Plant and animal community changes associated with the Cardiff Bay Barrage

• Main Author: Reed, James Peter
• Format: Thesis
• Language: English
• Published: 2007
• Subjects: QH301 Biology; Anas acuta; Anas clypeata; Limosa limosa
• Online Access: https://orca.cardiff.ac.uk/id/eprint/54641/; https://orca.cardiff.ac.uk/id/eprint/54641/1/U585030.pdf

The closure of the Cardiff Bay Barrage in November 1999 signified the end of a period of slow estuarine maturation, and the beginning of a period of more rapid freshwater succession. Such a marked ecological change has rarely been studied, and provides an opportunity to gain insights into the consequences of both natural and anthropogenic changes in the wetland environment. The current thesis describes the results of a study into the changes in habitats, plants, invertebrates and birds which have occurred as a result of Barrage closure. It includes overviews of the background to the Cardiff Bay Barrage project, the pre-Barrage estuary, and the post-Barrage ecological succession. Four main chapters are dedicated to outlining the changes in habitats, macrophytes, macro invertebrates and birds. The overall habitat diversity of Cardiff Bay increased as a result of Barrage closure, mainly because of the establishment of clear habitat zones in formerly uniform inter-tidal areas. Macrophytes were found to have increased from less than 30 species to over 80 in the same post-Barrage area. Macro invertebrate diversity also increased significantly - although this was countered by a reduction in overall abundance - a result of the generally lower productivity of freshwater versus estuarine habitats. Birds likewise showed an overall increase in diversity at the expense of a loss in abundance, especially of wading birds. Most of the increase in diversity was due to an increase in herbivorous and piscivorous species. Birds of the Gwent Levels Wetland Reserve (part of the compensation package for the loss of the Taff7Ely SSSI in Cardiff Bay), were also subject to a brief analysis. This area now attracts a wide diversity and abundance of wetland birds, and has fulfilled one of its primary objectives by attracting Nationally Important numbers of Shovelers Anas clypeata, Pintails Anas acuta and Black-Tailed Godwits Limosa limosa.