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Our goal in the development of a nearshore monitoring method has been to evaluate and refine an in situ mapping approach to assess the nearshore waters across the Great Lakes. The report here for Lake Huron is part of a broader effort being conducted across all five Great Lakes. We conducted an intensive survey for the United States nearshore of Lake Huron along a continuous shoreline transect (523 km) from Port Huron, Michigan, to Detour Passage. A depth contour of 20 m was towed with a conductivity-temperature depth profiler, fluorometer, transmissometer, and laser optical plankton counter. Multiple cross-contour tows (10-30 m) on the cruise dates were used to characterize the variability across a broader range of the nearshore. The cross-contour tows were comparable with the alongshore contour indicating that the 20-m contour does a good job of representing the nearshore region (10-30 m). Strong correlations were observed between water quality and spatially associated watershed land use. A repeat tow separated by several weeks investigated temporal variability in spatial patterns within a summer season. Strong correlations were observed across each variable for the temporal repeat across broad- and fine-scale spatial dimensions. The survey results for Lake Huron nearshore are briefly compared with a similar nearshore survey in Lake Superior. The biomass concentrations of lower food web components of Lake Huron were notably approximately 54-59 % of those in Lake Superior. The towed instrumentation survey supported the recent view of a change in Lake Huron to an ultra-oligotrophic state, which has been uncharacteristic in recent history.

An optical plankton counter (OPC) potentially provides an assessment tool for zooplankton condition in ecosystems that is rapid, economical, and spatially extensive. We collected zooplankton data with an OPC in 20 near-shore regions of 4 of the Laurentian Great Lakes. The zooplankton size information was used to compute mean size, biomass density, and size-spectra parameters for each location. The resulting metrics were analyzed for their ability to discriminate among the Great Lakes. Biomass density provided discrimination among lakes, as did several parameters describing spectra shape and distribution. A proposed zooplankton indicator, mean size (determined with OPC measurements in this study), was found to provide discrimination among lakes. Size-spectra-related parameters added increased ability to discriminate in conjunction with the biomass density (or mean size) metric. A discriminant function analysis of the multiple metrics (mean size, biomass density, and distribution parameters) suggests that a multi metric size-based approach might be used to classify communities among lakes improving a mean-size metric. The feasibility OPCs and size-based metrics for zooplankton assessment was found to have potential for further development as assessment tools for the biological condition of zooplankton communities in the Great Lakes.

Over 400 sites were sampled in the nearshore of the U.S. Great Lakes during the U.S. National Coastal Condition Assessment (NCCA) field survey in summer 2010. Underwater video images were recorded in addition to routine NCCA benthic assessment measures. This paper has two objectives: (1) to develop a process to evaluate video performance with acceptance criteria, exploring reasons for poor images, and (2) to use acceptable videos in an example application with invasive mussels, evaluating the enhancement potential of video to supplement traditional grab sampling. A standard hierarchical protocol was developed to rank video performance based on quality and clarity. We determined controllable and uncontrollable factors affecting video performance. Moreover, specific thresholds limiting video were identified: >0.5/m for light extinction and >3.5 µg/L for chlorophyll a concentration. To demonstrate the utility and enhancement potential of video sampling, observed dreissenid presence from excellent (221 of 362 videos) videos was compared with NCCA benthic taxonomy, in the context of the statistically based NCCA survey. Including video increased the overall area estimate of the U.S. Great Lakes nearshore with invasive mussels by about 15 % compared to PONAR alone; 44 % (7570 km2) of the surveyed region had mussels. The proportion of the nearshore area having mussels varied from low (3.5 %) in Lake Superior to >50 % in the lower lakes. PONAR and video have unique strengths and weaknesses as sampling tools in the Great Lakes nearshore environment, but when paired were complimentary and thus provided a more thorough benthic condition assessment at lake and regional scales.

This article summarizes the views of aquatic scientists who gathered to assess the ability of stream ecosystem theory to predict recovery from disturbance. Two views of disturbance were evident: a discrete removal of organisms vs an unusual deviation from normal. These were perceived as applying to different scales and/or objectives. Long-term information is required from both points of view to define recovery. Recovery also may be defined in different ways, but it is clear that recovery has both spatial and temporal components, and includes both physical and biological processes. Consensus was very strong that a major role (and challenge) for theory lies in the understanding of spatial aspects, temporal scales, coupling of physics and biology, and the interaction of these features in recovery processes. Some progress is evident in the articles of this volume, but among the topics identified as critical for further theoretical contributions were: homogeneous vs heterogeneous distribution of disturbance, local extent of disturbance relative to a regional context, critical vs noncritical patches (size and location) of disturbance at different spatial scales and temporal frequencies, delineation of reversible and nonreversible processes, and physical and biological constraints on the time frame for recovery. Such concepts need attention across different types of lotic ecosystems. Thus, there was strong consensus that a national monitoring system of representative lotic ecosystems within ecological regions be established. The purpose of this monitoring system would be to acquire long-term data on natural variability, to establish viable indicators of spatial and temporal aspects of recovery, and to develop and test emerging theoretical developments.

