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

过去200年来，农业景观中的淡水生物多样性主要受到人类活动的影响，特别是农业集约化。生物多样性的变化在长（几十年至几百年）和短（几年）的时间尺度上都有发生，其强度随时间和空间而变化。水生景观已经看到了物种种群的下降和生态退化的增加，因此调查的模式和变化的生物多样性在河流流域尺度上是很重要的，更好地了解生态和通知conservation.River格拉文，北诺福克，英国，提供了一个独特的机会，调查生物多样性在流域尺度上使用水生植物作为一个指标组。自20世纪90年代末以来，对流域内的水体（包括湖泊、池塘、河段、沟渠和回水）进行了广泛的水生植物调查，本论文涉及75种新的水生植物调查，旨在填补空间和站点类型的空白，以创建一个包含250多个站点和大约750个单独调查的数据库，为流域提供良好的空间覆盖率。该数据库用于解决三个关键问题：i）哪些水体类型拥有最稀有的物种和最具生物多样性？ii）如果流域面积丧失，流域生物多样性是否会下降？以及iii）现有的保护工作对流域生物多样性做了哪些工作？研究的另一个主要部分涉及对塞尔布里格池塘和贝菲尔德湖这两个关键湖泊遗址的两个沉积物岩心的宏体化石和硅藻进行古生态学分析，以研究过去两个世纪的生态变化。这两个网站显示以前良好的生态条件，随后一段时间的富营养化和随后的恢复，由于restorationworks.This项目展示了如何检查生物多样性在集水区规模与这样详细的空间覆盖允许被问到的独特的问题，因此，该方法可以更好地为保护工作提供信息。

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.