Groundwater Controls on Wetland Vegetation of a Ridge-and-Swale Chronosequence in a Lake Michigan Embayment
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KeywordRidge/swale wetlands . Lake Michigan
Wetland Vegetation--Lake Michigan
Groundwater Hydrology--Lake Michigan .
Climate Change--. Lake Michigan
Journal titleWetlands V. 40
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AbstractA chronosequence of wetland swales between beach ridges in the Manistique/Thompson embayments of Lake Michigan contains plant communities that differ across the strandplain.We characterized vegetation in 33 swales and compared distribution with previously reported groundwater flow systems. Older swales near a groundwater divide created by the peak Nipissing ridge receive local flows and hold sedge/leatherleaf floating mats that transition to swamp. Farther lakeward, another groundwater divide is created by discharge of calcareous waters released by termination of an underlying clay confining layer, resulting in swales dominated by northern white cedar. Cedar swamp continues lakeward in swales having flow-through calcareous groundwater, but several swales are perched above those flows. Farther lakeward, a large amalgamated beach ridge creates another groundwater divide with discharges that again support cedar swamp. Calcareous discharge from the confined aquifer, with downslope flow-through waters, then supports more cedar swamp. Flow-through waters meet yet another calcareous discharge, resulting in ponding and development of floating mats. Finally, a deep regional aquifer discharges at the Lake Michigan shore and supports marsh/shoreline species. Our results have implications for assessing potential responses to climate change, interpretation of past climate changes in paleoecological studies, and management of wetlands facing future climate changes
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Optically Stimulated Luminescence Dating of Late Holocene Raised Strandplain Sequences Adjacent to Lakes Michigan and Superior, Upper Peninsula, Michigan, USAArgyilan, Erin P.; Forman, Steven L.; Johnston, John W.; Wilcox, Douglas A.; Indiana University - Bloomington; Indiana University - Northwest; The College at Brockport; University of Illinois at Chicago (2005-01-01)This study evaluates the accuracy of optically stimulated luminescence to date well-preserved strandline sequences at Manistique/ Thompson bay (Lake Michigan), and Tahquamenon and Grand Traverse Bays (Lake Superior) that span the past ~4500 yr. The single aliquot regeneration (SAR) method is applied to produce absolute ages for littoral and eolian sediments. SAR ages are compared against AMS and conventional 14C ages on swale organics. Modern littoral and eolian sediments yield SAR ages b100 yr indicating near, if not complete, solar resetting of luminescence prior to deposition. Beach ridges that yield SAR ages b2000 yr show general agreement with corresponding 14C ages on swale organics. Significant variability in 14C ages N2000 cal yr B.P. complicates comparison to SAR ages at all sites. However, a SAR age of 4280 F 390 yr (UIC913) on ridge77 at Tahquamenon Bay is consistent with regional regression from the high lake level of the Nipissing II phase ca. 4500 cal yr B.P. SAR ages indicate a decrease in ridge formation rate after ~1500 yr ago, likely reflecting separation of Lake Superior from lakes Huron and Michigan. This study shows that SAR is a credible alternative to 14C methods for dating littoral and eolian landforms in Great Lakes and other coastal strandplains where 14C methods prove problematic. D 2004 University of Washington. All rights reserved.
Effects of Wind Stress, Wind Speed and Direction on Phytoplankton Abundance in the Nearshore Zone of Lake MichiganMakarewicz, Joseph C.; DeVault, David S.; The College at Brockport (1982-01-01)Phytoplankton data from a shore and offshore intake in the near-shore zone of Lake Michigan at Chicago were examined to determine the effects of wind speed and direction on phytoplankton density. Over the entire year, regression analysis indicated that a small (4.2 and 5.5 percent) but statistically significant portion of the daily variation in phytoplankton density at both sites occurred with densities increasing with increasing north winds. On days with only a north wind, wind speed accounted for 34.9 and 42.1 percent of the variation in phytoplankton abundance. During short periods ( < one month) of relatively constant water temperature (e.g., January), wind stress, independent of wind direction, explained nearly 50 percent of the daily variation at the shore intake with phytoplankton density increasing with increasing wind speed. In the Chicago area during periods of thermal stratification, southwesterly winds produced upwellings which were accompanied by higher densities of both diatoms and blue-green Oscillatoria. The higher densities of blue-green algae caused by upwellings have not, to our knowledge, been previously reported in Lake Michigan.
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