Richard A. Park

A generalized model for simulating lake ecosystems

CLEAN, a generalized lake-ecosystem model with strong ecological realism, has been developed in response to one aspect of the growing need for models suitable for helping man to manage his environment. The model currently consists of twenty-eight ordinary differ ential equations which represent approximately six teen compartments, including attached aquatic plants, phytoplankton, zooplankton, bottom-dwelling aquatic insects, fish, suspended organic matter, decomposers, sediments, and nutrients. These equations can be linked in any meaningful combination to simulate a given point in a lake (a separate model for lake cir culation is available to represent spatial variations and to couple simulations of different regions of the lake). Subprogram functions exist for each principal physiological and ecological process, and a submodel for lake water balance is presently being implemented. The program is written in FORTRAN for UNIVAC and IBM time-sharing systems. The model has provided intuitionally realistic simu lations and has given us insight into the effects of nutrient enrichment on the functioning of the lake ecosystem as a whole. Sensitivity analysis has in dicated priorities for further studies to obtain more precise estimates of parameters. Also, evalua tion of the logic and organization of the model by experimenting with it are providing information to use in planning new experimental approaches. CLEAN is presently being tested using data from Lake George, New York, and Lake Wingra. Wisconsin.

Documentation of selected constructs and parameter values in the aquatic model cleaner

Abstract Process representations critical to the phytoplankton and zooplankton submodels are described. These include constructs for: light- and nutrient-limitations and their interaction, temperature, consumption, and population-age structure. Values for key parameters are documented with reference to the literature on aquatic ecology and ecological modelling. Time-course relationships of the processes affecting the phytoplankton, zooplankton, phosphorus and nitrogen compartments are presented and discussed. These serve as additional documentation and are an important result of modelling synthesis.

A multivariate analytical strategy for classifying paleoenvironments

A multivariate analytical strategy is proposed for aiding the investigator in extracting maximum information from environmental data. Data are carefully coded and scaled and are tested for redundancy using R-mode cluster analysis. The samples are partitioned into environmental classes using Q-mode cluster analysis. Q-mode ordination facilitates interpretations, which usually can be verified by comparison with field relationships. Discriminant analysis serves as an identification procedure for extending the classification to unknown samples. The strategy is demonstrated by application to Cape Hatteras microorganism distributions and Devonian sedimentary facies.

Documentation of CLEANX : a generalized model for simulating the open-water ecosystems of lakes

This paper outlines the software for an open-water version of CLEAN, an ecosystem model for lakes. The modular program structure is described, examples of driving variables are given, and the output (including values of several parameters) is shown. The program, with extensive annotations to facilitate adaptation by potential users, is available from author Richard A. Park or from SCS.

Comparison of Chemical Bioaccumulation Models to Assist in Model Selection for Ecological Assessments and TMDL Development

This paper describes a recent EPA-sponsored study (Imhoff et al., 2004) that analyzed and compared the capabilities of advanced chemical bioaccumulation models that are currently available to support the evaluation of ecological effects in aquatic ecosystems. These models are commonly used to establish the linkage of a variety of water quality targets and sources, and to provide a means for comparing various watershed and waterbody management strategies. EPAs Office of Research and Development (ORD), National Environmental Research Laboratory (NERL), Ecosystem Research Division (ERD), is currently supporting EPAs Office of Emergency Response and Remediation (OERR) by addressing priority research needs related to assessing the fate and transport of pollutants via contaminated sediment and bioaccumulation. The results of the first support effort by ERD, an evaluation of currently available numerical models useful for assessing fate and transport of contaminated sediments (Imhoff et al., 2003), were presented at the fall 2003 WEF TMDL Conference (Imhoff, 2003). The work effort presented in this paper constitutes the second element of the support effort by ERD, a parallel evaluation of currently available numerical models useful for assessing chemical bioaccumulation. Eight models were identified that were judged superior to all others in their promise as tools for chemical bioaccumulation analysis. To provide ERD with a basis on

THE ROLE OF MICROCOMPUTERS IN ENVIRONMENTAL MANAGEMENT

ABSTRACT The development of inexpensive microcomputers with color graphics and ample memory has led to a new stage in the rapidly evolving field of environmental modeling. It is now possible to apply models of intermediate complexity in situations where access to large computers is difficult or impossible. In particular, there is excellent potential for the application of ecosystem models to aid environmental management in developing countries. The portability of microcomputers makes it quite easy to use models in the decision-making process at remote sites; questions concerning reservoir management, control of aquatic weeds in waterways, and sampling requirements at field stations can be answered on a day-by-day basis. The MICRO. CLEANER and MICRO. PEST packages, which are implemented on an APPLER microcomputer, will be used to demonstrate the utility of this approach in dealing with problems of water quality and toxic substances.