Aquatic Invertebrates

CHART 1: Hartley Pond and Tischer Creek

The high numbers of Daphnia indicate good quality unpolluted water and high productivity of aquatic life in the water. Any further conclusions require identifying the critters to species, genus or family and identifying and measuring the amounts of microscopic animals and algae.  Some species of caddisfly larvae are filter feeders, and some species are carnivores on larger critters.

This chart generally shows fewer individuals & larger-bodied animals in the higher trophic levels of our ponds as compared to those of the lower levels. This pattern is normal for aquatic communities everywhere.

CHART 2: Vernal Ponds

In every year the most common invertebrates found were mosquito larvae even in the years they were less abundant. The frequent inverse changes in numbers of mosquito larvae and Daphnia is due to the larvae feeding on young Daphnia..
In 2009 the numbers of both are off the chart. While it is possible there is that much of a difference from previous years that occurred, but more probable that it is due to more accurate counting that year.

Since the instructors’ main focus was on environmental experiences and not on ecological data gathering, the data in Chart 1 are from variable collecting and identification procedures according to what best fit the individual ages, abilities and instructional situations of each class. The accuracy of the counting varied according to the age of the children and the instructor’s emphasis on quantitative comparisons. The counting was probably the most accurate for daphnia and mosquito larvae in 2009.

None the less, a few major trends appear; high numbers of Daphnia, an almost microscopic animal, that feed on algae, smaller microscopic invertebrates and else, indicate productive ponds and non-polluted water. Their abundance varies widely, yearly and seasonally. The numbers in the charts may be partly due to how many classes each year actually paid attention to them because of their small size.

CHART 3: Fairmont Pond

The numbers and presence of aquatic insects and mites of Fairmont Pond seen above and in Carolyn Pond (shows a very similar chart), indicate good water quality in these ponds, little influenced by human activities.

Of the critters which are tolerant to pollution (mosquito larve, leeches, midge flies and worms), the mosquito larvae is the only one in which the numbers do not indicate water quality. The remaining primarily have large numbers occurring in polluted waters. Since we are not seeing that happening, it is a reasonable assumption that the waters are good quality.

Other indicators of the good water quality of Hartley's ponds and streams are the joint presence or high numbers of caddisfly, damselfly, dragonfly, mayfly and stonefly larvae or nymphs, predaceous diving beetles, clams, snails, water boatmen, water mites, water striders, and whirligig beetles, and low numbers of leeches and midges.

Of the ponds we sample, Fairmont Pond fufills most clearly the defined characteristics of a vernal pond. It is also the most frequently sampled by our Citizen Scientist classes. It is probable that the great yearly changes in population sizes are due to changing bioecological dynamics within the pond. More frequent sampling throughout the the active part of the year for several years might show more clearly what’s going on.

This project was funded in part by the Coastal Zone Management Act, by NOAA's Office of Ocean and Coastal Resource Management, in conjunction with Minnesota's Lake Superior Coastal Program