate concentration (1300 mg Cl− L−1), however, populations previously exposed to elevated concentrations (i.e.100–1000 mg Cl− L−1) had higher survival than populations previously exposed to natural background levels (15 mg Cl− L−1). All populations survived poorly when subsequently exposed to the highest concentrations (1500, 1700, and 1900 mg Cl− L−1). Our results show that the evolution of tolerance to moderate levels of salt can occur within 2.5 months, or 5–10 generations, in Daphnia. Given the importance of Daphnia in freshwater food webs, such evolved tolerance might allow Daphnia to buffer food webs from the impacts of freshwater salinization.

Liver tumours in flatfish have been diagnosed using histopathology for decades to monitor the impacts of marine pollution. Here we describe the application of specific gene (retinoblastoma, Rb) profiling in laser capture micro-dissected samples, and a suppression subtractive hybridization (SSH) approach to isolate differentially expressed genes in hepatocellular adenoma (HCA) samples from dab, Limanda limanda.The Rb profiles from apparently normal and HCA micro-dissected samples of fish from the North Sea showed no significant difference, and genotypic heterogeneity within defined histological phenotypes was observed. In the SSH, sequences associated with cell signalling, cell cycle, gene expression regulation, protein transport and protein degradation were isolated. These included up-regulation of arrestin domain containing 3 (arrdc3), Rac-1 and tribbles, and down-regulation of ankyrin repeat/sterile alpha-motif domain-containing protein 1B-like (ANKS1B-like), c-fos, CDKN1B and RhoA-like sequences, previously implicated in mammalian HCA. This study offers new candidates involved in fish liver tumour development.