TALKING SHIF: AN EXPLORATION OF HUMAN IMPACT ON CREEK HEALTH
To assess the relationship between creek health and land use in the watershed, measurements of benthic macroinvertebrate populations and water chemistry of nine Kalamazoo River tributaries were made over a two-week period in May and June of 2021. Standard macroinvertebrate sampling, counting, and classification approaches were used. Water chemistry data were acquired using handheld PC-60 multi-parameter testers. Human impact on land surrounding each tributary was quantified with a scaled human impact factor (SHIF) calculated using Kalamazoo County zoning data, in which higher SHIF values reflect more intensive urbanization.
Water conductivity data ranged from 427.33 S/m to 1305.67 S/m, and pH values ranged from 7.50 to 8.55. Macroinvertebrate data were evaluated while considering substrate type, as populations are strongly tied to substrate. Overall, data broadly show that pollution-sensitive macroinvertebrates tend to be more populous in lower SHIF tributaries, whereas pollution-tolerant macroinvertebrates are more populous in higher SHIF tributaries. From headwaters to mouth of creeks, a decrease in average species diversity correlated with increasing SHIF values in mud substrates. No statistical relationships between SHIF and macroinvertebrate biodiversity in gravel or sand, or pH, or conductivity were identified. Although the data do not conclusively permit rejection of the null hypothesis that human impact has no effect on river health, previous studies have shown such a link.
A future study would benefit from replicating sampling at creeks, use of satellite-based remote sensing datasets, and ground truth evaluation of land use. In addition, by extending the area studied into other watersheds, a greater range of human impact would be provided.