Using macroinvertebrate assemblages and related environmental attributes to assess ecological condition of Iowa prairie pothole wetlands

Macroinvertebrate assemblage characteristics and environmental attributes were measured in 17 semipermanent/permanent prairie pothole wetlands of Iowa.  Objectives were to 1) provide initial descriptions of macroinvertebrate assemblages, and 2) identify useful physicochemical and biological attributes for ecological condition assessment.  Macroinvertebrate abundance and taxa richness were positively related to plant/coarse detritus abundance and tiger salamander presence, and negatively related to nitrogen, phosphorus, turbidity, and presence of large-bodied fishes.  From statistical relationships and knowledge of underlying mechanisms among attributes, we concluded that total macroinvertebrate taxa richness, high plant/coarse detritus abundance, and tiger salamander presence were indicative of good ecological condition, whereas high turbidity, nitrogen, and phosphorus, and large-bodied fish presence reflected poor condition.  These indicator attributes were used to construct a preliminary ecological condition index for Iowa prairie pothole wetlands.  Presence/absence of large-bodied fishes appeared to be the primary determinant of wetland condition.  Fish predation reduces macroinvertebrate and salamander abundance.  Additionally, excretion and benthic habitat disturbance by fishes indirectly reduces invertebrate and salamander abundance by increasing turbidity and nutrient concentrations, and reducing plant abundance.  To effectively assess and improve condition of Iowa’s prairie potholes wetlands, we recommend 1) routine measurement of identified indicator attributes, and 2) eliminating and excluding large-bodied fishes from wetlands.