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The State of Florida (1994) has adopted a plan for addressing Everglades eutrophication problems by reducing anthropogenic phosphorus loads. The plan involves implementation of Best Management Practices in agricultural watersheds and construction of regional treatment marshes (Stormwater Treatment Areas or STA's). This paper describes the development, testing, and application of a mass‐balance model for sizing STA's to achieve treatment objectives. The model is calibrated and tested against peat and water‐column data collected in Water Conservation Area‐2A (WCA‐2A), where phosphorus dynamics and eutrophication impacts have been intensively studied. The 26‐year‐average rate of phosphorus accretion in peat is shown to be proportional to average water‐column phosphorus concentration, with a proportionality constant of 10.2 m/yr (90 percent Confidence Interval = 8.9 to 11.6 m/yr). Spatial and temporal variations in marsh water‐column data suggest that drought‐induced recycling of phosphorus was important during periods of low stage in WCA‐2A. Maintaining wet conditions will be important to promote phosphorus removal in STA's. Sensitivity analysis of STA performance is conducted over the range of uncertainty in model parameter estimates to assess the adequacy of the model as a basis for STA design.

The feasibility of lake water quality management planning has been greatly increased over the past 10 years with the development of relatively simple, empirical methods for assessing eutrophication problems. These relate phosphorus loading, hydrology, and morphometry to such traditional trophic state indices as phosphorus concentration, chlorophyll‐a concentration, and transparency. One of the difficulties associated with use of these methods is that water quality criteria, as related to beneficial use, do not generally correspond to subjective definitions of ‘trophic state.’ This paper attempts to improve upon existing methods by relating measures of phosphorus, chlorophyll‐a, and/or transparency to hypolimnetic dissolved oxygen, which is of direct relevance to existing water quality standards, particularly for fisheries management. A modified version of Carlson's (1977) trophic state index summarizes relationships among summer, epilimnetic measurements of total phosphorus, chlorophyll‐a, and transparency. On the basis of data from 30 lakes this index is shown to be highly correlated with areal hypolimnetic oxygen depletion rate when the apparent effects of mean depth are also taken into account (R2 = 0.91). Tests of the empirical model on a separate data base of 86 lakes indicate that the approach can be used to predict oxygen status based upon lake morphometry and trophic index. The methodology provides a link between phosphorus mass balance models and existing water quality criteria for dissolved oxygen.

An immunohistochemical assay for proliferating cell nuclear antigen (PCNA) identifies cells in all active phases of the cell cycle. In this study, PCNA methodology, which was developed primarily for mammalian tissues, was adapted to three small fish species, medaka (Oryzias latipes), guppy (Poecilia reticulata), and western mosquitofish (Gambusia affinis) that are used in carcinogenesis bioassays and environmental sentinel studies. Our study showed that PCNA can be identified in routinely processed, paraffin embedded specimens of these fishes. Optimum staining conditions were dependent on fixative, primary antibody, antigen retrieval processing, and protein blocking reagent. Best results were achieved using 10% neutral buffered formalin as the fixative, clone PC10 as the primary antibody, and a combination of powdered milk and bovine serum albumin as a protein block. Except for medaka specimens, antigen retrieval was not required for specimens preserved in 10% neutral buffered formalin, but was required for the other fixatives tested. In whole fish specimens, PCNA marked cells in normally proliferating tissues such as testis, ovary, primary filament epithelium of the gill, hematopoietic tissues, thymus, retina and alimentary tract. The study demonstrated the successful application of mammalian-based PCNA technology to these aquatic species. Further applications of the assay will aid in understanding the role of cell proliferation in normal, diseased, and toxicant-affected tissues of aquatic animals.