Water Stewardship Information Sources
| ID | 988 |
|---|---|
| Citation | Jensen, EV. 2006. Cumulative effects monitoring of Okanagan streams using benthic invertebrates, 1999-2004. BC Ministry of Environment. |
| Organization | Ministry of Environment |
| URL | http://www.env.gov.bc.ca/epd/regions/okanagan/waterqual/pdf/monitor_ok_benthic_06.pdf |
| Abstract/Description or Keywords | In this study, benthic invertebrates were collected from 23 low elevation Okanagan stream sites between 1999 and 2004. Replicate sampling used a Surber net and data analysis followed the Benthic Index of Biological Integrity concept developed by Karr (Karr and Chu, 1999). Streams representing a gradient of conditions from low stress to high stress due to human alteration or use of the watershed were examined. Potential stress levels were established through GIS analysis at the watershed level and at the sampling reach for in-stream and near stream habitat condition. Low stress or reference sites and watersheds had low urban, agriculture, timber harvest factors, as well as low instream and near stream habitat alteration. High stress or high impact sites were chosen in watersheds and locations with high urban and agriculture landuse, and demonstrated degraded near and instream habitat. Categorical ranking by upper and lower relative stressor levels allowed calibration of a benthic index of biological integrity (B-IBI) for Okanagan streams. Five benthic invertebrate measures responded predictably over space and time to cumulative stress in valley bottom stream locations. These metric included total taxa, number of plecoptera taxa, number of ephemeroptera taxa, number of intolerant taxa, and number of clinger taxa. These metrics were found to respond predictably to cumulative watershed disturbance and clearly distinguished urban and highly altered sites from low impact sites. Secondary metrics, which responded predictably but did not clearly distinguish high and low stress categories were: number of trichoptera, Hilsenhoff biotic index, percent tolerant, percent predators and percent dominance. Primary metrics were summed into a multimetric index (B-IBI) and partitioned into excellent, good, fair, poor and very poor stream condition categories. The primary and secondary metrics correspond well to metrics used in B-IBI systems employed elsewhere in the Pacific Northwest. B-IBI scores were highest for stream sites on Equesis, Peachland, Shorts, Whiteman, Ellis upstream of Penticton, Chute, McDougall ups of Hwy 97, Coldstream and Lambly Creek (see Table 6 for site details). These sites were considered good to excellent, having a full range of biological diversity and presence of species sensitive to variety of stressors such as thermal, flow, sediment and toxic contaminants. B-IBI scores were lowest for Kelowna, Ellis near Okanagan River, Vernon at 25th Avenue in Vernon, Trout Creek near Hwy 97, Shuttleworth in Ok Falls, Eneas and Prairie Creeks in Summerland and BX Creek at 30th Avenue in Vernon. These sites were judged to be in poor or very poor condition, having almost half the species diversity as the reference group and very few intolerant taxa. A large number of stream sites were ranked as fair (see Table 6) and have some loss of biodiversity. iii Water and sediment chemistry samples were collected during the study to complement the biological sampling. Water quality data indicated that in urban and agriculture settings, bacteriological measures frequently exceed drinking and recreational water quality guidelines. Aquatic life protection guidelines were rarely challenged. Nitrate nitrogen was often orders of magnitude higher in streams flowing through urban and agriculture settings. Reduced sediment quality was more common in urban streams. Polycyclic aromatic hydrocarbons (PAHs) were often elevated in urban stream sediments of BX, Kelowna, Ellis and Eneas creeks. PAHs in BX Creek at 30th Avenue were consistently above Canadian Council of Ministers of the Environment (CCME) aquatic life interim sediment guidelines but below probable effects levels. Lead and zinc were higher in BX and Kelowna creek sediments than other streams, and average values were between the CCME interim and probable effect levels. Pesticide analysis of stream sediments in 2003 found DDE (a breakdown product of DDT) above CCME aquatic life probable effects levels in Kelowna and Eneas creeks. Endosulphan was also detected in Eneas Creek. PCBs were not detected in urban sediments above detection limits. Further sampling and analysis would be required to describe variation in water and sediment quality for these study sites. Re-evaluation of the same habitat, water and sediment chemistry, and benthic invertebrate data set was carried out by Perrin (2006) using the Environment Canada's