A Basin-Wide Survey of Coastal Wetlands of the Laurentian Great Lakes: Development and Comparison of Water Quality Indices

Anna M. Harrison,Carl R. Ruetz,Jan J. H. Ciborowski,Matthew J. Cooper,Alexander J. Reisinger,Valerie J. Brady,Donald G. Uzarski,Katherine E. O’Reilly,Douglas A. Wilcox

doi:10.1007/s13157-019-01198-z

Abstract

Coastal wetlands of the Laurentian Great Lakes are vital habitats for biota of ecological and economic importance. These habitats are susceptible to water quality impairments driven by runoff from the landscape due to their location along the shoreline. Monitoring of the overall status of biotic and abiotic conditions of coastal wetlands within the Great Lakes has been ongoing for over a decade. Here, we utilize measurements of aquatic physicochemical and land cover variables from 877 vegetation zones in 511 coastal wetland sites spanning the US and Canadian shorelines of the entire Great Lakes basin. Our objective is to develop water quality indices based on physicochemical measures (Chem-Rank), land use/land cover (LULC-Rank), and their combined effects (Sum-Rank and Simplified Sum-Rank), for both vegetation zones and wetland sites. We found that water quality differed among wetland vegetation types and among Great Lakes regions, corroborating previous findings that human land use alters coastal wetland water quality. Future monitoring can use these straightforward, easy-to-calculate indices to assess the abiotic condition of aquatic habitats. Our data support the need for management efforts focused on reducing nutrient and pollution loads that stem from human activities, particularly in the developed southern portions of the Great Lakes basin.

Highlights

In recent decades, aquatic resource managers have increasingly used biological indicators to assess ecosystem health, in place of chemical and physical sampling of habitats, inferring that biota integrate conditions over time, whereas chemical and physical samples represent only a snapshot of the ecosystem
We previously proposed an index of anthropogenic disturbance combining physicochemical and landscape stressors (Uzarski et al 2005), but this previous index was limited in its spatial scale
Bulrush occur throughout the Great Lakes basin; this trend likely reflects lower anthropogenic disturbance in the northern regions compared with southern regions

Summary

Introduction

Aquatic resource managers have increasingly used biological indicators to assess ecosystem health, in place of chemical and physical sampling of habitats, inferring that biota integrate conditions over time, whereas chemical and physical samples represent only a snapshot of the ecosystem. Biological indices are developed based on the underlying assumption that the suite of anthropogenic impacts on an ecosystem can be best represented by the biological community capable of persisting within that ecosystem (Karr 1981). Wetlands (2020) 40:465–477 anthropogenic impacts and be of higher quality This index of biotic integrity (IBI) approach is wellestablished, it remains difficult to differentiate the relative influence of anthropogenic disturbances in biological communities from effects of natural disturbances (Suter 2001), some watershed modeling approaches have assessed these relationships (Wiley et al 2003). In coastal wetlands of the Laurentian Great Lakes (hereafter, Great Lakes), for example, anthropogenic disturbances can mask or interact with the effects of natural disturbances, such as wave exposure (Burton et al 2004) or water-level fluctuations (Wilcox et al 2002), on community structure

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