Draft: 2/28/03
Walla Walla Basin Watershed Council’s
Macroinvertebrate Sampling Report
1999 – 2002
Robert J. Bower
Objectives:
- To quantify seasonal variations in macroinvertebrate populations and community dynamics in the Walla Walla River.
- To quantify and compare macroinvertebrate community trends as a tool to track water quality changes in the Walla Walla River.
- To assist in development of Eastern Oregon Index for macroinvertebrates by providing information to ODEQ and OWEB.
Materials and Methods
This project will characterize the stream’s macroinvertebrate community with a Level 3 assessment as described by the DEQ’s Water Quality monitoring guidelines. A Level 3 assessment provides a “sensitive measure of stream condition”, offering information that can be used for a variety of objectives. A Level 3 assessment provides a more detailed characterization of the stream and does not increase field sampling or sorting time. The main difference is in the level of taxonomic identification, as the Level 2 assessment deals with family level ID and the Level 3 down to genus/species. The macroinvertebrate samples were sent to a Aquatic Biology Associates (A.B.A.) in Corvallis, Oregon for the Level 3 identification. A.B.A. has developed a biomonitoring protocol for assessing benthic invertebrate communities: primarily for use in Montane streams in Western North America, similar to that of the Index of Biological Integrity (I.B.I) developed by Karr et. al. (1986).
Macroinvertebrate samples were collected with a D-ring shaped kick net from a single habitat type (riffle) at four monitoring sites. Samples will be sorted (sub-sampled) and preserved in the laboratory at the watershed council office. Labels will be stored in the sub-sample vials with information regarding the number of kicks composited and the number of squares sorted from a sorting tray.
To collect an invertebrate sample in the field:
1) Select a sample-reach at the site that is roughly 40 times the mean wetted channel width.
2) Select two riffles within the reach. From the downstream riffle, determine a sample point with a random number table.
3) Place the kick net on the stream bottom, perpendicular to the stream flow. Collect the sample by disturbing a 1-ft. X 2-ft. area of the stream directly upstream of the net.
4) Place the contents of the net in a sieve bucket.
5) Repeat the procedure to collect three more samples: one in the same riffle and two from the other riffle section.
6) Macroinvertebrates are removed from large objects such as rocks, twigs, and leaves in the sample. These objects are then removed.
7) Rinse as much of the fine sediment and smaller particles through the sieve bucket taking care not to wash insects through the sieve.
8) Place the sample in a jar or a Ziplock ® bag with an appropriate amount of 90% ethanol preservative. Carefully seal the jar or bag.
9) Label the sample with the appropriate information.
10) If at a monitoring site that is to be duplicated for quality control (QC), repeat the procedure from step 3.
Analysis of the samples to the genus/species will enable the calculation of community metrics, or characteristics based on single or multiple taxa. A Level 3 assessment allows the calculation of the following metrics: taxa richness, mayfly richness, stonefly richness, caddisfly richness, sensitive taxa, sediment sensitive taxa, modified HBI, % tolerant taxa, % sediment tolerant taxa, and % dominant taxa. The calculation of these metrics will allow the estimation of a numerical value of biotic health (biotic index) that can be compared with a reference level of health from a similar stream(s) in the region.
Results and Discussion:
Samples were collected and processed during several periods, including once in August of 1999, and then seasonally in 2002, in June (spring) and August (summer). In 1999 and 2002, samples were collected at all of the following locations: Oregon/Washington Stateline (Pepper’s Bridge), South Fork Bridge (near mouth of South Fork Walla Walla River), North Fork Bridge (near mouth of North Fork Walla Walla River), and at Harris Park (the border between USFS and public lands.) In 2002 several sites were added to those sampled in 1999 to quantify improvements in the segment of the Walla Walla River where in 2000-2, a USFWS and Irrigation District agreement has restored approximately 25% of the summer low flows. These additional sites were Day Road (just above Milton-Freewater, Oregon), Nursery Bridge (site of agreement flow bypass), and Tumalum Bridge (where the river had been historically dry.) Figure 1 shows general locations and Table 1 describes exact locations for each of the sampling sites.
Data was collected according to the protocol described above in materials and methods and sent to a contractor for identification and benthic analysis. Data was processed by Aquatic Biology Associates, Inc. in Corvallis Oregon using their ABA protocol (Wisseman, 1996). The ABA system was developed specifically as a tool for benthic analysis in montane stream systems. The system uses the scoring of three main categories: primary metrics (total abundance, total taxa richness, EPT richness, % dominant taxa and community tolerance), positive indicators (predator, scraper, shredder richness and a variety of other indicators) and negative indicators (% collectors and parasites, and other indicators). The composite[1] scoring of these three categories gives the “Erosional total”. This total score can be used to compare to the General Biotic Integrity and Impact Categories for biotic health scoring.
However, as this system was developed for “ use(d) on: rivers; large, open streams, basins or valley streams; low gradient sites; alpine/subalpine streams or small streams.” (Wisseman, 1996) we found the overall ABA protocol score not applicable for most of our sites due to differences in specific site characteristics and their location in our watershed (most were considered valley sites). The site at Harris Park is probably the only site that may fall into the specific site criteria for the ABA protocol, however as system was developed for a coastal montane system, we still felt uncomfortable using it to score our NE Oregon, montane system. However, after consultation with Bob Wisseman at ABA, we found that some of the more generic component parts of the ABA protocol to be useful for our trend and seasonal benthic monitoring objectives.
