Ecological assessment of streams in the Hudson and Delaware River Basins: Linking stream condition to impact source and landscape change

Biological assemblages of streams integrate environmental conditions over space and time, and have been widely used to assess stream condition. Assemblage information can also be valuable in diagnosing sources of degradation. This dissertation links the vast information available in macroinvertebrate and fish assemblages of Hudson and Delaware River Basin streams to environmental conditions at several scales. The goals are to (1) diagnose sources of disturbance, (2) assess stream condition, and (3) determine urbanization-related landscape characteristics that affect stream condition.; New York State uses an Impact Source Determination method (ISD) to identify point and nonpoint sources of impacts to stream water quality on the basis of benthic macroinvertebrates. The ISD was calculated for 26 stream sites in the Hudson River Basin. Canonical correspondence analysis was performed to relate macroinvertebrate assemblage structure to chemical and physical conditions of the sites. ISD classifications for most sites agreed with impairment sources inferred from these results.; Fish assemblage data were used to calculate Index of Biological Integrity (IBI) scores for 27 sites. This IBI for northern mid-Atlantic drainages was evaluated against chemical and physical stream characteristics, macroinvertebrate metrics, and land use. An environmental gradient was established by ordination of chemical and habitat variables. Decreasing IBI scores were related to declining environmental quality, and loss of sensitive macroinvertebrate taxa. The modified IBI appears to be sensitive to environmental degradation of streams in the northern mid-Atlantic slope drainages.; Ordination of stream macroinvertebrate taxa relative abundances was used to establish a disturbance gradient associated with urban intensity for 42 streams in the Delaware River Basin. Regression models explained up to 78 percent of the variation in disturbance score (ordination axis score). Results suggest that the influence of urban-impervious cover in stream catchments can be offset by planning and management practices that retain forested riparian buffers, limit the replacement of tree cover by grass cover in urban areas, and limit forest fragmentation.; Key words. biological integrity, Delaware River basin, fish assemblage, forest fragmentation, Hudson River basin, landscape ecology, macroinvertebrate, source determination, urbanization, water quality...