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A fully coupled ecosystem model is used to identify the effects of environmental conditions and upwelling variability on growth of juvenile Chinook salmon in central California coastal waters. The ecosystem model framework consists of an ocean circulation submodel, a biogeochemical submodel, and an individual‐based submodel for salmon. Simulation results indicate that years favorable for juvenile salmon growth off central California are characterized by particularly intense early season upwelling (i.e., March through May), leading to enhanced krill concentrations during summer near the location of ocean entry (i.e., Gulf of the Farallones). Seasonally averaged growth rates in the model are generally consistent with observed values and suggest that juvenile salmon emigrating later in the season (i.e., late May and June) achieve higher weight gains during their first 90 days of ocean residency. Fully coupled ecosystem model for California juvenile Chinook salmonFavorable salmon growth conditions determined by early season upwellingLate spring emigration leads to higher weight gains during first period at sea

Sulfur (S) cycling in a chestnut oak forest on Walker Branch Watershed, Tennessee, was dominated by geochemical processes involving sulfate. Even though available SO42-was present far in excess of forest nutritional requirements, the ecosystem as a whole accumulated ~60% of incoming SO4-S. Most (90%) of this accumulation occurred by SO42-adsorption in sesquioxide-rich subsurface soils, with a relatively minor amount accumulating and cycling as SO42-within vegetative components. Organic sulfates are thought to constitute a large proportion of total S in surface soils, also, and to provide a pool of readily mineralized available S within the ecosystem.

A water‐budget model was developed to aid the study of transport of nutrients in surface and subsurface flows across a marsh. The model is based on field studies of Wingra marsh adjacent to Lake Wingra in Madison, Wis., and was used to calculate monthly totals of actual evapotranspiration, surface runoff, and subsurface drainage from April 1970 through August 1976. About 90% of the water entering the marsh comes from urban storm runoff. The remainder is precipitation (8%) and deep ground‐water inflow (2%). Water leaves the marsh through evapotranspiration (7%), shallow ground‐water discharge (8%), and surface outflow (85%). The model was used to estimate the water‐table elevation at an observation well where direct measurements were taken (November 1975 through October 1976). The observed depth to the water table ranged from 0 to 150 cm below the surface and the simulated value usually was within ± 10 cm. This suggests that the model adequately computes the water budget for the marsh and provides a sound basis for calculating dissolved and suspended material loads transported through the marsh into Lake Wingra.