Benthic Assessment of Sediment (BEAST) software in CABIN (Canadian Aquatic Biomonitoring Network). Okanagan streams were classified by BEAST using the Fraser Basin reference groups as either unstressed, potentially stressed, stressed or severely stressed relative to Fraser Basin reference conditions, and then compared to B-IBI scores. BEAST was conservative in showing a better condition for 13% of the sites but a worse condition for 55% of the sites than was determined using the B-IBI process. Complete agreement of BEAST and B-IBI scores occurred for 29% of the sites, and 81% of the sites were within one stress category. No sites were more than 2 stress categories apart. The Okanagan CABIN data set and sediment quality data was further evaluated by Perrin (2006) using cluster analysis and multidimensional scaling. These analyses confirmed the BIBI classification of sites into the upper and lower stressor groups which were used in calibrating the Okanagan benthic index of biological integrity. Discriminant function analysis identified sediment PAH, nickel, manganese and water alkalinity as best discrimiants of the reference group and two high stress groups. Polycyclic aromatic hydrocarbons (PAHs) in sediments were identified as the strongest discriminator of benthic community in high impact stations. Cause and effect can not be presumed as other stressors such as impervious surface area or measures of stream flow variation are often associated with deteriorating biological condition. Given the specificity of the CABIN model to the Fraser basin and travelling kick net collection method, the overall agreement between the two methods of analysis is encouraging. The comparability of the B-IBI and CABIN outputs suggests that either the B-IBI or BEAST can be used with confidence on Okanagan low elevation streams. Both methods will detect impairment when applied in riffle habitats. Perrin suggests Surber collected data can be used for BEAST assessment but notes assessment error potentially increases. Data compiled for a BIBI analysis may also be used for more in-depth analysis, including multivariate analysis of habitat variables and anthropogenic stressors. iv Methods of benthic invertebrate collection and data analysis will continue to evolve. Although metric scoring criteria and metric selection varies somewhat between areas in the Pacific Northwest (Skeena, Fraser Valley, Puget Sound and Washington Cascade areas) the overall commonality in chosen metrics, enables comparable statements of aquatic ecosystem health among these study areas and could enable broad environmental reporting. Comparability of different methods applied in overlaping or adjacent areas through examination of performance characteristics (e.g., precision, sensitivity) known as a performance-based method system. The demonstrated common response of the Okanagan B-IBI with the Fraser Basin models and CABIN protocols may further allow harmonized reporting of environmental conditions across geographic and methodological boundaries. To this end, focused comparison of kick and surber net collections, and increased sampling of reference sites to develop an Okanagan model within CABIN is recommended. Defining benthic community response to stressors is potentially more powerful when spatial scales are reduced, and linking this work to probabilistic surveys would enable broader estimation of regional stream conditions. While harmonization of collection methods and analysis tools between jurisdictions and across borders is a worthy goal it is equally important to apply available information in a timely manner. Given that the B-IBI method has been calibrated for the Okanagan, it can be used to communicate aquatic ecological health and cumulative effects. Further effort must be made on a provincial scale to translate these and other indicator measurements into socially valued descriptors of the environment. Urban streams in the Okanagan are clearly degraded relative to Okanagan B-IBI reference sites, as well as Fraser Basin reference conditions. Reference condition assessments whether based on B-IBI or RCA may not necessarily require high specificity to be used to differentiate highly stressed sites from reference conditions, and provide better aquatic ecosystem condition definition than chemical measures. This information can be particularly useful to watershed and stormwater management efforts in the Okanagan Basin. As resource, site specificity or consequences of decisions increase, the burden of proof will necessarily rise and more stressor based assessments will be required. |
| Information Type | report |
| Regional Watershed | Okanagan |
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| Project status | complete |
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