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A strategic programme for NERC Lowland catchment research
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Fine sediments, nutrient dynamics & biotic processes: summary

A fuller description of this project is also available.

Overview of project

Fine sediment plays an important role in the transfer and fate of nutrients through river basins. In recent years, groundwater-fed rivers throughout lowland England have exhibited increases in both suspended sediment loads and concentrations of macro-nutrients linked to changes in land use and river management practices. These increases have resulted in a number of environmental problems, not least for stream biota, and there is an urgent need for improved understanding of the fine sediment dynamics of lowland permeable catchments. This project investigated the complex interactions between sediments, river flows and biota in reaches of the Frome and Piddle catchments, Dorset. It focused on the role of aquatic macrophytes and suspension feeding invertebrates in trapping and transforming sediments and nutrients associated with sediments. See a schematic diagram of the sediment trapping processes.


The overall aim of the project was to establish the significance of biotic processes for instream sediment and nutrient budgets in lowland permeable catchments.  More about the aims of this project

Main findings

The research was important in quantifying:

  • the degree Ranunculus plants modify the flow in chalk streams
  • the associated spatial and temporal variability in the amount and character of fine particulate matter (especially its highly aggregated nature) that accumulates within chalk streams
  • the role of suspension-feeding invertebrates in sediment processing and retention; and
  • the biogeochemical processing within the trapped sediments and, in particular, the identification of chalk streams as significant sources of the greenhouse gases carbon dioxide, methane and nitrous oxide.  More about the main findings of this project

Description of activities

Field measurements:

  • Monthly mapping of in-channel vegetation and deposited sediments
  • Monthly measurement of flows at the reach scale
  • Flow velocity profiling around a Ranunculus stand
  • Sediment sampling for organic matter content and particle size analysis
  • Sampling of sediment pore water solutes and gases
  • Methane release from trapped fine sediments and gaseous exchange through Ranunculus stems. More about the activities carried out by this project

Field and laboratory based experiments:

  • Release of stained corn pollen to study the transport of fine particulate matter
  • Investigation of changes in blackfly larval faecal pellets through time
  • The potential for methane production and oxidation to take place beneath a Ranunculus stand was assessed. More about the activities carried out by this project

Areas of application

  • Implementation of the Habitats Directive and the Water Framework Directive
  • Sediment and nutrient management in chalk streams.

Related and future work

Two PhD studentships are currently investigating:

Researchers' details

Principal Investigator:

Co-Principal Investigator:


More researchers who worked on this project More researchers who worked on this project


All publications from this and other LOCAR projects are listed in the publications database.

Selected publications from this project are listed below. The full list of publications and recommended reading can be viewed in the full description page for this project Full publication list for this project

Selected publications

Wharton, G., Cotton, J. A., Wotton, R. S., Bass, J. A. B., Heppell, C. M., Trimmer, M., Sanders, I. A. and Warren, L. L. (2006) Macrophytes and suspension-feeding invertebrates modify flows and fine sediments in the Frome and Piddle Catchments, Dorset (UK). Journal of Hydrology 330: 171-184.

Wotton, R. S. and Wharton, G. (2006) Combining biology and hydrology - questions from an integrated study of chalk streams. In: Sediment dynamics and the hydromorphology of fluvial systems (Proceedings of a symposium held in Dundee, UK, July 2006). IAHS Publ. 306, 2006, pp. 331- 337.

Joyce, P., Warren, L. L. and Wotton, R. S. (2007) Faecal pellets in streams: their binding, breakdown and utlilization. Freshwater Biology 52: 1868-1880.

Full list of publications resulting from this project Full publication list for this project

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