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Coastal and nearshore regions of most large lakes have not been included in monitoring efforts in a regular, consistent and comprehensive fashion. To address this need, we have been developing a survey approach using towed in situ sensors to provide spatially-extensive mapping of nearshore conditions. Within the last decade, we have applied a strategy of towing along the coastline in all five US/Canadian Laurentian Great Lakes. We have developed confidence in the strategy's ability to assess the entire nearshore region comprehensively and efficiently. This article presents an overview of steps of the development, a selection of representative results, and our continuing evaluation of the approach. Findings to date demonstrate an ability to establish linkages between conditions in the nearshore and adjacent watersheds at a variety of spatial scales, including to the US basin-wide level. Results here highlight two plankton sensors (fluorometer for phytoplankton and [laser] optical plankton counter ([L]OPC))...

The amount of excess fixed nitrogen removed from the freshwater aquatic nitrogen cycle, particularly by freshwater wetlands, through denitrification (DNF) is largely unknown. Typically, DNF rates increase within sediments that have higher organic content and a source of sufficient NO3−, in this context we measured DNF in organic-rich sediments of Lost Creek wetland on the south shore of Lake Superior, where NO3− concentrations have increased dramatically over the last century. The concentrations of N2, O2, and Ar were determined on intact water-sediment cores. Denitrification and respiration rates were determined using membrane inlet mass spectrometry and N2:Ar and O2:Ar ratios. Nitrogen flux rates measured in August 2000 and 2001 using overlying ambient wetland water, Lake Superior water, and nitrate augmented wetland water ranged from

Trophic linkages of larval fish in Lake Superior coastal habitats can be identified using naturally occurring differences in the stable isotope ratios of nitrogen (15N:14N, δ15N) and carbon (13C:12C, δ13C). We measured 13C and 15N values in common fish larvae weekly during spring run-off (late-April to mid-July) in the hydrologically complex drowned river mouth of the St. Louis River, the second largest tributary to Lake Superior. For all species, δ13C was increasingly negative with increasing weight as the fish developed from the yolk-sac stage, during which they possess a maternally-derived isotopic signature, to an exogenously feeding larvae. Trends in δ15N with increasing weight varied among species; an increase, decrease, and no change in δ15N were observed. A weight-based stable isotope turnover function modeled well the observed changes in δ13C and δ15N. In general, fish obtained a constant signature after a 10-fold gain in body mass, implying their tissue was at isotopic equilibrium with their diet. Difference between yolk-sac and larvae δ13C and δ15N revealed distinct patterns in larval origin and settlement. Based on the species analyzed, we identify two specific Lake Superior coastal wetland-dependent fish early life histories that incorporate habitat use, movement, and trophic dynamics. This study thus provides a methodological approach that can potentially help resolve interactions between watershed character, coastal productivity, and Lake Superior that are of significance to the lake's fisheries.

Selected comparisons of water quality and biological properties in lakewide samplings of the early 1970s and 2005–2006 illustrate a range of ecological changes within Lake Superior over the last three decades. Comparisons depict warmed surface layers, and increased chloride and nitrate concentrations—confirming trends described in recent literature. Our comparisons also depict some spatial dimensions of change, showing vertical and horizontal patterns throughout the lake as a function of depth and from shallow to deepest waters. The selected physico-chemical examples speak to different scales of source drivers for change (from local, to basinwide, and even global) and highlight a lake in which some fundamental properties have been influenced in a short period relative to its long flushing time (∼170 years). One legacy of the past 30 years of study seems clear: the notion that Lake Superior, due to its vastness, is resistant to environmental forcing and very slow to change, has been modified. We use two important biological components to evaluate change and also to contrast biological distributions, highlighting that some fundamental aspects of food webs vary with depth. Reflecting on these observations, we offer a perspective on how well we keep track of the condition and functioning of the lake, and how we might improve assessments to more actively inform management. Without more frequent biological sampling across all depth zones of the lake, there will continue to be limited ability to assess the nature and causes of ecological change, even when some changes are detected. Knowing that physico-chemical changes can occur relatively quickly (within decades), that the mechanisms for change can be expressed over different spatial dimensions of the lake, and that biology is distributed heterogeneously over these spatial dimensions, we argue the need to increase the degree (the spatial comprehensiveness, frequency, and integration of components) to which the lake is assessed.

Spatial variation is well known to exist in water quality parameters of the Great Lakes nearshore; however, strong patterns for extended reaches also have been observed and found to be robust across seasonal time frames. Less is known about robustness of inter-annual variation within parameters for water quality in the nearshore. We have conducted high-resolution surveys with towed electronic instrumentation in nearshore areas of Lake Superior and have combined several seasons (2001–2005) of measurements from multiple research efforts to investigate how spatial variation compares across years. The combined survey tows ranged across approximately 1200 km of Lake Superior's south shore. In addition to the survey tracks, we also sampled fixed stations to collect calibration data and other parameters not observed by the in situ electronic sensors. The towed sensor data provided information on the spatial and temporal variability of water quality parameters along the nearshore. We found a consistent spatial pattern over time along the south shore of Lake Superior. Nearshore water quality parameters were analyzed with respect to landscape characteristics of the adjacent watersheds (US only) using multivariate stepwise regressions and found to correlate to landscape characterization. The stressor categories of landscape character that best described the nearshore parameters were agriculture-chemical usage and land-cover attributes. Peak nearshore values corresponded with landscape position that had the most altered landuse character (e.g. Duluth/Superior region). The landscape character appears to drive and maintain the spatial pattern in nearshore water quality parameters.

Biological indicators can be used both to estimate ecological condition and to suggest plausible causes of ecosystem degradation across the U.S. Great Lakes coastal region. Here we use data on breeding bird, diatom, fish, invertebrate, and wetland plant communities to develop robust indicators of ecological condition of the U.S. Lake Superior coastal zone. Sites were selected as part of a larger, stratified random design for the entire U.S. Great Lakes coastal region, covering gradients of anthropogenic stress defined by over 200 stressor variables (e.g. agriculture, altered land cover, human populations, and point source pollution). A total of 89 locations in Lake Superior were sampled between 2001 and 2004 including 31 sites for stable isotope analysis of benthic macroinvertebrates, 62 sites for birds, 35 for diatoms, 32 for fish and macroinvertebrates, and 26 for wetland vegetation. A relationship between watershed disturbance metrics and 15N levels in coastal macroinvertebrates confirmed that watershed-based stressor gradients are expressed across Lake Superior's coastal ecosystems, increasing confidence in ascribing causes of biological responses to some landscape activities. Several landscape metrics in particular—agriculture, urbanization, human population density, and road density—strongly influenced the responses of indicator species assemblages. Conditions were generally good in Lake Superior, but in some areas watershed stressors produced degraded conditions that were similar to those in the southern and eastern U.S. Great Lakes. The following indicators were developed based on biotic responses to stress in Lake Superior in the context of all the Great Lakes: (1) an index of ecological condition for breeding bird communities, (2) diatom-based nutrient and solids indicators, (3) fish and macroinvertebrate indicators for coastal wetlands, and (4) a non-metric multidimensional scaling for wetland plants corresponding to a cumulative stress index. These biotic measures serve as useful indicators of the ecological condition of the Lake Superior coast; collectively, they provide a baseline assessment of selected biological conditions for the U.S. Lake Superior coastal region and prescribe a means to detect change over time.

This Special Issue of Aquatic Ecosystem Health and Management (AEHM) is based on 11 of the papers presented at a three-day International Conference in Duluth, MN held in May 2010, and titled “Ecolo...