Oceanic sources of nutrients to the kelp forests of the Santa Barbara Channel were diagnosed using time series from three moorings in 12-to 17-m water depth. An in situ nitrate autoanalyzer on the moorings provided the first high-resolution time series of nitrate + nitrite (dissolved inorganic nitrogen, DIN) concentrations for this environment. Measurements between February 2001 and May 2003 show that the major mechanisms that supply DIN to the inner shelf of the Santa Barbara Channel are upwelling, diurnal internal motions, and storm runoff. These supply mechanisms vary in importance seasonally. Upwelling dominates increases of inner-shelf DIN concentration between March and May and accounts for more than half of the annual advective DIN transport to shelf reefs. In summer, baroclinic motions akin to internal waves are an important source of DIN because they occur when surface nutrient concentrations are depleted and other supply mechanisms are inactive. Brief episodes of upwelling become important in late autumn and early winter. DIN inputs from storm runoff, detected as salinity dilution at the moorings and estimated from measurements of stream discharge and nutrient concentration, are significant during winter runoff events.

Land use, watershed processes, and coastal biodiversity are often intricately linked, yet land–sea interactions are usually ignored when selecting terrestrial and marine reserves with existing models. Such oversight increases the risk that reserves will fail to achieve their conservation objectives. The conceptual model underlying existing reserve selection models presumes each site is a closed ecological system, unaffected by inputs from elsewhere. As a short‐term objective, we recommend extending land‐conservation analyses to account for effects on marine biodiversity by considering linkages between ecosystems. This level of integration seems feasible and directly relevant to agencies and conservancies engaged in protecting coastal lands. We propose an approach that evaluates terrestrial sites based on whether they benefit or harm marine species or habitats. We then consider a hypothetical example involving estuarine nurseries. Whether this approach will produce more effective terrestrial reserves remains to be seen.

In this study we describe the interannual variability of N loading to and yield from high-elevation watersheds of the Sierra Nevada of California using a 14 year continuous record from the Emerald Lake watershed (ELW) (1985-1998) and 1445

Abstract:Two-component hydrograph separations were performed for three, nested, snowmelt-dominated catchments in Sequoia National Park. The purpose of the hydrograph separations was to: (i) differentiate between the old and new water contributions to discharge during snowmelt using υ 18 O signatures; (ii) identify the fraction of snowmelt that travelled through the subsurface (reactive) compartment during the snowmelt period using silica or sodium; and (iii) investigate the impact of changing end-member signatures on the separations. 'Old' water refers to water that was stored in the watershed during the previous year, whereas 'new' water is current snowmelt. Hydrograph separations were performed for both a high-accumulation (1998, annual precipitation 2Ð4 m) and an average year (1999, 1Ð3 m). The proportion of old water contribution to discharge during the rising limb of the hydrograph was 10-20%, with 80-100% of snowmelt being reactive, i.e. passing through soil and talus. Estimates of old and new soil water and direct snowmelt entering the stream varied among the catchments in 1999. Differences between these components were minimal in 1998, regardless of varying topography and differing proportions of soil, rock and talus. Using time-dependent rather than constant υ 18 O meltwater and silica soil-water signatures made a meaningful impact on both new and old water, and reactive and unreactive, estimates.

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