Critical influence of seasonal sampling on the ecological quality assessment of small headwater streams

Abstract

Variability in the ecological quality assessment of reference sites was tested on small headwater streams in Ireland. Although headwater streams constitute a large portion of the river channel network, they are not routinely monitored for water quality. Various metrics were used including the Irish Q-value and the newly developed Small Streams Risk Score (SSRS), and metrics applied elsewhere in the Atlantic biogeographic region in Europe, including the Biological Monitoring Working Party score (BMWP), the Average Score per Taxon (ASPT), the Ephemeroptera, Plecoptera and Trichoptera taxa (EPT), the Belgium Biotic Index (BBI) and the Danish Stream Fauna Index (DSFI). The AQEM (version 2.5a) assessment software was used to apply some of these metrics. The spring and summer datasets are used to test the performance of biotic metrics with respect to season, and the applicability of their use to assess the ecological quality of wadeable streams. The quality status of most sites assigned by the various metrics was high using the spring invertebrate data, and an apparent considerable deviation in quality status occurred when the summer data was applied. Seasonal differences were noted using all the biotic indices and are attributed to the absence of pollution-sensitive groups in summer. Seasonal variability in the water quality status was particularly evident in acidic streams draining noncalcareous geologies with peaty soils that had relatively lower numbers of taxa. Some indices applied reflect a greater seasonal difference in the quality category assigned. The least amount of variability between seasons was obtained using the ASPT and the SSRS risk assessment system. Results suggest that reference status is reliably reflected in spring when more pollution-sensitive taxa were present, and that a new ecological quality assessment tool is required for application in summer when impacts may be most severe. This highly heterogeneous freshwater habitat seems to have too few taxa present in the summer to reliably determine the ecological quality of the stream using the available indices.

The impact of a catastrophic storm event on benthic macroinvertebrate communities in upland headwater streams and potential implications for ecological diversity and assessment of ecological status

“…the picking up and setting into motion) and abrasion of surface and subsurface substrates within and adjacent to the stream (Andrews, 1984;Andrews and Nankervis, 1995). Prior to the storm event on 24 October the instream habitats of the four sites were characterised by short riffle-run sequences, interspersed with shallow pools and were generally dominated by cobbles with some coarse gravel, sand and scattered large boulders, which is typical of small upland headwater streams in Ireland (Callanan et al, 2008;. The entrainment disturbance caused during the catastrophic event altered the natural sequence of instream habitats, causing severe damage to both the streambeds and banks in the four streams with the substrate composition changing to predominantly boulder and sand.…”

“…The three metrics calculated were the Small Stream Risk Score (SSRS) (Anonymous, 2005;Kavanagh et al, 2006), the Biological Monitoring Working Party (BMWP) Score and the Average Score Per Taxon (ASPT) (Hawkes, 1997), previously used in headwater stream assessment in Ireland (Callanan et al, 2008;. The before and after storm metric data were then tested for normality using KolmogorovSmirnov tests and compared using paired t-tests in PASW Statistics 18 (IBM SPSS, 2010).…”

Performance of selected macroinvertebrate-based biotic indices for rivers draining the Merendon Mountains region of Honduras

“…Samples were returned to the nearest camp to be live sorted and the contained macroinvertebrates were preserved in 70% ethanol. Individuals smaller than 1000µm may have been lost but this is a standard methodology often used in routine bioassessment (Wallace, Grubaugh & Whiles, 1996;Whiles et al, 2000;Dickens & Graham, 2002;Callanan, Baars & Kelly-Quinn, 2008). Specimens were returned to the laboratory in University College Dublin and identified to family level, this being the taxonomic level used in most bioassessment metrics.…”

“…All ASPT values exceeded 6,0 (Table 4), a value generally considered to represent high quality (Chutter, 1994;Chapman, 1996;Callanan et al, 2008). The IBMWP allocated 33,3% (5 sites) of sites to high quality, 46,6% (7 sites) to good and the remaining 20% (3 sites) to moderate quality (Table 4) (range 51,6 to 127) while the IASPT assigned 100% (15 sites) of sites to high status (range 6,27 to 7,30) ( Table 4).…”

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“…Destaca-se a importância das dimensões espacial (vertical, longitudinal e lateral) e temporal, devendo serem observadas mudanças físicas, químicas e biológicas, processos hidrológicos e geomorfológicos, ocasionados por fenômenos naturais ou por intervenção humana (Petts 2000;Brown e Pasternack, 2008;Hu et al, 2008). Na dimensão longitudinal do rio, observa-se o conceito de "Contínuo Fluvial" proposto por Vannote et al (1980), bastante citado na literatura eco-hidrológica para ecossistemas em movimento (Meyer, et al, 2003;Ciesielka e Bailey, 2007;Gore, 2007;Jørgensen et al, 2007;Callanan et al, 2008;Boulton et al, 2008;Burcher, 2009), que considera dentre outros aspectos, a contínua mudança nas condições ambientais do fluxo de primeira ordem para ordens superiores, dividindo o rio em três regiões geomorfológicas distintas: região de nascente (alta contribuição terrestre de sedimentos orgânicos), médio curso (mais relacionado com a produção de algas e plantas aquáticas) e proximidade da foz (disposiçãoà turbidez, carga elevada de sedimentos procedentes de montante). Montgomery (1999), no conceito de MEDEIROS, P. C.; SOUZA, F. A. S.; RIBEIRO, M. M. R. Aspectos conceituais sobre o regime hidrológico para a definição do hidrograma ambiental.…”