Macroinvertebrates

Written by MH | 17 November 2009

Introduction­­­­­­­                                                                                                                        _

Much can be learned about the dissolved oxygen level and the quality of a body of water by the number and diversity of macroinvertebrates living within. Some species are very sensitive to pollution, so if there are a lot of them, the water is clean. Some don’t need much oxygen to survive, so if there are a lot of those species but no others, then the water has a low dissolved oxygen level. When four groups set off to analyze different bodies of water (all rivers) around Tower, they had questions in their minds. Does flow rate affect the number or diversity? What about bottom composition?

Materials and Methods­­­­­­­                                                                                                      _

At each area, four Hester-Dendy Samplers were placed in the water facing into the current, and left there for one month.

After the month was up, all samplers were collected and taken back to the school in buckets filled with water (except for one group), though some samplers had gone missing. All macroinvertebrates were taken out of the water and the samplers, dunked in isopropyl alcohol, and identified at least down to the order with dissecting microscopes.

Results­­­­­­­                                                                                                                                 _

Six different orders of macroinvertebrate were found; Diptera, Trichoptera, Odonata, Amphipoda, Ephemeroptera, and Plecoptera, with Diptera by far being the most common. However, the name of the order isn’t as important as the order’s preferred dissolved oxygen level and its tolerance of pollution.

Discussion­­­­­­­                                                                                                                           _

The results from the first graph don’t seem to show any correlation between flow rate and number of organisms, but that could be due to not following protocol. Perhaps some groups were better at picking out the little worms. At least one sampler was missing from the water, so there could have been more. One group didn’t bring their samplers back in a water bucket, so some organisms may have jumped off.

The second graph shows that Medium-Oxygen organisms predominate, which in turn says that the water around Tower has a medium to high dissolved oxygen level. Several of the orders found are also very sensitive to pollution, which indicates that some of the water is healthy and high-quality.

The third graph does show a correlation between flow rate and number of unique species. The two areas with the fastest water also had the most unique species.

This shows that the water around Tower is very healthy water, and it is important that it stays that way. The people should be proud of their clean water and not throw things in the river or let fertilizer and salt run off into it. Also, heat decreases dissolved oxygen level, so clear-cutting to the edge of the river will eliminate shade, heat up the water, and wreck the dissolved oxygen level. The macroinvertebrates are the basis of the food chain, and support everything from minnows to walleye to birds of prey.