Background
Objectives
Significance
Anticipated Benefits
Beneficiaries
Methods
Deliverables
Schedule

Background

A major drawback of current pond aquaculture models is that they neglect the sediment-water interface (Colman & Jacobson, 1991). This is largely because the underlying processes have not been adequately studied in ponds, although the sediment-water interface appears to influence the flux of nitrogen, organic matter, oxygen, and phosphorus in such systems (Schroeder & Berner-Samsonov, 1986; Boyd, 1994). Although pond models have not included sediment-water interactions, process descriptions are available from models developed for shallow (1-3m), eutrophic lakes (e.g., Kamp-Nielsen, 1975; Jorgensen et al., 1982; Blom et al., 1992; Smits & van der Molen, 1993), which can be suitably adapted for pond models.

Objectives

1) To develop a conceptual model for sediment-water column interactions in ponds,

2) To implement differential equations for phosphorus flux between pond sediments and the water column,

3) To test and validate the model,

4) To link phosphorus, organic matter and nitrogen cycling models (developed by the UC Davis group) with existing POND^© models, and

5) To predict seasonal sediment and water quality nutrient profiles in ponds.

Significance

The development of models to describe the flux of phosphorus between pond sediments and the overlying water, combined with the work proposed by the UC Davis group on organic matter and nitrogen cycling, will represent an important step towards understanding nutrient cycles in ponds, and the fate of fertilizers and supplementary feed added to them. Such models will also have use in predicting pond effluent quality and thus will aid in the assessment of the environmental impacts of aquaculture.

Anticipated Benefits

Pond sediment-water column models can be used to better understand and predict the effects of management practices on pond water quality. They can also be used to develop or improve guidelines for the discharge of effluents from pond facilities.

Beneficiaries

Aquaculture managers, extension agents, planners, educators and researchers.

Methods

Process descriptions of sediment-water column interactions of phosphorus in lakes will be examined for use in pond models particularlywith regard to their functionality, adaptability to pond conditions, complexity, data and computational requirements. Differential equations that describe phosphorus flux will be implemented in POND^©, and initial estimates of the required parameters for different processes such as adsorption, mineralization, diffusion and bioturbation obtained from past or concurrent CRSP field research if possible, or adapted from lake models. The preliminary version of the model will be validated against data from past and concurrent CRSP experiments. The model will be integrated with descriptions for organic matter and nitrogen flux developed by the UC Davis group into an overall sediment-water column exchange model for ponds within the POND^© framework. Simulation results will be used to develop guidelines for effluent discharge from pond facilities.

Deliverables

A pond sediment-water column model implemented in the POND^© framework.

Schedule

8/1/96 to 10/1/97 (see also Table 1).

Report Submittal: 10/1/97