Erin P. Argyilan

Variability of Lake Michigan water level during the past 1000 years reconstructed through optical dating of a coastal strandplain

Post Nipissing-phase strandplains of the Great Lakes reflect late-Holocene water levels that are linked to climate variability, glacial isostasy, and changes in basin hydrology. This study examines a strandplain sequence at Bailey’s Harbor, Door County, Wisconsin, along Lake Michigan, which contains a record of water-level variations during the past 1000 years, following the separation of the Lake Michigan-Huron basin from the Lake Superior basin. Vibracores are used to define the current elevation of the foreshore facies in 25 preserved beach ridges. Optical ages for five individual beach ridges are compared with radiocarbon ages on basal peats from nine swales collected in a previous study. The optical chronology yields a ridge formation/preservation rate of 30 ± 2 yr/ridge similar to that of previous assessments. This study further demonstrates the efficacy of optical dating for deciphering late-Holocene beach-ridge sequences, providing multidecadal resolution. Lake level meets or exceeds, by at least 0.5 m, historic metrics at c. AD 1125—1225. The maximum water level after c. AD 1225 is comparable with that recorded by the instrumental data. There is a noticeable high lake level from c. AD 1560 to 1725. Dating of additional sites along Lake Michigan is required to establish local rates of glacio-isostatic adjustment, identify possible erosion of the outlets and to resolve lake-level records for individual lakes following the separation of the upper Great Lakes currently constrained to have occurred c. 2400 to 1200 years ago.

Characterization of Coastal Drift-Cell Sediment Processes Effecting the Restoration of the Southern Lake Michigan Shoreline

Hard structures along the southern shore of Lake Michigan restrict natural longshore sediment transport, destabilizing the shoreline, and dissecting the coast into localized shoreline reaches. A geometric design was used to sample (n = 590 nodes) at nine shoreline reaches near the Indiana Dunes National Lakeshore to characterize existing sediment in the offshore and onshore zones. Cluster Analysis grouped shoreline sites into two clusters. Factor Analysis showed that 35 % of the sand fractionation’s cumulative variance across all sites was explained by an increased loading on medium sand (0.250 mm) with a corresponding decrease loading on small pebbles (4.750 mm), and an additional 30 % of the cumulative variance was explained by a negative loading on very fine sand (0.075 mm). Individual clusters showed that 43 % of the cumulative variance within cluster one could be explained by increased loadings on fine and medium sand (0.149–0.250 mm) with a corresponding negative loading on small pebbles (4.75 mm). An additional 22 % of the cumulative variance was explained by the positive loading on coarse sand (0.850 mm). Cluster two was explained by a single factor (62 % cumulative variance) highlighting an increased loading on small pebbles and coarse sand, and decreased loadings on medium to very fine sand. Principal component analysis showed that sediment characterization of the swash zone provided the best explanation of between site variance.

Analytical Measurements to Improve Nonpoint Pollution Assessments in Indiana's Lake Michigan Watershed

The Salt Creek watershed in Porter County, Indiana, is a subwatershed within the Little Calumet-Galien watershed, the only one in Indiana that discharges to Lake Michigan. The state-approved watershed management plan for Salt Creek requires monthly measurements of general chemistry parameters, discharge, turbidity, and Escherichia coli concentrations from May to October. This pilot study was designed to utilize the strengths of the watershed management component in combination with research science measurements and analyses, to assess the nonpoint sources of pollution more accurately. The outcomes of the first-year study, which focused on dissolved anions, fluorescent whitening agents (FWAs), total suspended solids and discharge loads from September 2010 through April 2011, demonstrate the substantial increase in comprehension gained from such partnerships. While basic measurements of pH, dissolved oxygen, and other parameters offer an idea of the waterways health, the chloride, nitrate, and total suspended solids (TSS) loads showed significant seasonal stresses; and the chloride and nitrate concentrations provided insights into specific nonpoint pollution sources.

An environmental investigation of the mineralogical, geotechnical, hydrogeologic and botanical properties of subsurface flow constructed wetlands in Akumal Mexico

Akumal is one of the few locations where subsurface flow constructed wetland systems can be compared directly without major differences in environmental setting. These systems in Akumal have highly variable geotechnical properties and performance and most systems are not well functioning. A basic water quality survey indicates SFCW effluent in no case meets UNEP or USEPA guidelines for ammonia or phosphate for sensitive waters. Systems are undersized and many are planted with less than optimal vegetation. Aggregate is generally too coarse and pores are commonly occluded with organic matter. The mineralogy of the locally sourced aggregate used in the systems is dominated by calcite, aragonite, quartz, boehmite and chlorite and is generally beneficial for improving the water quality of the systems; however, dissolution is observed and is of some concern. Major systematic retrofit efforts to improve these systems are warranted and should focus on better vegetation choices, use of locally sourced smaller and less soluble aggregate, exclusive use of the local limestone source containing boehmite, more frequent exchange of the aggregate, and an increase of overall cell size. The systems in Akumal are a classic example of a technological solution to an environmental problem caused by human development that has outpaced the designed capacity for wastewater treatment. This investigation serves as a baseline for numerous future interdisciplinary investigations and outlines challenges facing coastal communities attempting to use subsurface flow constructed wetlands.