Spatial and temporal patterns of aquatic macrophyte biodiversity at the river catchment scale: the River Glaven, north Norfolk

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Freshwater biodiversity over the last 200 years in agricultural landscapes has been primarily influenced by human activities, particularly agricultural intensification. Biodiversity changes have occurred on both long (decades-centuries) and short (years) timescales, and their intensity varies over time and space. Aquatic landscapes have seen declines in species populations and increases in ecological degradation, therefore investigating patterns of and changes in biodiversity at the river catchment scale is important for better ecological understanding and informing conservation.The River Glaven, north Norfolk, UK, provides a unique opportunity to investigate biodiversity at the catchment scale using aquatic macrophytes as an indicator group. Waterbodies in the catchment including lakes, ponds, river sections, ditches, and backwaters, have been extensively surveyed for aquatic macrophytes since the late 1990s and this thesis involved 75 new macrophyte surveys, targeted to fill gaps spatially and in site type, to create a database of over 250 sites and approximately 750 individual surveys providing excellent spatial coverage of the catchment. This database was employed to address three key questions: i) which waterbody types hold the rarest species and the most biodiversity? ii) if areas of the catchment are lost will catchment scale biodiversity decline? and iii) what have existing conservation efforts done for catchment scale biodiversity? The other major strand of the research involved palaeoecological analysis of macrofossils and diatoms of two sediment cores from key lake sites, Selbrigg Pond and Bayfield Lake, to examine ecological change over the last two centuries. Both sites showed previously good ecological conditions, followed by a period of eutrophication and subsequent recovery due to restoration efforts.This project demonstrates how examining biodiversity at the catchment scale with such detailed spatial coverage allows for unique questions to be asked and therefore how the approach can better inform conservation efforts.