Ecologists frequently use stable isotopes to measure the pattern and process of interested ecosystems. Comparisons offood web structure among and within ecosystems rely on a baseline isotopic signature for each system.'The goal of a trophic baselineis to reflect the isotopic signature of the primary source of materials and nutrients for the Food web. In general isotope baseline se-lection depends on the specific research question and must be tailored to a particular study system. We reviewed the use of the sta-ble nitrogen isotopic signatures of primary producers and primary consumers to develop the baseline in aquatic ecology. Each ofthese studies used x slightly different method of baseline correction that was tailored to address a question of speci$c ecological in-terest. However, choosing an appropriate Laseline depends on the inter and intraspecific spatial, temporal variability of isotopicbaselines and on the spatial and temporal context of the ecological question under consideration. We also evaluated to what extentisotopic heterogeneity actually influence consumer' s trophic positions ai the temporal and intraspecifical scales. The result of troph-ic; position output estimated using an isotopic mixing model was generally variable, provided that baseline variability for trophic po-sition estimation were sufficiently distinct in dietary mixing models.