Date of Award
Coastal ecosystems of the Laurentian Great Lakes provide many of the services upon which society most depends and yet they are the most highly threatened by anthropogenic stress. Several means of quantifying anthropogenic stress in the Great Lakes have been developed, and measures of expected impact exist for watersheds across the entire basin. However, it is still unknown whether the biological communities present at coastal margins reflect the environmental condition expected from the level of stress in each watershed. Using data previously collected for the Great Lakes Environmental Indicators collaboration, the goal of this thesis was to assess both independent and combined effects of land-use stress on macroinvertebrate community condition. Macroinvertebrate community condition was measured by using multivariate analysis to derive a composite Zoobenthic Assemblage Condition Index (ZACI), which employs the Reference-Degraded Continuum approach. The variation in ZACI scores was then related to two classes of human land use- agriculture and urban development via surrogate environmental gradients. The combined effect of land-use was evaluated by three different methods in a proof of concept. These methods included 1) comparing predicted single-stress ZACI scores to combined stress ZACI scores, 2) response-surface modelling using non-parametric multiplicative regression, and 3) mapping of isopleths distinguishing reference from non-reference conditions. A cluster analysis of biota at site subjects to minimal stress identified 5 distinct invertebrate assemblages which could be classified by environmental attributes (3 in the north, 2 in the south). ZACI condition scores showed distinct but varying trends among groups as a function of land-use stress. Levels of agricultural land-use were found to continuously constrain biological condition in one group, while condition of other groups exhibited potential threshold changes with increasing development-associated stress. In combination, both agriculture and development stress were observed to have significant negative effects on macroinvertebrate assemblages at Great Lakes coastal margins, and development stress is the more severe stressor.
St. Pierre, Jasmine Isabel, "Independent and combined effects of land-use stress on macroinvertebrate community condition at Great Lakes coastal margins" (2016). Electronic Theses and Dissertations. 5867.