An application of canonical correspondence analysis for developing ecological quality assessment metrics for river macrophytes

Abstract

1. Aquatic macrophyte composition and abundance is required by the European Union's Water Framework Directive for determining ecological status. Five metrics were produced that can be combined to determine the deviation of aquatic macrophytes from reference conditions in Northern Ireland's rivers. 2. Species optima and niche breadths along silt, nitrate, pH, conductivity and dissolved oxygen gradients were generated from aquatic macrophyte and water quality surveys conducted at 273 sites throughout Northern Ireland using Canonical Correspondence Analysis (CCA). Five metric scores based on these environmental gradients were determined at new monitoring sites using the mean optima of the species occurring at the site, weighted by percentage cover and niche breadth of each species. 3. A preliminary reference network of 32 sites of high physico-chemical and hydromorphological quality, and representative of the range of river types in Northern Ireland, enabled reference metric scores to be produced for each river type. Five unimpacted and twenty impacted sites were used for testing the performance of the metrics. By subtracting reference metric scores from metric scores at a monitoring site measures of ecological impact could be determined along five different impact gradients. Metrics were also combined to give a measure of total ecological change. 4. The metrics system distinguished unimpacted from impacted sites and correctly identified 77% of the known impacts. The metrics distinguished different types of impact, e.g. silt and nitrate. 5. Aquatic macrophyte occurrence and abundance has high natural variability at a site, both temporally and spatially. This method was designed to be sensitive to ecological change whilst reducing noise caused by natural variation.

Artificial neural network modelling of macrophyte indices based on physico-chemical characteristics of water

“…The results of the sensitivity analysis correspond with other research on the impact of physico-chemical parameters, including nutrients, on the macrophyte metrics of river degradation (Dodkins et al, 2005;Haury et al, 2006;Hering et al, 2006;Szoszkiewicz et al, 2006). The identified major impact of mainly phosphorus and alkalinity on MIR shows the value of this index as an indicator of eutrophication, which was shown earlier by other authors .…”

The potential habitats of two submerged macrophytes,Myriophyllum spicatumandHydrilla verticillatain the river ecosystems, South Korea

“…We found that variables associated with water environmental factors were important determinants of the distributions of M. spicatum and H. verticillata, especially chlorophyll a, electrical conductivity, nitrate nitrogen, suspended solids, water temperature, water depth, and water velocity. Gradients of these variables also determine suitable habitats for submerged macrophytes in previous studies (Dodkins et al, 2005;Lacoul and Freedman, 2006;Franklin et al, 2008).…”

An extended Benthic Quality Index for assessment of lake profundal macroinvertebrates: addition of indicator taxa by multivariate ordination and weighted averaging

“…Many investigators have applied multivariate ordination methods to generate a synthetic pollution gradient and then used species scores along that ordination dimension to indicate species tolerance to the measured stressor or, alternatively, used constrained ordination (CCA) to estimate species stressor optima. Such approaches have been developed for marine (Smith et al 2001) and stream benthic invertebrates (Davy-Bowker et al 2005), freshwater phytoplankton , and macrophytes (Dodkins et al 2005). An approach somewhat analogous to our WA method was developed by Rossaro et al (2007), who modified Wiederholm's (1980) BQI to include multiple lentic macroinvertebrate taxa for Italian lakes and more recently for lakes in the central European Alpine region (Rossaro et al 2012).…”