Understanding that the Erosional Total (ET) scoring is a fixed template with which to look at the community (and not associating a particular health score with it) we can it to document seasonal trends in community structure for 2002. The June, 2002 sampling generally had a higher ET scoring than the August sampling (Figure 2). This is particularly evident in the lowest three river sites on the river. One possible explanation of this trend may be that the ET scoring gives a positive or higher value to scrapers, shredders and predators, and a negative scoring to collectors (etc.), which would indicate a seasonal shift from late spring to summer, in the community structure and composition. A higher score (June) would demonstrate a community composing more of primary shredders; scrapers and predators while in August the community (with lower ET scores) would have more collectors, etc. This would parallel what we know of water quality conditions in these areas of the river where water temperatures tend to increase and peak around the time of the August samplings. Percentages of benthic species “tolerant” of poorer water quality conditions also would increase with the lower ET scoring.
Figure 2.
Another trend clearly noted in the data was that of the Total Abundance. Total abundance is a measure of the total number of macroinvertebrates in a particular sample. Figure 3 shows that for all sites along the river, the August samplings clearly had much higher total populations when compared to that of June. This information, used in combination with the ET scoring, helps us to quantify the magnitude of these community shifts from shredders, predators, and scrappers to that of collectors and more water quality tolerant species particularly when used with conjunction with the EPT richness values (Figure 4.)
Figure 3.
The EPT taxa richness represents the total number of insect orders Ephemeroptera + Plecoptera + Trichoptera. These orders include the more commonly known groups of insects referred to as caddis, may and stone flys considered to be the primary food of many fish species. Many of these taxa are some of the most intolerant aquatic invertebrates, though tolerant forms can also be found in these orders. “EPT richness appears to be a good indicator of overall habitat/water quality” (Wissman, 1996). Using the EPT scoring along with the information provided by the Erosional and Total abundance seasonal values, we see (Figure 4) that while there the abundance values show community structure trending toward a more collector/tolerant dominant community, the EPT values did not change as drastically from June to August at the sites. This meant that the number of may, caddis and stone flys remained relatively the same, while the total number of collectors and water quality tolerant species increased dramatically. At most of the upper river sites (Harris Park to Day Road), there was a slight increase in EPT numbers while in the lower part of the river (where water quality conditions become much more impacted seasonally, due to low shade and flow volumes) the number decreased slightly. The exception of this trending was at the Harris Park site, which showed a drop in ETP numbers from June to August. A possible reasons for the lower 2002 score at this upper site may be from increased near and instream activities that occur at the park during the summer months. Activities such as fishing, swimming and picnicking may adversely effect the scoring at this location. The 2002 sample was collected in the river adjacent to the park while the 1999 sample was collected upstream of that high use area.
Figure 4
In order to assess the year-to-year water quality and macroinvertebrate community trends we compared Erosional totals of the August 1999 samples to those collected in 2002 (Figure 5). We observe that the Harris Park site may have been affected by the above-mentioned issues, and scored lower for 2002 when compared to 1999 (Figure 3). However, for the rest of the mainstem and South Fork Walla Walla River sites we see slightly higher ET scores. Of particular interest, is the Peppers Bridge site (which is now, due to the above mentioned agreement, is connected to the upper sites by a continuously flowing river) scored slightly higher in 2002 than in 1999.
Figure 5
The Tumalum Bridge is a site located at the bottom end of the USACE levee river section and is a good representative of pre-post agreement river conditions. Historically, the section of river between Nursery and downstream of Tumalum Bridge was for all practical purposes, dry during a majority of the irrigation season, due to a combination of irrigation diversions and high channel bed losses. In 1999, the river was dry at the Tumalum Bridge site (Figure 6). Starting in 2000, the USFWS and Irrigation districts processed an agreement that incrementally increased the amount of water left in this section of the river in order to accommodate for moved of the basin’s known ESA listed Bull Trout population. In 2002, the amount of water left in river was to be at least 25 cubic feet per second (cfs). While no sample was collected at the Tumalum location in 1999, it is inferred the known absence of water in turn meant an absence of aquatic macroinvertebrates. We acknowledge that there may have been macroinvertebrates present in the sub-surface gravels but make the assumption their richness and health to be marginal.
Figure 6.
Conclusions:
Analysis of the WWBWC’s macroinvertebrate sampling showed differences in year-to-year comparisons as well as difference in the community structure and abundance. Some sites downstream of the USFWS/Irrigation district agreement points showed dramatically different macroinvertebrates results. However, the data from this work needs to be further analyzed to depict and quantify trends in the basin. The following tasks are to be preformed during the coming year (2003):
- Utilize ODEQ’s Eastern Oregon Indexing efforts (particularly from work done in the Grande Ronde Basin) to compare and contrast regional trends and biotic health information. We hope to add our information to the Eastern Oregon Index efforts in to have a better regional meter with which to assess macroinvertebrate conditions.
- Work with Xerces staff to refine these results and future macroinvertebrates sampling strategies for our basin. The WWBWC has submitted a request for assistance to Xerces (OWEB funded) for technical assistance. This may included working with other regionally developed indexes to better assess our watershed specific conditions.
- Integrate the macroinvertebrate information with the other water quality components to better assess overall improvements to the system. This includes known flow, temperature, and water quality data for 1999 and 2002.
- Provide this data to the varies other monitoring efforts being conducted in the basin, and in particular to the fish habitat and telemetry work being done by ODFW, CTUIR and the USFWS. Food availability and timing should prove useful information for understanding life cycle habits for the basin’s ESA listed fish species.
References:
Wisseman, Bob,. Benthic Invertebrate Biomonitoring & Bioassessment in Western Montane Streams. Aquatic Biology Associates, Inc. Corvallis Oregon, 97330. email: .
Bower, Robert,. Walla Walla Basin Watershed Council’s Quality Assurance and Control Plan, 2001 (2002). WBWWC PO. Box 68 Milton-Freewater, Oregon. 97862. Email:
[1] Negative indicators are added to composite scoring as an inverse number.