We describe relationships between pH, specific conductance, calcium, magnesium, chloride, sulfate, nitrogen, and phosphorus and land‐use patterns in the Mullica River basin, a major New Jersey Pinelands watershed, and determine the thresholds at which significant changes in water quality occur. Nonpoint sources are the main contributors of pollutants to surface waters in the basin. Using multiple regression and water‐quality data for 25 stream sites, we determine the percentage of variation in the water‐quality data explained by urban land and upland agriculture and evaluate whether the proximity of these land uses influences water‐quality/land‐use relationships. We use a second, independently collected water‐quality dataset to validate the statistical models. The multiple‐regression results indicate that water‐quality degradation in the study area is associated with basin‐wide upland land uses, which are generally good predictors of water‐quality conditions, and that both urban land and upland agriculture must be included in models to more fully describe the relationship between watershed disturbance and water quality. Including the proximity of land uses did not improve the relationship between land use and water quality. Ten‐percent altered‐land cover in a basin represents the threshold at which a significant deviation from reference‐site water‐quality conditions occurs in the Mullica River basin.

/ We used linear regression to independently and jointly relate specific conductance and pH measured at New Jersey Pinelands stream sites to the percentage of altered land in a watershed. Percentage altered land included developed and agricultural land uses and represented watershed disturbance for a given site. Median values calculated for a 2-year period (September 1992 through August 1994) characterized pH and specific conductance at the study sites. We found the relationships between the median values for both water-quality measures and percentage altered land for a site to be consistent across subregion and dominant altered-land use. Our results also demonstrated that the water-quality/altered-land relationships developed using median values were similar to relationships developed using data from any single-sample period within the entire study period. Individually, pH and specific conductance explained 48% and 56%, respectively, of the variability in watershed disturbance among study sites. The joint use of pH and specific conductance explained 79% of the watershed disturbance variability among sites. The joint use of these easily obtained water-quality measures can provide a quick assessment of instream water-quality impacts from upstream watershed disturbance at any Pinelands stream site. Additionally, a range in pH and specific conductance, and hence a range in ambient water quality, can be predicted for a given altered-land percentage or a change in existing altered-land conditions.

ABSTRACT. Characterizing ecological indicatoJ'll such as water quality is neceuary to effectively manage human-dominated systems such as the New Jersey Pinelands. Pinelands surface wateJ'll are naturally acidic and low in nutrients and other dillOlved substances. Water quality for 14 Pinelands stream lites monitored by the U.8. Geological Survey was characterized in relation to land use. A gradient oC iDc:reasing pH, specific conductance, and concentration oC dissolved calcium, dissolved magnesium, total nitrite + nitrate-nitrogen, total ammonia-nitrogen, and total phosphorus was 8IIOciated with a watenhed disturbance gradient oC increasing land use intensity and waste water flow. These two parallel gradients emphasized the significant effect that watenhed disturbance can have on natural water chemistry in the Pinelands. The results oCthis study can be applied to planning and regulatory programs in the Pine1ands. (KEY TERMS: land use; New Jersey Pinelands; wateJ'llhed disturbance gradient; water quality.)

We compared species composition, relative abundances, and species richness of reference‐site fish assemblages to fish samples collected from Pinelands streams that displayed a range of water quality and watershed land‐use characteristics. We used detrended correspondence analysis (DCA) and principal component analysis (PCA) to relate community gradients to a complex watershed disturbance gradient characterized by increasing pH, specific conductance, and the percentage of developed and agricultural land in a drainage basin. Native species occurred across a range of conditions and dominated all sites. The major difference between reference‐site assemblages and those found in degraded streams was the occurrence of nonnative species at the degraded sites. Species whose occurrence within New Jersey is generally limited to the Pinelands were more frequently found at reference sites compared with disturbed sites, but these differences were not statistically significant. Based on relative abundance, only two native species displayed a clear affinity to either the disturbed or undisturbed end of the watershed gradient. Species richness did not clearly distinguish reference sites from degraded sites. Neither species composition nor species richness was related to stream size. Species composition based on presence/absence provided as good an estimate of Pinelands watershed disturbance as did relative abundance. The study demonstrates that ordination of presence/absence or relative abundance data using DCA provides a good measure of Pinelands watershed conditions. When evaluating assemblages found at both reference sites and degraded sites, our approach can provide at least part of the basis for developing regional metrics to assess the status of species‐poor fish communities or ranking biological samples based on inherent community attributes.

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