THE EFFECTS OF ATMOSPHERIC POLLUTANTS AND HYDROLOGY ON THE DEGRADATION OF PANNE VEGETATION BY INVASIVE SPECIES

Pannes, intradunal ponds kept wet by the water table or springs, exhibit diverse and extremely sensitive vegetation. They are home to plant species found nowhere else in Indiana. These ecosystems are frequently threatened by encroaching anthropogenic activities; an excellent example being within the Indiana Dunes National Lakeshore (IDNL), where they have been placed on the second tier of conservation targets for recovery by the Chicago Wilderness Biodiversity recovery plan. The pannes at the IDNL have been exposed to atmospheric pollutants emanating from the surrounding steel and energy production facilities over the last century. Since 1986, the native vegetation of this area is slowly disappearing and is being replaced by invasive species like Phragmites australis and Typha spp. The cause of the degradation of the native vegetation is subject to some debate, perhaps the result of the accumulation of nitrogen and heavy metals from upwind utility and steel production or fluctuations in the levels of Lake Michigan (tied to the hydrology of these proximal panne ecosystems). To test these hypotheses, we took surface sediment samples from four of the 12 pannes at the IDNL, and analyzed these samples for nutrient and metal contents using standard geochemistry coupled with sequential extraction analyses (to characterize nutrient geochemistry). Cd, Cr, Cu, Mn, Ni, Pb, S, Zn, Ba as well as Hg are the metals being studied. Coupled with this geochemical approach are complementary ecological studies of panne vegetation, as well as analyses of hydrologic levels within the pannes and past projections of panne water table levels. Ground penetrating radar (GPR) was also used to determine the shape of the water table of the pannes. The results provided by this study could assist in the development of guidelines relating to the management of the plant species that are being exposed to these high levels of atmospheric pollutants from the surrounding industries.