Assessing the differences in habitat between chalk and fen stream typologies

The freshwater environment provides many ecosystem services, vital to the functioning of global ecosystems and human health. Despite this, in England and Wales alone, around 300 water bodies are at high risk of not achieving good ecological status (GES). Through the aims of the Water Framework Directive (WFD), many initiatives are being taken to achieve GES. However this is at a time where the need for water from both human populations and industries is increasing. This exacerbates pressures from over-abstraction in already drought prone areas such as the East of England. Using the river Nar in Norfolk as a case study, this paper investigates the impact of low flow, caused by over-abstraction, on three indicator species: fish, macrophytes and benthos. Low flows have various impacts on different species; habitat availability reduces for macrophytes and benthos however remains relatively stable for spawning brown trout due to different habitat preferences (Garbe et. al. 2015). The differences in this habitat distribution during low flows between fen and chalk stream typologies have however little been explored. Results from habitat models (CASiMiR) combined with data both collected in the field and historical population data provided by the Environment Agency (EA) were used to explore the differences in fen and chalk streams and understand the difference in resilience to low flows each habitat provides. Extreme wet and dry years were focused on exploring the change in habitat availability and species population data. Mann-Whitney tests were also used to calculate statistically significant differences in results.