AB publishes rigorously refereed and carefully selected Feature Articles, Research Articles, Reviews and Notes, as well as Comments/Reply Comments (for details see MEPS 228:1), Theme Sections, Opinion Pieces (previously called 'As I See It') (for details consult the Guidelines for Authors) concerned with the biology, physiology, biochemistry and genetics (including the ’omics‘) of all aquatic organisms under laboratory and field conditions, and at all levels of organisation and investigation. Areas covered include: -Biological aspects of biota: Evolution and speciation; life histories; biodiversity, biogeography and phylogeography; population genetics; biological connectedness between marine and freshwater biota; paleobiology of aquatic environments; invasive species. -Biochemical and physiological aspects of aquatic life; synthesis and conversion of organic matter (mechanisms of auto- and heterotrophy, digestion, respiration, nutrition); thermo-, ion, osmo- and volume-regulation; stress and stress resistance; metabolism and energy budgets; non-genetic and genetic adaptation. -Species interactions: Environment–organism and organism–organism interrelationships; predation: defenses (physical and chemical); symbioses. -Molecular biology of aquatic life. -Behavior: Orientation in space and time; migrations; feeding and reproductive behavior; agonistic behavior. -Toxicology and water-quality effects on organisms; anthropogenic impacts on aquatic biota (e.g. pollution, fisheries); stream regulation and restoration. -Theoretical biology: mathematical modelling of biological processes and species interactions. -Methodology and equipment employed in aquatic biological research; underwater exploration and experimentation. -Exploitation of aquatic biota: Fisheries; cultivation of aquatic organisms: use, management, protection and conservation of living aquatic resources. -Reproduction and development in marine, brackish and freshwater organisms