Assessment of ecological changes relative to disturbance, either natural or human-induced, confronts a fundamental problem. Ecosystems are complex, variable, and diverse in nature; consequently, the need for simplification to essential features that would characterize ecosystems adequately is generally acknowledged. Yet there is no firm prescription for what to measure in order to describe the response and recovery of ecosystems to stress. Initial focus is provided by identifying relevant ecological endpoints, i.e., ecological changes of particular relevance to humans. Furthermore, we suggest generic purposes and criteria to be considered in making choices of ecological indicators that relate to those endpoints. Suites of indicators, with variety of purposes, are required to assess response and recovery of most ecosystems and most stresses. We suggest that measures of certain ecosystem processes may provide special insight on the early stages of recovery; the use of functional indicators as complimentary to other biotic indicators is highlighted in an extended example for lotic ecosystems.

A better understanding of relationships between human activities and water chemistry is needed to identify and manage sources of anthropogenic stress in Great Lakes coastal wetlands. The objective of the study described in this article was to characterize relationships between water chemistry and multiple classes of human activity (agriculture, population and development, point source pollution, and atmospheric deposition). We also evaluated the influence of geomorphology and biogeo- graphic factors on stressor-water quality relationships. We collected water chemistry data from 98 coastal wetlands distributed along the United States shoreline of the Lau- rentian Great Lakes and GIS-based stressor data from the associated drainage basin to examine stressor-water quality relationships. The sampling captured broad ranges (1.5-2 orders of magnitude) in total phosphorus (TP), total nitro- gen (TN), dissolved inorganic nitrogen (DIN), total suspended solids (TSS), chlorophyll a (Chl a), and chlo- ride; concentrations were strongly correlated with stressor metrics. Hierarchical partitioning and all-subsets regression analyses were used to evaluate the independent influence of different stressor classes on water quality and to identify best predictive models. Results showed that all categories of stress influenced water quality and that the relative influence of different classes of disturbance varied among water quality parameters. Chloride exhibited the strongest relationships with stressors followed in order by TN, Chl a, TP, TSS, and DIN. In general, coarse scale classification of wetlands by morphology (three wetland classes: riverine, protected, open coastal) and biogeography (two ecopro- vinces: Eastern Broadleaf Forest (EBF) and Laurentian Mixed Forest (LMF)) did not improve predictive models. This study provides strong evidence of the link between water chemistry and human stress in Great Lakes coastal wetlands and can be used to inform management efforts to improve water quality in Great Lakes coastal ecosystems.

Integrated, quantitative expressions of anthropogenic stress over large geographic regions can be valuable tools in environmental research and management. Despite the fundamental appeal of a regional approach, development of regional stress measures remains one of the most important current challenges in environmental science. Using publicly available, pre-existing spatial datasets, we developed a geographic information system database of 86 variables related to five classes of anthropogenic stress in the U.S. Great Lakes basin: agriculture, atmospheric deposition, human population, land cover, and point source pollution. The original variables were quantified by a variety of data types over a broad range of spatial and classification resolutions. We summarized the original data for 762 watershed-based units that comprise the U.S. portion of the basin and then used principal components analysis to develop overall stress measures within each stress category. We developed a cumulative stress index by combining the first principal component from each of the five stress categories. Maps of the stress measures illustrate strong spatial patterns across the basin, with the greatest amount of stress occurring on the western shore of Lake Michigan, southwest Lake Erie, and southeastern Lake Ontario. We found strong relationships between the stress measures and characteristics of bird communities, fish communities, and water chemistry measurements from the coastal region. The stress measures are taken to represent the major threats to coastal ecosystems in the U.S. Great Lakes. Such regional-scale efforts are critical for understanding relationships between human disturbance and ecosystem response, and can be used to guide environmental decision-making at both regional and local scales.

Potential effects of oil drilling fluid discharges uponThalassia seagrass ecosystems were examined using seagrass core microcosms. Observed experimental effects, summarized in this article, included changes in both autotrophic (Thalassia and epiphyte) and heterotrophic (dominant benthic macroinvertebrates) species, and the processes of primary productivity and decomposition. The physical disturbance related to greater turbidity and sedimentation caused some effects, while others seemed a direct response to the toxic constituents of drilling fluids. Using these experimental results and the case ofThalassia and drilling fluids as a case study, we explore general methodological and philosophical issues for ecotoxicology and, furthermore, focus upon the challenge of providing a scientific basis for judging acceptability of environmental changes likely to ensue from human activities.