Simple and reliable procedures have been developed for analyses of NO3−, total N, and organic N in freshwaters. NO3− is determined by second‐derivative UV spectroscopy. Total N and organic N are determined based on second‐derivative analyses of NO3− following persulfate digestion. Resolution of organic N determinations was increased by using ion‐exchange resins to remove NO3− from samples with high concentrations of NO3− prior to persulfate oxidation of the organic N.

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An investigation was made of factors controlling algal succession in a small, oligotrophic lake during summer stratification. Phytoplankton population densities, growth rates, sedimentation losses, and mortality due to zooplankton grazing were measured weekly. Cyclotella michiganiana was the dominant alga through the end of June, at which time Cyclotella comensis began to increase, becoming the dominant by August. In August, high grazing pressure caused the rapid declines of both C. michiganiana and C. comensis, which were followed by an increase of Sphaerocystis schroeteri. The combined effect of greater growth rates and lower loss rates of C. comensis resulted in its dominance over C. michiganiana. In contrast, the C. comensis—S. schroeteri succession clearly resulted from differential mortality alone. It is likely that losses due to sedimentation and/or grazing are important in many lakes and that interspecific competition may be less important in actually controlling seasonal succession.

Agricultural applications of fertilizers and pesticides have increased dramatically since the middle 1960s, and agrochemical contamination of surface and groundwater has become a serious environmental concern. Since the mid-1980s, a variety of state and federal programs have been used to promote wetland restoration, and these continuing efforts provide a unique opportunity for water quality improvement in agricultural watersheds. However, wetland restorations have been motivated primarily by concern over waterfowl habitat loss, and model simulations suggest that commonly used site selection criteria for wetland restorations may be inadequate for water quality purposes. This does not lessen the promise of wetlands for water quality improvement in agricultural watersheds, but rather emphasizes the need for watershed scale approaches to wetland siting and design. Water quality is best viewed from a watershed perspective, and watershed scale endpoints should be explicitly considered in site selection for wetland restoration.

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