Biological Monitoring
Rum River South
| Monitoring Location | behind Anoka High School, Anoka |
| Monitored By | Anoka High School Anoka Conservation District staff |
| Number of Years Monitored | 3.5 yrs |
| Background: The Rum River originates from Lake Mille Lacs, and flows south through western Anoka County where it joins the Mississippi River in the City of Anoka. Other than the Mississippi, this is the largest river in the county. In Anoka County the river has both rocky ripples as well as pools and runs with sandy bottoms. In the southern half of Anoka County slow water, silty bottom conditions dominate. The river's condition is generally regarded as excellent. Portions of the Rum River in Anoka County have a state "scenic and recreational" designation. The sampling site is near the Bunker Lake Boulevard bridge behind Anoka High School. Sampling is not conducted in the main channel. Rather, it occurs in a backwater area. Water is not flowing in this location and the bottom is mucky. This site is not particularly representative of this reach of the river. |
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| Results Monitoring was planned in 2006, but did not occur because the Anoka High School ecology class that planned to monitor was not offered due to lack of student enrollment. The results presented below are 2005 results. Anoka High School classes monitored this stream in both spring and fall 2005, with oversight by the Anoka Conservation District. The various indices, taken together, indicate a below average macroinvertebrate community. In 2005, and historically, the family biotic index is well below the county mean, and few of the pollution-sensitive EPT families are found. The number of families found fluctuates widely, sometimes above and sometimes below the county mean. However, most of the families are pollution-tolerant generalists. |
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| Discussion Biomonitoring results for this site are much different from the monitoring farther upstream in St. Francis. In St. Francis the Rum River harbors the most diverse and pollution-sensitive macroinvertebrate community of all sites monitored in Anoka County. At the Anoka location the biotic indices indicate a poorer than average river health. The reason for this dramatic difference is probably habitat differences, and to a lesser extent, water quality. The habitat and overall nature of the river is different in St. Francis and Anoka. In the upstream areas around St. Francis the river is steeper gradient, moving faster and has a variety of pools, riffles, and runs. Upstream the bottom is rockier and the lower human population density generally means there are fewer areas of disturbance and fewer storm water inputs. Downstream, near Anoka, the river is much slower moving, lacking pools, riffles and runs. The bottom is heavily silt laden. The area is more developed, so there are more direct and indirect human impacts to the river. Overall, there is less desirable habitat for invertebrates in the downstream reaches. Water quality also declines downstream, though is still quite good at all locations. Chemical monitoring in 2004 revealed that total suspended solids, total phosphorus, and chlorides were all higher near Anoka than upstream. This is probably due to the varied facets of a more highly developed watershed in these areas. Given that water quality is still quite good, it is unlikely that this factor is severely limiting macroinvertebrates. One additional factor to consider when comparing the up and downstream monitoring results is the type of sampling location. Sampling near Anoka was conducted mostly in a backwater area that has a mucky bottom and does not receive good flow. This area is unlikely to be occupied by families which are pollution intolerant because those families generally favor rocky habitats and require high dissolved oxygen not found in stagnant areas. |
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