Date of Award


Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)


Ecology and Environmental Sciences


Christopher Cronan

Second Committee Member

Alexander D. Huryn

Third Committee Member

Chet Rock


Physical, chemical, and biological characteristics of streams draining 20 catchments in Maine, U.S.A were compared to determine the influence of increasing urban intensity on stream ecosystem structure. The catchments had varying levels of urban land-use (percentage of the total impervious area within the catchment) ranging from 1-31%. Stream habitat quality, stability, and water quality consistently decreased as the proportion of impervious surface area increased within the catchment. .Indices based on stream benthic macroinvertebrate communities showed even stronger declines as a function of increasing impervious area in the study catchments. Streams draining catchments with levels of impervious surfaces <6% had higher levels of both total and Ephemeroptera + Plecoptera + Trichoptera (EPT) taxonomic richness. With increased levels of urban intensity, benthic macroinvertebrate communities in streams were characterized by decreased numbers of sensitive taxa. Taxa considered to be moderately sensitive to anthropogenic stress (e.g. Acerpenna (Ephemeroptera), Paracapnia and Allocapnia (Plecoptera), Optiosewus and Stenelmis (Coleoptera), Hydropsyche and Cheumatospyche (Trichoptera), Orthocladiinae (Diptera), and Oligochaeta) were apparently little influenced by increasing urban intensity. These patterns were similar between the Fall and Spring. Results indicated that beyond an apparent threshold of ≈6% impervious surface area in the catchment, study streams exhibited an abrupt step-like drop in macroinvertebrate community condition as indicated by a reduction in the presence of sensitive macroinvertebrate taxa. Streams with <6% impervious surfaces contained invertebrate communities with average total richness of 33 taxa (Fall) and 31 taxa (Spring) and average EPT richness of 15 taxa (Fall) and 13 taxa (Spring). In contrast, none of the streams located in catchments with 6-27% impervious coverage exhibited average total richness >18 taxa and average EPT richness >6 taxa. Physical habitat and water quality parameters failed to indicate the mechanism resulting in degradation of the macroinvertebrate community.