When assessing river water quality, it is important to take hydromorphology into account. There is an increasing number of biomonitoring tools available for measuring the effects of changes in hydromorphology, and flow in particular, on river ecology. This project aims to adapt some of these biomonitoring tools for use in river monitoring programmes in Ireland, thereby providing additional information when assessing ecological status of Irish rivers.
Water flow is an important determinant of the biological community at a site, while morphological features, such as substrate composition and channel structure, also have an important role to play, and may mediate the influence of flow on the biological community in various ways.
This project will examine the relationship between river flow and three major groups of aquatic organisms: macroinvertebrates, fish and macrophytes.
The aims of this project are to:
1. Test a range of macroinvertebrate flow indices using historical and current data, and develop appropriate flow indices for use in Irish monitoring programmes.
2. Test a range of fish flow metrics using historical and current data, develop appropriate flow metrics for use in Irish monitoring programmes, and use statistical modelling approaches to determine optimal flow conditions for sensitive fish species.
3. Investigate the relationship between macrophytes and flow rates and develop a macrophyte-based flow index using historical and current data for use in Irish monitoring programmes.
4. Provide recommendations on the use of biomonitoring tools for flow in Irish river monitoring programmes.
Macroinvertebrates and Flow
Because different macroinvertebrate taxa have different preferences for the microhabitats which are created by river flow and river morphology, the taxa present at a site can reveal information about prevailing (and antecedent) flow conditions, and as taxa are lost from, or added to, a site’s community, this can reveal information about changes in flow regime. In general, as flows decline, there should be an increase in the abundance of macroinvertebrate taxa associated with slower velocity habitats and silty conditions, and a decrease in the abundance of taxa associated with faster velocities and coarser substrates. An increasing amount of work is being carried out to investigate whether biota can provide useful information for monitoring and assessing hydromorphology, using macroinvertebrates in particular.
Fish and Flow
Different species of fish (and different age classes of the same species) can have different requirements in relation to water quality, flow and substrate, and the loss of a species from a site may be influenced by a range of factors, including changes in hydromorphology. Although biotic indices in relation to flow are much more common for taxa other than fish, there have been some efforts to develop fish-based metrics to measure the impacts of flow. Another common approach in the study of relationships between the fish present at a site and its hydromorphology is to study optimal flow conditions for particular species using a statistical modelling approach.
Macrophytes and Flow
There is a large body of published material regarding aquatic macrophytes and their use as biological indicators of water quality and as a result, there is a wide variety of macrophyte-based assessment methods utilised under the Water Framework Directive. There is also growing evidence that aquatic macrophytes are effective as indicators of hydromorphological conditions within rivers, and that they act as ecosystem engineers, having a direct impact on river habitat conditions. Despite this there are few known or established plant-based hydromorphological assessment tools to date.