Chalk streams drain areas of outcropping chalk and receive a significant proportion of their discharge from the substantial underground aquifers found within chalk geological formations. Chalk streams flow through open countryside, have high nutrient status, clear waters and a stable hydrological regime and these conditions promote the development of a substantial macrophyte community typically dominated by Ranunculus spp. These streams also support large populations of blackfly larvae which are found attached to the surfaces of submerged macrophytes. The larvae feed by using paired cephalic head fans to intercept particles passing in the water column. Blackfly larvae have a low assimilation efficiency and therefore a significant proportion of the ingested material is egested as faecal pellets. Studies have revealed these faecal pellets to be the dominant particles in the suspended load in some systems and this has important implications for particle transport and fate. This study investigated how blackfly larvae alter the size range of particles within streams through the production of faecal pellets and the presence and temporal dynamics of these faecal pellets within two chalk streams in Southern England. Experiments also established the factors that determine the fate of blackfly faecal pellets by investigating the interaction between the annual growth cycle of macrophytes and the accumulation and transport of faecal pellets the controls on the transport of faecal pellets, relating to physical variations in the pellet itself and the factors that influence the decomposition of this material within the stream.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:719130 |
| Date | January 2008 |
| Creators | Warren, L. L. |
| Publisher | University College London (University of London) |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://discovery.ucl.ac.uk/1446190/ |
Page generated in 0.0016 seconds